Abstract:
A method of fabricating a dielectric layer for a plasma display device that is suitable for forming the dielectric layer through a simple process and improving a characteristic of the dielectric layer. In order to fabricate the dielectric layer, non-crystallized glass powder is prepared. The non-crystallized powder is deposited on a substrate after it is mixed with oxide powder.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a plasma display device, and more particularly to a method of fabricating a dielectric layer for a plasma display device wherein the dielectric layer is formed by depositing dielectric powder on a substrate directly. Also, this invention is directed to a method of fabricating a fluorescent film wherein the fluorescent film is formed by depositing fluorescent powder on a substrate directly. 
     2. Description of the Related Art 
     A conventional alternative current system plasma display panel (hereinafter, AC-system PDP) includes a lower glass substrate  10  mounted with an address electrode  12 , and an upper glass substrate  20  mounted with a transparent electrode pair  22 , as shown in FIG. 1. A lower dielectric thick film  14  with a predetermined thickness for forming a wall charge and a barrier rib  16  for dividing discharge cells are sequentially formed on the lower glass substrate  10  mounted with the address electrode  12 . A fluorescent film  18  is coated on the surface of the lower dielectric thick film  14  and the wall surface of the barrier rib  16  into a predetermined thickness. The fluorescent film  18  is radiated by an ultraviolet generated during the plasma discharge to generate a visible light. Meanwhile, an upper dielectric thick film  24  and a protective film  26  are sequentially formed on the bottom surface of the upper glass substrate  20  mounted with the transparent electrode pair  22 . The upper dielectric thick film  24  forms a wall charge like the lower dielectric thick film  14 , and the protective film  26  protects the upper dielectric thick film  24  from an impact of gas ions during the plasma discharge. Such an AC-system PDP has discharge cells formed by isolating the lower and upper glass substrates  10  and  20  through the barrier rib  16 . He+Xe mixture gas or Ne+Xe mixture gas is sealed into the discharge cells. 
     All the lower and upper dielectric thick films  14  and  24  used in such an AC-system PDP must have a capability of performing a function of anti-diffusion film as well as improving the discharge sustenance and the radiation efficiency. In order to perform a function of anti-diffusion film, all the lower and upper dielectric thick films  14  and  24  must have a high thermal stability, a high calcining temperature and a dense organization. Also, in order to improve the radiation efficiency, that is, in order to improve the brightness, the lower glass substrate  14  must have a high reflective coefficient in such a manner to reflect a visible light back-scattered from the fluorescent film  18  while the upper glass substrate  24  must a high transmissivity in such a manner to transmit visible lights from the fluorescent film  18  as much as possible. Furthermore, in order to improve the discharge sustenance, the lower dielectric thick film  14  must have a low dielectric constant while the upper dielectric thick film  24  must have a high dielectric constant. For instance, it is required that the upper dielectric thick film  24  have a dielectric constant more than “13” and the lower dielectric thick film  14  have a dielectric constant less than “10”. 
     The dielectric thick films  14  and  24  are formed by a process as shown in FIG.  2 . In step  30 , non-crystallized glass powder is prepared. In order to prepare the non-crystallized glass powder, raw materials of a SiO 2 —ZnO—B 2 O 3  group non-crystallized glass or a P 2 O 5 —ZnO—BaO group non-crystallized glass are mixed at a desired component ratio. The raw materials of the mixed SiO 2 —ZnO—B 2 O 3  group non-crystallized glass or a P 2 O 5 —ZnO—BaO group non-crystallized glass are heated for about 5 hours into a temperature of about 1100° C. at a melting furnace to be melted. In the period of melting the raw materials of the non-crystallized glass, the raw materials is stirred two or three times to produce a uniform liquid-state non-crystallized glass. The liquid-state non-crystallized glass is suddenly cooled to thereby have a dense organization and to produce glass cullets with minute cracks. The cullets are milled for a desired time (e.g., 16 hours) by the ball milling technique and thereafter passes through #170 and #270 sievers sequentially, thereby making non-crystallized powder having a particle size of about 6 μm. In step  32 , such non-crystallized glass powder is mixed with filler powder at a predetermined component ratio. The non-crystallized glass powder and the filler powder having the predetermined component ratio is mixed during a desired time (e.g., 10 hours) by means of a tumbling mixer. In step  34 , the non-crystallized glass powder and the filler powder mixed in this manner is mixed with an organic vehicle at a predetermined component ratio to thereby produce a paste. Herein, a mixture of butyl-carbitol-acetate(ICA), butyl-carbitol(BC) and ethyl-cellulose(EC) with the organic vehicle at a desired ratio is used as the organic vehicle. A viscosity of the paste is varied in accordance with a quantity of EC to have an influence on the rheology and sintering characteristic. Subsequently, in step  36 , the paste is coated on the glass substrate  10  or  20  at a uniform thickness. The coating of the paste is carried out by a repetitive screen printing. In the screen printing technique, as shown in FIG. 3A, a screen  40  is installed at the upper portion of the glass substrate  10  or  20 , and a paste  42  is disposed on one edge of the screen  40 . The paste  42  is pushed into other edge of the screen  40  in such a manner to be coated on the glass substrate  10  or  20  at a constant thickness as shown in FIG.  3 B. Then, the paste  42  is again put on one edge of the screen  40  as shown in FIG.  3 C. The paste  42  is further pushed into other edge of the screen  40  by a squeezer such that it is again coated on the glass substrate  10  or  20  as shown in FIG.  3 D. By such a repetitive screen printing, the paste  42  is coated on the glass substrate  10  or  20  at a desired thickness (e.g., 15 to 20 μm). The glass substrate  10  or  20  coated with the paste  42  in this manner is dried during a desired time (e.g., about 20 to 30 minutes) at a temperature of 350 to 400° C. within a dry oven (not shown) at the atmosphere. At this time, an organic vehicle included in the paste is completely burned out. After the organic vehicle is completely eliminated, the glass substrate  10  or  20  is heated into the crystallization temperature during a desired time to sinter a non-crystallized glass included in the paste  42 . Consequently, the glass substrate  10  or  20  is cooled during a desired time(e.g., about 40 minutes) at a cooling time of 6° C./min to form a dielectric thick film  14  or  24  on the glass substrate  10  or  20 . Herein, the paste  42 , that is, a sintering temperature of the dielectric thick film  14  or  24  is set to less than 600° C. so as to minimize a thermal deformation of the glass substrate,  10  or  20 . 
     Such a screen printing technique complicates a dielectric thick film fabricating method because it needs a forming process and a sintering process of the paste. The calcining temperature is too low at the time of sintering the paste, the dielectric thick film is not eliminated completely to have a non-uniform surface. Due to this, the dielectric thick film absorbs or scatters a visible light to have a low light transmissivity. On the contrary, when the calcining temperature is too high, the surface of the dielectric thick film is damaged. As a result, a bonding between the dielectric thick film and the protective film is not only weakened, but also a characteristic of the protective film is deteriorated. The fluorescent film included in the PDP along with the dielectric thick film also is formed by the paste producing process, the screen printing process and the sintering process in similarity to the dielectric thick film. Due to this, the fluorescent film fabricating method also is complicated like the dielectric thick film fabricating method. Furthermore, the fluorescent thick film also has a non-uniform surface because an air gap is not eliminated completely. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an object of the present invention to provide a method of fabricating a dielectric layer for a plasma display device that is suitable for forming the dielectric layer through a simple process as well as improving a characteristic of the dielectric layer. 
     Further object of the present invention is to provide a method of fabricating a fluorescent film for a plasma display device that is adaptive for forming the fluorescent film through a simple process. 
     In order to achieve these and other objects of the invention, a method of fabricating a dielectric layer for a plasma display device according to one aspect of the present invention includes the steps of preparing non-crystallized glass powder; mixing the non-crystallized glass powder with oxide powder; and depositing the mixture power of the non-crystallized glass powder and the oxide powder. 
     A method of fabricating a fluorescent film for a plasma display device according to another aspect of the present invention includes the steps of preparing fluorescent powder; and depositing the fluorescent powder on a substrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other objects of the invention will be apparent from the following detailed description of the embodiments of the present invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic view showing the structure of a conventional plasma display device; 
     FIG. 2 is a flow chart for explaining a conventional dieletric thick film fabricating method; 
     FIGS. 3A to  3 D are sectional view of a glass substrate for explaining a procedure in which a paste is printed on the glass substrate by the conventional screen printing process; 
     FIG. 4 is a flow chart for explaining a method of fabricating a dielectric thick film for a plasma display device according to an embodiment of the present invention; and 
     FIG. 5 is a schematic sectional view showing the structure of a direct current plasma jet deposition device. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 4 for explaining a method of fabricating a dielectric thick film according to an embodiment of the present invention, in step  50 , non-crystallized glass powder is prepared. In order to prepare the non-crystallized glass powder, raw materials of a SiO 2 —ZnO—B 2 O 3  group non-crystallized glass or a P 2 O 5 —ZnO—BaO group non-crystallized glass are mixed at a desired component ratio. The raw materials of the mixed SiO 2 —ZnO—B 2 O 3  group non-crystallized glass or a P 2 O 5 —ZnO—BaO group non-crystallized glass are heated for about 5 hours into a temperature of about 1000° C. to 1100° C. at a melting furnace to be melted. In the period of melting the raw materials of the non-crystallized glass, the raw materials is stirred two or three times to produce a uniform liquid-state non-crystallized glass. The liquid-state non-crystallized glass is suddenly cooled to thereby have a dense organization and produce glass cullets with minute cracks. The cullets are milled for a desired time (e.g., 16 hours) by the ball milling technique and thereafter passes through #170 and #270 sievers sequentially, thereby making non-crystallized powder having a particle size of about 5 μm. In step  52 , such non-crystallized glass powder is mixed with several weight % of filler powder at a predetermined component ratio. The non-crystallized glass powder and the filler powder are mixed during a desired time (e.g., 10 hours) by means of a tumbling mixer. Oxide powder expediting a crystallization of the non-crystallized glass is used as the filler powder. The oxide powder consist of articles having a size of about 3 μm. Mixture powder of the non-crystallized glass powder and the oxide powder is kept at a constant temperature within a dry oven. 
     In step  54 , the mixture powder of the non-crystallized glass powder and the filler powder is vapor-deposited on the glass substrate  10  or  20  in which an electrode  12  or  22  is formed by a direct current arc plasma jet deposition (DC-APJD) device as shown in FIG.  5 . In order to deposit the mixture powder on the glass substrate  10  or  20 , the glass substrate  10  or  20  in which the electrode  12  or  22  is formed, is mounted into a substrate holder  50  cooled by a water. When an argon gas is supplied at a flux of 8 to 10 l/min through a gas injection hole  52  and, at the same time, a desired electric power (e.g. 30 to 50 kW) is applied between a cathode  54  and an anode  56 , a jet plasma  58  with a high temperature (e.g., 6000° C. to 10000° C.) generated by ionizing and suddenly expanding the argon gas is ejected into the glass substrate  10  or  20  at the speed of sound. The jet plasma  58  is subject to have a high density and a stabilization when it passes a magnetic field formed by a magnetic coil  60  Under this state, if the mixture powder of the non-crystallized glass powder and the oxide powder is supplied through a powder injection hole  62 , then non-crystallized glass articles of about 5 μm and oxide articles of about 3 μm have their surface melted instantaneously by the jet plasma with a temperature of 6000° C. to 10000° C. and are ejected into the glass substrate  10  or  20  at the speed of sound to thereby be attached onto the glass substrate  10  or  20 . At this time, because the jet plasma is subject to a high density and a uniformity by the magnetic field, the mixture powder ejected along with the jet plasma also are distributed densely and uniformly. Accordingly, a dielectric thick film having minute particles of 0.1 to 1 μm distributed densely and uniformly is obtained on the glass substrate  10  or  20 , Also, the dielectric thick film  14  or  24  has a low air perforation rate. As a result, the dielectric thick film  14  or  24  has a reduced dielectric loss. Further, the dielectric thick film  14  or  24  is strongly bonded to the protective film and permits a characteristic of the protective film to be improved. Moreover, the dielectric thick film  14  or  24  formed in the above-mentioned manner may undergo a thermal treatment so as to have a more dense and uniform particle structure. Meanwhile, the DC-APJD device shown in FIG. 5 is installed within a vacuum chamber (not shown) in which an atmosphere within itself is exhausted into about 10 −6  Torr by a vacuum pump to have a vacuum state. The method of vapor-depositing the powder onto the substrate using the DC-APJD device is referred to as “direct arc plasma deposition method”. 
     Hereinafter, a method of fabricating a fluorescent film according to an embodiment of the present invention will be explained. In order to form red(R), green(G) and blue(B) fluorescent films on the glass substrate provided with a dielectric thick film and a barrier rib, R, G and B fluorescent powder is prepared. Each of the R, G and B fluorescent powder consists of oxide particles. The R fluorescent powder is deposited on the wall surfaces of the dielectric thick film and the barrier rib by means of the DC-APJD as shown in FIG.  5 . Subsequently, the G fluorescent powder and the B fluorescent powder are sequentially deposited on the wall surfaces of the dielectric thick film and the barrier rib into a constant thickness by means of the DC-APJD device. The R, G and B fluorescent films are deposited on the glass substrate provided with the dielectric thick film and the barrier rib into a constant thickness by the direct current plasma deposition method, so that the fluorescent films can have a organization structure in which fluorescent particles thereof are densely and uniformly distributed. 
     As described above, in the dielectric thick film fabricating method according to the present invention, the mixture powder of the non-crystallized glass powder and the filler powder is deposited directly on the glass substrate. Accordingly, the dielectric thick film fabricating method according to the present invention is capable of eliminating the paste producing process, the screen printing process and the sintering process. Also, the dielectric thick film fabricating method can prevent a characteristic of the dielectric thick film from being deteriorated due to a sintering temperature during the sintering process. Moreover, the dielectric thick film fabricating method may be applied to an easy fabrication of the barrier rib without using the screen printing method. In this case, a productivity of the plasma display device is improved. 
     In addition, in the fluorescent film fabricating method according to the present invention, the mixture powder of the non-crystallized glass powder and the filler powder is deposited directly on the glass substrate. Accordingly, the dielectric thick film fabricating method according to the present invention is capable of eliminating the paste producing process, the screen printing process and the sintering process. Also, the dielectric thick film fabricating method can prevent a characteristic of the dielectric thick film from being deteriorated due to a sintering temperature during the sintering process. 
     Although the present invention has been explained by the embodiments shown in the drawings described above, it should be understood to the ordinary skilled person in the art that the invention is not limited to the embodiments, but rather that various changes or modifications thereof are possible without departing from the spirit of the invention. Accordingly, the scope of the invention shall be determined only by the appended claims and their equivalents.