Polycarbonate Resin Composition for Thin Light Guide Plates

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Solution Overview

Problem

Polycarbonate resin compositions face challenges in achieving high light transmittance while maintaining mechanical strength and heat resistance, particularly in thin light guide plates for liquid crystal display devices, where conventional materials like PMMA are insufficient.

Innovation Solution

A polycarbonate resin composition is developed by combining polycarbonate with 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane, along with antioxidants, hydrolysis-resistant agents, and brightness-improving agents, to enhance optical properties and prevent yellowing and mold adhesion, thereby improving light transmittance and mechanical strength.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If polycarbonate is used as a material for thin light guide plates, then mechanical strength and heat resistance are improved, but light transmittance deteriorates

Engineering Contradiction:
Improvemechanical strengthVSAvoidlight transmittance
Core Design Contradiction:
StrengthVSIllumination intensity

Solution Approach 1:

The patent combines polycarbonate with specific additives including 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane, antioxidants, hydrolysis-resistant agents, and brightness-improving agents to create a composite resin composition. This composite approach allows the material to maintain the mechanical strength and heat resistance of polycarbonate while improving light transmittance through the synergistic effects of the additives, directly resolving the contradiction between strength and optical clarity.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent optimizes specific parameters of the polycarbonate resin composition, including the weight average molecular weight (10,000 to 30,000), the amount of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane (0.01 to 0.3 parts by weight per 100 parts of polycarbonate), and the concentrations of other additives. By precisely controlling these parameters, the material achieves both high mechanical strength and improved light transmittance, resolving the performance contradiction.

Inventive Principle:
Principle #35Parameter changes

2Temperature

If polycarbonate is used instead of PMMA, then heat resistance and mechanical strength are improved, but light transmittance deteriorates

Engineering Contradiction:
Improveheat resistanceVSAvoidlight transmittance
Core Design Contradiction:
TemperatureVSIllumination intensity

Solution Approach 1:

The patent creates a composite resin composition by combining polycarbonate with 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane and other functional additives. This composite structure preserves the excellent heat resistance of polycarbonate while the specific additives compensate for its lower light transmittance compared to PMMA, achieving a balance suitable for thin light guide plates in LED backlight units.

Inventive Principle:
Principle #40Composite materials

Solution Approach 2:

The patent introduces 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane as an intermediary substance that mediates between the conflicting requirements of heat resistance and light transmittance. This additive acts as a modifier that allows polycarbonate to achieve PMMA-level light transmittance while maintaining its superior heat resistance and mechanical properties.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Length of moving object

If light guide plate thickness is reduced, then device thinning is achieved, but mechanical strength becomes insufficient

Engineering Contradiction:
Improveplate thicknessVSAvoidmechanical strength
Core Design Contradiction:
Length of moving objectVSStrength

Solution Approach 1:

The patent optimizes the resin composition parameters, including using polycarbonate with weight average molecular weight of 10,000 to 30,000 and adding specific amounts of 1,1,5,5-tetramethyl-3,3-diphenyltrisiloxane (0.01 to 0.3 parts by weight per 100 parts of polycarbonate) and other additives. These parameter changes enhance the mechanical strength and optical properties of the thin plate, enabling the use of ultra-thin light guide plates (0.3 to 0.5 mm) while maintaining sufficient strength.

Inventive Principle:
Principle #35Parameter changes

Data Source

PatentEP3375823B1Polycarbonate resin composition
Publication Date: 2019.07.24 LG CHEM LTD

AI summary

The present invention relates to a polycarbonate resin composition. The polycarbonate resin composition exhibits excellent optical properties, and thus can be used as a material for a light guide plate.