Back-Side Exposure for Color Filter Alignment

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Solution Overview

Problem

The fabrication of color filter layers in TFT-LCDs is hindered by alignment errors in the black matrix and assembly errors, which affect the brightness and contrast of the display, and existing methods are limited by equipment capabilities and require multiple photomasks, increasing costs.

Innovation Solution

A method involving a back-side exposure process using an opaque metal pattern as a mask to form the black matrix and color filter patterns on the active device array substrate, reducing alignment errors and eliminating the need for one photomask, thereby improving assembly accuracy and aperture ratio.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If conventional front-side exposure process is used to form black matrix, then equipment capability is utilized, but alignment error occurs between black matrix and color filter layer

Engineering Contradiction:

Improvealignment accuracy of black matrixVSAvoidassembly accuracy of color filter layer

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent applies back-side exposure process instead of conventional front-side exposure to form the black matrix. By exposing the photoresist layer from the back side of the substrate using the opaque metal pattern as a mask, the black matrix is formed with automatic alignment to the metal pattern, eliminating alignment errors that occur with front-side exposure methods.

Inventive Principle:

Principle #13The other way round (Inversion)

2Manufacturing precision

If multiple photomasks are used in fabrication process, then complete pattern formation is achieved, but fabrication cost increases

Engineering Contradiction:

Improvepattern formation completenessVSAvoidfabrication cost

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The patent combines the black matrix formation process with the color filter layer formation process into a single integrated process. The back-side exposure using the opaque metal pattern as mask forms both the black matrix and defines the pixel regions for color filters simultaneously, eliminating the need for separate photomasks and reducing fabrication costs.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If alignment error is reduced, then assembly accuracy improves, but process complexity increases

Engineering Contradiction:

Improveassembly accuracy of color filter layerVSAvoidfabrication process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The opaque metal pattern on the substrate serves as its own mask for the back-side exposure process. The metal pattern automatically defines the exposure regions, eliminating the need for external photomasks and alignment mechanisms. This self-aligning process reduces assembly errors while maintaining process simplicity.

Inventive Principle:

Principle #25Self-service

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

This method effectively reduces alignment and assembly errors, lowers fabrication costs, and enhances the aperture ratio of the TFT-LCD panel, improving display brightness and contrast.

Implementation Method 1

A back-side exposure process is performed on the active device array substrate using the opaque metal layer as a mask to form a black matrix thereon

Methodology Applied

Scientific EffectPhotomasking: Absorption (EM radiation)

Implementation Method 2

A back-side exposure process is performed to expose the black positive photoresist layer by using the opaque metal pattern as a mask

Methodology Applied

Scientific EffectPhotoresist exposure: Photopolymerisation

Data Source

PatentUS8178262B2Method for fabricating color filter layer

Publication Date: 2012.05.15 AU OPTRONICS CORP

AI summary

A method of fabricating a color filter layer is provided. An active device array substrate having an opaque metal pattern formed thereon is provided. A planarization layer covering the opaque metal pattern is formed. A back-side exposure process is performed on the active device array substrate using the opaque metal layer as a mask to form a black matrix thereon, wherein the black matrix defines a plurality of pixel regions. A plurality of color filter patterns is formed in the pixel regions.