Backlight Optical Sheet Corner Shaping for Assembly Detection

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Solution Overview

Problem

Existing backlight devices for liquid crystal displays face difficulties in detecting the absence of optical sheets due to their similar shapes, making it challenging to ensure all sheets are present during assembly, which affects light control functionality.

Innovation Solution

The design involves optical sheets with uniquely shaped corner portions, where the tip ends are removed along line segments spanning between two sides, ensuring that the arrangement of these segments differs between sheets, allowing for easy visual detection of any missing sheets by creating an irregular pattern.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Difficulty of detecting and measuring

If corner portions of optical sheets are cut off along straight lines with different cutoff amounts, then the sheets can be discriminated from one another during assembly, but the cutoff portions become difficult to see when the cutoff amount is minimized to maintain light control function

Engineering Contradiction:

Improvedetectability of optical sheet absenceVSAvoidsurface area of optical sheet

Core Design Contradiction:

Difficulty of detecting and measuringVSArea of stationary object

Solution Approach 1:

The patent applies asymmetry by removing corner portions of optical sheets to create asymmetric shapes. Each optical sheet has a unique asymmetric shape with differently positioned removed corners, allowing easy visual discrimination and detection of sheet presence or absence during assembly while maintaining the minimum required surface area for light control functionality

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by modifying only the corner portions of the optical sheets while keeping the main body intact. This localized modification creates distinctive markers for identification without significantly reducing the overall surface area needed for light control, thus resolving the contradiction between detectability and surface area maintenance

Inventive Principle:

Principle #3Local quality

2Difficulty of detecting and measuring

If optical sheets are stacked in order of size of remaining portions, then the arrangement facilitates detection of missing sheets, but the sheets with similar thin sheet shapes still appear indistinguishable when viewed from above

Engineering Contradiction:

Improvevisual detection of sheet arrangementVSAvoiddistinguishability of sheet shapes

Core Design Contradiction:

Difficulty of detecting and measuringVSShape

Solution Approach 1:

The patent creates highly distinguishable shapes by removing different corners of each optical sheet, resulting in asymmetric shapes that are easily distinguishable from one another. When stacked in order of size, the asymmetric corner removal patterns create a visually detectable sequence, solving the problem of indistinguishability despite similar overall sheet dimensions

Inventive Principle:

Principle #4Asymmetry

3Difficulty of detecting and measuring

If the cutoff portions are made larger to improve visibility during manufacturing, then missing sheets can be easily detected, but the minimum predetermined surface area required for light control function is compromised

Engineering Contradiction:

Improvevisibility of corner portionsVSAvoidlight control function

Core Design Contradiction:

Difficulty of detecting and measuringVSReliability

Solution Approach 1:

The patent modifies only the corner portions locally while preserving the main body of each optical sheet. This localized corner removal creates visible markers for detection during manufacturing without significantly reducing the overall surface area, thus maintaining the reliability of light control function while improving visibility

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies partial action by removing only the corner portions rather than reducing the entire sheet size. This partial modification provides sufficient visibility for detection purposes while minimizing the impact on the overall surface area required for light control, effectively balancing detectability and functional reliability

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS7731376B2Lighting device for display device and display using the same

Publication Date: 2010.06.08 SHARP KK

AI summary

A backlight device includes a light guide plate opposed to fluorescent tubes, a diffusion sheet stacked on the light guide plate, and lens sheets further stacked on the diffusion sheet. A tip end of a corner portion of the diffusion sheet has a shape defined by removing a portion of the sheet along a straight line spanning between two sides constituting the corner portion. In first of the lens sheets, a tip end portion of a corner portion formed by two sides has a shape defined by removing a portion of the sheet in a larger amount than in the diffusion sheet by a circular arc which projects outward. In a second of the lens sheets, a tip end of a corner portion formed by two sides has a shape defined by removing a larger amount than in the first of the lens sheets along a straight line.