Liquid Crystal Display Conductive Resin Flow Control
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Solution Overview
Problem
In liquid crystal display devices with a lateral electric field system, the use of conductive resin with low viscosity leads to excessive flow, causing potential short circuits when mounted components like drivers or flexible wiring boards are close to the GND pad, especially with reduced distances due to thinner substrates and increased resolution.
Innovation Solution
A dam part is integrated into the insulating layer on the substrate to regulate the flow of conductive resin, limiting its range and preventing short circuits by positioning it strategically next to the conductive resin and pad, ensuring the height difference between the pad and conductive film is 0.31 mm or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conductive resin having low viscosity is used to suppress the rising of the conductive resin, then the conductive resin flows over a wide range, but this causes a problem that a wide region is required and increases the risk of short circuit with mounted components
Solution Approach 1:
The insulating layer is divided into a first insulating layer and a second insulating layer with different dielectric constants. The first insulating layer (with higher dielectric constant) is positioned below the pad, while the second insulating layer (with lower dielectric constant) is positioned above the pad. This segmentation creates an optimized electric field distribution that suppresses conductive resin flow without requiring excessive resin placement area.
Solution Approach 2:
Different regions of the insulating structure are assigned different dielectric properties. The first insulating layer has a dielectric constant of 3.5 or higher (preferably 4.5 or higher), while the second insulating layer has a dielectric constant of 3.5 or lower (preferably 2.5 or lower). This local quality differentiation allows precise control of electric field concentration, suppressing resin flow toward the pad while maintaining overall device performance.
2Productivity
If the distance between the GND pad and the mounted component is reduced due to the narrowing of a picture frame or an increase in resolution, then the device density increases, but the risk of short circuit increases when conductive resin flows
Solution Approach 1:
The insulating layers are pre-configured with specific dielectric constants before conductive resin application. The first insulating layer (higher dielectric constant) below the pad and the second insulating layer (lower dielectric constant) above the pad create a pre-established electric field barrier that prevents conductive resin from flowing toward nearby mounted components, even when spacing is reduced to 1 mm or less.
Solution Approach 2:
The dielectric constant parameters of the insulating layers are specifically optimized to control electric field distribution. By setting the first insulating layer's dielectric constant to 3.5 or higher and the second insulating layer's dielectric constant to 3.5 or lower, the electric field is concentrated in a controlled manner that suppresses conductive resin flow, enabling safe reduction of distances to mounted components.
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 dam part effectively limits the flow range of the conductive resin, allowing for closer mounting of components without risking short circuits, thereby ensuring reliable operation even with reduced viscosity and tighter spacing.
Implementation Method 1
it has been found that when an insulating layer having a specific dielectric constant distribution is formed on a substrate, an electric field is concentrated between a pad and a conductive film, so that flow of a conductive resin can be suppressed
Data Source
AI summary
A liquid crystal display device includes: a first substrate having a first portion and a second portion; a pad formed in the first portion; a second substrate facing the second portion; a conductive film formed on the opposite face of the second substrate from the face facing the first substrate; liquid crystal arranged between the first substrate and the second substrate; a conductive resin disposed on the pad so as to extend on the conductive film and electrically connecting the pad with the conductive film; and an insulating layer formed on the first substrate and including a dam part arranged next to the conductive resin in the first portion. The height from the surface of the pad to the surface of the conductive film is 0.31 mm or less in a position avoiding the insulating layer.