Optical modulation device

Abstract

In the present application, a light modulation device and use thereof can be provided, which achieves low transmittance in a black mode while having a wide transmittance variable range, and does not cause problems such as liquid crystal defects or visibility degradation.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2020-0082159, filed on July 3, 2020, the disclosure of which is incorporated herein by reference in its entirety.

[0002] This application relates to optical modulation devices and windows. Background Technology

[0003] An optical modulation device is a device capable of switching between at least two or more different states. Such devices are used in a wide range of applications, including wearable devices such as eyeglasses or sunglasses; mobile devices; devices for virtual reality (VR) or augmented reality (AR); and windows for vehicle sunroofs or building windows (so-called smart windows).

[0004] In optical modulation devices, devices using a guest-host liquid crystal system change the light absorption rate of a liquid crystal layer by mixing a dichroic dye, which serves as a guest molecule, with the host molecule in the liquid crystal layer, and by applying a voltage to the liquid crystal to change the arrangement of the host and guest molecules.

[0005] In such guest-host liquid crystal systems, methods to broaden the variable transmittance range (e.g., the ratio of transmittance in the transparent state to transmittance in the blocking state) include increasing the amount of dichroic dye added as a guest molecule. However, known dichroic dyes do not have high solubility in liquid crystal compounds that are host molecules, which limits the ability to broaden the variable transmittance range by increasing the amount of dichroic dye.

[0006] Meanwhile, adding chiral dopants to the host-guest liquid crystal system can be considered to broaden the range of transmittance. However, even with this method, a large amount of chiral dopants must be added to broaden the range of transmittance, which may lead to liquid crystal defects and visibility problems. Summary of the Invention

[0007] Technical issues

[0008] One object of this application is to provide an optical modulation device. Another object of this application is to provide an optical modulation device and its application that does not have liquid crystal defects or visibility degradation while exhibiting a wide range of variable transmittance.

[0009] Technical solution

[0010] Unless otherwise stated, the physical properties mentioned in this specification that affect the results of the measurement by temperature are those measured at room temperature.

[0011] In this specification, the term room temperature refers to the temperature without special heating or cooling, and may mean any temperature in the range of about 10°C to 30°C, such as about 15°C or higher, 18°C ​​or higher, 20°C or higher, or about 23°C or higher and simultaneously about 27°C or lower. Furthermore, unless otherwise stated, the unit of temperature mentioned in this specification is degrees Celsius (°C).

[0012] Unless otherwise stated, the physical properties mentioned in this specification that affect the results of the measurement pressure are the results of measurements taken at normal pressure.

[0013] The term atmospheric pressure is the natural pressure without pressurization or depressurization, which at the level of atmospheric pressure usually means about 1 atmosphere.

[0014] In cases where the physical properties that affect the results of humidity measurements are measured, the relevant physical properties are those measured under natural humidity conditions without special control at room temperature and / or normal pressure.

[0015] In this specification, the terms used to define angles, such as vertical, horizontal, orthogonal, or parallel, mean substantially vertical, horizontal, orthogonal, or parallel to the intended effect, and the range of vertical, horizontal, orthogonal, or parallel includes errors such as manufacturing errors or deviations (variations). For example, each of the foregoing cases may include an error within approximately ±15 degrees, an error within approximately ±10 degrees, or an error within approximately ±5 degrees.

[0016] This application relates to an optical modulation device. The term optical modulation device can refer to a device capable of switching between two or more different optical states. Here, different optical states can refer to states in which at least transmittance, reflectance, color, and / or haze are different.

[0017] The optical modulation apparatus of this application may include a first substrate and a second substrate arranged to face each other, and may further include a liquid crystal layer between the first substrate and the second substrate. Here, the first substrate and the second substrate each have a first surface, wherein the first substrate and the second substrate may be arranged such that their first surfaces face each other. In this application, the terms "first surface of the first substrate" or "first surface of the second substrate" refer to either the first substrate or the second substrate's main surface, and "second surface" refers to a surface of the first substrate or the second substrate opposite to the first surface.

[0018] As described below, a pressure-sensitive adhesive layer or adhesive layer can be formed on the first surface of the first substrate.

[0019] Furthermore, the distance between the first substrate and the second substrate can be maintained by a so-called partition wall spacer.

[0020] Figure 1An exemplary optical modulation apparatus according to one aspect of this application is illustrated. The optical modulation apparatus according to a first example sequentially includes a first substrate 101, a liquid crystal layer 300, and a second substrate 201. The first substrate 101 may have a pressure-sensitive adhesive layer or adhesive layer 103 formed on its first surface. As described below, the liquid crystal layer 300 may contain a liquid crystal compound and a chiral dopant. Figure 1 As shown, a liquid crystal alignment film 203 may be present on the first surface of the second substrate 201. Alternatively, the liquid crystal alignment film 203 may not be present. Figure 1 In the first substrate and the second substrate are arranged opposite each other such that their first surfaces face each other, and the distance G between the first substrate and the second substrate is maintained by a partition wall spacer 400.

[0021] Figure 2 An optical modulation apparatus according to another aspect of this application is illustrated by way of example. Figure 2 The optical modulation device has the same characteristics as Figure 1 The structure is similar to that of the device, but no liquid crystal alignment film is formed on the second substrate 201. Even Figure 2 In the structure, the distance between the first substrate and the second substrate is also maintained by the partition wall spacer 400.

[0022] The optical modulation device of this application can be configured to achieve at least a twisted orientation. Such a twisted orientation can be achieved either in a state where no voltage is applied or in a state where a voltage is applied.

[0023] The liquid crystal layer can be configured to switch between twisted orientations and other orientations. For example, if the twisted orientation is achieved in a state where no voltage is applied, it can be switched to other orientations by applying a voltage, and if the twisted orientation is achieved in a state where a voltage is applied, it can be switched to other orientations in a state where no voltage is applied by removing the voltage.

[0024] In one example, the liquid crystal layer can be configured such that the ratio (d / p) of the thickness (cell gap, d) of the liquid crystal layer in the twisted alignment state to the pitch (p) of the liquid crystal layer is greater than 2.8 and 10 or less. Such a d / p ratio can be adjusted by changing the ratio of chiral dopants present in the liquid crystal layer and the thickness of the liquid crystal layer. A light modulation device with a wide range of variable transmittance and without visibility degradation and liquid crystal defects can be provided by maintaining the distance between liquid crystal layers exhibiting such a d / p using spacer walls.

[0025] In another instance, d / p can be 2.9 or greater, 3 or greater, 3.1 or greater, 3.2 or greater, 3.3 or greater, 3.4 or greater, 3.5 or greater, 3.6 or greater, 3.7 or greater, 3.8 or greater, 3.9 or greater, 4 or greater, 4.1 or greater, 4.2 or greater, 4.3 or greater, 4.4 or greater, 4.5 or greater, 4.6 or greater, 4.7 or greater, or 4.8 or greater, or it can also be 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 5.7 or less, 5.5 or less, 5.4 or less, 5.3 or less, 5.2 or less, 5.1 or less, 5.0 or less, 4.9 or less, 4.7 or less, 4.5 or less, or around 4 or less.

[0026] The optical modulation device of this application can be designed to switch between a transparent mode and a black mode. The switching of the optical modulation device can be adjusted based on the application of an external signal, such as whether a voltage signal is applied. In one example, the black mode can be implemented with the aforementioned twisted orientation, and the transparent mode can be implemented with an orientation different from the twisted orientation.

[0027] The light modulation device of this application may include a structure having two substrates arranged facing each other and a liquid crystal layer positioned between the substrates as a basic unit. This basic unit may also be referred to as a liquid crystal cell. Typically, a liquid crystal alignment film is formed on both surfaces of the first and second substrates facing the liquid crystal layer, but a pressure-sensitive adhesive layer or adhesive layer is formed on the first substrate, thereby obtaining an orientation state of the liquid crystal compound that is very useful in specific applications (e.g., smart windows or eye-wearing devices). Therefore, a liquid crystal alignment film may not be formed on the first substrate of the light modulation device of this application. Furthermore, spacers for maintaining the distance (cell gap) between the first and second substrates are present on either the first or second substrate of the light modulation device, but when a pressure-sensitive adhesive layer or adhesive layer is formed on the first substrate, the pressure-sensitive adhesive layer or adhesive layer can be attached to the spacers to greatly improve the adhesion between the first and second substrates.

[0028] In this specification, the first surface of the substrate refers to either the main surface of the substrate or its opposite surface, and the second surface refers to the other surface of the substrate, either the main surface or its opposite surface. Furthermore, the main surface may refer to the surface of the substrate having the largest area.

[0029] As the first and second substrates, known substrate materials can be used without any particular limitation. For example, inorganic substrates such as glass substrates, crystalline or amorphous silicon substrates, or quartz substrates, or plastic substrates can be used as substrates. As plastic substrates, TAC (triacetyl cellulose) substrates; COP (cyclic olefin copolymer) substrates, such as norbornene derivative substrates; PMMA (poly(methyl methacrylate)) substrates; PC (polycarbonate) substrates; PE (polyethylene) substrates; PP (polypropylene) substrates; PVA (polyvinyl alcohol) substrates; DAC (diacetyl cellulose) substrates; Pac (polyacrylate) substrates; PES (polyethersulfone) substrates; PEEK (polyether ether ketone) substrates; PPS (polyphenyl sulfone), PEI (polyetherimide) substrates; PEN (polyethylene naphthalate) substrates; polyester substrates, such as PET (polyethylene terephthalate) substrates; PI (polyimide) substrates; PSF (polysulfone) substrates; PAR (polyarylate) substrates, or substrates containing amorphous fluoropolymers, etc., but not limited to these. There are no particular restrictions on the thickness of such a substrate; it can be selected within an appropriate range.

[0030] In the optical modulation apparatus of this application, a pressure-sensitive adhesive layer or adhesive layer can be formed on the first surface of the first substrate. In one example, the ratio (percentage) (=100%×A / B) of the area (A) of the pressure-sensitive adhesive layer or adhesive layer formed on the first surface to the area (B) of the first surface can be approximately 50% or greater, 55% or greater, 60% or greater, 65% or greater, 70% or greater, 75% or greater, 80% or greater, 85% or greater, 90% or greater, or 95% or greater. There is no particular upper limit to the ratio (percentage) (=100%×A / B), which can be, for example, approximately 100%.

[0031] The pressure-sensitive adhesive layer or adhesive layer may be optically transparent. The average transmittance of the pressure-sensitive adhesive layer or adhesive layer to the visible light region (e.g., wavelengths from 380 nm to 780 nm) may be about 80% or greater, 85% or greater, 90% or greater, or 95% or greater.

[0032] As the adhesive layer or pressure-sensitive adhesive layer, known materials can be used without any particular limitation; for example, materials known as so-called OCA (optically clear adhesive) or OCR (optically clear resin) can be used. The inventors have demonstrated that such OCA or OCR materials exhibit a certain level of orientation force with respect to liquid crystal compounds, and have confirmed that this orientation force achieves an orientation state highly suitable for specific applications (e.g., smart windows or eye-wearing devices as described above).

[0033] There are no particular limitations on the type of pressure-sensitive adhesive layer or adhesive layer, as long as a pressure-sensitive adhesive or adhesive with strong stain resistance to liquid crystals is used. As mentioned above, various types of pressure-sensitive adhesives known in the industry as so-called OCA (Optically Transparent Adhesive) can be used as pressure-sensitive adhesive layers, characterized by curing before the objects to be attached are bonded. Examples of such pressure-sensitive adhesives include acrylic pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, and urethane-based pressure-sensitive adhesives. Various types of adhesives known in the industry as so-called OCR (Optically Transparent Resin) can be used as adhesive layers, characterized by curing after the objects to be attached are bonded. Such adhesives can be applied to a substrate and semi-cured by heat or UV, and then fully cured by heat or UV after the manufacture of the light modulation device. The pressure-sensitive adhesive layer or adhesive layer can be combined with a liquid crystal alignment film to induce the proper orientation of the liquid crystal compound.

[0034] In one example, the pressure-sensitive adhesive layer or adhesive layer can be a liquid crystal-oriented pressure-sensitive adhesive layer or adhesive layer that simultaneously possesses liquid crystal alignment force and adhesion force to liquid crystal molecules. For example, the pressure-sensitive adhesive or adhesive can be a vertically oriented or horizontally oriented pressure-sensitive adhesive or adhesive. In this specification, a vertically oriented pressure-sensitive adhesive or adhesive can mean a pressure-sensitive adhesive or adhesive that has an adhesion force capable of bonding an upper substrate and a lower substrate, while simultaneously imparting a vertical alignment force to adjacent liquid crystal compounds. In this specification, a horizontally oriented pressure-sensitive adhesive or adhesive can mean a pressure-sensitive adhesive or adhesive that has an adhesion force capable of bonding an upper substrate and a lower substrate, while simultaneously imparting a horizontal alignment force to adjacent liquid crystal compounds.

[0035] The pre-tilt angle of adjacent liquid crystal compounds relative to the vertically oriented pressure-sensitive adhesive or binder can be in the range of 80 to 90 degrees, 85 to 90 degrees, or 87 to 90 degrees, and the pre-tilt angle of adjacent liquid crystal compounds relative to the horizontally oriented pressure-sensitive adhesive or binder can be in the range of 0 to 10 degrees, 0 to 5 degrees, or 0 to 3 degrees. According to one embodiment of this application, a vertically oriented pressure-sensitive adhesive or binder can be used as the pressure-sensitive adhesive or binder.

[0036] In this specification, the pre-tilt angle can refer to the angle formed by the director of the liquid crystal compound relative to a plane horizontal to the liquid crystal alignment pressure-sensitive adhesive or alignment film when no voltage is applied. In this specification, the director of the liquid crystal compound can refer to the optical axis or slow axis of the liquid crystal layer. Alternatively, when the liquid crystal compound is rod-shaped, the director of the liquid crystal compound can refer to the long axis direction; when the liquid crystal compound is disk-shaped, the director of the liquid crystal compound can refer to an axis parallel to the normal direction of the disk's plane. When multiple liquid crystal compounds with different directores exist in the liquid crystal layer, the director can be a vector sum.

[0037] In one example of this application, a silicone-based pressure-sensitive adhesive or binder, for example, can be used as a pressure-sensitive adhesive or binder that exhibits strong stain resistance to liquid crystals and has vertical alignment force. As a silicone-based pressure-sensitive adhesive or binder, a cured product comprising a composition containing a curable silicone compound can be used. Since curable silicone compounds can exhibit vertical alignment capability due to their surface properties, a suitable type can be selected from known silicone pressure-sensitive adhesives or binders. There are no particular limitations on the type of composition containing a curable silicone compound (hereinafter, curable silicone composition), wherein, for example, a thermosetting silicone composition or a UV-curable silicone composition can be used.

[0038] In one example, the curable silicone composition is an addition-curable silicone composition, which may comprise (1) an organopolysiloxane containing two or more alkenyl groups in its molecule and (2) an organopolysiloxane containing two or more hydrogen atoms bonded to silicon in its molecule. Such a silicone compound can, for example, form a cured product through an addition reaction in the presence of a catalyst such as a platinum catalyst.

[0039] More specific examples of (1) organopolysiloxanes that may be used in this application may include dimethylsiloxane-methylvinylsiloxane copolymers capped at both ends of the molecular chain with trimethylsiloxane, methylvinylpolysiloxanes capped at both ends of the molecular chain with trimethylsiloxane, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped at both ends of the molecular chain with trimethylsiloxane, dimethylpolysiloxanes capped at both ends of the molecular chain with dimethylvinylsiloxane, methylvinylpolysiloxanes capped at both ends of the molecular chain with dimethylvinylsiloxane, dimethylsiloxane-methylvinylsiloxane copolymers capped at both ends of the molecular chain with dimethylvinylsiloxane, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped at both ends of the molecular chain with dimethylvinylsiloxane, and those comprising R 1 2SiO 2 / 2 The siloxane unit represented by R and the siloxane unit represented by R 1 2R2 SiO 1 / 2 The siloxane unit represented and the siloxane unit composed of SiO 4 / 2 The organopolysiloxane copolymer representing the siloxane unit, comprising R 1 2R 2 SiO 1 / 2 The siloxane unit represented and the siloxane unit composed of SiO 4 / 2 The organopolysiloxane copolymer representing the siloxane unit, comprising R 1 R 2 SiO 2 / 2 The siloxane unit represented by R and the siloxane unit represented by R 1 SiO 3 / 2 The siloxane unit represented by R or made of 2 SiO 3 / 2 The organopolysiloxane copolymers of the indicated siloxane units, and mixtures of two or more of the foregoing, but not limited thereto.

[0040] Here, R 1 It is a hydrocarbon group other than an alkenyl group, specifically an alkyl group, such as methyl, ethyl, propyl, butyl, pentyl, hexyl or heptyl; an aryl group, such as phenyl, tolyl, xylyl or naphthyl; an aralkyl group, such as benzyl or phenethyl; a halogen-substituted alkyl group, such as chloromethyl, 3-chloropropyl or 3,3,3-trifluoropropyl; and so on.

[0041] Furthermore, here, R 2 It is an alkenyl group, specifically, it can be vinyl, allyl, butenyl, pentenyl, hexenyl or heptenyl, etc.

[0042] More specific examples of (2) organopolysiloxanes that may be used in this application may include methylhydropolysiloxanes with trimethylsiloxane-terminated ends of the molecular chain; dimethylsiloxane-methylhydro copolymers with trimethylsiloxane-terminated ends of the molecular chain; dimethylsiloxane-methylhydrosiloxane-methylphenylsiloxane copolymers with trimethylsiloxane-terminated ends of the molecular chain; dimethylpolysiloxanes with dimethylhydrosiloxane-terminated ends of the molecular chain; dimethylsiloxane-methylphenylsiloxane copolymers with dimethylhydrosiloxane-terminated ends of the molecular chain; methylphenylpolysiloxanes with dimethylhydrosiloxane-terminated ends of the molecular chain; and methylphenylpolysiloxanes containing R 1 3SiO 1 / 2 The siloxane unit represented by R 1 2HSiO 1 / 2 The siloxane unit represented and the siloxane unit composed of SiO 4 / 2 Organopolysiloxane copolymers containing siloxane units; comprising R 1 2HSiO 1 / 2 The siloxane unit represented and the siloxane unit composed of SiO 4 / 2Organopolysiloxane copolymers containing siloxane units; comprising R 1 HSiO 2 / 2 The siloxane unit represented by R and the siloxane unit represented by R 1 SiO 3 / 2 The siloxane unit represented is or is composed of HSiO 3 / 2 The organopolysiloxane copolymer representing the siloxane unit; and mixtures of two or more of the foregoing, but not limited thereto. Here, R 1 It can be a hydrocarbon group other than an alkenyl group. Specifically, it can be an alkyl group, such as methyl, ethyl, propyl, butyl, pentyl, hexyl or heptyl; an aryl group, such as phenyl, tolyl, xylyl or naphthyl; an aralkyl group, such as benzyl or phenethyl; a halogen-substituted alkyl group, such as chloromethyl, 3-chloropropyl or 3,3,3-trifluoropropyl; and so on.

[0043] (2) There is no particular limitation on the content of the organopolysiloxane, as long as it is contained to a degree that allows for proper curing. For example, (2) the organopolysiloxane may be contained in an amount of 0.5 to 10 silicon-bonded hydrogen atoms per alkenyl group contained in (1) the organopolysiloxane as described above. Within such a range, sufficient curing can be achieved and heat resistance can be ensured.

[0044] Addition-curable silicone compositions may also contain platinum or platinum compounds as catalysts for curing. There are no particular limitations on the specific type of platinum or platinum compound. The catalyst ratio can also be adjusted to a level suitable for proper curing.

[0045] Addition-curable silicone compositions may also contain appropriate additives in suitable proportions as needed from the viewpoint of improving storage stability, handling properties and processability.

[0046] In another example, as a condensable curable silicone composition, the silicone composition may comprise, for example, (a) an alkoxy-containing siloxane polymer; and (b) a hydroxyl-containing siloxane polymer.

[0047] (a) The siloxane polymer can be, for example, a compound represented by Formula 1 below.

[0048] [Formula 1]

[0049] R 1 a R 2 b SiO c (OR 3 ) d

[0050] In Equation 1, R 1 and R 2Each independently represents a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, R 3 Represents an alkyl group, wherein when a plurality of R are present... 1 R 2 and R 3 When, they can be the same or different from each other, a and b can each independently represent 0 or greater than 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 equals 4.

[0051] In the definition of Formula 1, the monovalent hydrocarbon can be, for example, an alkyl, phenyl, benzyl, or tolyl group having 1 to 8 carbon atoms, wherein the alkyl group having 1 to 8 carbon atoms can be methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, heptyl, or octyl, etc. Furthermore, in the definition of Formula 1, the monovalent hydrocarbon group can be substituted with known substituents such as halogen, amino, mercapto, isocyanate, glycidyl, glycidoxy, or urea groups.

[0052] Under the constraints of Equation 1, R 3 Examples of alkyl groups may include methyl, ethyl, propyl, isopropyl, or butyl, etc. Among these alkyl groups, methyl or ethyl are commonly used, but are not limited to these.

[0053] In the polymer of Formula 1, branched or tertiary crosslinked siloxane polymers can be used. Furthermore, in this (a) siloxane polymer, hydroxyl groups may remain to a extent that does not impair the purpose, specifically, to a extent that does not inhibit the dealcoholization reaction.

[0054] (a) Siloxane polymers can be produced, for example, by hydrolysis and condensation of polyfunctional alkoxysilanes or polyfunctional chlorosilanes. Those skilled in the art can readily select suitable polyfunctional alkoxysilanes or chlorosilanes according to the desired (a) siloxane polymer, and can also readily control the conditions of the hydrolysis and condensation reactions using them. Simultaneously, in the production of (a) siloxane polymers, suitable monofunctional alkoxysilanes can also be used in combination, depending on the purpose.

[0055] As (a) a siloxane polymer, for example, commercially available organosiloxane polymers such as Shin-Etsu Silicone's X40-9220 or X40-9225; or GE Toray Silicone's XR31-B1410, XR31-B0270 or XR31-B2733 can be used.

[0056] As a condensable curable silicone composition, (b) a hydroxyl-containing siloxane polymer may be used, for example, a compound represented by Formula 2 below.

[0057] [Equation 2]

[0058]

[0059] In Equation 2, R4 and R5 each independently represent a hydrogen atom or a substituted or unsubstituted monovalent hydrocarbon group, wherein when there are multiple R4s and R5s, they may be the same or different from each other, and n represents an integer from 5 to 2000.

[0060] In the definition of Formula 2, the specific type of monovalent hydrocarbon group may include, for example, the same hydrocarbon group as in Formula 1 above.

[0061] (b) Siloxane polymers can be produced, for example, by hydrolysis and condensation of dialkoxysilanes and / or dichlorosilanes. Those skilled in the art can readily select suitable dialkoxysilanes or dichlorosilanes according to the desired (b) siloxane polymer, and can also readily control the conditions of the hydrolysis and condensation reactions using them. As the above (b) siloxane polymers, commercially available bifunctional organosiloxane polymers can be used, such as GE Toray Silicone's XC96-723, YF-3800, or YF-3804, etc.

[0062] There are no particular limitations on the type of pressure-sensitive adhesive or binder with vertical orientation force, which can be appropriately selected according to the desired application. For example, solid pressure-sensitive adhesives or binders, semi-solid pressure-sensitive adhesives or binders, elastic pressure-sensitive adhesives or binders, or liquid pressure-sensitive adhesives or binders can be appropriately selected and used. Solid pressure-sensitive adhesives, semi-solid pressure-sensitive adhesives, or elastic pressure-sensitive adhesives can be referred to as pressure-sensitive adhesives (PSA), which can cure before the bonded objects are bonded. In this application, for example, polydimethylsiloxane pressure-sensitive adhesives or polymethylvinylsiloxane pressure-sensitive adhesives can be used as PSA-type pressure-sensitive adhesives with vertical orientation force, and alkoxy silicone adhesives can be used as OCR-type adhesives with vertical orientation force, but are not limited thereto.

[0063] There are no particular limitations on the thickness of the pressure-sensitive adhesive layer or adhesive layer; it can be selected within an appropriate range to ensure the desired adhesion. The thickness can range from about 1 μm to 50 μm. In another example, the thickness can be 2 μm or greater, 3 μm or greater, 4 μm or greater, 5 μm or greater, 6 μm or greater, 7 μm or greater, 8 μm or greater, 9 μm or greater, or 10 μm or greater, or it can also be 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, or about 10 μm or less.

[0064] By including a pressure-sensitive adhesive layer or an adhesive layer in the above arrangement, a light modulation device can be provided that exhibits excellent optical properties while controlling light leakage (especially in black mode) and having excellent adhesion.

[0065] In an optical modulation apparatus, a liquid crystal alignment film may or may not be formed on a first surface of a second substrate (the surface facing the first surface of the first substrate). When a liquid crystal alignment film is formed, the type of alignment film formed on the first surface of the second substrate is not particularly limited. That is, as the alignment film, known vertical alignment films, horizontal alignment films, or other alignment films can be applied considering the desired initial orientation. Regarding the type of alignment film, contact alignment films (e.g., rubbing alignment films) or non-contact alignment films (e.g., photoalignment films) can be applied.

[0066] The liquid crystal layer may exist between the pressure-sensitive adhesive layer of the first substrate or between the adhesive layer and the alignment film of the second substrate. The liquid crystal layer is a functional layer capable of changing its transmittance, reflectance, haze, and / or color, individually or in combination with other components, depending on whether an external signal is applied. In this specification, an external signal may refer to an external factor, such as an external voltage, that can affect the behavior of materials (e.g., light-modulating materials) contained in the liquid crystal layer. Therefore, a state in which no external signal is applied may mean a state in which no external voltage, etc., is applied.

[0067] A liquid crystal layer is a layer containing a liquid crystal compound. As described below, a so-called host-guest layer containing a liquid crystal compound (liquid crystal host) and a dichroic dye, or a layer containing a liquid crystal compound and other additives such as chiral dopants, are also types of liquid crystal layers specified in this specification. The liquid crystal compound can be present in the liquid crystal layer such that its orientation direction changes depending on whether an external signal is applied. Any type of liquid crystal compound can be used as the liquid crystal compound, as long as its orientation direction can be changed by applying an external signal.

[0068] The liquid crystal layer may contain a liquid crystal compound having positive or negative dielectric anisotropy. The absolute value of the dielectric anisotropy of the liquid crystal can be appropriately selected in consideration of the purposes of this application. The term dielectric anisotropy (Δε) may refer to the difference (ε / / -ε⊥) between the horizontal dielectric constant (ε / / ) and the vertical dielectric constant (ε⊥). In this specification, the term horizontal dielectric constant (ε / / ) means the dielectric constant measured along the direction of the electric field when a voltage is applied such that the direction of the liquid crystal's director and the direction of the electric field through the applied voltage are substantially horizontal, and the term vertical dielectric constant (ε⊥) means the dielectric constant measured along the direction of the electric field when a voltage is applied such that the direction of the liquid crystal's director and the direction of the electric field through the applied voltage are substantially perpendicular.

[0069] To achieve the aforementioned d / p ratio, the liquid crystal layer can contain chiral dopants and liquid crystal compounds (or liquid crystal molecules). The d / p ratio can be adjusted by regulating the content of the chiral dopants and the thickness (cell gap) of the liquid crystal layer.

[0070] As chiral dopants included in the liquid crystal layer, known compounds can be used without any particular limitation. Chiral dopants can be used without any particular limitation, as long as they can induce the desired twisting without impairing the liquid crystal properties, such as nematic regularity. Chiral dopants used to induce rotation in liquid crystal molecules need to include at least chirality in their molecular structure. Examples of chiral dopants include, for example, compounds having one or two or more asymmetric carbons; compounds having asymmetric sites on heteroatoms, such as chiral amines or chiral sulfoxides; or compounds having axial asymmetry and optically active sites, such as cumulative polyenes or binatol. Chiral dopants can be, for example, low molecular weight compounds having a molecular weight of 1,500 or less. Commercially available chiral nematic liquid crystals can also be used as chiral dopants, such as the chiral doped liquid crystal S811 from Merck Co., Ltd. or LC756 from BASF.

[0071] The content of chiral dopant in the liquid crystal layer can be appropriately selected in consideration of the purpose of this application. For example, the content of chiral dopant in the liquid crystal layer can 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, 1.5 wt% or more, 2 wt% or more, 2.5 wt% or more, or 2.7 wt% or more. The upper limit of the content of chiral dopant in the liquid crystal layer can be, for example, 10 wt% or less, 9 wt% or less, 8 wt% or less, 7 wt% or less, 6 wt% or less, 5.0 wt% or less, 4.0 wt% or less, 3.5 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 chiral dopant in the liquid crystal layer meets the above range, an optical modulation device with excellent variable transmittance characteristics can be provided.

[0072] Choosing the appropriate application ratio of chiral dopants allows for the achievement of a d / p ratio. Typically, the chiral dopant content (wt%) can be calculated using the formula 100 / HTP (helical twisting power) × pitch (p) (nm). HTP represents the twisting strength of the chiral dopant, and the chiral dopant content can be determined by considering the desired pitch using the method described above.

[0073] In terms of adjusting the variable transmittance, the liquid crystal layer may also include dichroic dyes and liquid crystal compounds. As described above, such a liquid crystal layer can be referred to as a guest-host liquid crystal layer. In this specification, "dye" can mean a material capable of strongly absorbing and / or altering light in at least part or all of the visible light region, such as the wavelength range of 400 nm to 700 nm. The term "dichroic dye" can mean a material capable of anisotropically absorbing light in at least part or all of the visible light region. In this specification, the term "GHLC layer (guest-host liquid crystal layer)" can mean a functional layer in which dichroic dyes are arranged together according to the liquid crystal alignment, thereby exhibiting anisotropic light absorption characteristics relative to the alignment direction of the dichroic dyes and in a direction perpendicular to the alignment direction. For example, a dichroic dye is a substance whose light absorption rate varies with the polarization direction. If the absorption rate of light polarized in the long axis direction is large, it can be called a p-type dye; if the absorption rate of light polarized in the short axis direction is large, it can be called an n-type dye. In one instance, when using a p-type dye, polarized light vibrating along the dye's long axis can be absorbed, while polarized light vibrating along the dye's short axis can be less absorbed and transmitted. In the following text, unless otherwise stated, dichroic dyes are considered p-type dyes.

[0074] As dichroic dyes, for example, known dyes that are known to align according to the alignment state of the liquid crystal compound via the so-called host-guest effect can be selected and used. Examples of such dichroic dyes include azo dyes, anthraquinone dyes, methylene dyes, azomethyl base dyes, cyanine dyes, naphthoquinone dyes, tetraazine dyes, phenylene dyes, tetranaphthalene-triphenylene dyes, benzothiadiazole dyes, diketopyrrolopyrrole dyes, squaric acid cyanine dyes, or pyrrole methylbenzene dyes, but the dyes applicable in this application are not limited to the foregoing.

[0075] As dichroic dyes, dyes with a dichroism ratio (i.e., a value obtained by dividing the absorption of polarized light parallel to the long axis of the anisotropic dye by the absorption of polarized light parallel to the direction perpendicular to the long axis) of 5 or greater, 6 or greater, or 7 or greater can be used. The dye can satisfy the said dichroism ratio at at least a portion of the wavelengths, or any 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 dichroism ratio can be, for example, about 20 or less, 18 or less, 16 or less, or about 14 or less.

[0076] The content of dichroic dyes in the liquid crystal layer can be appropriately selected to suit the purposes of this application. For example, the content of dichroic dyes in the liquid crystal layer can be 0.1% by weight or more, 0.25% by weight or more, 0.5% by weight or more, 0.75% by weight or more, 1% by weight or more, 1.25% by weight or more, 1.5% by weight or more, 2% by weight or more, 2.5% by weight or more, or 2.7% by weight or more. The upper limit of the content of dichroic dyes in the liquid crystal layer can be, for example, 10% by weight or less, 9% by weight or less, 8% by weight or less, 7% by weight or less, 6% by weight or less, 5.0% by weight or less, 4.0% by weight or less, 3.5% by weight or less, 3.0% by weight or less, 2.75% by weight or less, 2.5% by weight or less, 2.25% by weight or less, 2.0% by weight or less, 1.75% by weight or less, or 1.5% by weight or less. When the content of dichroic dyes in the liquid crystal layer meets the above range, an optical modulation device with excellent variable transmittance characteristics can be provided. In one example, as the content of dichroic dyes increases within the above range, an optical modulation device with excellent variable transmittance characteristics can be provided.

[0077] The type and physical properties of the liquid crystal compound can be appropriately selected in consideration of the purpose of this application. In one example, the liquid crystal molecules can be nematic liquid crystals or smectic liquid crystals. Nematic liquid crystals can refer to liquid crystals in which, although their positions are not regular, the rod-shaped liquid crystal molecules are arranged parallel to each other along the long axis of the liquid crystal molecules. Smectic liquid crystals can refer to liquid crystals in which the rod-shaped liquid crystal molecules are regularly arranged to form a layered structure and are regularly parallel to each other along the long axis. According to one example of this application, nematic liquid crystals can be used as liquid crystal molecules.

[0078] In one instance, the liquid crystal molecule can be a non-reactive liquid crystal molecule. A non-reactive liquid crystal molecule can be defined as a liquid crystal molecule that does not have any polymerizable groups. Here, polymerizable groups can be exemplified as acryloyl, acryloyloxy, methacryl, methacryloyloxy, carboxyl, hydroxyl, vinyl, or epoxy groups, etc., but are not limited thereto, and can include known functional groups known to be polymerizable groups.

[0079] The refractive index anisotropy of the liquid crystal molecules can be appropriately selected by considering desired physical properties, such as variable transmittance characteristics. In this specification, the term refractive index anisotropy can refer to the difference between the unusual and ordinary refractive indices of the liquid crystal molecules. The refractive index anisotropy of the liquid crystal molecules can be, for example, from 0.01 to 0.3. The refractive index anisotropy can be 0.01 or greater, 0.05 or greater, or 0.07 or greater, and can 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, an optical modulation device with excellent variable transmittance characteristics can be provided. In one example, as the refractive index of the liquid crystal molecules decreases within the above range, an optical modulation device with excellent variable transmittance characteristics can be provided.

[0080] Considering the driving method of the target liquid crystal cell, the dielectric anisotropy of the liquid crystal molecules can be positive or negative. In this specification, the term dielectric anisotropy can refer to the difference between the unusual dielectric constant (εe) and the ordinary dielectric constant (εo) of the liquid crystal molecules. The dielectric anisotropy of the liquid crystal molecules can, for example, be within a range of ±40, ±30, ±10, ±7, ±5, or ±3. Controlling the dielectric anisotropy of the liquid crystal molecules within these ranges can be advantageous in terms of the driving efficiency of the optical modulation element.

[0081] The total weight of the liquid crystal molecules and dichroic dyes in the liquid crystal layer can be, 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% by weight or more, 90% by weight or more, or 95% by weight or more. In another example, it can be less than about 100% by weight, 98% by weight or less, or 96% by weight or less.

[0082] The liquid crystal layer can switch its alignment state depending on whether a voltage is applied. For example, a voltage can be applied in a direction perpendicular to the first and second substrates.

[0083] In one example, the liquid crystal layer can exist in a twisted state when no voltage is applied, and in a vertically aligned state when a voltage is applied. In the twisted alignment state, the twist angle can be, for example, greater than 500 degrees. Such a liquid crystal cell can be called an HTN (highly twisted nematic) driven mode liquid crystal cell. The upper limit of the twist angle can be, for example, 3000 degrees or less. In this specification, the twist angle can be calculated using the following general formula 1.

[0084] [General Form 1]

[0085] Twist angle (A) = a + b × 360°

[0086] In the above general formula 1, a is the angle formed by the optical axis of the liquid crystal molecule at the bottom and the optical axis of the liquid crystal molecule at the top in the twisted orientation state, and b is the number of pitches.

[0087] According to one example of this application, the torsion angle can be approximately 550 degrees or greater, 600 degrees or greater, 650 degrees or greater, 700 degrees or greater, 750 degrees or greater, 800 degrees or greater, 850 degrees or greater, 900 degrees or greater, 950 degrees or greater, 1000 degrees or greater, 1120 degrees or greater, 1240 degrees or greater, 1360 degrees or greater, 1480 degrees or greater, 1600 degrees or greater, 1720 degrees or greater, or 1840 degrees or greater. The lower limit of the torsion angle can be approximately 2900 degrees or less, 2800 degrees or less, 2700 degrees or less, 2600 degrees or less, 2500 degrees or less, 2400 degrees or less, 2300 degrees or less, 2200 degrees or less, 2160 degrees or less, 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.

[0088] By applying the HTN liquid crystal driving mode, this application can provide an optical modulation device that achieves excellent variable transmittance levels while realizing low transmittance.

[0089] In a twisted alignment liquid crystal layer, the liquid crystal molecules can have a helical structure in which the optical axis is twisted along a virtual helical axis while being aligned within the layer. The optical axis of the liquid crystal molecule can refer to the slow axis of the liquid crystal molecule, which can be parallel to the long axis of the rod-shaped liquid crystal molecule. The helical axis can be formed parallel to the thickness direction of the liquid crystal layer. In this specification, the thickness direction of the liquid crystal layer can refer to a direction parallel to the virtual line connecting the lowermost and uppermost parts of the liquid crystal layer with the shortest distance. In one example, the thickness direction of the liquid crystal layer can be a direction parallel to the virtual line formed in a direction perpendicular to the surface of the polymer substrate.

[0090] The ratio (d / p) of the thickness (d) to the pitch (p) of the liquid crystal layer in the twisted alignment state can exceed 2.8. When the ratio (d / p) exceeds 2.8, the liquid crystal layer can exist in a twisted state when no voltage is applied, and the twist angle of the liquid crystal molecules in the liquid crystal layer in this twisted alignment state can be 860 degrees or greater. Such a liquid crystal cell can be called an HTN (Highly Twisted Nematic) driven mode liquid crystal cell. Furthermore, when the ratio (d / p) is 2.8 or smaller, an increase in initial transmittance occurs, which may prevent the achievement of the low transmittance objective of this application; therefore, the above range is preferred.

[0091] When the ratio (d / p) of the thickness (d) of the liquid crystal layer to the pitch (p) exceeds 10, the driving voltage increases, so the upper limit of the ratio (d / p) can be adjusted to 10 or less. In another instance, d / p can be 2.9 or greater, 3 or greater, 3.1 or greater, 3.2 or greater, 3.3 or greater, 3.4 or greater, 3.5 or greater, 3.6 or greater, 3.7 or greater, 3.8 or greater, 3.9 or greater, 4 or greater, 4.1 or greater, 4.2 or greater, 4.3 or greater, 4.4 or greater, 4.5 or greater, 4.6 or greater, 4.7 or greater, or 4.8 or greater, or it can also be 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 5.7 or less, 5.5 or less, 5.4 or less, 5.3 or less, 5.2 or less, 5.1 or less, 5.0 or less, 4.9 or less, 4.7 or less, 4.5 or less, or approximately 4 or less.

[0092] The thickness (d) of the liquid crystal layer can have the same meaning as the cell gap. In this application, the thickness (d) of the liquid crystal layer can be in the range of 0.1 μm to 50 μm. In another example, it can be 0.5 μm or greater, 1 μm or greater, 2 μm or greater, 3 μm or greater, 4 μm or greater, 5 μm or greater, 6 μm or greater, 7 μm or greater, 8 μm or greater, 9 μm or greater, 10 μm or greater, 11 μm or greater, or 11.5 μm or greater, or it can be 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.

[0093] The pitch (p) of the liquid crystal layer can be measured using a wedge cell measurement method, specifically, by the method described in 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, pp. 789-791).

[0094] As mentioned above, the ratio (d / p) can be achieved by adjusting the thickness of the liquid crystal layer and the content of chiral dopants in the liquid crystal layer.

[0095] In host-guest liquid crystal systems using conventional spherical spacers, liquid crystal defects occur when applying HTN liquid crystal driving mode to achieve low transmittance, leading to visibility problems. Reducing the chiral dopant content to address the visibility issue increases transmittance in the black state, potentially making it impossible to achieve low transmittance.

[0096] In the optical modulation device of this application, a structure is applied that simultaneously uses a pressure-sensitive adhesive layer or an adhesive layer and a spacer wall as described below. This prevents liquid crystal defects from occurring in the HTN liquid crystal driving mode and allows for an increase in the chiral dopant content to reduce the pitch, thereby increasing the absorption of transmitted light and enabling the optical modulation device to effectively achieve both transparent and black states.

[0097] In the optical modulation device of this application, the distance between the first substrate and the second substrate can be maintained by a partition wall spacer. The partition wall spacer can be a cellular partition wall spacer, a quadrilateral partition wall spacer, a triangular partition wall spacer, or a random spacer.

[0098] Here, honeycomb spacers, rectangular spacers, or triangular spacers refer to cases where, when viewed in the direction normal to the substrate, the shape formed by the spacers is honeycomb, quadrilateral, or triangular, as is known. Typically, the honeycomb shape can be a combination of regular hexagons, and the quadrilaterals can be squares, rectangles, or a combination of squares and rectangles. In the above structures, the hexagons, quadrilaterals, or triangles can be regular hexagons, squares, or equilateral triangles, or they may not be regular hexagons, squares, or equilateral triangles.

[0099] Furthermore, here, random spacing refers to the case where the partition walls are randomly arranged, meaning that the partition walls do not form a pattern, or even if they do form a pattern, the pattern is formed randomly rather than a standard pattern.

[0100] The spacing (P) of the partition wall spacers can be appropriately selected by considering factors such as the desired adhesion force or the unit gap retention efficiency.

[0101] For example, the spacing P of the spacers in the partition walls can range from 100 μm to 1,000 μm. In another example, the spacing can be 150 μm or greater, 200 μm or greater, 250 μm or greater, 300 μm or greater, 350 μm or greater, 400 μm or greater, 450 μm or greater, 500 μm or greater, or 550 μm or greater, or it can also be 950 μm or less, 900 μm or less, 850 μm or less, 800 μm or less, 750 μm or less, 700 μm or less, 650 μm or less, 600 μm or less, 550 μm or less, 500 μm or less, 450 μm or less, or 300 μm or less. Methods for obtaining the spacing in the spacers in the partition walls are well known. For example, if the partition wall spacers are honeycomb-shaped, the spacing is obtained by the intervals between the facing edges of the hexagons constituting the honeycomb. If the partition wall spacers are quadrilaterals or triangles, the length of the side of the quadrilateral or triangle is set as the spacing. When the intervals between the facing edges of the hexagons constituting the honeycomb or the length of the side of the quadrilateral or triangle are not constant, their average value can be defined as the spacing. Furthermore, when the partition wall spacers are random, the average value of the intervals between each partition wall (average spacing) can be defined as the spacing.

[0102] The linewidth of the spacers, for example, the width of each side of a quadrilateral or a hexagon constituting a honeycomb, can range, for example, from about 5 μm to 50 μm. In another example, the linewidth can be about 10 μm or more, 15 μm or more, 20 μm or more, or 25 μm or more, or it can be 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.

[0103] Within this range, the inter-unit spacing can be maintained appropriately, and the adhesion between substrates can be maintained excellently.

[0104] Simultaneously, the height of the spacer can be adjusted by considering the distance between the upper and lower substrates. In this application, the height of the spacer is approximately consistent with the thickness of the liquid crystal layer (cell gap), and refers to the size of the spacer measured in the normal direction of the substrate surface. For example, the height of the spacer can range from 0.1 μm to 50 μm. In another example, it can be 1 μm or greater, 2 μm or greater, 3 μm or greater, 4 μm or greater, 5 μm or greater, 6 μm or greater, 7 μm or greater, or 8 μm or greater, or it can be 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. In this case, when the height of the spacer is not constant, the height can be the measured maximum height or minimum height, or the average of the maximum height and the minimum height.

[0105] In this application, the spacers can be manufactured using conventional methods for producing spacers in the form of partition walls. Typically, spacers in the form of partition walls can be manufactured using methods (e.g., embossing) with curable resin compositions. Therefore, the spacers of this application can contain cured products of curable resin compositions. Known types of curable resin compositions used for spacer formation can be used without any particular limitation. Such resin compositions typically include thermosetting resin compositions or photocurable resin compositions, such as UV-curable resin compositions.

[0106] As a thermosetting resin composition, for example, silicone resin compositions, furan resin compositions, polyurethane resin compositions, epoxy resin compositions, amino resin compositions, phenolic resin compositions, urea resin compositions, polyester resin compositions, or melamine resin compositions can be used, but are not limited thereto.

[0107] As a UV-curable resin composition, resin compositions typically comprising, but not limited to, acrylic polymers, such as polyester acrylate polymers, polystyrene acrylate polymers, epoxy acrylate polymers, polyurethane acrylate polymers, or polybutadiene acrylate polymers, silicone acrylate polymers, or alkyl acrylate polymers, can be used. In another example, silicone polymers can also be used to form spacers. When silicone polymers are used to form spacers, the silicone polymer retained in the concave regions of the spacers can serve as a vertical alignment film, such that, as described below, no additional vertical alignment film needs to be used on the substrate in which the spacers are present. As silicone polymers, known polymers having silicon-oxygen bonds (Si-O-Si) as the main axis can be used, such as polydimethylsiloxane (PDMS), but not limited to, but not limited to.

[0108] By controlling the shape, arrangement, and / or arrangement method of the spacers as described above, this application can provide a light modulation device that minimizes liquid crystal defects and has improved visibility while properly maintaining cell gaps and having excellent adhesion between the upper and lower film substrates.

[0109] To achieve the above effects, the relationship between the spacers and the liquid crystal layer can be adjusted. For example, in a light modulation device, the ratio (p1 / d) of the spacing (p1) of the spacers to the thickness (d) of the liquid crystal layer can be in the range of 10 to 100. In another example, this ratio can be 15 or greater, 20 or greater, 25 or greater, 30 or greater, 35 or greater, 40 or greater, 45 or greater, 50 or greater, or 55 or greater, or it can also be 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 or less, 60 or less, 55 or less, 50 or less, 45 or less, or around 40 or less.

[0110] Furthermore, in the optical modulation apparatus, the ratio (p1 / p) of the spacing (p1) of the spacers to the pitch (p in the twisted orientation state) of the liquid crystal layer can be in the range of 50 to 500. In another example, this ratio can be 60 or greater, 70 or greater, 80 or greater, 90 or greater, 100 or greater, 110 or greater, 120 or greater, 130 or greater, 140 or greater, 150 or greater, 160 or greater, 170 or greater, 180 or greater, 190 or greater, 200 or greater, or 210 or greater, or it can also be around 450 or less, 400 or less, 350 or less, 300 or less, 250 or less, 200 or less, or 190 or less.

[0111] Within this range, the desired performance of the optical device can be ensured more effectively.

[0112] like Figure 1 and Figure 2 As shown, the optical modulation device of this application may further include an electrode layer 500 on one side of each of the first substrate and the second substrate, as long as it does not impair the effect of this application. In one example, each electrode layer 500 may be formed between the first surface of the first substrate and the pressure-sensitive adhesive layer or adhesive layer and / or between the first surface of the second substrate and the alignment film.

[0113] An electrode layer can apply an appropriate electric field to the liquid crystal layer, thereby switching the alignment state of the liquid crystal molecules. The direction of the electric field can be vertical or horizontal, such as the thickness direction or planar direction of the liquid crystal layer.

[0114] The electrode layer can be, for example, a transparent conductive layer. A transparent conductive layer can be formed by depositing, for example, conductive polymers, conductive metals, conductive nanowires, or metal oxides such as ITO (indium tin oxide). Furthermore, various materials and methods for forming transparent conductive layers are known and can be used without limitation.

[0115] The optical modulation device of this application may include other additional components as needed. That is, depending on the driving mode, even using only the optical modulation device with the above structure, the above-described transparent mode and black mode, as well as the switching between them, can be realized. However, in order to facilitate the realization or switching of these modes, additional components may be included.

[0116] For example, the device may further include a polarizing layer on a second surface of a first substrate and / or a second substrate. The term polarizing layer can refer to an element that converts natural or unpolarized light into polarized light. In one example, the polarizing layer may be a linear polarizing layer. A linear polarizing layer means that the light selectively transmitted is linearly polarized light vibrating in either direction, and the light selectively absorbed or reflected is linearly polarized light vibrating in a direction orthogonal to the vibration direction of the linearly polarized light. That is, the linear polarizing layer may have a transmission axis and an absorption axis or reflection axis orthogonal to each other in a planar direction.

[0117] The polarizing layer can be an absorptive polarizing layer or a reflective polarizing layer. As an absorptive polarizing layer, for example, a polarizing layer in which iodine is dyed onto a polymer stretched film such as a PVA stretched film, or a host-guest polarizing layer in which liquid crystal polymerized in an oriented state is used as the host and dichroic dyes aligned along the orientation of the liquid crystal are used as guests, is not limited to these. As a 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), is not limited to these.

[0118] However, in one instance, the optical modulation device may not include a polarizing layer.

[0119] When no voltage is applied, the aforementioned optical modulation device can exist in a twisted orientation state to exhibit minimum transmittance, and when a voltage is applied, it can exist in a perpendicular alignment state to exhibit maximum transmittance.

[0120] The transmittance of the optical modulation device in the transparent mode state exhibiting maximum transmittance can be at least 20% or greater, 21% or greater, 22% or greater, 23% or greater, 24% or greater, 25% or greater, 26% or greater, 27% or greater, 28% or greater, 29% or greater, 30% or greater, 31% or greater, 32% or greater, 33% or greater, 34% or greater, 35% or greater, 40% or greater, 45% or greater, 50% or greater, 55% or greater, 60% or greater, 65% or greater, 70% or greater, or approximately 80% or greater. The transmittance of the light modulation device in the black mode state exhibiting minimum transmittance can be 10% or less, 9% or less, 8% or less, 7% or less, 6% 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.

[0121] Higher transmittance in transparent mode is more advantageous, while lower transmittance in black mode is more advantageous. Therefore, there are no particular restrictions on the upper limit of transmittance in transparent mode and the lower limit of transmittance in black mode. In one example, the upper limit of transmittance in transparent mode can be approximately 100%, and the lower limit of transmittance in black mode can be approximately 0%.

[0122] In one instance, the optical modulation device of this application can achieve the aforementioned transmittance without a polarizing layer.

[0123] In one example, the difference between the transmittance in the transparent mode and the transmittance in the black mode of the optical modulation device (transparent mode - black mode) can be 25% or greater, 26% or greater, 27% or greater, 28% or greater, 29% or greater, 30% or greater, 35% or greater, or 40% or greater. Furthermore, it can also be 90% or less, 85% or less, 80% or less, 75% or less, 70% or less, 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 44% or less, 43% or less, 42% or less, 41% or less, 40% or less, 39% or less, 38% or less, 37% or less, 36% or less, 35% or less, 34% or less, 33% or less, 32% or less, or 31% or less.

[0124] This application provides an optical modulation device that achieves low transmittance in the aforementioned black mode state while possessing an excellent variable transmittance level (the difference between transmittance in the transparent state and transmittance in the black mode state).

[0125] The aforementioned transmittance can be the transmittance measured by the method described in the embodiments described below.

[0126] The aforementioned transmittance and reflectance can be transmittance or reflectance for any wavelength in the visible light region, such as about 400 nm to 700 nm or about 380 nm to 780 nm, or they can be transmittance or reflectance for the entire visible light region, or they can be the maximum or minimum transmittance or reflectance for the entire visible light region, or they can be the average transmittance or reflectance in the visible light region.

[0127] Such light modulation devices can be applied to a variety of applications. Applications that can utilize light modulation devices include, but are not limited to, windows used as glass in buildings or sunroofs in vehicles. Examples include: openings in enclosed spaces such as buildings, containers, or vehicles (e.g., glass or sunroofs), eye-wearing devices, windows and doors, light-blocking panels for OLEDs (organic light-emitting devices), etc. Within the scope of eye-wearing devices, this can include all eye-wearing devices configured to allow an observer to see the outside through lenses, such as ordinary glasses, sunglasses, sports goggles or helmets, or wearable devices such as those used for experiencing virtual reality or augmented reality.

[0128] Typical applications that can be made using the light modulation device of this application may include vehicle sunroofs. In one example, the light modulation device itself may be a vehicle sunroof. For example, in a vehicle including a body in which at least one or more openings are formed, a light modulation device or a vehicle sunroof mounted on the openings may be installed and used.

[0129] A sunroof is a fixed or operable (ventilated or sliding) opening on the roof of a vehicle, and can be generally referred to as any device that allows light or fresh air to enter the interior of the vehicle. In this application, there are no particular limitations on the method of operating the sunroof; for example, it can be manually operated or motor-driven, and the shape, size, or style of the sunroof can be appropriately selected according to its intended use. For example, depending on the method of operation, a sunroof can be exemplified as a pop-up sunroof, a spoiler (flat and sliding) sunroof, a built-in sunroof, a folding sunroof, a roof-mounted sunroof, a panoramic roof system sunroof, a removable roof panel (T-roof or Targa-roof) sunroof, or a solar sunroof, but is not limited to these.

[0130] The exemplary skylight of this application may include the light modulation device of this application, in which case the details of the light modulation device may be equivalently applied to the content described in the project on the light modulation device.

[0131] Beneficial effects

[0132] In this application, an optical modulation device and its use can be provided, which achieves low transmittance in black mode while having a wide range of variable transmittance, and does not cause problems such as liquid crystal defects or visibility degradation. Attached Figure Description

[0133] Figure 1 and Figure 2 This is a schematic diagram of the structure of an exemplary optical modulation device.

[0134] Figure 3 This is an optical photograph used to determine the liquid crystal defects in the optical modulation device of Comparative Example 1.

[0135] Figure 4 These are optical photographs used to determine liquid crystal defects in the optical modulation device of Example 1.

[0136] Figure 5 These are optical photographs used to determine liquid crystal defects in the optical modulation device of Embodiment 2.

[0137] Figure 6 and Figure 7 This is a graph related to the evaluation of the thickness (cell gap) of liquid crystal cells. Detailed Implementation

[0138] The present application will be described in more detail below by way of embodiments and comparative examples, but the scope of the present application is not limited to the following embodiments.

[0139] 1. Evaluation of the thickness (cell gap) of liquid crystal cells

[0140] The thickness of the liquid crystal cells, i.e., the cell gap, is measured using a spectrometer in the following manner. For example... Figure 6 As shown, using light (I) I Irradiate one side of a liquid crystal cell with a cell gap (d) and measure the light transmitted from the other side (I). T When irradiated with light, the irradiation angle is parallel to the normal direction of the virtual surface of the transmittance-variable layer. When the transmittance for each wavelength is examined in this way, constructive interference, etc., can yield results such as... Figure 7 The transmittance diagram is shown. Figure 7 In the diagram, the X-axis represents wavelength (nm), and the Y-axis represents transmittance (%). For example... Figure 7 The obtained graph has the following relationship with the cell gap (d) as the thickness of the transmittance variable layer, as shown by the following equation E, where κ is... Figure 7 The number of peaks existing between wavelengths λ1 and λ2. That is, according to... Figure 7 The obtained graph shows that the cell gap (d) can be obtained by obtaining the number of peaks (κ) between wavelengths λ1 and λ2 and substituting wavelengths λ1 and λ2 into Equation E.

[0141] [Formula E]

[0142]

[0143] Example 1

[0144] In a PET (polyethylene terephthalate) film (first substrate) having an ITO (indium tin oxide) layer with a thickness of about 30 nm and a thickness of about 125 μm deposited on its first surface, an organosilicon pressure-sensitive adhesive layer is formed on the ITO layer. The pressure-sensitive adhesive layer is formed to a thickness of about 10 μm by applying a rod of an organosilicon pressure-sensitive adhesive composition (Shinetsu, KR3700) known as an OCA (optically transparent adhesive) onto the ITO layer and drying it at about 150°C for 5 minutes.

[0145] In a PET (polyethylene terephthalate) film (second substrate) having an ITO (indium tin oxide) layer with a thickness of approximately 30 nm deposited on its first surface and a thickness of approximately 125 μm, hexagonal (closed pattern) spacers forming a honeycomb structure are formed on the ITO layer. These spacers have a spacing of approximately 450 μm, a height of approximately 12 μm (cell gap), and a linewidth of approximately 30 μm. Therefore, the area of ​​the closed pattern (hexagon) formed by the spacers is approximately 2.14 mm². 2 Left and right. The spacers are formed using a UV-curable acrylic resin composition via conventional photolithography. A horizontal alignment film (Nissan, SE-7492K) with a thickness of approximately 300 nm is formed on the spacers, and the horizontal alignment film is rubbed in one direction.

[0146] A liquid crystal composition is coated on the surface of a horizontally aligned film on a second substrate, and a pressure-sensitive adhesive layer of a first substrate is laminated to face the coated surface of the liquid crystal composition.

[0147] Here, as the liquid crystal composition, a composition comprising a liquid crystal compound (JNC, SHN-5011XX), a chiral dopant (HCCH, S811), and a dichroic dye (black dye) is used. The amount of the chiral dopant used in the liquid crystal cell is 3.7% by weight, and the amount of the dichroic dye used in the liquid crystal cell is 3% by weight.

[0148] The resulting liquid crystal cell has a pitch (p) of approximately 2.5 μm and a cell gap (d) (approximately 12 μm) to pitch (p) ratio (d / p) of approximately 4.8.

[0149] Here, the pitch of the liquid crystal cell is measured using the wedge cell measurement method according to the method described in D. Podolskyy et al.'s paper, "Simple method for accurate measurements of the cholesteric pitch using astripe-wedge Grandjean-Cano cell" (Liquid Crystals, Vol. 35, No. 7, July 2008, pp. 789-791).

[0150] The liquid crystal cell is an HTN mode liquid crystal cell with a twist angle of 1720 degrees when no voltage is applied.

[0151] Example 2

[0152] The liquid crystal cell was manufactured in the same manner as in Example 1, except that square-shaped spacers were used as spacers. The square-shaped spacers had a pitch of about 450 μm, a height of about 10 μm, and a linewidth of about 30 μm.

[0153] Furthermore, the pitch (p) of the formed liquid crystal cells is approximately 2.5 μm, and the ratio (d / p) of the cell gap (d) (approximately 10 μm) to the pitch (p) is approximately 4.0.

[0154] The liquid crystal cell in Example 2 is also an HTN mode liquid crystal cell with a twist angle of 1720 degrees when no voltage is applied.

[0155] Example 3

[0156] The liquid crystal cell was fabricated in the same manner as in Example 1, except that the following steps were performed. Square-shaped spacers were formed as spacers on the ITO (indium tin oxide) layer of the second substrate. The square-shaped spacers had a pitch of approximately 350 μm, a height of approximately 6.3 μm, and a linewidth of approximately 30 μm. The liquid crystal cell was fabricated in the same manner as in Example 1, except that an alignment film was not formed on the spacers of the second substrate.

[0157] The pitch (p) of the liquid crystal cell is approximately 1.6 μm, and the ratio (d / p) of the cell gap (d) to the pitch (p) is approximately 4.0 (approximately 3.94). The liquid crystal cell of Example 3 is also an HTN mode liquid crystal cell with a twist angle of 1720 degrees when no voltage is applied.

[0158] Comparative Example 1

[0159] As the alignment film forming material, a polyimide-based material (Nissan, SE-5661) for vertical alignment films, used as a friction alignment film forming material, was employed. The alignment film forming material was prepared by dissolving it in a solvent at a concentration of approximately 3% by weight. A mixed solvent was used, in which PGME (propylene glycol methyl ether) and GBL (γ-butyrolactone) were mixed in a weight ratio of 7:3 (PGME:GBL). The alignment film forming material was prepared by formulating spherical spacers with a diameter of approximately 12 μm in the mixture of the alignment film forming material and the solvent, such that the concentration in the entire alignment film forming material was approximately 1% by weight.

[0160] The coating material is applied to a suitable thickness on a PET (poly(ethylene terephthalate)) film having an ITO (indium tin oxide) electrode layer formed on one side using a bar coater, and then subjected to heat treatment at a temperature of about 130°C for about 10 minutes to form the first substrate.

[0161] As a second substrate, a PC (polycarbonate) film without any spacers is used, wherein an ITO (indium tin oxide) electrode layer and a known polyimide horizontal alignment film (Nissan, SE-7492K) are sequentially formed on one side as described above.

[0162] The liquid crystal cell is manufactured by coating a liquid crystal composition onto the surface of a horizontal alignment film on a second substrate, and laminating a vertical alignment film layer of a first substrate facing the coated surface of the liquid crystal composition. The liquid crystal composition used is a composition comprising a liquid crystal compound (JNC, SHN-5011XX), a chiral dopant (HCCH, S811), and a dichroic dye (black dye). The amount of chiral dopant contained in the liquid crystal cell is approximately 2.3% by weight, and the amount of dichroic dye contained in the liquid crystal cell is approximately 3% by weight.

[0163] The thickness (d) of the liquid crystal cell is approximately 10 μm, the pitch (p) is approximately 4 μm, and the ratio of cell gap (d) to pitch (p) (d / p) is approximately 2.5. The liquid crystal cell is a liquid crystal cell with a twist angle of 1000 degrees when no voltage is applied.

[0164] Comparative Example 2

[0165] The liquid crystal cell was manufactured in the same manner as in Example 1, except that the thickness (d, cell gap) of the liquid crystal cell was adjusted so that the ratio (d / p) of the cell gap (d) to the pitch (p) was about 2.5.

[0166] Comparative Example 3

[0167] The liquid crystal cell was manufactured in the same manner as in Example 1, except that the thickness (d, cell gap) of the liquid crystal cell was adjusted so that the ratio (d / p) of the cell gap (d) to the pitch (p) was about 12.

[0168] Experimental Example 1

[0169] The transmittance variability of the liquid crystal cells prepared in the examples and comparative examples was evaluated.

[0170] Transmittance is measured using a haze meter (NDH5000SP, Sekos) according to ASTM D1003. When light with wavelengths from 380 nm to 780 nm is incident on the object being measured within an integrating sphere, the incident light is split into diffuse light (DT, the sum of diffuse and emitted light) and linear light (PT, light emitted from the frontal direction excluding diffuse light). The diffuse and linear light can be measured separately by focusing them onto a light-receiving element within the integrating sphere. That is, through the above process, the total transmitted light (TT) is defined as the sum of diffuse light (DT) and linear light (PT) (DT+PT), and the total transmitted light refers to the total transmittance.

[0171] Table 1 below shows the total transmittance of the comparative examples and embodiments, where the black mode is the state in which no voltage is applied to the liquid crystal cell (0V), and the transparent mode is the state in which a voltage of 60V is applied to the liquid crystal cell.

[0172] [Table 1]

[0173]

[0174] Based on the results in Table 1, it can be determined that the liquid crystal cell according to this application exhibits low transmittance in black mode but high transmittance in transparent mode relative to black mode. On the other hand, the liquid crystal cells of Comparative Examples 1 and 2 have high transmittance in black mode, therefore, in transparent mode, the ratio of transmittance to black mode is not high.

[0175] Furthermore, Comparative Example 3 exhibited low transmittance in black mode, but did not adequately ensure transmittance in transparent mode.

[0176] at the same time, Figure 3 This is an optical photograph of the liquid crystal cell of Comparative Example 1. Figure 4 and Figure 5 The figures are optical photographs of the liquid crystal cells of Examples 1 and 2, respectively. According to the figures, in Comparative Example 1 where no spacer was applied, optical defects such as oily streak lines appear in the liquid crystal cell of this application, leading to visibility problems.

[0177] [Explanation of reference numerals in the attached figures]

[0178] 101: First basement

[0179] 103: Pressure-sensitive adhesive layer or adhesive layer

[0180] 201: Second basement

[0181] 203: Liquid crystal alignment film

[0182] 300: Liquid Crystal Layer

[0183] 400: Partition wall spacer

[0184] 500: Electrode layer

Claims

1. An optical modulation device, comprising: A first substrate, wherein a pressure-sensitive adhesive layer or an adhesive layer is formed on a first surface of the first substrate; A second substrate having a first surface, wherein the first surface of the second substrate is configured to face the first surface of the first substrate; as well as Liquid crystal layer between the first substrate and the second substrate The liquid crystal layer comprises a liquid crystal compound, a chiral dopant, and a dichroic dye. The distance between the first substrate and the second substrate is maintained by a partition wall spacer. The liquid crystal layer is configured to achieve a twisted orientation. The liquid crystal layer exists in a twisted state when no voltage is applied, and exists in a vertically aligned state when a voltage is applied. In the case of the twisted orientation, the ratio of the thickness of the liquid crystal layer to the pitch of the liquid crystal layer is greater than 2.8 and not greater than 10. The ratio of the spacing of the partition wall spacers to the pitch of the liquid crystal layer is in the range of 50 to 500.

2. The optical modulation apparatus according to claim 1, wherein no alignment film is formed on the first substrate.

3. The optical modulation device according to claim 1 or 2, wherein the partition wall spacers are honeycomb spacers, quadrilateral spacers, or random spacers.

4. The optical modulation apparatus according to claim 1 or 2, wherein the spacing between the spacers is in the range of 100 μm to 1,000 μm.

5. The optical modulation apparatus according to claim 1 or 2, wherein the thickness of the liquid crystal layer is in the range of 0.1 μm to 50 μm.

6. The optical modulation apparatus according to claim 1 or 2, wherein the ratio of the spacing of the partition wall spacers to the thickness of the liquid crystal layer is in the range of 10 to 100.

7. The optical modulation apparatus according to claim 1 or 2, wherein a liquid crystal alignment film is formed on the first surface of the second substrate.

8. The optical modulation apparatus according to claim 7, wherein the liquid crystal alignment film is a horizontal alignment film.

9. The optical modulation apparatus according to claim 1 or 2, wherein no liquid crystal alignment film is formed on the second substrate.

10. The optical modulation device according to claim 1 or 2, wherein the optical modulation device exhibits minimum transmittance when no voltage is applied.

11. A window, comprising: The optical modulation apparatus according to any one of claims 1 to 10.

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