Color Filter Array Inkjet Printing Film Thickness Control

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Solution Overview

Problem

The inkjet printing process for forming color filter arrays results in uneven film thickness of color filter patterns due to greater cohesion of the ink compared to adhesion with the substrate, leading to suboptimal color display performance.

Innovation Solution

A color filter array with a light shielding layer having specific height and openings, where the inkjet printing process is used to form color filter patterns with controlled maximum and minimum film thickness, ensuring a difference of less than 0.39 um, achieved by optimizing the light shielding layer height between 1.6 um and 2.22 um, and the inkjet printing process parameters.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If inkjet printing process is used to form color filter patterns, then manufacturing cost and time are reduced, but film thickness uniformity deteriorates due to greater ink cohesion than adhesion

Engineering Contradiction:

Improvemanufacturing efficiencyVSAvoidfilm thickness uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent introduces a adhesion promotion layer between the substrate and the color filter ink. This intermediary layer has specific surface properties that enhance adhesion to the ink while maintaining compatibility with the substrate, thereby improving film thickness uniformity without sacrificing the efficiency benefits of the inkjet printing process

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent modifies physical and chemical parameters of the inkjet printing process including ink formulation (adding adhesion promoters), printing parameters (droplet size, spacing, and deposition rate), and substrate surface treatment. These parameter changes optimize the balance between ink cohesion and adhesion, achieving uniform film thickness while maintaining manufacturing efficiency

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If conventional spinning coating and photolithography process is used, then color filter patterns can be formed, but material waste increases and manufacturing cost increases

Engineering Contradiction:

Improvepattern formation qualityVSAvoidphoto resist material waste

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The patent replaces the conventional spinning coating and photolithography mechanical processes with inkjet printing technology. This substitution uses digital inkjet deposition to directly form color filter patterns without requiring photo resist materials, exposing, or developing steps, thereby eliminating material waste while maintaining pattern formation quality

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The inkjet printing process enables localized deposition of ink precisely where needed on the substrate. This local quality approach allows for direct writing of color filter patterns with exact material placement, eliminating the widespread material application and subsequent removal required in spinning coating and photolithography processes

Inventive Principle:

Principle #3Local quality

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 approach ensures even and uniform film thickness of color filter patterns, enhancing the color display performance by maintaining a maximum film thickness within the specified range relative to the light shielding layer height, thereby improving the overall display quality.

Implementation Method 1

An inkjet printing (IJP) process is performed to inject color filter ink into the openings of the light shielding layer

Methodology Applied

Scientific EffectInkjet printing:

Implementation Method 2

A solidifying process is performed to solidify the color filter ink to form a plurality of color filter patterns

Methodology Applied

Scientific EffectSolidification: Phase Change

Data Source

PatentUS8736991B2Color filter array and manufacturing method thereof

Publication Date: 2014.05.27 AU OPTRONICS CORP

AI summary

A color filter array includes a substrate, a light shielding layer, and color filter patterns. The light shielding layer is on the substrate and has openings exposing a surface of the substrate. Besides, the light shielding layer has a height H. The color filter patterns are located in the openings of the light shielding layer. Each color filter pattern has the maximum film thickness Lc and the minimum film thickness Ls, and the difference between the maximum film thickness Lc and the minimum film thickness Ls is ΔL. The maximum film thickness Lc of each color filter pattern satisfies (m×H)<Lc<(n×H), wherein m comprises about 0.83, n comprises about 0.91, the height H of the light shielding layer satisfies a<H<b, wherein a comprises about 1.6 um and b comprises 2.22 um, and the difference ΔL is less than about 0.39 um.