ATOMIZER FOR FORMING A THIN FILM

Abstract: There is disclosed an atomizer for forming a thin film comprising an atomizing box (13), a guide tube (21) having one open end of small diameter and the other open end of large diameter, a nozzle (17) having an ejection outlet disposed in the atomizing box (13), an atomizing solution reservoir (15) defined in the atomizing box (13) and confronting the other open end of large diameter of the guide tube (21), and a fluid return passage defined around the circumference of the guide tube (21) for returning the atomized solution from the atomizing solution reservoir (15) to the one open end thereof. The atomizing box (13) can have a plurality of guide tubes (21) each provided with a nozzle (17). The guide tube (21) can have a plurality of nozzles (17).

Description: The present invention relates to an atomizer for atomizing a solution of a material, feeding the resultant atomized solution into a film formation chamber where the atomized solution contact a heated substrate to form the thin film on the surface of the substrate. The conventional atomizer comprises a nozzle in a wind tunnel for atomizing a solution of a material, a blower provided at a rear side of the nozzle for feeding the atomized solution, a feeding device for receiving and feeding the atomized solution to a film formation chamber. The conventional film forming device has the problem that the atomized solution fed from the feeding device shows wide variety in the diameter thereof, and has many coarse particles. If the atomized solution to collide with the surface of the substrate has many coarse particles, the thickness and quality of the film formed on the substrate is liable to be locally uneven. That is, it is important that the atomized solution to collide with the surface of the substrate has fine particles as many as possible for forming the thin film having a uniform thickness and quality. A further developed film forming device is disclosed in FR-A-2291800, wherein a solution is sprayed into gaseous stream and the resulting two-phase mixture gas-droplet is directed into a discriminating chamber, said discriminating chamber comprising an arrangement of dischargers and reflectors enabling to feed only particles having a predetermined size into a film formation chamber. Particles having a size exeeding this predetermined value can either be reflected back into the direction of the nozzle providing the atomized solution or spray and thereby getting into the way and distracting the jet containing material for forming thin films and carrier gas, or can instead of being directed onto the film be directed into a solution reservoir being a solution supply source for said nozzle, whereby this fluid return line is complicated as not being installed within the mixing and discriminating device. The present invention is made to solve the problems of the conventional thin film forming devices. Hence, it is an object of the present invention to provide an atomizer for efficiently forming a thin film capable of feeding the atomized solution having only the fine particles by controlling the fluid passage within the atomizer. To achieve the above object, the atomizer for forming thin film comprises an atomizing box, a guide tube disposed in the atomizing box, having an open end of small diameter and the other open end of large diameter, a nozzle having an ejection outlet disposed in the atomizing box and directed from the one open end of small diameter to the other open end of large diameter of the guide tube, an atomized solution reservoir defined in the atomizing box and confronting the other open end of large diameter of the guide tube, an atomized solution discharger connected to said atomized solution reservoir, and a fluid return passage defined around the circumference of the guide tube, which passage reaches from said atomized solution reservoir through a plurality of perforations within a partition supporting the guide tube at it's large diameter end in the atomizing box to the small diameter open end of said guide tube. The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings. Fig. 1 is a perspective view showing partly cutaway atomizer for forming a thin film according to a first embodiment of the present invention; Fig. 2 is a longitudinal cross sectional side view of the atomizer for forming a thin film of Fig. 1; Fig. 3 is a perspective view showing partly cutaway atomizer for forming a thin film according to a second embodiment of the present invention; Fig. 4 is a lateral cross sectional plan view of the atomizer for forming a thin film of Fig. 3; Fig. 5 is a perspective view showing partly cutaway atomizer for forming a thin film according to a third embodiment of the present invention; Fig. 6 is a lateral cross sectional plan view of the atomizer of Fig. 5; and Fig. 7 is longitudinal cross sectional view of a thin film forming device employing the atomizer. An atomizer for forming a thin film (hereinafter referred to as atomizer) includes an atomizing box 13 of a cubic shape which box has one side surface provided with a through hole 24. The atomizing box 13 has a guide tube 21 which is disposed therein and is tapered to increase its inner diameter from one open end facing the through hole 24 to the other open end. A nozzle 17 is inserted into the atomizing box 13 from the through hole 24 and has an ejection outlet positioned in the atomizing box 13 and directed from one open end of a small diameter of the guide tube 21 to the other open end of a large diameter of the guide tube 21. A solution is jetted so as to be dispersed as the atomized particle in the pressurized air. The thus jetted atomized particle is also jetted toward the other open end of large diameter of the guide tube 21. The guide tube 21 has a partition of a handguard shape at the periphery of the other open end of large diameter for partitioning the atomizing box 13 perpendicularly. The partition 14 supports the guide tube 21 in the atomizing box 13 and defines an atomized solution reservoir 15 in the atomizing box 13 at the side of the other open end of large diameter of the guide tube 21. The partition 14 is perforated to provide a plurality of through holes 16 or perforations which are arranged in the manner to surround the other open end of large diameter of the guide tube 21. A return passage is defined between the atomized solution reservoir 15 and the one open end of small diameter of the guide tube 21 via the perforations 16 and the space around the outer periphery of the guide tube 21. The atomized solution reservoir 15 has a long cylindrical atomized solution discharger 3 which is protruded from an upper wall of the atomized solution reservoir 15. The particle of the atomized solution in the atomized solution reservoir 15 rises from the atomized solution discharger 3 and fed to a film formation chamber 4 of the thin film forming device. As illustrated in Fig. 2, when the atomizing solution is jetted together with the pressurized air from the nozzle 17 attached to the side surface of the atomizing box 13, the atomizing solution is dispersed into the pressurized air in the atomized state and jetted into the guide tube 21. The atomizing solution thus jetted in the guide tube 21 spreads and flows toward the atomized solution reservoir 15 through the other open end of large diameter. At this time, the particle of the atomized solution is coarse at the peripheral portion adjacent to the guide tube 21 and is dispersed in the periphery of the jetting route of the atomized solution and adhered to the wall surface of the guide tube 21. The atomized solution having coarse particles located in the center of the jetting route of the atomized solution is jetted far away than that of the fine particles and reaches and collides with the wall surface of the atomized solution reservoir 15 (left side wall in Fig. 2). Hence, the atomized solution having relatively large or coarse particles is adhered to the guide tube 21 or the wall surfaces of the atomizing box 13 so that the atomized solution having relatively coarse particles will be changed to a liquid drop and eliminated from the floating atomized solution. The one open end of the guide tube 21 at the side of the nozzle 17 has an area in cross section less than that at the side of the atomized solution reservoir 15, hence the speed of floating or running fluid is rapid to form a negative pressurized flow. Accordingly, part of the atomized solution in the atomized solution reservoir 15, particularly the particle of the atomized solution collected in the end or the periphery of the atomized solution reservoir 15 is returned to the one open end of the small diameter of the guide tube 21 via the space defined circumference of the atomizing guide tube 21. The coarse particle of the atomized solution thus returned to the nozzle 17 is eliminated during running in the jetting route so that the fine particle is returned to the atomized solution reservoir 15 and fed to the upward via the atomized solution discharger 3. A schematic arrangement of the thin film forming device employing the atomizer will be illustrated in Fig. 7. In the thin film forming device, the atomizing solution of a material for forming the thin film and a carrier gas (air in most cases) are fed from a solution supply source 23 and an air supply device 2 to the nozzle 17 wherein the atomizing solution is jetted and discharged from an outlet 3a of the atomized solution discharger 3. A film formation chamber 4 is provided over the oulet 3a of the atomized solution discharger 3 in which the atomized solution is floated. There are provided substrates 6 such as glass plates and the like for forming a ceiling of the film formation chamber 4 so as to be successively continuing over the film formation chamber 4 and fed from the left side to the right side in Fig. 7 while it is kept in the film formation chamber 4. The substrates 6 are heated at a predetermined temperature by a heater 8 provided at the rear side thereof via a uniform heating plate 7. The substrates 6 are entered from a substrate entrance 9 and fed successively to be discharged from a substrate outlet 10 via the film formation chamber 4. In the film formation chamber 4 there is provided the outlet 3a of the atomized solution discharger 3 at the lower surface of the film formation chamber 4 and directed from the lower side to the upper side thereof. The atomized solution discharged from the outlet 3a is floating gently in the film formation chamber 4 in the direction of an outlet 5 provided adjacent to the substrate outlet while contacting the surfaces of the substrates 6. The atomized solution reacts on oxygen in the air or liquid in the atomized solution so that the oxydized thin film is formed on the surface of the substrates 6. The atomized solution which is not contributed to form the thin film oxide on the surfaces of the substrates 6 are discharged from the outlet 5. The atomizer for foming a thin film according to the present invention will be described more in detail with reference to comparative examples thereof. The atomizing box 13 is the cubic shaped container having length of 1.3 m, the height of 80 cm and the width of 80 cm and provided with the nozzle 17 at one side surface thereof (right side surface in the figures). The nozzle 17 can jet gas fluid and liquid fluid from the ejection outlet at the same time both of which are atomized. In this case, the two fluids are jetted under the air pressure of 5 kg/cm². Chloride solution of Sn and In are employed as the atomizing solution and jetted under the liquid pressure of 0.2 kg/cm² for the liquid volume of 4 ℓ/h. As a result, most of the particle of the atomized solution discharged from the atomized solution discharger 3 toward the upper portion thereof are minute and uniform with the diameter less than 10 mµ when five minutes elapsed after the atomizing solution was jet from the ejection outlet of the nozzle 17. There is employed, for forming the atomized solution, a thin film forming device having substantially same arrangement of the first embodiment except that the guide tube 21 is not provided so that the return flow passage is not defined. The atomized solution discharged from the outlet has the atomized particle having the diameter of more than 10 mµ. This is caused by so called knocking at the jetting port of the nozzle 17 due to the large variation of the pressure in the atomizing box 13. A second embodiment of the atomizer according to the present invention will be described with reference to Figs. 3 and 4. A pair of guide tubes 21, 21 respectively provided with nozzles 17, 17 are disposed in parallel with each other in the atomizing box 13. Inasmuch as the nozzles 17, 17 are separated from each other by the guide tubes 21, 21, hence the atomized solution is hardly interferes with each other. Accordingly, a large amount of solution is not jetted from each nozzle 17 which results in increasing two times of the discharging amount of the atomized solution discharged from the atomized solution discharger 3 without jetting a large amount of atomized solution. As a result, it is possible to discharge a large amount of atomizing solution having fine particle with the time per unit. A third embodiment of the atomizer according to the present invention will be described with reference to Figs. 5 and 6. The guide tube 21 has two nozzles 17, 17 at the one open end or the base end thereof. The two nozzles 17, 17 are disposed symmetrically relative to the central axis of the guide tube 21 for thereby jetting the atomizing solution in the direction parallel to the central axis. If the two nozzles 17, 17 are disposed at the position adjacent to each other, the atomized solution jetted by the nozzles 17, 17 interferes with each other to produce the atomized solution having coarse particles. The atomized solution having coarse particle collides with the wall surface of the guide tube 21 and the wall surface confronting the atomizing solution reservoir 15 where the atomized solution having coarse particles is eliminated so that the amount of the atomized solution to be supplied to the film formation chamber is reduced compared with the atomizer of the second embodiment provided with the pair of nozzles 17, 17 as illustrated in Figs. 3, 4. It is possible to provide the guide tubes 21, 21 respectively having two nozzles 17, 17. Although the invention has been described in its preferred form with a certain degree of particularity, it is to be understood that many variations and changes are possible in the invention without departing from the scope of the claims.

Claims: An atomizer for forming a thin film comprising: an atomizing box (13); a guide tube (21) disposed in the atomizing box (13), having an open end of small diameter and the other open end of large diameter; a nozzle (17) having an ejection outlet disposed in the atomizing box (13) and directed from the one open end of small diameter to the other open end of large diameter of the guide tube (21); an atomized solution reservoir (15) defined in the atomizing box (13) and confronting the other open end of large diameter of the guide tube (21); an atomized solution discharger (3) connected to said atomized solution reservoir (15); and a fluid return passage, characterized in that said fluid return passage is defined around the circumference of the guide tube (21), which passage reaches from the atomized solution reservoir (15) through a plurality of perforations (16) within a partition (14) supporting the guide tube (21) at it's large diameter end in the atomizing box (13) to the small diameter open end of said guide tube (21). An atomizer for forming a thin film according to claim 1, wherein the atomizing box (13) has a plurality of guide tubes (21) each provided with a nozzle (17). An atomizer for forming a thin film according to claim 1, wherein the guide tube (21) has a plurality of nozzles (17). An atomizer for forming a thin film according to claim 1, wherein the guide tube (21) has an inner diameter which is tapered to increase from the one end to the other end thereof. An atomizer for forming a thin film according to claim 1, wherein the nozzle (17) can jet air fluid and liquid fluid at the same time from the ejection outlet of the nozzle (17). An atomizer for forming a thin film according to claim 1, wherein the nozzle (17) can jet liquid fluid from the ejection outlet of the nozzle (17).

Inventors: FUKAI, KIKUJI, IIDA, HIDEYO, IMAI, MIZUHO, ITO, ATSUO, KATO, KOMEI, SEKIGUCHI, MIKIO, FUKAI, KIKUJI, C/O TAIYO YUDEN CO, LTD., IIDA, HIDEYO, C/O TAIYO YUDEN CO, LTD., IMAI, MIZUHO, C/O TAIYO YUDEN CO, LTD., ITO, ATSUO, C/O TAIYO YUDEN CO, LTD., KATO, KOMEI, C/O TAIYO YUDEN CO, LTD., SEKIGUCHI, MIKIO, C/O TAIYO YUDEN CO, LTD.
Applicants: TAIYO YUDEN CO., LTD.
Application year: 1990
Main classification: B05B15
IPC codes: B05B15, B05B7