Injection Compression Molding
The process of injection molding with dynamic mold temperature control leads to a good replication quality of high-aspect-ratio microstructures. However, an inhomogeneous pressure distribution during the holding pressure phase results in an anisotropy of the component properties, low dimensional accuracy and, especially with optical polymers, an undesired stress birefringence (55).
The anisotropy is based on the orientation of the molecular chains in the flow direction, which can be reduced by an injection-compression molding (ICM) process. In order to use the synergy from both processes, an injection-compression molding process with dynamic mold temperature control can be utilized.
This process was reproduced by an ICM process at elevated mold temperature and compared with injection molding with regard to molding accuracy and optical properties in dependence of component thickness and mold temperature (55). In order to evaluate the molding accuracy, the roughness of a wire-eroded microstructure on the cavity surface was measured.
To determine the degree of orientation, the optical properties considered were the transmission and the path difference. It could be shown that the adapted ICM process was able to achieve a high degree of replication accuracy with a low degree of orientation, especially for thin-walled components. ICM at elevated mold temperature reduced the path difference in the components with the lowest wall thickness by a factor of two while at the same time optimizing the replication of the microstructure. This could also be confirmed by transmission measurements (55).
1.13 Hot Press System
In conventional mold fabrication techniques, hot pressing techniques are typically applied to the fabrication of shoe soles (56). After selecting the appropriate mold for the fabrication of a shoe sole, a mixture of a foaming agent is added and heated, and the sole is formed after the mold is cooled. Hence, the temperature control of the mold in the hot pressing process is an important controlling factor.
The heating of a shoe sole mold is performed via a hot plate, wherein the shoe sole mold is placed on a hot plate with a hot liquid tunneling through and the shoe sole mold is heated via heat conduction. However, relying upon the conduction method for heat conduction is time consuming. Furthermore, the surface of the mold used in hot pressing is closer to the hot plate, and that mold surface is heated faster than other areas of the mold, resulting in an overall uneven heating. In addition, the heat emitted from the hot plate is not absorbed solely by the neighboring regions of the hot pressed surface. Consequently, the power consumption is increased.
The current technology further includes directly incorporating a heating unit in the mold. However, such a mold necessitates a reconnection of the wirings of the hot plate when the mold is being replaced; hence, the mold replacement process becomes more complicated. Furthermore, incorporating a heating unit in the mold increases the fabrication cost and the removable heating pipelines also present safety issues (56).
So, a mold thermal controlling device for efficiently heating or cooling a mold was developed (56). Figure 1.5 is a schematic view illustrating a mold thermal controlling device and a mold.
The injection end 232 and the discharge end 234 pierce through the first temperature control layer, and the heated or cold liquid is injected through the injection end 232 and is discharged from the discharge end 234. Since the replacement of the mold 110 does not require any changes to the temperature control tunnel 230, deterioration of the temperature control tunnel 230 due to frequent changing is reduced, and safety and the replacement efficiency are improved.
In particular, the mold thermal controlling device includes a first trench, a first temperature control layer and at least a temperature control tunnel. The first temperature control layer includes a first temperature control face and the first temperature control layer forms a first temperature control trench forming the inner surface of a part of the first trench. The first temperature control trench is used for accommodating or containing a mold and is in contact with the mold through the first temperature control face. The temperature control tunnel is disposed in the first temperature control layer. A heated fluid or a cold fluid is injected into the temperature control tunnel. When the mold is placed in the first temperature control trench, the first temperature control face is positioned between the mold and the temperature control tunnel.
Figure 1.5 Mold thermal controlling device (56).
The mold thermal controlling device further includes a first surface having a first trench, and the opening of the first trench is positioned at the first surface. The cross-sectional area of the first trench tapers from the opening of the first trench along the first direction, and the mold is placed in or removed from the first trench along the first direction.
The mold thermal controlling device applies a pressure to the mold along the first direction. The surfaces of the mold that is in contact with the first temperature control layer protrudes and concaves along the first direction, and the cross section of the opening of the first trench tapers along the first direction. The mold is placed in or removed from the first trench along the first direction.
Since the mold thermal controlling device includes a temperature control tunnel that is formed with the temperature control layer, the temperature control tunnel can efficiently heat or cool the mold placed therein. Moreover, the mold used with the mold thermal controlling device can be easily replaced, and there are structures that may be included in or on the mold to assist the positioning of the mold, the gas discharge or to perform a grabbing action. Additionally, the mold thermal controlling device may be applied to an automated fabrication process. Since the hot press system of the disclosure includes the above mold thermal controlling device, which can provide heating or cooling with high efficiency, the hot press system of the disclosure can be broadly applied to various hot pressing processes (56).
1.14 Stamper Mold
1.14.1 Recoding Media
A stamper for forming a data recording region on a recording medium substrate by means of a transfer surface thereof has been described (57). The transfer surface transfers a predetermined set of data to the recording medium substrate. The stamper is fitted on at least one of the metal molds that are arranged opposite one another for forming the recording medium substrate. The stamper includes a stepped portion formed as bends in the material of the stamper. The stepped portion is configured to project from the transfer surface toward the recording medium substrate.
The substrate may be produced through common injection molding processes and photopolymer processes. The injection molding process is a process in which an acrylic or a PC resin melted by a plasticizer of a molding device is filled into a cavity of a mold fitted with a master disc having microscopic projection/recess patterns for recording/retrieving signals, and the resulting substrate is removed from the mold after the molten resin cools down and is solidified (57).
1.14.2 Microscopic Structured Body
A polymer molded product with a fine structure has been increasingly utilized in various fields such as electronic devices, optical devices, recording media, and medical devices (58). Various methods for manufacturing such a molded product with fine structure have been proposed but attention has been attracted to a UV and thermal nanoimprint method owing to high economic efficiency and
