Patent Publication Number: US-2006001356-A1

Title: FED including gate-supporting device with gate mask having reflection layer

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a FED, and particularly relates to an FED including a gate-supporting device with a gate mask that has a reflection layer.  
      2. Background of the Invention  
      There are several categories of a flat panel display (FPD), such as, for example a field emission display (FED), a thin film transistor-liquid crystal display (TFT-LCD), a plasma display panel (PDP), an organic electro-luminescence display (OELD), or a reflection-type liquid crystal display (LCD). Thinness, lightness, low power consumption, and portability are the common features of the FPDs mentioned above. The FED has many similarities to conventional cathode ray tubes (CRT). As for the CRT, electrons are accelerated in a vacuum towards phosphors, which then glows. The main difference from the CRT is that the electrons are generated by field emission rather than thermal emission, so the device consumes much less power and can be turned on instantly. Instead of one single electron gun, each pixel includes several thousand sub-micrometer or even nanometer tips from which electrons are emitted. The tips, made of low work-function materials, in particular of carbon nanotubes (CNTs) nowadays, are sharp, so that the local field strengths are high enough for even a moderately low gate voltage.  
      A conventional FED illustrated in  FIG. 1  includes a unit within an anode  10   a  and a cathode  20   a  disposed therein, and an insulating supporting member  15   a  (or a spacer) arranged between the anode  10   a  and the cathode  20   a  for separating the anode  10   a  from the cathode  10   a  and supporting the anode  10   a . The anode  10   a  includes an anode glass substrate  11   a , an anode conductive layer  12   a , and a phosphors layer  13   a  arranged sequentially. The cathode  20   a  includes a cathode glass substrate  21   a , a cathode electrode layer  22   a , a cathode electron emitter layer  23   a , a dielectric layer  24   a , and a gate layer  25   a  arranged sequentially. The insulating supporting member  15   a  is connected between the anode  10   a  and the cathode  10   a  to provide support. The cathode electron emitter layer  13   a  generates electrons for emission onto the phosphors layer  13   a  to produce light via an additional electric field, so as to excite the phosphors layer  13   a  to luminesce. Furthermore, the cathode electrode layer  22   a  is made from cathode conductive lines parallel to one another, and the gate layer  25   a  is made from gate conductive lines parallel to one another. The gate conductive lines are orthogonal to the cathode conductive lines. In addition, an additional voltage is forced between the gate layer  25   a  and the cathode electrode layer  22   a . An electron beam provided by the gate layer is controlled to switch due to the orthogonal arrangement between the gate conductive lines and the cathode conductive lines. For ease in moving the electrons, a vacuum of 10 −7  Torr is accordingly formed therein, a mean free path of the electrons is provided, and, furthermore, the vacuum can protect the cathode electron emitter layer  23   a  and the phosphors layer  13   a  from pollution. In order to accelerate the electrons for impact, there should be a proper distance between the anode  10   a  and the cathode  20   a ; after the anode  10   a  is provided with high power, the electron beam is energized enough to excite the phosphors.  
      A photolithographic method can be adopted for the conventional FED, but is still hard to mass-produce due to the complicated procedures and the precise fabrications.  FIG. 2  shows a gate mask  46 ′ applied thereto, and  FIG. 3  shows the gate mask  46 ′ arranged in an FED to replace the photolithographic method. The gate mask  46 ′ can be seen as an independent element disposed between the cathode  2 ′ and the anode  1 ′; a dielectric rib  24 ′ is supported between the cathode  2 ′ and the anode  1 ′. A vacuum cavity is formed thereby. The gate mask  46 ′ usually has a thickness of 50 μm to 200 μm and is laminated from a plurality of sheets with gate conductive lines. An effect of the resonance due to the gate mask can influence the display quality of the FED.  
      In recent years, a new insulating supporting member is shaped from a panel as a rib, referring to  FIG. 11 . An expansion coefficient of this material is similar to that of glass. The thickness of the plate-like device ranges from 500 μm to 1500 μm, and the plate-like device has a plurality of apertures  42 ′ etched therein. A diameter of each aperture  42 ′ matches the FED unit (including the anode and the cathode). The plate-like device is used for a support. The conventional supporting member is shaped as a glass ball, a cross, or a strip via an adhesive stuck thereto in advance. After a sintering process, a plate-like device is made thereby. The plate-like device has a size ranging from 50 μm to 200 μm. Because of the micro size, the plate-like device has some problems in manufacture. First, the plate-like device is complicated to manufacture; the equipment needs more precision due to the micro size. Second, the plate-like device sticky with the adhesive is polluted easily; because the conventional plate-like device uses adhesive to connect to a panel and a sintering process is required, the adhesive easily pollutes the panel. Third, after the sintering process, the solvent contained in the adhesive will escape therefrom to pollute the panel.  
      Hence, an improvement over the prior art is required to overcome the disadvantages thereof.  
     SUMMARY OF INVENTION  
      The primary object of the invention is therefore to specify an FED that includes a gate-supporting device with a reflection layer, where the gate-supporting device is combined with a gate mask.  
      The secondary object of the invention is therefore to specify an FED of which the gate-supporting device is manufactured individually to save cost.  
      The third object of the invention is therefore to specify an FED for which the elements individually manufactured in advance are assembled in simple steps.  
      These objects are achieved by an FED that includes a cathode having a plurality of cathode electron emitter layers and a cathode substrate, an anode having a phosphors layer and an anode substrate, and supporting device. The cathode includes a plurality of cathode ribs disposed on the cathode substrate, and the cathode ribs are used for laterally separating any respective two cathodes ribs. The cathode includes a gate made from a metallic mask and disposed above the cathode ribs. The supporting device is arranged between the metallic mask and the anode, and has a reflection layer towards the anode. The reflection layer is capable of reflecting the light emitted from the phosphors layer.  
      To provide a further understanding of the invention, the following detailed description illustrates embodiments and examples of the invention. Examples of the more important features of the invention thus have been summarized rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contributions to the art may be appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject of the claims appended hereto. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings, where:  
       FIG. 1  is a cross-sectional profile of a conventional FED;  
       FIG. 2  is a perspective view of a conventional gate mask;  
       FIG. 3  is a perspective view of a conventional FED with a conventional gate mask;  
      FIGS.  4  to  6  are perspective views of a supporting device with a reflection layer and a gate according to the present invention;  
      FIGS.  7  to  9  are perspective views-of three embodiments of a gate mask;  
       FIG. 10  is a perspective view of the FED according to the present invention; and  FIG. 11  is a perspective view of the supporting device.  
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       FIG. 10  shows an FED that includes a cathode  2 , an anode  1  and a supporting device  38 . The cathode  2  has a plurality of cathode ribs  24 , a plurality of cathode electron emitter layers  23 , a cathode electrode layer  22  and a cathode glass substrate  21 . The anode  1  has a plurality of anode ribs  14 , an anode conductive layer  12 , a phosphors layer  13  and an anode substrate  11 . The supporting device  38  has a reflection layer  44 . The cathode ribs  24  are arranged over the cathode substrate  21 , and adjacent to a gate  46  of the supporting device  38 . The cathode ribs  24  are alternately arranged with the cathode electron emitter layers  23 . The thickness of each of the cathode ribs  24  is a factor in determining an additional field over the gate  46  and the cathode electrode layer  22  and controlling the capacity of electrons emitted from the cathode electron emitter layers  23  by the gate  46 . The cathode ribs  24  replace the conventional dielectric layer  24   a.    
      With respect to FIGS.  4  to  6 , the supporting device  38  includes a plurality of apertures  42  formed therein. The supporting device  38  is used to support the cathode  2  and the anode  1 , and the apertures  42  provide a cavity for relative electrons. The supporting device  38  is made of insulating materials, and the reflection layer  44  is arranged on a side of the supporting device  38  to correspond to the anode for light reflection. The luminance is increased thereby, and a periphery surrounding the reflection layer is an ineffective area used for sealing and alignment. The gate  46  is arranged on an opposite side of the supporting device  38 . The gate  46  is made from gate conductive lines  461 . A first type of the gate  46  is made of a metallic mask after the etching process; the gate conductive lines include a plurality of holes relating to through holes of the supporting device  38 . The gate conductive lines are parallel to one another and orthogonal to the cathode conductive lines of the cathode electrode layer  22 . The cathode conductive lines of the cathode electrode layer  22  are parallel to one another.  FIG. 4  shows a second type of the gate  46  made of a metallic mask after etching process, too. Any two of the gate conductive lines is taken as a line unit, and an aperture is formed in the line unit. The aperture corresponds to a respective one of the through holes of the supporting device  38 . The line unit is orthogonal to the cathode conductive lines of the cathode electrode layer  22 .  FIG. 5  illustrates a third type of the gate  46 , a plurality of metallic lines parallel to one another, where any two of the gate conductive lines are a line unit, and an aperture is formed in the line unit, too. The aperture corresponds to a respective one of the through holes of the supporting device  38 . The line unit is orthogonal to the cathode conductive lines of the cathode electrode layer  22 . The anode ribs  14  relates to the apertures  42  as a plurality of passageways formed between the anode ribs  14  and communicating with the apertures  42 , respectively. The reflection layer of the supporting device  38  can be made of a glass substrate with apertures  42  by sputtering or evaporation. The gate mask contacts the opposite side of the glass substrate. A gate mask before cutting is shown in FIGS.  7  to  9 . Materials with similar expansion coefficients are applicable to the supporting device  38  and the gate mask. The gate mask is divided into an effective contact area and an ineffective removable area. The effective contact area of the gate mask is used easily via a glass glue for connection and supports the support device  38 . A semi-product with the gate conductive lines can be sliced to remove the ineffective area for the gate conductive lines individually.  
      The steps of the making the FED includes making a plurality of cathode ribs  24  and anode ribs  14 , respectively disposed on the cathode electron emitter layer  23  of the cathode  20  and the phosphors layer  13  of the anode  10 . The cathode ribs  24  and the anode ribs.  14  are arranged between the reflection layer  44  and the gate  46  and adjacent to the apertures  42 . Glue (UV glue) and a binder are applied to a predetermined position of the ineffective area  43  (see  FIG. 11 ) to false-connect the supporting device  38  between the cathode  2  and the anode  1 . After a sintering process, the UV glue can be removed due to the oxidization, or the binder can be hardened to secure the supporting device  38 . The supporting device  38  can be aligned with precision. The unit of the anode  1  and the cathode  2  can align with the apertures. The false-connect process or clamping equipment can be adopted. The semi-product after false connection is then sintered in order to secure the supporting device  38  between the anode  1  and the cathode  2 .  
      The materials with similar expansion coefficients will increase the precision of the alignment between the supporting device  38  and the gate  46 . Furthermore, the similar expansion coefficients of these materials helps the alignment between the cathode  2  and the anode  1 .  
      For further detailed descriptions, the reflection layer  44  faces the phosphors layer  11 . The phosphors layer  11  is processed in a screen-printing manner or a spreading manner. The cathode electron emitter layers  23  are processed in a screen-printing manner or a spreading manner. Each of the cathode electron emitter layers  23  includes a plurality of property-improving carbon nanotubes (like dotting carbon nanotubes) and is capable of high electron emission efficiency. The supporting device  38  has a plurality of apertures  42  formed on the reflection layer  44 , and each of the cathode electron emitter layers is formed on each of the apertures  42 . The reflection layer is made of aluminum or chromium. The cathode ribs  24  and the anode ribs  14  are fabricated by photolithography or screen-printing. An adhesive with glass is provided and is capable of connecting the anode  1  and the cathode  2  after a sintering process. The metallic mask  46  has an expansion coefficient ranging from 10 −6  to 10 −7  per degree centigrade. The metallic mask  46  has a thickness ranging from 50 μm to 100 μm. Each of the anode ribs  14  has a thickness ranging from 50 μm to 100 μm, and each of the cathode ribs  24  has a thickness ranging from 30 μm to 60 μm. The metallic mask  46  is made of ferro-nickel alloy materials. The supporting device  38  has an expansion coefficient ranging from 82×10 −6  to 86×10 −7  per degree centigrade. The driving power is designed as 80 voltages.  
      The present invention is characterized by an easy manufacturing process, mass production, low costs and less equipment.  
      It should be apparent to those skilled in the art that the above description is only illustrative of specific embodiments and examples of the invention. The invention should therefore cover various modifications and variations made to the herein-described structure and operations of the invention, provided they fall within the scope of the invention as defined in the following appended claims.