TW202534357A - Optical structure, anti-reflective device and method for manufacturing such optical structure - Google Patents

Abstract

The present invention relates to an optical structure comprising a linearly polarizing layer (6), a twisted liquid crystal retarder layer (4) being arranged at a polarizer interface (8). A first orientation direction of liquid crystals just within the twisted liquid crystal retarder layer (4) at the polarizer interface (8) is set by the polarizing direction of the polarizing layer (6). Furthermore, the optical structure comprises an alignment layer (3) defining an alignment direction and an alignment interface (7) between alignment layer (3) and either the polarizing layer (6) or the twisted liquid crystal retarder layer (4). Furthermore, the present invention relates to an anti-reflective device comprising such optical structure and a method for manufacturing such optical structure.

Description

Optical structure, anti-reflection device and method for manufacturing the optical structure

The present invention relates to an optical structure comprising an alignment layer, a linear polarizer, and a retardation layer. In particular, the optical structure can independently provide a special polarizer, a special diater, and a combination thereof, in terms of polarizance (ellipticality, spectral properties). Furthermore, the present invention relates to an antireflection device comprising such an optical structure. Furthermore, the present invention relates to a method for manufacturing such an optical structure. Accordingly, the antireflection device, the special polarizer, the special diater, and the combination thereof can be manufactured using the method of the present invention.

Anti-reflection devices are widely used, for example, in OLED (Organic Light Emitting Diode) displays. OLED displays are brighter than LCDs. Unfortunately, the reflection of ambient light off the metal anode layer of an OLED display reduces contrast and thus readability. To reduce light reflection, OLED displays are equipped with circular polarizers, which convert incident ambient light into circularly polarized light, which is then absorbed by the polarizer after reflection off the metal anode layer. Typically, a circular polarizer consists of a linear polarizer and a quarter-wave plate (QWP) as a retardation plate, where the slow axis of the quarter-wave plate is oriented at ±45 degrees relative to the absorption axis of the linear polarizer. Unpolarized ambient light is polarized by the linear polarizer; after passing through the QWP, the linearly polarized light is converted into circularly polarized light. The chirality of the circularly polarized light changes after reflection from the metal layer, so most of the reflected light no longer passes through the linear polarizer. Therefore, the circular polarizer used on top of the OLED device is used to address the contrast degradation caused by ambient light reflection.

However, a quarter-wave plate only converts linearly polarized light into circularly polarized light at a certain wavelength. For longer or shorter wavelengths, this relationship no longer applies, resulting in portions of light of different wavelengths being partially transmitted and not blocked.

Therefore, the goal is to reduce the wavelength dependence of the quarter-wave plate. A quarter-wave plate that exhibits no or reduced wavelength dependence is called an "achromatic wave plate" or "achromatic retardation plate."

To reduce the wavelength dependence of antireflective optical structures, several layers can be placed on top of each other. These layers are then aligned in one or more separate alignment steps that cancel or compensate for the wavelength effects, thereby reducing the wavelength dependence. However, in this case, a large number of alignment layers are required, each of which must be aligned in a separate alignment step.

WO 2016/016156 A1 describes a packaging structure for an OLED display incorporating anti-reflection properties.

US 10 962 696 B2 describes an OLED display panel coated with a layer providing anti-reflective properties.

US 2004/0109114 A1 describes a combination of a half-wave plate and a quarter-wave plate for making an achromatic retardation device for anti-reflection film.

US Pat. No. 6,717,644 B2 describes a stack of LCP layers having individual optical axis orientations. Each of these LCP layers is aligned by an alignment layer (e.g., a photoalignment layer). Therefore, the total number of layers in the stack is at least twice the number of LCP layers.

It is desirable to develop methods and structures that allow for reducing the number of layers required for stacking LCP layers so that the director in one LCP layer does not affect the director in an adjacent LCP layer. A director is defined as a direction parallel to the average orientation of the liquid crystal molecules. Solving this problem would reduce the complexity of manufacturing stacked LCP layers and, at the same time, lower production costs.

WO 2018/019691 A1 describes a method in which at least one LCP-containing layer is formed from a composition comprising a polymerizable liquid crystal and one or more photo-orientable substances. Any type of alignment treatment can be used to align the polymerizable liquid crystal material in a desired direction and/or configuration. Typically, the orientation of the polymerizable liquid crystal in the composition is altered by exposing the alignment layer to linearly polarized light. In contrast to these methods, the established orientation of the liquid crystal material is modified while avoiding exposure to polarized light. Thus, the alignment is produced at the surface of the upper layer by exposure to polarized light, which exposure results in an alignment direction that is different from the orientation of the liquid crystal director of the liquid crystal immediately below the upper surface of the layer.

The structure produced in this way can include an alignment layer above a substrate that aligns the liquid crystal material in a PLCPO layer (i.e., a layer made of PLCPO (polymerizable liquid crystal and photo-orientable) material). The PLCPO layer can function as a linear polarizer. The PLCPO layer can then provide alignment for a secondary material, such as a retarder layer, wherein the alignment direction provided by the PLCPO layer is different from the orientation of the liquid crystal in the PLCPO layer immediately below the upper surface. The polarization direction of the PLCPO layer can therefore be different from the orientation direction of the liquid crystal in the retarder layer. Although a separate alignment layer for the retarder is not necessary in this case, the alignment layer and the PLCPO layer must still be photo-aligned.

Therefore, it remains desirable to provide optical structures that can be produced with a reduced number of production steps and methods for producing such optical structures with a reduced number of production steps, in particular alignment steps.

Furthermore, US 9 298 041 B2 describes so-called multi-twisted retarders (MTRs), which comprise an arrangement of at least two generally nematic liquid crystal layers on a single substantially uniform alignment surface, wherein at least one of the layers has a nematic direction, i.e. a local optical axis, which is twisted along the thickness of the layer, and wherein the subsequent layer is directly aligned by the exposed surface of the preceding layer.

An object of the present invention is to provide an optical structure that defines at least two optical alignment directions—one for a retardation layer and one for a polarizer—and whose production is simplified. In particular, additional alignment steps beyond the alignment of the alignment layer should be avoided. Another object of the present invention is to provide a method for manufacturing such an optical structure and an antireflection device comprising such an optical structure.

This object is solved by an optical structure as defined in claim 1, an antireflection device as defined in claim 8 and a method as defined in claims 9 and 10.

The optical structure of the present invention includes a linear polarizer, a twisted liquid crystal retardation layer, or a stack of twisted liquid crystal retardation layers. The linear polarizer defines a polarization direction. The stack of twisted liquid crystal retardation layers has a first outer layer and a second outer layer, the second outer layer being located opposite the first outer layer. The twisted liquid crystal retardation layer or the first outer layer of the stack of twisted liquid crystal retardation layers is disposed at a polarization interface between the polarizer and the twisted liquid crystal retardation layer or the stack of twisted liquid crystal retardation layers. The first orientation direction of liquid crystal within the twisted liquid crystal retardation layer or the stack of twisted liquid crystal retardation layers immediately adjacent to the polarization interface is determined by the polarization direction of the polarizer. Furthermore, the optical structure includes an alignment layer and an alignment interface. The alignment layer defines an alignment direction. The alignment interface is an interface between the alignment layer and a layer adjacent to the alignment layer, wherein the adjacent layer is selected from the polarizing layer, the twisted liquid crystal retardation layer, and a second outer layer of a stack of twisted liquid crystal retardation layers. If the alignment interface is the interface between the alignment layer and the polarizing layer, the alignment direction of the alignment layer sets the polarization direction of the polarizing layer. If the alignment interface is the interface between the alignment layer and the twisted liquid crystal retardation layer or the second outer layer of the stack of twisted liquid crystal retardation layers, the alignment direction of the alignment layer sets the second orientation direction of the liquid crystal in the twisted liquid crystal retardation layer or the second outer layer of the stack of twisted liquid crystal retardation layers adjacent to the alignment interface.

The phrase "the orientation of one layer is set by the orientation of another layer" or "the orientation of one layer sets the orientation of another layer" means that the first orientation of the liquid crystal immediately adjacent to the polarizing interface within the twisted liquid crystal retarder layer or a stack of twisted liquid crystal retarder layers is set by the polarization direction of the polarizing layer, the alignment direction of the alignment layer sets the polarization direction of the polarizing layer, and the alignment direction of the alignment layer sets the second orientation of the liquid crystal immediately adjacent to the second outer layer of the twisted liquid crystal retarder layer or the stack of twisted liquid crystal retarder layers. This means that the orientation of one layer affects or is affected by the orientation of the other layer. Generally, there is a specific angle between the orientation of the one layer and the orientation of the other layer. This angle can be, for example, 90°, such that the orientation of one layer is perpendicular to the orientation of the other layer. Alternatively, it can be 0°, such that the orientation of one layer is parallel to the orientation of the other layer. In the latter case, the orientation of one layer is aligned with the orientation of the other layer, i.e., for example, the orientation of the alignment layer is aligned with the polarization direction of the polarizing layer, and the orientation of the alignment layer is aligned with the second orientation direction of the liquid crystal immediately adjacent to the twisted liquid crystal retardation layer or the second outer layer of the twisted liquid crystal retardation layer stack.

It should be understood that although the terms first, second, third, etc. may be used herein to describe various layers, orientations, and/or elements, such as a single body, these layers, orientations, and/or elements should not be limited by these terms. These terms are only used to distinguish one layer, orientation, and/or element from another layer, orientation, and/or element. Thus, a first layer, orientation, and/or element discussed herein could be termed a second layer, orientation, and/or element without departing from the teachings of the present invention. If an embodiment specifically specifies a second layer, orientation, and/or element, the first layer, orientation, and/or element may or may not be present.

In the case of linearly polarized light, the electromagnetic field oscillates in a plane that defines the plane of polarization. A linearly polarizing layer is a layer that polarizes incident light, at least in the visible wavelength range, such that the light leaving the layer is linearly polarized. The direction of polarization is the direction in which light leaving the polarizing layer is linearly polarized according to the plane of polarization.

The polarizing interface refers to the interface between the polarizing layer and another layer forming an interface with the polarizing layer. The other layer is particularly the twisted liquid crystal retardation layer or a stack of twisted liquid crystal retardation layers. The alignment interface refers to the interface between the alignment layer and another layer forming an interface with the alignment layer. In the optical structure of the present invention, the other layer is the polarizing layer, the twisted liquid crystal retardation layer, or an outer layer of the stack of twisted liquid crystal retardation layers.

The alignment of the liquid crystals in the polarising layer or the twisted liquid crystal retardation layer or in the outer layer of the stack of twisted liquid crystal retardation layers can be achieved by means of the alignment layer by any known method for aligning liquid crystals. For example, the alignment layer formed on the substrate forms an alignment surface, which should be understood to mean that the surface has the ability to align the liquid crystals. The alignment layer may provide the alignment without further treatment. For example, if a plastic substrate is used as a carrier, it may provide the alignment on the surface due to its manufacturing method, such as extruding or stretching the substrate. It is also possible to paint the carrier or to emboss a directional microstructure in order to produce the alignment capability. For example, the alignment layer may be rubbed polyimide.

Alternatively, a thin alignment layer of material can be applied to a carrier specifically designed for its alignment properties. This layer can be further painted or treated to impart a directional microstructure to the surface, for example by embossing. Alternatively, the thin alignment layer can comprise a photo-orientable substance. In this case, alignment can be induced by exposure to polarized light.

Compared to conventional liquid crystal alignment via brushed surfaces, photo-alignment technology offers numerous advantages, including high reproducibility, flexible alignment patterns, and suitability for roll-to-roll manufacturing. Furthermore, photo-alignment can be applied to curved surfaces, as the light aligning the photo-alignment layer can follow the surface modification. Conventional photo-alignment technology involves applying a thin layer of photo-alignable material onto a substrate, such as glass or plastic foil, to form the alignment layer.

Preferably, the alignment layer of the optical structure of the present invention is a photo-alignment layer. In particular, the initial orientation is determined by exposing the alignment layer to linearly polarized ultraviolet (LPUV) light. Alternatively, the initial orientation is determined by rubbing polyimide. However, any other alignment methods are possible.

In the context of the present invention, a "photo-alignment layer" is made of a material in which anisotropic properties can be induced after exposure to aligning light, as described, for example, in US 11 181 674 B2 (WO 2018/019691 A1). For this purpose, the photo-alignment layer comprises a photo-orientable substance. Furthermore, the term "photo-alignment layer" refers to a layer that has been aligned by exposure to aligning light. For the purposes of the present invention, the induced anisotropy must be such that it provides alignment capabilities for an adjacent layer comprising, for example, an anisotropic LCP compound. The term "alignment direction" shall refer to the preferred direction induced in the adjacent layer, for example, the alignment direction in which the LCP compound is aligned.

The photo-orientable material is incorporated into the photo-orientable portion, which is capable of developing a preferred direction upon exposure to aligning light and thus generating anisotropic properties. Such photo-orientable portions preferably have anisotropic absorption properties.

For example, the photoorientable moiety is a substituted or unsubstituted azo dye, anthraquinone, coumarin, merocyanidin, 2-phenylazothiazole, 2-phenylazobenzothiazole, stilbene, cyanostilbene, fluorostilbene, cinnamonitrile, chalcone, cinnamate, cyanocinnamate, stilbazolium, 1,4-bis(2-phenylvinyl)benzene, 4,4'-bis(arylazo)stilbene, perylene, 4,8-diamino-1,5-naphthoquinone dye, aryloxycarboxylic acid derivatives, aryl esters, N-arylamide, polyimines, diaryl ketones having a ketone moiety or ketone derivative bound to two aromatic rings, such as, for example, substituted benzophenones, benzophenoneimines, phenylhydrazones, and semicarbazones.

The preparation of the anisotropic absorbent materials listed above is well known, as shown, for example, by Hoffman et al., U.S. Patent No. 4,565,424, Jones et al., U.S. Patent No. 4,401,369, Cole, Jr. et al., U.S. Patent No. 4,122,027, Etzbach et al., U.S. Patent No. 4,667,020, and Shannon et al., U.S. Patent No. 5,389,285.

Preferably, the photoorientable moieties comprise arylazo, poly(arylazo), stilbene, cyanostilbene, cinnamate, or chalcone.

Photo-orientable materials can be monomers, oligomers, or polymers. For example, the photo-orientable moieties can be covalently bonded within the main chain or side chains of a polymer or oligomer, or they can be monomers or other non-polymerizable compounds. Photo-orientable materials can further be copolymers containing different types of photo-orientable moieties, or they can be copolymers containing side chains with and without photo-orientable moieties.

The polymer includes, for example, polyacrylates, polymethacrylates, polyimines, polyurethanes, polyamides, polymaleimides, poly-2-chloroacrylates, poly-2-phenylacrylates; unsubstituted or C1- _{C6 alkyl} -substituted polyacrylamide, polymethacrylamide, poly-2-chloroacrylamide, poly-2-phenylacrylamide, polyethers, polyvinyl ethers, polyesters, polyvinyl esters, polystyrene derivatives, polysiloxanes, linear or branched alkyl esters of polyacrylic acid or polymethacrylic acid; polyphenoxyalkyl acrylates, polyphenoxyalkyl methacrylates, polyphenylalkyl methacrylates having an alkyl residue of 1 to 20 carbon atoms; polyacrylonitrile, polymethacrylonitrile, cycloolefin polymers, polystyrene, poly-4-methylstyrene, or mixtures thereof.

Preferably, the twisted liquid crystal retardation layer of the optical structure of the present invention or the twisted liquid crystal retardation layer of a stack of twisted liquid crystal retardation layers is made of an oriented LCP layer, which has been made from an LCP material, which LCP material contains chiral dopants, which chiral dopants adopt a twisted configuration so as to form the twisted liquid crystal retardation layer.

For information regarding polymerizable chiral dopants and liquid crystal cholesterol mixtures containing them, please refer to US Patent No. 6,120,859, particularly Example 4. In this embodiment, the dopants induce a helical structure in the liquid crystal layer. In the uniformly oriented state (Grandjean texture) of such a layer, light within a specific wavelength range (selective reflection range) is separated into its left-circularly polarized component and its right-circularly polarized component. Depending on the direction of rotation of the cholesterol helical structure, one of the circularly polarized components is completely reflected, while the other is transmitted unaffected. Light outside the selective reflection range is transmitted unaffected. The position of the reflection band in the optical spectrum is determined by the pitch of the cholesterol helix, and the width of the band is related to the material's double refraction (birefringence). Layers with these optical properties are ideal media for a wide range of applications, including color filters, optical bandpass filters, and polarizers.

In particular, the chiral doping of the twisted liquid crystal retardation layer includes one or more chiral additives. The chiral additives cause a twist in the liquid crystal. In an aligned layer containing chiral additives, a left-handed or right-handed twist deformation can be induced, where the twist angle depends on the type and concentration of the chiral additive and the layer thickness. For example, if a 90° twist is developed in such a layer, the liquid crystal immediately below the top surface of the layer will be aligned at 90° relative to the liquid crystal at the bottom of the layer.

For non-twisted liquid crystal retardation layers, the orientation direction of the liquid crystal molecules does not change along the thickness direction of the layer. However, for twisted liquid crystal retardation layers, such as cholesterol liquid crystal retardation layers, the orientation direction changes along the thickness direction. With respect to the position of the liquid crystal in a layer, the phrase "immediately adjacent to the interface within the layer" shall refer to the liquid crystal molecules closest to the interface with another layer. Accordingly, "the orientation direction of the liquid crystal at a certain position "immediately adjacent to the interface within the layer" shall refer to the average orientation of the liquid crystal molecules closest to the interface at the said position. For a layer containing only liquid crystal molecules, the liquid crystal molecules of the layer closest to the interface are directly at the interface.

In a preferred embodiment of the present invention, the polarizing layer is a coatable layer. In particular, the polarizing layer may comprise a liquid crystal polymer material and at least a dichroic dye and/or at least a fluorescent dye. Preferably, a coatable polarizer is used for the polarizing layer. The coatable polarizing layer typically comprises anisotropically absorbing molecules, such as carbon nanotubes or a dichroic dye, dispersed or dissolved in a host material. For example, a polarizer that can be used as a polarizing layer is described in US Patent No. 10,385,215.

In a preferred embodiment of the present invention, the twisted liquid crystal retardation layer or the outer layer of the stack of twisted liquid crystal retardation layers is a coatable layer. It is a formulation containing a solvent mixture and a solid content characterized by at least one LCP material, a photoinitiator and possibly other additives.

In a preferred embodiment of the present invention, the twisted liquid crystal retardation layer, or the stack of twisted liquid crystal retardation layers, is made of a twisted reverse-dispersion material. Reverse wavelength dispersion means that the retardation value decreases at shorter wavelengths. This type of material typically exhibits a low wavelength dependence of the retardation and is therefore more achromatic. With respect to antireflection properties, a single such layer yields similar results to two layers of conventional materials.

In a preferred embodiment of the present invention, the optical structure comprises a stack of twisted liquid crystal retardation layers, wherein at least one retardation interface is formed between two adjacent twisted liquid crystal retardation layers in the stack. Generally, a retardation interface refers to an interface between two different twisted liquid crystal retardation layers.

To better compensate for the wavelength dependence of the retarder, a retarder in which the liquid crystal molecules are continuously twisted along a perpendicular axis ("twisted retarder") is used. According to embodiments of the present invention, two or more twisted liquid crystal retardation layers are stacked to even better compensate for the wavelength dependence. This structure is also referred to as an "achromatic multi-twisted retarder."

In a preferred embodiment of the present invention, at the retardation interface between one of the twisted liquid crystal retardation layers and the other of the twisted liquid crystal retardation layers, the orientation direction of the liquid crystal immediately adjacent to the retardation interface in one of the twisted liquid crystal retardation layers is aligned with the orientation direction of the liquid crystal immediately adjacent to the retardation interface in the other of the twisted liquid crystal retardation layers. Accordingly, the optical structure of this embodiment includes at least two birefringent layers, namely twisted liquid crystal retardation layers, and in particular, a stack of twisted liquid crystal retardation layers. The structure can include an arrangement of at least two generally nematic liquid crystal layers, wherein one of the layers has a nematic director (i.e., a local optical axis) that is twisted along the thickness of the layer, and wherein the subsequent layer is directly aligned by the exposed surface of the preceding layer (i.e., at the retarder interface). Thus, an achromatic multi-twist retarder (MTR) can be provided. Advantageously, a separate alignment step is not required to produce such an optical structure, as the liquid crystal director of one retarder layer aligns the liquid crystal director of the other retarder layer at the retarder interface.

In a preferred embodiment of the present invention, the third orientation direction of the liquid crystal immediately adjacent to the delay interface in one of the two adjacent twisted liquid crystal retardation layers is aligned with the fourth orientation direction of the liquid crystal immediately adjacent to the delay interface in the other of the two adjacent twisted liquid crystal retardation layers.

In a preferred embodiment of the present invention, the helical pitch of one twisted liquid crystal retarder layer in the stack of twisted liquid crystal retarder layers differs from the helical pitch of another twisted liquid crystal retarder layer in the stack of twisted liquid crystal retarder layers. Advantageously, this further improves achromatic properties. As used herein, the term "helical pitch" (helix pitch, spiral pitch) shall refer to the distance over which the liquid crystal orientation direction rotates a full 360 degrees.

In a preferred embodiment of the present invention, the twisted liquid crystal retardation layer, or at least one twisted liquid crystal retardation layer in a stack of twisted liquid crystal retardation layers, is a high-twist retardation plate. Accordingly, the twisted liquid crystal retardation layer, or at least one twisted liquid crystal retardation layer in a stack of twisted liquid crystal retardation layers, does not function as a waveguide because the twist angle does not satisfy the Maugin condition (waveguide mode confinement): Where φ is the twist angle, λ is the wavelength, Δn is the birefringence, and d is the thickness. If we invert this equation, we can say that the pitch of the high-twist retarder cannot exceed a critical value: .

In particular, the helical pitch of the twisted liquid crystal retarder layer is less than 11 μm, in particular less than 8 μm and preferably less than 5 μm, for example to cover the entire visible range. For antireflective coatings, the angle between the orientation of the retarder and the orientation of the polarizer is important. If these orientations are parallel, the antireflective coating will be ineffective. At the interface between the retarder and the polarizer, the orientations are set by the layers, for example if the retarder is aligned with the polarizer, the orientations are parallel. The orientation of the twisted retarder then changes in a direction perpendicular to the interface. Therefore, the pitch and thickness of the twisted retarder or the pitch and thickness of the stack of twisted retarder or the twist angle between the opposite side surfaces of one or more retarder of the stack of twisted retarder are important. So-called low-twist retarders show similar effects to waveguides. According to the present invention, it is preferred to use at least one high-twist retarder, which provides better efficacy, especially for anti-reflection coatings.

In a preferred embodiment of the present invention, the pitch of the twisted liquid crystal retarder layer or the pitch of the stacked twisted liquid crystal retarder layers is configured to provide an optical structure with achromatic antireflection properties. In particular, the pitch of the twisted liquid crystal retarder layer(s) can be configured to provide an achromatic quarter-wave retarder.

In a preferred embodiment of the present invention, the alignment interface is the interface between the alignment layer and the twisted liquid crystal retarder layer or the second outer layer of the stack of twisted liquid crystal retarder layers. Furthermore, the polarization interface is disposed between the polarization layer and the twisted liquid crystal retarder layer or the stack of twisted liquid crystal retarder layers. The optical structure of this further embodiment includes an additional twisted liquid crystal retarder layer or a stack of additional twisted liquid crystal retarder layers, wherein the stack of additional twisted liquid crystal retarder layers has an additional first outer layer and an additional second outer layer, the additional second outer layer is on the opposite side of the additional first outer layer, and the first outer layer of the additional twisted liquid crystal retarder layer or the stack of additional twisted liquid crystal retarder layers is arranged at an additional polarization interface between the polarizing layer and the additional twisted liquid crystal retarder layer or the stack of additional twisted liquid crystal retarder layers. The first orientation direction of the liquid crystal in the further twisted liquid crystal retarder layer or the stack of further twisted liquid crystal retarder layers immediately adjacent to the further polarizing interface is set by the polarization direction of the polarizing layer. Preferably, the optical structure of this embodiment can provide a special dichroic attenuator.

According to the present invention, the optical structure can include a retardation layer or a stack of retardation layers above a polarizing layer, and, conversely, one or more polarizing layers above the retardation layer or the stack of retardation layers. According to the present invention, this structure can be extended to a structure consisting of one or more polarizing layers, with the polarizing layer(s) between the retardation layers or between the stack of retardation layers, to make it not only a special polarizer but also a special dichroic attenuator. The manufacturing process can begin with the application of an alignment layer, followed by a retarder layer or a stack of retarder layers, followed by one or more polarizing layers, and then again further retarder layers or stacks of further retarder layers. This allows the production of not only circular polarizers but also any specific polarizer with regard to polarization degree (ellipticality, spectral properties, etc.), any specific dichroic attenuator, and combinations of the two, independently of one another.

The present invention is based on the concept that it is possible to align a coatable polarizer and an LCP retarder layer, for example, by aligning the coatable polarizer on an LCP retarder layer, in which case the absorption direction is determined by the slow axis of the retarder. Alternatively, an upside-down arrangement is possible, aligning the LCP retarder layer and the coatable polarizer. However, circular polarization cannot be achieved with a simple straight retarder configuration because the absorption axis of the polarizer and the slow axis of the retarder would be identical. According to the present invention, at least one twisted liquid crystal retarder layer is used. It is also possible to stack several twisted liquid crystal retardation layers in a stack, so that the liquid crystal directors on the outer layers of the stack are aligned with those on the adjacent layers at the interface. The initial orientation of the optical structure is determined by the alignment layer. In general, the optical structure of the present invention provides a special polarizer, a special dichroic attenuator, or a combination of the two.

An advantage of this architecture of the optical structure of the present invention is that the number of layers is reduced, as only one alignment layer or surface is required. Furthermore, the number of alignment steps required to provide alignment, such as UV exposure and/or stretching steps, is also reduced. Compared to current standard optical stack structures, the performance of the device is maintained, if not improved.

According to the present invention, no alignment layer is used at the interface between the linear polarizing layer and the twisted liquid crystal retarder layer or the outer layer of the stack of twisted liquid crystal retarder layers. Similarly, no alignment layer can be used between different twisted liquid crystal retarder layers of the stack. The omission of such an alignment layer, which is usually used to have different orientations between adjacent layers, results in a continuous change of the liquid crystal orientation at the respective interfaces. The thickness and pitch of the one or more twisted liquid crystal retarders are usually optimized to achieve a certain optical effect; for example, the conversion of linearly polarized light into elliptical or circularly polarized light. By omitting an additional alignment layer at the polarizer or retarder interface, another limitation is introduced, which must be taken into account during optimization. For example, at the polarization interface, the linear polarizer sets the orientation of the twisted liquid crystal retarder. Therefore, at this interface, the orientation of the polarizer or the twisted liquid crystal retarder cannot be freely selected. According to the present invention, compared to optical structures in which a separate alignment layer is used to select the orientation of the polarizer or the retarder at the interface, different optimizations with this limitation achieve essentially the same optical effect. However, the manufacturing method is simplified because no additional alignment layer needs to be inserted at the polarization interface or the retarder interface. In addition, no additional alignment steps, such as exposure to UV light, are required.

Thus, the optical structure of the present invention can be adapted to provide a variety of optical effects to light passing through the linear polarizer and the twisted liquid crystal retarder, or a stack of twisted liquid crystal retarder layers. For example, elliptical or circular polarizers or specialized dichroic attenuators can be provided, wherein the polarized light produced can be tailored to the specific application for which the optical structure is intended.

The anti-reflection device of the present invention comprises the optical structure described above, wherein the pitch of the twisted liquid crystal retardation layer or the pitch of the stacked twisted liquid crystal retardation layers is set to form an achromatic quarter-wave retardation plate.

Because the anti-reflection device includes the optical structure described above, it has the same advantages as the optical structure described above. In particular, the method of manufacturing such an anti-reflection device is simplified. Furthermore, advantageously, the device can be designed to provide improved achromatic properties by selecting a specific pitch and/or thickness of the twisted liquid crystal retardation layer or the pitch and/or thickness of the stack of twisted liquid crystal retardation layers.

The present invention is also directed to a dichroic attenuator comprising the optical structure described above, wherein the optical properties of the dichroic attenuator can be set by the pitch of the twisted liquid crystal retarder layer or the pitch of the stacked twisted liquid crystal retarder layers.

The method for manufacturing an optical structure according to the first aspect of the present invention comprises the following steps: (a)    forming an alignment layer, the alignment layer defining an alignment direction on a substrate, (b1) forming a linear polarizing layer, the linear polarizing layer defining a polarization direction on the alignment layer, and forming an alignment interface by setting the polarization direction of the polarizing layer through the alignment direction of the alignment layer, (c1) A twisted liquid crystal retardation layer or a stack of twisted liquid crystal retardation layers is formed, wherein the stack of twisted liquid crystal retardation layers has a first outer layer and a second outer layer, the second outer layer being located opposite the first outer layer. The twisted liquid crystal retardation layer or the first outer layer of the stack of twisted liquid crystal retardation layers is disposed on the polarizing layer to form a polarizing interface, wherein a first orientation direction of liquid crystal within the twisted liquid crystal retardation layer or the first outer layer of the stack of twisted liquid crystal retardation layers immediately adjacent to the polarizing interface is determined by the polarization direction of the polarizing layer.

This method can be used to fabricate the aforementioned optical structure. Advantageously, only a single alignment layer is required. Alignment of the liquid crystal orientation of the twisted liquid crystal retardation layer at the polarizing interface with the polarization direction of the polarizing layer is performed without the presence of a separate alignment layer. Therefore, the alignment step of the liquid crystal in the alignment layer or the first outer layer of the twisted liquid crystal retardation layer stack can be omitted.

The method for manufacturing an optical structure according to the second aspect of the present invention comprises the following steps: (a) forming an alignment layer, the alignment layer defining an alignment direction; (b2) forming a twisted liquid crystal retardation layer or a stack of twisted liquid crystal retardation layers, the stack of twisted liquid crystal retardation layers having a first outer layer and a second outer layer, the second outer layer being on an opposite side of the first outer layer, the twisted liquid crystal retardation layer or the second outer layer of the stack of twisted liquid crystal retardation layers being disposed on the alignment layer to form an alignment interface, wherein a second orientation direction of liquid crystal in the twisted liquid crystal retardation layer or the second outer layer of the stack of twisted liquid crystal retardation layers immediately adjacent to the alignment interface is set by the alignment direction of the alignment layer; (c2) forming a linear polarizing layer, wherein the linear polarizing layer defines a polarization direction on the twisted liquid crystal retardation layer or the first outer layer of the stack of twisted liquid crystal retardation layers, thereby forming a polarization interface, wherein the polarization direction of the polarizing layer is set by the first orientation direction of the liquid crystal in the twisted liquid crystal retardation layer or the first outer layer of the stack of twisted liquid crystal retardation layers immediately adjacent to the polarization interface.

This method can also be used to fabricate the optical structure described above. The method of the second aspect of the present invention differs from the method of the first aspect in that the alignment layer is configured, specifically, the orientation of the liquid crystal immediately adjacent to the alignment interface within the twisted liquid crystal retardation layer or the outer layer of the twisted liquid crystal retardation layer stack, rather than the polarization direction of the polarizing layer. However, the method of the second aspect of the present invention offers the same advantages as the method of the first aspect.

The alignment layer defining the alignment direction may be formed on a substrate.

In a preferred embodiment of the present invention, in the method according to the first or second aspect of the present invention, step (a) further comprises: providing a solution of a photopolymer, coating the photopolymer on a substrate, and exposing the photopolymer to polarized light to align the photopolymer.

In a preferred embodiment of the present invention, in the method according to the second aspect of the present invention, step (b2) further comprises: Coating a second component on the alignment layer to form the alignment interface, the second component comprising a second liquid crystal monomer and a second chiral dopant, the second component containing a polymerizable liquid crystal; Annealing the second component, whereby the second alignment direction of the liquid crystal within the second component coating adjacent to the alignment interface is set by the alignment direction of the alignment layer; Inducing polymerization of the polymerizable liquid crystal in the second component by exposure to UV light, thereby forming the twisted liquid crystal retardation layer or a second outer layer of a stack of twisted liquid crystal retardation layers at the alignment interface.

In a preferred embodiment of the present invention, the method according to the second aspect of the present invention further comprises: Coating a first component on the polymerized second component, the first component comprising a first liquid crystal monomer and a first chiral dopant, the first component containing a polymerizable liquid crystal; Annealing the first component so that a third orientation of the liquid crystals in the first component coating immediately adjacent to the interface between the polymerized second component and the first component coating is aligned with a fourth orientation of the liquid crystals in the polymerized second component immediately adjacent to the interface between the polymerized second component and the first component coating; Inducing polymerization of the polymerizable liquid crystals in the first component by exposure to UV light, thereby forming an additional layer of the stack of twisted liquid crystal retardation layers.

Representative second and/or first compositions comprising second and/or first liquid crystal monomers and second and/or first chiral dopants are described in US Pat. No. 6,120,859, particularly in Example 4.

In particular, the further layer of the stack of twisted liquid crystal retarder layers is a first outer layer of the stack of twisted liquid crystal retarder layers.

In a preferred embodiment of the present invention, the method according to the second aspect of the present invention further comprises: Coating a polarizing solution containing polymerizable liquid crystals on the twisted liquid crystal retardation layer or the stack of twisted liquid crystal retardation layers to form the polarizing interface; Annealing the polarizing solution, whereby the polarization direction of the polarizing solution is set by the first alignment direction of the liquid crystals in the first outer layer of the twisted liquid crystal retardation layer or the stack of twisted liquid crystal retardation layers immediately adjacent to the polarizing interface; Inducing polymerization of the polymerizable liquid crystals in the polarizing solution by exposure to UV light, thereby forming the polarizing layer.

In an embodiment of the present invention, the method according to the second aspect of the present invention further comprises: Coating an additional polarizing solution on the polymerized polarizing solution, the additional polarizing solution containing a polymerizable liquid crystal; Annealing the additional polarizing solution so that the polarization direction of the additional polarizing solution is aligned with the polarization direction of the polymerized polarizing solution at the interface between the polymerized polarizing solution and the additional polarizing solution; Inducing polymerization of the polymerizable liquid crystal in the additional polarizing solution by exposure to UV light, thereby forming a stack of polarizing layers having parallel polarization directions. In particular, if thickness requirements that may not be achievable with a single coating step are required, the additional layer of the coatable polarizer can be provided.

In a preferred embodiment of the present invention, the method according to the second aspect of the present invention further comprises: forming an additional twisted liquid crystal retardation layer or a stack of additional twisted liquid crystal retardation layers, the stack of additional twisted liquid crystal retardation layers having an additional first outer layer and an additional second outer layer, the additional second outer layer being located opposite the additional first outer layer, the additional twisted liquid crystal retardation layer or the additional second outer layer of the stack of additional twisted liquid crystal retardation layers being disposed on the polarizing layer to form an additional polarizing interface, wherein a first orientation direction of liquid crystal within the additional twisted liquid crystal retardation layer or the additional second outer layer of the stack of additional twisted liquid crystal retardation layers immediately adjacent to the additional polarizing interface is determined by the polarization direction of the polarizing layer. Preferably, the method of this embodiment can provide a special two-way attenuator.

The embodiments of the present invention will now be described with reference to the accompanying drawings.

The first embodiment of the optical structure 1 of the present invention is described with reference to FIG1 :

The optical structure 1 comprises a glass substrate 2 which is 1.1 mm thick and known per se.

The glass substrate 2 is coated with an alignment layer 3 having a thickness of approximately 100 nm. The alignment layer 3 is exposed to linearly polarized ultraviolet (LPUV) light and provides alignment direction for subsequent layers.

The alignment layer 3 defines an alignment interface 7 for the other layer to be aligned. Furthermore, the alignment layer 3 defines the alignment direction for the liquid crystals in the layer adjacent to the alignment layer 3. The alignment layer 3 itself is known. Instead of a photoalignment layer, a rubbed polyimide can also be used as the alignment layer.

In the optical structure 1 of the first embodiment, the twisted liquid crystal retardation layer 4 is disposed at the alignment interface 7. Therefore, in the first embodiment of the optical structure 1, the alignment interface 7 is the interface between the alignment layer 3 (on one side) and the twisted liquid crystal retardation layer 4 (on the other side). In this case, the alignment direction of the alignment layer 3 sets the orientation direction of the liquid crystal within the liquid crystal retardation layer 4 immediately adjacent to the alignment interface 7. In this embodiment, the alignment direction of the alignment layer 3 is aligned with the orientation direction of the liquid crystal within the liquid crystal retardation layer 4 immediately adjacent to the alignment interface 7 because the alignment direction is parallel to the alignment direction. This alignment direction is also designated as the second alignment direction.

The twisted liquid crystal retardation layer 4 is a coatable layer made of a twisted reverse dispersion material. The thickness of the twisted liquid crystal retardation layer 4 is 3.50 μm, and its helical pitch is 20.0 μm.

A linear polarizing layer 6 is disposed on the opposite interface of the twisted liquid crystal retardation layer 4. Therefore, the interface between the twisted liquid crystal retardation layer 4 and the polarizing layer 6 is referred to as a polarizing interface 8. The orientation of the liquid crystal within the twisted liquid crystal retardation layer 4 immediately adjacent to the polarizing interface 8 determines the polarization direction of the polarizing layer 6. In the present embodiment, the orientation of the liquid crystal within the twisted liquid crystal retardation layer 4 immediately adjacent to the polarizing interface 8 aligns with the polarization direction of the polarizing layer 6. This orientation of the liquid crystal within the twisted liquid crystal retardation layer 4 is also referred to as a first orientation direction.

The polarizing layer 6 is a coatable layer and contains dichroic dyes dispersed in a host material.

The parameters of the twisted liquid crystal retardation layer 4, particularly its thickness and helical pitch, are configured to provide an achromatic quarter-wave plate. Together with the linear polarizing layer 6, the optical structure 1 of the first embodiment provides an antireflection device. Incident light passing from the linear polarizing layer 6 to the substrate 2, through the optical structure 1, and then reflected by a material with a higher reflectivity is absorbed and essentially does not pass through the linear polarizing layer 6 in the opposite direction over a wide wavelength range.

The second embodiment of the optical structure 1 of the present invention is described with reference to FIG2 :

In the optical structure 1 of the second embodiment, its substrate 2, alignment layer 3, and alignment interface 7 are identical to those of the corresponding optical structure 1 of the first embodiment. In the optical structure 1 of the second embodiment, the linear polarizing layer 6 is disposed at the alignment interface 7. Therefore, the alignment interface 7 is the interface between the alignment layer 3 (on one side) and the polarizing layer 6 (on the other side). Therefore, the alignment direction of the alignment layer 3 determines the polarization direction of the polarizing layer 6. In this embodiment, the alignment direction of the alignment layer 3 is aligned with the polarization direction of the polarizing layer 6.

On the opposite side of the polarizing layer 6, that is, at the polarizing interface 8, the twisted liquid crystal retardation layer 4 is arranged. Accordingly, the first orientation direction of the liquid crystal in the twisted liquid crystal retardation layer 4 immediately adjacent to the polarizing interface 8 is set by the polarization direction of the polarizing layer 6. In the case of this embodiment, the first orientation direction of the liquid crystal in the twisted liquid crystal retardation layer 4 immediately adjacent to the polarizing interface 8 is aligned with the polarization direction of the polarizing layer 6. The orientation direction of the liquid crystal in the twisted liquid crystal retardation layer 4 is then rotated in the direction of the thickness of the twisted liquid crystal retardation layer 4. The composition, helical pitch, and thickness of the twisted liquid crystal retardation layer 4 of the optical structure of the second embodiment are the same as those of the twisted liquid crystal retardation layer 4 of the optical structure 1 of the first embodiment described above.

The optical structure 1 of the second embodiment thus corresponds substantially to the optical structure 1 of the first embodiment. However, in the case of the optical structure 1 of the second embodiment, the alignment layer 3 aligns the linear polarizing layer 6 instead of the twisted liquid crystal retardation layer 4.

The third embodiment of the optical structure 1 of the present invention is described with reference to Figures 3 to 5:

As in the first and second embodiments, the optical structure 1 of the third embodiment comprises a glass substrate 2, which is 1.1 mm thick and known per se, coated with an alignment layer 3 having a thickness of approximately 100 nm. This alignment layer 3 corresponds to the alignment layer 3 of the first and second embodiments.

In the optical structure 1 of the third embodiment, a stack of twisted liquid crystal retarder layers 10 is disposed at the alignment interface 7. The stack 10 includes a plurality of twisted liquid crystal retarder layers, which form at least a first outer layer 10-1 and a second outer layer 10-2, with the second outer layer 10-2 located opposite the first outer layer 10-1. In the third embodiment, the stack 10 includes two twisted liquid crystal retarder layers, namely the first outer layer 10-1 and the second outer layer 10-2, as shown in FIG3 . In the third embodiment of the optical structure 1, the alignment interface 7 is the interface between the alignment layer 3 (on one side) and the second outer layer 10-2 of the stack 10 (on the other side). In this case, the alignment direction of the alignment layer 3 sets the second orientation direction of the liquid crystal in the second outer layer 10-2 of the stack 10 adjacent to the alignment interface 7. In this embodiment, the alignment direction of the alignment layer 3 is aligned with the second orientation direction of the liquid crystal in the second outer layer 10-2 of the stack 10 adjacent to the alignment interface 7.

The second outer layer 10-2 of the stack 10 of twisted liquid crystal retarder layers is a coatable layer made of a twisted reverse dispersion material. The thickness of this outer layer 10-2 of the stack 10 is 1.05 μm. Its helical pitch is 8 μm. The twist angle of this second outer layer 10-2 in the direction of thickness _d1 is 78.2°. This twist angle is the difference between the liquid crystal orientation direction _Φ1 at the alignment interface 7 and the liquid crystal orientation direction _Φ1 at the retarder interface 9. Therefore, the second outer layer 10-2 of the stack 10 is a high-twist retarder. As can be seen in Figure 4, the pointing angle Φ1 of the second outer layer 10-2 of the stack 10 is changed in a twisted manner from the alignment direction given by the alignment layer 3 to another angle Φ1 at the opposite interface (i.e., the delayed interface 9) provided by the second outer layer 10-2 of the stack 10, as described below and as shown in Figure 1.

At the retardation interface 9, the first outer layer 10-1 of the stack 10 is arranged adjacent to the second outer layer 10-2 of the stack 10. Therefore, the retardation interface 9 is the interface between two different twisted liquid crystal retardation layers.

As can be seen in FIG4 , the fourth orientation direction of the liquid crystal in the second outer layer 10 - 2 of the stack 10 immediately adjacent to the delay interface 9 is aligned with the third orientation direction of the liquid crystal in the first outer layer 10 - 1 of the stack 10 immediately adjacent to the delay interface 9. Therefore, at the delay interface 9, the second outer layer 10 - 2 of the stack 10 is directly aligned with the first outer layer 10 - 1 of the stack 10 at the delay interface 9.

As can be seen in Figure 4, the third orientation direction of the first outer layer 10-1 of the stack 10 rotates along with the thickness of the first outer layer 10-1 of the stack 10 so that based on the thickness _d2 of the first outer layer 10-1 of the stack 10, the orientation direction _Φ2 at the delayed interface 9 is different from the orientation direction _Φ2 on the opposite side interface of the first outer layer 10-1 of the stack 10.

The thickness _d2 of the first outer layer 10-1 of the stack 10 is 2.12 μm. The helical pitch of the first outer layer 10-1 of the stack 10 is 38 μm. The twist angle in the thickness direction of the first outer layer 10-1 is 20.1°. The twist angle is the difference between the liquid crystal alignment direction _Φ2 at the retardation interface 9 and the liquid crystal alignment direction _Φ2 at the polarization interface 8.

A linear polarizing layer 6 is disposed on the interface opposite the first outer layer 10-1 of the stack 10. Thus, the interface between the first outer layer 10-1 of the stack 10 and the polarizing layer 6 is a polarizing interface 8. The first orientation direction of the liquid crystal within the first outer layer 10-1 of the stack 10, immediately adjacent to the polarizing interface 8, sets the polarization direction of the polarizing layer 6. In the present embodiment, the first orientation direction of the liquid crystal within the first outer layer 10-1 of the stack 10, immediately adjacent to the polarizing interface 8, aligns with the polarization direction of the polarizing layer 6, as can be seen in FIG. 4 .

The polarizing layer 6 corresponds to the polarizing layer 6 of the first embodiment shown in FIG. 1 .

The parameters, particularly the thicknesses _d1 and _d2 and the helical pitch of the first and second outer layers 10-1 and 10-2 of the stack 10, are configured to provide an achromatic quarter-wave plate. Together with the linear polarizer layer 6, the optical structure 1 of the third embodiment provides an antireflection device. Incident light passing through the optical structure 1 from the linear polarizer layer 6 to the substrate 2 and then reflecting off a material with a higher reflectivity is absorbed and essentially does not pass through the linear polarizer layer 6 in the opposite direction over a wide wavelength range.

Figure 5 shows the results of the cone-beam method, which uses an air gap between the mirror and the device at an angle of incidence from 30° to 50°. The color rendering is close to natural gray, and the anti-reflection effect is confirmed. However, the air gap reduces this effect.

6 to 8 , a fourth embodiment of the optical structure 1 is described.

In the optical structure 1 of the fourth embodiment, its substrate 2, alignment layer 3, and alignment interface 7 are identical to those of the corresponding optical structure 1 of the third embodiment. In the optical structure 1 of the fourth embodiment, the linear polarizing layer 6 is disposed at the alignment interface 7. Therefore, the alignment interface 7 is the interface between the alignment layer 3 (on one side) and the polarizing layer 6 (on the other side). Therefore, the alignment direction of the alignment layer 3 determines the polarization direction of the polarizing layer 6. In this embodiment, the alignment direction of the alignment layer 3 is aligned with the polarization direction of the polarizing layer 6.

On the opposite side of the polarizing layer 6, i.e., at the polarizing interface 8, the stack 10 of twisted liquid crystal retardation layers is arranged. Accordingly, the first orientation direction of the liquid crystal within the first outer layer 10-1 of the stack 10, immediately adjacent to the polarizing interface 8, is set by the polarizing direction of the polarizing layer 6, specifically aligned with the polarizing direction of the polarizing layer 6. The orientation direction of the liquid crystal in the first outer layer 10-1 of the stack 10 is then rotated in the direction of the thickness of the first outer layer 10-1 of the stack 10, as shown in FIG. 7 . The composition, helical pitch, and thickness of the first outer layer 10 - 1 of the stack 10 of the optical structure 1 of the fourth embodiment are the same as those of the first outer layer 10 - 1 of the stack 10 of the optical structure 1 of the third embodiment described above.

Similar to the optical structure 1 of the third embodiment, the optical structure 1 of the fourth embodiment also includes a second outer layer 10-2 of the stack 10 at the delay interface 9 between the first and second outer layers 10-1, 10-2 of the stack 10. The composition, helical pitch, and thickness of the second outer layer 10-2 of the stack 10 correspond to the second outer layer 10-2 of the stack 10 of the optical structure 1 of the third embodiment described above.

The optical structure 1 of the fourth embodiment thus corresponds substantially to the optical structure 1 of the third embodiment. However, in the case of the optical structure 1 of the fourth embodiment, the alignment layer 3 is aligned to the linear polarizing layer 6 rather than to the outer layer of the stack 10 of twisted liquid crystal retardation layers.

In all embodiments, only a single alignment layer 3 is required to provide the optical structure 1. Furthermore, only a single alignment step needs to be performed for the alignment layer. Further alignment is provided directly by the layers provided at the interfaces between the layers.

8 depicts a diagram showing the delay in terms of wavelength and the wavelength-dependent optical axis of the optical structure 1 of the fourth embodiment. It can be seen that the delay is substantially independent of wavelength in the range between 400 nm and 700 nm, so that an achromatic retarder is provided by the optical structure 1.

Figures 9A and 9B depict reflection cone diagrams, derived from simulations, for intensity (Figure 9A) and color ΔE (Figure 9B) at up to 50° oblique incidence for a known optical structure. In this structure, the same linear polarizer 6 as in the third and fourth embodiments of optical structure 1 is used. In addition, a linear reverse-dispersion retarder is used, with the liquid crystal orientation angled at 45° relative to the polarization direction of the polarizer.

For comparison, Figures 10A and 10B show corresponding reflection cone diagrams, which are derived from simulations, for a combination of two twisted standard dispersion retarders using the same polarizer aligned with a top director layer corresponding to the alignment layer 3 of the optical structure 1 of the third embodiment.

In addition, Figures 11A and 11B show corresponding reflection cone plots, which are derived from simulations using a reduced number of layers. A single twisted reverse-dispersive retarder was used, with a polarizer aligned at its top angle. Again, the single twisted reverse-dispersive retarder was aligned by an alignment layer, corresponding to alignment layer 3 of optical structure 1 in the first or third embodiment. It can be seen that the performance of the different designs is very similar.

The fifth embodiment of the optical structure 1 is described with reference to FIG12 :

In the optical structure 1 of the fifth embodiment, the substrate 2, the alignment layer 3, the alignment interface 7, the twisted liquid crystal retardation layer 4, the polarization interface 8 and the linear polarization layer 6 are the same as those of the corresponding optical structure 1 of the first embodiment.

Furthermore, the optical structure 1 of the fifth embodiment includes an additional twisted liquid crystal retardation layer 11. The additional twisted liquid crystal retardation layer 11 is disposed at an additional polarization interface 12 between the polarizing layer 6 and the additional twisted liquid crystal retardation layer 11. Again, the first alignment direction of the liquid crystal within the additional twisted liquid crystal retardation layer 11 adjacent to the additional polarization interface 12 is set by the polarization direction of the polarizing layer 6, for example, aligned with the polarization direction of the polarizing layer 6.

The optical structure 1 of the fifth embodiment provides a special bidirectional attenuator.

The first embodiment of the method of the present invention is described below. The optical structure 1 of the third embodiment shown in FIG3 can be manufactured by the first embodiment of the method.

A photopolymer solution is spin-coated onto a glass substrate 2 and then dried on a hot plate at 180°C for 10 minutes. It is then exposed to polarized UV light for a total of 330 mJ/ ^cm² . This forms an alignment layer 3 on the substrate 2, defining the alignment direction. The formation of alignment layers from photopolymer solutions is known per se. For example, US Pat. No. 9,298,041 B2 describes alignment layers.

A solution containing a liquid crystal monomer (also designated herein as the second liquid crystal monomer) and a chiral dopant composition (as described in Example 4 of US Patent No. 6,120,859 or US Patent No. 9,298,041 B2) was spin-coated onto the sample, followed by an annealing step at 100°C for 1 minute on a hot plate. The sample was then exposed to UV light for a total of 3000 mJ/ ^cm² under a saturated nitrogen atmosphere. The resulting layer had a thickness of 1.05 μm. Furthermore, the chiral dopant-induced helical pitch of the layer was 8 μm, and the twist angle in the thickness direction of the layer was 78.2°. Therefore, a twisted liquid crystal retardation layer, i.e., the second outer layer 10-2 of the twisted liquid crystal retardation layer stack 10, is formed on the alignment layer 3, thereby forming an alignment interface 7. In addition, the orientation direction of the liquid crystal in the second outer layer 10-2 of the twisted liquid crystal retardation layer stack 10 adjacent to the alignment interface 7 is aligned with the alignment direction of the alignment layer 3.

Subsequently, a solution containing a composition comprising a liquid crystal monomer (also designated herein as the first liquid crystal monomer) and a chiral dopant was applied following the procedure described in Example 4 of US Patent No. 6,120,859 or US Patent No. 9,298,041 B2. The resulting layer had a thickness of 2.12 μm. Furthermore, the layer's helical pitch, induced by the chiral dopant, was 38 μm, and the twist angle in the thickness direction of the layer was 20.1°.

By annealing the composition comprising the first liquid crystal monomer, the orientation direction of the liquid crystal molecules at the interface between the polymerized composition comprising the second liquid crystal monomer and the coating film comprising the first liquid crystal monomer within the coating film comprising the first liquid crystal monomer is aligned with the orientation direction of the liquid crystal molecules at the interface between the polymerized composition comprising the second liquid crystal monomer and the coating film comprising the first liquid crystal monomer within the polymerized composition comprising the first liquid crystal monomer. The liquid crystals of the composition comprising the first liquid crystal monomer, polymerized by exposure to UV light, form the first outer layer 10-1 of the stack 10.

The stack 10 thus forms a multi-twisted retarder (MTR) which can be manufactured as described in US 9 298 041 B2.

A coatable polarizing solution was then spin-coated onto the sample and annealed on a hot plate at 100°C for 3 minutes. It was then exposed to UV light for a total of 1500 mJ/ ^cm² under a saturated nitrogen atmosphere. This polarizing solution is described in US Patent No. 10,385,215. Consequently, a linear polarizing layer 6 was formed, defining the polarization direction of the first outer layer 10-1 of the stack 10. Furthermore, a polarizing interface 8 was formed. Furthermore, the polarization direction of the polarizing layer 6 was aligned with the orientation direction of the liquid crystal within the first outer layer 10-1 of the stack 10, immediately adjacent to the polarizing interface 8.

If necessary, if thickness requirements are met, a second layer of a coatable polarizer can be added following the same process as for the coatable polarizer solution mentioned above. The embodiments of the optical structure 1 shown in Figures 1, 2, 4, 6, and 12 can be manufactured using methods similar to those of the first embodiment.

1: Optical structure 2: Substrate 3: Alignment layer 4: Twisted liquid crystal retardation layer 6: Linear polarizer 7: Alignment interface 8: Polarization interface 9: Retardation interface 10: Stack of twisted liquid crystal retardation layers 10-1: First outer layer 10-2: Second outer layer 11: Additional twisted liquid crystal retardation layer 12: Additional polarization interface

[Figure 1] shows a first embodiment of the optical structure of the present invention. [Figure 2] shows a second embodiment of the optical structure of the present invention. [Figure 3] shows a third embodiment of the optical structure of the present invention. [Figure 4] shows the optical structure of the third embodiment in another embodiment. [Figure 5] shows an experimental cone optical diagram of the optical structure of the third embodiment, with an incident angle from 30° to 50°, and an air gap between the mirror and the device. [Figure 6] shows a fourth embodiment of the optical structure of the present invention. [Figure 7] shows another embodiment of the optical structure of the fourth embodiment. [Figure 8] shows a diagram of the retardation and optical axis based on the wavelength display of the fourth embodiment of the optical retardation plate. [Figure 9A] shows a reflection cone pattern of the intensity simulation from a known optical structure, using a polarizer at a 45° angle and a linear reverse-dispersive retarder. [Figure 9B] shows a reflection cone pattern of the color ΔE simulation from a known optical structure, using a polarizer at a 45° angle and a linear reverse-dispersive retarder. [Figure 10A] shows a reflection cone pattern of the intensity simulation from the optical structure of the present invention, using a combination of two twisted standard dispersive retarder and the same polarizer aligned with the top director layer. Figure 10B shows a reflection cone plot of the color ΔE simulation of the optical structure of the present invention, using a combination of two twisted standard dispersion retarders and the same polarizer, with the polarizer aligned with the top director layer. Figure 11A shows a reflection cone plot of the intensity simulation of the optical structure of the present invention, using a single twisted reverse dispersion retarder and polarizer, with the polarizer and the retarder aligned at the top angle. Figure 11B shows a reflection cone plot of the color ΔE simulation of the optical structure of the present invention, using a single twisted reverse dispersion retarder and polarizer, with the polarizer and the retarder aligned at the top angle. Figure 12 shows a fifth embodiment of the optical structure of the present invention.

1: Optical structure

2:Substrate

3:Alignment layer

6: Linear polarizing layer

7: Alignment interface

8: Polarized interface

9: Delayed interface

10: Stacking of twisted liquid crystal delay layers

10-1: First Outer Layer

10-2: Second Outer Layer

Claims (15)

An optical structure (1) comprising: A linear polarizing layer (6), wherein the linear polarizing layer (6) defines a polarization direction; A twisted liquid crystal retardation layer (4) or a stack of twisted liquid crystal retardation layers (10), wherein the stack of twisted liquid crystal retardation layers (10) has a first outer layer (10-1) and a second outer layer (10-2), wherein the second outer layer (10-2) is located on the opposite side of the first outer layer (10-1), and the twisted liquid crystal retardation layer (4) or the first outer layer (10-1) of the stack of twisted liquid crystal retardation layers (10) is arranged at a polarization interface (8), wherein the polarization interface (8) is between the polarization layer (6) and the twisted liquid crystal retardation layer (4) or the stack of twisted liquid crystal retardation layers (10). wherein the first orientation direction of the liquid crystal in the twisted liquid crystal retardation layer (4) or the stack of twisted liquid crystal retardation layers (10) adjacent to the polarization interface (8) is set by the polarization direction of the polarization layer (6); and an alignment layer (3) and an alignment interface (7), wherein the alignment layer (3) defines the alignment direction, and the alignment interface (7) is an interface between the alignment layer (3) and a layer adjacent to the alignment layer (3), wherein the adjacent layer is selected from the polarization layer (6), the twisted liquid crystal retardation layer (4) and the second outer layer (10-2) of the stack of twisted liquid crystal retardation layers (10), Wherein, if the alignment interface (7) is an interface between the alignment layer (3) and the polarizing layer (6), the alignment direction of the alignment layer (3) sets the polarization direction of the polarizing layer (6), or Wherein, if the alignment interface (7) is an interface between the alignment layer (3) and the twisted liquid crystal retardation layer (4) or the second outer layer (10-2) of the stack (10) of twisted liquid crystal retardation layers, the alignment direction of the alignment layer (3) sets the second orientation direction of the liquid crystal in the twisted liquid crystal retardation layer (4) or the second outer layer (10-2) of the stack (10) of twisted liquid crystal retardation layers adjacent to the alignment interface (7). The optical structure (1) of claim 1, wherein the polarizing layer (6) is a coatable layer. The optical structure (1) of claim 1 or 2, wherein the polarizing layer (6) comprises a liquid crystal polymer material and at least a dichroic dye and/or at least a fluorescent dye. An optical structure (1) as claimed in any one of the preceding claims, comprising a stack (10) of twisted liquid crystal retardation layers, wherein at least one retardation interface (9) is formed between two adjacent twisted liquid crystal retardation layers (10-1, 10-2) of the stack (10) of twisted liquid crystal retardation layers. An optical structure (1) as claimed in any one of the preceding claims, wherein the helical pitch of one twisted liquid crystal retardation layer (10-1) of the stack of twisted liquid crystal retardation layers (10) is different from the helical pitch of another twisted liquid crystal retardation layer (10-2) of the stack of twisted liquid crystal retardation layers (10). An optical structure (1) as claimed in any one of the preceding claims, wherein the twisted liquid crystal retardation layer (4) or at least one twisted liquid crystal retardation layer (10-2) of the stack (10) of twisted liquid crystal retardation layers is a high twist retardation plate. An optical structure (1) as claimed in any one of the preceding claims, wherein the alignment interface (7) is an interface between the alignment layer (3) and the twisted liquid crystal retarder layer (4) or the second outer layer (10-2) of the stack of twisted liquid crystal retarder layers (10), the polarization interface (8) is arranged between the polarization layer (6) and the twisted liquid crystal retarder layer (4) or the stack of twisted liquid crystal retarder layers (10), and The optical structure (1) comprises another twisted liquid crystal retardation layer (11) or another stack of twisted liquid crystal retardation layers, the stack of twisted liquid crystal retardation layers having another first outer layer and another second outer layer, the second outer layer being on the opposite side of the first outer layer, the first outer layer of the other twisted liquid crystal retardation layer (11) or the stack of twisted liquid crystal retardation layers being arranged at another polarization interface (12), the other polarization interface (12) being between the polarization layer (6) and the other twisted liquid crystal retardation layer (11) or the stack of twisted liquid crystal retardation layers. The first orientation direction of the liquid crystal in the additional twisted liquid crystal retardation layer (11) or the stack of the additional twisted liquid crystal retardation layers adjacent to the additional polarization interface (12) is set by the polarization direction of the polarization layer (6). An antireflection device comprising an optical structure (1) as claimed in any one of the preceding claims, wherein the pitch of the twisted liquid crystal retardation layer (4) or the pitch of the twisted liquid crystal retardation layers (10-1, 10-2) of the stack (10) is set to form an achromatic quarter-wave retardation plate. A method for manufacturing an optical structure (1), comprising the following steps: (a)    forming an alignment layer (3), wherein the alignment layer (3) defines an alignment direction, (b1) forming a linear polarizing layer (6), wherein the linear polarizing layer (6) defines a polarization direction of the alignment layer (3), and wherein the polarization direction of the polarizing layer (6) is set by the alignment direction of the alignment layer (3), thereby forming an alignment interface (7), (c1) A twisted liquid crystal retardation layer (4) or a stack of twisted liquid crystal retardation layers (10) is formed, wherein the stack of twisted liquid crystal retardation layers (10) has a first outer layer (10-1) and a second outer layer (10-2), wherein the second outer layer (10-2) is on the opposite side of the first outer layer (10-1), and the twisted liquid crystal retardation layer (4) or the stack of twisted liquid crystal retardation layers ( The first outer layer (10-1) of the twisted liquid crystal retardation layer (4) or the stack (10) of twisted liquid crystal retardation layers is arranged on the polarizing layer (6) to form a polarizing interface (8), wherein the first orientation direction of the liquid crystal adjacent to the polarizing interface (8) in the first outer layer (10-1) of the twisted liquid crystal retardation layer (4) or the stack (10) of twisted liquid crystal retardation layers is set by the polarization direction of the polarizing layer (6). A method for manufacturing an optical structure (1) having a layer structure, comprising the following steps: (a) forming an alignment layer (3), wherein the alignment layer (3) defines an alignment direction, (b2) forming a twisted liquid crystal retardation layer (4) or a stack of twisted liquid crystal retardation layers (10), wherein the stack of twisted liquid crystal retardation layers (10) has a first outer layer (10-1) and a second outer layer (10-2), wherein the second outer layer (10-2) is on the opposite side of the first outer layer (10-1), and the twisted liquid crystal retardation layer (4) or the stack of twisted liquid crystal retardation layers ( The second outer layer (10-2) of the twisted liquid crystal retardation layer (4) or the stack (10) of twisted liquid crystal retardation layers is arranged on the alignment layer (3) to form an alignment interface (7), wherein the second orientation direction of the liquid crystal adjacent to the alignment interface (7) in the second outer layer (10-2) of the twisted liquid crystal retardation layer (4) or the stack (10) of twisted liquid crystal retardation layers is set by the orientation direction of the alignment layer (3). (c2) forming a linear polarizing layer (6), wherein the linear polarizing layer (6) defines the polarization direction on the first outer layer (10-1) of the twisted liquid crystal retardation layer (4) or the stack (10) of twisted liquid crystal retardation layers, thereby forming a polarization interface (8), wherein the polarization direction of the polarizing layer (6) is set by the first orientation direction of the liquid crystal in the first outer layer (10-1) of the twisted liquid crystal retardation layer (4) or the stack (10) of twisted liquid crystal retardation layers, adjacent to the polarization interface (8). The method of claim 10, wherein step (b2) comprises: coating a second component on the alignment layer (3) to form the alignment interface (7), the second component comprising a second liquid crystal monomer and a second chiral dopant, the second component containing a polymerizable liquid crystal; annealing the second component, whereby the second orientation direction of the liquid crystal coated in the second component adjacent to the alignment interface (7) is set by the orientation direction of the alignment layer (3); inducing polymerization of the polymerizable liquid crystal in the second component by exposure to UV light, thereby forming the twisted liquid crystal retardation layer (4) or the second outer layer (10-2) of the stack (10) of twisted liquid crystal retardation layers at the alignment interface (7). The method of claim 11, further comprising: coating a first component on the polymerized second component, the first component comprising a first liquid crystal monomer and a first chiral dopant, the first component containing a polymerizable liquid crystal; annealing the first component so that the third orientation direction of the liquid crystal at the interface between the polymerized second component and the first component coating in the first component coating is aligned with the fourth orientation direction of the liquid crystal at the interface between the polymerized second component and the first component coating in the polymerized second component; inducing polymerization of the polymerizable liquid crystal in the first component by exposure to UV light, thereby forming another layer of the stack (10) of twisted liquid crystal retardation layers. The method of any one of claims 10 to 12 further comprises: Coating a polarizing solution on the twisted liquid crystal retardation layer (4) or the stack of twisted liquid crystal retardation layers (10) to form the polarizing interface (8), wherein the polarizing solution contains a polymerizable liquid crystal; Annealing the polarizing solution, whereby the polarization direction of the polarizing solution is set by the first orientation direction of the liquid crystal in the first outer layer (10-1) of the twisted liquid crystal retardation layer (4) or the stack of twisted liquid crystal retardation layers (10) adjacent to the polarizing interface (8); Inducing polymerization of the polymerizable liquid crystal in the polarizing solution by exposure to UV light to form the polarizing layer (6). The method of claim 13 further comprises: applying an additional polarizing solution onto the polymerized polarizing solution, the additional polarizing solution containing a polymerizable liquid crystal; annealing the additional polarizing solution so that the polarization direction of the additional polarizing solution is aligned with the polarization direction of the polymerized polarizing solution at the interface between the polymerized polarizing solution and the additional polarizing solution; inducing polymerization of the polymerizable liquid crystal in the additional polarizing solution by exposure to UV light, thereby forming a stack of parallel polarizing layers. The method of any one of claims 10 to 14, further comprising: Another twisted liquid crystal retardation layer (11) or another stack of twisted liquid crystal retardation layers is formed, the stack of twisted liquid crystal retardation layers having another first outer layer and another second outer layer, the other second outer layer being on the opposite side of the other first outer layer, the other twisted liquid crystal retardation layer or the other second outer layer of the stack of twisted liquid crystal retardation layers being arranged on the polarizing layer (6), thereby forming another polarizing interface (12), wherein the first orientation direction of the liquid crystal in the other twisted liquid crystal retardation layer (11) or the other second outer layer of the stack of twisted liquid crystal retardation layers adjacent to the other polarizing interface (12) is set by the polarization direction of the polarizing layer (6).