DMD Mirror Multilayer Stack for Surface Uniformity and Luminance

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Solution Overview

Problem

The surface unevenness of metal films in digital micro mirror devices (DMDs) leads to scattered light and reduced luminance, while exposure to the atmosphere causes oxidation and warpage, further lowering reflectance and luminance.

Innovation Solution

A configuration where a reflective metal film is deposited on a high melting point metal film, such as titanium or titanium nitride, with an antioxidative film in between, to minimize surface unevenness and prevent oxidation, enhancing reflectance and luminance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a metal film (e.g., aluminum) is used as a reflective film, then high reflectivity is achieved, but the surface becomes uneven and scattered light occurs, lowering luminance

Engineering Contradiction:

ImproveluminanceVSAvoidsurface uniformity

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

A high melting point metal film (titanium or titanium nitride) is introduced as an intermediary layer between the substrate and the aluminum reflective film. This intermediary layer provides a stable base that prevents aluminum migration and maintains surface uniformity, while the aluminum layer retains its high reflectivity function.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention uses a composite structure combining titanium/titanium nitride with aluminum. The titanium layer provides structural stability and oxidation resistance, while the aluminum layer provides high reflectivity, creating a composite material system that achieves both surface uniformity and high luminance.

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If titanium is used as a base metal film to suppress aluminum migration, then surface uniformity is improved, but oxidation occurs when exposed to atmosphere, causing warpage and lowering reflectance

Engineering Contradiction:

Improvesurface uniformityVSAvoidoxidation resistance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

An antioxidative film is introduced as an intermediary protective layer between the titanium base film and the atmosphere. This protective layer prevents oxygen from reaching the titanium, thereby preventing oxidation and warpage while allowing the titanium to maintain its function of suppressing aluminum migration.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The invention converts the harmful effect of titanium oxidation into a beneficial protective mechanism. By intentionally adding an antioxidative film, the titanium's reactivity is harnessed to create a stable structure that, when protected, provides excellent surface uniformity and aluminum migration suppression.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Ease of manufacture

If the mirror is exposed to the atmosphere, then manufacturing is simplified, but oxidation film forms on the metal film, causing warpage and lowering reflectance

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidreflectance

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The antioxidative film is formed in advance during the manufacturing process, before the device is exposed to the atmosphere. This preliminary protective action ensures that oxidation cannot occur during subsequent handling or operation, maintaining high reflectance without complicating the manufacturing process.

Inventive Principle:

Principle #10Preliminary action

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 configuration flattens the reflective metal film surface, improves reflectance, and prevents warpage by suppressing oxidation, thereby enhancing luminance and display quality in electrooptical devices like projectors.

Implementation Method 1

since the reflective metal film is arranged on the high melting point metal film, for example, a space difference between spaces of a lattice plane of a portion where the two films overlap each other, can be small, and it is possible to flatten a surface of the reflective metal film which is the uppermost film

Methodology Applied

Scientific EffectSurface flattening effect:

Implementation Method 2

since the high melting point metal film is interposed between the reflective metal film and the antioxidative film, even when the mirror which is configured of the films, is exposed into the atmosphere, an oxidation film can be suppressed from being formed on the high melting point metal film

Methodology Applied

Scientific EffectOxidation prevention: Oxidation

Data Source

PatentUS9791692B2Electrooptical device, method for manufacturing electrooptical device, and electronic apparatus

Publication Date: 2017.10.17 SEIKO EPSON CORP

AI summary

An electrooptical device includes a substrate, a mirror that is made up of a plurality of films which are arranged so as to be separated from the substrate on one plane of the substrate, and a supporting portion that is arranged between the substrate and the mirror, and has a portion which is connected to a portion of the mirror so as to support the mirror, in which the mirror includes a third mirror film which is a reflective metal film that is arranged on a side of the mirror which is opposite to the substrate, a second mirror film which is a high melting point metal film that is arranged between the reflective metal film and the substrate, and a first mirror film which is an antioxidative film that is arranged between the high melting point metal film and the substrate.