Ceramic Phosphor Plate Surface and AR Film for Uniform White Light
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Solution Overview
Problem
Existing ceramic phosphor plates experience issues with color unevenness and low light extraction efficiency due to surface roughness, which affects the uniformity and brightness of white light emission in LED lighting.
Innovation Solution
A ceramic phosphor plate with a ceramic substrate having a light emitting surface featuring a concave and convex uneven shape, an arithmetic mean roughness (Ra) of 0.1 μm to 0.7 μm, and a Kurtosis (Rku) of 5 to 10, combined with an antireflection film of 500 nm to 700 nm thickness, composed of multiple layers with different refractive indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the surface roughness is made small to improve light extraction efficiency, then specular reflection increases making it difficult to extract incident light, but if the surface roughness is made large to prevent color unevenness, then diffuse reflection increases making it difficult to efficiently extract emitted light
Solution Approach 1:
The invention optimizes the surface roughness parameters (Ra and Rq values) to specific ranges (Ra: 0.001-0.1 μm, Rq: 0.003-0.03 μm) to achieve the balance between preventing color unevenness and maintaining efficient light extraction. This parameter optimization resolves the contradiction by finding the precise value that satisfies both requirements.
Solution Approach 2:
The invention applies different surface treatment conditions to different regions of the ceramic phosphor plate surface. The first surface (light incident surface) has different roughness characteristics compared to the second surface (light emitting surface), with each surface optimized for its specific function. This local differentiation allows each surface to perform optimally without compromising the other.
2Manufacturing precision
If an antireflection film is formed on a surface with uneven shape to reduce reflection, then color unevenness occurs due to light reflection inside convex portions, but if the surface is made flat to prevent color unevenness, then light extraction efficiency decreases
Solution Approach 1:
The invention specifies precise surface roughness parameters (Ra: 0.001-0.1 μm, Rq: 0.003-0.03 μm) that balance surface flatness with light extraction efficiency. These controlled parameters prevent excessive surface unevenness that would cause color unevenness while maintaining sufficient surface features for efficient light extraction.
Solution Approach 2:
The invention applies a moderate level of surface treatment rather than complete flattening. By controlling the surface roughness within specific ranges rather than achieving perfect flatness, the invention maintains partial surface features that aid light extraction while preventing excessive unevenness that would cause color variations.
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
The solution effectively prevents color unevenness and enhances light extraction efficiency, improving the uniformity and brightness of white light emission.
Implementation Method 1
white light is obtained by wavelength conversion of light emitted from a light emitting diode (LED) or a laser diode (LD)
Implementation Method 2
an antireflection film formed at least on the light emitting surface
Data Source
AI summary
The present invention relates to a ceramic phosphor plate including: a ceramic substrate having a light incident surface and a light emitting surface facing the light incident surface; and an antireflection film formed at least on the light emitting surface, in which the light emitting surface of the ceramic substrate has an uneven shape including a concave portion and a convex portion, the light emitting surface has an arithmetic mean roughness (Ra) of 0.1 μm or more and 0.7 μm or less, and a Kurtosis (Rku) obtained from a surface roughness curve of 5 or more and 10 or less.