Keypad Illumination Using Flexible Light Guide Film
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Solution Overview
Problem
Existing keypads in portable electronic devices face challenges in ensuring adequate illumination while maintaining small size and functionality, particularly with direct backlighting systems that suffer from thickness and uniformity issues, and side backlighting systems that require reliable and uniform light guide films.
Innovation Solution
The use of a flexible light guide film with elastic and hardened plunging structures, combined with a reflective layer and side-emitting LEDs, allows for efficient light distribution and actuation of electrical switches, providing uniform illumination and reduced thickness through the integration of micro-optic structures and optical patterns.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If direct backlighting is used to illuminate the keypad, then illumination intensity is improved, but keypad thickness increases
Solution Approach 1:
The patent transitions from direct backlighting (light source positioned directly behind the keypad) to side backlighting (light source positioned at the side edge of the keypad). This dimensional change in light source placement allows illumination to be achieved without increasing keypad thickness, as the light enters from the side and is distributed through the light guide film laterally across the keypad surface.
Solution Approach 2:
The patent introduces a light guide film as an intermediary component between the side-positioned LED light source and the keypad keys. This light guide film receives light from the side LED and distributes it uniformly across the keypad surface, enabling effective illumination without requiring the light source to be positioned directly behind the keys, thus avoiding thickness increase.
2Length of stationary object
If side backlighting is used to reduce thickness, then keypad thickness is reduced, but illumination uniformity deteriorates
Solution Approach 1:
The patent applies local quality by positioning multiple LED light sources at different locations along the side edge of the keypad, and by incorporating reflective elements at specific positions within the light guide film structure. This localized optimization of light source placement and reflective positioning ensures uniform light distribution across different regions of the keypad, compensating for the inherent non-uniformity that would result from simple side backlighting.
Solution Approach 2:
The light guide film serves as a mediator that receives light from side-positioned LEDs and distributes it uniformly across the keypad surface. The film's optical properties and structural design (including potential internal reflective elements) enable it to transform the non-uniform side light input into uniform illumination across the entire keypad, maintaining thin profile while achieving illumination uniformity.
3Reliability
If plunging structures are made harder to ensure reliable switch actuation, then reliability is improved, but tactile feedback deteriorates
Solution Approach 1:
The patent applies local quality by creating regions of different hardness within the plunging structures. The portions of the plunging structures that contact the switches are made harder to ensure reliable actuation, while other portions remain softer to provide adequate tactile feedback to the user. This spatial variation in material properties allows both reliability and tactile feedback requirements to be satisfied simultaneously.
Solution Approach 2:
The patent employs composite material construction for the plunging structures, combining materials with different hardness properties in a single integrated component. This allows the plunging structure to exhibit both hard characteristics (for reliable switch contact) and soft characteristics (for tactile feedback) in different regions, resolving the contradiction between reliability and ease of operation.
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 solution enhances illumination uniformity and reduces keypad thickness, ensuring reliable key actuation and tactile feedback while maintaining a compact design, addressing the limitations of direct and side backlighting systems.
Implementation Method 1
a flexible light guide film with elastic and hardened plunging structures, combined with a reflective layer and side-emitting LEDs, allows for efficient light distribution
Implementation Method 2
side-emitting LEDs, allows for efficient light distribution and actuation of electrical switches, providing uniform illumination
Implementation Method 3
combined with a reflective layer and side-emitting LEDs, allows for efficient light distribution
Implementation Method 4
flexible light guide film with elastic and hardened plunging structures, combined with a reflective layer and side-emitting LEDs, allows for efficient light distribution and actuation of electrical switches
Data Source
AI summary
A keypad illumination apparatus having a key plate member, a flexible light guide film, a reflective layer, a plurality of metal domes, a light source and a substrate. The key plate member may have a plurality of keys formed thereon. The flexible light guide film is configured to transmit light from the light source and has a plurality of plunging structures and apertures to accommodate the plurality of metal domes, which may be configured to actuate a plurality of electrical switches on the substrate.