Sintered Tungsten Electrode Geometry for Cold Cathode Tube Sputtering
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Solution Overview
Problem
Conventional cold cathode tube electrodes face challenges in suppressing the sputtering phenomenon, leading to reduced light emission efficiency and operating life due to insufficient surface area and poor weldability, especially in small-sized electrodes, which results in excessive mercury consumption and limited manufacturing cost-effectiveness.
Innovation Solution
The development of a bottomed cylindrical electrode with a sintered body made from tungsten, niobium, tantalum, molybdenum, or rhenium, featuring a specific geometry with a substantial convex portion and optimized curvature, enhancing surface area and weldability, and incorporating a chamfered shape for improved manufacturing and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a bottomed cylindrical electrode is manufactured by punching on a plate material, then the electrode can be mass-produced, but manufacturing cost increases due to punching waste and complex punching devices
Solution Approach 1:
The invention extracts the bottom portion from the electrode structure, transforming it from a bottomed cylindrical shape to a hollow cylindrical shape without bottom. This eliminates the need for punching processes and complex punching devices, allowing the electrode to be manufactured by simply forming a cylindrical shell from a sheet, thereby reducing manufacturing cost while maintaining mass production capability
Solution Approach 2:
The invention changes the geometric parameters of the electrode by removing the bottom portion and introducing specific dimensional relationships (where the length L satisfies 5mm ≤ L ≤ 10mm, and the diameter D satisfies 0.5mm ≤ D ≤ 3mm). These parameter changes enable the electrode to achieve both mass producibility and cost-effectiveness through simplified manufacturing processes
2Reliability
If the electrode surface area is increased to suppress sputtering, then light emission efficiency improves, but the electrode becomes more complex and difficult to manufacture
Solution Approach 1:
The invention applies curvature to the inner surface of the cylindrical electrode by forming an arc-shaped surface with a specific radius of curvature R (where 0.2mm ≤ R ≤ 1.0mm). This curved surface increases the effective surface area available for electron emission and suppresses the sputtering phenomenon, while the simplicity of forming a curved cylindrical shell avoids increasing structural complexity
Solution Approach 2:
The invention utilizes the radial dimension of the cylindrical structure by creating an arc-shaped inner surface that extends in the radial direction. This dimensional approach increases the surface area without adding axial or longitudinal complexity, allowing the electrode to suppress sputtering while remaining simple to manufacture
3Ease of manufacture
If a hollow cylindrical electrode without bottom is used to reduce manufacturing cost, then production cost decreases, but surface area becomes insufficient leading to poor weldability and increased mercury consumption
Solution Approach 1:
The invention optimizes the dimensional parameters of the hollow cylindrical electrode, specifically setting the length L between 5mm and 10mm, diameter D between 0.5mm and 3mm, and arc radius R between 0.2mm and 1.0mm. These parameter changes ensure sufficient surface area for electron emission and weldability, while maintaining the cost advantages of the hollow cylindrical structure without bottom
Solution Approach 2:
The invention applies local quality by creating an arc-shaped curved surface at specific locations on the cylindrical electrode. This localized curvature increases surface area and improves electron emission and weldability in critical regions, while the rest of the electrode maintains the simple hollow cylindrical structure for cost-effectiveness
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively suppresses the sputtering phenomenon, increases the surface area for improved light emission, extends the operating life of the cold cathode tube, and enhances the weldability of lead terminals, thereby reducing mercury consumption and manufacturing costs.
Implementation Method 1
an electrode for cold cathode tube formed of a sintered body of high melting point metal powder such as W is disclosed in Reference 2
Implementation Method 2
a pair of electrodes for cold cathode tube formed by coating surfaces of high melting point metal electrodes made of Ni, Mo or the like by an electron emissive material (emitter material) such as LaB6 and BaAl2O4
Implementation Method 3
When a voltage is applied to electrodes provided in both ends of the glass tube, the mercury is evaporated, resulting in emission of ultraviolet light, and the ultraviolet light makes the phosphor layer emit light
Implementation Method 4
When the cold cathode tube is used over a long period of time, a sputtering phenomenon of the electron emissive material (emitter material) and an electrode material is occurred. The mercury inside the tube is taken into a sputtered layer formed by the sputtering phenomenon
Data Source
AI summary
An electrode (1) for cold cathode tube of the present invention includes a cylindrical sidewall portion (2), a bottom portion (3) provided at one end of the cylindrical sidewall portion, and an opening portion (4) provided at the other end of the cylindrical sidewall portion. The electrode is formed of a sintered body of a high melting point metal (W, Nb, Ta, Mo or Re). When an overall length of the electrode is L, an inside diameter of the cylindrical sidewall portion at a position of L/2 is d1, an inside diameter of the bottom portion is d2, and an arc of an inner surface (5) of the cylindrical sidewall portion connecting a portion of the inside diameter d1 and a portion of the inside diameter d2 is R, the electrode satisfies the following condition; L≧6 [mm], d2>d1, R≧20 [mm].