KR20220004384A - Light modulating device - Google Patents

Abstract

The application relates to an optical modulation device. The optical modulation device of the present application can drive the optical modulation device with a high transmittance variable level with a low driving voltage while implementing low transmittance. The optical modulation device includes a first substrate on which an adhesive layer or an adhesive layer is formed on a first surface; a liquid crystal layer comprising a liquid crystal compound and a chiral dopant; and a second substrate on which a vertical alignment layer is formed on the first surface.

Description

Light modulation device {LIGHT MODULATING DEVICE}

This application relates to an optical modulation device.

The optical modulation device refers to a device capable of switching between at least two or more different states. Such devices include, for example, eyewear such as glasses or sunglasses, a mobile device, a device for virtual reality (VR), a wearable device such as a device for augmented reality (AR), or Its use is gradually expanding, such as being used for sunroofs of vehicles.

Among the light modulation devices, a device using a guest host liquid crystal system mixes a dichroic dye as a guest molecule with respect to the host molecule of the liquid crystal layer, and changes the arrangement of the host molecule and the guest molecule by a voltage applied to the liquid crystal layer to form a liquid crystal layer can change the light absorptivity of

In such a guest-host liquid crystal system, a highly twisted nematic (HTN) liquid crystal driving mode may be applied to maximize the degree of transmittance variation while lowering the transmittance in the blocking mode state. However, since this type of liquid crystal system has a high driving voltage for switching between the blocking mode state and the transmission mode state, there is a limit to actually applying it to various display devices.

The present application provides an optical modulation device capable of switching between a cut-off mode state and a transmission mode state even with a low driving voltage and maximizing a variable transmittance level while implementing low transmittance.

This application relates to an optical modulation device. The term light modulation device may refer to a device capable of switching between two or more different states of light. In the above, different states of light may mean states in which at least transmittance, reflectance, color, and/or haze are different.

1 exemplarily shows an optical modulation device according to an embodiment of the present application. The light modulation device of the present application sequentially includes a first substrate, a liquid crystal layer, and a second substrate.

The first substrate 101 has an adhesive layer or an adhesive layer 103 formed on a first surface, the liquid crystal layer 300 includes a liquid crystal compound and a chiral dopant, and the second substrate 201 is a 1 A vertical alignment film is formed on the surface. The first substrate and the second substrate are disposed to face each other so that their first surfaces face each other, and a distance between the first substrate and the second substrate is maintained by the barrier rib spacer 400 . The optical modulation device of the present application switches between a twisted orientation state in which the twist angle (A) calculated by the following general formula (1) is 860 degrees or more and an orientation state different from the twist orientation state according to the application of voltage.

[General formula 1]

Twisting angle (A) = a+b×360

In Formula 1, a is the angle formed by the optical axis of the liquid crystal molecule present at the lowermost portion and the optical axis of the liquid crystal molecule present at the uppermost portion in the liquid crystal layer in the twist alignment state, and b is the number of pitches.

In the present specification, vertical, parallel, perpendicular, or horizontal among terms defining an angle means substantially vertical, parallel, orthogonal or horizontal in a range that does not impair the intended effect, and the range of vertical, parallel, orthogonal or horizontal is It includes errors such as manufacturing errors or variations. 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.

Among the physical properties mentioned in this specification, when the measured temperature affects the corresponding physical property, unless otherwise specified, the physical property is a physical property measured at room temperature.

As used herein, the term room temperature refers to a temperature in a state in which it is not particularly heated or reduced, and any one temperature within the range of about 10° C. to 30° C., for example, about 15° C. or more, 18° C. or more, 20° C. or more, or about 23° C. or more. , may mean a temperature of about 27 ℃ or less. In addition, unless otherwise specified, the unit of temperature referred to in the present specification is °C.

The optical modulation device of the present application may be designed to be able to switch between a transmissive mode state and a blocking mode state. The switching of the optical modulation device may be controlled according to application of an external signal, for example, whether a voltage signal is applied.

The light modulation device of the present application may include a structure including two substrates facing each other and a liquid crystal layer positioned between the substrates as a basic unit. Usually, a liquid crystal aligning film is formed on both surfaces of the first and second substrates, but by forming an adhesive layer or an adhesive layer instead of the liquid crystal aligning film on the first substrate and forming the liquid crystal aligning film only on the second substrate, a specific application (eg For example, the alignment state of the liquid crystal compound which is very useful in smart windows or eye wear) can be obtained. Accordingly, the liquid crystal alignment layer may not be formed on the first substrate of the light modulation device of the present application. In addition, a spacer for maintaining a cell gap between the first and second substrates is present on any one of the first and second substrates of the light modulation device, and an adhesive layer or an adhesive layer is formed on the first substrate In this case, the adhesive layer or the adhesive layer is attached to the spacer to greatly improve the bonding force of the first and second substrates.

In the present specification, the first surface of the substrate means any one of the main surface and the opposite surface of the substrate, and the second surface means the other surface of the main surface and the opposite surface of the substrate.

As the first substrate 101 and the second substrate 201 , a known substrate material may be used without particular limitation. For example, as the substrate, an inorganic substrate such as a glass substrate, a crystalline or amorphous silicon substrate, or a quartz substrate, or a plastic substrate can be used. Examples of the plastic substrate include a triacetyl cellulose (TAC) substrate; COP (cyclo olefin copolymer) substrates such as norbornene derivative substrates; PMMA(poly(methyl methacrylate) substrate; PC(polycarbonate) substrate; PE(polyethylene) substrate; PP(polypropylene) substrate; PVA(polyvinyl alcohol) substrate; DAC(diacetyl cellulose) substrate; Pac(Polyacrylate) substrate; PES(polypropylene) substrate ether sulfone) substrate; PEEK (polyetheretherketon) substrate; PPS (polyphenylsulfone), PEI (polyetherimide) substrate; PEN (polyethylenemaphthatlate) substrate; PET (polyethyleneterephtalate) polyester substrate such as; PI (polyimide) substrate; PSF (polysulfone) substrate ; A PAR (polyarylate) substrate or a substrate including an amorphous fluororesin may be used, but is not limited thereto The thickness of the substrate is not particularly limited and may be selected within an appropriate range.

In the light modulation device of the present application, an adhesive layer or an adhesive layer may be formed on the first surface of the first substrate.

The pressure-sensitive adhesive layer or the adhesive layer may be optically transparent. The pressure-sensitive adhesive layer or the adhesive layer may have an average transmittance of about 80% or more, 85% or more, 90% or more, or 95% or more in a visible light region, for example, a wavelength of 380 nm to 780 nm.

The type of the pressure-sensitive adhesive layer or adhesive layer is not particularly limited, and it is sufficient to use a pressure-sensitive adhesive or adhesive having strong stain resistance to liquid crystal. As such an adhesive, various types of adhesives known in the industry as so-called Optically Clear Adhesive (OCA) may be used, and the adhesive is characterized in that the adhesive is cured before the object to be adhered to. As the adhesive, for example, an acrylic, silicone, epoxy or urethane adhesive may be used. As the adhesive, various types of adhesives known as so-called optically clear resins (OCRs) in the industry may be used, and the adhesives are characterized in that the adhesive is cured after the object to be attached is cemented. Such an adhesive may be coated on a substrate and semi-cured with heat or UV, and then fully cured with heat or UV after the light modulation device is fabricated. The pressure-sensitive adhesive layer or adhesive layer may be combined with the liquid crystal alignment film to induce proper alignment of the liquid crystal compound.

In one example, the pressure-sensitive adhesive layer or adhesive layer may mean a liquid crystal alignment pressure-sensitive adhesive layer or adhesive layer having both liquid crystal alignment force and adhesion to liquid crystal molecules. For example, the pressure-sensitive adhesive or adhesive may be vertically oriented or horizontally oriented. In the present specification, the "vertically oriented pressure-sensitive adhesive or adhesive" may refer to an adhesive or adhesive having an adhesive force capable of adhering an upper substrate and a lower substrate while providing a vertical alignment force to an adjacent liquid crystal compound. In the present specification, "horizontal alignment adhesive or adhesive" may refer to an adhesive or adhesive having an adhesive force capable of adhering an upper substrate and a lower substrate while imparting a horizontal alignment force to an adjacent liquid crystal compound.

The pretilt angle of the adjacent liquid crystal compound with respect to the vertically oriented pressure-sensitive adhesive or adhesive may be in the range of 80 degrees to 90 degrees, 85 degrees to 90 degrees or 87 degrees to 90 degrees, and The pretilt angle may be in the range of 0 degrees to 10 degrees, 0 degrees to 5 degrees, and 0 degrees to 3 degrees. According to an embodiment of the present application, a vertically oriented pressure-sensitive adhesive or adhesive may be used as the pressure-sensitive adhesive or adhesive.

In the present specification, the pretilt angle may mean an angle formed by a director of a liquid crystal compound with respect to a plane parallel to an alignment layer or a liquid crystal aligning adhesive or adhesive in a state in which no voltage is applied. In the present specification, the director of the liquid crystal compound may refer to an optical axis or a slow axis of the liquid crystal layer. Alternatively, the director of the liquid crystal compound may mean a long axis direction when the liquid crystal compound has a rod shape, and may mean an axis parallel to the normal direction of the plane of the disk when the liquid crystal compound has a discotic shape. When a plurality of liquid crystal compounds having different directors exist in the liquid crystal layer, the director may be a vector sum.

In one embodiment of the present invention, the pressure-sensitive adhesive or adhesive having strong stain resistance to liquid crystal and having a vertical alignment force may be, for example, a silicone-based pressure-sensitive adhesive or adhesive. In the present invention, the silicone-based pressure-sensitive adhesive or adhesive may be used together with a barrier rib spacer and a vertical alignment film structure formed on the first surface of the second substrate to induce an effect of reducing the driving voltage of the optical modulation device.

As the silicone-based pressure-sensitive adhesive or adhesive, a cured product of a composition including a curable silicone compound may be used. If it is a curable silicone compound, since vertical alignment ability may appear on the surface properties thereof, an appropriate type may be selected from known silicone pressure-sensitive adhesives or adhesives. The type of the composition (hereinafter, curable silicone composition) containing the curable silicone compound is not particularly limited, and, for example, a heat-curable silicone composition or an ultraviolet-curable silicone composition may be used.

In one example, the curable silicone composition is an addition-curable silicone composition, (1) an organopolysiloxane containing two or more alkenyl groups in a molecule and (2) an organopolysiloxane containing two or more silicon-bonded hydrogen atoms in a molecule may include The silicone compound as described above can form a cured product by addition reaction in the presence of a catalyst such as a platinum catalyst.

More specific examples of the (1) organopolysiloxane that can be used in the present application include dimethylsiloxane-methylvinylsiloxane copolymer blocking trimethylsiloxane groups at both ends of the molecular chain, methylvinylpolysiloxane blocking both ends of the molecular chain, methylvinylpolysiloxane, molecular chain Blockade of trimethylsiloxane groups at both ends Dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer, block dimethylvinylsiloxane groups at both ends of the molecular chain Dimethylpolysiloxane, block dimethylvinylsiloxane groups at both ends of the molecular chain Methylvinylpolysiloxane, dimethylvinylsiloxane at both ends of the molecular chain acid groups blocked dimethylsiloxane-methylvinylsiloxane copolymer, a molecular chain, both ends dimethylvinylsiloxy group blocked dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers, R ^1- 2SiO1 / 2 siloxane unit represented by the R ¹ 2R ² SiO1 / Organopolysiloxane copolymer including a siloxane unit represented by 2 and a siloxane unit represented by SiO4/2, R ¹ 2R ² Organo including a siloxane unit represented by SiO1/2 and a siloxane unit represented by SiO4/2 A polysiloxane copolymer, an organopolysiloxane copolymer comprising a siloxane unit represented by R1R2SiO2/2 and a siloxane unit represented by R1SiO3/2 or a siloxane unit represented by R2SiO3/2, and a mixture of two or more of the above may be mentioned. It is not limited.

In the above, R ¹ is a hydrocarbon group other than the alkenyl group, specifically, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, or a heptyl group; Aryl groups, such as a phenyl group, a tolyl group, a xylyl group, or a naphthyl group; an aralkyl group such as a benzyl group or a phenentyl group; It may be a halogen-substituted alkyl group such as a chloromethyl group, a 3-chloropropyl group, or a 3,3,3-trifluoropropyl group.

In addition, in the above, R ² is an alkenyl group, and specifically, may be a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, or a heptenyl group.

More specific examples of the organopolysiloxane (2) that can be used in the present invention include methylhydrogenpolysiloxane blocked with trimethylsiloxane groups at both ends of the molecular chain, dimethylsiloxane-methylhydrogen copolymer with both ends of the molecular chain blocked with trimethylsiloxane groups, and molecules Blocking trimethylsiloxane groups at both ends of the chain dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymer, blocking dimethylhydrogensiloxane groups at both ends of the chain dimethylpolysiloxane, blocking dimethylhydrogensiloxane groups at both ends of the molecular chain Dimethylsiloxane-methylphenylsiloxane copolymer , methylphenylpolysiloxane blocking both ends of the molecular chain, an organopolysiloxane comprising ^{a siloxane unit represented by R 1} 3SiO1/2, a siloxane unit represented by R ¹ 2HSiO1/2, and a siloxane unit represented by SiO4/2 A copolymer, an ^{organopolysiloxane copolymer comprising a siloxane unit represented by R 1} 2HSiO1/2 and a siloxane unit represented by SiO4/2, a siloxane unit represented by R ¹ HSiO2/2 and a siloxane unit represented by R ¹ SiO3/2 an organopolysiloxane copolymer including a siloxane unit or a siloxane unit represented by HSiO3/2, and a mixture of two or more of the above, but is not limited thereto. In the above, R ¹ is a hydrocarbon group other than the alkenyl group, specifically, an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, or a heptyl group; Aryl groups, such as a phenyl group, a tolyl group, a xylyl group, or a naphthyl group; an aralkyl group such as a benzyl group or a phenentyl group; It may be a halogen-substituted alkyl group such as a chloromethyl group, a 3-chloropropyl group, or a 3,3,3-trifluoropropyl group.

The content of the (2) organopolysiloxane is not particularly limited as long as it is included to the extent that appropriate curing can be achieved. For example, the (2) organopolysiloxane may be contained in an amount such that the number of silicon-bonded hydrogen atoms is 0.5 to 10 with respect to one alkenyl group included in the aforementioned (1) organopolysiloxane. In this range, curing can be sufficiently advanced and heat resistance can be secured.

The addition-curable silicone composition may further include platinum or a platinum compound as a catalyst for curing. As such, the specific kind of platinum or the platinum compound is not particularly limited. The ratio of the catalyst may also be adjusted to a level at which proper curing can be achieved.

The addition-curable silicone composition may also contain an appropriate additive required from the viewpoint of storage stability, handleability and workability improvement in an appropriate ratio.

In another example, the silicone composition is a condensation-curable silicone composition, for example, (a) an alkoxy group-containing siloxane polymer; and (b) a hydroxyl group-containing siloxane polymer.

The (a) siloxane polymer may be, for example, a compound represented by the following formula (1).

[Formula 1]

R ¹ _a R ² _b SiO _c (OR ³ ) _d

In Formula 1, R ¹ and R ² each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, R ³ represents an alkyl group, and when a plurality of ^{R 1} , R ² and R ^{3 are each present} may be the same as or different from each other, a and b each independently represent a number greater than or equal to 0 and less than 1, a+b represents a number greater than 0 and less than 2, c represents a number greater than 0 and less than 2 , d represents a number greater than 0 and less than 4, and a+b+c×2+d is 4.

In the definition of Formula 1, the monovalent hydrocarbon may be, for example, an alkyl group having 1 to 8 carbon atoms, a phenyl group, a benzyl group or a tolyl group, and in this case, the alkyl group having 1 to 8 carbon atoms includes a methyl group, an ethyl group, a propyl group, It may be an isopropyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, or an octyl group. In addition, in the definition of Formula 1, the monovalent hydrocarbon group may be substituted with a known substituent such as, for example, a halogen, an amino group, a mercapto group, an isocyanate group, a glycidyl group, a glycidoxy group, or a ureido group.

In the definition of Formula 1, ^{examples of the alkyl group of R 3} include a methyl group, an ethyl group, a propyl group, an isopropyl group, or a butyl group. Among the alkyl groups, a methyl group or an ethyl group is usually applied, but is not limited thereto.

A branched or tertiarily crosslinked siloxane polymer among the polymers of Formula 1 may be used. In addition, in this (a) siloxane polymer, the hydroxyl group may remain|survive within the range which does not impair the objective, specifically, within the range which does not inhibit a dealcoholization reaction.

The siloxane polymer (a) can be produced, for example, by hydrolyzing and condensing polyfunctional alkoxysilane or polyfunctional chlorosilane. An average person skilled in the art can easily select an appropriate polyfunctional alkoxysilane or chlorosilane according to the desired (a) siloxane polymer, and the conditions of hydrolysis and condensation reaction using the same can also be easily controlled. On the other hand, in the production of the (a) siloxane polymer, an appropriate monofunctional alkoxysilane may be used in combination according to the purpose.

As the siloxane polymer (a), for example, commercially available organosiloxanes such as X40-9220 or X40-9225 by Shin-Etsu Silicone, XR31-B1410, XR31-B0270 or XR31-B2733 by GE Toray Silicone Polymers may be used.

As the (b) hydroxyl group-containing siloxane polymer contained in the condensation-curable silicone composition, for example, a compound represented by the following formula (2) can be used.

[Formula 2]

In Formula 2, R ⁴ and R ⁵ each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, ^{and when a plurality of R 5} and R ⁶ are present, they may be the same as or different from each other. and n represents an integer of 5 to 2,000.

In the definition of the formula (2), specific types of the monovalent hydrocarbon group include, for example, the same hydrocarbon group as in the case of the formula (1).

The siloxane polymer (b) can be produced, for example, by hydrolyzing and condensing dialkoxysilane and/or dichlorosilane. A person skilled in the art can easily select an appropriate dialkoxy silane or dichlorosilane according to the desired (b) siloxane polymer, and can also easily control the conditions of hydrolysis and condensation reaction using the same. As the siloxane polymer (b) as described above, for example, a commercially available bifunctional organosiloxane polymer such as XC96-723, YF-3800, YF-3804 manufactured by GE Toray Silicones can be used.

The type of the pressure-sensitive adhesive or adhesive having the vertical alignment force is not particularly limited and may be appropriately selected depending on the intended use. For example, a solid, semi-solid, elastic, or liquid pressure-sensitive adhesive or adhesive may be appropriately selected and used. The solid or semi-solid or elastic pressure sensitive adhesive may be referred to as a pressure sensitive adhesive (PSA), and may be cured before an adhesive object is bonded. In the present application, for example, a polydimethyl siloxane adhesive or a polymethylvinyl siloxane adhesive may be used as a PSA type adhesive having a vertical alignment force, and an OCR type adhesive having a vertical alignment force may be used. An alkoxy silicone adhesive may be used as the adhesive, but is not limited thereto.

The thickness of the pressure-sensitive adhesive layer or the adhesive layer is not particularly limited, and may be selected within an appropriate range for securing a desired adhesive force. The thickness may be in the range of approximately 1 μm to 50 μm. The thickness is 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more, 8 μm or more, 9 μm or more, or 10 μm or more, or 45 μm or less, 40 μm or less in another example. , 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

By including the pressure-sensitive adhesive layer or the adhesive layer having the above properties under the arrangement as described above, it is possible to provide a light modulation device capable of exhibiting excellent optical properties by controlling light leakage in a blocking mode while having excellent adhesion.

In the present application, a vertical alignment layer 203 may be formed on the first surface of the second substrate 201 . The combination of the vertical alignment layer 203 and the pressure-sensitive adhesive layer or adhesive layer 103 can induce an alignment state of the liquid crystal compound suitable for various uses, and is used together with the barrier rib spacer 400 structure to form a light modulation device. There is an effect of reducing the driving voltage. The type of the vertical alignment layer may be a contact alignment layer such as a rubbing alignment layer, or a non-contact alignment layer such as a photo alignment layer.

The liquid crystal layer 300 may exist between the pressure-sensitive adhesive layer or adhesive layer of the first substrate and the vertical alignment layer of the second substrate. The liquid crystal layer is a functional layer capable of changing light transmittance, reflectivity, haze, and/or color, either alone or in conjunction with other components, depending on whether an external signal is applied. In the present specification, an external signal may mean an external factor that may affect the behavior of a material included in the liquid crystal layer, for example, a light modulation material, for example, an external voltage. Accordingly, the state in which there is no external signal may mean a state in which there is no application of an external voltage or the like.

The liquid crystal layer is a layer containing a liquid crystal compound, and as will be described later, a so-called guest host layer containing a liquid crystal compound (liquid crystal host) and a dichroic dye, or a layer containing other additives such as a chiral dopant together with the liquid crystal compound It is a kind of liquid crystal layer specified in the specification. The liquid crystal compound may be present in the liquid crystal layer so that the alignment direction changes depending on whether an external signal is applied. As the liquid crystal compound, any kind of liquid crystal compound may be used as long as its alignment direction can be changed by application of an external signal.

The liquid crystal layer may include a liquid crystal compound having a positive or negative dielectric anisotropy. The absolute value of the dielectric anisotropy of the liquid crystal may be appropriately selected in consideration of the purpose of the present application. The term “dielectric anisotropy (Δε)” may mean a difference (ε// - ε⊥) between a horizontal dielectric constant (ε//) and a vertical dielectric constant (ε⊥) of a liquid crystal. As used herein, the term horizontal permittivity (ε//) refers to a dielectric constant value measured along the direction of the electric field in a state in which a voltage is applied so that the direction of the electric field by the applied voltage and the director of liquid crystal molecules is substantially horizontal, The perpendicular permittivity ε⊥ refers to a dielectric constant value measured along the direction of the electric field in a state in which a voltage is applied so that the direction of the electric field by the applied voltage is substantially perpendicular to the direction of the liquid crystal molecules.

The liquid crystal layer may further include a dichroic dye together with the liquid crystal compound in terms of adjusting the light transmittance variable property, and as described above, the liquid crystal layer in this case is used as a guest host liquid crystal layer. can call In the present specification, "dye" may mean a material capable of intensively absorbing and/or transforming light within the visible light region, for example, at least a portion or the entire range within a wavelength range of 400 nm to 700 nm, and the term The "dichroic dye" may refer to a material capable of anisotropic absorption of light in at least a part or the entire range of the visible light region. In the present specification, "GHLC layer (Guest host liquid crystal layer)" refers to a dichroic dye in which a dichroic dye is arranged according to the arrangement of liquid crystals, and anisotropic light absorption is respectively directed to the alignment direction of the dichroic dye and the direction perpendicular to the alignment direction. It may mean a functional layer exhibiting properties. For example, a dichroic dye is a material whose absorption rate of light varies depending on the polarization direction. If the absorption rate of light polarized in the long-axis direction is large, it is called a p-type dye, and if the absorption rate of light polarized in the short-axis direction is large, it is called an n-type dye. can be called In one example, when a p-type dye is used, polarized light vibrating in the long axis direction of the dye is absorbed, and polarized light vibrating in the short axis direction of the dye is absorbed and transmitted therethrough. Hereinafter, it is assumed that the dichroic dye is a p-type dye, unless otherwise specified.

As the dichroic dye, for example, a known dye known to have a property of being aligned according to the alignment state of liquid crystal molecules by a so-called guest host effect may be selected and used. Examples of such dichroic dyes include azo dyes, anthraquinone dyes, methine dyes, azomethine dyes, merocyanine dyes, naphthoquinone dyes, tetrazine dyes, phenylene dyes, quinerylene dyes, benzothiadiazole dyes, poly There are iketopyrrolopyrrole dyes, squaraine dyes or pyromethene dyes, but the dyes applicable in the present application are not limited thereto.

The dichroic dye has a dichroic ratio, that is, a value obtained by dividing absorption of polarized light parallel to the long axis direction of the dichroic dye by absorption of polarized light parallel to a direction perpendicular to the major axis direction is 5 or more, 6 or more, or 7 More than one dye can be used. The dye may satisfy the dichroic ratio at at least some wavelengths or any one wavelength within the wavelength range of the visible light region, for example, 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 14 or less.

The content of the dichroic dye in the liquid crystal layer may be appropriately selected in consideration of the purpose of the present application. For example, the content of the dichroic dye in the 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 dichroic dye in the liquid crystal layer is, for example, 5.0 wt% or less, .4.0 wt% or less, 3.0 wt% or less, 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% or less. When the content of the dichroic dye in the liquid crystal layer satisfies the above range, it is possible to provide an optical modulation device having excellent transmittance variable characteristics. In one example, as the content of the dichroic dye increases within the above range, it is possible to provide a light modulation device having excellent transmittance variable characteristics.

The type and physical properties of the liquid crystal molecules of the liquid crystal compound may be appropriately selected in consideration of the purpose of the present application. In one example, the liquid crystal molecule may be a nematic liquid crystal or a smectic liquid crystal. Nematic liquid crystal may refer to a liquid crystal in which rod-shaped liquid crystal molecules are arranged in parallel in the long axis direction of the liquid crystal molecules although there is no regularity in their positions. It may refer to liquid crystals that form a structure and are arranged in parallel with regularity in the major axis direction. According to an embodiment of the present application, a nematic liquid crystal may be used as the liquid crystal molecule.

In one example, the liquid crystal molecule may be a non-reactive liquid crystal molecule. The non-reactive liquid crystal molecule may mean a liquid crystal molecule not having a polymerizable group. In the above, the polymerizable group may be exemplified by an acryloyl group, an acryloyloxy group, a methacryloyl group, a methacryloyloxy group, a carboxyl group, a hydroxyl group, a vinyl group or an epoxy group, but is not limited thereto, and is known as a polymerizable group. A known functional group may be included.

The refractive index anisotropy of the liquid crystal molecules may be appropriately selected in consideration of a target physical property, for example, a transmittance variable characteristic. In the present specification, the term “refractive index anisotropy” may mean a difference between an extraordinary refractive index and an ordinary refractive index of a liquid crystal molecule. The refractive index anisotropy of the liquid crystal molecules may be, for example, 0.01 to 0.3. The refractive index anisotropy may be 0.01 or more, 0.05 or more, or 0.07 or more, and may be 0.3 or less, 0.2 or less, 0.15 or less, or 0.13 or less. When the refractive index anisotropy of the liquid crystal molecules is within the above range, it is possible to provide an optical modulation device having excellent transmittance variable characteristics. In one example, as the refractive index of the liquid crystal molecules is lower within the above range, it is possible to provide a light modulation device having excellent transmittance variable characteristics.

The dielectric anisotropy of the liquid crystal molecules may have a positive dielectric anisotropy or a negative dielectric anisotropy in consideration of a desired driving method of the liquid crystal cell. As used herein, the term "dielectric anisotropy" may mean the difference between the extraordinary dielectric constant (εe, extraordinary dielectric anisotropy, long-axis dielectric constant) and the normal dielectric constant (εo, ordinary dielectric anisotropy, short-axis dielectric constant) of liquid crystal molecules. The dielectric anisotropy of the liquid crystal molecules may be, for example, within ±40, within ±30, within ±10, within ±7, within ±5, or within ±3. If the dielectric anisotropy of the liquid crystal molecules is adjusted within the above range, it may be advantageous in terms of driving efficiency of the light modulation device.

The total weight of the liquid crystal molecules of the liquid crystal compound and the dichroic dye in the liquid crystal layer is, for example, about 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80% by weight or more, 85 weight % or greater, 90 weight % or greater, or 95 weight % or greater, and in other examples less than about 100 weight %, 98 weight % or less, or 96 weight % or less.

The liquid crystal layer may change an alignment state depending on whether a voltage is applied. The voltage may be incident in a direction perpendicular to the first and second substrates.

In one example, the liquid crystal layer may exist in a twisted state when no voltage is applied, and may exist in a vertically aligned state when a voltage is applied. In the twist orientation state, the twist angle may be, for example, 860 degrees or more. Such a liquid crystal cell may be referred to as a highly twisted nematic (HTN) driving mode liquid crystal cell. The upper limit of the twist angle may be, for example, 2160 degrees or less. In the present specification, the twist angle may be calculated by the following general formula (1).

[General formula 1]

Twisting angle (A) = a+b×360

In Formula 1, a is the angle formed by the optical axis of the liquid crystal molecule present at the lowermost portion and the optical axis of the liquid crystal molecule present at the uppermost portion in the liquid crystal layer in the twist alignment state, and b is the number of pitches.

According to an embodiment of the present application, the twist angle is about 870 degrees or more, 880 degrees or more, 890 degrees or more, 900 degrees or more, 910 degrees or more, 920 degrees or more, 930 degrees or more, 940 degrees or more, 950 degrees or more, 960 degrees or more. It may be more than degrees, more than 970 degrees, more than 980 degrees, more than 990 degrees, or more than 1000 degrees. The lower limit of the twist angle may be about 2130 degrees or less, 2100 degrees or less, 2070 degrees or less, 2040 degrees or less, 2010 degrees or less, 1980 degrees or less, 1950 degrees or less, or 1920 degrees or less.

The present application can provide an optical modulation device having an excellent transmittance variable level while realizing low transmittance by applying the HTN liquid crystal driving mode.

In the twist alignment liquid crystal layer, liquid crystal molecules may have a spiral structure in which an optical axis is oriented in layers while twisting along an imaginary spiral axis. The optical axis of the liquid crystal molecules may mean the slow axis of the liquid crystal molecules, and the slow axis of the liquid crystal molecules may be parallel to the long axis of the rod-shaped liquid crystal molecules. The spiral axis may be formed to be parallel to the thickness direction of the liquid crystal layer. In the present specification, the thickness direction of the liquid crystal layer may mean a direction parallel to an imaginary line connecting the lowermost part and the uppermost part of the liquid crystal layer by the shortest distance. In one example, the thickness direction of the liquid crystal layer may be a direction parallel to an imaginary line formed in a direction perpendicular to the surface of the polymer substrate. In the present specification, the twist angle refers to an angle between the optical axis of the liquid crystal molecule present at the lowermost portion and the optical axis of the liquid crystal molecule present at the uppermost portion in the twist alignment liquid crystal layer.

The ratio (d/p) of the thickness (d) to the pitch (p) of the liquid crystal layer in the twisted alignment state may be 2 to 6. When the ratio (d/p) is less than 2, an increase in initial transmittance occurs and thus the object of the present invention of implementing a low transmittance cannot be achieved, and when the ratio (d/p) exceeds 6, the driving voltage is Since it increases, it is preferable to adjust it as much as possible in the above range. In another example, the ratio (d/p) may be about 2.3 or more, 2.5 or more, 2.7 or more, 2.9 or more, 3.1 or more, 3.3 or more, or 3.5 or more, and about 5.7 or less, 5.5 or less, 5.3 or less, 5.1 or less, 4.9 or less or 4.7 or less. The thickness d of the liquid crystal layer may have the same meaning as a cell gap in the light modulation device.

The thickness d of the liquid crystal layer may have the same meaning as a cell gap in the light modulation device. The thickness (d) of the liquid crystal layer in the present application may be in the range of 0.1 μm to 50 μm, and in other examples 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more or 8 μm or less, or 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 9 μm or less, or 8 μm or less.

The pitch (p) of the liquid crystal layer can be measured by a measurement method using a wedge cell, and specifically, D. Podolskyy et al.'s Simple method for accurate measurements of the cholesteric pitch using a "stripe-wedge Grandjean-Cano cell (Liquid Crystals) , Vol. 35, No. 7, July 2008, 789-791).

The ratio (d/p) can be achieved by introducing an appropriate amount of a chiral dopant into the liquid crystal layer. The chiral dopant included in the liquid crystal layer is not particularly limited as long as it can induce desired twisting without impairing liquid crystallinity, for example, nematic regularity. The chiral dopant for inducing rotation in the liquid crystal molecules needs to include at least chirality in the molecular structure. The chiral agent includes, for example, a compound having one or two or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine or a chiral sulfoxide, or cumulene ) or a compound having an axially asymmetric, optically active site having an axial agent such as binaphthol may be exemplified. The chiral agent may be, for example, a low molecular weight compound having a molecular weight of 1,500 or less. As the chiral agent, a commercially available chiral nematic liquid crystal, for example, a chiral dopant liquid crystal S-811 commercially available from Merck or LC756 from BASF may be used.

The rate of application of the chiral dopant is chosen so as to achieve the desired ratio (d/p). In general, the content (wt%) of the chiral dopant may be calculated by the formula of 100/HTP (Helixcal Twisting power) × pitch (p) (nm). The HTP indicates the strength of the twist of the chiral dopant, and the content of the chiral dopant may be determined in consideration of a desired pitch with reference to the above method.

The optical modulation device of the present application applies a structure using a pressure-sensitive adhesive layer or an adhesive layer, a vertical alignment layer formed on the first surface of the second substrate, and a barrier rib spacer to be described later, so that the optical modulation device has excellent transmittance variation even at a low driving voltage can provide

In the light modulation device of the present application, a gap between the first substrate and the second substrate may be maintained by the barrier rib spacer 400 . As the barrier rib spacer, a honeycomb type, a rectangular barrier rib spacer, or a random spacer may be applied. In the above, the honeycomb or quadrangular barrier rib spacer is a case in which the shape formed by the barrier rib spacer is honeycomb or quadrangular when the shape of the barrier rib spacer formed on the substrate is observed in the normal direction of the substrate. it means. The honeycomb type is usually a combination of a regular hexagon, and in the case of a square, there may be a square, a rectangle, or a combination of a square and a rectangle. Also, in the above description, the random spacer refers to a case in which the partition walls are randomly arranged, and the partition walls do not form a figure or a case in which a figure is formed at random rather than a standardized figure even when the partition walls are formed.

The pitch P of the barrier rib spacer may be appropriately selected in consideration of a desired adhesion force or cell gap maintenance efficiency. In the present specification, the term pitch refers to the length of each side of the quadrangle, which is confirmed when the spacer is observed from the top. In the present specification, observing the spacer from above means observing the spacer parallel to the normal direction of the plane of the spacer and the substrate. When all sides of the rectangle have the same length (that is, when the rectangle is a square), the length of the same side is defined as a pitch, and when the lengths of each side are not the same (eg, when the rectangle is a rectangle), The arithmetic mean of the lengths of all sides can be defined as the pitch.

For example, the pitch P of the barrier rib spacer may be in a range of 300 μm to 900 μm. The pitch is 350 μm or more, 400 μm or more, 450 μm or more, 500 μm or more, or 550 μm or more, or 850 μm or less, 800 μm or less, 750 μm or less, 700 μm or less, 650 μm or less, or 600 μm or less in another example. can A method of obtaining the pitch in the partition wall spacer is known. For example, if the barrier rib spacer is a honeycomb type, the pitch is obtained through the distance between the sides facing each other in the hexagon constituting the honeycomb, and in the case of the rectangular spacer, the pitch is obtained through the length of the side of the rectangle. When the distance between the sides of the hexagon constituting the honeycomb or the length of the sides of the rectangle is not constant, the average value thereof may be defined as the pitch.

Meanwhile, the line width of the barrier rib spacer, for example, the width of each hexagonal or rectangular wall constituting the honeycomb may be, for example, within a range of about 5 μm to 50 μm. In another example, the line width may be about 10 μm or more, 15 μm or more, or 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, or 20 μm or less. In the above range, the cell gap may be properly maintained, and adhesion between the substrates may be maintained excellently.

Meanwhile, the height of the barrier rib spacer may be adjusted in consideration of the distance between the upper substrate and the lower substrate. In the present application, the height of the barrier rib spacer substantially coincides with the thickness of the liquid crystal layer (cell gap) and means the dimension of the spacer measured in the normal direction of the surface of the substrate. For example, the height of the barrier rib spacer may be in the range of 0.1 μm to 50 μm, and in another example, 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 6 μm or more, 7 μm or more or 8 μm or more, 45 μm or less, 40 μm or less, 35 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, 15 μm or less, 10 μm or less, 9 μm or less, or 8 μm or less, but is not limited thereto no. In this case, when the height of the spacer is not constant, the height may be a measured maximum height, a minimum height, or an average value of the maximum and minimum heights.

In the present application, the spacer may be manufactured by applying a conventional method for manufacturing the spacer in the form of a barrier rib. In general, the partition wall spacer may be manufactured by using a curable resin composition (eg, imprinting method, etc.). Accordingly, the spacer of the present application may include a cured product of the curable resin composition. As the curable resin composition, a known type applied for spacer formation may be applied without any particular limitation. Such a resin composition is usually a heat-curable resin composition or a photo-curable resin composition, for example, an ultraviolet-curable resin composition.

As the heat-curable resin composition, for example, a silicone resin composition, a fran resin composition, a polyurethane resin composition, an epoxy resin composition, an amino resin composition, a phenol resin composition, a urea resin composition, a polyester resin composition, or a melamine resin composition, etc. can be used. may be, but is not limited thereto.

The ultraviolet curable resin composition is typically an acrylic polymer, for example, a polyester acrylate polymer, a polystyrene acrylate polymer, an epoxy acrylate polymer, a polyurethane acrylate polymer or a polybutadiene acrylate polymer, a silicone acrylate polymer, or an alkyl acrylate. A resin composition including a polymer or the like may be used, but is not limited thereto. As another example, it may be formed using a silicone polymer, and when the spacer is formed using a silicone polymer, the silicone polymer remaining in the concave region of the spacer can serve as a vertical alignment layer, so that the spacer is An additional vertical alignment layer may not be used on the existing substrate. As the silicone polymer, a known polymer having a silicon-oxygen bond (Si-O-Si) as a main axis may be used, for example, polydimethylsiloxane (PDMS, Polydimethylsiloxane) may be used, but is not limited thereto.

The present application can provide an optical modulation device in which the cell gap is properly maintained and the adhesion between the upper and lower film substrates is excellent by controlling the shape, arrangement and/or arrangement method of the spacer as described above.

The light modulation device of the present application may further include an electrode layer 500 on one surface of the first substrate and the second substrate, respectively, as long as the effects of the present application are not hindered. In one example, an electrode layer may be formed between the first surface of the first substrate and the pressure-sensitive adhesive layer or adhesive layer, and between the first surface of the second substrate and the alignment layer, respectively.

The electrode layer may apply an appropriate electric field to the liquid crystal layer to change the alignment state of the liquid crystal molecules. The direction of the electric field may be a vertical or horizontal direction, for example, a thickness direction or a plane direction of the liquid crystal layer.

The electrode layer may be, for example, a transparent conductive layer. The transparent conductive layer may be formed by, for example, depositing a conductive polymer, a conductive metal, a conductive nanowire, or a metal oxide such as indium tin oxide (ITO). In addition, various materials and methods for forming the transparent conductive layer are known and can be applied without limitation.

The light modulation device of the present application may include additional other components as needed. That is, depending on the driving mode, it is possible to implement the above-described transmission mode and the blocking mode and switch between them even with the light modulation device having the above structure alone, but the inclusion of an additional configuration to facilitate the implementation or switching of these modes It is possible.

For example, the device may further include a polarizing layer on the second surface of the first and/or second substrate. The term polarization layer may refer to a device that converts natural light or unpolarized light into polarized light. In one example, the polarization layer may be a linear polarization layer. The linear polarization layer refers to a case in which selectively transmitted light is linearly polarized light vibrating in one direction, and selectively absorbed or reflected light is linearly polarized light vibrating in a direction orthogonal to the vibration direction of the linearly polarized light. That is, the linear polarization layer may have a transmission axis and an absorption axis or a reflection axis orthogonal to each other in a plane direction.

The polarization layer may be an absorption type polarization layer or a reflection type polarization layer. As the absorption type polarizing layer, for example, a polarizing layer in which iodine is dyed on a polymer stretched film such as a PVA (poly(vinyl alcohol)) stretched film, or a liquid crystal polymerized in an aligned state is used as a host, and the alignment of the liquid crystal is performed. A guest-host type polarizing layer in which a dichroic dye arranged according to a guest is used may be used, but the present invention is not limited thereto. As the reflective polarizing layer, for example, a reflective polarizing layer known as a so-called DBEF (Dual Brightness Enhancement Film) or a reflective polarizing layer formed by coating a liquid crystal compound such as LLC (Lyotropic liquid crystal) may be used. , but is not limited thereto.

The above-described optical modulation device may exist in a twisted alignment state when no voltage is applied to exhibit minimum transmittance, and may exist in a vertically aligned state when voltage is applied to exhibit maximum transmittance.

The transmittance of the light modulation device in the transmittance mode state exhibiting the maximum transmittance may be at least about 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, or 80% or more. have. The transmittance of the optical modulation device in the cut-off mode state showing the minimum transmittance is 20% or less, 15% or less, 10% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less, 0.9% or less , 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, or 0.3% or less.

In the transmission mode, the higher the transmittance, the more advantageous, and the lower the transmittance in the blocking mode, the more advantageous. In one example, the upper limit of the transmittance in the transmission mode state may be about 100%, and the lower limit of the transmittance in the blocking mode state may be about 0%.

The optical modulation device of the present application can switch between the blocking mode state and the transmission mode state even with a low driving voltage. For example, the light modulation device of the present application has a transmission mode having a transmittance of 50% or more, and 20% or less, 15% or less, 10% or less, 5% or less, 4% or less, 3% or less, 2% or less, 1% or less , 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, or 0.3% or less of the required voltage to switch between cut-off modes of 40V or less, 38V or less, 36V or less, 34V or less, 32V or less, 30V or less, 28V or less, 26V or less, or 24V or less.

In one example, the difference between the transmittance in the transmission mode state and the transmittance in the blocking mode state (transmission mode-blocking mode) in the light modulation device is 36% or more, 37% or more, 38% or more, 39% or more, 40 % or more 41% or more, 42% or more, 43% or more, 44% or more, 45% or more, 46% or more, or 47% or more, or 90% or less, 85% or less, 80% or less, 75% or more, 70% or more or less, 65% or less, 60% or less, 55% or less, or 50% or less.

The present application can provide an excellent optical modulation device having a variable transmittance level (difference between transmittance in the transmittance mode and transmittance in the block mode state) of 36% or more while implementing low transmittance in the blocking mode state as described above, There is an advantage in that the optical modulation device as described above can be driven with a low driving voltage.

The above-mentioned transmittance may be, for example, a straight light transmittance. The straight light transmittance is a percentage of the ratio of the light transmitted in the same direction as the incident direction to the light incident on the device. For example, if the device is in the form of a film or sheet, the transmittance is defined as the percentage of light that has passed through the device in a direction parallel to the normal direction among the light incident in a direction parallel to the normal direction of the film or sheet surface. can

The above-mentioned transmittance and reflectance are the transmittance or reflectance for any one wavelength in the visible light region, for example, about 400 to 700 nm or about 380 to 780 nm, respectively, or the transmittance or reflectance for the entire visible light region, It may be a maximum or minimum transmittance or reflectance among transmittances or reflectances for the entire visible light region, or an average value of transmittances or reflectances within the visible light region.

The light modulation device may control the alignment state of the liquid crystal compound, and may switch between the haze mode and the non-haze mode through application of an external action such as a voltage. For example, when the liquid crystal compound exists in an irregularly arranged state, the optical modulation device may exhibit a haze mode, and when the liquid crystal compound exists in an aligned state, the optical modulation device may exhibit a non-haze mode. In the present specification, "haze mode" means a mode in which the liquid crystal cell exhibits haze above a predetermined level, and "non-haze mode" may refer to a mode in which light can be transmitted or a mode in which haze is below a predetermined level.

For example, the optical modulation device in the haze mode has a haze of 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, 80% or more, 85% or more, 90% or more, or 95% or more. The optical modulation device in the non-haze mode may, for example, have a haze of less than 10%, less than 9%, less than 8%, less than 7%, less than 6%, or less than 5%. The haze may be a percentage of transmittance of diffused light with respect to transmittance of total transmitted light passing through the measurement target. The haze may be evaluated using a hazemeter (NDH5000SP). That is, the light is transmitted through the measurement object and is incident into the integrating sphere. In this process, the light is divided into diffused light (DT) and parallel light (PT) by the measurement target. These lights are reflected within the integrating sphere and condensed on the light receiving element, and the haze can be measured through the condensed light. do. That is, the total transmitted light TT by the above process is the sum (DT+PT) of the diffused light DT and the parallel light PT, and the haze is the percentage of the diffused light with respect to the total transmitted light (Haze(%) = 100ХDT) /TT) can be specified.

The optical modulation device of the present application can switch between the haze mode and the non-haze mode even with a low driving voltage. For example, the optical modulation device has a required voltage for switching between a haze mode in which the haze is 40% or more and a non-haze mode in which the haze is less than 10%, 40V or less, 38V or less, 36V or less, 34V or less, 32V or less, 30V or less, 28V or less , 26V or less or 24V or less.

The optical modulation device as described above can be applied to various uses. Applications to which the light modulation device can be applied include openings in closed spaces including buildings, containers, or vehicles such as windows or sunroofs, eyewear, etc. This can be exemplified. In the above, the scope of eyewear includes general eyewear, sunglasses, sports goggles or helmets, or wearable devices such as virtual reality or augmented reality experience devices, etc., all eyewear formed so that an observer can observe the outside through a lens. have.

A typical use to which the light modulation device of the present application can be applied may include a vehicle sunroof. In one example, the light modulation device may itself be a vehicle sunroof. For example, in a vehicle including a vehicle body in which at least one opening is formed, the optical modulation device or a vehicle sunroof mounted in the opening may be mounted and used.

A sunroof is a fixed or operating (venting or sliding) opening in the ceiling of a vehicle, and may refer to a device capable of allowing light or fresh air to flow into the interior of the vehicle. . In the present application, the operation method of the sunroof is not particularly limited, and for example, it may be manually operated or driven by a motor, and the shape, size or style of the sunroof may be appropriately selected according to the intended use. For example, depending on the operation method of the sunroof, a pop-up type sunroof, a spoiler (tile & slide) type sunroof, an in-built type sunroof, a folding type sunroof, a top-mount type sunroof, and a panoramic roof system A type sunroof, a removable roof panel (t-tops or targa roofts) type sunroof or a solar type sunroof may be exemplified, but the present disclosure is not limited thereto.

The exemplary sunroof of the present application may include the optical modulation device of the present application, and in this case, the details of the optical modulation device may be identically applied to the contents described in the item of the optical modulation device.

The optical modulation device using the HTN liquid crystal driving mode according to the present application includes a barrier rib spacer for maintaining a cell gap between two substrates, an adhesive layer or adhesive layer formed instead of an alignment film on one substrate, and a vertical substrate formed on the other substrate Through the structure including the alignment layer, it is possible to realize low transmittance and drive an optical modulation device having a large transmittance variable level with a low driving voltage.

1 is a schematic diagram of an optical modulation device according to an example of the present application.
2 is a graph illustrating a change in transmittance according to a driving voltage of an optical modulation device according to Example 1 and Comparative Examples 1 to 3;
3 is a graph illustrating a change in haze value according to a driving voltage of an optical modulation device according to Example 1 and Comparative Examples 1 to 3;

Hereinafter, the present invention will be described in more detail through Examples according to the present invention and Comparative Examples not according to the present invention, but the scope of the present invention is not limited by the Examples presented below.

Example 1

As the first substrate, a poly(ethylene terephthalate) (PET) film having a thickness of about 125 μm in which an indium tin oxide (ITO) layer was deposited to a thickness of about 30 nm on the first surface was used. A silicone adhesive layer was formed on the ITO layer of the PET film. The pressure-sensitive adhesive was bar-coated with a silicone pressure-sensitive adhesive composition (Shinetsu, KR3700) and dried at about 150° C. for 5 minutes to form a thickness of about 10 μm.

As the second substrate, a poly(ethylene terephthalate) (PET) film having a thickness of about 125 μm was used as an indium tin oxide (ITO) layer deposited on the first surface to a thickness of about 30 nm. First, on the ITO layer of the PET film, a square-shaped barrier rib spacer having a pitch of about 350 μm, a cell gap of about 6.3 μm, and a line width of about 30 μm is formed, A vertical alignment layer (5661LB3, Nissan Co.) was formed on the formed spacer to a thickness of about 300 nm. The vertical alignment layer was formed by rubbing in one direction.

Then, the liquid crystal composition was coated on the surface of the vertical alignment layer of the second substrate, and the pressure-sensitive adhesive layer of the first substrate was laminated to face the coated surface of the liquid crystal composition.

As the liquid crystal composition, a composition including a liquid crystal compound (JNC, SHN-5011XX), a chiral dopant (HCCH, S811) and a dichroic dye (LG Chem, black dye combination) was used as the liquid crystal composition. At this time, the chiral dopant was included to be 3.7 wt% in the liquid crystal layer, and the dichroic dye was included to be 3 wt% in the liquid crystal layer. The pitch (p) of the liquid crystal layer formed as described above was about 2.5 μm, and the ratio (d/p) of the thickness (d) to the pitch (p) was about 2.5. In the above, the pitch of the liquid crystal layer is described by D. Podolskyy et al. Simple method for accurate measurements of the cholesteric pitch using a "stripe-wedge Grandjean-Cano cell (Liquid Crystals, Vol. 35, No. 7, July 2008, 789-791) ) was measured by a measurement method using a wedge cell according to the method described in

The liquid crystal cell is an HTN mode liquid crystal cell having a twist angle of 860 degrees.

Comparative Example 1

A liquid crystal cell was manufactured in the same manner as in Example 1, except that an alignment layer was not formed when the second substrate was manufactured. The ratio (d/p) of the thickness (d) and the pitch (p) of the liquid crystal layer of Comparative Example 1 is about 2.5, and the liquid crystal cell has a twist angle of about 860 degrees.

Comparative Example 2

A liquid crystal cell was manufactured in the same manner as in Example 1, except that a horizontal alignment layer was formed on the spacers when the second substrate was manufactured. p) is about 2.5, and the twist angle is about 860 degrees liquid crystal cell.

Comparative Example 3

A liquid crystal cell was manufactured in the same manner as in Example 1, except that a silicone pressure-sensitive adhesive composition (Dow Corning, DOW7657) was used for manufacturing the first substrate, and a horizontal alignment layer was formed on the spacer when manufacturing the second substrate.

The ratio (d/p) of the thickness (d) and the pitch (p) of the liquid crystal layer of Comparative Example 3 is about 6.15, and the twist angle is about 2200 degrees of the liquid crystal cell.

Experimental Example 1. Transmittance and haze evaluation

The transmittance and haze according to the voltage applied while connecting and driving the AC power to each of the electrode layers of the first and second substrates were measured using a haze meter (NDH5000SP, Secos Co., Ltd.) according to ASTM D1003 standard.

Specifically, when light with a wavelength of 380 nm to 780 nm is incident on a measurement target in the integrating sphere, the incident light is diffused light (DT, sum of diffused and emitted light) and straight light (PT, diffused light) by the measurement target. light emitted in the front direction excluded). The diffused light and the straight light may be individually measured by condensing the light-receiving element within the integrating sphere. That is, by the above process, the total transmitted light TT is defined as the sum (DT+PT) of the diffused light DT and the straight light PT, and the haze is the diffused light DT for the total transmitted light TT. It is defined as the 100 fraction of (100 × (DT/TT)). The total transmitted light means total transmittance.

The transmittance and haze values according to the voltage application of the liquid crystal cells prepared in Example 1 and Comparative Examples 1 to 3 are compared and shown in Table 1 below.

division Transmittance (%) Transmittance gradient (%) Haze (%) Shutdown mode (0V) Transmissive mode (50V) Shutdown mode (0V) Transmissive mode (50V) Example 1 17.6 54.4 36.7 20.0 6.5 Comparative Example 1 12.5 37.9 25.4 12.5 31.7 Comparative Example 2 13.3 49.0 35.7 13.8 9.0 Comparative Example 3 10.3 44.3 34.0 13.5 12.8

Referring to Table 1, the liquid crystal cell of Example 1 in which a silicone-based pressure-sensitive adhesive layer is formed on the first substrate and a vertical alignment film is formed on the second substrate showed the highest transmittance variable level compared to Comparative Examples 1 to 3, The haze value in the mode was very low. In addition, referring to FIGS. 2 and 3 , it was confirmed that the liquid crystal cell of Example 1 was able to rapidly implement a change in transmittance even at a low driving voltage of about 40 V, and thus had excellent performance.

Example 1 is a liquid crystal cell using a pressure-sensitive adhesive having a vertical alignment force on the first substrate, and using a vertical alignment film on the second substrate. The pressure-sensitive adhesive having vertical alignment force may induce the liquid crystal to be tilted with a slight angle like the alignment layer has a pretilt angle. For this reason, the liquid crystal cell of Example 1 using a pressure-sensitive adhesive having a vertical alignment force on the first substrate and using a vertical alignment film on the second substrate may implement a blocking state at 0V.

In addition, when a voltage is applied, the twisted liquid crystal and dye molecules are slowly untied and changed to a vertically aligned state. At low voltage, the liquid crystal molecules are in a state of lying obliquely, thereby maximizing the difference in refractive index, resulting in a high haze value. However, when a high voltage is applied, the liquid crystal and dye molecules are aligned perpendicular to the substrate, thereby increasing transmittance and lowering haze. However, the haze value does not fall below a certain value even at 0V due to the spacer and the substrate itself.

Comparative Example 2 and Comparative Example 3 are liquid crystal cells in which a horizontal alignment film is formed on the second substrate in the same manner, but Comparative Example 2 showed a higher level of transmittance variable and a lower haze value than Comparative Example 3. This is thought to be because the pressure-sensitive adhesive (DOW7657) used in Comparative Example 3 has a greater force for horizontally aligning the liquid crystal than the pressure-sensitive adhesive (KR3700) used in Comparative Example 2. That is, it is determined that the strong liquid crystal vertical alignment force of the pressure-sensitive adhesive used in Comparative Example 2 affected the optical properties (transmittance variable level, haze).

101: first substrate
103: adhesive layer or adhesive layer
201: second substrate
203: liquid crystal alignment film
300: liquid crystal layer
400: bulkhead type spacer
500: electrode layer

Claims (13)

a first substrate on which an adhesive layer or an adhesive layer is formed on a first surface; a liquid crystal layer comprising a liquid crystal compound and a chiral dopant; and a second substrate on which a vertical alignment film is formed on the first surface;
The first and second substrates are disposed to face each other so that the first surfaces of each other,
A gap between the first and second substrates is maintained by a barrier rib spacer,
An optical modulation device for switching between a twisted orientation state in which the twist angle A calculated by the following general formula (1) is 860 degrees or more and an orientation state different from the twist orientation state according to the application of a voltage.
[General formula 1]
Twisting angle (A) = a+b×360
In Formula 1, a is the angle formed by the optical axis of the liquid crystal molecules present at the lowermost portion and the optical axis of the liquid crystal molecules present at the uppermost portion in the liquid crystal layer in the twist alignment state, and b is the number of pitches. The optical modulation device of claim 1, wherein an alignment layer is not formed on the first substrate. The light modulation device according to claim 1, wherein an electrode layer is formed between the first surface of the first substrate and the pressure-sensitive adhesive layer or the adhesive layer. The light modulation device of claim 1, wherein the liquid crystal layer is present between the pressure-sensitive adhesive layer or adhesive layer of the first substrate and the vertical alignment layer of the second substrate. The light modulation device according to claim 1, wherein an electrode layer is formed between the first surface of the second substrate and the vertical alignment layer. The optical modulation device according to claim 1, wherein the barrier rib spacer is a honeycomb spacer, a square spacer, or a random spacer. The light modulation device according to claim 1, wherein the barrier-wall spacer includes a cured product of a curable resin composition. The optical modulation device according to claim 1, wherein the ratio (d/p) of the thickness (d) to the pitch (p) of the liquid crystal layer in the twisted alignment state is 2 to 6. The optical device of claim 1 , wherein the liquid crystal layer further comprises a dichroic dye. The optical modulation device of claim 1 , wherein the optical modulation device exists in a twisted orientation state when no voltage is applied, and exists in a vertical orientation state when a voltage is applied. The optical modulation device according to claim 10, wherein the optical modulation device exhibits a minimum transmittance when no voltage is applied and a maximum transmittance when a voltage is applied. The optical modulation device according to claim 1, wherein the voltage at which the haze is less than 10% when the voltage is applied is 40V or less. The optical modulation device according to claim 1, wherein the voltage at which the transmittance is 50% or more when voltage is applied is 40V or less.

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