Keypad Light Guide Plate Uniformity via Printed Patterns
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Solution Overview
Problem
Existing keypad devices with backlight functions suffer from light nonuniformity due to the weakening of light emitted from LED lamps with increasing distance, which affects visual quality and complicates manufacturing, especially in thin portable devices.
Innovation Solution
A keypad device featuring a modularized backlight module with a light guide plate made of PMMA, PC, or PET materials, incorporating patterns with adhesive and reflective materials (SiO2 or TiO2) and metal domes connected via a printed circuit board, which enhances light uniformity and simplifies manufacturing by reducing the need for multiple LED lamps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If multiple LED lamps are distributed among keys to provide backlight, then key visibility in dark conditions is improved, but light uniformity deteriorates due to light weakening with distance
Solution Approach 1:
The backlight system is segmented into multiple independent LED lamps positioned at different locations (corner LEDs and side LEDs) to illuminate different regions of the light guide plate, allowing optimized light distribution across the keypad surface
Solution Approach 2:
A light guide plate is introduced as an intermediary component between the LED lamps and the keypad keys. This light guide plate with specific refractive index (1.4-1.6) and surface patterns (micro-prisms, diffusers, or gratings) redistributes the light from multiple LED sources to achieve uniform illumination across the key surface
2Ease of manufacture
If adhesive material is disposed on the light guide plate surface to adhere dome sheets, then structural assembly is achieved, but manufacturing complexity increases due to layer disposition difficulties
Solution Approach 1:
The adhesive layer is merged with the light guide plate by disposing adhesive material directly on the light guide plate surface at the intended bonding locations. This integration eliminates the need for separate adhesive application steps and simplifies the overall layer stacking process
Solution Approach 2:
Adhesive material is pre-disposed on the light guide plate surface at specific locations before final assembly. This preliminary placement of adhesive ensures proper positioning and bonding of dome sheets and metal domes during subsequent assembly steps, reducing manufacturing complexity
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 provides improved light uniformity and energy efficiency while simplifying the manufacturing process, enabling the creation of thinner portable devices with enhanced keypad visibility in dark conditions.
Implementation Method 1
Light emitted from the light source 21 enters the light guide plate 22 laterally and reflects inside the light guide plate 22 repeatedly for proceeding in a direction opposite to the light source 21
Implementation Method 2
The light can scatter so as to emit out of a surface of the light guide plate 22 by a pattern 23 formed on the light guide plate 22
Implementation Method 3
each pattern includes adhesive material and reflective material
Data Source
AI summary
A keypad device includes a keypad with a plurality of keys in a defined order, and a light guide plate disposed under the keypad. The light guide plate includes a plurality of patterns formed by a method of printing on a surface thereof, and each pattern includes adhesive material and reflective material. The keypad device further includes at least one LED lamp disposed beside the light guide plate.