Optical Sheet Notch Design for Drop Impact Resistance

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Solution Overview

Problem

Conventional liquid crystal display apparatuses in mobile devices are prone to display failure due to deformation caused by mechanical stresses like drop impact, as the optical sheets are not adequately secured to prevent warpage and positional deviation.

Innovation Solution

The introduction of notches or protrusions at the boundary areas between the optical sheet and the resin frame or light guide plate helps absorb and disperse mechanical stress, preventing deformation from extending to the display area, thereby securing the optical sheet effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the optical sheet is attached to the resin frame using conventional fixing methods (one side fixed, other side fitted to concavity), then the optical sheet can be positioned and secured, but the optical sheet is prone to deformation and warpage under mechanical stress such as drop impact

Engineering Contradiction:

Improveresistance to deformation under mechanical stressVSAvoidstructure of optical sheet fixing

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The optical sheet is divided into multiple regions: a display area and multiple fixing portions. Notches are created at the boundaries between these regions, segmenting the stress transmission path and preventing deformation from spreading to the display area.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Notches are pre-created at the boundary areas between the display area and fixing portions to absorb and disperse mechanical stress before it can propagate to the display area, providing beforehand protection against deformation under impact.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Manufacturing precision

If notches are created at the boundary areas of the optical sheet, then deformation is prevented from extending to the display area, but the manufacturing process becomes more complex

Engineering Contradiction:

Improvepositioning accuracy of optical sheetVSAvoidprocess of creating notches

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

Notches are created during the manufacturing process at predetermined boundary locations before the optical sheet is assembled into the display apparatus. This preliminary action ensures precise positioning and stress management while the optical sheet is still being fabricated.

Inventive Principle:

Principle #10Preliminary action

3Stability of the object's composition

If the optical sheet is firmly secured to prevent any movement, then positional deviation is reduced, but the optical sheet cannot absorb thermal expansion differences

Engineering Contradiction:

Improvepositional stability of optical sheetVSAvoidability to accommodate thermal expansion

Core Design Contradiction:

Stability of the object's compositionVSAdaptability or versatility

Solution Approach 1:

Different regions of the optical sheet have different properties: the display area maintains high stability for image quality, while the fixing portions with notches provide flexibility to accommodate thermal expansion and contraction without affecting the display area.

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS7626747B2Liquid crystal display apparatus

Publication Date: 2009.12.01 PANASONIC HOLDINGS CORP

AI summary

A liquid crystal display apparatus includes an optical sheet for uniformly diffusing light toward a light-emitting face, and a resin frame onto which the optical sheet is attached. The optical sheet has the first fixing portion or the second fixing portion. The optical sheet is attached to the resin frame by fitting the first fixing portion or the second fixing portion to a concavity created at the resin frame at a part corresponding to the first fixing portion or the second fixing portion. At least one notch is created at a boundary area between a display area of the optical sheet and the first fixing portion or the second portion so that deformation in the optical sheet caused by a significant mechanical stress, such as drop impact, does not extend to the display area.