Fingerprint Sensor Light Blocking in Display Devices
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Solution Overview
Problem
Current display devices with integrated fingerprint sensors face challenges in enhancing sensing ability while maintaining display quality and preventing light leakage.
Innovation Solution
A display device design featuring a substrate with distinct areas for display and fingerprint sensing, incorporating a cushion layer, protecting layer, adhesive layers, and light-blocking layers to optimize light transmittance and sensitivity for improved fingerprint sensing, along with a flexible printed circuit board to manage light and fix the fingerprint sensor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fingerprint sensor is integrated into the display device, then security functionality is improved, but light leakage occurs and sensing ability deteriorates
Solution Approach 1:
The display region is divided into a first area (for fingerprint sensing) and a second area (for display). The cushion layer is segmented with a first opening portion corresponding to the first area and a second opening portion corresponding to the second area. This segmentation allows light to reach the fingerprint sensor in the first area while preventing light leakage in the second area, thereby improving both security functionality and sensing ability simultaneously.
Solution Approach 2:
A light-blocking layer is introduced as an intermediary component between the cushion layer and the fingerprint sensor. This light-blocking layer selectively blocks light in the second area (preventing light leakage) while allowing light to pass through to the fingerprint sensor in the first area, resolving the contradiction between security functionality and sensing ability.
2Object-generated harmful factors
If a light-blocking layer is added to prevent light leakage, then light leakage is reduced, but device complexity increases
Solution Approach 1:
The light-blocking layer is merged with the cushion layer structure, where the cushion layer includes both a first opening portion (for fingerprint sensing) and a second opening portion (for light blocking). This integration reduces the need for separate components and simplifies the overall device structure while still preventing light leakage effectively.
Solution Approach 2:
The cushion layer is designed to serve multiple functions: it provides mechanical cushioning support and simultaneously acts as a light-blocking structure through its second opening portion. This multi-functionality reduces the need for additional dedicated light-blocking components, thereby reducing device complexity while preventing light leakage.
3Illumination intensity
If the fingerprint sensor is placed on the rear surface of the substrate, then display quality is improved, but light transmittance to the sensor is reduced
Solution Approach 1:
The cushion layer is designed with different properties in different regions: the first opening portion allows maximum light transmittance to the fingerprint sensor, while the second opening portion provides light blocking. This local differentiation of properties allows the fingerprint sensor on the rear surface to receive sufficient light while maintaining display quality in the second area.
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 design enhances the sensing sensitivity of the fingerprint sensor by increasing light transmittance in the sensing area and preventing light leakage, thereby improving the ability to detect fingerprints effectively.
Implementation Method 1
a first light-blocking layer disposed on a rear surface of the substrate, the first light-blocking layer covering at least part of the cushion layer and a lower surface of the fingerprint sensor
Implementation Method 2
The fingerprint sensor may be configured to sense the light emitted from the display unit and reflected by the fingerprint of the user
Data Source
AI summary
A display device including a substrate including a display region and a non-display region disposed at one side of the display region, the display region includes first and second areas adjacent to each other; a display unit disposed on a front surface of the substrate, the display unit including a plurality of pixels for displaying an image; a cushion layer disposed on a rear surface of the substrate, the cushion layer including a first opening portion corresponding to the first area; a fingerprint sensor provided in the first opening portion of the cushion layer, the fingerprint sensor sensing a fingerprint of a user; and a first light-blocking layer disposed on a rear surface of the substrate, the first light-blocking layer covering at least part of the cushion layer and a lower surface of the fingerprint sensor.