Epoxy Resin Composition for LED Encapsulation
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Solution Overview
Problem
Conventional epoxy resin compositions used for encapsulating LEDs require curing accelerators, which degrade under long-term heat and light, leading to color changes and poor workability due to high viscosity and curing rates.
Innovation Solution
An epoxy resin composition with cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride (H-TMAn) and alicyclic epoxy resin compounds in specific ratios, along with a hindered phenol-based antioxidant, to achieve low viscosity, self-curing, and excellent light fastness without the need for accelerators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alicyclic acid anhydride is used as a curing agent for epoxy resin, then the epoxy resin cured product is colorless and transparent, but the curing reactivity is low and requires addition of curing accelerator
Solution Approach 1:
The patent uses H-TMAn as an intermediary curing agent that mediates between the need for colorless transparency and adequate curing reactivity. It provides sufficient reactivity without requiring accelerators while maintaining the colorless and transparent properties of the cured epoxy resin.
Solution Approach 2:
The patent changes the chemical structure parameter of the acid anhydride from conventional alicyclic types to H-TMAn, which has a specific molecular structure that provides both adequate curing reactivity and maintains colorless transparency in the cured product.
2Productivity
If curing accelerator is added to improve curing reactivity, then the curing rate increases, but the curing accelerator changes to yellow color under long-term heating and impairs colorless and transparent nature
Solution Approach 1:
The patent extracts and eliminates the curing accelerator component from the system by using H-TMAn as a self-sufficient curing agent that provides adequate reactivity without requiring external accelerators, thereby removing the source of yellowing under long-term heating.
Solution Approach 2:
H-TMAn serves as a self-sufficient curing agent that provides its own curing capability without needing external accelerators. It maintains colorless transparency under long-term heating while achieving adequate curing reactivity on its own.
3Reliability
If epoxy resin composition contains high viscosity and high curing rate, then curability is improved, but workability deteriorates due to high degree of viscosity increase in standing
Solution Approach 1:
The patent optimizes the viscosity parameter by selecting H-TMAn as the curing agent, which maintains low viscosity of the epoxy resin composition while providing adequate curing reactivity. This balance ensures both good workability during application and satisfactory curability.
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
The composition maintains low viscosity, ensures colorless and transparent curing, and provides crack resistance with minimal color change under long-term light and heat exposure, enhancing workability and performance as an encapsulant for LEDs.
Implementation Method 1
an epoxy resin composition which includes: acid anhydrides (A); and epoxy resins (B)... a cured product of the composition
Implementation Method 2
further including 0.1 to 5 mass% of a hindered phenol-based antioxidant... changes its color to a small extent with long-term light irradiation and heating
Data Source
AI summary
Provided are an epoxy resin composition including acid anhydrides (A) and epoxy resins (B), in which: (a) cyclohexane-1,2,4-tricarboxylic acid-1,2-anhydride accounts for 50 to 90 mass% of the acid anhydrides (A); (b) an alicyclic epoxy resin compound accounts for 30 to 90 mass% of the epoxy resins (B) and an epoxy resin compound represented by the following general formula (1) accounts for 10 to 50 mass% of the epoxy resins (B); and (c) contents of the acid anhydrides (A) and the epoxy resins (B) are such that a blending equivalent ratio between the acid anhydrides and the epoxy resins ranges from 0.4 to 0.7, a cured product of the composition, and a light-emitting diode. The epoxy resin composition has the following characteristics. That is, (1) the composition has a low viscosity after the mixing, a low degree of viscosity increase in standing at room temperature, and excellent workability, (2) the composition has satisfactory curability even when no curing accelerator is added, and (3) a cured product is colorless and transparent, has crack resistance, and changes its color to a small extent with long-term light irradiation and heating. The composition is suitable for an encapsulant for a photoelectric conversion element such as a blue LED or white LED. (In the formula, R's each independently represent a hydrogen atom or a methyl group, m represents an integer of 1 to 3, and n represents an integer of 2 to 8.)