Reflection Sheet Bonding for LED Backlight Units
Solution Overview
Problem
Display devices with liquid crystal panels require backlight units to enhance brightness, but existing reflection sheets face challenges in achieving high reflectivity due to electrical conduction issues and air bubble formation during bonding, leading to reduced brightness.
Innovation Solution
A lighting device with a light source substrate and a reflection sheet featuring an insulating sheet and a metal thin film reflection layer, where the reflection sheet is bonded to the substrate with an adhesive layer, and holes are drilled through both layers to expose light sources, ensuring accurate bonding and higher reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a metal reflection film is used to improve reflectivity, then reflectivity increases, but electrical conduction occurs between solders causing bonding issues
Solution Approach 1:
The reflection sheet is divided into multiple isolated metal reflection islands, each positioned under a solder joint. This segmentation prevents electrical conduction between adjacent solders while maintaining high reflectivity in each localized area. The insulating sheet between the metal layers further ensures electrical isolation.
Solution Approach 2:
An insulating sheet is introduced as an intermediary layer between the metal reflection film and the LED substrate. This insulating layer prevents direct electrical contact between the metal reflection film and solder joints while allowing the metal film to maintain its reflective function. The insulating sheet acts as a mediator that decouples the electrical and optical functions.
2Manufacturing precision
If accurate bonding of reflection sheet is required to prevent electrical conduction, then bonding precision must be high, but air bubbles become difficult to eliminate
Solution Approach 1:
The bonding interface is segmented into multiple small contact areas between the reflection sheet and substrate, rather than requiring large-area continuous contact. This segmentation reduces the total volume of air bubbles that can form and makes it easier to eliminate trapped air during the bonding process while maintaining precise electrical isolation.
3Ease of manufacture
If hole tolerance is increased to facilitate reflection sheet bonding, then bonding becomes easier, but LED substrate or conductive pattern exposure reduces reflectivity
Solution Approach 1:
The holes in the reflection sheet are segmented into multiple small openings rather than large continuous areas. This allows the holes to be positioned with larger tolerance without significantly exposing the underlying conductive patterns, as the total exposed area remains small. The segmented structure maintains reflectivity while facilitating easier manufacturing.
4Ease of manufacture
If white resist is formed through silk printing, then manufacturing is simple, but film thickness is insufficient for high reflectivity
Solution Approach 1:
The reflection sheet uses a composite structure combining an insulating sheet with a metal reflection film layer. This composite material approach achieves high reflectivity (comparable to or exceeding 90%) without relying on thick white resist coatings. The metal film provides superior reflective properties while the insulating sheet maintains electrical isolation, replacing the insufficient white resist with a more effective composite structure.
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 increases the brightness of lighting and display devices by improving reflectivity and reducing electrical conduction, while allowing for precise bonding without air bubbles, thus enhancing light use efficiency.
Implementation Method 1
The reflection layer includes a metal thin film stacked on the insulating sheet
Implementation Method 2
The light source substrate and the reflection sheet are bonded together with an adhesive layer
Data Source
AI summary
A lighting device includes light sources, a light source substrate, and a reflection sheet. The light source substrate includes a plate-shaped base including a mounting surface on which mounting portions are formed. The light sources are mounted on the mounting portions with solders. The reflection sheet includes an insulating sheet, a reflection layer, and holes. The reflection layer includes a metal thin film stacked on the insulating sheet. The holes are drilled through the reflection layer and the insulating sheet at positions corresponding to the light sources so that the light sources are exposed through the holes. The light source substrate and the reflection sheet are bonded together with an adhesive layer. The insulating sheet is made of a material having a heat resistance higher than a melting temperature of the solders and an elastic modulus lower than that of the base of the light source substrate.