Method for producing a light emitting element

Abstract: A light emitting element comprises a housing (34) formed by allowing respective first principal surfaces of a rectangular upper housing member (12) made of glass material and having a recess at a central portion on its first principal surface and a rectangular lower housing member (14) made of glass material and having a recess at a central portion on its first principal surface as well to make contact with each other so that they are thermally glued by press under a pressure in a predetermined atmosphere; a cavity (16) formed by the respective recesses (30, 32) in the housing (34) and enclosed with at least one of a gas and a light emitting substance; and two lead wires (18, 20) confronted with each other with the cavity (16) interposed therebetween. Accordingly, it is possible to simultaneously realize the integration and the miniaturization of the electronic tube and present the display expression for information transmission at a high brightness.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to a method for producing a light emitting element, including an electronic tube which utilizes the discharge light emission of at least one of a gas and a light emitting substance enclosed in a formed product made of, for example, a glass material. Description of the Related Art: In general, the light source, which utilizes the discharge light emission of at least one of the gas and the light emitting substance enclosed in a tube made of glass, includes electronic tubes such as mercury lamps, fluorescent tubes, sodium lamps, carbon arc lamps, zirconium discharge lamps, neon tubes, and flash discharge lamps. The electronic tube as described above is manufactured, for example, such that an anode bar is fused to one end of a cylindrical glass tube, and then a cathode bar is fused to the other end of the glass tube in a predetermined gas atmosphere (atmosphere containing the gas to be enclosed) to enclosed the predetermined gas in the glass tube. It is contemplated that such an electronic tube is utilized to display, for example, images and characters at the outdoor. In such a situation, it is conceived that a large number of electronic tubes are arranged so that the light is selectively emitted from the electronic tubes. However, the respective electronic tubes exist as single members. Therefore, when the large number of electronic tubes are arranged, the scale is inevitably large. As a result, problems arise in that the installation space is enlarged, the wiring operation is complicated, and the production cost becomes expensive. Under the circumstances, it is expected that the electronic tube itself is allowed to have a miniature size. However, if the electronic tube is miniaturized, then the distance between the anode and the cathode is decreased, and the pressure at the inside of the glass tube is further Increased during the light emission. Therefore, it is necessary to increase the strength of the glass tube in association with the miniaturization of the electronic tube. EP-A-0 581 376 describes a high pressure discharge lamp and a method for making the same utilizing integrated circuit techniques. This document further considers joining two substrates to form a cavity by anodic wafer bonding or fusion wafer bonding. SUMMARY OF THE INVENTION The present invention has been made taking the foregoing problems into consideration, an object of which is to provide a method for producing a light emitting element, in which it is possible to easily produce the light emitting element which makes it possible to simultaneously realize the integration and the miniaturization of the electronic tube and present the display expression for information transmission at a high brightness. According to the present invention, there is provided a method for producing a light emitting element, comprising forming at least two glass members from non-crystalline glass which, when confronted, form an enclosed cavity; confronting the glass members with each other and thermally gluing them under a pressure in a predetermined atmosphere to form the enclosed cavity; and applying a heat treatment to the joined glass members to cause crystallisation to form crystallised glass. The method producing a light emitting element comprising a cavity enclosed with at least one of a gas and a light emitter substance at its inside; and mutually confronting electrodes within the cavity. The electric power is applied to the electrodes which are opposed to one another with the cavity interposed therebetween. Thus, the discharge light emission is effected by at least one of the gas and the light emitter substance enclosed in the cavity. That is, one cavity functions as one electronic tube. Therefore, when a large number of electronic tubes are integrated with each other in order to make display for information transmission, it is convenient that a large number of cavities are integrated with each other. In the present invention, the cavity is formed by thermally gluing the glass members. Therefore, it is possible to integrate the large number of cavities at a high degree of integration. Accordingly, it is also possible to easily realize the miniaturization thereof. As described above, according to the light emitting element concerning the present invention, it is possible to simultaneously realize the integration and the miniaturization of the electronic tube and present the display expression for information transmission at a high brightness. In the arrangement described above, it is also preferable that the electrodes are constructed by lead wires fixed on a surface at which the glass members contact with each other. Alternatively, the electrodes may be constructed by thin films formed by printing on a surface at which the glass members contact with each other. Especially, when the electrodes are constructed by the thin films, then the labor for wiring arrangement can be eliminated, and it is possible to simplify the production steps. Further, the positioning can be easily performed in order to confront the electrodes with each other with the cavity interposed therebetween. In the arrangement described above, it is also preferable that the glass member to be used has a bending strength of not less than 1000 kgf/cm 2 . For example, in the case of the light emitting element in which argon, mercury or the like is enclosed in the cavity, the glass member having a bending strength of about 1000 kgf/cm 2 is used. In the case of the light emitting element in which the gas such as xenon capable of obtaining a high brightness is enclosed, the glass member having a bending strength of about 3000 kgf/cm 2 is preferably used. In general, in order to improve the resolution of the display expression, it is necessary to increase the number of cavities which function as electronic tubes. However, considering the miniaturization in such a situation, it is conceived that the respective cavities are reduced in size. If the size of the respective cavities is reduced, the pressure in the cavity is increased during the light emission in accordance therewith. However, when the glass member satisfies the condition for the bending strength as described above, the formed product is obtained, which is sufficiently capable of withstanding the pressure in the cavity. Thus, it is possible to avoid the inconvenience such as the light emission defect. It is also preferable that a glass member having a coefficient of thermal expansion which is substantially zero or which is near to a coefficient of thermal expansion of the electrode is used as the glass member. In this arrangement, the heat resistance is excellent, and the light emitting element is advantageous in resistance to the heat cycle relevant to the repetition of discharge light emission of at least one of the gas and the light emitting substance enclosed in the cavity. The thermal gluing here mentioned may be any suitable thermal bonding process, with or without intermediary bonding material, preferably without such bonding material. In the accompanying drawings light emitting elements formed by preferred embodiments of the present invention are shown by way of illustrative example. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a perspective view illustrating an arrangement of a light emitting element formed by a method embodying the present invention; Fig. 2 shows an exploded sectional view illustrating the arrangement of the light emitting element of Fig. 1; Fig. 3 shows a longitudinal sectional view illustrating the arrangement of the light emitting element of Fig. 1; Fig. 4 illustrates an exemplary method for fixing the lead wire on the contact surface of the housing member; Fig. 5 illustrates another exemplary method for fixing the lead wire on the contact surface of the housing member; Fig. 6 illustrates still another exemplary method for fixing the lead wire on the contact surface of the housing member; Fig. 7 shows a longitudinal sectional view illustrating a first modified light emitting element formed by a method embodying the present invention; FIG. 8 shows a longitudinal sectional view illustrating a second modified light emitting element formed by a method embodying the present invention; FIG. 9 shows a block diagram depicting steps of a method of the invention for producing a light emitting element; FIG. 10 shows a characteristic curve illustrating the forming temperature for the glass member and the elongation percentage of the glass member; FIG. 11 shows a graph illustrating a time schedule for the heat treatment performed to cause crystallization; FIG. 12 shows a perspective view illustrating an arrangement of a second light emitting element formed by a method embodying the present invention; FIG. 13 shows an exploded sectional view illustrating the arrangement of the second light emitting element according to Fig. 12; FIG. 14 shows a longitudinal sectional view illustrating the arrangement of the second light emitting element according to fig.12; FIG. 15 shows a longitudinal sectional view illustrating a modified second light emitting element formed by a method embodying the present invention; FIG. 16 shows a sectional view taken along a line XVI-XVI shown in FIG. 15; FIG. 17 shows a longitudinal sectional view illustrating a modified second light emitting element formed by a method embodying the present invention; FIG. 18 shows a sectional view taken along a line XVIII-XVIII shown in FIG. 17; FIG. 19 shows a longitudinal sectional view illustrating a modified second light emitting element formed by a method embodying the present invention; FIG. 20 illustrates an exemplary procedure for forming the thin film on the contact surface of the housing member; FIG. 21 illustrates another exemplary procedure for forming the thin film on the contact surface of the housing member; and FIG. 22 illustrates still another exemplary procedure for forming the thin film on the contact surface of the housing member. DESCRIPTION OF THE PREFERRED EMBODIMENTS Explanation will be made below with reference to FIGS. 1 to 22 for several illustrative embodiments of the method according to the present invention for producing a light emitting element. Description of the light emitting elements themselves is included to give a clearer understanding of the methods embodied in the present invention. At first, as shown in FIG. 1, a light emitting element 10A comprises a cavity 16 which is formed such that respective first principal surfaces of a rectangular upper housing member 12 and a rectangular lower housing member 14 made of a glass material are allowed to make contact with each other to thermally glue them by press under a pressure in a predetermined atmosphere, the cavity 16 including at least one of a gas and a light emitting substance enclosed therein, and two lead wires 18, 20 provided for the cavity 16 interposed therebetween. The lead wires 18, 20 constitute an anode and a cathode respectively. Specifically, as shown in FIG. 2, the upper housing member 12 has, for example, a rectangular recess 30 which is formed at the central portion of its first principal surface 12a. The lower housing member 14 also has, for example, a rectangular recess 32 which is formed at the central portion of its first principal surface. Therefore, the surfaces other than the recesses 30, 32 of the respective first principal surfaces 12a, 14a of the upper housing member 12 and the lower housing member 14 function as contact surfaces 12a, 14a respectively. The upper housing member 12 and the lower housing member 14 are allowed to make contact with each other while confronting the first principal surfaces 12a, 14a with each other to thermally glue them by press under a pressure in a predetermined atmosphere. Thus, a housing 34 (formed product) is manufactured, which has the cavity 16 formed by the recesses 30, 32 at the inside. Before the upper housing member 12 and the lower housing member 14 are allowed to make contact with each other with the first principal surfaces 12a, 14a confronting with each other, for example, the two lead wires 18, 20 are fixed with their respective end surfaces exposed to the recesses 32 on the contact surface 14a of the lower housing member 14. Accordingly, when the upper housing member 12 and the lower housing member 14 are thermally glued by press under the pressure with each other, the anode and the cathode, which are formed by the lead wires 18, 20 respectively, are confronted with each other with the cavity 16 interposed therebetween. In this light emitting element, in order to ensure the discharge light emission in the cavity 16, it is more preferable to allow the respective ends of the lead wires 18, 20 to protrude into the cavity 16. The method for wiring and fixing the lead wires 18, 20 on the contact surface 14a of the lower housing member 14 includes, for example, a method in which the lead wires 18, 20 are fixed by the aid of a paste 40 made of a glass material applied to the contact surface 14a as shown in FIG. 4, a method in which grooves 42 for lead wires extending from the outer surface to the recess 32 are previously formed on the contact surface 14a, and the lead wires 18, 20 are arranged and fixed in the grooves 42 respectively as shown in FIG. 5, and a method in which the paste 40 made of the glass material is applied to the grooves 42, and the lead wires 18, 20 are fixed in the grooves 42 as shown in FIG. 6. The glass material paste 40 is preferably a paste having the same composition as that of the glass material for constructing the housing 34, for example, in view of the thermal expansion. More preferably, in order to improve the operability, the melting point of the glass is slightly lowered. When the glass material paste 40 is used, it is preferable that the glass material paste 40 is also applied to the contact surface 12a of the upper housing member 12. In this light emitting element, crystallized glass is used as the glass material for constructing the upper housing member 12 and the lower housing member 14. Specifically, this method of forming a light emitting element uses a glass material having its trade name of "Miraclon" (registered trademark) produced by NGK Insulators, Ltd. Miraclon (registered trademark) includes glass ceramic products (Miraclon PP and Miraclon PH) and a chemical strengthening glass product (Miraclon PC). The glass ceramic product is obtained such that a blended preparation having a specified composition is melted and glassified at a high temperature, which is formed in the same manner as in the ordinary glass production method, followed by a heat treatment under a specified condition to make conversion into an aggregate composed of a large number of uniform mtcrocrystals. The chemical strengthening glass product is obtained such that the glass surface layer is subjected to ion exchange. The characteristics will now be briefly explained for the crystallized glass specified by Miraclon (registered trademark). At first, Miraclon PP is obtained by depositing, in glass, about 1 µm of microcrystals of lithium disilicate (Li 2 O·2SiO 2 ) and β-spodumene (Li 2 O·Al 2 O 3 ·4SiO 2 ), and it has the following features. That is, the appearance is white and opaque. Especially, the bending strength is 3500 kgf/cm 2 which is extremely strong and which is not less than three times those of the glass and the porcelain. Miraclon PH-1 is obtained by depositing, in glass, about 1 µm of microcrystals of β-spodumene (Li 2 O · Al 2 O 3 · 4SiO 2 ), and it has the following features. That is, the appearance is white and opaque. The coefficient of thermal expansion is about 11 × 10 -7 /°C which is small. Miraclon PH-1 is strong against heat shock. Miraclon PH-3 is obtained by depositing, in glass, about 1 µm of β-quartz type microcrystals (Li 2 O· Al 2 O 3 · 2SiO 2 ), and it has the following features. That is, the appearance is colorless and transparent. The coefficient of thermal expansion is substantially zero. Therefore, Miraclon PH-3 is extremely strong against heat shock. Miraclon PH-3 is not broken even when it is red-heated to 800 °C followed by introduction into water at 0 °C. Miraclon PC is chemical strengthening glass obtained by ion exchange of Li + ←→ Na + for the glass surface layer, and it has the following feature. Especially, the bending strength is 5200 kgf/cm 2 which is extremely strong. As described above, in the light emitting element 10A , the cavity 16, in which at least one of the gas and the light emitting substance is enclosed, is formed in the housing 34 manufactured such that the upper housing member 12 and the lower housing member 14 composed of the glass material are thermally glued by press under the pressure. The electric power is applied to the anode and the cathode (lead wires 18, 20) confronting with each other with the cavity 16 interposed therebetween. Thus, the discharge light emission is effected by at least one of the gas and the light emitting substance enclosed in the cavity 16. That is, one cavity 16 functions as one electronic tube. Therefore, when the display expression is made for the purpose of information transmission, if a large number of electronic tubes are integrated with each other, then a large number of recesses 30, 32 are formed in the upper housing member 12 and the lower housing member 14, and a large number of cavities 16 are integrated with each other, which are formed by thermally gluing the upper housing member 12 and the lower housing member 14 by press under the pressure to produce the housing 34. In these light emitting elements, the cavities 16 are formed by the thermal adhesion of the glass members under the pressure. Accordingly, it is possible to integrate the large number of cavities 16 at a high degree of integration, in accordance with which it is also possible to easily realize the miniaturization thereof. As described above, according to the light emitting element 10A , it is possible to simultaneously realize the integration and the miniaturization of the electronic tube, and it is possible to present the display expression for information transmission at a high brightness. Further, it is also contemplated to make application to color display. Especially, the light emitting element 10A uses the glass material having the bending strength of not less than 1000 kgf/cm 2 as the glass material for constructing the upper housing member 12 and the lower housing member 14. Therefore, it is possible to obtain the following effects. That is, in order to improve the resolution of the display expression, it is necessary to increase the number of cavities 16 which function as electronic tubes. However, considering the miniaturization, it is conceived that the respective cavities 16 are reduced in size. If the size of the respective cavities 16 is reduced, the pressure in the cavity 16 is increased during the light emission in accordance therewith. However, when the glass member satisfies the bending strength as described above, the formed product (housing 34) is obtained, which is sufficiently capable of withstanding the pressure in the cavity 16. Thus, it is possible to avoid the inconvenience such as the light emission defect. The glass material having a bending strength of about 1000 kgf/cm 2 is used for the light emitting element in which, for example, argon or mercury is enclosed in the cavity. The glass material having a bending strength of about 3000 kgf/cm 2 is preferably used for the light emitting element in which the gas such as xenon to obtain a high brightness is enclosed in the cavity. The light emitting element 10A is allowed to use the glass material in which the coefficient of thermal expansion is substantially zero, or it is near to the coefficient of thermal expansion of the electrode. In this arrangement, the heat resistance is excellent, and the light emitting element 10A is advantageous in resistance to the heat cycle relevant to the repetition of discharge light emission of at least one of the gas and the light emitting substance enclosed in the cavity 16. Next, several modified light emitting elements will be explained with reference to FIGS. 7 and 8. At first, as shown in FIG. 7, a light emitting element 10Aa comprises a recess 32 provided on only the lower housing member 14. In this case, the cavity 16 is formed by the recess 32 and the first principal surface 12a of the upper housing member 12. Next, as shown in FIG. 8, a light emitting element 10Ab comprises a recess 30 provided on only the upper housing member 12. In this case, the cavity 16 is formed by the recess 30 and the first principal surface 14a of the lower housing member 14. The light emitting elements 10Aa and 10Ab also make it possible to obtain the same effect as that obtained by the light emitting element 10A described above. Next, a method for producing the light emitting element 10A will be explained with reference to a flow chart shown in FIG. 9. At first, in the step S1, various composition components are blended in order to obtain the desired crystallized glass. For example, when Miraclon PP-4 is obtained, the blending is carried out to give 79 % by weight of SiO 2 , 6.0 % by weight of Al 2 O 3 , 12.5 % by weight of Li 2 O, 2.5 % by weight of K 2 O, 3.0 % by weight of P 2 O 5 , and 0.3 % by weight of As 2 O 3 . When Miraclon PH-3 is obtained, the blending is carried out to give 65.7 % by weight of SiO 2 , 22.7 % by weight of Al 2 O 3 , 4.2 % by weight of Li 2 O, 0.5 % by weight of Na 2 O, 0.3 % by weight of K 2 O, 1.4 % by weight of P 2 O 5 , 0.5 % by weight of MgO, 1.7 % by weight of TiO, 0.9 % by weight of As 2 O 3 , 2.4 % by weight of ZrO 2 , and 0.2 % by weight of Sb 2 O 3 . When Miraclon PC-4 is obtained, the blending is carried out to give 62.9 % by weight of SiO 2 , 17.2 % by weight of Al 2 O 3 , 3.5 % by weight of Li 2 O, 5.8 % by weight of Na 2 O, 1.9 % by weight of CaF 2 , 1.0 % by weight of TiO, 7.7 % by weight of B 2 O 3 , and 0.3 % by weight of As 2 O 3 . Subsequently, in the step S2, the blended preparation is heated and melted at a temperature of 1400 to 1500 °C. Subsequently, in the step S3, the melted blended preparation is quenched and quickly cooled with water, oil or the like without causing crystallization in the same manner as in the ordinary glass production method. After that, in the step S4, the cooled blended preparation is processed to have a plate-shaped configuration to prepare a source plate for the upper housing member 12 and the lower housing member 14. Subsequently, in the step S5, the source plate is press-formed to produce the upper housing member 12 having the recess 30 at the central portion of the first principal surface 12a and the lower housing member 14 having the recess 32 at the central portion of the first principal surface 14a. The press forming is performed at a temperature of not less than a softening point Ts of the source plate. The softening point Ts is a temperature at which the viscosity of the source plate is 4.5 × 10 7 poise. In this embodiment, as shown in FIG. 10, for example, the process is carried out at a temperature which is higher by about 40 °C to 50 °C than the yield temperature T D at which the elongation percentage is maximum. T G in FIG. 10 represents the temperature at which the melted glass begins to be solidified, i.e., the transition temperature. Subsequently, in the step S6 shown in FIG. 9, the upper housing member 12 and the lower housing member 14, which have been manufactured by the press forming described above, are cooled, for example, to the room temperature. After that, in the step S7, the lead wires 18, 20 are wired and fixed, for example, on the contact surface 14a of the lower housing member 14. As described above, the method for fixing the lead wires 18, 20 includes, for example, a method in which the lead wires 18, 20 are fixed by the aid of the paste 40 made of the glass material applied to the contact surface 14a (see FIG. 4), a method in which the grooves 42 for the lead wires extending from the outer surface to the recess 32 are previously formed on the contact surface 14a, and the lead wires 18, 20 are arranged and fixed in the grooves 42 respectively (see FIG. 5), and a method in which the paste 40 made of the glass material is applied to the grooves 42, and the lead wires 18, 20 are fixed in the grooves 42 respectively (see FIG. 6). Subsequently, in the step S8, the upper housing member 12 and the lower housing member 14 are allowed to make contact with each other with their first principal surfaces (contact surfaces) 12a, 14a opposing to one another to thermally glue them by press under a pressure in a predetermined atmosphere, for example, a xenon atmosphere at a high pressure (1 to 20 atms). Thus, the housing 34 is manufactured, which includes, at its inside, the cavity 16 formed by the recesses 30, 32. The press thermal gluing process under the pressure is also performed at a temperature which is higher by about 40 °C to 50 °C than the yield temperature T D , in the same manner as in the press forming performed in the step S5. Subsequently, in the step S9, the heat treatment is performed in order that the crystalline nucleuses are generated in the manufactured housing 34 to cause crystallization. An example of the heat treatment will be explained. As shown in FIG. 11, the temperature is raised from the room temperature to the primary crystallization temperature t1 at a temperature-raising speed of 50 °C to 200 °C / hour, followed by being held for a certain period of time T1. Accordingly, the crystalline nucleuses are formed in the housing 34. After that, the temperature is raised to the secondary crystallization temperature t2 at a temperature-raising speed of 50 °C to 200 °C / hour, followed by being held for a certain period of time T2. Accordingly, the crystals grow in the housing 34. Subsequently, the temperature is lowered to the room temperature at a temperature-lowering speed of, for example, 50 °C to 200 °C / hour. The application of the heat treatment for the purpose of crystallization as described above allows the housing 34 to be converted into an aggregate of a large number of uniform microcrystals. As a result, it is possible to obtain the high bending strength which is not less than three times that of the glass. Next, a light emitting element 10B will be explained with reference to FIGS. 12 to 19. Components or parts corresponding to those shown in FIGS. 1 to 3 are designated by the same reference numerals, duplicate explanation of which will be omitted. As shown in FIGS. 12 to 14, the light emitting element 10B is constructed in approximately the same manner as the light emitting element 10A described above (see FIG. 1). However, the former is different from the latter in that the anode and the cathode are not constructed by the lead wires 18, 20, but the anode and the cathode are constructed by thin films 50, 52 containing metal. Especially, in the light emitting element 10B, in order to facilitate the connection to an unillustrated interface circuit, the respective thin films 50, 52 for constructing the anode and the cathode are formed over the contact surface 14a to the outer circumferential surface of the lower housing member 14. The method for forming the thin films 50, 52 on the contact surface 14a of the lower housing member 14 includes, for example, a method in which they are formed by printing a paste based on the use of a glass powder and a high melting point metal (for example, tungsten and molybdenum), and a method in which they are formed by using a sheet member comprising a metal foil formed on, for example, a film-shaped resin strip to stick the metal foil of the sheet member, for example, to the contact surface 14a of the lower housing member 14, followed by peeling off the resin strip other than the metal foil. Also in the light emitting element 10B, it is possible to simultaneously realize the integration and the miniaturization of the electronic tube, and it is possible to make the display expression for information transmission at a high brightness, in the same manner as in the light emitting element 10A. Especially, in the light emitting element 10B , the anode and the cathode are constructed by using the thin films 50, 52. Therefore, the labor for the wiring arrangement is reduced, and it is possible to simplify the production steps, as compared with the case in which the anode and the cathode are constructed by using the lead wires 18, 20. Further, the positioning can be easily achieved in order that the anode and the cathode are opposed to one another with the cavity 16 interposed therebetween. Next, several modified light emitting elements based on light emitting element 10B will be explained with reference to FIGS. 15 to 19. At first, as shown in FIG. 15, a light emitting element 10Ba differs in that the recess 32 is provided on only the lower housing member 14, and the anode and the cathode are formed by the thin films 50, 52 on the first principal surface 12a of the upper housing member 12. In this case, as shown in FIG. 16, the cavity 16 is formed by the recess 32 and the first principal surface 12a of the upper housing member 12. Especially, forward ends of the thin films 50, 52 for constructing the anode and the cathode may be formed to have a sharp configuration. This arrangement is more preferred in that the discharge efficiency is improved. Next, as shown in FIG. 17, a light emitting element 10Bb differs in that the recess 30 is provided on only the upper housing member 12, and the anode and the cathode are formed by the thin films 50, 52 on the first principal surface 14a of the lower housing member 14. Also as shown in FIG. 18, the cavity 16 is formed by the recess 30 and the first principal surface 14a of the lower housing member 14. Especially, forward ends of the thin films 50, 52 for constructing the anode and the cathode may be formed to have a sharp configuration. This arrangement is more preferred in that the discharge efficiency is improved. Next, as shown in FIG. 19, a light emitting element 10Bc differs in that a tapered surface 32a is formed at the circumferential edge of the recess 32 of the housing member (the lower housing member 14 in Fig. 19) on which the anode and the cathode based on the thin films 50, 52 are not formed, of the upper housing member 12 and the lower housing member 14. In this light emitting element, it is possible to avoid the inconvenience which would otherwise occur such that the glass component of the lower housing member 14 covers the forward ends of the anode and the cathode constructed by the thin films 50, 52, during the discharge light emission. Thus, it is possible to contemplate the reliability of the discharge light emission. Next, a method for producing the light emitting element 10B will be explained. This production method is carried out by executing approximately the same steps as those of the method for producing the light emitting element 10A shown in FIG. 9. However, the former is different from the latter in that the anode and the cathode of the thin films 50, 52 are formed in the electrode formation in the step S7 not by arranging the lead wires 18, 20 but by adopting, for example, the method based on the printing or the method based on the use of the sheet member as described above. In this embodiment of the present invention, it is possible to adopt, for example, a method in which the electrodes (the anode and the cathode) based on the thin films 50, 52 are formed, for example, by means of printing by the aid of a paste 40 made of glass material applied to the contact surface 14a of the lower housing member 14 as shown in FIG. 20, a method in which a groove 54 for the electrode extending from the outer surface to the recess 32 is previously formed, for example, on the contact surface 14a of the lower housing member 14 so that the anode and the cathode based on the thin films 50, 52 are formed in the groove 54 as shown in FIG. 21, and a method in which the paste 40 made of glass material is applied to the groove 54 and then the anode and the cathode based on the thin films 50, 52 are formed as shown in FIG. 22. The glass material paste 40 is preferably a paste having the same composition as that of the glass material for constructing the housing 34, for example, in view of the thermal expansion. When the glass material paste 40 is used, it is preferable that the glass material paste 40 is also applied to the contact surface 12a of the upper housing member 12. In the light emitting elements 10A and 10B described above (including the light emitting elements concerning the various modified light emitting elements ), the upper housing member 12 and the lower housing member 14, each of which has the plate-shaped configuration, are joined to one another by means of the thermal adhesion by press under the pressure to produce the plate-shaped housing 34. Alternatively, hemispherical housing members may be joined to produce a spherical housing. The shape of the housing 16 is not especially limited. The xenon gas is used as the gas to be enclosed in the cavity 16 of the housing 34. Alternatively, it is possible to use other gases such as mercury and argon.

Claims: A method of forming a light emitting element comprising: an enclosed cavity (16) with at least one of a gas and a light emitter substance inside; and mutually confronting electrodes (18, 20) within said cavity, wherein said method comprises: forming at least two glass members (12, 14) from non-crystalline glass which, when confronted, form said enclosed cavity (16); confronting said glass members (12, 14) with each other and thermally gluing said glass members (12, 14) under a pressure in a predetermined atmosphere to form said enclosed cavity (16); and applying a heat treatment to the joined glass members (12, 14) to cause crystallisation to form crystallised glass. A method of forming a light emitting element according to claim 1 wherein said mutually confronting electrodes are provided on a contact surface of at least one of said glass members (12, 14). A method of forming a light emitting element according to claim 1 or 2, wherein said electrodes (18, 20) are constructed by fixing lead wires on a surface at which said glass members (12, 14) contact with each other. A method of forming a light emitting element according to claim 1 or 2, wherein said electrodes (18, 20) are formed by printing thin films on a surface at which said glass members (12, 14) contact with each other. A method of forming a light emitting element according to any one of the preceding claims, wherein said glass member (12, 14) has a bending strength of not less than 1000 kgf/cm 2 . A method of forming a light emitting element according to any one of the preceding claims, wherein a glass member having a coefficient of thermal expansion which is substantially zero or which is near to a coefficient of thermal expansion of said electrode (18, 20) is used as said glass member (12, 14).

Inventors: ASAI MICHIO, NIIMI NORIKAZU, ASAI, MICHIO, NIIMI, NORIKAZU, Niimi, Norikazu, Grande Maison Kachigawa 304,65
Applicants: NGK INSULATORS LTD, NGK INSULATORS, LTD.
Application year: 1999
Main classification: H01J9
IPC codes: H01J17, H01J9, H01J61, C03B23