JPH08511652A - Phosphor coating structure for electrodeless discharge lamp - Google Patents

Abstract

(57) [Summary] An electrodeless discharge lamp (10) having a lamp bulb (12) filled with mercury and a rare gas is excited to a discharge state by introducing RF energy in the vicinity thereof. A ballast circuit housed within the lamp housing base (22) produces RF energy from a conventional line power source. The ballast circuit has a core that projects into a recessed cavity (16) formed in the lamp bulb. During operation of the lamp, the recessed cavity is exposed to higher wall heat load conditions than the outer surface of the lamp bulb. These high wall heat load conditions require the rare earth phosphor 30 to be more expensive than the conventional halophosphate phosphor 32 used in the outer portion of the lamp bulb. In a single lamp bulb shape and at a reasonable cost, the recessed cavity and outer coating operations are performed individually to apply two phosphor coatings, and then the two elements are integrated. Joined to form a finished lamp bulb. The juncture between the recessed cavity and the outer bulb is located below the upper rim of the housing and is therefore invisible in the final lamp product.

Description

Description: TECHNICAL FIELD The present invention relates to a structure of a phosphor coating applied to a bulb portion of an electrodeless discharge lamp. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a phosphor coating, and more particularly to a phosphor coating structure intended to solve the difference in wall heat loading characteristics existing in an electrodeless discharge lamp. BACKGROUND OF THE INVENTION It is noted that electrodeless discharge lamps contribute significantly to the realization of electrical configurations that reduce power requirements, thereby avoiding the construction of power plants with high operating costs. The attributes of electrodeless discharge lamps are derived from the improved energy efficiency of such devices, and long life is expected due to the elimination of electrode elements that shorten the life. An example of an electrodeless discharge lamp is disclosed in US Pat. No. 4,010, which discloses that an ionized medium is contained in a lamp bulb and an RF signal is introduced so as to be close to the ionized medium to form a discharge state. It can be found in No. 400. With the use of suitable phosphors, visible light is generated by such discharge. In order to generate this RF signal, the electrodeless discharge lamp has a stable circuit structure arranged in the lamp base, and such a stable circuit structure ionizes the RF signal by plunging the coil member into the lamp bulb. Inductively coupled to the medium. As with some conventional fluorescent lamps, electrodeless discharge lamps require a phosphor layer to convert the discharge from the ionized medium into visible light. A typical practice in the fluorescent lamp manufacturing process is to use a halophosphate phosphor and either mix the phosphate into it or add a relatively small amount of it to obtain the final color required. You can Halophosphate phosphors are widely used because of their relative low cost, their favorable efficiency, low cost, and wide color latitude. However, in small fluorescent lamp applications, the use of halophosphate phosphors is unsuitable because of the high number of wall heat load characteristics typically formed. This is because these materials tend to deteriorate rapidly under high wall heat load conditions. In such cases, it is usually necessary to use more expensive rare earth phosphors. In the electrodeless discharge lamp, the wall heat load characteristics change depending on the different lamp bulbs, but the heat load characteristics described above are sufficient in the vicinity of the cavity surrounding the coil member where the RF signal is inductively coupled. It raises the road and blocks the use of halophosphate phosphors in such areas. One way to mitigate the degradation of the phosphor by using a halophosphate phosphor is to cover the entire inside surface of the lamp bulb with a rare earth phosphor. While such a feature results in a longer life of the light source, the cost of the lamp is significantly increased by using a relatively expensive rare earth phosphor. Another way to alleviate this problem is to mask certain positions of the inner wall of the lamp bulb and perform a separate deposition process at each location where different phosphors should be used. Such an arrangement is generally costly due to the expensive manufacturing steps required for masking and multi-coating. Therefore, the phosphor coating structure has a cost effect as a result of using different phosphors (using expensive rare earths only where needed) based on wall heat load requirements, such as masking and multiple coating steps. It is desirable to provide an electrodeless discharge lamp without adding such various processes. SUMMARY OF THE INVENTION An electrodeless discharge lamp constructed in accordance with the principles of the present invention has a lamp bulb containing a mercury fill and a noble gas, the noble gas being generated by a ballast circuit located in the lamp base. It has a lamp bulb adapted to be excited to a discharge state by the introduction of an RF signal. The lamp bulb is arranged so as to at least partially surround the coil member, and an RF signal is generated from the coil member. The phosphor coating structure on the lamp bulb is effectively formed at low cost and can be easily instrumented for mass production processes. The outer portion of the lamp bulb is spaced apart with respect to the coil member, while the inner cavity projects into the lamp bulb along its central axis. The inner cavity along this central axis is dimensioned to receive the coil member inserted therein and to provide a higher wall heat load on the inner cavity adjacent the coil member than on the outer portion of the lamp bulb. To be decided The joining area of the lamp bulb is formed by joining the inner cavity portion to the outer portion of the lamp bulb at the lowermost portion of the lamp bulb. The lowermost part of the lamp bulb is inserted on the lamp base in order to hold the lamp bulb on the lamp base. The rare earth phosphor coating is applied to the inner cavity, while either the halophosphate phosphor or the fluorescent phosphate material is applied to the inner surface of the outer portion of the lamp bulb. The manufacturing process for joining the inner cavity to the outer part of the lamp bulb is carried out after the phosphor coating has been applied, thus eliminating the need for masking operations in the coating process. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in more detail with reference to the accompanying drawings. FIG. 1 is a side sectional view of an electrodeless lamp constructed in accordance with the present invention. FIG. 2 is an enlarged side sectional view showing the lamp bulb portion of FIG. 1 for showing the phosphor coating structure of the present invention. DETAILED DESCRIPTION OF THE INVENTION As shown in FIG. 1, a low pressure electrodeless fluorescent lamp 10 comprises a lamp bulb 12 having an outer bulb portion 14 and an inner cavity portion shown as a recessed (reentrant) cavity portion 16. ing. The recessed cavity portion 16 is basically circular in shape and projects into the outer bulb portion 14 along the central axis thereof. An exhaust gas sealing tube 18 is provided along the central axis of the recessed cavity portion 16, and the exhaust gas sealing tube 18 is formed by joining the recessed cavity portion 16 and the outer bulb portion 14 to each other. Is completed, that is, a portion projecting downward beyond the joining point indicated by 20 in the figure. The outer bulb portion 14 basically has the same shape as a finished product of a conventional incandescent reflector lamp. However, other shapes for the outer lamp bulb 14 can be employed. For example, the outer bulb 14 may have a shape similar to that of a well-known A-line type lamp or a decorative globe lamp. Irrespective of the shape of the outer bulb portion 14, the lower regions 14a and 14b that face each other in the outer bulb portion and the recessed cavity of the lamp bulb 12 and are ultimately integrated at the joint 20 are: It will be located inside the upper rim area of the base housing 22. As will be described later in detail, in this respect, by disposing the joint portion 20, the fluorescent substance can be coated with the strictness somewhat relaxed. Further, by adopting a lamp manufacturing method in which the outer bulb portion 14 is formed separately from the step of forming the recessed cavity portion 16, the phosphor coating is formed by joining these two parts in the final finishing step of the lamp. It can be done individually for each part before being processed. According to the present invention, in this aspect, the formation of the phosphor coating on the outer bulb portion 14 can be performed separately from the application to the recessed cavity wall, whereby other portions are coated with different fluorescent substances. In this case, it is not necessary to mask the relevant part. As further shown in FIG. 1, the electrodeless discharge lamp 10 of the present invention produces a toroidal discharge phase 23 in the lamp bulb 12. Such a discharge phase 23 is generated by introducing radio frequency (RF) energy into the filling contained in the lamp bulb. In this case, as the filling material, a conventionally known substance used for a standard fluorescent lamp is used. RF energy is generated by the resonant circuit portion of ballast circuit 24 located within housing base 22. This resonance circuit section is composed of an excitation coil 26 having a winding section 26a and a core section 26b, and a capacitor 28. This stabilizing circuit excites the resonance circuit section by the condition signal converted from the line power supply. Due to the excitation generation and maintenance of the discharge phase 23 in the lamp bulb 12, the recessed cavity 16 of the lamp bulb 12 has a higher wall heat load value (W / cm ² ) than the outer bulb portion 14. . In order to prevent the phosphor coating applied to the wall surface of the recessed cavity 16 from shortening the actual life of the electrodeless discharge lamp 10, which is expected to have a long life, this region is made of triphosphate. It is necessary to use a phosphor coating of As shown in FIG. 2, the triphosphate phosphor coating 30 is applied on the wall surface of the recessed cavity 16 facing the inner space outside the lamp bulb 12. The triphosphate phosphor coating 30 can typically use materials for ordinary small fluorescent lamps that are readily available on the market. Unlike the wall heat load conditions that the recessed cavity 16 suffers, the outer bulb portion 14 of the lamp bulb 12 has a very low such heat load and it is possible to use a relatively inexpensive halophosphate material. it can. This material is a fluorescent material similar to that which has been used for relatively large fluorescent lamps of 2 or 4 feet type. As shown in FIG. 2, the different phosphors 32 are shown as having a different particle size than the phosphors 30 used in the recessed cavities. Further, as shown in FIG. 2, the lamp 10 is a reflector lamp, and has a light-reflecting coating 34 in the lower half portion extending to the maximum diameter portion of the lamp bulb on the wall surface of the recessed cavity portion 16. The maximum diameter portion is indicated by a dividing line (two-dot chain line) indicated by line AA. In the coating step for forming the phosphor coating on the wall surface of the outer bulb portion 14 of the lamp bulb 12 and the wall surface of the recessed cavity portion 16, the recessed cavity portion 16 and the outer bulb portion 14 are joined together. Rigidity is not required for the portion of the lamp bulb 12. In effect, the joint 20 is not visible in the final product and is covered by the upper rim of the housing base 22. Further, in the processing step applied to the lamp bulb 12 having the phosphor coating as the final product assembled to the housing portion 22 and the stabilizing circuit portion 24, each of the outer bulb portion 14 and the cavity portion 16 is individually coated. It will be appreciated that it is simplified by the fact that it is carried out without the need for a masking step to apply the material. After such an individual coating process is completed, the outer bulb portion 14 and the recessed cavity portion 16 are joined to form the final lamp bulb, thereby allowing the expensive triphosphate material to be removed from the wall. It is possible to achieve a relatively inexpensive device structure that is used only in a region required depending on the heat load characteristics. Although the embodiments described above are preferred embodiments of the present invention, various modifications may be made to these embodiments without departing from the scope of the present invention as long as they come within the scope of the appended claims. It is possible.

Claims (1)

[Claims] 1. It is released by introducing an RF signal generated by a stabilizing circuit arranged in the base part. Electrodeless discharge lamp with a lamp bulb filled with mercury and a noble gas excited to an electric state The lamp bulb, at least part of which is a coil member for generating an RF signal. And a phosphor coating on the lamp bulb. Which is formed, the electrodeless discharge lamp,     An outer portion of the lamp bulb located away from the coil member,     Projects into the lamp bulb along its central axis and supports the coil member An inner cavity dimensioned such that the outer portion of the lamp bulb is The part that is governed by the wall heat load condition higher than the incurred value,     Joining of the lamp bulb that connects the inner cavity to the outer portion of the lamp bulb Area and     A rare earth phosphor coating applied to the inner cavity of the lamp bulb, and     Halophosphate and phosphate material applied to the inner surface of the outer portion of the lamp bulb Electrodeless discharge lamp having a phosphor coating consisting of at least one . 2. In the manufacture of the electrodeless discharge lamp, the rare earth phosphor coating is used for the inner space. It is applied to the wall of the sinus and at least the halophosphate and phosphate phosphors On the one hand, the inner cavity is joined to the connection area on the outer part of the lamp bulb. It was previously applied to the outside of the lamp bulb, which allows the phosphor coating to During the formation of the membrane on any surface area of the lamp bulb any other surface A lamp as claimed in claim 1, characterized in that the need for masking the surface area is eliminated. Phosphor coating structure in tube. 3. The joining while the inner cavity portion and the outer portion of the lamp bulb are joined The region forms a connection point in the vertical section, and the connection point is an upper portion of the lamp base. It is arranged in the lamp base so as to be covered by the lamp section. The phosphor coating structure in the lamp bulb according to claim 2.