WO2018117721A1

WO2018117721A1 - Variable reflectivity mirror

Info

Publication number: WO2018117721A1
Application number: PCT/KR2017/015309
Authority: WO
Inventors: 임은정; 김진홍; 오동현; 유정선; 이현준; 김남훈
Original assignee: 주식회사 엘지화학
Priority date: 2016-12-23
Filing date: 2017-12-22
Publication date: 2018-06-28

Abstract

The present application relates to a variable reflectivity mirror using a liquid crystal cell. The variable reflectivity mirror of the present application may sequentially comprise: a first liquid crystal cell including a guest-host liquid crystal layer; a first reflective polarizing film; a second liquid crystal cell including a liquid crystal layer having variable phase contrast; a second reflective polarizing film; and an absorbing plate. The variable reflectivity mirror of the present application lowers its reflectivity in an anti-reflection mode thereby implementing an excellent variable reflectivity characteristic.

Description

Reflective Variable Mirror

The present application relates to a reflectance variable mirror.

This application claims the benefit of priority based on Korean Patent Application No. 10-2016-0177578 dated December 23, 2016 and Korean Patent Application No. 10-2017-0177678 dated December 22, 2017. All content disclosed in the literature is included as part of this specification.

The reflectance variable mirror refers to a mirror manufactured to adjust the reflectance of incident light, and may be referred to as a smart mirror. Due to the disadvantage of the slow response speed of the conventional electrochromic variable reflectivity mirror, the need for an alternative method has emerged (Patent Document 1: Korean Patent Publication No. 2004-0098051).

As an alternative to the electrochromic variable reflectance mirror, a guest host liquid crystal cell, a quarter wave plate, and a mirror may be applied. However, a problem with lower reflectance variable characteristics is lower than that of the conventional electrochromic variable reflectance mirror. have.

An object of the present application is to provide a variable reflectance mirror having excellent reflectivity variable characteristics using a liquid crystal cell.

The present application relates to a reflectance variable mirror. The variable reflectivity mirror may sequentially include a first liquid crystal cell including a guest host liquid crystal layer, a first reflective polarizing film, a second liquid crystal cell including a phase difference variable layer, a second reflective polarizing film, and an absorption plate. have. Hereinafter, the first liquid crystal cell may be referred to as a guest host liquid crystal cell, and the second liquid crystal cell may be referred to as a phase difference variable liquid crystal cell.

In defining an angle herein, when specifying an angle, or using terms such as vertical, parallel, orthogonal, or horizontal, this means that a particular angle, or substantially vertical, parallel, in a range that does not impair the desired effect. , Orthogonal or horizontal, for example, includes an error in consideration of a manufacturing error or a variation. For example, each of the above cases may include an error within about ± 15 degrees, an error within about ± 10 degrees or an error within about ± 5 degrees.

The guest host liquid crystal layer may include a liquid crystal and an anisotropic dye. As used herein, the term "guesthost liquid crystal layer" refers to a functional layer in which anisotropic dyes are arranged together according to an arrangement of liquid crystals, and exhibit anisotropic light absorption characteristics with respect to the alignment direction of the anisotropic dye and the vertical direction of the alignment direction, respectively. can do. For example, anisotropic dye is a material whose light absorption rate varies depending on the polarization direction. When the absorption rate of light polarized in the long axis direction is large, it is called p-type dye. When the absorption rate of light polarized in the axial direction is large, it is called n-type dye. can do. In one example, when a p-type dye is used, the polarized light vibrating in the long axis direction of the dye is absorbed and the polarized light vibrating in the short axis direction of the dye is less absorbed and thus can be transmitted. Unless otherwise specified, the anisotropic dye is assumed to be a p-type dye.

The guest host liquid crystal layer may function as an active polarizer. As used herein, the term "active polarizer" may refer to a functional device capable of adjusting anisotropic light absorption according to application of external action. For example, since the arrangement of the liquid crystal and the anisotropic dye of the guest host liquid crystal layer may be controlled by application of an external action such as a magnetic field or an electric field, the guest host liquid crystal layer may control anisotropic light absorption according to the application of the external action. .

The guest host liquid crystal layer may switch between a vertical alignment state and a horizontal alignment state according to whether voltage is applied.

In the present specification, the vertical alignment state is a state in which the directors of the liquid crystal molecules are vertically arranged with respect to the plane of the liquid crystal layer, for example, 85 degrees to 90 degrees, 86 degrees to 90 degrees, 87 degrees to 90 degrees, and 88 degrees to 90 degrees. 89 to 90 degrees may refer to an arrangement state that preferably constitutes 90 degrees, the horizontal alignment state is a state in which the director of the liquid crystal molecules are arranged horizontally with respect to the plane of the liquid crystal layer, for example, 0 degrees to 5 degrees, 0 degrees to 4 degrees, 0 degrees to 3 degrees, 0 degrees to 2 degrees, 0 degrees to 1 degrees may mean an arrangement state of preferably 0 degrees. As used herein, the term "director of liquid crystal molecules" may mean a long axis when the liquid crystal molecules are rod-shaped, and may mean an axis in the normal direction of the disc plane when the liquid crystal molecules are discotic. .

When the guest host liquid crystal layer is in the vertical alignment state, the liquid crystal and the anisotropic dye are present in the vertically aligned state. When a non-polarized light source passes through the guest host liquid crystal layer in the vertical alignment state, polarization is not imparted to the light source. When the guest host liquid crystal layer is in a vertical alignment state, the reflectance variable mirror may implement a mirror mode.

When the guest host liquid crystal layer is in a horizontal alignment state, the liquid crystal and the anisotropic dye are present in the horizontal alignment state. When the unpolarized light source passes through the horizontally aligned guest host liquid crystal layer, the vibration component parallel to the absorption axis of the anisotropic dye is absorbed, and the vibration component orthogonal to the absorption axis of the anisotropic dye is transmitted, thereby polarizing the light source. Can be given. When the guest host liquid crystal layer is in a horizontal alignment state, the reflectance variable mirror may implement an anti-reflection mode.

In one example, the guest host liquid crystal layer may be present in a vertical alignment state in a voltage-free state. The guest host liquid crystal layer may exist in a horizontal alignment state when a voltage is applied. Such an alignment state may be suitable when the first liquid crystal cell is implemented as a VA mode guest host liquid crystal cell.

The type and physical properties of the liquid crystal may be appropriately selected in consideration of the driving mode of the first liquid crystal cell.

In one example, the liquid crystal of the guest host liquid crystal layer may be a nematic liquid crystal or a smectic liquid crystal. Nematic liquid crystals may refer to liquid crystals in which rod-shaped liquid crystal molecules have no regularity of position but are arranged in parallel in the long axis direction of the liquid crystal molecules. It may mean a liquid crystal that is formed in a parallel structure with regularity in the long axis direction.

The liquid crystal of the guest host liquid crystal layer may have positive or negative dielectric anisotropy. As used herein, the term "dielectric anisotropy (Δε)" may mean the difference (ε / /-ε ㅗ) of the horizontal dielectric constant (ε / /) and the vertical dielectric constant (ε ㅗ,) of the liquid crystal. As used herein, the term "horizontal dielectric constant (ε //)" refers to a dielectric constant value measured along the direction of the electric field in a state where a voltage is applied such that the direction of the electric field due to the director of the liquid crystal molecules and the applied voltage is substantially horizontal. In addition, "vertical dielectric constant (ε ㅗ)" means a dielectric constant value measured along the direction of the electric field in the state where a voltage is applied so that the direction of the electric field by the director of the liquid crystal molecules and the applied voltage is substantially perpendicular.

In one example, when the guest host liquid crystal layer is driven in ECB mode, a liquid crystal having a positive dielectric anisotropy may be used. As another example, when the guest host liquid crystal layer is driven in VA mode, a liquid crystal having a negative dielectric anisotropy may be used.

In one example, the dielectric anisotropy of the liquid crystal of the guest host liquid crystal layer may be -20 to 20. When the dielectric anisotropy of the liquid crystal of the guest host liquid crystal layer satisfies the above range, it may be advantageous to implement a reflectance variable mirror having a high response speed and excellent reflectance variable characteristics.

As used herein, the term "dye" may mean a material capable of intensively absorbing and / or modifying light in at least part or the entire range within the visible light region, for example, in the 400 nm to 700 nm wavelength range, The term "anisotropic dye" may refer to a material capable of anisotropic absorption of light in at least part or the entire range of the visible light region.

As the anisotropic dye, for example, a known dye known to have a property that can be aligned according to the alignment state of the liquid crystal can be selected and used. As the anisotropic dye, for example, a black dye can be used. Such dyes are known, for example, but not limited to azo dyes, anthraquinone dyes, and the like.

The dichroic ratio of the anisotropic dye may be, for example, 5 or more, 6 or more or 7 or more. In the present specification, the term “dichroic ratio”, for example, in the case of a p-type dye, may mean a value obtained by dividing the absorption of polarized light parallel to the long axis direction of the dye by the absorption of polarized light parallel to the direction perpendicular to the long axis direction. Can be. Anisotropic dyes may satisfy the dichroic ratio at at least some of the wavelengths or at any one within the wavelength range of the visible region, for example, in the wavelength range of about 380 nm to 700 nm or about 400 nm to 700 nm. The upper limit of the dichroic ratio may be, for example, about 20 or less, 18 or less, 16 or less, or about 14 or less. When the dichroic ratio of the anisotropic dye satisfies the above range, it may be advantageous to implement a reflectance variable mirror having excellent reflectivity variable characteristics.

The content of the anisotropic dye of the guest host liquid crystal layer may be appropriately selected in consideration of the purpose of the present application. For example, the content of the anisotropic dye of the guest host liquid crystal layer may be 0.1 wt% or more, 0.25 wt% or more, 0.5 wt% or more, 0.75 wt% or more, 1 wt% or more, 1.25 wt% or more or 1.5 wt% or more. . The upper limit of the content of the anisotropic dye of the guest host liquid crystal layer is, for example, less than 3.0 wt%, 2.75 wt% or less, 2.5 wt% or less, 2.25 wt% or less, 2.0 wt% or less, 1.75 wt% or less, or 1.5 wt% It may be: When the content of the anisotropic dye of the guest host liquid crystal layer satisfies the above range, it may be advantageous to implement a reflectance variable mirror having excellent reflectivity variable characteristics.

The thickness of the guest host liquid crystal layer may be appropriately selected in consideration of the purpose of the present application. The thickness of the guest host liquid crystal layer may be, for example, about 3 μm to 20 μm or 3 μm to 15 μm. When the thickness of the guest host liquid crystal layer satisfies the above range, it may be advantageous to provide a mirror device having excellent reflectivity variable characteristics.

3 exemplarily shows a structure of a reflectance variable mirror of the present application.

As shown in FIG. 3, the first liquid crystal cell may further include an alignment layer. The alignment layer may be disposed to be adjacent to the guest host liquid crystal layer. In one example, the first liquid crystal cell may include two alignment layers (hereinafter, referred to as first and

second alignment layers

11A and 11B of FIG. 3) disposed on both surfaces of the guest host liquid crystal layer.

The first and second alignment layers may have an orientation force capable of controlling alignment of the initial state of the liquid crystal and the anisotropic dye. In the present specification, the initial state may mean a state in which an external voltage is not applied.

The alignment state of the guest host liquid crystal layer to the retardation variable liquid crystal layer can be adjusted by pretilt of the alignment film. In the present specification, the pretilt may have an angle and a direction. The pretilt angle may be referred to as a polar angle, and the pretilt direction may be referred to as an azimuthal angle.

The pretilt angle may refer to an angle formed by the optical axis of the liquid crystal molecules with respect to the plane parallel to the alignment layer. The pretilt direction may refer to a direction in which the optical axis of the liquid crystal molecules is projected onto the horizontal surface of the alignment layer.

The first and second alignment layers may be horizontal alignment layers or vertical alignment layers, respectively. In one example, each of the first and second alignment layers may be a vertical alignment layer. In this case, the directors of the liquid crystal molecules may be arranged perpendicularly to the vertical alignment layer plane. In another example, each of the first and second alignment layers may be a horizontal alignment layer. In this case, the directors of the liquid crystal molecules may be arranged horizontally with respect to the alignment layer plane.

As the first and second alignment films, an alignment film known in the art having an alignment force with respect to liquid crystal molecules can be appropriately selected and used. As the alignment layer, for example, a photoalignment layer capable of exhibiting alignment characteristics by a non-contact method such as irradiation of linearly polarized light including a contact alignment layer or a photoalignment layer compound such as a rubbing alignment layer may be used.

As shown in FIG. 3, the first liquid crystal cell may further include a transparent electrode substrate. The transparent electrode substrate may include a substrate layer and a transparent electrode layer on the substrate layer. The electrode layer may take over an electric field suitable for the guest host liquid crystal layer to switch the alignment state of the liquid crystal and the anisotropic dye. In one example, the first liquid crystal cell refers to two transparent electrode substrates (hereinafter, referred to as first and second transparent electrode substrates (12A and 12B in FIG. 3)) disposed opposite to both sides of the guest host liquid crystal layer. It may include. When the first liquid crystal cell includes the first and second alignment layers, the first and second transparent electrode substrates may be disposed adjacent to opposite sides of the guest host liquid crystal layers of the first and second alignment layers, respectively.

The electrode layer may be a transparent electrode layer. As the transparent electrode layer, for example, a conductive polymer, a conductive metal, a conductive nanowire, or a metal oxide such as ITO (Indium Tin Oxide) may be used by evaporation. In addition, various materials and forming methods capable of forming transparent electrodes are known, and the present invention may be applied without limitation.

As the substrate layer, a transparent substrate layer can be used. For example, an inorganic film, a plastic film, etc., such as a glass substrate, a crystalline or amorphous silicon film, a quartz, or an Indium Tin Oxide (ITO) film, can be used as a base material layer. As the substrate layer, an optically anisotropic substrate such as an optically isotropic substrate or a retardation layer can be used.

Specific examples of the plastic film include triacetyl cellulose (TAC); COP (cyclo olefin copolymer) such as norbornene derivatives; Poly (methyl methacrylate); PC (polycarbonate); PE (polyethylene); PP (polypropylene); PVA (polyvinyl alcohol); DAC (diacetyl cellulose); Pac (Polyacrylate); PES (poly ether sulfone); PEEK (polyetheretherketon Films including polyphenylsulfone (PPS), polyetherimide (PEI); polyethylenemaphthatlate (PEN); polyethyleneterephtalate (PET); polyimide (PI); polysulfone (PSF); polyarylate (PAR) or amorphous fluorine resin, etc. It is not limited to this.

In the present specification, the reflective polarizing film may have selective transmission and reflection characteristics with respect to incident light. For example, the reflective polarizing film may have a property of transmitting one of the transverse and longitudinal wave components of light and reflecting the other component. When light is incident on the reflective polarizing film, the light passing through the reflective polarizing film and the light reflected from the reflective polarizing film may have polarization characteristics. In one example, the polarization direction of the transmitted light and the polarization direction of the reflected light may be orthogonal to each other. That is, the reflective polarizing film may have a transmission axis and a reflection axis orthogonal to the plane direction. Reflective polarizing film has a characteristic that most of the transmissive and longitudinal components of the light transmits most of the components and reflects most of the other components, it can be implemented in the form of a half mirror (Half Mirror). As the reflective polarizing film, for example, DBEF (Dual Brightness Enhancement Film) may be used. Matters for the reflective polarizing film may be applied to the first and second reflective polarizing films described later.

The first reflective polarizing film may be disposed below the first liquid crystal layer. The first reflective polarizing film may have a first reflection axis formed in one direction. The first reflection axis may be parallel to the absorption axis direction of the anisotropic dye in the horizontal alignment of the guest host liquid crystal layer. The first reflective polarizing film may have a first transmission axis perpendicular to the first reflection axis. The first reflection axis and the first transmission axis may be formed in a horizontal direction (plane direction).

The second liquid crystal cell may be disposed below the first reflective polarizing film. The second liquid crystal cell may include a phase difference variable liquid crystal layer for switching between a phase difference mode and a non-phase difference mode. The phase difference variable liquid crystal layer may include a liquid crystal. The type and physical properties of the liquid crystal may be appropriately selected in consideration of the driving mode of the second liquid crystal cell.

The phase difference variable liquid crystal layer may switch a phase difference mode and a non-phase difference mode according to whether voltage is applied.

When the retardation variable liquid crystal layer is in retardation mode, the retardation variable may have a phase delay characteristic with respect to incident light. The retardation variable liquid crystal layer has a vibration direction of the linearly polarized light incident in the retardation mode of 80 degrees to 100 degrees, 82 degrees to 98 degrees, 84 degrees to 96 degrees, 86 degrees to 94 degrees, 88 degrees to 92 degrees, preferably It may have a phase delay characteristic of rotating 90 degrees. When the retardation variable liquid crystal layer is in retardation mode, the reflectance variable mirror may implement a mirror mode.

When the phase difference variable liquid crystal layer is in the non-phase difference mode, it may mean a mode that does not have a phase delay characteristic with respect to incident light. The phase difference variable liquid crystal layer does not change the vibration direction of linearly polarized light incident in the non-phase difference mode. When the retardation variable liquid crystal layer is in retardation mode, the reflectance variable mirror may implement an antireflection mode.

In one example, the phase difference variable liquid crystal layer may implement a phase difference mode in a voltage-free state, and may implement a non-phase difference mode in a voltage applied state. Such an alignment state may be suitable when the second liquid crystal cell is implemented as a 90 degree TN liquid crystal cell.

The second liquid crystal cell may be driven in an appropriate mode to switch between the phase difference mode and the non-phase difference mode. The second liquid crystal cell may be embodied in a liquid crystal based mode in which a phase difference variable characteristic plays the same role as a half wave plate, or may be implemented as a stacked element of a liquid crystal based mode and a compensation film. In one example, the second liquid crystal cell may be a 90 degree TN mode liquid crystal cell, a 270 degree STN mode liquid crystal cell, an ECB mode liquid crystal cell or a laminate of a half wave plate and a VA mode liquid crystal cell.

In the twisted nematic (TN) mode liquid crystal cell, liquid crystal molecules in the liquid crystal layer may exist in a twisted alignment state at a twist angle of 90 degrees or less in a voltage-free state, and may exist in a vertical alignment state in a voltage application state. A 90 degree TN liquid crystal cell may mean a TN liquid crystal cell having a twist angle of 90 degrees.

In the STN (Super twisted nematic) mode liquid crystal cell, the liquid crystal molecules in the liquid crystal layer may exist in a twisted alignment state at a twist angle of more than 90 degrees in a voltage-free state, and may exist in a vertical alignment state in a voltage application state. A 270 degree STN liquid crystal cell may refer to an STN liquid crystal cell having a twist angle of 270 degrees.

In the ECB (Electrically Controllable Birefringence) mode liquid crystal cell, the liquid crystal molecules in the liquid crystal layer may exist in a horizontal alignment state in a voltage-free state, and may exist in a vertical alignment state in a voltage application state.

In the VA (Vertical Alignment) mode liquid crystal cell, liquid crystal molecules in the liquid crystal layer may exist in a vertical alignment state in a voltage-free state, and may exist in a horizontal alignment state in a voltage application state.

The twist angle refers to an angle formed between the optical axis of the liquid crystal molecules at the bottom and the optical axis of the liquid crystal molecules at the top of the twisted alignment liquid crystal layer. The application of the voltage may be applied in a direction perpendicular to the surfaces of the third and fourth transparent electrode substrates.

The thickness of the phase difference variable liquid crystal layer may be appropriately selected in consideration of the purpose of the present application. The thickness of the phase difference variable liquid crystal layer may be, for example, about 3 μm to 20 μm or 3 μm to 15 μm. When the thickness of the phase difference variable liquid crystal layer satisfies the above range, it may be advantageous to provide a mirror element having excellent reflectance variable characteristics.

The second liquid crystal cell may further include an alignment layer. In one example, the second liquid crystal cell may further include third and fourth alignment layers (31A and 31B of FIG. 3) disposed opposite to both sides of the phase difference variable liquid crystal layer. For the third and fourth alignment layers, the contents described in the items of the first and second alignment layers may be applied in the same manner, and an alignment layer suitable for the driving mode of the second liquid crystal cell may be applied.

In one example, when the second liquid crystal cell is a 90-degree TN liquid crystal cell or a 270 STN liquid crystal cell, the pretilt direction of the third alignment layer disposed closer to the first reflective polarizing film among the third and fourth alignment layers may include The reflection axis of the first reflective polarizing film may be orthogonal to each other, and the pretilt direction of the fourth alignment layer may be parallel to the reflection axis of the first reflective polarizing film.

In another example, when the second liquid crystal cell is an ECB mode liquid crystal cell, the pretilt direction of the third and fourth alignment layers may be about 45 degrees with the reflection axis of the first reflective polarizing film.

In another example, when the second liquid crystal cell is a laminate of a half wave plate and a VA mode liquid crystal cell, the slow axis of the half wave plate and the reflection axis of the first reflective polarizing film are about 45 degrees. In this case, the slow axis of the 1/2 wave plate and the direction of the horizontal alignment of the VA mode liquid crystal cell (the pretilt direction of the alignment layer of the VA mode liquid crystal cell) may be about 45 degrees. In this case, the mirror mode may be implemented in the non-voltage applied state to the VA liquid crystal cell, and the anti-reflection mode may be implemented in the voltage applied state.

The second liquid crystal cell may further include a transparent electrode substrate. In one example, the second liquid crystal cell may further include third and fourth transparent electrode substrates (32A and 32B of FIG. 3) on both sides of the phase difference variable liquid crystal layer. For the third and fourth transparent electrode substrates, the contents described in the items of the first and second transparent electrode substrates may be applied in the same manner, and a transparent electrode substrate suitable for the driving mode of the second liquid crystal cell may be applied.

The second reflective polarizing film may be disposed below the second liquid crystal cell. The second reflective polarizing film may have a second reflection axis formed in a direction parallel to the first reflection axis. The second reflective polarizing film may have a second transmission axis perpendicular to the second reflection axis. The second reflection axis and the second transmission axis may be formed in a horizontal direction (plane direction). The second reflection axis may be parallel to the vibration direction of linearly polarized light passing through the phase difference mode of the phase variable variable liquid crystal layer of the second liquid crystal cell.

The absorbing plate may be disposed below the second reflective polarizing film. The absorbing plate may play a role of absorbing and extinguishing afterglow transmitted through the first liquid crystal cell, the first reflective polarizing film, the second liquid crystal cell, and the second reflective polarizing film. The absorbing plate may include a known light absorbing material. The light absorbing material may include, for example, a black inorganic pigment such as carbon black ink, graphite or iron oxide, or an ink including black organic pigment ink such as azo pigment or phthalocyanine pigment. Can be mentioned.

The light absorption rate of the absorber may be about 90% or more, 95% or more, or 98% or more. The light absorption may refer to light absorption for visible light, for example, light having a wavelength of about 380 nm to 780 nm. The light absorptance means light absorption in one wavelength or a predetermined wavelength band of the wavelength band of 380 nm to 780 nm, or means light absorption in all wavelengths of the wavelength band, or the average light absorption in the wavelength band. It may mean.

The variable reflectivity mirror may switch between a mirror mode and an anti-reflection mode depending on whether a voltage is applied. In the present specification, the mirror mode may mean a mode in which the front light reflectance is about 50% or more, and the antireflection mode may mean a mode in which the front light transmittance is about 10% or less.

1 and 2 illustrate the principle of implementing the mirror mode and the anti-reflection mode of the reflectivity variable mirror when the first liquid crystal cell is a guest host liquid crystal cell in VA mode and the second liquid crystal cell is a 90 degree TN mode liquid crystal cell, respectively. Indicated by As exemplarily shown in FIGS. 1 and 2, the variable reflectance mirror includes a guest host liquid crystal layer 10 including a liquid crystal 101 and an anisotropic dye 102, and a first reflection having a first reflection axis R1. A polarizing film 20, a phase difference variable liquid crystal layer 30 including a liquid crystal 301, a second reflective polarizing film 40 having a second reflection axis R2, and an absorbing plate 50. can do.

Solid lines in FIGS. 1 and 2

Means unpolarized light, dotted line

Means 0 degree vibration component

Means 90 degree vibration component.

The exemplary reflectance variable mirror may implement a mirror mode in a state where no voltage is applied to each of the first liquid crystal cell and the second liquid crystal cell. Hereinafter, an optical path when implementing the mirror mode of FIG. 1 will be described. Assume that the reflection axes of the first and second reflective polarizing films are each 0 degrees.

① The guest host liquid crystal cell in VA mode exists in a vertical alignment state without a voltage applied state. The non-polarized light source incident on the vertically aligned guest host liquid crystal layer is partially absorbed by the guest host liquid crystal layer and maintains an unpolarized state while passing through the guest host liquid crystal layer. ② The zero-degree vibration light source oscillating in parallel with the first reflection axis 0 degrees of the first reflection type polarizing film among the light transmitted through the guest host liquid crystal layer is reflected by the first reflection type polarizing film and through the guest host liquid crystal layer. Outgoing. ③ The 90 degree vibration light source and some 0 degree vibration light source orthogonal to the 1st reflection axis of a 1st reflective polarizing film among the light which passed the said guest host liquid crystal layer permeate | transmit a 1st reflective polarizing film. ④ The light transmitted through the first reflective polarizing film passes through the phase variable variable liquid crystal layer of the TN mode liquid crystal cell and is delayed by 90 degrees. That is, the 90 degree vibration light source is changed into a 0 degree vibration light source component through the phase difference variable liquid crystal layer. ⑤ In the above ④, the 0 degree vibration light source is reflected because it is a light source component parallel to the second reflection axis of the second reflective polarizing film. ⑥ The zero degree vibration light source reflected by ⑤ is changed through the phase difference variable liquid crystal layer through a phase difference variable liquid crystal layer by 90 degrees and is converted into a 90 degree vibration light source. Since the transmission axis of the first reflective polarizing film is 90 degrees, all of the 90 degree vibration light sources expressed in 6 are transmitted through the first reflective polarizing film. Therefore, most of 0 degree and 90 degree polarization components of an incident light source can be extracted as a reflection light source.

The exemplary reflectance variable mirror may implement an anti-reflection mode in a voltage applied state to each of the first liquid crystal cell and the second liquid crystal cell. Hereinafter, an optical path when the anti-reflective mode of FIG. 2 is implemented will be described. Assume that the reflection axes of the first and second reflective polarizing films are each 0 degrees.

(1) The guest host liquid crystal cell in VA mode exists in a horizontal alignment state in a voltage application state. Assume that the absorption axis of the anisotropic dye in the horizontal alignment is 0 degrees. The non-polarized light source incident on the vertically oriented guest host liquid crystal layer is absorbed by the 0 degree vibration component while passing through the horizontally oriented guest host liquid crystal layer having the absorption axis of the anisotropic dye at 0 degrees to generate polarized light of the 90 degree vibration component. ② The zero degree vibration light source oscillating parallel to the first reflection axis 0 degrees of the first reflective polarizing film of the partially polarized light source passing through the guest host liquid crystal layer is reflected, and further absorption is absorbed while passing through the guest host liquid crystal layer. Generated and emitted. ③ The 90 degree vibration light and the 0 degree vibration light source orthogonal to the 1st reflection axis of a 1st reflection type polarizing film among the some polarized light sources which passed the said guest host liquid crystal layer permeate | transmit a 1st reflection type polarizing film. ④ The TN mode liquid crystal cell is in a vertically oriented state in a voltage application state. Therefore, since the phase difference variable liquid crystal layer does not have a phase delay characteristic, the light passing through the first reflective polarizing film passes through the phase difference variable liquid crystal layer as it is. That is, the 90 degree vibration light source is maintained as a 90 degree vibration light source component. ⑤ In the above ④, the 90-degree vibration light source is a light source component parallel to the second transmission axis of the second reflective polarizing film, and thus is transmitted as it is and is absorbed and disappeared by the absorption plate. ⑥ The 0 degree and 90 degree vibration light sources partially reflected by ⑤ pass through the phase difference variable liquid crystal layer. ⑦ Since the transmission axis of the first reflective polarizing film is 90 degrees, the absorbing light is generated by the uniaxial absorption of the guest host liquid crystal layer among the remaining light sources of ⑥, and the 90 degree vibration light source is the first reflective polarizing film. Additional reflection and partial light emission, but additional absorption occurs because it is parallel to the absorption axis of the long axis of the guest host liquid crystal layer. Therefore, the reflection of 0 degree and 90 degree polarization components of the incident light source can be prevented.

The reflectance variable mirror of the present application may implement a reflectance of 10% or less in the anti-reflection mode according to the implementation principle of the mirror mode and the anti-reflection mode. Accordingly, the reflectance variable mirror may have excellent reflectance variable characteristics. For example, the difference in reflectance between the mirror mode and the anti-reflective mode of the variable reflectivity mirror may be 50% or more. In addition, the reflectance variable mirror of the present application has the advantage that the response speed is fast because it is based on the liquid crystal cell.

The variable reflectance mirror of the present application can be applied to various optical elements that require application of the variable reflectance mirror. Other components, structures, and the like are not particularly limited as long as they include the variable reflectivity mirror, and all contents known in the art may be appropriately applied. However, the reflectance variable mirror of the present application may not include an image display panel. That is, the reflectance variable mirror of the present application is not an image display device.

The variable reflectivity mirror of the present application can implement excellent reflectivity variable characteristics by lowering the reflectance in the anti-reflection mode.

1 exemplarily illustrates an implementation principle of a mirror mode of a reflectance variable mirror of the present application.

2 exemplarily illustrates an implementation principle of an anti-reflective mode of a reflectance variable mirror of the present application.

3 exemplarily shows a reflectance variable mirror of Embodiment 1. FIG.

4 exemplarily shows a reflectance variable mirror of Comparative Example 1. FIG.

[Description of the code]

DESCRIPTION OF SYMBOLS 10 Guest host liquid crystal layer 101 Liquid crystal 102

Anisotropic dye

11A and 11B 1st and 2nd oriented

films

12A and 12B The 1st and 2nd transparent electrode base material 20 The 1st reflective polarizing film 30 Retardation variable liquid crystal layer 301:

liquid crystals

31A and 31B: third and fourth alignment films, 32A and 32B: third and fourth transparent electrode substrates 40: second reflective polarizing film 50: absorber plate 60: guest host liquid crystal layer 601: liquid crystal 602:

anisotropic Dye

61A, 61B:

alignment layer

62A, 62B: transparent electrode layer 63: base layer 70: 1/4 wave plate 80: mirror R1: reflection axis of first reflective polarizing film R2: reflection axis of second reflective polarizing film a : Absorption axis o of guest host liquid crystal layer 60: Optical axis of quarter wave plate 70

Hereinafter, the reflectivity variable mirror of the present application will be described in detail with reference to the following examples, but the scope of the present application is not limited by the following contents.

제조예 1 VA 모드 GHLC셀의 제조 Preparation Example 1 Preparation of VA Mode GHLC Cell

Two cell substrates each having an ITO electrode layer and a vertical alignment layer sequentially formed on a polycarbonate film (width × length = 15cm × 5cm) face each other and are spaced apart so that the cell gap is 8 μm, and the liquid crystal therebetween. VA mode GHLC cells were prepared by injecting the composition and sealing the edges. The liquid crystal composition comprises a nematic liquid crystal (HNG7306 from HCCH, dielectric anisotropy: -5.0) and an anisotropic dye (X12 from BASF), wherein the content of the anisotropic dye is 1.4% by weight.

제조예 2 VA 모드 GHLC셀의 제조 Preparation Example 2 Preparation of VA Mode GHLC Cell

Two cell substrates each having an ITO electrode layer and a vertical alignment layer sequentially formed on a polycarbonate film (width × length = 15cm × 5cm) face each other and are spaced apart so that the cell gap is 8 μm, and the liquid crystal therebetween. VA mode GHLC cells were prepared by injecting the composition and sealing the edges. The liquid crystal composition comprises a nematic liquid crystal (HNG7306 from HCCH, dielectric anisotropy: -5.0) and an anisotropic dye (X12 from BASF), wherein the content of the anisotropic dye is 1.0% by weight.

제조예 3. ECB 모드 GHLC셀의 제조 Preparation Example 3 Preparation of ECB Mode GHLC Cells

After the glass substrates (horizontal x vertical = 15 cm x 5 cm) are arranged so that the alignment directions of the horizontal alignment films facing two cell substrates in which the ITO electrode layer and the horizontal alignment film are sequentially formed are parallel, and the cell gap is 11 µm, The liquid crystal composition was injected in between and the edges were sealed to prepare an ECB mode GHLC cell. The liquid crystal composition comprises a nematic liquid crystal (HPC2160 from HCCH, dielectric anisotropy: 18.2) and an anisotropic dye (X12 from BASF), wherein the content of the anisotropic dye is 1.5% by weight.

제조예 4 VA 모드 GHLC셀의 제조 Preparation Example 4 Preparation of VA Mode GHLC Cell

The two cell substrates on which the ITO electrode layer and the vertical alignment layer were sequentially formed on the polycarbonate film (width × length = 15cm × 5cm) face each other and are spaced apart so that the cell gap is 12 μm, and the liquid crystal therebetween. VA mode GHLC cells were prepared by injecting the composition and sealing the edges. The liquid crystal composition comprises a nematic liquid crystal (HNG7306 from HCCH, dielectric anisotropy: -5.0) and an anisotropic dye (X12 from BASF), wherein the content of the anisotropic dye is 1.4% by weight.

제조예 5 TN 모드 액정셀의 제조 Preparation Example 5 Preparation of TN Mode Liquid Crystal Cell

On the polycarbonate film (width × length = 15cm × 5cm), the alignment direction of the horizontal alignment film facing two cell substrates in which the ITO electrode layer and the horizontal alignment film are sequentially formed is orthogonal, and the cell gaps are spaced apart so that the cell gap is 7 μm, In the meantime, the liquid crystal composition was injected and the edge was sealed to prepare a 90 degree TN mode GHLC cell. The liquid crystal composition includes a nematic liquid crystal (MAT-16-970 from Merck, dielectric anisotropy: 5.0) and a chiral agent (S811, HCC), and the content of the chiral agent is 0.08% by weight. The cell gap x Δn (refractive index anisotropy) of the prepared TN mode liquid crystal cell is about 480 nm.

실시예 1Example 1

Dual Brightness Enhancement Film (DBEF) having a reflectance of 52% for unpolarized incident light was prepared as the first and second reflective polarizing films, respectively. A black sheet (LG Chem) having an absorption rate of 98% or more was prepared as an absorbent plate.

The VA mode GHLC cell 10 of Preparation Example 1, the first reflective polarizing film 20, the TN mode liquid crystal cell 30 of Preparation Example 5, the second reflective polarizing film 40 and the light absorbing plate 50 were By sequentially stacking as shown in Figure 3 to produce a variable reflectance mirror. The reflection axis R1 of the first reflective polarizing film and the reflection axis R2 of the second reflective polarizing film were arranged in parallel. The reflection axis of the first reflection type polarizing film is parallel to the absorption axis direction when the GHLC cell is horizontally aligned, and the reflection axis of the second reflection type polarizing film is aligned with the alignment direction of the side of the second reflection type polarizing film of the TN mode liquid crystal cell. Placed to be orthogonal.

실시예 2Example 2

A variable reflectance mirror was produced in the same manner as in Example 1 except that the VA mode GHLC cell of Preparation Example 2 was used instead of the VA mode GHLC cell of Preparation Example 1.

비교예 1Comparative Example 1

An ECB mode GHLC cell 60 of manufacture example 3, a quarter wave plate 70, and a commercial mirror 80 having a reflectance of 90% were sequentially stacked as shown in FIG. 4 to fabricate a variable reflectance mirror. The absorption axis (a) in the horizontal alignment of the GHLC cell and the optical axis (o) of the quarter wave plate were arranged to form about 45 degrees.

비교예 2Comparative Example 2

A reflectance variable mirror was manufactured in the same manner as in Comparative Example 1 except that the VA mode GHLC cell of Preparation Example 4 was used instead of the ECB mode GHLC cell of Preparation Example 3.

비교예 3Comparative Example 3

In Example 2, a reflectance variable mirror was manufactured in a structure except for the first liquid crystal cell.

평가예 1. 반사율 가변 특성 평가 Evaluation Example 1. Reflectance Variable Characteristic Evaluation

The GHLC cells used in the manufacture of the variable reflectivity mirrors of Examples 1 to 2 and Comparative Examples 1 to 3 were measured according to the presence or absence of voltage applied thereto, and are shown in Table 1 below. The reflectances of Examples 1 to 2 and Comparative Examples 1 to 3 were measured according to the presence or absence of voltage, and are shown in Table 1 below.

The transmittance is the back light transmittance, and the reflectance is the front light reflectance. The front light is light incident on the reflecting variable mirror at the viewer side, and the back light is light incident on the reflectivity variable mirror on the opposite side of the viewer side, and the back light transmittance and the front light reflectance are measured values at the viewer side.

In Examples 1 to 2 and Comparative Examples 1 to 3, the viewer side is the GHLC cell side. The reflectance is a value measured for light having a wavelength of 380 nm to 780 nm in a SCI (specular component included) method using a CM-2600d manufactured by KONICA MINOLTA. The front light reflectance of Table 2 is a numerical value for the case where the total amount of incident light is 100%.

	GHLC Cell 단품 특성GHLC Cell
	0V 투과율(%)0V transmittance (%)	15V 투과율(%)15V transmittance (%)
제조예 1Preparation Example 1	71.571.5	4141
제조예 2Preparation Example 2	7777	4646
제조예 3Preparation Example 3	3535	58.658.6
제조예 4Preparation Example 4	5959	3333

	반사율 가변 미러 특성Reflective Variable Mirror Characteristics
	0V 반사율(%)0 V reflectance (%)	15V 반사율(%)15 V reflectance (%)	반사율 차이(%)Reflectance Difference (%)
실시예 1Example 1	57.757.7	3.53.5	54.254.2
실시예 2Example 2	6868	99	5959
비교예 1Comparative Example 1	1616	5555	3939
비교예 2Comparative Example 2	5555	12.512.5	42.542.5
비교예 3Comparative Example 3	91%91%	51%51%	4040

Claims

A first liquid crystal cell having a guest host liquid crystal layer comprising a liquid crystal and an anisotropic dye,

A first reflective polarizing film having a first reflection axis formed in one direction,

A second liquid crystal cell having a phase difference variable liquid crystal layer for switching a phase difference mode for rotating the vibration direction of linear polarization by 90 degrees and a non-phase difference mode.

A second reflective polarizing film having a second reflection axis parallel to the first reflection axis;

Reflective variable mirror containing the absorbing plate in sequence.
The method of claim 1,

The guest host liquid crystal layer is a variable reflectivity mirror to switch the vertical alignment state and the horizontal alignment state depending on the presence or absence of voltage.
The method of claim 1,

The first liquid crystal cell further includes a variable reflectivity mirror, the first and second alignment layer disposed on both sides of the guest host liquid crystal layer.
The method of claim 1,

The first liquid crystal cell further comprises a variable reflectivity mirror comprising a first and a second transparent electrode substrate disposed on both sides of the guest host liquid crystal layer.
The method of claim 1,

The first reflective polarizing film has a first transmission axis orthogonal to a first reflection axis, and the first reflection axis and the first transmission axis are formed in a horizontal direction.
The method of claim 1,

A first reflecting axis of the first reflective polarizing film is a reflectance variable mirror parallel to the absorption axis direction of the anisotropic dye in the horizontal alignment of the guest host liquid crystal layer,
The method of claim 1,

The phase difference variable liquid crystal layer is a variable reflectivity mirror to switch the phase difference mode and the non-phase difference mode according to the presence or absence of voltage applied.
The method of claim 1,

And the second liquid crystal cell further includes third and fourth alignment layers disposed on opposite sides of the phase difference variable liquid crystal layer.
The method of claim 1,

The second liquid crystal cell further includes a third and fourth transparent electrode substrates disposed opposite to both sides of the variable phase difference liquid crystal layer.
The method of claim 1,

The second liquid crystal cell is a variable reflectivity mirror of 90 degrees TN mode liquid crystal cell, 270 degrees STN mode liquid crystal cell, ECB mode liquid crystal cell, or a half wave plate and VA mode liquid crystal cell.
The method of claim 1,

The second reflective polarizing film has a second transmission axis orthogonal to a second reflection axis, and the second reflection axis and the second transmission axis are formed in a horizontal direction.
According to claim 1,

And a second reflecting axis of the second reflecting polarizing film is parallel to a vibration direction of linearly polarized light passing through the retardation mode of the retardation variable liquid crystal layer.
The method of claim 1,

The variable reflectance mirror implements a mirror mode when the first liquid crystal cell is in a vertical alignment state and the second liquid crystal cell is in a phase difference mode.
The method of claim 1,

The variable reflectivity mirror is a variable reflectivity mirror to implement an anti-reflection mode when the first liquid crystal cell is in a horizontal alignment state and the second liquid crystal cell is in a non-phase difference mode.
The method of claim 1,

And the reflectance variable mirror does not include an image display panel.