Cold Cathode Fluorescent Lamp Phosphor Film UV Reflection
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Solution Overview
Problem
The existing cold cathode fluorescent lamps in liquid crystal display devices suffer from low light emission efficiency due to ultraviolet rays being absorbed by the glass tube rather than contributing to phosphor light emission, and the phosphor film's structure leads to gaps between particles, reducing film strength and causing peeling issues.
Innovation Solution
A phosphor film is formed on the inner surface of the glass tube using a suspension of phosphors mixed with butyl acetate and nitrocellulose, with an ultraviolet-ray reflection film interposed between the glass tube and the phosphor film to reflect and re-emit ultraviolet rays, enhancing light emission efficiency and film strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a phosphor film is formed by coating phosphors with particle size of 2 μm to 5 μm and dispersing agents in a solution, then the maximum light emission brightness can be acquired, but ultraviolet rays pass through gaps between phosphor particles and are absorbed by the glass tube, lowering light emission efficiency
Solution Approach 1:
The patent changes the particle size parameter of phosphors from 2-5 μm to 0.5-2 μm, which reduces the gaps between particles and prevents ultraviolet ray transmission. This parameter change simultaneously maintains light emission brightness while improving light emission efficiency by preventing energy loss through the glass tube.
Solution Approach 2:
The patent uses a composite binder system comprising both a resin binder and a colloidal binder in the phosphor suspension. This composite material approach creates a more effective film structure that fills gaps between phosphor particles, preventing ultraviolet transmission while maintaining the desired optical properties for light emission.
2Illumination intensity
If phosphor particles are dispersed in a solution with dispersing agents to form a phosphor film, then light emission can be achieved, but the film strength is lowered and the phosphor film is easily peeled off
Solution Approach 1:
The patent employs a composite binder system combining resin binder and colloidal binder. The resin binder provides structural strength and adhesion to the glass tube, while the colloidal binder ensures proper dispersion of phosphor particles. This composite approach simultaneously achieves light emission functionality and mechanical strength to prevent peeling.
Solution Approach 2:
The patent optimizes the concentration ratio of resin binder to colloidal binder in the phosphor suspension. By adjusting these concentration parameters, the film achieves adequate adhesion strength to prevent peeling while maintaining the necessary optical properties for light emission.
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 configuration significantly reduces ultraviolet-ray transmissivity, increases light emission brightness, and enhances the luminous flux of the cold cathode fluorescent lamp, improving the backlight's brightness and reducing material costs while stabilizing the phosphor film against peeling.
Implementation Method 1
an ultraviolet-ray reflection film interposed between the glass tube and the phosphor film to reflect and re-emit ultraviolet rays
Implementation Method 2
mercury and a rare gas are sealed in the inside of the glass tube. By generating an electric discharge in the inside of the glass tube, ultraviolet rays mainly having a wavelength of approximately 254 nm are generated by excitation radiation of mercury thus exciting phosphors with the ultraviolet rays whereby visible light is radiated
Data Source
AI summary
A cold cathode fluorescent lamp for a backlight of a liquid crystal display device includes a light-transmitting glass tube in which a rare gas and mercury are sealed, and a phosphor film which is formed on an inner peripheral surface of the glass tube. The phosphor film is formed such that a phosphor suspension is formed by mixing phosphors into a suspension produced by strongly stirring a mixed solvent made of butyl acetate and nitrocellulose and by re-stirring the mixture, and the phosphor suspension is applied to the inner peripheral surface of the glass tube by coating.