JP2007080777A - Electrode, electrode unit, and cold cathode lamp - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cold cathode lamp with low manufacturing cost and capable of extending lifetime of the cold cathode lamp. <P>SOLUTION: The cold cathode lamp 1 is provided with a glass tube 2, a fluorescent film 3, electrodes 4, and lead members 5. The glass tube 2 forms an enclosed space. The fluorescent film 3 is formed on the inner face of the glass tube 2. The electrodes 4 are formed in a cup-shape and are respectively sealed to the both end parts of the glass tube 2 in a state that the opening parts 41 are mutually faced inside. Of this electrode 4, the outside diameter of the cylindrical part 43 of cup-shape is constant from the bottom 42 side to the opening part 41 side, and the thickness of a first portion 431 being a cylindrical portion 43 of at least a half to the bottom 42 side and the bottom 42 is larger than that of a second portion 432 being the cylindrical portion 43 to the opening part 41 side. The lead member 5 is connected to the electrode 4 and led out to the outside of the glass tube 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode sealed at an end of a cold cathode lamp used for, for example, a backlight of a liquid crystal screen, an electrode unit including the electrode, and a cold cathode lamp.

  Cold cathode lamps have been widely used as backlights for display devices such as liquid crystal panels because of their low power consumption and long life as a light source. The cold cathode lamp includes a glass tube in which a discharge gas is sealed, and a pair of electrode units sealed at both ends of the glass tube. The discharge gas is composed of an inert rare gas such as argon and mercury vapor. The electrode unit includes a lead having conductivity and excellent adhesion to glass, and an electrode connected to the end of the lead and housed in the glass tube.

  When a voltage is applied between the electrodes, electrons are emitted from one of the electrodes. Ultraviolet rays are emitted when the emitted electrons collide with mercury atoms. This ultraviolet light is converted into visible light by the fluorescent film applied to the inner surface of the glass tube. As a result, the cold cathode lamp emits visible light.

  The electrodes disclosed in Patent Document 1 and Patent Document 2 are formed in a cup shape so that the vicinity of the electrodes is not blackened by ions emitted from the electrodes. The openings of the electrodes are arranged to face each other. While the cold cathode lamp is turned on, argon ions accelerated by the collision of the emitted electrons strike the electrode.

At this time, if the electrode is made of nickel (Ni), sputtering is likely to occur. In the case of a cup-shaped electrode, it is known that the inner surface of the cup-shaped electrode 100 is sputtered as shown in FIG. When the electrode 100 is corroded by sputtering, a hole is opened at the end, and in some cases, it falls off. In order to make it less susceptible to sputtering, Patent Documents 1 and 2 disclose, for example, that an electrode is made of niobium (Nb), titanium (Ti), tantalum (Ta), or an alloy thereof. In addition, as a material hardly affected by sputtering, Patent Document 3 mentions molybdenum (Mo) and tungsten (W).
JP 2002-110085 A JP 2002-358922 A JP 2003-187740 A

  However, materials such as molybdenum (Mo), tungsten (W), and tantalum (Ta) have low toughness and are difficult to roll and press. Moreover, since these materials are rare metals, the material unit price is high. Further, Mo, Nb, W, and Ta all have high melting points, so that they are not sufficiently melted in bonding with the lead, and the required bonding strength may not be obtained.

  Moreover, when the electrodes made of these refractory metals are sealed in the glass tube, the heat that melts the glass tube may be transmitted to oxidize the surface. If an oxide film is formed, the effect on sputtering will fall. Furthermore, once Mo or Nb is oxidized, it is very difficult to reduce it in a later step. Therefore, care must be taken in handling during the manufacturing process.

  Since Mo and Nb are refractory metals, high heat is applied to join the lead member to the electrode made of Mo or Nb. However, heat is excessively applied to the lead member, which is not preferable.

  In consideration of the fact that materials are available at low cost and easy to process, it is also possible to make the electrodes thick in advance and make them as Ni so that they can withstand long-term use. Conceivable. However, when the diameter of the cold cathode lamp is reduced, the inner diameter of the cup becomes too small, which makes the processing difficult, and a sufficient hollow cathode effect as a cup electrode cannot be obtained.

  Therefore, the present invention provides an electrode that can be manufactured at low cost and can extend the life of a cold cathode lamp, an electrode unit having the electrode, and a cold cathode lamp.

  The electrode according to the present invention is used for a cold cathode lamp and has a cup shape. The outer diameter dimension of the cup-shaped cylindrical part is constant from the bottom side to the opening side, and the thickness of the first part and the bottom part that are at least half the cylindrical part near the bottom part is the cylindrical part near the opening part. It is larger than the thickness of the second part.

  The electrode unit of the present invention is sealed to both ends of the glass tube of the cold cathode lamp, and includes an electrode and a lead portion. The electrode has a cup shape enclosed inside the glass tube. In the electrode, the outer diameter of the cup-shaped cylindrical portion is constant from the bottom side to the opening side, and the thickness of the first portion and the bottom portion that are at least half the cylindrical portion near the bottom portion is close to the opening portion. It is larger than the thickness of the 2nd part which is a cylindrical part. The lead member is connected to this electrode and led out to the outside of the glass tube.

  The cold cathode lamp of the present invention includes a glass tube, a fluorescent film, an electrode, and a lead member. The glass tube forms a sealed space. The fluorescent film is formed on the inner surface of the glass tube. The electrodes are formed in a cup shape and are respectively sealed at both ends of the glass tube so that the openings are inward of each other. In this electrode, the outer diameter of the cup-shaped cylindrical part is constant from the bottom side to the opening side, and the thickness of the first part and the bottom part that are at least half the cylindrical part near the bottom part is close to the opening part. It is larger than the thickness of the second part which is the cylindrical part. The lead member is connected to the electrode and led out of the glass tube.

  In the electrode of the present invention, the thickness of the bottom portion and the cylindrical portion near the bottom portion is larger than the thickness near the cup-shaped opening. Therefore, this electrode can maintain a sufficient life even when it is subjected to corrosion due to sputtering while ensuring a sufficient effective diameter of the opening. And since Ni can be used as a material of an electrode, material cost and a manufacturing unit price can also be held down cheaply. In addition, the electrode unit and the cold cathode lamp of the present invention can be provided with this electrode, thereby extending the life of the cold cathode lamp.

  A first embodiment according to the present invention will be described. A cold cathode lamp 1 shown in FIG. 1 includes a glass tube 2, a fluorescent film 3, an electrode 4, and a lead member 5. The glass tube 2 forms a sealed space as the cold cathode lamp 1. In the sealed space, a mixed gas 6 in which a rare gas such as argon, xenon, or neon and mercury vapor are mixed in a desired ratio is sealed at a pressure of about 0.1 atm.

  The glass tube 2 is made of lead glass, soda glass or low lead glass in addition to boro-silicate glass. When the cold cathode lamp 1 is used as a light source for a backlight of a liquid crystal panel, several types of glass tubes 2 having an outer diameter in a range of φ1.5 mm to φ5.0 mm are prepared. It is used properly according to the.

  The fluorescent film 3 is formed by uniformly applying a fluorescent material over the entire inner wall of the glass tube 2. The fluorescent material can be applied from existing materials such as halophosphate phosphors and rare earth phosphors to fluorescent materials that will be newly developed in the future.

  The electrode 4 has a cup shape having an outer diameter slightly smaller than the inner diameter of the glass tube 2 in a state where the fluorescent film 3 is formed on the inner surface. The electrodes 4 are respectively sealed at both ends of the glass tube 2. The electrodes 4 are arranged with the cup-shaped openings 41 facing each other. As shown in FIG. 2, the electrode 4 includes a bottom portion 42 and a cylindrical portion 43.

  The outer diameter of the cylindrical portion 43 is constant from the bottom 42 side to the opening 41 side. In the cylindrical portion 43, the inner diameter dimension of the second portion 432 closer to the opening 41 is larger than the inner diameter dimension of the first portion 431 half closer to the bottom portion 42. That is, the thickness of the first portion 431 of the cylindrical portion 43 is larger than the thickness of the second portion 432.

  The thickness of the bottom portion 42 is substantially the same as that of the first portion 431 of the cylindrical portion 43. Moreover, it is preferable that the internal diameter dimension of the 2nd part 432 is made into the substantially same magnitude | size as the conventional electrode. Thus, the thickness of the member of the cup-shaped electrode 4 is made from half to deep in the depth direction of the cup and from the half to the near side.

  A transition portion between the inner peripheral surface of the first portion 431 and the inner peripheral surface of the second portion 432 is gently continuous with a tapered portion 433 having a certain gradient. The tapered portion 433 is preferably provided on the first portion 431 side and has a length that does not exceed ¼ of the length of the cylindrical portion 43. Further, the opening 41 is formed with a reduced diameter portion 411 that is thinner than the inner diameter of the second portion 432 while maintaining the thickness of the second portion 432. By having this reduced diameter part 411, when inserting the electrode 4 in the glass tube 2 in which the fluorescent film 3 was formed, it can prevent that the fluorescent film 3 is spoiled.

  As in the conventional electrode 100 shown in FIG. 3, the portion where the electrode 100 is corroded by sputtering is located at the inner surface A of the bottom 101 and about a quarter of the position from the bottom 101 in the depth direction of the cup shape. It has been clarified by the inventor that the inner surface B of the cylindrical portion 102 is in the center range. Further, the corroded range does not depend on the cup-shaped aperture.

  Therefore, by making the thickness of the first portion 431 from the bottom portion 42 to half in the length direction of the cylindrical portion 43 and the thickness of the second portion 432 which is a half near the opening portion 41 by sputtering, by sputtering. Improves durability against aging corrosion. Moreover, since the aperture 41 has the same diameter as the conventional one, the electrode 4 does not impair the hollow cathode effect.

  The lead member 5 includes a sealing member 51 having excellent wettability with respect to the glass tube 2 and a lead wire 52 connected to the wiring. The sealing member 51 is joined to the lead wire 52 and then joined to the bottom 42 of the electrode 4 by resistance welding (flash welding), laser beam welding, or the like.

  In the electrode unit 7 composed of the electrode 4 and the lead member 5, the bead glass 8 is welded to the sealing member 51 prior to joining with the glass tube 2. When the electrode unit 7 is attached to the glass tube 2, the bead glass 8 and the end of the glass tube 2 are melt-bonded.

  With the above configuration, the durability of the electrode 4 against sputtering is improved, so that the life of the cold cathode lamp 1 is extended. Further, since the inner diameter of the opening 41 of the electrode 4 is not different from the conventional one, the same hollow cathode effect can be obtained. Moreover, since Ni conventionally used for the material of the electrode 4 can be applied, compared with using Mo or Nb as the material, the material unit price is low, and management during manufacture is easy.

1 is a cross-sectional view showing a cold cathode lamp according to an embodiment of the present invention. Sectional drawing which shows the electrode of the electrode unit of the cold cathode lamp shown in FIG. Sectional drawing of the electrode of the conventional cold cathode lamp.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Cold cathode lamp, 2 ... Glass tube, 3 ... Fluorescent film, 4 ... Electrode, 5 ... Lead member, 6 ... Mixed gas, 7 ... Electrode unit, 8 ... Bead glass, 41 ... Opening part, 42 ... Bottom part, 43 ... cylindrical part, 411 ... reduced diameter part, 431 ... first part, 432 ... second part, 433 ... taper part.

Claims (6)

A cup-shaped electrode used in a cold cathode lamp,
The outer diameter of the cup-shaped cylindrical portion is constant from the bottom side to the opening side,
The thickness of the first part, which is the cylindrical part near the bottom part, and the bottom part is larger than the thickness of the second part, which is the cylindrical part near the opening.   2. The electrode according to claim 1, wherein the inner peripheral surface of the first portion and the inner peripheral surface of the second portion are connected by a tapered portion having a certain gradient.   2. The first portion according to claim 1, wherein the first portion has a tapered portion that extends from an inner diameter of the first portion to an inner diameter of the second portion at an end near the second portion. The electrode as described.   2. The electrode according to claim 1, wherein the opening has a reduced diameter portion that is thinner than an inner diameter of the second portion with a thickness of the second portion. An electrode unit sealed to both ends of a glass tube of a cold cathode lamp,
A cup-shaped electrode enclosed inside the glass tube, and a lead member connected to the electrode and led out of the glass tube;
The electrode is
The outer diameter dimension of the cup-shaped cylindrical portion is constant from the bottom side to the opening side,
The electrode unit, wherein the thickness of the first portion, which is the cylindrical portion near the bottom, and the thickness of the second portion, which is the cylindrical portion near the opening, is larger. A glass tube forming a sealed space;
A fluorescent film formed on the inner surface of the glass tube;
An electrode formed in a cup shape and sealed in both ends of the glass tube in a state in which the openings are inward of each other;
In a cold cathode lamp comprising a lead member connected to the electrode and led out of the glass tube,
The electrode is
The outer diameter dimension of the cup-shaped cylindrical portion is constant from the bottom side to the opening side,
The cold cathode lamp, wherein the thickness of the first portion, which is the cylindrical portion near the bottom, and the thickness of the second portion, which is the cylindrical portion near the opening, is larger than the thickness of the second portion which is the cylindrical portion near the opening. .

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