UV-Curable Dam Composition for Image Display Sealing
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Solution Overview
Problem
UV curable resin compositions used as sealants in image displays tend to exhibit fluidity, leading to squeezing out of the display component, and existing dam materials lack detailed descriptions of hardness and adhesion properties, with conspicuous joints forming between the dam frame and sealant.
Innovation Solution
An image display sealant dam composition comprising a polyorganosiloxane with a mercaptoalkyl group, an aliphatic unsaturated group-containing polyorganosiloxane, a photoreaction initiator, an aliphatic unsaturated group-containing silane compound, and hexamethyldisilazane-treated fumed silica, which forms a dam frame with appropriate hardness and adhesion, and inconspicuous joints with the sealant.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV curable resin composition is applied as sealant, then sealing function is achieved, but the composition exhibits fluidity and squeezes out of display component
Solution Approach 1:
A dam frame is formed in advance on the display component or protective component before applying the sealant composition. This preliminary structure prevents the sealant from squeezing out during curing while maintaining the sealing function.
Solution Approach 2:
The viscosity of the sealant composition is controlled within a specific range (100-10,000 cP at 23°C) to balance fluidity for proper application and resistance to squeeze-out. The composition also exhibits thixotropic behavior with a viscosity ratio V6rpm/V12rpm of 1.05-2.0, becoming more viscous under higher shear stress to prevent extrusion.
2Object-generated harmful factors
If dam material is added to sealant composition, then squeeze-out is prevented, but joints between dam frame and sealant become conspicuous
Solution Approach 1:
The dam frame composition and the sealant composition are designed to have matching optical properties, specifically refractive index and transparency. This homogeneity ensures that when the sealant is applied inside the dam frame, the joint between them is inconspicuous and the overall appearance is uniform.
Solution Approach 2:
Both the dam frame and sealant are formulated as UV-curable silicone resin compositions with complementary chemical components (polyorganosiloxane, aliphatic unsaturated group-containing polyorganosiloxane, photoreaction initiator). This composite approach ensures compatible curing characteristics and optical properties while providing distinct functional roles.
3Shape
If existing dam materials are used, then frame structure is formed, but hardness and adhesion properties are insufficient
Solution Approach 1:
The composition includes specific ratios of polyorganosiloxane (A) with mercaptoalkyl groups to aliphatic unsaturated group-containing polyorganosiloxane (B), with the ratio of mercaptoalkyl groups to aliphatic unsaturated groups controlled at 0.5-4.0. This chemical parameter optimization ensures adequate crosslinking density for hardness while maintaining adhesion to adherends.
Solution Approach 2:
The dam frame composition combines multiple silicone resin components with a photoreaction initiator to create a composite material system that achieves both structural integrity (hardness) and bonding strength (adhesion) after UV curing, overcoming the limitations of simpler dam 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
The composition achieves good adhesion and viewability in image displays by preventing sealant squeeze-out and forming inconspicuous joints, ensuring high transparency and stability of the cured products.
Implementation Method 1
a photoreaction initiator (C)
Data Source
AI summary
The invention provides dam compositions which can give cured products serving as dam materials exhibiting appropriate hardness and adhesion with respect to adherends and which are preferably such that the dam materials also have inconspicuous joints with fillers. The invention also provides image displays manufactured with the compositions. An image display sealant dam composition includes (A) a polyorganosiloxane having a mercaptoalkyl group bonded to a silicon atom, and having a viscosity at 23°C of 20 to 25000 cP; (B) an aliphatic unsaturated group-containing polyorganosiloxane including an aliphatic unsaturated group-containing linear polyorganosiloxane (B1) represented by Formula (I) and optionally further including a branched polyorganosiloxane (B2) having SiO4/2 units, R'3SiO1/2 units and R'2SiO2/2 units, and optionally further having R'SiO3/2 units, at least three R' groups per molecule of the branched polyorganosiloxane (B2) are aliphatic unsaturated groups; (C) a photoreaction initiator; (D) an aliphatic unsaturated group-containing silane compound; and (E) a fumed silica having a BET specific surface area of 180 to 500 m2/g. In the composition, the ratio of the number of the mercaptoalkyl groups present in (A) to the total number of the aliphatic unsaturated groups in (B) and (D) is 0.45 to 1.50; the amount of (E) is 0.5 to 24 parts by weight per 100 parts by weight of (B); and the composition has a viscosity at 23°C of 20,000 to 10,000,000 cP. An image display includes an image display component and a protective component sealed with the composition.