Viewing Angle Switchable Back Light Unit for LCD Privacy
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Solution Overview
Problem
Current liquid crystal display (LCD) back light units cannot be selectively controlled to operate in both privacy mode with a narrow viewing angle and general mode with a wide viewing angle, requiring additional optical films that can interfere with touch panel functionality.
Innovation Solution
An ultra-thin film type back light unit featuring a light guide film with a light collimator that includes a horizontal taper part and a vertical wedge part, allowing for the conversion of expanding light from LED sources into collimated light, which can be controlled to achieve either narrow or wide viewing angles without additional optical films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If additional optical films are added to achieve privacy mode, then viewing angle control is improved, but device complexity and interference with touch panel functionality increase
Solution Approach 1:
The patent merges the privacy mode function directly into the backlight unit structure by integrating a light guide film with specific refractive index characteristics and optical sheet configurations, eliminating the need for separate additional optical films. This combines multiple functions (backlighting and viewing angle control) into a single integrated system.
Solution Approach 2:
The backlight unit is designed to perform multiple functions: it provides general illumination for wide viewing angles while simultaneously enabling privacy mode with narrow viewing angles through selective activation of different light sources (edge-type LEDs vs. surface-type LEDs) and corresponding optical path configurations within the same device.
2Adaptability or versatility
If additional optical films are added to achieve privacy mode, then viewing angle control is improved, but touch panel functionality is interfered with
Solution Approach 1:
The privacy mode functionality is merged into the backlight unit rather than being added as a separate optical film layer on the display surface. This integration ensures that touch operations can proceed through the display surface without interference from additional privacy films, while still achieving the desired viewing angle control through the backlight's optical design.
3Ease of operation
If traditional backlight units are used, then wide viewing angle is achieved, but privacy mode capability is lost
Solution Approach 1:
The backlight unit incorporates dynamic switching capability between different operating modes through independent control of edge-type and surface-type LED arrays. This allows the system to transition between wide viewing angle mode (general mode) and narrow viewing angle mode (privacy mode) based on user needs, making the viewing angle characteristic adjustable rather than fixed.
4Length of moving object
If edge type backlight unit is used, then thickness is reduced, but light distribution uniformity may be compromised
Solution Approach 1:
The patent combines edge-type backlighting (for thinness) with surface-type LED arrays (for uniform light distribution) within the same backlight unit. The edge-type LEDs provide the primary light source for thickness reduction, while the surface-type LEDs compensate for non-uniformities in light distribution, achieving both thinness and uniformity simultaneously.
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
Enables selective operation in privacy and general modes without obstructing touch panel functionality, providing even luminescence distribution and thinness comparable to organic light emitting diode displays, suitable for various applications including thin LCDs with touch input devices.
Implementation Method 1
a light guide film with a light collimator that includes a horizontal taper part and a vertical wedge part, allowing for the conversion of expanding light from LED sources into collimated light
Implementation Method 2
a light guide film with a light collimator... providing evenly luminescence distribution
Data Source
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AI summary
The present disclosure relates to a viewing angle switchable back light unit in which the general mode and the privacy mode in a liquid crystal display can be selected. The present disclosure suggests a thin film type back light unit comprising: a light guide film (LGF), a light radiator (VHOE), a first light source (LS1) and a light collimator (WLC). The light guide film (LGF) includes a light entering part (LIN) defined at one side, a light guiding part (LWG) extending from the one side to an opposite side of the one side, and a light radiating part (LOT) defined on one plane surface. The light radiator (VHOE) is disposed on the light radiating part (LOT). The first light source (LS1) is disposed as facing the light entering part (LIN). The light collimator (WLC) is disposed on the light entering part (LIN) as facing the first light source (LS1). The light collimator (WLC) receives an expanding light from the first light source (LS1), converts the expanding light into a collimated light, and provides the collimated light to the light entering part (LIN).