Circularly polarized light extraction optical element and method of manufacturing optical element

Abstract

A circularly polarized light extraction optical element (10) capable of effectively suppressing the lowering of the display quality of a display caused by light-dark patterns appearing on the display surface of the display even when a circularly polarized light plate and an elliptically polarized light plate are brought into a cross nicol state and the circularly polarized light extraction optical element is disposed therebetween, and providing a circularly polarized light having a continuous selectively reflected wave zone without optical singular point even when the circular polarized light extraction optical element is manufactured by stacking a plurality of liquid crystal layers each other, comprising a liquid crystal layer (12) planar-disposed and having a cholesteric ordinality, wherein two major surfaces (12A) and (12B) of the liquid crystal layer (12) opposed to each other are substantially identical to each other in the directions of directors (Da, Db) of liquid crystal molecules through the entire area of the surfaces (12A, 12B) and, when the liquid crystal layer (12) is formed of the plurality of liquid crystal layers, the directions of the directors of the liquid crystal molecules should desirably be substantially parallel with each other near the boundary of the liquid crystal layers adjacent to each other.

Description

technical field [0001] The present invention relates to an optical element for extracting circularly polarized light from non-polarized light using a liquid crystal layer having cholesteric regularity, a manufacturing method thereof, a polarized light source device and a liquid crystal using the optical element for extracting circularly polarized light display device. In addition, in this specification, the term "liquid crystal layer" is used in the sense of a layer having optical liquid crystal properties, and the state of the layer includes not only the state of a fluid liquid crystal phase, but also The molecular alignment of the liquid crystal phase is maintained and solidified. Background technique [0002] Generally, as an optical element using a cholesteric liquid crystal or the like, one of the left-handed or right-handed circularly polarized light components of a wavelength corresponding to the helical pitch of the liquid crystal molecules in the cholesteric liquid...

AI Technical Summary

Problems solved by technology

[0009] However, when using a binder, the liquid crystal molecules of the thinned liquid crystal layer and the molecules of the binder must have good adhesion, which not only limits the type of binder, but also makes it difficult to extract The thickness of circularly polarized optical elements will increase the thickness of the adhesive layer problem

In addition, there is also a problem that the difference in the refractive index between the adhesive layer and the liquid crystal layer causes reflection at the interface between the two, so that the light extracted from the circularly polarized light extraction optical element is attached to the adhesive. the layer's own color, etc.

[0010] In addition, when thermal bonding is performed without using an adhesive, in order to make the thinned liquid crystal layer flexible, it is necessary to heat it above the glass transition temperature (Tg), so that there is thermal bonding. Problems that are difficult to use industrially in terms of configuration and operation of junction devices

In addition, there is a problem that due to high-temperature heating, the liquid crystal molecules of the liquid crystal layer and the liquid crystal molecules of the adjacent liquid crystal layer are randomly mixed, which will cause a decrease in optical characteristics.

[0011] Furthermore, regardless of the situation of using an adhesive or not using an adhesive, in order to orient the liquid crystal molecules in the same plane, an orientation film and a base layer must be used, so there is a possibility that the optical element for extracting circularly polarized light will increase the a thickness problem

Also, regarding this point, when stretched films such as stretched PET (polyethylene terephthalate) films are used as the base layer, the orientation film is omitted because the stretched film itself has the function of an orientation film. It becomes possible, however, to extract the thickness of the circularly polarized optical element by increasing the thickness of this portion of the stretched film

In addition, there is a problem that after the liquid crystal is solidified, the alignment film and the base layer may fall off, and the liquid crystal layer is mostly damaged when falling off, which reduces the possibility of mass production

Furthermore, there is a problem that when the liquid crystal layer is laminated with more than 3 layers, using any of the above methods will make the process quite complicated, and the base layer and alignment film of this part of the number of layers will become wasteful.

[0013] However, there is a problem in this method that it is difficult to always maintain the helical axis of the cholesteric liquid crystal molecules in each liquid crystal layer.

In addition, because the cholesteric liquid crystal polymer is simply coated, the orientation direction of the liquid crystal molecules near the interlayer interface of adjacent cholesteric liquid crystal polymers is not uniquely determined, and the cholesteric liquid crystal polymer In the interlayer interface, faults occur in the direction of the director dipole of the liquid crystal molecules, thereby degrading the optical performance as an optical element for extracting circularly polarized light

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