JP2007220669A - Alloy for cold-cathode discharge tube electrode, electrode for cold-cathode discharge tube, and cold-cathode discharge tube for backlight for liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alloy for an electrode capable of solving problems of plastic workability in a conventional Ni-Nb alloy for an electrode and surface oxidation occurring in processing glass sealing or the like, and of providing spatter resistance equivalent to that of the conventional Ni-Nb alloy for an electrode. <P>SOLUTION: This alloy for a cold-cathode discharge tube electrode comprises 1.0-10.0 mass% of V, 3.0-15.0 mass% of Mo, and Ni as substantially the whole of the residual. Its preferable chemical composition is 3.0-8.5 mass% of V, 5.0-13.0 mass% of Mo and not greater than 30.0 mass% of 2.9V+Mo. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an alloy for a cold cathode discharge tube electrode used as, for example, a light source for a backlight of a liquid crystal display device, an electrode for a cold cathode discharge tube using the alloy for a cold cathode discharge tube electrode, and an electrode for the cold cathode discharge tube The present invention relates to a cold cathode discharge tube for a backlight for a liquid crystal display.

Conventionally, a backlight for illumination is incorporated in a liquid crystal display (LCD) used in a television or a personal computer (personal computer), and a cold cathode discharge tube is used as a light source of the backlight. The cold cathode discharge tube has a structure in which a pair of electrodes are arranged facing each other inside a glass tube filled with a rare gas and mercury vapor, and an inner wall of the glass tube is covered with a fluorescent film. One end of a lead is connected to the pair of electrodes, and the other end of the lead is led out from both ends of the glass tube. When a voltage is applied between the pair of electrodes via the lead, electrons are emitted from one electrode, and the electrons collide with mercury atoms in the glass tube to generate ultraviolet rays. This ultraviolet ray is converted into visible light by a fluorescent film coated on the inner wall of the glass tube, and plays a role as illumination.
FIG. 1 shows a cross-sectional view of an example of an electrode part (4) for a cold cathode discharge tube. The structure of the cold cathode discharge tube electrode component (4) includes: a cold cathode discharge tube electrode (1) formed by deep-drawing plastic alloy of a cold cathode discharge tube electrode, a glass sealing metal part (2), It is comprised with a lead part (3).

  The cold cathode discharge tube electrode (1) (hereinafter referred to as an electrode) often uses a thin plate-shaped material formed into a cup shape by cold plastic working such as deep drawing. Therefore, conventionally, a pure Ni thin plate that is soft and has excellent plastic workability has been used. However, there is a problem that an electrode made of pure Ni is consumed by sputtering while being used for a long time, leading to a life. Since the life of this electrode depends on the sputtering resistance of the material constituting the electrode (difficult to be consumed by sputtering), proposals have been made to improve the sputtering resistance of the electrode material.

  In addition, in order to improve the spatter resistance, Mo and Nb materials, which are high melting point pure metals, have been used in some of the cup-shaped electrodes. However, these high melting point pure metals are expensive and have high cups. There was a drawback that the productivity of the process of plastic processing into a shape was low.

In order to solve these drawbacks, for example, Japanese Patent Application Laid-Open No. 2005-93119 (Patent Document 1) describes Ni--containing Nb in an amount of 6% to less than 32% by mass and the balance being substantially Ni. Proposals have been made to use Nb alloys as electrodes. This proposal is superior in that an electrode superior in sputtering resistance to an electrode made of pure Ni can be provided by alloying Nb, which is less likely to be consumed by sputtering than Ni, with Ni.
JP 2005-93119 A

  According to studies by the present inventors, the Ni—Nb alloy for electrodes disclosed in Patent Document 1 described above has an advantage that corrosion resistance is superior to pure Ni in addition to sputtering resistance. Corrosion resistance is one of the important characteristics of an electrode of a cold cathode discharge tube used for a long period of several years or more. Therefore, Nb is suitable as an element to be alloyed with Ni.

However, in the Ni—Nb alloy for electrodes disclosed in Patent Document 1, the Nb content is as high as 6% by mass or more, and in this range, brittle intermetallic compound (Ni ₃ Nb) is generated, and the material is cup-shaped. There is a problem of adversely affecting cold plastic workability, which is a process of forming an electrode. Therefore, although the Ni—Nb alloy for electrodes disclosed in Patent Document 1 is excellent in spatter resistance, the plastic workability in the process of forming the material into a cup shape is poor, and it is difficult to produce the electrode itself. There is a drawback. In addition, in Ni-Nb alloy, discoloration due to surface oxidation is likely to occur in processing steps such as welding of lead wires and glass sealing after electrode processing, and when excessive coloring occurs, an oxide layer formed on the surface Discharge characteristics may deteriorate.

  The object of the present invention is to solve the problems of plastic workability in the above-described conventional Ni-Nb alloy for electrodes and surface oxidation that occurs during processing such as glass sealing, and is equivalent to the conventional Ni-Nb alloy for electrodes. It is an object to provide an alloy for an electrode capable of obtaining sputtering resistance.

As a result of studying various Ni alloys, the present inventors have found an electrode material that can satisfy sputtering resistance, surface oxidation, and plastic workability by adding Mo and V to Ni, and have reached the present invention.
That is, in the present invention, V: 1.0% to 10.0% by mass, Mo: 3.0% to 15.0%, and the balance is substantially made of Ni. 2.9V + Mo: 35.0% An alloy for cold cathode discharge tube electrodes satisfying the following.
The preferred composition is an alloy for cold cathode discharge tube electrodes in which V: 3.0% to 8.5%, Mo: 5.0% to 13.0%, 2.9V + Mo: 30.0% or less in mass%. is there.
Moreover, this invention is an electrode for cold cathode discharge tubes which uses said alloy material for electrodes.
Furthermore, the present invention is a cold cathode discharge tube for a backlight for a liquid crystal display comprising the cold cathode discharge tube electrode.

  The alloy for electrodes of the present invention is economically advantageous because the refractory metal content is small. In addition to having the same spatter resistance as that of a conventional Ni—Nb alloy having excellent sputter resistance, and having a plastic workability superior to that of a conventional Ni—Nb alloy, a cup-shaped electrode In the process of manufacturing a cold cathode discharge tube, discoloration is difficult to occur by suppressing surface oxidation when the electrode passes through an atmosphere where it is easily oxidized. It has the effect which suppresses deterioration of.

An important feature of the present invention is that V is effective in improving the spatter resistance while maintaining the excellent plastic workability of Ni, and an excessive coloring due to surface oxidation in addition to the effect of improving the spatter resistance. It has a novel chemical composition in which Mo is added in combination with the effect of preventing discharge and suppressing the deterioration of discharge characteristics.
The reasons for defining chemical components in the electrode alloy of the present invention will be described below. Unless otherwise specified, the mass% is indicated.

V: 1.0% to 10.0%
V is an essential element of the present invention that improves sputtering resistance by alloying with Ni. In particular, in the present invention, Mo which improves the sputtering resistance together with V is essential, but the effect of improving the sputtering resistance is larger for V, and the essential addition is required when V is in the range of 1 to 10%.
However, if the amount of V exceeds 10%, brittle intermetallic compounds are likely to be formed, so the upper limit of the amount of V was set to 10.0%. In addition, when the V amount is less than 1%, the effect of improving the sputtering resistance is small even by the combined addition with Mo, so the lower limit value of the V amount was set to 1.0%. A preferable range of V is V: 3.0% to 8.5%, and a more desirable range is 3.0% to 6.0%.

Mo: 3.0% to 15.0%
In addition to the effect of improving the spatter resistance by alloying with Ni in the same way as V, Mo suppresses excessive coloring due to surface oxidation, for example, in the processing step during welding of lead wires or glass sealing. Is an essential element of the present invention necessary for obtaining the effect of preventing the discoloration of the glass and suppressing the deterioration of the discharge characteristics. Mo needs to be 3.0 to 15.0% in order to achieve both the spatter resistance and the effect of suppressing excessive coloring due to surface oxidation and suppressing the deterioration of discharge characteristics.
However, if the Mo amount exceeds 15.0%, the plastic workability deteriorates due to an increase in hardness due to work hardening, so the upper limit of the Mo amount was set to 15.0%. Moreover, the lower limit of the amount of Mo is set to 3.0% because the effect of improving the sputtering resistance is small if it is less than 3.0%. A preferable range of Mo is 5.0% to 13.0%, and a more desirable range is 5.5% to 10.0%.

In the present invention, it is necessary to adjust the contents of V and Mo within the above-described V and Mo component ranges. This is because if both V and Mo are increased, the hardness is likely to exceed 300 Hv, which hinders deep drawability.
The effect of increasing the hardness of V and Mo is not the same, and the effect of increasing the hardness of V is 2.9 times the effect of increasing the hardness of Mo. Therefore, the effect of increasing the hardness of V and Mo can be adjusted by 2.9V + Mo.
When the value of 2.9V + Mo exceeds 35.0%, the hardness becomes too high and the toughness is lowered. Therefore, in the present invention, the value of 2.9V + Mo is limited to 35.0% or less. A preferable range is 30.0% or less.
The lower limit is preferably set to 5.5% with a value of 2.9 V + Mo in consideration of the effect of suppressing coloring due to surface oxidation and the effect of improving the sputtering resistance.

The balance is essentially Ni
Although the balance is substantially Ni, inevitable impurities such as C, Si, Mn, P, and S are naturally included. These elements may be contained as unavoidable impurities within the ranges shown below as ranges that do not adversely affect the sputtering resistance and plastic workability of the electrode alloy.
C ≦ 0.10%, Si ≦ 0.50%, Mn ≦ 0.50%, P ≦ 0.05%, S ≦ 0.05%

The electrode alloy of the present invention exhibits a characteristic behavior of crystal grain size.
When the electrode alloy of the present invention is used to form a cup-shaped electrode, a hydrogen reduction heat treatment of about 1000 ° C. × 5 min is performed. Before and after this hydrogen reduction heat treatment, the electrode alloy of the present invention can suppress the coarsening of the crystal grain size.
A metal structure photograph (magnification 200 times) before hydrogen reduction annealing of the alloy for electrodes of the present invention is shown in FIG. 2, and a metal photograph after hydrogen reduction annealing at 1000 ° C. × 5 min is shown in FIG.
The electrode alloy of the present invention showed almost no change in crystal grain size before and after hydrogen reduction annealing, and had a fine metal structure with a crystal grain size of about 30 ** μm after hydrogen annealing. Note that the composition of the electrode alloy of the present invention shown in the metallographic photographs of FIGS. 3 alloys.

  In the electrode alloy of the present invention, the above configuration can ensure the spatter resistance equivalent to that of the conventional Ni—Nb alloy, and the effect of a long life can be obtained. Furthermore, since the plastic workability which has been a problem of the conventional Ni-Nb alloy can be improved, it has the effect that the plastic workability to the cup-shaped electrode is easy, and excessive coloring due to surface oxidation can be achieved. Therefore, it is suitable as an electrode alloy for a cold cathode discharge tube.

Since the electrode alloy of the present invention is excellent in plastic workability to a cup-shaped electrode, it can be easily processed into a cup shape, and a cold cathode discharge tube electrode (1) as shown in FIG. 1 can be obtained.
Moreover, it can be set as the electrode component for cold cathode discharge tubes (4) by combining the electrode (1) for cold cathode discharge tubes, the metal part (2) for glass sealing, and the lead part (3). And, if the cold cathode discharge tube for a liquid crystal display using the electrode component (4) for the cold cathode discharge tube has excellent spatter resistance, the cold cathode for the backlight for a liquid crystal display with a long life is obtained. It can be a discharge tube.

Example 1
Using a vacuum melting furnace, 10 kg each of seven types of electrode alloys having chemical components shown in Table 1 were prepared. No. in Table 1 1-4 (Ni-V-Mo alloy) are the alloys for electrodes of the present invention. On the other hand, no. No. 5 (Ni-V-Mo alloy) is a comparative alloy, No. 5, which does not satisfy the relational expression defined in the present invention. 6 (pure Ni) and no. 7 (Ni—Nb alloy) is a comparative example (conventional example). In addition, No. 7 corresponds to the electrode alloy disclosed in Patent Document 1.

Each alloy was heated to 1100 ° C. and subjected to hot forging and hot rolling to obtain a plate material having a thickness of 5 mm. From these plate materials, a target having a diameter of 75 mm and a thickness of 3 mm was prepared as a sample for evaluating the sputtering resistance.
These targets are installed in a vacuum chamber of a magnetron sputtering apparatus, and continuously sputtered for 12 hours under conditions of Ar pressure of 0.8 Pa and input power of 300 W. Then, the target is taken out from the chamber, and the amount of consumption of the target by sputtering (weight) Change).
Table 2 shows the ratio of consumption. In addition, No. The consumption amount of No. 6 is 100%. The lower the value, the less the consumption due to sputtering and the better the sputtering resistance.

  From Table 2, no. It can be seen that the consumption amount of the electrode alloy of the present invention is excellent when the consumption amount of 6 (pure Ni) is the standard (100%). Also, the electrode alloy No. 1 of the present invention. 3 and no. No. 4 is the No. of the comparative example (conventional example). It can be seen that almost the same spatter resistance as 7 (Ni—Nb alloy) can be obtained.

Next, the hardness of the produced alloy was measured and it was judged whether deep drawing could be performed easily.
The production of a test piece for hardness measurement was measured using an annealed material obtained in the following steps.
The remainder of the hot-rolled material was again heated to 1100 ° C. and hot-rolled to obtain a plate material having a thickness of 2.5 mm. After removing the oxide scale generated during hot rolling by pickling, it was softened by annealing in a vacuum furnace maintained at 800 ° C. for 1 hour. These plate materials were repeatedly subjected to cold rolling and annealing at 800 ° C. to obtain thin plate materials having a thickness of 0.2 mm. In the final step, after cold rolling at a reduction rate of 80%, annealing was performed in a vacuum furnace maintained at 800 ° C. for 30 minutes, and then quenched with N ₂ gas. Table 3 shows the measurement results of the hardness.

From Table 3, No. 1 of the present invention. 1-No. 4 and Comparative Example No. Since 6 (pure Ni) had a hardness of 300 Hv or less, it was determined that it could be formed into a cup shape by deep drawing. On the other hand, no. In No. 5, the hardness was as high as 365 Hv, and it was judged that deep drawing was very difficult.
No. 7 (Ni-Nb alloy) had a hardness of 285 Hv, but formation of a brittle intermetallic compound (Ni ₃ Nb) was confirmed by observation of the metal structure 400 times, and cracks occurred during deep drawing. It was judged that the processability to cup shape was bad.

Furthermore, after the remaining hot-rolled material was wire-cut, surface polishing (# 500 finishing) was performed to obtain a plate material having a thickness of 1 mm. The plate material was heated in the atmosphere for 1 hour in an electric furnace maintained at 350 ° C., and the surface state was visually observed.
Further, the reflectance of the test piece before and after heating was measured. For the measurement of reflectance, a spectrocolorimeter (manufactured by Minolta, CM-2002) was used, and the average reflectance in the visible light region (wavelength 400 to 700 nm) was measured. Table 4 shows the decrease in reflectance and the surface state before and after heating.

  From Table 4, it can be seen that the electrode alloy of the present invention has little decrease in reflectance. The electrode alloy of the present invention and No. No coloring was observed for No. 6 (pure Ni). 7 (Ni—Nb alloy) was confirmed to be light brown due to surface oxidation that promotes deterioration of discharge characteristics.

From the above examples, the electrode alloy of the present invention is No. of the comparative example (conventional example) excellent in sputtering resistance. It was confirmed that almost the same spatter resistance as 7 (Ni—Nb alloy) could be secured, and molding into a cup shape (plastic processing) was easy.
Further, it was found that excessive coloring due to surface oxidation can be suppressed and deterioration of discharge characteristics can be suppressed, and it was shown that the alloy is suitable as an electrode alloy for a cold cathode discharge tube.
It should be noted that the electrode alloy no. 3 and no. For 6 (pure Ni), the work function when electrons are emitted from the electrode (the smaller the value, the easier the electron emission occurs) was measured using atmospheric photoelectron spectroscopy. 4.10 eV (electrode alloy No. 3) and 4.17 eV (No. 6 pure Ni). It was superior to 6 (pure Ni).
Therefore, it was confirmed that the electrode made of the Ni-V-Mo alloy of the present invention can be practically used in terms of electron emission characteristics as compared with the pure Ni electrode which has been mainly used so far. .

(Example 2)
Next, in order to simulate an actual process, the above alloy No. 1 of the present invention is used. 3 (Ni-V-Mo alloy) annealed material and Using 6 (pure Ni) annealed material, consumption and discharge characteristics were measured and observed. The test piece used was 9 mm × 0.15 (t) mm.
First, consumption was measured. The sputtering conditions were DC 3 kV, 10 mA, and Ar. Under this condition, the consumption (volume) by sputtering for 5 hours was measured. As described above, the measurement results were excellent in consumption of the Ni-V-Mo alloy of the present invention. Table 5 shows the measurement results of the consumption amount.

Next, the discharge characteristics were measured. The discharge characteristics were as follows: test piece φ9 mm × 0.15 (t) mm as a cathode, held at a position of 100 mm distance from a stainless steel anode, and DC in both electrodes in an atmosphere of argon 1.33 × 10 ⁴ Pa. Measured by applying voltage. The discharge voltage when the discharge current is 10 mA is the same as that of the electrode alloy No. 1 of the present invention. 3 is 380V, No. 3 The discharge voltage of 6 (pure Ni) was 350V. As a result, the electrode alloy no. The discharge characteristics of No. 3 are No. 3. It was equivalent to the discharge characteristic of 6 (pure Ni).

  The electrode alloy of the present invention can be used over a long period of several years or more because it can suppress spatter resistance, plastic workability, and excessive coloration due to surface oxidation and suppress deterioration of discharge characteristics. Therefore, plastic processing to a cup shape is indispensable, and it can be applied as an electrode alloy for a cold cathode discharge tube in which surface oxidation hardly occurs in processing steps such as lead wire welding and glass sealing after electrode processing. For example, it is suitable for an electrode alloy of a cold cathode discharge tube used as a light source for a backlight of a liquid crystal display device.

It is a cross-sectional schematic diagram which shows an example of the electrode component for cold cathode discharge tubes. It is a metal structure photograph before hydrogen reduction annealing of the electrode alloy of the cold cathode discharge tube of the present invention. It is a metal photograph after 1000 degreeC x 5 min hydrogen reduction annealing of the electrode alloy of the cold cathode discharge tube of this invention.

Explanation of symbols

1. 1. Cold cathode discharge tube electrode 2. Metal part for glass sealing Lead part 4. Electrode parts for cold cathode discharge tubes

Claims (4)

In mass%, V: 1.0% to 10.0%, Mo: 3.0% to 15.0%, the balance is substantially made of Ni, and satisfies 2.9V + Mo: 35.0% or less. Characteristic alloy for cold cathode discharge tube electrodes. 2. The cooling according to claim 1, wherein in mass%, V: 3.0% to 8.5%, Mo: 5.0% to 13.0%, 2.9 V + Mo: 30.0% or less. Alloy for cathode discharge tube electrode. A cold cathode discharge tube electrode comprising the alloy material for a cold cathode discharge tube electrode according to claim 1 or 2. A cold cathode discharge tube for a backlight for a liquid crystal display, comprising the electrode for a cold cathode discharge tube according to claim 3.