Transparent Watch Component Shaping via UV Photopolymerization

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Solution Overview

Problem

Molded transparent plastic components for timepieces are thick, lack wear resistance, and cannot be produced with sharp angles due to low durability, limiting their use in exterior components.

Innovation Solution

A process using a mixture of trimethylolpropane tri(methacrylate) and pentaerythrityl tetraacrylate with additives, polymerized under controlled conditions including UV exposure, to create a one-piece, transparent watch component with enhanced surface hardness and wear resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If traditional molded plastic materials are used for transparent components, then production cost is low and manufacturing is easy, but the components are thick, have poor wear resistance, and cannot maintain sharp angles

Engineering Contradiction:
Improvesharp angles and thin profilesVSAvoidwear resistance
Core Design Contradiction:
Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the chemical composition parameters of the molding material by using a specific mixture of trimethylolpropane tri(methacrylate) and pentaerythrityl tetraacrylate with controlled ratios, which fundamentally alters the material properties to achieve both thin profiles with sharp angles and high wear resistance simultaneously

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite material system by combining two different monomers (trimethylolpropane tri(methacrylate) and pentaerythrityl tetraacrylate) in specific proportions, leveraging the complementary properties of each component to achieve superior wear resistance while maintaining the ability to form sharp angles and thin sections

Inventive Principle:
Principle #40Composite materials

2Reliability

If traditional molded plastic materials are used, then production is economical, but the components lack durability and scratch resistance for exterior use

Engineering Contradiction:
Improvedurability and scratch resistanceVSAvoidmanufacturing complexity
Core Design Contradiction:
ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces traditional mechanical molding processes with a chemical polymerization process using UV irradiation, which eliminates the need for complex mechanical molds and allows for more intricate geometries including sharp angles while maintaining ease of production

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the manufacturing process parameters by using photopolymerization with specific UV irradiation conditions (intensity and duration), which simplifies the manufacturing process while achieving superior durability and scratch resistance in the final component

Inventive Principle:
Principle #35Parameter changes

3Volume of moving object

If very thin transparent components are molded, then material usage is reduced and design flexibility increases, but quality and reproducibility deteriorate

Engineering Contradiction:
Improvecomponent thicknessVSAvoidquality and reproducibility
Core Design Contradiction:
Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent replaces mechanical injection molding with UV photopolymerization, which allows for precise control of thin section formation through light penetration depth control, enabling consistent quality and reproducibility in very thin components that would be difficult to achieve with traditional mechanical molding

Inventive Principle:
Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent uses controlled UV irradiation with specific time intervals and intensity levels to progressively cure the material from the surfaces inward, ensuring uniform quality and reproducibility even in very thin components by controlling the polymerization process in stages

Inventive Principle:
Principle #19Periodic action

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 process achieves high-dimensional precision and improved wear resistance, allowing for the production of transparent components with sharp angles that are durable and resistant to scratches, surpassing the limitations of traditional molded plastic materials.

Implementation Method 1

a first transparent and polymerizable molding material is chosen for the production of said component

Methodology Applied
Scientific EffectPolymerization:

Implementation Method 2

said first material injected into said cavity is subjected, during its polymerization, to a temperature of between 100° C. and 120° C., for 10 to 20 seconds

Methodology Applied
Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentEP2764410B1Shaping of an integral transparent clock component
Publication Date: 2017.08.30 ETA SA MFG HORLOGERE SUISSE
  • EP2764410B1 patent drawingFigure 1~6
  • EP2764410B1 patent drawingFigure 2~5

AI summary

The invention relates to a method for forming a transparent timepiece component (1) comprising upper (2) and lower (3) surfaces, in which: a polymerisable transparent material (5) is selected; a flexible female mould (9) is applied to a plate (15), wherein one contact surface (10) of the mould is the negative of the above-mentioned lower surface (3) and is bordered by a rim (11), said mould (9) comprising a capillary network (14); a cavity (17) is formed by means of the sealed abutment of the rim (11) against a plate (6) of which one contact surface (7) is the negative of the above-mentioned upper surface (2); the cavity (17) is filled with material (5) that is injected through the capillary network (14); the material (5) is polymerised in order to obtain a rigid component (1); and the component (1) is detached from the plates by deforming the flexible mould (9). Hardness is enhanced by insulating the component (1) against UV.