Photocurable Silicone Resin Thin Film Curing Method

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Solution Overview

Problem

Existing photocurable silicone resin compositions for thin films face challenges in achieving desired thickness and shape precision due to slow curing rates and susceptibility to heat and light, leading to unsatisfactory heat resistance and light resistance of the cured products.

Innovation Solution

A method involving a photocurable silicone resin composition with an organopolysiloxane having alkenyl groups, an organohydrogenpolysiloxane, and a photoactive catalyst, where the composition is partially cured using light through a mask to form a semi-cured pattern, followed by heat curing to achieve complete curing, with light irradiation having a maximum peak between 300-400 nm and minimal spectral irradiance below 300 nm.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a photocurable silicone resin composition is used to achieve rapid curing, then the curing rate is improved and production line control is easier, but the heat resistance and light resistance of the cured product deteriorate due to weak crosslinking points

Engineering Contradiction:

Improvecuring rateVSAvoidheat resistance and light resistance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The curing process is divided into two distinct stages: a photocuring stage that provides rapid initial curing and pattern formation, followed by a thermal curing stage that completes the curing and develops heat resistance and light resistance. This segmentation allows each stage to optimize for its specific function without compromising the other.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The photocuring step performs the preliminary action of forming the cured pattern and achieving sufficient curing to prevent flow, which allows the subsequent thermal curing to focus on developing the final heat and light resistance properties without worrying about maintaining shape or thickness precision.

Inventive Principle:

Principle #10Preliminary action

2Manufacturing precision

If a three dimensional network structure silicone resin is used to reduce fluidity, then the desired thickness and pattern precision is improved, but the curing time increases and production efficiency decreases

Engineering Contradiction:

Improvethickness and pattern precisionVSAvoidcuring time

Core Design Contradiction:

Manufacturing precisionVSProductivity

Solution Approach 1:

The patent replaces reliance on mechanical/chemical viscosity control (three dimensional network structure) with optical energy input (photocuring) to achieve rapid curing. The photocuring initiates polymerization that quickly increases viscosity and prevents flow, eliminating the need for pre-designed high-crosslinking structures that would slow down the overall curing process.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If high-temperature heating is used to achieve rapid curing, then the curing rate is improved, but the production line control becomes difficult and molded article quality deteriorates

Engineering Contradiction:

Improvecuring rateVSAvoidproduction line control

Core Design Contradiction:

ProductivityVSEase of manufacture

Solution Approach 1:

The patent substitutes thermal energy (heating) with optical energy (light irradiation) as the primary curing mechanism. Photocuring occurs rapidly at ambient or moderate temperatures when exposed to light of appropriate wavelength, providing precise control over the curing process without the thermal runaway or control difficulties associated with high-temperature heating.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

4Manufacturing precision

If a photocurable composition with polyhedral siloxane structure is used to achieve lithography properties, then the pattern formation capability is improved, but the heat resistance and light resistance deteriorate due to susceptibility of crosslinking points to damage

Engineering Contradiction:

Improvepattern formation capabilityVSAvoidheat resistance and light resistance

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent employs a composite curing approach combining photocuring and thermal curing mechanisms. The composition contains photopolymerizable functional groups for light-induced curing and silane groups for thermal curing, creating a dual-cure system that achieves both pattern precision and environmental resistance.

Inventive Principle:

Principle #40Composite materials

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 method enables the formation of thin films with precise thickness and shape, excellent heat resistance, and optical transparency, suitable for encapsulating optical semiconductor elements like LEDs, with improved workability and pot life of the resin composition.

Implementation Method 1

a photocurable composition comprising a polysiloxane-based compound having a polyhedral siloxane structure containing a photopolymerizable functional group and an SiH group, an alkenyl group-containing compound, a photopolymerization initiator and a hydrosilylation catalyst

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Implementation Method 2

curing upon heating generally employ a platinum catalyst as a curing catalyst

Methodology Applied

Scientific EffectThermal curing: Heating

Implementation Method 3

a polysiloxane-based compound having a polyhedral siloxane structure containing a photopolymerizable functional group and an SiH group, an alkenyl group-containing compound

Methodology Applied

Scientific EffectHydrosilylation: Chemical Bonding

Data Source

PatentEP2570463B1Method of producing cured thin film using photocurable silicone resin composition

Publication Date: 2015.02.25 SHIN ETSU CHEMICAL CO LTD

Figure 1

AI summary

A method of producing a cured thin film that enables a desired cured thin film to be formed easily and with superior precision, by using a silicone resin composition which exhibits lithography properties, and can be cured by a combination of photocuring and heat curing. Specifically, a method of producing a cured thin film by curing a photocurable silicone resin composition containing: (A) an organopolysiloxane having two or more alkenyl groups within each molecule, (B) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms within each molecule, and (C) a photoactive catalyst, wherein the method includes: (i) applying the composition to a substrate, (ii) obtaining a thin film in a semi-cured state by irradiating the applied coating with light, and (iii) heating the thin film in a semi-cured state to achieve complete curing, and wherein the spectrum of the light irradiated in step (ii) has a maximum peak in a wavelength region from 300 nm to 400 nm, and the spectral irradiance of light of any wavelength within the wavelength region shorter than 300 nm is not more than 5% of the spectral irradiance of light of the maximum peak wavelength.