Interior-Light Display Using Refractive Index Gradients
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Solution Overview
Problem
Existing signboards using external light sources face challenges in maintaining constant display characteristics as the incident angle of light changes, and they are ineffective in utilizing interior light sources, such as those from trains or buses, especially at night.
Innovation Solution
An interior-light-utilizing display is created by laminating a reflection structure and a light diffusion film with a specific internal structure, including regions of high and low refractive index, to efficiently diffuse and reflect light over a wide angle range, allowing recognition as a station name signboard both day and night without external power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If external light sources are used for signboards, then the signboard can be recognized during daytime, but the display characteristics become unstable when the incident angle of light changes and the signboard is ineffective at night
Solution Approach 1:
The signboard structure is designed to perform multiple functions: it can utilize both external light sources (sunlight) during daytime and internal light sources (vehicle interior lights) at night. The combination of light diffusion film and reflection structure enables the signboard to adapt to different lighting conditions and time periods, making it universally effective both day and night without requiring separate signaling systems.
Solution Approach 2:
The optical parameters of the signboard are optimized by controlling the incident angle range of light (α) to be 5° or more, and the emission angle range (β) to be 35° or more. By adjusting these angular parameters and the refractive index distribution, the signboard maintains stable display characteristics across varying light incident angles and effectively utilizes interior light sources at night.
2Loss of energy
If retroreflective materials are used, then light can be reflected back to the source, but the display is only effective in a narrow angle range close to the front face and cannot utilize interior light sources
Solution Approach 1:
Instead of using uniform retroreflective materials that only work in narrow angles, the invention employs a light diffusion film with spatially varying refractive index distribution. Different regions of the film have different optical properties, enabling light to be diffused and reflected across a wide viewing angle range (β ≥ 35°) while maintaining efficient utilization of interior light sources from various directions.
Solution Approach 2:
Rather than relying on retroreflection that sends light back along the incident path, the invention inverts the approach by using a reflection structure combined with light diffusion to emit light in a wide forward direction. This allows interior light sources to be effectively utilized and displays to be visible from broad viewing angles, fundamentally changing how light is managed in the signboard system.
3Illumination intensity
If light diffusion films with fine particles are used, then light can be scattered, but the display characteristics change when the incident angle of external light changes
Solution Approach 1:
The invention uses a composite structure combining a light diffusion film with a reflection structure. The light diffusion film contains fine particles dispersed in a resin to scatter light, while the reflection structure behind it reflects both external and internal light sources. This composite design ensures that display characteristics remain consistent across different incident angles by providing multiple light interaction mechanisms, enabling stable display whether illuminated by sunlight or interior lights.
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 ensures stable and increased luminance of the display, enabling clear recognition from various angles and distances, even in moving vehicles, with constant brightness and sharpness, utilizing interior light sources effectively.
Implementation Method 1
a light diffusion film with a specific internal structure, including regions of high and low refractive index, to efficiently diffuse and reflect light over a wide angle range
Implementation Method 2
the light diffusion film has an internal structure including a plurality of regions having a relatively high refractive index in a region having a relatively low refractive index
Implementation Method 3
laminating a reflection structure and a light diffusion film... to efficiently diffuse and reflect light
Data Source
AI summary
In various embodiments, the present invention is directed to an interior-light-utilizing display obtained by laminating a reflection structure and a light diffusion film, in which the light diffusion film has an internal structure including a plurality of regions having a relatively high refractive index in a region having a relatively low refractive index in the film. The interior-light-utilizing display provides improved luminance and is capable of stably maintaining constant display characteristics even where the incident angle of the external light changes.