Patent Publication Number: US-7717765-B2

Title: Method of sealing a flat-type fluorescent lamp device and process for coating fluorescent layers on corresponding first and second substrates

Description:
This application is a Divisional of U.S. patent application Ser. No. 10/747,270 filed on Dec. 30, 2003 now U.S. Pat. No. 7,279,829 and claims the benefit of Korean Patent Application No. P2002-87874 filed in Korea on Dec. 31, 2002, both of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fluorescent lamp device, and more particularly, to a flat-type fluorescent lamp device and a method of fabricating a flat-type fluorescent lamp device. 
     2. Background of the Related Art 
     Currently, cathode ray tubes (CRTs) are commonly used in televisions, as monitors in scientific instruments, and information terminals. However, the CRTs have size and weight limitations that are in direct opposition to the trend of electronic products becoming smaller and lighter. Different types of flat display devices that are expected to replace the CRTs include liquid crystal display (LCD) devices that make use of electro-optical effects, plasma display panel (PDP) device that make use of gas-discharge, and electro-luminescent display (ELD) device that make use of electroluminescent materials. 
     Among these flat display devices, the LCD devices have been commonly selected to replace the CRTs because of their small size, light weight, and low power consumption. Since most of the LCD devices are light receptive devices, wherein a quantity of light receivable from an exterior source is controlled to display image data, i.e., pictures, a separate light source for illuminating an LCD panel is necessary. Generally, a backlight unit is used as the light source of the LCD device and includes cylindrical fluorescent lamps. The backlight unit may be divided into different functional categories including bottom-type and edge-type backlight units. 
     The bottom-type backlight unit includes a plurality of lamps arranged along a first direction beneath a spreading plate for directing light toward a front surface of the LCD panel. The bottom-type backlight unit has a high light utilization efficiency as compared to the edge-type backlight unit, and is commonly used in large sized LCD panels requiring high luminance. However, incorporation of the bottom-type backlight in a thin LCD panel is limited because a gap is required between the lamps and the LCD panel in order to prevent the lamps from being visible on the LCD panel. 
     The edge-type backlight unit includes a fluorescent lamp at a side of a light plate for spreading the light to an entire surface of the LCD panel through the light plate. The edge-type backlight unit is commonly used in comparatively small sized LCD devices, such as monitors for laptop and desktop computers. However, incorporation of the edge-type backlight unit results in low luminance since the fluorescent lamp is provided at the side of the light plate. Accordingly, the edge-type backlight unit requires high optical design and processing technologies of the light plate for obtaining a uniform distribution of light intensity across an entire surface of the LCD panel. 
       FIG. 1  is a cross sectional view of an edge-type backlight unit according to the related art. In  FIG. 1 , a backlight unit is mounted on an under side of an LCD panel that displays image data and includes a lower cover  3  for protecting a base l, a lamp assembly  10  for holding a lamp to be used as a light source, a light plate  5  for uniform supply of a light from the source to the LCD panel, an upper spreading plate  9  and a lower spreading plate  6  over the light plate  5  for spreading the light from the light plate  5 , and an upper prism  8  and a lower prism  7  between the upper spreading plate  9  and the lower spreading plate  6  for converging and directing the light toward the LCD panel. 
       FIG. 2  is a perspective view of an edge-type backlight unit according to the related art. In  FIG. 2 , an edge-type backlight unit includes a lamp having a high voltage side lamp wire  13   a  and a low voltage side lamp wire  13   b  connected to a connector  16  in a high voltage side lamp holder  12   a  and a low voltage side lamp holder  12   b , respectively. In addition, the lamp wires  13   a  and  13   b  are soldered to a high voltage side and a lower voltage side of the lamp, respectively, and lamp holders  12   a  and  12   b  are attached to cover the soldered part of the lamp. The lamp is placed in a lamp housing  15 . 
     Next, the lamp assembly is mounted onto a base  1 , and a lower cover  3  is attached to a part of the base  1  around a light reception part of a light plate  5 . This protects the lamp assembly from external impact. After a reflective plate  4  is placed on an inside bottom of the base  1 , the light plate  5  is inserted in an inside of an inner cap part of the lamp housing  15  without deforming the inside cap of the lamp housing  15 . A lower spreading plate  6 , a lower prism  7 , an upper prism  8 , and an upper spreading plate  9  are sequentially placed on the light plate  5 . 
     When power is provided to the backlight unit through the connector  16  connected to a power source, light is emitted from the lamp as a glow discharge. Accordingly, the emitted light is incident on a light reception surface of the light plate  5 , and is reflected and scattered by dots printed on a bottom of the light plate  5 . The light is scattered along an oblique direction as it passes through the spreading plate  6 , which is arranged along a vertical direction as the light passes through the upper and lower prisms  8  and  7 . The light is scattered again along an oblique angle as the it passes through the spreading plate  9 . Eventually, a portion of the light passed through the spreading plate  6  illuminates the LCD panel from a back surface. Thus, when the reflective plate  4  reflects the light, the light escapes to a back surface without being reflected and scattered by the printed dots on the light plate  5 , and is transmitted upward again. 
     However, the backlight unit has the following disadvantages. First, since the light progresses along a lateral direction from the fluorescent lamp, the backlight unit cannot provide adequate amounts of light. Accordingly, uniform luminance cannot be provided along an entire surface of the LCD panel. Second, it is very difficult to control a surface state of the light plate and a direction of the light progression by using the light plate having the fixed pattern of printed dots. Third, the fabrication process is complicated, thereby resulting in poor device yield. For example, many defects may be generated during the fabrication process, including deformed light plates or light plates having inaccurate dimensions. Specifically, since there are different thermal expansion coefficients between the different sheets and structures, wrinkles are generated. In addition, large dimensional variations of the light plate are caused by high absorption of moisture when the LCD panel and backlight unit are exposed to high humidity. Fourth, measures to prevent contamination by foreign matter and to prevent scratches on the light plate and sheets increase production costs. 
       FIG. 3  is a cross sectional view of a flat-type fluorescent lamp device according to the related art, and  FIG. 4  is a cross sectional view and a plan view of dark spots on the flat-type fluorescent lamp device in  FIG. 3  according to the related art. In  FIGS. 3 and 4 , a flat-type fluorescent lamp device includes a plurality of first and second electrodes  31  and  32  arranged on a first substrate  30  at fixed intervals, a barrier layer  33  covering an entire surface of each of the first and second electrodes  31  and  32 , a first fluorescent layer  34  on an entire surface of the first substrate  30  including the first and second electrodes  31  and  32  and the barrier layer  33 , a second fluorescent layer  41  on a second substrate  40 , and supports  42  formed between the first substrate  30  and the second substrate  40 . 
     The first and second substrates  30  and  40  may be formed of glass or heat resistive flat material. The barrier layer  33  is formed of a material that can function as a reflective layer for directing UV light along an upward direction. The support  42  is arranged between the first and second substrates  30  and  40 , and supports the first and second substrates  30  and  40 , wherein sides of the support  42  are concave for providing improved discharge efficiency. In addition, side supports  43  provide support for the first substrate  30  and the second substrate  40 , and confine an inert gas, such as Xe, between the first and second substrates  30  and  40 . 
     In  FIG. 3 , upon application of a voltage to the first and second electrodes  31  and  32 , electrons emitted from the first electrode  31  collide with atoms of the inert gas to form a plasma that emits UV light. Then, the UV light collides with the second fluorescent layer  41  on the second substrate  40  to cause the second fluorescent layer  41  to emit white light. Accordingly, the white light passes through the second substrate  40  to emit a light from an entire upper surface of the second substrate  40 . However, the UV light cannot transmit through the supports  42 , and this dark spots are formed in areas of the fluorescent layer  41  where no white light is transmitted. Accordingly, since the dark spots deteriorate a uniform intensity of the white light, an additional spreading film must be incorporated. The spreading film decreases productivity, increases weight, and decreases an overall luminance of the flat-type fluorescent lamp device. Moreover, the process required for attaching the supports  42  between the first and the second substrates  30  and  40  at required positions further decreases productivity. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention is directed a flat-type fluorescent lamp device and a method of fabricating a flat-type fluorescent lamp device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art. 
     An object of the present invention is to provide a flat-type fluorescent lamp device and a method of fabricating a flat-type fluorescent lamp device that may function as a backlight unit for large sized LCD panels. 
     Another object of the present invention is to provide a flat-type fluorescent lamp device and a method of fabricating a flat-type fluorescent lamp device having a simplified fabrication process for improving productivity. 
     Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a flat-type fluorescent lamp device includes a first substrate, a plurality of first and second electrodes arranged on the first substrate at fixed intervals, a first fluorescent layer on an entire surface of the first substrate including the first and second electrodes, a second substrate having a plurality of projection portions for maintaining a uniform gap between the first and second substrates, and a second fluorescent layer on the second substrate except at regions of the projection portions that contact the first substrate. 
     In another aspect, a flat-type fluorescent lamp device includes first and second substrates, a plurality of first and second electrodes arranged on the first substrate at fixed intervals, a barrier layer covering surfaces of each of the first and second electrodes, a first fluorescent layer on an entire surface of the first substrate and the barrier layer, a plurality of supports each attached to a region of the second substrate for maintaining a uniform gap between the first and second substrates, and a second fluorescent layer on the second substrate except at regions where the supports are formed. 
     In another aspect, a method of fabricating a flat-type fluorescent lamp device includes forming a plurality of first and second electrodes at fixed intervals on a first substrate, forming a barrier layer on surfaces of each of the first and second electrodes, forming a first fluorescent layer on surfaces of the first substrate and the barrier layer, forming a second substrate having a plurality of projection portions, forming a second fluorescent layer on the second substrate excluding top regions of the projection portions, and bonding the first substrate and the second substrate together. 
     In another aspect, a method of fabricating a flat-type fluorescent lamp device includes forming a plurality of first and second electrodes on a first substrate, forming a barrier layer on surfaces of the first and second electrodes, forming a first fluorescent layer on the barrier layer, forming a first fluorescent layer on the first substrate including the barrier layer, forming a plurality of supports on a second substrate, each support having end portion, forming a second fluorescent layer on sidewall surfaces of the supports and the second substrate, and attaching the first and second substrates together,wherein the end portions of the supports contact first regions of the first fluorescent layer between adjacent ones of the first and second electrodes. 
     It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a cross sectional view of an edge-type backlight unit according to the related art; 
         FIG. 2  is a perspective view of an edge-type backlight unit according to the related art; 
         FIG. 3  is a cross sectional view of a flat-type fluorescent lamp device according to the related art; 
         FIG. 4  is a cross sectional view and a plan view of dark spots on the flat-type fluorescent lamp device in  FIG. 3  according to the related art; 
         FIG. 5  is a cross sectional view of an exemplary flat-type fluorescent lamp device according to the present invention; 
         FIGS. 6A to 6E  are cross sectional views of an exemplary method of fabricating a flat-type fluorescent lamp device according to the present invention; and 
         FIG. 7  is a cross sectional view of another exemplary flat-type fluorescent lamp device according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
       FIG. 5  is a cross sectional view of an exemplary flat-type fluorescent lamp device according to the present invention. In  FIG. 5 , a flat-type fluorescent lamp device may include a plurality of first and second electrodes  51  and  52  arranged on a first substrate  50  at fixed intervals, a barrier layer  53  covering on an entire surface of each of the first and second electrodes  51  and  52 , a first fluorescent layer  54  on an entire surface of the first substrate  50  including the first and second electrodes  51  and  52  and the barrier layer  53 , a second substrate  60  having projections for maintaining a gap with the first substrate  50 , and a second fluorescent layer  61  on the second substrate  60  except at top surfaces of the projections that contact the first substrate  50 . 
     Although not shown, the first electrodes  51  may be arranged on the first substrate  50  along a first direction at fixed intervals, and may each have first ends connected to each other with sharp projections formed at one or both sides thereof 
     The second electrodes  52  may be arranged along the first direction spaced at fixed distances apart from the first electrodes  51 , and may each have ends connected to each other. In addition, two of the second electrodes  52  may be arranged in parallel with, and between the first electrodes  51 . The first electrode  51  may be used as a cathode, and the second electrode  52  may be used as an anode. 
     The first and second substrates  50  and  60  may be formed of glass material or heat resistive material. The barrier layer  53  may function as a dielectric layer and may contain material(s) that can prevent electrons emitted during discharge between the first electrode  51  and the second electrode  52  from damaging the first and second electrodes  51  and  52 . In addition, the material(s) may function as a reflective layer for directing UV light along an upward direction. For example, the barrier layer  53  may be formed of at least one of AlN, BaTiO 3 , SiNx, and SiOx, and the first and second electrodes  51  and  52  may be formed of a low resistivity metal, such as silver Ag, chrome Cr, platinum Pt, and copper Cu. 
     The projection portions of the second substrate  60  may be formed as a unit with the second substrate  60  in order to maintain a uniform gap between the first and second substrates  50  and  60 . The projection portions of the second substrate  60  may have concave sides, wherein a first width of the projection portions that contact the second substrate  60  may be greater than a second width of the projection portions that contact the first substrate  50 , thereby increasing discharge efficiency. 
     In  FIG. 5 , side supports  62  may be provided for supporting sides of the first and second substrates  50  and  60 , and may be formed of material(s) of the first and second substrates  50  and  60 . In addition, the side supports  62  may also be formed as an integral unit with the second substrate  60 . Accordingly, the side supports  62  may function to contain a composite gas between the first and second substrates  50  and  60 . Thus, by forming the projection portions of the second substrate  60  to function as supports for maintaining the uniform gap between the first and second substrates  50  and  60 , occurrence of dark spots may be prevented. Since the second fluorescent layer  61  may not be formed at portions where the projection portions contact portions of the first substrate  50 , transmission of the UV light will be generated. 
       FIGS. 6A to 6E  are cross sectional views of an exemplary method of fabricating a flat-type fluorescent lamp device according to the present invention. In  FIG. 6A , first and second electrodes  51  and  52  may be formed at fixed intervals on a first substrate  50  by screen printing or photolithography that may include exposure and development processes. The first substrate  50  may be formed of a metal or an oxide, such as glass or heat resistive material, and the first and second electrodes  51  and  52  may be formed of silver Ag, chrome Cr, platinum Pt, or copper Cu. Accordingly, the first electrode  51  functions as a cathode and the second electrode  52  may function as an anode. 
     In  FIG. 6B , a barrier layer  53  may be formed to cover surfaces of the first and second electrodes  51  and  52 . Then, a first fluorescent layer  54  may be formed to cover the barrier layer  53  and surface portions of the first substrate  50  between the first and second electrodes  51  and  52 . The barrier layer  53  may include material(s) that functions both as a barrier for preventing damage by electrons emitted during discharge between the first and second electrodes  51  and  52  and as a reflective layer for preventing the UV light from being directed along a downward direction. The barrier layer  53  may include at least one of AlN, BaTiO 3 , SiNx, and SiOx. 
     In  FIG. 6C , a second substrate  60  may include a plurality of projection portions. The projection portions of the second substrate  60  may function as supports for maintaining a uniform gap between the first substrate  50  and the second substrate  60 . Each of the projection portions may be formed having concave side surfaces, wherein a first area of the projection portions that contact the second substrate  60  may be larger than a second area of the projection portions that contact portions of the first substrate  50 . Moreover, a first width of the projection portions that contact the second substrate  60  may be larger than a second width of the projection portions that contact portions of the first substrate  50 . The second substrate  60 , and the projection portions may include glass or heat resistive materials. 
     In  FIG. 6D , a second fluorescent layer  61  may be formed on the second substrate  60  except along top regions of the projection portions that will contact the portions of the first substrate  50 . 
     In  FIG. 6E , after bonding the first substrate  50  and the second substrate  60  with side supports  62 , a composite fluorescent gas that includes Xe may be injected through a gas injection hole (not shown), and sealed. In addition, the side supports may be formed as an integral unit with the second substrate  60  along with the projection portions. 
     Next, although not shown, a flexible printed circuit (FPC) may be soldered onto the first and second substrates  50  and  60  and to a connector assembly wire. Upon connection of the connector assembly to a power supply, UV light may be emitted from glow discharge as a result of an induced electric field between the first and second electrodes  51  and  52 , or from a plasma formed as electrons emitted from the first electrode  51  collide with the composite fluorescent gas. The UV light emitted collides with the second fluorescent layer  61  on the second substrate  60 , thereby emitting white light. In turn, the white light may-be reflected by the first fluorescent layer  54  formed on the barrier film and portions of the first substrate  50 , and may be directed such that the white light is transmitted from an entire upper surface of the second substrate  60 . Accordingly, formation of the projection portions as an integral unit with the second substrate  60  may prevent formation of dark spots. In addition, since separate formation processes of the supports  62  may not be required, an overall fabrication process of the flat-type fluorescent lamp device may be simplified, thereby improving productivity. Moreover, since no additional spreading film may be required for moderating the dark spots, an overall weight of the flat-type fluorescent lamp device may be reduced. 
       FIG. 7  is a cross sectional view of another exemplary flat-type fluorescent lamp device according to the present invention. In  FIG. 7 , a flat-type fluorescent lamp device may include a plurality of first and second electrodes  71  and  72  arranged on a first substrate  70  at fixed intervals, a barrier layer  73  covering on an entire surface of each of the first and second electrodes  71  and  72 , a first fluorescent layer  74  on an entire surface of the first substrate  70  including the barrier layer  73 , supports  82  attached to a region of the second substrate  80  for maintaining a uniform gap between the first and second substrates  70  and  80 , and a second fluorescent layer  81  on the second substrate  80  except at regions where the supports  82  may be formed. Although not shown, the first electrodes  71  may be arranged on the first substrate  70  along a first direction at fixed intervals, and may each have ends connected to each other and sharp projections may be included at one or both sides thereof. In addition, the supports  82  may include concave sides. 
     The first electrode  71  may function as a cathode, and the second electrode  72  may function as an anode. Alternatively, the first electrode  71  may function as an anode, and the second electrode  72  may function as a cathode. 
     The first and second substrates  70  and  80  may be formed of glass or heat resistive materials. The barrier layer  73  on the surfaces of the first and second electrodes  71  and  72  may include material(s) that may prevent damage caused by the electrons emitted in discharge between the first electrode  71  and the second electrode  72 . In addition, the material(s) of the barrier layer  73  may function as a reflective layer for directing UV light emitted in the discharge along an upward direction. For example, the barrier layer  73  may include at least one of AlN, BaTiO 3 , SiNx, and SiOx, and the first and second electrodes  71  and  72  may include a low resistivity metal, such as silver Ag, chrome Cr, platinum Pt, and copper Cu. 
     Side supports  83  may be provided for supporting sides of the first and second substrates  70  and  80 , and may include material(s) that are similar to material(s) of the first and second substrates  70  and  80 . In addition, the side supports may be provided to confine a composite gas, such as Xe, between the first and second substrates  70  and  80 . Accordingly, when a connector assembly is connected to the flat-type fluorescent lamp device to a power supply, UV light may be emitted from glow discharge induced by an electric field between the first and second electrodes  71  and  72 , or from a plasma formed as electrons emitted from the first electrode  71  collide with atoms of the composite gas. The emitted UV light collides with the second fluorescent layer  81  on the second substrate  80 , to emit white light that may be reflected by the barrier film  73  on the first substrate  70  and the first fluorescent layer  74 . Accordingly, the white light may be directed such that the white light is emitted from an entire upper surface of the second substrate  80 . 
     By not forming the second fluorescent layer  81  on portions of the supports  82 , an occurrence of dark spots may be prevented. For example, the UV light cannot pass through the supports  82 , and the second fluorescent layer  81  emits visible light when the UV light collides with the second fluorescent layer  81 . Since a portion of the visible light progresses between the first and second substrates  70  and  80 , most of the emitted visible light progresses to an upper part of the second substrate  80  to the LCD panel. 
     When the visible light between the first and second substrates  70  and  80  progresses through the supports  82 , if the second fluorescent layer  81  is formed on a part of the second substrate  80  that contacts the support  82 , a dark spot will be generated. However, if no second fluorescent layer  81  is formed on portions of the second substrate  80  where the supports  82  are formed, the visible light will pass through the supports  82  and the dark spots will not be generated. 
     The exemplary, flat-type fluorescent lamp devices in accordance with the present invention may be used not only as a lamp device but also as a separate light source at a rear or front of a display device, such as a monitor, a notebook computer, and a television. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.