Capacitive Touch Glass Assembly for Thick, Pressure-Resistant Covers
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Solution Overview
Problem
Existing glasses with capacitive keys for portable electronic instruments face challenges in achieving both sufficient thickness for durability and high sensitivity, as well as complex manufacturing processes that limit the range of usable substances and increase thickness, impairing keyboard operation and requiring precise placement of insulating films.
Innovation Solution
A glass with capacitive keys is designed where an insulating film with electrodes is fixed on the outer surface of a rigid base substrate, connected via metallized holes and conductive rods, allowing for sensitive finger activation without compromising durability, and a method involving hot rolling and adhesive films for secure mounting and electrical connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the glass is made thick to withstand high external pressures, then the durability and pressure resistance are improved, but the sensitivity of capacitive keys deteriorates due to excessive thickness interfering with proper functioning
Solution Approach 1:
The glass assembly is divided into two separate components: a thick base glass substrate for pressure resistance and a thin insulating film for capacitive key functionality. This segmentation allows each component to be optimized independently - the base glass can be thick enough to withstand high external pressures while the insulating film remains thin to ensure proper capacitive key sensitivity and response.
2Strength
If an additional layer of glass is added to cover the liquid crystal display, then the display protection is improved, but the distance between user's finger and capacitive button electrode increases, reducing activation sensitivity
Solution Approach 1:
The capacitive key electrodes are moved from the display layer to the inner surface of the base glass substrate, changing the spatial dimension of electrode placement. This allows the display glass to remain thick for protection while the electrodes are positioned as close as possible to the outer surface through the thin insulating film, maintaining high touch activation sensitivity.
3Ease of manufacture
If transparent electrodes are deposited and chemically etched on the inner surface of the glass, then the capacitive touch buttons are formed, but the manufacturing process becomes complex and limited to specific substances
Solution Approach 1:
The manufacturing approach changes from depositing and etching transparent conductive oxide layers directly on glass to using a flexible insulating film with pre-formed conductive elements. This parameter change in the manufacturing process allows for simpler fabrication using conventional flexible substrate techniques, expanding material choices beyond traditional glass-compatible substances.
4Adaptability or versatility
If an insulating film with capacitive touchpads is placed in a mold with liquid substance to solidify, then the capacitive touchpads are integrated into the glass, but precise positioning is required and only few substances can be used
Solution Approach 1:
The capacitive key electrodes and conductive tracks are pre-formed on the insulating film before the lamination process. This preliminary action allows the entire assembly to be transferred as a complete unit to the base glass, eliminating the need for precise positioning during assembly and expanding material selection to include all flexible substrate-compatible 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
The solution enables a glass with capacitive keys that is resistant to external forces while maintaining high sensitivity, allowing for reliable operation of capacitive keys on portable electronic instruments, such as watches, without the drawbacks of increased thickness or complex manufacturing.
Implementation Method 1
an adhesive film, and by hot laminating the layers of the two films
Implementation Method 2
by hot laminating the layers of the two films
Data Source
Figure 1a~1b
Figure 2
Figure 3
AI summary
The glass (1) with capacitive keys for a portable electronic instrument, comprises a base substrate (2) and at least one insulating film (11), which is provided with electrodes (13) of the capacitive keys. The insulating film is fixed on an outer surface of the base substrate (2), and a connection device (4, 5) is made in the base substrate. The connection device, which comprises conductive rods (4) in holes (5), makes it possible to electrically connect the electrodes of the insulating film to a processing circuit in the portable electronic instrument fitted with the glass (1). A decoration film (16) can also be attached via an adhesive film (14) to the insulating film.