JP2007299614A - Cold cathode discharge lamp and lighting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode discharge lamp P for reducing the temperature of a sealing section in lighting and enhancing the sealing properties between a valve 1 and a sealing material 2, and to provide a lighting system 11. <P>SOLUTION: The cold cathode discharge lamp comprises: the valve 1 having a sealing section at both edges; a pair of discharge electrodes 5 sealed into the valve 1; and a sealing material 2 that supports the discharge electrode 5 at one edge side, allows the middle to be sealed to the sealing section and allows the other edge side to be led to the outside of the valve while at least the middle has a main constituent of at least one type of molybdenum and tungsten and a copper layer is formed on an outer surface by 1-10 μm. The sealing properties of the edge of the valve 1 are enhanced by a copper layer 2a formed on the outer-periphery surface. Also, the wetting properties of the sealing material 2 are improved, thus improving the welding strength between the discharge electrode 5 and an external lead wire 4, and the sealing material 2. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cold cathode discharge lamp having improved adhesion at a sealing portion and an illumination device using the cold cathode discharge lamp.

  In recent years, miniaturization of personal computers and televisions using liquid crystal display devices (hereinafter abbreviated as “LCD”) has been made thinner and higher in luminance. As a fluorescent lamp used in the backlight device for LCD, a cold cathode discharge lamp which is easy to downsize and has excellent life characteristics is often used.

  Since the cold cathode discharge lamp has a cold cathode electrode, it is possible to reduce the bulb diameter, and an extremely small lamp having an bulb inner diameter of 12 mm or less, for example, 5 mm or less has been developed. Usually, since the discharge electrode of the cold cathode discharge lamp is consumed by sputtering, when a certain size is required but molybdenum having sputtering resistance is used as the electrode, the electrode can be designed small. In addition, when the discharge electrode is formed of a metal having a small work function such as molybdenum or tungsten, power consumption required for light emission is reduced. For these reasons, there is an increasing demand for high-efficiency, long-life electrodes using refractory metals such as molybdenum and tungsten that have sputtering resistance and a low work function.

The electrode member of the cold cathode discharge lamp includes a discharge electrode, a sealing material whose one end is welded to the base end side thereof, and an external lead wire welded to the end face on the other end side of the sealing material. The electrode is sealed by inserting an electrode member into the bulb from the bulb end and sealing the sealing material to the bulb end. By the way, in recent years, cold cathode discharge lamps have become smaller and have higher output, and conventional discharge lamps that use bulbs made of soft glass as arc tubes ensure mechanical strength against smaller and higher output. Can not do it. Therefore, a means for configuring the bulb with hard glass such as borosilicate glass has been adopted. Cold cathode discharge lamps using hard glass have the advantage that heat resistance and mechanical strength are increased, and miniaturization and high output can be achieved. In this case, a sealing material made of a metal or an alloy having a thermal expansion coefficient similar to that of hard glass such as Kovar is used. On the other hand, with further miniaturization and higher output of the cold cathode discharge lamp, the electrode temperature at the time of lighting the lamp is increased, and the temperature of the sealing portion is also increasing. Therefore, the thermal conductivity of the sealing material conventionally formed of Kovar etc. is large, and the thermal expansion coefficient is similar to hard glass. Problems are prevented (see, for example, Patent Document 1).
JP 2003-142026 A

  However, in order to cope with higher output, it is necessary to further improve the adhesion between the arc tube and the sealing material. Molybdenum and tungsten used in the above-described conventional sealing materials have almost no diffusion into the glass, so there is room for improvement in order to improve the adhesion between the glass and the sealing material.

  The present invention has been made in view of the above problems, and has a cold cathode discharge lamp which reduces the temperature of a sealing portion during lighting and has improved adhesion between a bulb and a sealing material, and the cold cathode discharge lamp as a light source. It aims at provision of the illuminating device equipped as.

  The cold cathode discharge lamp according to claim 1 includes a bulb having sealing portions at both ends; a pair of discharge electrodes sealed in the bulb; and supporting the discharge electrode at one end side, and an intermediate portion being sealed. A sealing material that is sealed to the stopper and the other end is led out of the bulb, at least an intermediate part is mainly composed of at least one of molybdenum or tungsten, and a copper layer of 1 to 10 μm is formed on the outer surface; It is characterized by comprising.

  In the invention described in claim 1 and the invention described in each of the following claims, the definitions and technical meanings of terms are as follows unless otherwise specified.

  The cold cathode discharge lamp includes a discharge lamp such as a lamp enclosing mercury and a rare gas or a lamp using rare gas emission that does not enclose mercury. Further, the use of the lamp is not limited to the backlight, but can be used not only for general illumination but also for lamps for display and ultraviolet radiation. The valve preferably has a reduced inner diameter of about 5 mm or less.

As the bulb, soft glass, hard glass, quartz, ceramic, or the like can be used, but it is preferable to use hard glass. Hard glass is glass having a coefficient of thermal expansion of 32 to 60 × 10 ⁻⁷ / ° C.

  The main component of the sealing material may be molybdenum, tungsten alone, or an alloy obtained by adding a subcomponent metal such as copper or rhenium to molybdenum or tungsten. As the composition of the main component, a preferable material may be selected so as to obtain a coefficient of thermal expansion that can ensure airtightness with the valve.

  The sealing material is formed with a copper layer of 1 to 10 μm, preferably 2 to 3 μm on the peripheral surface of these main components. The copper layer is formed at least on the sealing portion. The sealing material is sealed directly or indirectly by bead glass when sealed at both ends of the cylindrical glass tube. However, in order to reliably and easily seal the sealing material, glass is used. It is preferable to use one that has been wound (beaded glass).

  The discharge electrode may be formed by pressing from a plate-like metal into a bottomed cylindrical shape, or may be formed by sintering. Further, the discharge electrode and the sealing material may be integrally formed.

  The cold cathode discharge lamp according to claim 2, wherein a copper layer is formed on the outer peripheral surface of the sealing material up to the discharge electrode, and a bonding metal material is formed on the discharge electrode and the sealing material. It is characterized in that it is welded to a layer and bonded together.

  The lower the melting point of the bonding metal material, the easier the welding between the discharge electrode and the sealing material. However, if the melting point is too low, the strength of the welded portion decreases due to the temperature rise of the electrode during lamp operation. Therefore, a low melting point metal having a melting point of about 1000 to 1700 ° C. is desirable. For example, Kovar, copper, nickel, etc. are optimal.

  By forming cuprous oxide on the surface of the copper layer, the adhesion with the glass is increased and the copper layer can be firmly sealed. In addition, since the wettability with adhesive metal materials such as nickel, copper, and cobalt is better than molybdenum, the welding strength between the electrode and the sealing material is higher than when using a sealing material made only of molybdenum. .

  The cold cathode discharge lamp according to claim 3, wherein a copper layer is formed up to the discharge electrode on an outer peripheral surface of the sealing material, and a part of the copper layer formed on the sealing material is melted to form the discharge. The electrode and the sealing material are bonded together.

  The cold cathode discharge lamp according to claim 4, wherein the other end side of the sealing material is welded to an external lead wire having a coating layer made of copper formed on the outer surface, and is connected to a welded portion with the external lead wire. A copper layer is formed on the outer peripheral surface, and a part of the coating layer is melted and welded to the copper layer formed on the sealing material.

  As the external lead wire, for example, a dumet wire formed by depositing 20 to 25% by mass of copper on the surface of the Fe—Ni alloy wire with respect to the entire external lead wire is used. Here, the composition ratio of Fe—Ni and the like are not particularly limited and can be appropriately selected according to the application.

  By forming cuprous oxide on the surface of the copper layer, the adhesion with the glass is increased and the copper layer can be firmly sealed. Further, since the wettability of copper is better than that of molybdenum, the welding strength between the sealing material and the external lead wire is higher than when a sealing material made only of molybdenum is used.

  According to a fifth aspect of the present invention, there is provided a cold lighting apparatus comprising: the cold cathode discharge lamp according to any one of the first to third aspects; and an apparatus main body to which the lamp is mounted.

  The lighting device can be applied to a display backlight device housed in a liquid crystal display device or the like, but can also be used for other display devices and lighting fixtures.

  According to the cold cathode discharge lamp of the first aspect, the sealing performance of the bulb end is enhanced by the copper layer formed on the outer peripheral surface.

  According to the cold cathode discharge lamp of the second aspect, since the wettability of the sealing material is increased, the welding strength between the discharge electrode and the sealing material is increased.

  According to the cold cathode discharge lamp of the third aspect, in the welding of the discharge electrode and the sealing material, it is not necessary to prepare a glazing material as a separate member between them, and the manufacture is easy.

  According to the cold cathode discharge lamp of the fourth aspect, since the wettability of the sealing material is increased, the connection strength with the external lead wire coated with the copper layer is increased.

  According to the illuminating device of the fifth aspect, it is possible to provide an illuminating device equipped with the cold cathode discharge lamp having the effects of the first to third aspects.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a partially cutaway front view showing a cold cathode discharge lamp of the present invention.

The cold cathode discharge lamp L is, for example, a straight tube type and consumes less than 5 W, for example, 2.5 W. The lamp L has a bulb 1 made of hard glass (thermal expansion coefficient 51 × 10 ⁻⁷ / ° C.) having an outer diameter of about 2.6 mm, an inner diameter of about 1.6 mm, and a length of about 200 mm. The bulb 1 has a phosphor layer P formed on the inner wall surface and sealed at both ends by glass beads 3 welded to a sealing material 2 to form a sealed portion. The bulb 1 contains a discharge medium made of a mixed gas of mercury, argon and neon.

Hard glass is a glass having a thermal expansion coefficient of 32 to 60 × 10 ⁻⁷ / ° C., and is a borosilicate glass (thermal expansion) containing boron oxide (B ₂ O ₃ ) and silicic acid (SiO ₂ ) as main components. Rate 51 × 10 ⁻⁷ / ° C.).

The sealing material 2 is connected to the external lead wire 4, and the sealing material 2 seals the bulb 1 through the glass bead 3, so that molybdenum (Mo) having a diameter of 1.0 mm whose thermal expansion coefficient approximates that of the bulb 1. ) (Thermal expansion coefficient 51 × 10 ⁻⁷ / ° C.) wire is used.

  In order to increase the luminous efficiency of the cold cathode discharge lamp, a bottomed cylindrical discharge electrode 5 made of molybdenum having a low work function is used, and the discharge electrodes 5 are sealed inside both ends of the bulb 1, respectively. The discharge electrode 5 is connected to one end side of the sealing material 2 by welding.

  The bottomed cylindrical discharge electrode 5 made of molybdenum has a bottom portion 5a having a diameter of about 2.0 mm.

  FIG. 2 is a cross-sectional view showing the sealing material before welding according to the first embodiment of the present invention.

  In the sealing material 2, a copper layer 2 b (Cu) is formed with a thickness of 2 μm on the outer peripheral surface of a molybdenum (Mo) wire 2 a formed in a columnar shape having a diameter of about 1.0 mm. A copper layer is not formed on one end surface 2c and the other end surface 2e of the wire 2a. The wire 2a made of molybdenum (Mo) uses a wire material obtained by cutting a molybdenum wire (Mo) according to the intended use. However, the molybdenum wire material may be added with other elements, or may be formed to a predetermined size by sintering. The copper layer 2b can be formed on the outer peripheral surface of the wire 2a obtained by barrel-polishing this molybdenum wire material by a method such as electroplating or vapor deposition. Moreover, after forming a copper layer in a molybdenum wire (Mo), you may cut | disconnect to the predetermined dimension.

Molybdenum (Mo) has a thermal expansion coefficient close to that of hard glass and has a relatively good sealing property. By the way, a part of the sealing material 2 diffuses into the valve 1 at the sealing portion of the valve 1, so that they are in close contact with each other and high airtightness is obtained. That is, the sealing property between the valve 1 and the sealing material 2 is not determined only by the coefficient of thermal expansion, and the greater the diffusion of the sealing material 2 to the valve 1, the higher the sealing force can be achieved. The diffusion of the sealing material into the valve is a mode in which the particles of the sealing material are scattered in the components of the valve on the valve side from the interface between the valve and the sealing material, or a part of the sealing material. The state which exists in a valve | bulb so that it may extend from may be said. Further, the diffusion may be generated in at least a part of the sealing portion of the valve. As a result of examination by the present inventor in order to improve the sealing performance, when a copper layer having a predetermined thickness is coated on the outer peripheral surface of the molybdenum wire 2a which is a sealing material, a part of the copper layer 2b diffuses into the glass constituting the bulb. It has been found that the adhesion is increased by doing. That is, when molybdenum (Mo) is used as a sealing material, the diffusion of molybdenum (Mo) into the glass is about 0.5 μm from the interface, whereas when the copper layer is formed on the outer peripheral surface to 1 to 10 μm, the copper layer It was found that some diffused to about 5 μm from the interface. The copper layer is thought to be bonded tightly to the glass because the copper on the surface is oxidized to form dense cuprous oxide (Cu ₂ O) and this cuprous oxide (Cu ₂ O) diffuses into the glass. It is done. In addition, since copper has a higher thermal conductivity than molybdenum and tungsten, the sealing material in which the copper layer is formed on the outer peripheral surface of the wire 2a has a higher thermal conductivity than the sealing material made only of molybdenum. Can be expected. When the copper layer formed on the outer peripheral surface is 10 μm or more, the thermal expansion coefficient of the sealing material changes, and the sealing property is deteriorated. On the other hand, when the copper layer is 1 μm or less, the copper layer is not sufficiently diffused, so that the sealing strength does not increase so much. For this reason, the copper layer formed on the outer peripheral surface of the sealing material is 1 to 10 μm, preferably 2 to 3 μm.

  According to the sealing material 2 having this configuration, the thermal expansion coefficient is similar to that of hard glass, and the diffusion into the valve 1 is greater than that of the sealing material made only of molybdenum, so that the sealing property can be improved. Furthermore, since the copper layer 2b is formed on the outer peripheral surface, the effect of increasing the thermal conductivity and improving the heat dissipation can be expected.

  FIG. 3 is an enlarged cross-sectional view showing a connection state between the discharge electrode 5 and the sealing material 2 of the first embodiment.

  The discharge electrode 5 and the sealing material 2 are connected by an adhesive metal material 6 made of Kovar so that the outer end surface 5b of the bottom 5a and the one end surface 2c of the sealing material 2 face each other. The bonding metal material 6 is attached to the outer end surface 5b of the discharge electrode 5 and the side surface 2d on the end surface 2c side of the sealing material 2, and the appearance is a smooth concave curved surface.

  Next, a method for connecting the discharge electrode 5 and the sealing material 2 will be described. First, the bonding metal material 6 made of substantially disk-shaped Kovar is temporarily fixed to the end surface 2a of the sealing material 2 at a position where the respective diameter centers coincide. The fixing method can be fixed by various methods such as resistance welding and adhesion with a metal brazing material such as solder. Next, the bonding metal material 6 attached to the sealing material 2 is brought into contact with the outer end surface 5b of the bottom 5a of the discharge electrode 5 and is welded by resistance welding. At this time, the central axes of the discharge electrode 5 and the sealing material 2 are aligned with each other. At the time of welding, the bonding metal material 6 melts and adheres to the outer end surface 5b of the discharge electrode 5 and the side surface 2d on the end surface 2c side of the sealing material 2, and both are firmly welded. The heat generated in resistance welding between the discharge electrode 5 and the sealing material 2 is generated by the Joule heat of resistance, and the high temperature region spreads outward from the center of the one end surface 2c of the sealing material 2 in a ripple shape.

  By the way, the tensile strength of the welded portion formed by welding the bonding metal material 6 is determined by the area where the molten bonding metal material 6 adheres to the outer end surface 5b of the discharge electrode 5 and the side surface 2d of the sealing material 2. Depends on the area to be. Since this area changes depending on the diameter and foil thickness of the bonding metal material 6 before melting, the tensile strength of the weld can be improved by optimizing the dimensions of the bonding metal material 6. Furthermore, this area also changes depending on the wettability of the sealing material 2 and the discharge electrode 5. When the outer peripheral surface of the sealing material 2 is molybdenum (Mo), the wettability of the molten metal material 6 for adhesion is poor. However, when the copper layer 2 a is formed on the outer peripheral surface of the sealing material 2, the low melting point metal has good wettability with respect to copper, so the wettability of the adhesive metal material 6 is improved, and the adhesive metal material 6 is Since it spreads to the other end side and the deposition area increases, the connection strength increases.

  FIG. 4 is an enlarged cross-sectional view showing a connection state between the sealing material 2 and the external lead wire 4 of the first embodiment.

  The other end surface 2e of the sealing material 2 and the distal end surface of the external lead wire 4 are connected by resistance welding. The external lead wire 4 is formed such that a coating layer 4b made of copper is deposited on the surface of a core wire 4a made of a Ni—Fe alloy having a diameter of 0.8 mm with respect to the entire external lead wire by 20 to 25 mass%. . The power of resistance welding is about 300W. By this welding, a part of the tip of the external lead wire 4 is melted at the time of welding to form a bulging portion 4c having a substantially spherical shape with a part larger in diameter than the sealing material 2. The bulging portion 4c is attached so as to extend on the outer peripheral surface on the intermediate side with respect to the outer end surface 2e of the sealing material 2. Here, the copper layer 2a is formed on the outer peripheral surface of the sealing material 2, so that the wettability is improved, the deposition area is increased, and the connection strength is improved. The external lead wire 4 can be an inexpensive dumet wire that has been conventionally used as a lead wire for sealing soft glass.

  Next, the manufacturing method of the cold cathode discharge lamp of the 1st Embodiment of this invention is demonstrated.

  First, the glass beads 3 are fused to the sealing material 2, and a metal film made of Kovar is fixed to one end of the sealing material 2. Subsequently, current is applied to the outer end surface 5b of the discharge electrode 5 made of molybdenum while pressing one end of the sealing material 2 via the bonding metal material 6, and the bonding metal material 6 is connected to the end of the sealing material 2 and It is surely fused to both bottom surfaces of the discharge electrode 5. Next, the glass beads 3 are fused to one end side of the bulb 1 to seal the sealing material 2, and the external lead wire 4 is welded to the other end portion of the sealing material 2 to form an electrode on one end side. . Then, after exhausting the inside of the valve 1 and enclosing a predetermined rare gas, the other end of the valve 1 is similarly sealed, and the external lead wire 4 is welded to the other end of the sealing material 2. One electrode is formed.

  Next, a second embodiment according to the present invention will be described.

  FIG. 5 is a cross-sectional view showing the sealing material before welding according to the second embodiment of the present invention. A copper layer 2b is formed on the outer peripheral surface, one end surface 2c and the other end surface 2e of the molybdenum wire 2a. The sealing material 2 having this configuration is obtained by forming the copper layer 2b on the outer surface of the wire 2a obtained by barrel polishing a molybdenum wire material by a method such as electroplating or vapor deposition. Further, the thickness of the copper layer 2b formed on the one end surface 2c of the sealing material 2 may be different from the thickness of the copper layer formed on the outer peripheral surface, and preferably 2 to 100 μm. When the one end face 2a of the sealing material 2 and the bottom face of the discharge electrode 5 are brought into contact with each other and welded, the copper layer 2b formed on the one end face 2c is melted and functions as the bonding metal material 6. To do. For this reason, it is not necessary to dispose and weld another member made of a low melting point metal between the discharge electrode 5 and the sealing material 2, so that the electrode can be easily manufactured. Further, since the copper layer is formed on the outer peripheral surface, the wettability of the molten copper is improved, and the connection strength is the same as that in the case where the adhesive metal material made of Kovar is provided. On the other hand, when the sealing material 2 and the external lead wire 4 are resistance-welded, heat is transferred from the center of the external lead wire 4 in a ripple pattern, so the copper layer formed on the other end surface 2e is more than the coating layer 4b of the external lead wire. The temperature rises quickly. For this reason, the copper layer formed on the other end surface 2e is easily melted, and welding of both is facilitated.

  Further, the cold cathode discharge lamp of the second embodiment can be manufactured by the same manufacturing method as that of the first embodiment.

  The present invention is not limited to the above embodiments. For example, the glass bead 3 as the sealing portion is not necessarily required, and the sealing material 2 may be sealed to the end portion of the bulb 1 as it is. The lamp is not limited to a cold cathode fluorescent lamp, and a discharge maintaining medium may contain a light emitting material other than mercury. For example, a lamp of various thin tubes such as a lamp using rare gas emission in which xenon gas is enclosed. Applicable to discharge lamps. The shape of the valve is not limited to a straight tube shape, and may be bent into a U shape, a W shape, a ring shape, or the like.

  FIG. 6 is a schematic cross-sectional view showing an illumination device 11 equipped with the cold cathode discharge lamp L of the above embodiment. Reference numeral 11 denotes a liquid crystal display device as an illumination device. The liquid crystal display device 11 has a thin box-like case body 13 having an irradiation opening 12 on the front surface. The unit 14 is accommodated. The backlight unit 14 includes a cold cathode discharge lamp L, and a silver-deposited film-like reflecting surface 15 that also serves as a proximity conductor so as to contain the bulb 1 is provided in the vicinity of the cold cathode discharge lamp L. The light guide plate 16 made of acrylic resin is disposed in the irradiation direction of the reflecting surface 15.

  The light guide plate 16 is positioned to face the opening 12 of the case body 13. In addition, a planar reflecting plate 18 is disposed on the back side of the light guide plate 16, and a light control means 22 configured by a diffusion plate 20 and a light collecting plate 21 between the light guide plate 16 and the case body 13. Is arranged. A liquid crystal unit 24 as a display means is disposed on the front side of the opening 12 of the case body 13.

It is a partially cutaway front view showing the cold cathode discharge lamp of the present invention. It is sectional drawing which shows the sealing material of 1st Embodiment by this invention. It is an expanded sectional view which shows the connection state of the discharge electrode of 1st Embodiment, and a sealing material. It is an expanded sectional view which shows the connection state of the sealing material of 1st Embodiment, and an external lead wire. It is sectional drawing which shows the sealing material of 2nd Embodiment by this invention. It is a schematic sectional drawing which shows the illuminating device carrying the cold cathode discharge lamp of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Discharge electrode, 2 ... Sealing material, 4 ... External lead wire, 5 ... Discharge electrode, 6 ... Adhesive, 11 ... Illuminating device, 14 ... Illuminating device main body, P ... Cold cathode discharge lamp

Claims (5)

A valve having seals at both ends;
A pair of discharge electrodes sealed within the bulb;
The discharge electrode is supported on one end side, the middle portion is sealed to the sealing portion, and the other end side is led out of the bulb. At least the middle portion is mainly composed of at least one kind of molybdenum or tungsten, and the outer surface has 1 A sealing material on which a copper layer of 10 μm is formed;
A cold cathode discharge lamp comprising:   A copper layer is formed on the outer peripheral surface of the sealing material up to the discharge electrode, and an adhesive metal material is welded to and bonded to the copper layer formed on the discharge electrode and the sealing material. The cold cathode discharge lamp according to claim 1.   A copper layer is formed on the outer peripheral surface of the sealing material up to the discharge electrode, and a part of the copper layer formed on the sealing material is melted to bond the discharge electrode and the sealing material. The cold cathode discharge lamp according to claim 1.   The other end side of the sealing material is welded to an external lead wire in which a coating layer made of copper is formed on the outer surface, and a copper layer is formed on the outer peripheral surface to the welded portion with the external lead wire. 4. The cold cathode discharge lamp according to claim 1, wherein a part of the layer is melted and welded to a copper layer formed on the sealing material. A cold cathode discharge lamp according to any one of claims 1 to 4;
The device body to which this lamp is mounted;
An illumination device comprising:

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