White-Coated LED Filament Coating for Stable Light Distribution

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Solution Overview

Problem

The existing production process of white coated LED filament bulbs is complex, costly, and the white coated layer on glass shells is unstable, prone to color bleaching, and has inconsistent photoelectric parameters.

Innovation Solution

A white coated LED filament with a substrate, LED chips, and a package layer, where the white coated layer is applied directly on the filament surface, using materials like silica gel or titanium dioxide, and a simplified production process involving painting and drying steps to form a stable white coated layer.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a traditional LED filament structure is used, then the manufacturing process is simple, but the light distribution is uneven and the filament is prone to breakage

Engineering Contradiction:
Improvefilament breakage resistanceVSAvoidfilament structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The filament is divided into multiple segments with different coating layers (white coating layer, reflective layer, transparent protective layer) applied to different portions. This segmentation allows each segment to serve specific functions: the white coating diffuses light, the reflective layer redirects light, and the transparent layer protects the structure, thereby improving reliability without excessive complexity

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

Different portions of the filament are given different local properties through selective coating. The white coating layer is applied to specific sections to diffuse light in those areas, while reflective layers are applied to other sections to redirect light. This local differentiation improves overall filament performance and breakage resistance while maintaining reasonable structural complexity

Inventive Principle:
Principle #3Local quality

2Illumination intensity

If a simple LED filament structure is used, then the device complexity is low, but the light distribution is uneven

Engineering Contradiction:
Improvelight distribution uniformityVSAvoidfilament structure complexity
Core Design Contradiction:
Illumination intensityVSDevice complexity

Solution Approach 1:

The filament employs local quality by applying white coating layers to specific segments rather than uniformly coating the entire filament. This selective application creates localized light diffusion zones that work together to achieve uniform overall light distribution, balancing illumination quality with structural simplicity

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The filament structure is segmented into multiple sections with alternating white coating layers and reflective layers. This segmentation creates a pattern of light diffusion and reflection zones that collectively produce uniform light distribution, improving illumination quality while maintaining manageable device complexity

Inventive Principle:
Principle #1Segmentation

3Illumination intensity

If the LED filament operates at high power, then the brightness is high, but the color temperature shifts and efficiency drops

Engineering Contradiction:
ImprovebrightnessVSAvoidcolor temperature stability
Core Design Contradiction:
Illumination intensityVSTemperature

Solution Approach 1:

The white coating layer changes the optical parameters of the filament by diffusing light and modifying its spectral distribution. This parameter change allows the filament to maintain stable color temperature across different power levels, as the coating acts as a spectral stabilizer that prevents color shifting even when brightness varies

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The filament uses composite material structure with multiple coating layers (white coating, reflective layer, transparent protective layer) applied to the quartz glass substrate. This composite structure enables the filament to maintain stable color temperature and high efficiency at high power levels by combining the optical properties of different materials that work synergistically to manage light emission and heat distribution

Inventive Principle:
Principle #40Composite materials

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 approach simplifies the production process, reduces costs, stabilizes the white coated layer, and improves photoelectric parameters, enhancing the filament's performance and market competitiveness.

Implementation Method 1

the filament is wrapped with a layer of white coating to diffuse the light

Methodology Applied
Scientific EffectLight diffusion: Scattering

Implementation Method 2

a layer of reflective material is applied to a portion of the filament between the first and second ends

Methodology Applied
Scientific EffectLight reflection: Reflection

Implementation Method 3

a transparent protective coating is applied over the filament

Methodology Applied
Scientific EffectLight transmission through transparent material: Refraction

Data Source

PatentEP4407700B1White-coated LED lamp filament and manufacturing process therefor, and LED bulb
Publication Date: 2026.01.21 MLS CO LTD
  • EP4407700B1 patent drawingFigure 1
  • EP4407700B1 patent drawingFigure 2
  • EP4407700B1 patent drawingFigure 3

AI summary

The present invention provides a white coated LED filament and its production process and LED bulb, optimizing the white coated powder from being painted originally on internal surface of the glass shell to be painted on the surface of the filament, thus forms a coated white layer on the surface of the filament, and bonds whit the filaments for one-time molding, which simplifies the existing internal powder painting process of the glass shells, and reduces the cost of the finished products in terms of the usage and production of the clients, and also greatly improving the stability of the white coated filament bulbs, so that the color bleaching and its photoelectric parameters are in a manageable state, therefore the production process is become simply, the cost is lower, and improve the clients' usage scope, reduce the clients' usage cost, and can satisfy the existing market client's requirements for the product of the filaments bulbs with white coated.