WINDOW FILM AND METHOD FOR OPERATING THE SAME

Provided is a variable-transmittance window film capable of being operated in four different colors, and the window film of the present invention includes a first film, a second film spaced apart from the first film, a third film interposed between the first film and the second film, a suspended particle layer between the first film and the third film, and a polymer dispersed liquid crystal layer between the second film and the third film, wherein the polymer dispersed liquid crystal layer includes a dye having a second color complementary to a first color of the suspended particle layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35 U.S.C. § 119 of Korean Patent Application No. 10-2023-0094507, filed on Jul. 20, 2023, the entire contents of which are hereby incorporated by reference.

BACKGROUND

The present disclosure herein relates to a window film, and more particularly, to a variable-transmittance window film capable of being operated in four different colors.

A suspended particle device (SPD) has been examined for application in a manner of controlling the amount of light transmitted in variable-transmittance devices such as displays, smart windows, and automotive sunroofs, filters for optical fibers, and applications such as toys, sun visors, eyewear, and mirrors.

The SPD is used in various fields such as smart windows of transportation devices such as automobiles and building windows due to its large area, shape control, continuous transmission control, and low power consumption, but there is a restriction in use of the SPD due to the prominent blue color thereof in the absence of an electric field.

SUMMARY

The present disclosure provides a window film having an opaque state in a black color.

The present disclosure also provides a method for operating a window film, the method capable of controlling the state of the film in four different colors.

An embodiment of the inventive concept provides a window film including a first film, a second film spaced apart from the first film, a third film interposed between the first film and the second film, a suspended particle layer between the first film and the third film, and a polymer dispersed liquid crystal layer between the second film and the third film, wherein the polymer dispersed liquid crystal layer may include a dye having a second color complementary to a first color of the suspended particle layer.

In an embodiment of the inventive concept, there is provided a method for operating a window film, wherein the window film includes a first film, a second film spaced apart from the first film, a third film interposed between the first film and the second film, a suspended particle layer between the first film and the third film, and a polymer dispersed liquid crystal layer between the second film and the third film, and the method includes a first step of controlling the application of a first electric field to the suspended particle layer, and a second step of controlling the application of a second electric field to the polymer dispersed liquid crystal layer.

DETAILED DESCRIPTION

In order to facilitate sufficient understanding of the configuration and effects of the present invention, preferred embodiments of the inventive concept will be described with reference to the accompanying drawings. However, the present invention is not limited to the embodiments set forth below, and may be embodied in various forms and modified in many alternate forms. Rather, the present embodiments are provided so that the disclosure of the present invention will be thorough and complete, and will fully convey the scope of the present invention to those skilled in the art to which the inventive concept pertains.

In the present specification, when an element is referred to as being on another element, it means that the element may be directly formed on the other element, or that a third element may be interposed therebetween. Also, in the drawings, the thickness of elements are exaggerated for an effective description of technical contents. Like reference numerals refer to like elements throughout the specification.

Embodiments described in the present specification will be described with reference to cross-sectional views and/or plan views which are ideal illustrations of the present invention. In the drawings, regions illustrated have schematic properties, and the shapes of the regions illustrated in the drawings are intended to exemplify specific shapes of regions of a window film and are not intended to limit the scope of the present invention. Although the terms first, second, and the like are used in various embodiments of the present specification to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. The embodiments described and exemplified herein also include the complementary embodiments thereof.

The terms used herein are for the purpose of describing embodiments and are not intended to be limiting of the present invention. In the present specification, singular forms include plural forms unless the context clearly indicates otherwise. As used herein, the terms ‘comprises’ and/or ‘comprising’ are intended to be inclusive of the stated elements, and do not exclude the possibility of the presence or the addition of one or more other elements.

FIG.1illustrates a window film according to an embodiment of the present invention.

Referring toFIG.1, a window film600may include a first film100, a second film200, a third film300, a suspended particle layer400between the first film and the third film, and a polymer dispersed liquid crystal layer500between the second film200and the third film300. The suspended particle layer400may have a first color. The polymer dispersed liquid crystal layer500may have a second color complementary to the first color. For example, the first color may be a blue color, and the second color may be an orange color. As an embodiment of the present invention, the polymer dispersed liquid crystal layer500may include a dye510having the second color.

The window film600may further include a first conductive film110between the first film100and the suspended particle layer400, a second conductive film120between the third film300and the suspended particle layer400, a third conductive film210between the third film300and the polymer dispersed liquid crystal layer500, and a fourth conductive film220between the second film200and the polymer dispersed liquid crystal layer500. Each of the first to fourth conductive films may include at least one selected from the group consisting of indium zinc oxide (ITO), silver nanowire, aluminum, carbon nanotube (CNT), graphene, PEDOT:PSS, polyaniline, and polythiophene.

A first control unit10configured to apply a first electric field to the suspended particle layer400may be connected to the first conduction film110and the second conduction film120. A second control unit20configured to apply a second electric field to the polymer dispersed liquid crystal layer500may be connected to the third conductive film210and the fourth conductive film220. The first control unit10and the second control unit20may be connected to a film control unit30. Through the film control unit30, the first control unit10and the second control unit20may operate independently of each other.

Each of the first to third films100,200, and300may include a transparent polymer. The first to third films100,200, and300may be configured to support the suspended particle layer400and the polymer dispersed liquid crystal layer500. The third film300may physically connect the suspended particle layer400and the polymer dispersed liquid crystal layer500to each other by being interposed therebetween.

The suspended particle layer400may include a dispersion410containing an organic fluid or organic gel, and suspended particles420dispersed in the dispersion. In order to supplement the impact resistance of the suspended particle layer400, a mixture of ultraviolet-curable oligomers and monomers may be mixed with the suspended particle layer400and photo-cured to form a polymer matrix around the suspended particles420. If the first electric field is not applied to the suspended particle layer400, the suspended particles420dispersed in the dispersion410may be randomly positioned due to the Brownian motion. Light incident on the suspended particle layer400may be absorbed or reflected depending on the concentration, characteristics, and SPD structure of the suspended particles420. If the first electric field is not applied, the suspended particle layer400may be opaque or translucent.

If the first electric field is applied to the suspended particle layer400, the suspended particles420may be arranged in the direction of the first electric field, so that the incident light may pass through the suspended particle layer400. In other words, the suspended particle layer400is switched to a transparent state.

The polymer dispersed liquid crystal layer500may further include a polymer layer530and liquid crystals520dispersed in the polymer layer530. The polymer layer530may include a photoinitiator, an ultraviolet-curable polymer precursor, and a dispersant. The polymer dispersed liquid crystal layer500may contain approximately 80 parts by weight to approximately 120 parts by weight of the liquid crystals based on 100 parts by weight of a curable polymer. In order to improve the curing rate by an exposure machine during ultraviolet curing, an ultraviolet-curable polymer composition may be mixed with one or more types of photoinitiators and applied. The weight of the photoinitiator may be approximately 0.5 parts by weight to 10 parts by weight based on 100 weights of the cured polymer. For the ultraviolet curing according to the present invention, light with a wavelength of approximately 250 nm to approximately 400 nm may be used, and photocuring energy of approximately 50 mJ to approximately 2000 mJ may be used.

The liquid crystals520may have a thin and long rod shape. If the second electric field is applied to the polymer dispersed liquid crystal layer500, the molecular arrangement changes in the direction of the electric field. Typically, there are no restrictions on the characteristics of the liquid crystals, but as an example, the liquid crystals according to the present invention may have a flow viscosity (mm2/s) of approximately 15 to approximately 100, a refractive index anisotropy of approximately 0.10 to approximately 0.30, and a dielectric anisotropy (1.0 kHz) of approximately +2.0 to approximately +50.0.

The dye510included in the polymer dispersed liquid crystal layer500may be prepared by mixing two or more dyes having a chemical structure with excellent miscibility with a polymer and liquid crystals. For example, a mixture of a yellow dye and a red dye may be used to impart the second color (e.g., an orange color) to the polymer dispersed liquid crystal layer500. The concentration of the dyes included in the polymer dispersed liquid crystal layer500may be approximately 0.01 wt % to approximately 10 wt % based on the weight of liquid crystals.

The yellow dye may have a structure of [Formula 1] below.

In Formula 1 above, R1may be —N(CH3)2, —N(C2H5)2, or —N(X)2. The X may be an alkyl chain having 3 or more carbon atoms, and in Formula 1 above, R2may be —H, —CH3, —C2H5, a linear alkyl group having 3 or more carbon atoms, a branched alkyl group having 3 or more carbon atoms, a linear alkene having 3 or more carbon atoms, a branched alkene having 3 or more carbon atoms, or one or more aromatic groups.

The red dye may have a structure of [Formula 2] or a structure of [Formula 3] below.

In Formula 2 above, R7may be one among Cr, Mo, W, Mn, V, Nb, and Ta, and R8R9R10, and R11may each independently be —NO2, —NH3, —NHCH3, —NC4H10, —NC2H6, —N(an alkyl chain having 3 or more carbon atoms), or one or more aromatic groups.

In Formula 3 above, R12may be either —SO3Na or —SO3H, R13may be either —COOH or —COONa, R14and R15may each independently be —H, —CH3, —C2H5, or one among an alkyl group having 3 or more carbon atoms, a branched alkyl group having 3 or more carbon atoms, a linear alkene having 3 or more carbon atoms, a branched alkene having 3 or more carbon atoms, —NC4H10, —NC2H6, —NHCH3, —NH2, —N (an alkyl chain having 3 or more carbon atoms), and one or more aromatic group, and R16may be one among —H, —OH, —SO3H, and —COOH.

FIG.2toFIG.5show the operation state of a window film depending on the application of the first electric field and the second electric field.

FIG.2illustrates a state in which the first electric field is applied through the first control unit10, and the second electric field is also applied through the second control unit20. Since the first electric field is applied, the suspended particles420are arranged in the direction of the electric field, so that the suspended particle layer400may become transparent. Since the second electric field is applied, molecules of the liquid crystal520are arranged in the direction of the electric field, so that the polymer dispersed liquid crystal layer500may become transparent. Incident light1incident on the first film100may pass through the suspended particle layer400. The incident light2that has passed through the suspended particle layer400may pass through the polymer dispersed liquid crystal layer500. That is, the window film600becomes transparent.

FIG.3illustrates a state in which the first electric field is applied through the first control unit10, and the second electric field is not applied through the second control unit20. Since the first electric field is applied, the suspended particles420are arranged in the direction of the electric field, so that the suspended particle layer400may become transparent. Since the second electric field is not applied, the liquid crystal molecules520are arranged randomly, so that the polymer dispersed liquid crystal layer500may become opaque or translucent. Finally, the window film600may become opaque or translucent in the second color.

FIG.4illustrates a state in which the first electric field is not applied through the first control unit10, and the second electric field is applied through the second control unit20. Since the first electric field is not applied, the suspended particles420are arranged randomly, so that the suspended particle layer400may become opaque or translucent. Since the second electric field is applied, molecules of the liquid crystal520are arranged in the direction of the electric field, so that the polymer dispersed liquid crystal layer500may become transparent. Finally, the window film600may become opaque or translucent in the first color.

FIG.5illustrates a state in which the first electric field is not applied through the first control unit10, and the second electric field is also not applied through the second control unit20. Since the first electric field is not applied, the suspended particles420are arranged randomly, so that the suspended particle layer400may become opaque or translucent. Since the second electric field is not applied, the liquid crystal molecules520are arranged randomly, so that the polymer dispersed liquid crystal layer500may become opaque or translucent. Finally, the window film600may become opaque or translucent in a black color, as a result of the mixture of the first color and the second color, which are complementary colors.

According to the present invention, a window film includes a polymer liquid crystal layer containing a dye having a second color complementary to a first color of a suspended particle layer, and thus, may be operated in an opaque or translucent state in a black color in the absence of an electric field.

According to the present invention, depending on the application of a first electric field and a second electric field, the window film may be operated in four different colors of an opaque or translucent state in a black color, an opaque or translucent state in a first color, an opaque or translucent state in a second color, and a transparent state.

Although the present invention has been described in detail with reference to preferred embodiments, the present invention is not limited to the above-described embodiments, and various modifications and changes may be made by those skilled in the art within the technical spirit and scope of the present invention.