The Technological Breakthrough of Transparent Glass Keyboards: Bastron’s Dual-Layer Separated Architecture

In the technological exploration of transparent glass keyboards, Bastron has taken a technical path completely different from the mainstream OGS (One Glass Solution). The boldness of this approach lies in the fact that it does not attempt to make minor adjustments within the OGS framework, but rather fundamentally reconstructs the structural logic of the touch sensor.

I. The Dilemma of the OGS Approach: Visible Limitations

As mentioned earlier, although the "out-of-VAA bridging" technology solves the optical visibility problem of SITO bridging, the OGS solution exposes insurmountable defects in the specific product form of the transparent keyboard:

1. High Process Complexity, Low Yield

OGS fabricates the touch sensor directly on the cover glass, meaning all process steps—from ITO coating, photolithography etching, to insulating layer coating—must be completed on a single piece of glass. If a defect occurs at any stage, the entire glass sheet is scrapped. For large-size products like transparent keyboards, yield control is particularly difficult.

2. The Black Border is Unavoidable

To conceal the bridging circuits and border traces outside the VAA, the OGS solution must retain a black border (BM) around the keyboard. For ordinary touchscreens, a black border is standard and users are accustomed to it. However, for a product like the transparent keyboard that pursues a "fully transparent" visual effect, any opaque border deviates from the very concept of "transparency."

3. The Contradiction Between Protection and Function

OGS places the sensor circuits directly on the inner side of the cover glass, meaning the circuit layer is "exposed." Although a protective glass can be attached beneath the circuit layer, this increases thickness, reduces light transmittance, and each additional lamination step introduces further yield loss.

II. Bastron’s Breakthrough: Dual-Layer Separated Architecture

Facing the above dilemmas of OGS, Bastron chose a distinctly different technical path: fabricating TX (drive electrodes) and RX (sense electrodes) on two separate glass substrates, and laminating them with optical adhesive to achieve the bridging function.

The core idea of this design can be summarized as: replacing "process bridging" with "spatial separation."

2.1 Structural Analysis

The layered stack structure of this solution, from top to bottom, is:

This structure is corroborated by patent literature. A 2021 patent application by Truly Opto-Electronics, titled "A touch structure and touch screen" (CN216286615U), describes a similar solution: the touch functional layer is made between two glass sheets and isolated by an optical adhesive layer, which not only provides insulation but also offers protection, saving one insulating process step.

2.2 Differences from Traditional DITO

It should be noted that this "TX and RX on separate glass sheets" solution is fundamentally different from traditional DITO:

· Traditional DITO: TX and RX are on opposite sides of the same glass substrate, requiring two coatings and two photolithography steps, making the process complex.

· Bastron’s solution: TX and RX are on two independent glass substrates, each requiring only single-sided coating, making the process for each sheet simpler.

The difference is: DITO makes "two layers on one piece of glass," while Bastron’s solution makes "one layer on each of two pieces of glass, then laminates them." The latter breaks down a complex dual-layer process into two relatively simple single-layer processes, greatly reducing the difficulty and risk of each substrate’s manufacturing.

III. Core Advantages of the Dual-Layer Separated Architecture

3.1 Complete Elimination of Bridging Issues

In the traditional SITO solution, bridging allows intersecting traces on the same layer to "cross over" each other. However, in Bastron’s dual-layer separated solution, TX and RX are not on the same plane at all—they are physically isolated by the glass substrates and optical adhesive, so there is naturally no intersection, and therefore no need for bridging.

This means:

· No need to fabricate any bridging structures within the VAA.

· No need to worry about the optical visibility of bridge points.

· No need to address step-coverage breakage issues at bridging areas.

3.2 Achieving a Truly Borderless Design

Because there is no need to arrange bridges and traces in the border area, Bastron’s solution enables a black-border-free, fully transparent design.

This is already reflected in Bastron’s "Transparent Touch Keyboard" patent (CN203966061U), which describes a keyboard body with multiple spaced-apart key regions and at least one transparent conductive film for touch sensing in each key region, where the keyboard body includes a transparent substrate and a transparent cover plate attached to the substrate.

Further exploration into transparency is also evident in nanowire technology. Related patents show that by encapsulating nanowires within a transparent substrate, a fully transparent touch substrate can be formed, featuring "no border, no coils, and no visible conductive traces."

3.3 Significant Improvement in Process Yield

Breaking down a complex dual-layer process into two independent single-layer processes brings notable process advantages:

More importantly, the two glass sheets can be processed independently on separate production lines and finally laminated with optical adhesive. If one sheet has a problem, only that sheet needs to be scrapped, and the other can be retained, reducing the cost loss per scrap event.

3.4 Dual Role of Optical Adhesive: Insulation and Protection

In Bastron’s solution, the optical clear adhesive (OCA) layer plays a critical role:

· Insulation: Isolates the TX and RX layers to prevent short circuits.

· Protection: Encapsulates the sensor circuits between the two glass sheets, fully protecting the circuit layer without needing an additional protective glass.

This design not only saves an insulating process step but also improves product reliability. Truly Opto-Electronics’ patent explicitly states that the optical adhesive layer "not only provides insulation but also offers protection."

IV. Technical Positioning: Not Universal, but Well-Suited for Its Purpose

It should be noted objectively that the dual-layer separated architecture is not superior to OGS in all scenarios. It involves trade-offs in the following areas:

1. Slightly Increased Thickness
The total thickness of two glass sheets plus one OCA layer is typically greater than that of a single OGS sheet. For ultra-thin devices like smartphones and tablets, this may be a disadvantage. However, for a desktop keyboard product, the millimeter-scale thickness difference is almost negligible.