Investigations into the production of achromatic lenses by two-component injection compression molding of transparent plastics

与许多光学等级的玻璃相比，塑料具有高色散。这意味着材料的折射率随着波长的增加而更强烈地降低。结果，由光学透镜聚焦的不同波长的光（光色）具有不同的焦点位置。这导致图像误差和模糊的图像，这就是为什么成像光学系统通常由几个组合透镜组成的原因。在照明光学中，色散是通过光锥边缘的色幕来表现的，通过将两个由不同色散材料制成的透镜组合成消色差透镜，可以减小这种色差，从而显著提高成像性能。为了提高图像质量，塑料透镜系统通常由几个透镜组装而成。这需要生产多个部件、精确定位和进一步的组装步骤。因此，该项目专注于将第二个部件注射到具有低翘曲和收缩的预制件上，以生产由不同透明塑料制成的消色差透镜。用于组合的可能的塑料是聚碳酸酯（PC）和聚（甲基丙烯酸甲酯）（PMMA）。除了减少进一步的加工和组装步骤外，双组份注塑成型还通过减少界面处的反射来提高透射率。本研究项目将从消色差透镜的应用出发，对具有大接触面的低收缩和低翘曲双组份注塑压缩成型的生产策略进行一般推导。除了光学之外，这些知识还与许多其他应用相关。然而，光学部件的这种双组分注射成型的先决条件特别具有挑战性。第二组分必须以非常小的收缩被注射到预成型件上，第二组分的注射过程不应使第一组分表面变形，并且必须确保两种塑料在大表面上的充分粘附。这些点将通过适当的注射压缩成型工艺来实现。在该过程中通过压花对熔体进行适当的压缩应尽可能减少注射部件的后续收缩。系统地研究了工艺参数对薄膜的附着力、收缩率、界面形状、折射率以及器件性能的影响。

Compared to many optical grades of glass, plastics have a high dispersion. This means that the refractive index of the material decreases more strongly with increasing wavelength. As a result, different wavelengths of light (light colors), which are focused by an optical lens, have different focal positions. This leads to image errors and blurred images, which is why imaging optics are usually composed of several combined lenses. In illumination optics, the dispersion is shown by a color veil on the edge of the light cone.By combining two lenses made of materials with different dispersions to form an achromatic lens, this chromatic aberration, can be reduced, resulting in a significant increase in imaging performance. To improve image quality, plastic lens systems are usually assembled from several lenses. This requires the production of several components, exact positioning and further assembly steps.The project therefore focuses on injecting a second component onto a preform with low warpage and shrinkage to produce an achromatic lens from different transparent plastics. Possible plastics for the combination are polycarbonate (PC) and poly(methyl methacrylate) (PMMA). In addition to reducing further processing and assembly steps, two-component injection molding also increases transmission by reducing reflections at the interfaces.From the application of an achromatic lens, the general derivation of a production strategy for low-shrinkage and low-warpage two-component injection compression molding with large contact surfaces is to be carried out in the research project. In addition to optics, this knowledge is relevant for numerous other applications. Nevertheless, the prerequisites for this two-component injection moulding of optical components are particularly challenging. The second component must be injected onto the preform with very little shrinkage, the injection process of the second component should not deform the first component surface and sufficient adhesion of the two plastics over a large surface must be ensured. These points are to be achieved by an adapted injection compression molding process. An adapted compression of the melt in the process by means of embossing should reduce subsequent shrinkage of the injected component as far as possible. The influences of the process parameters on adhesion, shrinkage, the shape of the interface and the refractive index as well as the component properties are systematically investigated.