Layered Thermosettable Adhesive Tape for UV-Cured Black Bonding
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Solution Overview
Problem
Existing adhesive tapes used to bond substrates like rear view mirror brackets to automotive windshields face challenges in achieving a black color after heat curing due to the inability to adequately UV photo-polymerize thick layers loaded with pigment, which weakens the windshield and is aesthetically undesirable.
Innovation Solution
A thermosettable adhesive tape is designed with a thin, highly pigmented layer laminated to a thicker layer with low pigment, allowing UV radiation to penetrate and cure the adhesive, maintaining a black color after heat curing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick adhesive layer is used to provide structural bonding, then the bonding strength is improved, but the UV photo-polymerization is insufficient and the pigment cannot be adequately distributed
Solution Approach 1:
The adhesive tape is divided into multiple layers with different functions: a thin first layer (3-8 mils) containing high pigment concentration for color, and a thicker second layer (15-30 mils) with low or no pigment for structural bonding. This segmentation allows each layer to be optimized independently - the thin first layer enables complete UV penetration and polymerization while providing black color, and the thick second layer provides the required bonding strength.
Solution Approach 2:
Different regions of the adhesive tape have different properties: the first layer near the substrate interface has high pigment concentration for aesthetic appearance, while the second layer away from the interface has low pigment concentration for optimal UV curing and bonding performance. This local differentiation resolves the contradiction between color requirements and bonding requirements.
2Ease of manufacture
If a thick adhesive layer is loaded with black pigment to maintain color after curing, then the black color is preserved, but UV radiation cannot penetrate adequately for complete photo-polymerization
Solution Approach 1:
The pigment is segregated into the first thin layer rather than being distributed throughout the entire thick adhesive layer. This allows the UV radiation to penetrate the thin pigmented layer effectively for complete polymerization, while still achieving the desired black color appearance from the substrate side.
Solution Approach 2:
The solution moves from a single-dimensional approach (one thick layer) to a multi-dimensional approach (multiple layers with gradient pigment distribution). By creating a layered structure with varying pigment concentrations through the thickness, the patent simultaneously achieves color maintenance and UV penetration.
3Manufacturing precision
If a thin adhesive layer is used to enable complete UV polymerization, then the photo-polymerization is complete, but the bonding strength is reduced
Solution Approach 1:
The patent merges a thin first adhesive layer with a thicker second adhesive layer to combine their respective advantages. The thin first layer ensures complete UV polymerization, while the thicker second layer contributes to the overall bonding strength, achieving both complete curing and adequate bond strength.
Solution Approach 2:
The adhesive tape uses a composite structure with two different adhesive compositions: the first layer contains high pigment concentration optimized for color and UV curing, while the second layer contains low or no pigment optimized for bonding performance. This composite structure allows each layer to fulfill its specific function.
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 solution enables the adhesive tape to maintain a black color after curing while providing structural bonding, without weakening the windshield, by using a thin, pigmented layer that allows complete UV polymerization.
Implementation Method 1
The starting materials for each adhesive layer comprises at least a photo-polymerizable acrylic component (e.g., with ultraviolet light) and a thermosettable (e.g., heat curable) epoxy component
Implementation Method 2
The thermosettable adhesive (i.e., a first adhesive) used for one of the adhesive layers (i.e., a first adhesive layer) includes a black coloring pigment (e.g., carbon black)
Implementation Method 3
The curable epoxy resin can be, or the mixture of epoxy resins can include, a heat curable epoxy resin. The starting materials for either or both of the adhesive layers can include a heat curable epoxy resin. When a heat curable epoxy resin is used, a heat-activatable hardener can be included in the applicable starting materials.
Data Source
AI summary
A thermosettable adhesive taped article comprising at least first and second adhesive layers bonded together. Each of the adhesive layers comprises a thermosettable adhesive, which is the photo-polymerization reaction product of starting materials. The starting materials for each adhesive layer comprises at least a photo-polymerizable acrylic component and a thermosettable epoxy component. The thermosettable adhesive, used for either of the two adhesive layers, is not black when fully cured without the presence of a black coloring pigment. The first adhesive layer is made from a layer of starting materials that is thin enough to allow substantial photo-polymerization of the starting materials, even with the starting materials containing a sufficient amount of a black coloring pigment to cause the first adhesive to have a black color after the first adhesive is substantially cured. The second adhesive layer is made from a layer of starting materials which has a thickness that would be sufficiently thick to prevent substantial photo-polymerization (e.g., with UV light) of the starting materials, if the starting materials contained enough of a black coloring pigment to cause the second adhesive to have a black color after the second adhesive is cured.