JP4934156B2 - Cold cathode fluorescent tube electrode and cold cathode fluorescent tube using the same - Google Patents

Description

  The present invention relates to an electrode for a cold cathode fluorescent tube and a cold cathode fluorescent tube using the same.

  Cold cathode fluorescent tubes are widely used as light sources for backlights of liquid crystal displays. The cold cathode fluorescent tube includes a small-diameter glass tube in which Hg vapor and an inert gas such as Ar and Ne are enclosed and a fluorescent material is coated on the inner wall surface, and tube shafts at both ends of the glass tube. A pair of cold-cathode fluorescent tube electrodes that are mounted to face each other in the direction. In a cold cathode fluorescent tube, an electric field is generated by applying a high voltage between a pair of cold cathode fluorescent tube electrodes, and electrons are emitted from an unheated cathode (cold cathode). Next, when the electrons collide with the Hg atoms, the Hg atoms are excited, and the ultraviolet rays emitted when the Hg atoms transition from the excited state to the ground state irradiate the phosphor, whereby visible light is emitted from the phosphor. Is released.

  In general, the cold cathode fluorescent tube electrode is formed by forming a thin plate-shaped electrode material into a bottomed cylindrical body having one opening by plastic working such as deep drawing. Conventionally, as the electrode for the cold cathode fluorescent tube, an electrode substantially made only of Ni has been widely used. Ni is excellent in plastic workability and has an advantage as an electrode for a cold cathode fluorescent tube.

  Accordingly, various cold cathode fluorescent tube electrodes made of a Ni-based alloy have been proposed focusing on the characteristics of Ni. For example, the present inventors have proposed a cold cathode fluorescent tube electrode made of a Ni-based alloy containing Mo and Nb (see Patent Document 1).

  However, the cold cathode fluorescent tube electrode substantially made of Ni and the cold cathode fluorescent tube electrode made of a Ni-based alloy are easily sputtered with Ni constituting the electrode, and the sputtered Ni atoms are enclosed in a glass tube. The Hg atoms are consumed by the reaction with Hg atoms, so there is a disadvantage that the life of the cold cathode fluorescent tube is shortened, and it is not suitable for reducing mercury in the cold cathode fluorescent tube as an environmental measure. There is an inconvenience.

  On the other hand, in some applications, an electrode for a cold cathode fluorescent tube substantially composed of Mo is used (for example, see Patent Document 2). The cold cathode fluorescent tube electrode consisting essentially of Mo has excellent discharge characteristics since the tube voltage is low and the energy efficiency is good. In addition, the cold cathode fluorescent tube electrode consisting essentially of Mo is superior in spatter resistance to the cold cathode fluorescent tube electrode consisting of a Ni-based alloy, so the life of the cold cathode fluorescent tube is extended. can do.

  However, the cold cathode fluorescent tube electrode consisting essentially of Mo is disadvantageous in that Mo is extremely expensive, has high hardness and is difficult to process into an electrode, and therefore the manufacturing cost increases.

JP 2007-31832 A JP 2000-133201 A

  The present invention eliminates such inconvenience, has excellent spatter resistance and workability, lowers the tube voltage, suppresses reaction with mercury, and can realize low mercury as an environmental measure. An object of the present invention is to provide an electrode for a cold cathode fluorescent tube and a cold cathode fluorescent tube using the same.

  The inventors of the present invention have made various studies in order to achieve the above object, and have focused on Fe as a metal element that can be manufactured at a lower cost than Mo and has better sputtering resistance than Ni. However, since the cold cathode fluorescent tube electrode consisting essentially of Fe still has problems in the discharge characteristics and the sputtering resistance, it has been attempted to add various alloy elements containing Fe as a main component. As a result, a cold cathode fluorescent tube electrode made of an Fe-based alloy containing Mo and Nb in a predetermined range has a discharge characteristic and sputter resistance comparable to the cold cathode fluorescent tube electrode substantially made only of Mo. The inventors have found that both are possible and have reached the present invention.

  That is, the cold cathode fluorescent tube electrode of the present invention contains Mo in the range of 0.1 to 30% by mass and Nb in the range of 0.1 to 6% by mass with the balance being Fe and It consists of an alloy which is an inevitable impurity.

  The electrode of the present invention can be used for a cold cathode fluorescent tube.

Explanatory drawing which shows the cold cathode fluorescent tube and electrode for cold cathode fluorescent tubes of this embodiment. The graph which shows the current-voltage characteristic of the electrode for cold cathode fluorescent tubes of this embodiment.

  Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings. A cold cathode fluorescent tube 1 according to this embodiment shown in FIG. 1 is used for a light source for a backlight of a liquid crystal display. For example, a glass tube 2 having a diameter of 3 mm and 1 attached to both ends of the glass tube 2 are used. And a pair of cold cathode fluorescent tube electrodes 3.

  The glass tube 2 is coated with a well-known phosphor on the inner wall surface, and Hg vapor and an inert gas such as Ar or Ne are sealed inside.

  The cold-cathode fluorescent tube electrode 3 is a bottomed cylindrical body having one opening, and the opening has an outer diameter of 2.1 mm, a wall thickness of 0.15 mm, and a length of 7.0 mm. The cold cathode fluorescent tube electrode 3 may have a thin plate shape, but the bottomed cylindrical body can facilitate the emission of electrons from the electrode 3.

  Each pair of cold cathode fluorescent tube electrodes 3 is mounted in the glass tube 2 with the openings facing each other in the axial direction of the glass tube 2. The bottom of the cold cathode fluorescent tube electrode 3 is connected to a sealing pin 4 made of a Kovar wire, sealed to the glass tube 2 and protruding outward from the glass tube 2. An external lead wire 5 made of a dumet wire is connected to the end of the sealing pin 4 opposite to the cold cathode fluorescent tube electrode 3. Further, glass beads (not shown) for sealing with the glass tube 2 are attached to the sealing pins 4.

  The cold cathode fluorescent tube electrode 3 contains Mo in the range of 0.1 to 30% by mass and Nb in the range of 0.1 to 6% by mass with the balance being Fe and inevitable impurities with respect to the total amount. Made of an alloy.

  The cold cathode fluorescent tube electrode 3 of the present embodiment (hereinafter sometimes simply referred to as the electrode 3) can be reduced in cost by using Fe as the base element in the alloy constituting the electrode 3. Further, the electrode 3 suppresses the consumption of Hg by suppressing the reaction between the surface of the electrode 3 and the sputtered particles from the electrode 3 and Hg atoms in the glass tube 2, thereby reducing the lifetime of the cold cathode fluorescent tube 1. Can be lengthened. In addition, the electrode 3 can obtain basic electrical characteristics as an electrode and excellent workability by using Fe as an element as a base in the alloy constituting the electrode 3. it can.

  However, as described above, when the alloy constituting the electrode 3 is substantially only Fe, problems remain in discharge characteristics and sputtering resistance. Therefore, in the cold cathode fluorescent tube electrode 3 of the present embodiment, the range of Mo and the range of Nb are added to the alloy.

  In the cold cathode fluorescent tube electrode 3 of the present embodiment, when the alloy contains Mo in the above range, the tube voltage during discharge can be reduced and the electron emission characteristics can be improved. Moreover, the electrode 3 can suppress the rusting of a Fe-based alloy, and can improve corrosion resistance because the said alloy contains Mo of the said range. Moreover, the electrode 3 can suppress more reliably reaction of a Fe-based alloy and Hg because the said alloy contains Mo of the said range.

  At this time, in the alloy, when the Mo content is less than 0.1% by mass with respect to the total amount, the effect cannot be obtained.

On the other hand, in the alloy, when the Mo content exceeds 30% by mass, the tube voltage of the cold cathode fluorescent tube electrode 3 cannot be lowered, and Fe ₂ Mo, Fe is contained in the alloy. An intermetallic compound exhibiting brittleness such as ₃ Mo ₃ is formed, or the workability is lowered by increasing the hardness. Therefore, in the alloy, when the Mo content exceeds 30% by mass with respect to the total amount, the cold cathode fluorescent tube electrode 3 having a desired shape cannot be formed.

  Moreover, the electrode 3 for cold cathode fluorescent tubes of this embodiment can reduce the tube voltage at the time of discharge, and can improve an electron emission characteristic, when the said alloy contains Nb of the said range. Moreover, the electrode 3 can improve sputtering resistance because the said alloy contains Nb of the said range. Moreover, corrosion resistance can be improved by suppressing rusting of the Fe-based alloy.

  At this time, in the alloy, when the Nb content is less than 0.1% by mass with respect to the total amount, the effect cannot be obtained.

On the other hand, when the Nb content exceeds 6% by mass in the alloy, intermetallic compounds exhibiting brittleness such as Fe ₂ Nb are formed in the alloy, or the hardness is increased. As a result, workability is lowered. Therefore, in the alloy, when the Nb content exceeds 6% by mass, the cold cathode fluorescent tube electrode 3 having a desired shape cannot be formed.

  Next, an Example and a comparative example are shown about the electrode 3 for cold cathode fluorescent tubes of this embodiment.

  In this example, first, Fe, Mo, and Nb were melted in a vacuum melting furnace to prepare a molten metal, and cast to produce about 10 kg of ingot. The ingot is composed of an alloy containing 3.4% by mass of Mo and 1.6% by mass of Nb with respect to the total amount, and the balance being Fe and inevitable impurities. The inevitable impurities are 0.10 mass% or less of C, 0.50 mass% or less of Si, 0.80 mass% or less of Mn, and 0.05 mass% or less of the total amount of the alloy. Of P and 0.05% by mass or less of S.

  Next, the ingot was hot forged at a temperature of 1100 ° C. to obtain a plate material having a thickness of 20 mm. Next, the plate material having a thickness of 1 mm was obtained by wire-cutting the plate material having a thickness of 20 mm. Next, the oxide scale produced by the wire cut was removed by polishing the plate material having a thickness of 1 mm.

  Next, cold rolling at normal temperature and annealing at a temperature of 800 ° C. in a hydrogen atmosphere are repeated in this order on the 1 mm-thick plate material from which the oxide scale has been removed. A 2 mm thin plate was obtained. Next, the 0.2 mm thin plate material was annealed at 800 ° C. for 10 minutes in a hydrogen atmosphere, and then cooled to room temperature to obtain an electrode material used for the cold cathode fluorescent tube electrode 3.

Next, a test piece having a length of 20 mm, a width of 20 mm, and a thickness of 0.2 mm was produced from the electrode material obtained in this example. The test piece was placed in a vacuum chamber of a sputtering apparatus, and was continuously sputtered for 8 hours under an Ar atmosphere of 5.33 × 10 ⁻¹ Pa at a power input of 150 W. Next, by measuring the weight loss of the continuously sputtered test piece, the amount of wear due to sputtering in the electrode material obtained in this example was calculated.

  Next, a test piece was manufactured in the same manner as in this example for the electrode material (Reference Example 1) substantially made of Ni excluding inevitable impurities, and the amount of consumption due to sputtering in the electrode material was calculated. Next, when the consumption amount by sputtering of the electrode material obtained in this example with respect to the consumption amount by sputtering in the electrode material of Reference Example 1 was determined, the consumption amount of the electrode material obtained in this example was It was 69.1% of the electrode material of Example 1. The results are shown in Table 1 as the sputtering rate. In Table 1, the smaller the value of the sputtering rate, the smaller the amount of consumption due to sputtering, and the better the sputtering resistance.

  Next, from the electrode material obtained in this example, two pairs of cold cathode fluorescent tube electrodes 3 of this example having a thin plate shape of 15 mm in length, 1.5 mm in width, and 0.2 mm in thickness were manufactured.

  Next, in order to evaluate the performance of the cold cathode fluorescent tube electrode 3 obtained in the present example, a pair of cold electrodes 3 provided with a pair of the electrodes 3 is provided inside the glass tube 2 whose inner wall surface is coated with a phosphor. A cathode fluorescent tube 1 was manufactured.

  First, a sealing pin 4 made of a Kovar wire is connected to the end portion of the pair of cold cathode fluorescent tube electrodes 3 obtained in this embodiment, and the end portion of the sealing pin 4 opposite to the electrode 3 is connected. An external lead wire 5 made of a jumet wire was connected to Glass beads (not shown) for sealing with the glass tube 2 are attached to the sealing pins 4.

  Next, the cold cathode fluorescent tube electrodes 3 to which the sealing pins 4 were connected were attached to both ends of the glass tube 2 having a diameter of 3 mm, on which the phosphor was coated on the inner wall surface. At this time, the pair of cold cathode fluorescent tube electrodes 3 was attached in the axial direction so that the end portions on the side where the sealing pins 4 were not connected face each other.

  Next, after sealing Hg vapor, Ar gas, and Ne gas inside the glass tube 2, the sealing pin 4 and the glass tube 2 were sealed. At this time, the cold cathode fluorescent tube 1 was manufactured by projecting the sealing pin 4 outward of the glass tube 2.

  Next, with respect to the obtained cold cathode fluorescent tube 1, a tube current of 5 mA, 6 mA, 7 mA, and 8 mA was applied between the pair of electrodes 3, and the tube voltage generated for each tube current was applied. It was measured. The results are shown in FIG.

  Next, a pair of cold cathode fluorescent tube electrodes was manufactured in exactly the same manner as in this example except that the electrode material of Reference Example 1 was used, and a cold cathode fluorescent tube (Reference Example 1) including the electrodes was manufactured. did. With respect to the obtained cold cathode fluorescent tube, tube currents of 5 mA, 6 mA, 7 mA and 8 mA were respectively applied between the pair of electrodes, and the tube voltage generated for each tube current was measured. The results are shown in FIG.

  Next, in order to evaluate the performance of the cold cathode fluorescent tube electrode 3 obtained in this example, a pair of cold electrodes 3 provided with a pair of the electrodes 3 is provided inside a glass tube whose inner wall surface is not coated with a phosphor. Cathode tube A was manufactured. For the cold cathode tube A, a glass tube in which the inner wall surface is not coated with a phosphor is used in consideration of the presence / absence of atoms sputtered from the cold cathode fluorescent tube electrode 3 and the convenience when examining the influence thereof. . That is, the cold cathode tube A is replaced with a glass tube having a diameter of 3 mm that is not coated with a phosphor on the inner wall surface, instead of the glass tube 2 having a diameter of 3 mm that is coated with a phosphor on the inner wall surface. Thus, it was manufactured exactly the same as the cold cathode fluorescent tube 1.

  Next, the cold cathode tube A was discharged for 300 hours under a constant 6 mA tube current, and then the cold cathode tube A was opened and the cold cathode fluorescent tube electrode 3 was taken out. Next, in order to examine the presence or absence of the sputtered atoms from the cold cathode fluorescent tube electrode 3 and the influence thereof, the composition of the surface of the cold cathode fluorescent tube electrode 3 and the composition of the inner wall surface of the glass tube were changed to It measured with the analyzer (EPMA: Electron Probe Micro Analyzer). The results are shown in Table 2. Table 2 shows the presence or absence of mercury atoms on the surface of the cold cathode fluorescent tube electrode 3 and the inner wall of the glass tube.

  Next, a pair of cold cathode fluorescent tube electrodes was manufactured in exactly the same manner as in this example except that the electrode material of Reference Example 1 was used, and a cold cathode tube (Reference Example 1) B provided with the electrodes was manufactured. did. About the obtained cold cathode tube B, it carried out exactly the same as Example 1, and measured the composition of the surface of the electrode for cold cathode fluorescent tubes, and the composition of the inner wall surface of a glass tube by EPMA. The results are shown in Table 2.

  Next, in order to evaluate the workability of the electrode material of this example, a tensile test was performed. First, hot forging is performed on the ingot obtained in this example at a temperature of 1100 ° C., and cold rolling at room temperature and annealing at a temperature of 800 ° C. in a hydrogen atmosphere are repeated in this order. After performing the annealing at 800 ° C. for 10 minutes in a hydrogen atmosphere, a round bar test piece was prepared by cooling to room temperature. The round bar test piece has a small-diameter portion as a parallel portion and large-diameter portions at both ends, and the parallel portion has a length of 24 mm and a diameter of 8 mm.

Next, the round bar test piece was subjected to a tensile test at a tensile speed of 24 mm / second and measured for tensile strength, which was 502 N / mm ² . Furthermore, when the length and diameter of the parallel part of the round bar test piece after the tensile test were measured and the elongation and the drawing by the tensile test were calculated, the elongation was 34.9% and the drawing was 59.6%. The results are shown in Table 3.

Next, a round bar test piece (Reference Example 1) was prepared from the electrode material of Reference Example 1, and was subjected to a tensile test in exactly the same manner as in this example to measure the tensile strength and calculate elongation and drawing. However, the tensile strength was 361 N / mm ² , the elongation was 18.8%, and the aperture was 6.4%. The results are shown in Table 3.
[Comparative Example 1]
Next, a test piece was manufactured in the same manner as in Example 1 for the electrode material substantially made of Mo except for inevitable impurities, and the amount of consumption by sputtering in the electrode material was calculated. The consumption amount of the electrode material obtained in this comparative example was 83.4% of the electrode material of Reference Example 1. The results are shown in Table 1 as the sputtering rate.

  Next, a pair of cold cathode fluorescent tube electrodes was manufactured in the same manner as in Example 1 except that the electrode material of this comparative example was used, and a cold cathode fluorescent tube including the electrodes was manufactured. With respect to the obtained cold cathode fluorescent tube, tube currents of 5 mA, 6 mA, 7 mA and 8 mA were respectively applied between the pair of electrodes, and the tube voltage generated for each tube current was measured. The results are shown in FIG.

  Next, a pair of cold cathode fluorescent tube electrodes was manufactured in the same manner as in Example 1 except that the electrode material of this comparative example was used, and a cold cathode tube C including the electrodes was manufactured. About the obtained cold cathode tube C, it carried out exactly the same as Example 1, and measured the composition of the surface of the electrode for cold cathode fluorescent tubes, and the composition of the inner wall surface of a glass tube by EPMA. The results are shown in Table 2.

Next, a round bar test piece was prepared from the electrode material of this comparative example, the tensile test was performed in exactly the same manner as in Example 1, the tensile strength was measured, and the elongation and the drawing were calculated. 335 N / mm ² , elongation 2.4%, aperture 1.6%. The results are shown in Table 3.
[Comparative Example 2]
Next, a pair of cold cathode fluorescent tube electrodes was manufactured in the same manner as in Example 1 except that the inevitable impurities were substantially composed of Fe, and a cold cathode fluorescent tube including the electrodes was manufactured. With respect to the obtained cold cathode fluorescent tube, tube currents of 5 mA, 6 mA, 7 mA and 8 mA were respectively applied between the pair of electrodes, and the tube voltage generated for each tube current was measured. The results are shown in FIG.

  Next, a pair of cold cathode fluorescent tube electrodes was manufactured in the same manner as in Example 1 except that the electrode material of this comparative example was used, and a cold cathode tube D including the electrodes was manufactured. About the obtained cold cathode tube D, it carried out exactly the same as Example 1, and measured the composition of the surface of the electrode for cold cathode fluorescent tubes, and the composition of the inner wall surface of a glass tube by EPMA. The results are shown in Table 2.

  From Table 1, the sputtering of the electrode material of Example 1 in which the Mo content is 3.4% by mass, the Nb content is 1.6% by mass, and the balance is substantially Fe. It is clear that the amount of wear due to is smaller than that of the electrode material of Comparative Example 1 substantially made of Mo. Therefore, it is clear that the electrode material of Example 1 has a low sputtering rate and has excellent sputtering resistance.

  From Table 2, it is clear that in the cold cathode fluorescent lamp A provided with the cold cathode fluorescent tube electrode 3 of Example 1, Hg atoms are not present on the surface of the electrode 3 and the inner wall surface of the glass tube. Accordingly, in the cold cathode tube A, Fe atoms constituting the cold cathode fluorescent tube electrode 3 are slightly sputtered, but Fe and Hg are formed on both the surface of the electrode 3 and the inner wall surface of the glass tube. It is clear that an alloy (amalgam) is not formed. Thus, it is clear that the cold cathode tube A can extend the life of the cold cathode tube A without depleting Hg vapor in the glass tube due to amalgam formation.

  On the other hand, in the cold cathode fluorescent lamp B provided with the cold cathode fluorescent tube electrode of Reference Example 1, 87% by mass of Hg atoms are present on the surface of the electrode, and 21% by mass of Hg atoms are present on the inner wall surface of the glass tube. It is clear that Therefore, it is clear that in the cold cathode tube B, Ni atoms constituting the cold cathode fluorescent tube electrode are sputtered, and an amalgam composed of Ni and Hg is formed on the surface of the electrode. Accordingly, it is apparent that the cold cathode tube B consumes Hg vapor in the glass tube due to amalgam formation, and the life of the cold cathode tube B is shortened.

  Further, in the cold cathode tube D provided with the cold cathode fluorescent tube electrode of Comparative Example 2, Hg atoms are present on the surface of the electrode, although Hg atoms are not present on the inner wall surface of the glass tube. Obviously. Therefore, it is apparent that in the cold cathode tube D, Fe atoms constituting the cold cathode fluorescent tube electrode are sputtered, and an amalgam composed of Fe and Hg is slightly formed on the surface of the electrode. Accordingly, it is apparent that the cold cathode tube D consumes the Hg vapor in the glass tube due to amalgam formation, and the life of the cold cathode tube D is shortened compared to the cold cathode tube A.

  From Table 3, it is clear that the tensile strength of the electrode material of Example 1 is larger than that of Comparative Example 1. Therefore, it is clear that the electrode material of Example 1 has excellent strength. Further, from Table 3, it is clear that the elongation and restriction of the electrode material of Example 1 are much larger than those of Comparative Example 1. Therefore, it is clear that the electrode material of Example 1 has excellent workability.

  Further, from FIG. 1, the cold cathode fluorescent tube electrode 3 of Example 1 is substantially the same as that of Reference Example 1 made of Ni although the Mo content is as small as 3.4% by mass with respect to the total amount. It is clear that the tube voltage is smaller than that of the cathode fluorescent tube electrode, and the tube voltage is substantially similar to the cold cathode fluorescent tube electrode of Comparative Example 1 made of Mo. Therefore, it is clear that the cold cathode fluorescent tube electrode 3 of Example 1 has a small tube voltage and good energy efficiency.

  1 ... Cold cathode fluorescent tube, 3 ... Cold cathode fluorescent tube electrode.

Claims (2)

  It is characterized by comprising Mo in the range of 0.1 to 30% by mass and Nb in the range of 0.1 to 6% by mass with the balance being Fe and an unavoidable impurity with respect to the total amount. An electrode for a cold cathode fluorescent tube.   For cold cathode fluorescent tubes comprising Mo in the range of 0.1 to 30% by mass and Nb in the range of 0.1 to 6% by mass with the balance being Fe and an unavoidable impurity with respect to the total amount A cold cathode fluorescent tube comprising an electrode.