Patent Description:
Windows are important components of modern architectures, such as vehicles and buildings and can allow natural light to enter indoor spaces, thereby providing a comfortable, healthy and safe environment for occupants. However, natural light entering through a window may also cause danger and discomfort. Sunlight consists of ultraviolet rays (<NUM>-<NUM>), visible light (<NUM>-<NUM>) and near infrared rays (<NUM>-<NUM>,<NUM>). The ultraviolet rays interact with materials, such as furniture in buildings, causing discoloration and degradation, and interact with human skin, potentially and negatively affecting human health. Therefore, it is desirable that the window can blocks the ultraviolet rays. Visible light transmission can greatly affect comfort and appearance of a building. The interaction of the window material with the visible light of the solar spectrum determines the coloring of the window. The near infrared sunlight accounts for <NUM>% of solar energy and plays a major role in heating the indoor spaces, which may cause thermal discomfort to the occupants and increase energy consumption for artificial refrigeration. In order to protect indoor materials and the occupants from harms caused by the ultraviolet rays, a laminated glass in which an ultraviolet ray absorbing interlayer (such as polyvinyl butyral) is sandwiched is commonly used.

Another important property of the window is its thermal insulation ability, which is mainly determined by the interaction of the window material with the near infrared sunlight. Thus, metal-containing IR absorbing dyes are widely used in the window material. These dyes reduce a solar transmission but also substantially absorb the visible light, thus coloring the window glass. In addition, the dyes may heat up and dissipate internal heat. A thin metal matrix which can reflect near infrared sunlight can also be coated on a top part of the glass, commonly known as a low-radiation coating. A layer thickness (< <NUM>) should be precisely controlled to obtain uniform and high visible light transmission, which can be obtained a vapor deposition technology.

Near infrared light can also be reflected using a photonic structure. In the photonic structure, materials with different refractive indices (n) are periodically structured because they can reflect light of a particular wavelength at a material interface. The simplest photonic structure is a multi-layered structure, in which two materials with different refractive indices alternate, which is called a distributed Bragg reflector. <FIG> is a schematic structural diagram of the Bragg reflector. A selective reflection band can be set into near infrared rays by precisely controlling thickness and the refractive indices variation of each layer.

As an alternative to the photonic structure, the cholesteric liquid crystal (CLC) can be used as a near infrared reflective material. Liquid crystal is a material that has properties between three-dimensionally ordered solids and isotropic liquids. The liquid crystal has a long-distance order in one or two dimensions and thus has anisotropy. For example, the liquid crystal is birefringent, which means that a refractive index (ne) parallel to a long molecular axis is different from the refractive index (no) perpendicular to the molecular axis. By adding the chiral dopant to the liquid crystal material, molecular directors of the continuous liquid crystal plane rotate relative to each other in a periodic spiral manner. <FIG> is a schematic diagram of a CLC periodic helical structure.

Patent document <CIT> describes an infrared light reflecting plate for reflecting infrared light, which comprises a substrate and at least four light-reflective layers, each of which is formed of a fixed cholesteric liquid-crystal phase.

The present disclosure provides a liquid crystal multilayer film and a preparation method thereof, as defined by the independent claims. Other aspects of the invention are defined by the dependent claims.

Other features and advantages of the present disclosure will be described in the following specification, and some of these will become apparent from the specification or be understood by implementing the present disclosure. The objectives and other advantages of the present disclosure can be implemented or obtained by structures specifically indicated in the specification, claims, and accompanying drawings.

The accompanying drawings are provided for further understanding of the present disclosure, constitute a part of the specification, are intended to explain the technical solutions of the present disclosure with the examples of the present disclosure, but do not intended to limit the technical solutions of the present disclosure.

As used herein, the term "and/or" includes any and all combinations of one or more related items listed. The terms used herein are only used to describe the specific examples, but are not intended to limit the present disclosure. As used herein, the singular forms "a", "an", and "the" are intended to include plural forms, unless the context clearly indicates. For further understanding, the terms "comprises" "comprising," "includes" and/or "including" used herein, specify the stated features, integers, steps, operations, elements, components, and/or combinations thereof, but do not preclude the presence of one or more additional features, integers, steps, operations, elements, components, and/or combinations thereof.

Unless otherwise specified, all terms used herein (including technical and scientific terms) have the same meanings as those generally understood by those of ordinary skill in the art to which the present disclosure pertains. It will be further understood that the terms, such as those defined in commonly used dictionaries, are interpreted in accordance with their meanings in the context of the relevant field, and are not idealized or overly formal meanings unless clearly defined as such herein.

The exemplary disclosure described herein may appropriately lack any one or more element limitations, which is not specifically disclosed herein. Therefore, the terms "comprises", "comprising", "includes", "including", "contains", "containing" and the like should be understood broadly and non-limitingly. In addition, the term expressions used herein are used for description without limitation, the use of the term expressions that do not include any equivalent characteristics is unintentional, the term expressions only describes some of their characteristics. But according to the rights, various modifications within the scope of the present disclosure are possible. Therefore, although the present disclosure has been specifically disclosed through the preferred examples and optional features, the modifications disclosed herein to embody changes of the present disclosure may be recorded by those skilled in the art, and such modifications and changes will be considered as within the scope of the present disclosure.

The present disclosure has been described broadly and generally here. Smaller species and subgeneric groupings falling within the generic disclosure also form a part of the present disclosure. This includes the removal of any subject matter within the scope of the appended claims, regardless of whether a reduced material is specifically recited herein.

Other examples are included in the following claims and non-limiting examples. In addition, the technical features or related contents of the present disclosure are subject to description of the terms of the Markush group. Those skilled in the art will recognize that the present disclosure is also described by any independent explicit terms or subgroup terms of the Markush group.

The concepts, specific content and technical effects of the present disclosure are clearly and completely described below in conjunction with examples, so as to allow the objectives, features and effects of the present disclosure to be fully understood. Apparently, the described examples are merely some rather than all of the examples of the present disclosure. All other examples obtained by those skilled in the art based on the examples of the present disclosure without creative efforts should fall within the protection scope of the present disclosure. The raw materials used in the following examples are all commercially available, unless otherwise specified. The preparation methods in the examples are all conventional methods, unless otherwise specified.

<FIG> is a liquid crystal multilayer film provided by an example of the present disclosure. As shown in <FIG>, the multilayer film at least includes a first cholesteric liquid crystal layer <NUM> and a first ultraviolet blocking material <NUM>. The first cholesteric liquid crystal layer <NUM> is coated on the first ultraviolet blocking material <NUM>. The first cholesteric liquid crystal layer <NUM> has a thickness between <NUM> to <NUM>. The first cholesteric liquid crystal layer <NUM> includes a polymerizable liquid crystal monomer, a levorotatory polymerizable chiral dopant and a photoinitiator. The levorotatory polymerizable chiral dopant accounts for <NUM>-<NUM> wt% of the first cholesteric liquid crystal layer <NUM>. The photoinitiator accounts for <NUM>-<NUM> wt% of the first cholesteric liquid crystal layer <NUM>. The multilayer film can filter ultraviolet rays and near infrared rays in natural light, thereby reducing the influences of the ultraviolet rays on people and objects indoors, and reducing the heat effect caused by near infrared rays.

In an example, the first cholesteric liquid crystal layer <NUM> includes dextrorotatory or levorotatory cholesteric liquid crystal. The polymerizable chiral dopant is a levorotatory chiral dopant, and the liquid crystal mixture includes a polymerizable liquid crystal monomer, <NUM>-<NUM> wt% of the levorotatory chiral dopant and <NUM>-<NUM> wt% of a photoinitiator. Alternatively, the polymerizable chiral dopant is a dextrorotatory chiral dopant, and the liquid crystal mixture includes a polymerizable liquid crystal monomer, <NUM>-<NUM> wt% of the dextrorotatory chiral dopant and <NUM>-<NUM> wt% of a photoinitiator. The cholesteric liquid crystals have a multi-layer structure, molecular directions in the same layer are the same and molecular directions of adjacent layers are deflected, thus a dextrorotatory polarized light can be reflected. Due to a selective polarization reflection of the cholesteric liquid crystal, the adjusted dextrorotatory cholesteric liquid crystal can reflect near infrared rays in natural light according to the Bragg effect. Since the near infrared rays contain more than half of the energy of the natural light, reflecting near infrared rays can reduce the heat effect of the natural light passing through the multilayer film.

In an example, the arrangement of the cholesteric liquid crystals includes a chiral nematic phase. The polymerizable chiral dopant is added during preparation of the cholesteric liquid crystals, thus the cholesteric liquid crystal has a selective reflection function, and a reflecting effect on specific wavelengths of light is realized.

<FIG> is a multilayer film provided by another example of the present disclosure. As shown in <FIG>, the multilayer film at least includes a first cholesteric liquid crystal layer <NUM>, a second cholesteric liquid crystal layer <NUM>, a first ultraviolet blocking material <NUM> and a second ultraviolet blocking material <NUM>. The second cholesteric liquid crystal layer <NUM> is coated on the first cholesteric liquid crystal layer <NUM>, and the second ultraviolet blocking material <NUM> is coated on the second cholesteric liquid crystal layer <NUM>. The second cholesteric liquid crystal layer <NUM> has a thickness between <NUM> and <NUM>. The second cholesteric liquid crystal layer <NUM> includes a polymerizable liquid crystal monomer, a dextrorotatory polymerizable chiral dopant and a photoinitiator. The dextrorotatory polymerizable chiral dopant accounts for <NUM>-<NUM>% of the second cholesteric liquid crystal layer <NUM>, and the photoinitiator accounts for <NUM>-<NUM> wt% of the second cholesteric liquid crystal layer <NUM>. The polymerizable liquid crystal monomer, the dextrorotatory polymerizable chiral dopant and the photoinitiator accounts for a total weight of <NUM> wt%. The multilayer film can filter ultraviolet rays and near infrared rays in natural light, thereby reducing the influences of the ultraviolet rays on people and objects indoors, and reducing the heat effect caused by near infrared rays.

In an example, the first cholesteric liquid crystal layer <NUM> and the second cholesteric liquid crystal layer <NUM> may have opposite chirality. The levorotatory cholesteric liquid crystals have a multi-layer structure, molecular directions in the same layer are the same and molecular directions of adjacent layers are deflected, thus a levorotatory polarized light can be reflected. The levorotatory cholesteric liquid crystal are combined with the dextrorotatory cholesteric liquid crystal to reflect the levorotatory polarized light and the dextrorotatory polarized light. Since near infrared rays in natural light comprise the levorotatory polarized light and the dextrorotatory polarized light, reflecting the levorotatory polarized light and the dextrorotatory polarized light can reduce the transmission rate of the near infrared rays.

<FIG> is a diagram showing a light transmission rate of a liquid multilayer film provided by an example of the present disclosure. As shown in <FIG>, the levorotatory polymerizable chiral dopant accounts for <NUM> wt% of the first cholesteric liquid crystal layer <NUM>, the photoinitiator accounts for <NUM> wt% of the first cholesteric liquid crystal layer <NUM>, and the polymerizable liquid crystal monomer accounts for <NUM> wt% of the first cholesteric liquid crystal layer <NUM>. The mixture to prepare the first cholesteric liquid crystal layer <NUM> further includes <NUM> wt% of an organic solvent cyclopentanone, in which <NUM> wt% of a surfactant BYK-361N is dissolved. The liquid crystal mixture is dissolved in the organic solvent cyclopentanone at a ratio of <NUM>:<NUM>, and the liquid crystal mixture with a thickness of <NUM> is coated on the first ultraviolet blocking material <NUM> polyethylene terephthalate (PET) at a speed of <NUM>/s, heated at <NUM> for <NUM>, and irradiated by using ultraviolet rays at a light intensity of <NUM> mJ/cm<NUM> to obtain a multilayer film. The multilayer film can reduce the transmission rate of ultraviolet rays to <NUM>% and the transmission rate of near infrared rays with the wavelength around <NUM> and the bandwidth of <NUM> to <NUM>%, and at the same time maintain the transmission rate of visible light at <NUM>% and the total transmission rate of natural light at <NUM>%. The multilayer film can reduce the transmission rates of the ultraviolet rays and the near infrared rays in natural light, and reduce harms brought by the ultraviolet rays and the heat effect brought by the near infrared rays. At the same time, the high transmission rate of the visible light can ensure that the natural light passing through the multilayer film has a low distortion rate. When the multilayer film is used for ultraviolet and near-infrared protection, the low distortion rate of the natural light can still be ensured when observing at <NUM> degrees from the side surface of the multilayer film.

<FIG> is a diagram showing a transmission rate of a liquid crystal multilayer film provided by an example of the present disclosure. As shown in <FIG>, the multilayer film includes a first ultraviolet blocking material <NUM>, a first cholesteric liquid crystal layer <NUM>, a second cholesteric liquid crystal layer <NUM> and a second ultraviolet blocking material. The first cholesteric liquid crystal layer <NUM> has the same components as the first cholesteric liquid crystal <NUM> in <FIG>. The dextrorotatory polymerizable chiral dopant accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, the photoinitiator accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, and the polymerizable liquid crystal monomer accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>. The mixture to prepare the second cholesteric liquid crystal layer <NUM> includes <NUM> wt% of an organic solvent cyclopentanone, in which <NUM> wt% of a surfactant BYK-361N is dissolved. The liquid crystal mixture is dissolved in the organic solvent cyclopentanone at a ratio of <NUM>:<NUM>, and the liquid crystal mixture with a thickness of <NUM> is coated on the first ultraviolet blocking material <NUM> polyethylene terephthalate (PET) at a speed of <NUM>/s, heated at <NUM> for <NUM>, and irradiated by using ultraviolet rays at a light intensity of <NUM> mJ/cm<NUM> to obtain a multilayer film. The multilayer film can reduce the transmission rate of ultraviolet rays to be least than <NUM>% and the transmission rate of near infrared rays with the wavelength around <NUM> and the bandwidth of <NUM> to <NUM>%, and at the same time maintain the transmission rate of visible light at <NUM>% and the total transmission rate of natural light at <NUM>%. When used to filter natural light, the multilayer film can reduce the heat effect brought by the near infrared rays.

<FIG> is a diagram showing a transmission rate of a liquid crystal multilayer film provided by an example of the present disclosure. As shown in <FIG>, in the multilayer film, the levorotatory polymerizable chiral dopant accounts for <NUM> wt% of the first cholesteric liquid crystal layer <NUM>, the photoinitiator accounts for <NUM> wt% of the first cholesteric liquid crystal layer <NUM>, and the polymerizable liquid crystal monomer accounts for <NUM> wt% of the first cholesteric liquid crystal layer <NUM>. The mixture to prepare the first cholesteric liquid crystal layer <NUM> further includes <NUM> wt% of an organic solvent cyclopentanone, in which <NUM> wt% of a surfactant BYK-361N is dissolved. In the second cholesteric liquid crystal layer <NUM>, the dextrorotatory polymerizable chiral dopant accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, the photoinitiator accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, and the polymerizable liquid crystal monomer accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>. The mixture to prepare the second cholesteric liquid crystal layer <NUM> further includes <NUM> wt% of the organic solvent cyclopentanone, in which <NUM> wt% of the surfactant BYK-361N is dissolved. The liquid crystal mixture is dissolved in the organic solvent cyclopentanone at a ratio of <NUM>:<NUM>, and the liquid crystal mixture with a thickness of <NUM> is coated on the first ultraviolet blocking material <NUM> polyethylene terephthalate (PET) at a speed of <NUM>/s, heated at <NUM> for <NUM>, and irradiated by using ultraviolet rays at a light intensity of <NUM> mJ/cm<NUM> to obtain a multilayer film. The multilayer film can reduce the transmission rate of ultraviolet rays to be less than <NUM>% and the transmission rate of near infrared rays with the wavelength of <NUM> and the bandwidth of <NUM> to <NUM>%, and at the same time maintain the transmission rate of visible light at <NUM>% and the total transmission rate of natural light at <NUM>%. When used to filter natural light, the multilayer film can reduce influences of the ultraviolet rays and near infrared rays on people and objects.

<FIG> is a diagram showing a transmission rate of a multilayer film provided by an example of the present disclosure. As shown in <FIG>, in the multilayer film, the first cholesteric liquid crystal layer <NUM> is the same as the first cholesteric liquid crystal layer <NUM> in <FIG>. In the second cholesteric liquid crystal layer <NUM>, the polymerizable chiral dopant accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, the photoinitiator Irgacure <NUM> accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, and the polymerizable liquid crystal monomer accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>. The mixture to prepare the second layer further includes <NUM> wt% of an organic solvent, in which <NUM> wt% of a surfactant is dissolved in the organic solvent. The second cholesteric liquid crystal layer <NUM> further includes <NUM> wt% of the organic solvent, and <NUM> wt% of the surfactant is dissolved in the organic solvent. The polymerizable chiral dopant accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, the photoinitiator accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>, and the polymerizable liquid crystal monomer accounts for <NUM> wt% of the second cholesteric liquid crystal layer <NUM>. The liquid crystal mixture is dissolved in the organic solvent cyclopentanone at a ratio of <NUM>:<NUM>, and the liquid crystal mixture with a thickness of <NUM> is coated on the first ultraviolet blocking material <NUM> polyethylene terephthalate (PET) at a speed of <NUM>/s, heated at <NUM> for <NUM>, and irradiated by using ultraviolet rays at a light intensity of <NUM> mJ/cm<NUM> to obtain a multilayer film. The multilayer film can reduce the transmission rate of ultraviolet rays to be less than <NUM>% and the transmission rate of near infrared rays with the wavelength of <NUM> and the bandwidth of <NUM> to <NUM>%, and at the same time maintain the transmission rate of visible light at <NUM>% and the total transmission rate of natural light at <NUM>%. When used to filter natural light, the multilayer film can reduce influences of the ultraviolet rays and near infrared rays on people and objects.

In an example, when the photoinitiator accounts for <NUM> wt% of the cholesteric liquid crystal layers, the coating process of the cholesteric liquid crystal layers can be conducted in an air environment. The coating in the air environment can reduce the cost of preparing the multilayer film.

In an example, when the photoinitiator accounts for <NUM> wt% of the cholesteric liquid crystal layers, the coating process of the cholesteric liquid crystal layers needs to be conducted in one or more of nitrogen, helium, neon, argon, krypton, and xenon environments. The coating process in the specific gas environment can improve purity of the cholesteric liquid crystal layers, and reduce the amount of the photoinitiator.

In an example, the surfactant is polyacrylate-based surfactant. The polyacrylate-based surfactant includes at least one selected from the group consisting of Byk-361N, Byk-<NUM>, Byk-UV <NUM> and Byk-Dynwet 800N. The surfactant can improve wettability of the cholesteric liquid crystal solution.

In an example, the matrix material includes at least one selected from the group consisting of glass, polyethylene terephthalate, biaxially oriented polypropylene, and polycarbonate. The matrix can filter ultraviolet rays with the wavelength of <NUM>-<NUM>, and reduce the transmission rate of the ultraviolet rays. The ultraviolet rays can cause harms to people and objects.

In an example, the polymerizable liquid crystal monomer material includes <NUM>-(methoxycarbonyl)-<NUM>,<NUM>-phenylene-bis(<NUM>-((((<NUM>-(acryloyloxyoxy)ethoxy)carbonyl)oxy)-<NUM>-naphthoic acid).

In one example, the levorotatory polymerizable chiral dopant is used to modulate the cholesteric liquid crystal into the dextrorotatory cholesteric liquid crystal.

In an example, the levorotatory polymerizable chiral dopant includes (3R, 3aR, <NUM>, 6aR)-hexahydro furan [<NUM>,<NUM>-b] furan-<NUM>,<NUM>-diyl bis(<NUM>-((<NUM>-((((<NUM>-(acryloyloxy)butoxy)carbonyl)oxy)benzoyl)oxy)benzoate).

In one example, the dextrorotatory polymerizable chiral dopant is used to modulate the cholesteric liquid crystal into the levorotatory cholesteric liquid crystal.

In an example, the dextrorotatory polymerizable chiral dopant includes (((((3R, 3aR, <NUM>, 6aR)-hexahydro furan [<NUM>,<NUM>-b] furan-<NUM>,<NUM>-diyl)bis(oxy)bis(carbonyl)bis(<NUM>,<NUM>-phenylene)bis(<NUM>-((((<NUM>-(acryloxyoxy)butoxy)carbonyl)oxy)-<NUM>-naphthoic acid).

<FIG> is a process diagram of a preparation method of a multilayer film provided by an example of the present disclosure. As shown in <FIG>, the preparation method includes the following steps:.

In an example, the cholesteric liquid crystal is coated on the ultraviolet blocking material, and the multilayer film is heated and irradiated with the ultraviolet rays to cure the cholesteric liquid crystal into a cholesteric liquid crystal layer. Levorotatory or dextrorotatory chirality of the cholesteric liquid crystal layer is maintained.

In an example, the cholesteric liquid crystal is dissolved in an organic solvent. Dissolving the cholesteric liquid crystal in the organic solvent may increase fluidity the cholesteric liquid crystal, such that the cholesteric liquid crystal can be coated on the ultraviolet blocking material.

In an example, the organic solvent includes at least one selected from the group consisting of cyclopentanone, methyl ethyl ketone, cyclohexanone and toluene.

In an example, the cholesteric liquid crystal is coated on the ultraviolet blocking material, specifically, the cholesteric liquid crystalwith a thickness of <NUM>-<NUM> is coated on the ultraviolet blocking material at a speed of <NUM>/s to <NUM>/s. After the cholesteric liquid crystal is dissolved in the organic solvent, the cholesteric liquid crystal may be coated on the ultraviolet blocking material. When the thickness of the cholesteric liquid crystal is <NUM>-<NUM>, the levorotatory polarized light or the dextrorotatory polarized light can be reflected.

In an example, the multilayer film is heated at <NUM> to <NUM> for at least <NUM> seconds. The multilayer film is heated to volatilize the organic solvent and retain the cholesteric liquid crystal on the matrix.

In an example, the multilayer film is irradiated with long-wave ultraviolet rays with a light intensity of at least <NUM> mJ/cm<NUM>. Irradiating the multilayer film with the long-wave ultraviolet rays can cure the cholesteric liquid crystal into the cholesteric liquid crystal layer.

Claim 1:
A liquid crystal multilayer film, comprising:
a first ultraviolet blocking material, and
a first cholesteric liquid crystal layer, wherein the first cholesteric liquid crystal layer is coated on the first ultraviolet blocking material;
wherein the first cholesteric liquid crystal layer is prepared from a liquid crystal mixture comprising a polymerizable liquid crystal monomer, a polymerizable chiral dopant and a photoinitiator;
the polymerizable chiral dopant is a levorotatory chiral dopant, and the liquid crystal mixture comprises the polymerizable liquid crystal monomer, <NUM>-<NUM> wt% of the levorotatory chiral dopant and <NUM>-<NUM> wt% of the photoinitiator; or the polymerizable chiral dopant is a dextrorotatory chiral dopant, and the liquid crystal mixture comprises the polymerizable liquid crystal monomer, <NUM>-<NUM> wt% of the dextrorotatory chiral dopant and <NUM>-<NUM> wt% of the photoinitiator; and
the liquid crystal multilayer film further comprises:
at least a second cholesteric liquid crystal layer which is coated on the first cholesteric liquid crystal layer; and the first cholesteric liquid crystal layer and the second cholesteric liquid crystal layer have different chirality.