Decorative Sheet Graphic Layer Segmentation for Injection Molding Stability
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Solution Overview
Problem
In printed matters using interference pigments, the graphic patterns deteriorate due to heat and pressure during injection molding, causing changes in the color expressions and image recognition.
Innovation Solution
A decorative sheet with a base film, graphic layers containing interference pigments, an optical functional layer, and an adhesive layer, which enhances light transmission and reflectance properties to maintain color stability and clarity under heat and pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a printed matter uses interference pigments with multiple color binders to achieve wide color expressions, then color variety is improved, but the graphic deteriorates under heat and pressure during injection molding
Solution Approach 1:
The invention divides the graphic into two separate layers: a first graphic layer with first color binder containing interference pigments, and a second graphic layer with second color binder containing interference pigments. Each layer is printed separately and then overlaid during injection molding. This segmentation prevents the binders from mixing and changing the graphic pattern under heat and pressure, while still achieving wide color expressions through the combination of different interference pigments in each layer.
Solution Approach 2:
The invention transitions from a two-dimensional printed graphic to a three-dimensional structure by creating separate first and second graphic layers that are stacked in the thickness direction. The first graphic layer is formed on the decorative sheet before molding, and the second graphic layer is formed during injection molding. This dimensional approach allows each layer to maintain its graphic integrity independently while combining to produce the final color effect.
2Adaptability or versatility
If the degree of overlap of binders is increased to enhance color mixing, then color expression is improved, but the graphic changes under heat and pressure during molding
Solution Approach 1:
The invention segments the color mixing process into two independent stages: the first graphic layer provides a base color pattern with specific interference pigments, and the second graphic layer adds overlay colors with different interference pigments. Each layer uses its own color binder that does not mix with the other, preventing graphic distortion. The final color expression is achieved through optical combination rather than physical mixing of binders.
Solution Approach 2:
The invention applies different color binders with different properties to different layers: the first color binder is designed for the first graphic layer with specific drying and curing characteristics, while the second color binder is designed for the second graphic layer with compatibility to the molten resin. This local optimization ensures each layer maintains its graphic integrity under the specific conditions it encounters during molding.
3Device complexity
If a single graphic layer is used to simplify the structure, then manufacturing complexity is reduced, but color expression variety and graphic stability are compromised
Solution Approach 1:
The invention divides the graphic structure into two independent layers, each with its own color binder and interference pigments. The first graphic layer is formed on the decorative sheet before molding, and the second graphic layer is formed during injection molding. This segmentation enables wide color expression variety while maintaining graphic stability, as each layer independently maintains its pattern under heat and pressure.
Solution Approach 2:
The two-layer graphic structure serves multiple functions: the first graphic layer provides a stable base pattern and color foundation, the second graphic layer adds color variety and depth, and together they achieve wide color expressions while both layers maintain graphic stability under molding conditions. This multi-functional design compensates for the increased structural complexity.
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 decorative sheet effectively suppresses graphic deterioration and maintains clear color expressions and image recognition during injection molding by optimizing light transmission and reflectance.
Implementation Method 1
The first graphic layer contains a plurality of kinds of interference pigments in a first group that emit respective interference lights having a plurality of colors different from one another in a first direction heading from the back surface to the front surface of the decorative sheet in a first binder that transmits visible light to exhibit a first mixed color
Implementation Method 2
The optical functional layer has an optical function that changes a reflectance property of light and transmits visible light. The optical functional layer is configured to have a reflectance property. The reflectance property increases a ratio of at least one of an amount of visible light representing the graphic and an amount of visible light representing the image and passing through the first graphic layer and the second graphic layer
Implementation Method 3
The base film has a first main surface and a second main surface and transmits visible light. The first graphic layer and the second graphic layer are configured such that interference pigments contained in the first group, the interference pigments contained in the second group, the first binder, and the second binder transmit incident light traveling in the first direction to allow visually recognizing an image displayed on a side of the back surface of the decorative sheet from the side of the front surface
Data Source
AI summary
Provided is a decorative sheet in which a graphic is less deteriorated even after injection molding. First and second graphic layers contain a plurality of interference pigments that emit respective interference lights having respective colors in a first direction in first and second binders to exhibit first and second mixed colors. An optical functional layer changes a reflectance property of light. The first and second graphic layers represent a graphic visually recognizable from a front surface of a decorative sheet and allow visually recognizing an image displayed on a back surface from the front surface. The optical functional layer increases at least one of ratios of an amount of visible light representing the graphic and an amount of visible light representing the image that transmits through the first and second graphic layers to an amount of visible light reflected by and visible on the front surface.