Evaporation Device Thermal Screen for OLED Material Protection
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Solution Overview
Problem
In vacuum deposition processes, the uniform heating of crucibles leads to uneven evaporation of materials, causing unnecessary heat exposure and degradation of organic materials, particularly in the manufacture of OLEDs and photovoltaic cells, where materials are thermally sensitive and expensive.
Innovation Solution
An evaporation device with a thermal screen interposed between the crucible and heating means, featuring a movable element that adjusts heat distribution non-uniformly along the crucible, ensuring only the material at the free surface is heated intensely for evaporation, while minimizing heat exposure to the rest of the material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If uniform heating of the crucible is applied, then the material is heated consistently throughout, but the material at the bottom experiences excessive heat exposure leading to degradation
Solution Approach 1:
The thermal screen is designed with variable thickness along the crucible height, creating different thermal insulation properties at different locations. The thickness increases from top to bottom, providing stronger insulation where needed to prevent material degradation while maintaining evaporation efficiency at the free surface.
Solution Approach 2:
The thermal screen acts as an intermediary layer between the heating means and the crucible material. It mediates heat transfer by blocking excessive thermal radiation from reaching the material, particularly protecting the lower portions while allowing sufficient heat to reach the free surface for evaporation.
2Object-affected harmful factors
If the thermal screen thickness is increased to protect material, then material degradation is reduced, but the complexity of the device increases
Solution Approach 1:
The thermal screen thickness is varied as a continuous parameter along the crucible height rather than using discrete layers. This gradient thickness approach provides effective material protection while maintaining a relatively simple single-piece structure that is easier to manufacture and install compared to multi-layer configurations.
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 solution optimizes the use of materials by heating them only when necessary, reducing thermal degradation and maintaining a consistent vapor flow rate, thus enhancing the efficiency and longevity of organic materials during the deposition process.
Implementation Method 1
the heating of the body of the crucible by the heating means takes place essentially by radiation, the vacuum prevailing inside the vacuum chamber reducing the exchanges of heat by convection
Implementation Method 2
The heat shield reflects the other part
Implementation Method 3
the quantity of heat received by the body of the crucible at a considered point of this body conforms, at a given instant, to a non-constant function of the distance between the point considered and the bottom of the crucible
Implementation Method 4
a stream of vapor escapes through the opening of the crucible originating essentially from the free surface of the material to be evaporated close to the opening of the crucible
Data Source
Figure 1
Figure 2~3
Figure 4~5
AI summary
The evaporation device comprises: a crucible (20) that is intended to contain a material to be evaporated and comprises a bottom (21), a body (22) and an opening (23); a heating unit surrounding the body; and a thermal shield (30) interposed between the body and the heating unit. The thermal shield comprises a first element that is designed such that a quantity of heat received by the body of the crucible at a considered point of the body is conform, at a given instant of time, to a non-constant function of the distance between the considered point and the bottom of the crucible. The evaporation device comprises: a crucible (20) that is intended to contain a material to be evaporated and comprises a bottom (21), a body (22) and an opening (23); a heating unit surrounding the body of the crucible; and a thermal shield (30) interposed between the body of the crucible and the heating unit. The thermal shield comprises a first element that is movable with respect to the crucible and is designed such that a quantity of heat received by the body of the crucible at a considered point of the body is conform, at a given instant of time, to a non-constant function of the distance between the considered point and the bottom of the crucible. The function is adjustable with respect to a degree of movability of the first element of the thermal shield with respect to the crucible. A vacuum deposition apparatus has a pressure of lower than 10 -> 3> mbar. The first element is mounted movable in translation with respect to the crucible and in rotation with respect to the crucible. The thermal shield comprises a second element. The first element is movable with respect to the second element, and the first and second elements are arranged to define apertures whose size is adjustable as a function of their relative positions. The device further comprises a control unit adapted to control the first element of the thermal shield to adjust a flow rate of steam of the material to be evaporated through the opening of the crucible, and an additional control unit adapted to control the bottom of the crucible to adjust the flow rate of the material to be evaporated through the opening of the crucible. The flow rate of steam of the material to be evaporated through the opening of the crucible is kept constant. The bottom of the crucible is mounted movable in translation with respect to the body of the crucible.