KR102816679B1 - Optical Device - Google Patents

Abstract

The present application relates to an optical device. The optical device of the present application can secure structural stability and good quality uniformity by properly maintaining the cell gap of a liquid crystal element, having excellent adhesion between an upper substrate and a lower substrate, and minimizing defects such as pressing or crowding during the bonding process of an outer substrate.

Description

Optical Device

The present application relates to an optical device.

In order to ensure long-term stability and large-area expandability of liquid crystal film cells using flexible substrates, it is important to maintain the cell gap between the upper and lower substrates and provide adhesion between the upper and lower substrates.

Non-patent document 1 discloses a technology for forming an organic film pattern in the shape of a pillar or wall with a cell gap height on one substrate and fixing it to an opposite substrate using an adhesive. However, this technology requires that the adhesive be located only on the pillar or wall surface, and the technology for micro-stamping the adhesive on the pillar or wall surface has a high process difficulty, it is difficult to control the thickness and area of the adhesive, there is a high possibility that the adhesive will be pushed out when the upper and lower substrates are bonded, and there is a concern that the adhesive will be contaminated into the alignment film or liquid crystal.

“Tight Bonding of Two Plastic Substrates for Flexible LCDs” SID Symposium Digest, 38, pp. 653-656 (2007)

In order to maintain the cell gap of the liquid crystal cell and secure the adhesion between the upper and lower substrates, it may be considered to form a spacer and an alignment film on the lower substrate, and then form an adhesive having both liquid crystal alignment and adhesion on the upper substrate and bond them together. However, this structure is vulnerable to external pressure due to the very low modulus of the adhesive layer, making it difficult to obtain good quality in a high-temperature and high-pressure autoclave process. Specifically, if the structural stability of the liquid crystal cell is not secured in the autoclave process, the cell gap collapses or the liquid crystal flow/moulding is poor, which causes a deterioration in the electro-optical characteristics and appearance uniformity of the liquid crystal cell.

The present application provides an optical device in which the cell gap of a liquid crystal cell is appropriately maintained, excellent adhesion between an upper substrate and a lower substrate is achieved, and defects such as pressing or crowding are minimized, thereby ensuring structural stability and good quality uniformity.

In the present specification, if the measurement temperature affects the result, the property is a property measured at room temperature unless otherwise specified. The term room temperature refers to the natural temperature that is not heated or cooled, and is typically a temperature within the range of about 10°C to 30°C, or about 23°C or about 25°C. In addition, unless otherwise specified in the present specification, the unit of temperature is ℃. In the present specification, if the measurement pressure affects the result, the property is a property measured at atmospheric pressure unless otherwise specified. The term atmospheric pressure refers to the natural temperature that is not pressurized or cooled, and typically refers to about 1 atm as atmospheric pressure.

The present application relates to an optical device. FIG. 1 exemplarily shows an optical device of the present application. As shown in FIG. 1, the optical device may include a first outer substrate (100a), a second outer substrate (100b) opposite to the first outer substrate (100a), and a liquid crystal element (400) positioned between the first and second outer substrates. The optical device may further include a first polarizer (200a) positioned between the first outer substrate and the liquid crystal element, and a second polarizer (200b) positioned between the second outer substrate and the liquid crystal element.

The optical device may include at least one intermediate layer positioned between the first outer substrate and the liquid crystal element, and between the second outer substrate and the liquid crystal element. FIG. 1 exemplarily illustrates an optical device including intermediate layers (300a, 300b, 300c, 300d) positioned between the first outer substrate (100a) and the liquid crystal element (400), and between the second outer substrate (100b) and the liquid crystal element (400).

The first outer substrate and the second outer substrate may each independently be an inorganic substrate or a plastic substrate. The inorganic substrate is not particularly limited, and a known inorganic substrate may be used. For example, a glass substrate having excellent light transmittance may be used as the inorganic substrate. Examples of the glass substrate that may be used include, but are not limited to, a soda lime glass substrate, a general tempered glass substrate, a borosilicate glass substrate, or an alkali-free glass substrate. The polymer substrate may include, but is not limited to, a cellulose film such as TAC (triacetyl cellulose) or DAC (diacetyl cellulose); a COP (cyclo olefin copolymer) film such as a norbornene derivative; An acrylic film such as PAR (Polyacrylate) or PMMA (poly(methyl methacrylate)); a polyolefin film such as PC (polycarbonate) film; PE (polyethylene) or PP (polypropylene); PVA (polyvinyl alcohol) film; PI (polyimide) film; a sulfone film such as PSF (polysulfone) film, PPS (polyphenylsulfone) film or PES (polyethersulfone) film; a polyester film such as PEEK (polyetheretherketon) film; PEI (polyetherimide) film; PEN (polyethylenenaphthatlate) film or PET (polyethyleneterephtalate) film; or a fluorine resin film can be used, but is not limited thereto. The first outer substrate and the second outer substrate may each have a coating layer of gold; silver; or a silicon compound such as silicon dioxide or silicon monoxide, or a functional layer such as an antireflection layer, as needed.

In one example, the first outer substrate and/or the second outer substrate may be a glass substrate. In order to overcome the physical limitations of the liquid crystal element, the automobile or window industry may bond glass substrates to both sides of the liquid crystal element, or bond a glass substrate to one side of the liquid crystal element and a film substrate to the other side. Among these, the automobile industry has demanded bonding glass substrates to both sides of the liquid crystal element using an adhesive layer. However, in the case of the liquid crystal element, due to the use of an adhesive layer, it is vulnerable to external pressure, and thus defects such as collapse of the cell gap or flow or crowding of the liquid crystal may occur in a glass bonding process such as a high-temperature and high-pressure autoclave. According to the present invention, as described below, by controlling the thickness of the intermediate layer, the above defects can be minimized, and the structural stability and quality uniformity of the optical device can be secured.

The thickness of the first outer substrate and the second outer substrate can each be about 0.3 mm or more. In other examples, the thickness can be about 0.5 mm or more, 1 mm or more, 1.5 mm or more, or about 2 mm or more, and can be about 10 mm or less, 9 mm or less, 8 mm or less, 7 mm or less, 6 mm or less, 5 mm or less, 4 mm or less, or about 3 mm or less.

The first outer substrate and the second outer substrate may be flat substrates or substrates having a curved shape. For example, the first outer substrate and the second outer substrate may be flat substrates at the same time, or may have curved formations at the same time, or one of them may be a flat substrate and the other may be a curved substrate. In addition, in the case where they have curved shapes at the same time, the curvature or curvature radius of each may be the same or different. In the present specification, the curvature or curvature radius can be measured by a method known in the industry, and can be measured using, for example, a non-contact device such as a 2D Profile Laser Sensor, a Chromatic confocal line sensor, or a 3D Measuring Confocal Microscopy. A method of measuring the curvature or curvature radius using such devices is known.

In relation to the first outer substrate and the second outer substrate, for example, when the curvature or curvature radius of the front surface and the back surface are different, the curvature or curvature radius of the respective facing surfaces, that is, in the case of the first outer substrate, the curvature or curvature radius of the surface facing the second outer substrate, and in the case of the second outer substrate, the curvature or curvature radius of the surface facing the first outer substrate may be used as a reference. In addition, when the curvature or curvature radius of the surfaces is not constant and there are different portions, the largest curvature or curvature radius may be used as a reference, the smallest curvature or curvature radius may be used as a reference, or the average curvature or average curvature radius may be used as a reference.

The first outer substrate and the second outer substrate may have a difference in curvature or radius of curvature of about 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, respectively. The difference in the curvature or radius of curvature is a numerical value calculated as 100×(CL-CS)/CS, where a large curvature or radius of curvature is referred to as CL and a small curvature or radius of curvature is referred to as CS. In addition, the lower limit of the difference in the curvature or radius of curvature is not particularly limited. Since the difference in the curvature or radius of curvature of the first and second outer substrates may be the same, the difference in the curvature or radius of curvature may be about 0% or more or greater than about 0%. Such control of the curvature or radius of curvature is useful in a structure in which a liquid crystal element is in contact with an intermediate layer, such as the optical device of the present application. In other words, if the curvature or radius of curvature exceeds 10%, when the outer substrate and the liquid crystal element are brought into contact with the intermediate layer described later, a problem may occur in which the bonded outer substrate is deformed due to reduced bonding strength. However, if controlled to within 10%, the problem in which the bonded outer substrate is deformed due to reduced bonding strength can be effectively prevented.

The first outer substrate and the second outer substrate may have curvatures of the same sign. In other words, the first and second outer substrates may both be bent in the same direction. That is, the case is when the center of curvature of the first outer substrate and the center of curvature of the second outer substrate both exist in the same portion among the upper and lower portions of the first and second outer substrates. When the first outer substrate and the second outer substrate are bent in the same direction, the first and second outer substrates can be more efficiently bonded to the intermediate layer, and after bonding, the first and second outer substrates and the liquid crystal element and/or the polarizer can be more efficiently prevented from being bonded.

The first outer substrate and the second outer substrate have no particular limitation on the specific range of their respective curvatures or curvature radii. In one example, the first and second outer substrates each have a radius of curvature of about 100R or more, 200R or more, 300R or more, 400R or more, 500R or more, 600R or more, 700R or more, 800R or more, or about 900R or more, or about 10,000R or less, 9,000R or less, 8,000R or less, 7,000R or less, 6,000R or less, 5,000R or less, 4,000R or less, 3,000R or less, 2,000R or less, 1,900R or less, 1,800R or less, 1,700R or less, 1,600R or less, 1,500R or less, 1,400R or less, 1,300R or less, 1,200R or less, It may be 1,100R or less or about 1,050R or less. In the above, R means the degree of curvature of a circle with a radius of 1 mm. Therefore, for example, 100R in the above is the degree of curvature of a circle with a radius of 100 mm or the radius of curvature for such a circle. The first and second outer substrates may have the same or different radii of curvature within the above range. In one example, when the curvatures of the first and second outer substrates are different from each other, the radius of curvature of the substrate with a greater curvature among them may be within the above range. In one example, when the curvatures of the first and second outer substrates are different from each other, the substrate with a greater curvature among them may be the substrate that is arranged more in the direction of gravity when the optical device is used. If the curvature or radius of curvature of the first and second substrates is controlled as described above, even if the bonding force by the intermediate layer described later is reduced, the net force, which is the sum of the restoring force and gravity, can be applied to prevent spreading.

The term polarizer, as used herein, refers to a film, sheet or device having a polarizing function. A polarizer is a functional device capable of extracting light vibrating in one direction from incident light vibrating in multiple directions.

The first polarizer and the second polarizer may be an absorptive polarizer or a reflective polarizer, respectively. In the present specification, an absorptive polarizer refers to an element that exhibits selective transmission and absorption characteristics with respect to incident light. For example, a polarizer can transmit light vibrating in one direction from incident light vibrating in various directions and absorb light vibrating in the remaining direction. In the present specification, a reflective polarizer refers to an element that exhibits selective transmission and reflection characteristics with respect to incident light. The polarizer can transmit light vibrating in one direction from incident light vibrating in various directions, for example, and reflect light vibrating in the remaining direction. According to one embodiment of the present application, the polarizer may be an absorptive polarizer.

The first polarizer and the second polarizer may each be linear polarizers. In the present specification, a linear polarizer means a case where light that is selectively transmitted is linearly polarized and vibrates in one direction, and light that is selectively absorbed or reflected is linearly polarized and vibrates in a direction perpendicular to the vibration direction of the linearly polarized light. In the case of an absorptive linear polarizer, the light transmission axis and the light absorption axis may be perpendicular to each other. In the case of a reflective linear polarizer, the light transmission axis and the light reflection axis may be perpendicular to each other.

In one example, the first polarizer and the second polarizer may be polymer stretched films dyed with iodine or anisotropic dye, respectively. The polymer stretched film may be, for example, a poly(vinyl alcohol) (PVA) stretched film. In another example, the first polarizer and the second polarizer may be guest-host type polarizers that use a liquid crystal polymerized in an aligned state as a host and an anisotropic dye arranged according to the alignment of the liquid crystal as a guest. In another example, the first polarizer and the second polarizer may be a thermotropic liquid crystal film or a lyotropic liquid crystal film, respectively.

A protective film, an antireflection film, a retardation film, an adhesive layer, an adhesive layer, a surface treatment layer, etc. may be additionally formed on one or both sides of the first polarizer and the second polarizer, respectively. The retardation film may be, for example, a quarter wavelength plate or a half wavelength plate. The quarter wavelength plate may have an in-plane retardation value for light having a wavelength of 550 nm in a range of about 100 nm to 180 nm, 100 nm, or 150 nm. The half wavelength plate may have an in-plane retardation value for light having a wavelength of 550 nm in a range of about 200 nm to 300 nm, or 250 nm to 300 nm. The retardation film may be, for example, a polymer stretched film or a liquid crystal polymer film.

The transmittance of the first polarizer and the second polarizer for light having a wavelength of 550 nm may each be in the range of 40% to 50%. The transmittance may mean the single transmittance of the polarizer for light having a wavelength of 550 nm. The single transmittance of the polarizer may be measured, for example, using a spectrometer (V7100, manufactured by Jasco). For example, the single transmittance may be calculated after measuring the transmittance of each while setting air as the base line and aligning the axis of the polarizer sample vertically and horizontally with the axis of the reference polarizer while placing the polarizer sample (excluding the upper and lower protective films) in the device.

The optical transmission axis of the first polarizer and the optical transmission axis of the second polarizer may be perpendicular to each other. Specifically, the angle formed by the optical transmission axis of the first polarizer and the optical transmission axis of the second polarizer may be within a range of 80 to 100 degrees or 85 to 95 degrees. When the optical transmission axis of the first polarizer and the optical transmission axis of the second polarizer are perpendicular to each other, light leakage, etc. may occur depending on the separation distance between the first polarizer and the second polarizer.

According to the present application, the at least one intermediate layer may include an intermediate layer having a thickness of 380 μm or less, which is positioned between the first polarizer and the liquid crystal element and between the second polarizer and the liquid crystal element, respectively. That is, the thicknesses of the intermediate layer existing between the first polarizer and the liquid crystal element and the intermediate layer existing between the second polarizer and the liquid crystal element may each be 380 μm or less. Through this, the distance between the first polarizer and the second polarizer can be minimized, thereby reducing light leakage and ensuring structural stability of the liquid crystal element. The lower limits of the thicknesses of the intermediate layer existing between the first polarizer and the liquid crystal element and the intermediate layer existing between the second polarizer and the liquid crystal element may each be 10 μm or more.

Fig. 2 illustrates an example of a liquid crystal element. As shown in Fig. 2, the liquid crystal element may include a first substrate layer (10a), an adhesive layer (10c) formed on the inner side of the first substrate layer, a second substrate layer (20a) positioned opposite the first substrate layer (10a), a spacer (20c) formed on the inner side of the second substrate layer (20a), and a liquid crystal layer (30) positioned between the first substrate layer (10a) and the second substrate layer (10b).

For the first substrate layer and the second substrate layer, for example, an inorganic film such as a glass film, a crystalline or amorphous silicon film, a quartz or ITO (Indium Tin Oxide) film, or a polymer film can be used, and in terms of implementing a flexible element, a polymer film can be used.

In one example, the first substrate layer and the second substrate layer may each be a polymer film. As the polymer film, TAC (triacetyl cellulose); COP (cyclo olefin copolymer), such as a norbornene derivative; PMMA (poly (methyl methacrylate); PC (polycarbonate); PE (polyethylene); PP (polypropylene); PVA (polyvinyl alcohol); DAC (diacetyl cellulose); Pac (Polyacrylate); PES (poly ether sulfone); PEEK (polyetheretherketon); PPS (polyphenylsulfone), PEI (polyetherimide); PEN (polyethylenemaphthatlate); PET (polyethyleneterephtalate); PI (polyimide); PSF (polysulfone); PAR (polyarylate) or amorphous fluorine resin, etc. can be used, but are not limited thereto. The first substrate layer and the second substrate layer may include a coating layer of a silicon compound such as gold, silver, silicon dioxide or silicon monoxide, or an anti-reflection layer, if necessary.

The first substrate layer and the second substrate layer may each have a thickness of about 10 ㎛ to about 1,000 ㎛. As another example, the substrate layers may each have a thickness of about 20 ㎛ or more, 40 ㎛ or more, 60 ㎛ or more, 80 ㎛ or more, 100 ㎛ or more, 120 ㎛ or more, 140 ㎛ or more, 160 ㎛ or more, or about 180 ㎛ or more, and may each be about 900 ㎛ or less, 800 ㎛ or less, 700 ㎛ or less, 600 ㎛ or less, 500 ㎛ or less, or about 400 ㎛ or less. When the thicknesses of the first substrate layer and the second substrate layer satisfy the above ranges, when manufacturing an optical device by bonding a liquid crystal element with an outer substrate, appearance defects such as wrinkles can be reduced.

The adhesive layer may be present on the inner surface of the first substrate layer. In the present specification, the “inner surface” of a component included in a liquid crystal element may mean a surface facing the liquid crystal layer.

The adhesive layer can be optically transparent. The adhesive layer can have an average transmittance for visible light in the range of, for example, 380 nm to 780 nm of about 80% or greater, 85% or greater, 90% or greater, or 95% or greater.

The adhesive layer may be a liquid crystal alignment adhesive layer. The adhesive layer may be, for example, a vertical alignment adhesive layer or a horizontal alignment adhesive layer. In the present specification, the term “vertical alignment adhesive” may mean an adhesive that provides vertical alignment force to adjacent liquid crystal compounds and has adhesive strength capable of bonding an upper substrate and a lower substrate at the same time. In the present specification, the term “horizontal alignment adhesive” may mean an adhesive that provides horizontal alignment force to adjacent liquid crystal compounds and has adhesive strength capable of bonding an upper substrate and a lower substrate at the same time. The pretilt angle of the adjacent liquid crystal compound for the vertically aligned adhesive can be in the range of 80 degrees to 90 degrees, 85 degrees to 90 degrees, or about 87 degrees to 90 degrees, and the pretilt angle of the adjacent liquid crystal compound for the horizontally aligned adhesive can be in the range of 0 degrees to 10 degrees, 0 degrees to 5 degrees, or 0 degrees to 3 degrees.

In this specification, the pretilt angle may mean an angle formed by a director of a liquid crystal compound with respect to a plane that is horizontal to a liquid crystal alignment adhesive or alignment film when no voltage is applied. In this specification, the director of the liquid crystal compound may mean an optical axis or a slow axis of a liquid crystal layer. Alternatively, the director of the liquid crystal compound may mean a major axis direction when the liquid crystal compound is in a rod shape, and may mean an axis parallel to a normal direction of a discic plane when the liquid crystal compound is in a discic shape.

The thickness of the adhesive layer may be, for example, in the range of 3 ㎛ to 15 ㎛. When the thickness of the adhesive layer is within the above range, it can be advantageous in minimizing defects such as pressing or crowding of the adhesive when used in the manufacture of a liquid crystal device while securing the adhesion between the upper substrate and the lower substrate.

As the adhesive layer, various types of adhesives known in the industry as OCA (Optically Clear Adhesive) can be suitably used. The adhesive may be different from the OCR (Optically Clear Resin) type adhesive, which is hardened after the objects to be attached are bonded, in that it is hardened before the objects to be attached are bonded. As the adhesive, for example, an acrylic, silicone, epoxy or urethane type adhesive can be applied.

The adhesive layer may include a cured product of an adhesive resin. In one example, the adhesive layer may include a silicone-based adhesive. The silicone-based adhesive may include a cured product of a curable silicone compound as an adhesive resin.

The type of the curable silicone compound is not particularly limited, and for example, a heat-curable silicone compound or an ultraviolet-curable silicone compound can be used. The curable silicone compound can be referred to as an adhesive resin.

In one example, the curable silicone compound can be an addition curable silicone compound.

Specifically, the addition-curable silicone compound may be exemplified by, but is not limited to, (1) organopolysiloxane containing two or more alkenyl groups in the molecule and (2) organopolysiloxane containing two or more silicon-bonded hydrogen atoms in the molecule. Such a silicone compound can form a cured product by an addition reaction, for example, in the presence of a catalyst described below.

More specific examples of the above (1) organopolysiloxane that can be used in the present application include a dimethylsiloxane-methylvinylsiloxane copolymer having trimethylsiloxane groups capped at both molecular ends, a methylvinylpolysiloxane having trimethylsiloxane groups capped at both molecular ends, a dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer having trimethylsiloxane groups capped at both molecular ends, a dimethylpolysiloxane having dimethylvinylsiloxane groups capped at both molecular ends, a methylvinylpolysiloxane having dimethylvinylsiloxane groups capped at both molecular ends, a dimethylsiloxane-methylvinylsiloxane copolymer having dimethylvinylsiloxane groups capped at both molecular ends, a dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer having dimethylsiloxane groups capped at both molecular ends, a siloxane unit represented by R12SiO1/2 and a siloxane unit represented by R12R2SiO1/2. Examples thereof include, but are not limited to, an organopolysiloxane copolymer comprising a siloxane unit represented by SiO4/2, an organopolysiloxane copolymer comprising a siloxane unit represented by R12R2SiO1/2 and a siloxane unit represented by SiO4/2, 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 mixtures of two or more of the above. In the above, R1 is a hydrocarbon group other than an alkenyl group, and 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; an aryl group 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 can be a halogen-substituted alkyl group such as a chloromethyl group, a 3-chloropropyl group, or a 3,3,3-trifluoropropyl group. In addition, R2 in the above can be an alkenyl group, and specifically, a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, or a heptenyl group.

More specific examples of the above (2) organopolysiloxane that can be used in the present application include a methylhydrogenpolysiloxane having trimethylsiloxane groups capped at both molecular ends, a dimethylsiloxane-methylhydrogen copolymer having trimethylsiloxane groups capped at both molecular ends, a dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymer having trimethylsiloxane groups capped at both molecular ends, a dimethylpolysiloxane having dimethylhydrogensiloxane groups capped at both molecular ends, a dimethylsiloxane-methylphenylsiloxane copolymer having dimethylhydrogensiloxane groups capped at both molecular ends, a methylphenylpolysiloxane having dimethylhydrogensiloxane groups capped at both molecular ends, an organopolysiloxane copolymer comprising a siloxane unit represented by R13SiO1/2, a siloxane unit represented by R12HSiO1/2, and a siloxane unit represented by SiO4/2, and a siloxane unit represented by R12HSiO1/2. Examples thereof include, but are not limited to, organopolysiloxane copolymers comprising a siloxane unit and a siloxane unit represented by SiO4/2, organopolysiloxane copolymers comprising a siloxane unit represented by R1HSiO2/2 and a siloxane unit represented by R1SiO3/2 or a siloxane unit represented by HSiO3/2, and mixtures of two or more of the above. In the above, R1 is a hydrocarbon group other than an alkenyl group, and specifically, may be 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; an aryl group 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; a halogen-substituted alkyl group such as a chloromethyl group, a 3-chloropropyl group, or a 3,3,3-trifluoropropyl group, etc.

When the adhesive layer is a vertically aligned adhesive layer, the surface energy may be 16 mN/m or less. The lower limit of the surface energy may be, for example, 5 mN/m or more. When the adhesive layer is a horizontally aligned adhesive layer, the surface energy may exceed 16 mN/m. The upper limit of the surface energy may be, for example, 50 mN/m or less. The surface energy can be measured using a drop shape analyzer (DSA100 product of KRUSS). Specifically, the process of dropping deionized water, which has a known surface tension, on the surface of the adhesive and obtaining the contact angle is repeated five times, and the average of the five contact angle values obtained is obtained. In the same way, diiodomethane, which has a known surface tension, is dropped and the contact angle is obtained, and the process of repeating the process is five times, and the average of the five contact angle values obtained is obtained. Thereafter, the surface energy was obtained by substituting the surface tension value (Strom value) of the solvent using the Owens-Wendt-Rabel-Kaelble method using the average contact angle for the obtained deionized water and diiodomethane. The surface energy (γsurface) of the sample can be calculated by considering the dispersion force between nonpolar molecules and the interaction force between polar molecules (γsurface = γdispersion + γpolar), and the ratio of the polar term (γpolar) in the surface energy γsurface can be defined as the polarity of the surface.

The upper substrate and the lower substrate of the liquid crystal element may be attached by an adhesive layer. Specifically, the adhesive layer of the upper substrate and the spacer of the lower substrate may be attached. When an alignment film is formed on the spacer of the lower substrate, an area of the alignment film corresponding to the spacer may be attached to the adhesive layer of the upper substrate.

The adhesive layer may have a storage modulus of 1 MPa or less. The lower limit of the storage modulus of the adhesive layer may be, for example, 0.01 MPa or more. The storage modulus (G2) of the adhesive layer may be specifically, 0.02 MPa or more, 0.04 MPa, 0.06 MPa, 0.08 MPa, or 0.1 MPa or more, and 0.8 MPa or less, 0.6 MPa or less, 0.4 MPa or less, or 0.2 MPa or less. The storage modulus may be a value measured at a temperature of 25°C and a frequency of 6 rad/sec. In order to overcome the limitations of the physical properties of the liquid crystal element, an outer substrate may be bonded to both sides of the liquid crystal element via an intermediate layer. However, due to the low modulus of the adhesive layer, it is vulnerable to external pressure, and defects such as collapse of the cell gap or flow or crowding of the liquid crystal may occur during the bonding process. According to the present invention, the above defects can be minimized and the structural stability and quality uniformity of the optical device can be secured by controlling the thickness of the intermediate layer included in the optical device as described below.

The liquid crystal layer may include a liquid crystal compound. As the liquid crystal compound, a liquid crystal compound whose alignment direction can be changed by application of an external action can be used. In this specification, the term “external action” may mean any external factor that can affect the behavior of a substance included in the liquid crystal layer, such as an external voltage. Accordingly, a state without an external action may mean a state without application of an external voltage, etc.

The type and properties of the liquid crystal compound may be appropriately selected in consideration of the purpose of the present application. In one example, the liquid crystal compound may be a nematic liquid crystal or a smectic liquid crystal. A nematic liquid crystal may refer to a liquid crystal in which rod-shaped liquid crystal molecules are arranged parallel to the long-axis direction without any regularity in position, and a smectic liquid crystal may refer to a liquid crystal in which rod-shaped liquid crystal molecules are arranged regularly to form a layered structure and are arranged parallel to the long-axis direction with regularity. According to one embodiment of the present application, the liquid crystal compound may be a nematic liquid crystal compound.

The nematic liquid crystal compound may be selected to have a clearing point of, for example, about 40°C or higher, 50°C or higher, 60°C or higher, 70°C or higher, 80°C or higher, 90°C or higher, 100°C or higher, or about 110°C or higher, or a phase transition point in the above range, that is, a phase transition point from the nematic phase to the isotropic phase. In one example, the clearing point or phase transition point may be about 160°C or lower, 150°C or lower, or about 140°C or lower.

The liquid crystal compound may be a non-reactive liquid crystal compound. The non-reactive liquid crystal compound may mean a liquid crystal compound that does not have a polymerizable group. Examples of the polymerizable group include, but are not limited to, 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, and the like, and a known functional group known as a polymerizable group may be included.

The liquid crystal compound may have positive or negative dielectric anisotropy. The absolute value of the dielectric anisotropy of the liquid crystal compound may be appropriately selected in consideration of the purpose of the present application. The term "dielectric anisotropy (△ε)" may mean the difference (ε//- ε⊥) between the horizontal dielectric constant (ε//) and the vertical dielectric constant (ε⊥) of the liquid crystal. As used herein, the term horizontal dielectric constant (ε//) means a dielectric constant value measured along the direction of the electric field when a voltage is applied such that the direction of the electric field due to the director of the liquid crystal compound and the applied voltage are substantially horizontal, and the term vertical dielectric constant (ε⊥) means a dielectric constant value measured along the direction of the electric field when a voltage is applied such that the direction of the electric field due to the director of the liquid crystal compound and the applied voltage are substantially perpendicular. The dielectric anisotropy of the liquid crystal molecule may be within a range of 5 to 25.

The refractive index anisotropy of the liquid crystal compound may be appropriately selected in consideration of the purpose of the present application. The term "refractive index anisotropy" in the present specification may mean the difference between the extraordinary refractive index and the ordinary refractive index of the liquid crystal compound. The refractive index anisotropy of the liquid crystal compound 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.

The liquid crystal layer may further include a dichroic dye. When the liquid crystal layer includes a dichroic dye, the liquid crystal element is less affected by changes in the cell gap during the bonding process of the outer substrate even if it includes an adhesive layer, so there is an advantage in that the thickness of the intermediate layer can be made relatively thin to ensure structural stability and quality uniformity of the liquid crystal element.

A dichroic dye can control the light transmittance variable characteristic of a liquid crystal layer. In the present specification, the term "dye" can mean a material capable of intensively absorbing and/or modifying light within at least a part or the entire range within a visible light range, for example, a wavelength range from 400 nm to 700 nm, and the term "dichroic dye" can mean a material capable of anisotropic absorption of light within at least a part or the entire range of a visible light range.

The liquid crystal layer including the liquid crystal compound and the dichroic dye may be a GHLC layer (Guest host liquid crystal layer). In the present specification, the 'GHLC layer (Guest host liquid crystal layer)' may mean a functional layer in which the dichroic dye is arranged together with the arrangement of the liquid crystal compound, and exhibits anisotropic light absorption characteristics with respect to the alignment direction of the dichroic dye and the direction perpendicular to the alignment direction, respectively. For example, the dichroic dye is a material in which the light absorption rate varies depending on the polarization direction. If the light absorption rate of the light polarized in the major axis direction is high, it may be called a p-type dye, and if the light absorption rate of the light polarized in the minor axis direction is high, it may be called an n-type dye. In one example, when a p-type dye is used, polarized light that vibrates in the major axis direction of the dye is absorbed, and polarized light that vibrates in the minor axis direction of the dye is less absorbed and can be transmitted. Unless otherwise specified, it is assumed that the dichroic dye is a p-type dye.

As a dichroic dye, a known dye known to have a property of being able to be aligned according to the alignment state of a liquid crystal compound, for example, by the so-called guest-host effect, can 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, quterylene dyes, benzothiadiazole dyes, diketopyrrolopyrrole dyes, squaraine dyes, or pyromethene dyes, but the dyes applicable in the present application are not limited thereto.

The dichroic dye may be a dye having a dichroic ratio, that is, a value of the absorption of light polarized parallel to the major axis of the dichroic dye divided by the absorption of light polarized parallel to the direction perpendicular to the major axis, of 5 or more, 6 or more, or 7 or more. The dye may satisfy the dichroic ratio at at least some wavelengths or any one wavelength within a wavelength range of a visible light region, for example, within a wavelength range of about 380 nm to 700 nm or within a wavelength range of 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 0.2 wt% or more. The content of the dichroic dye may be specifically 0.5 wt% or more, 1 wt% or more, 2 wt% or more, or 3 wt% or more. The upper limit of the content of the dichroic dye may be, for example, 10 wt% or less, 9 wt% or less, 8 wt% or less, 6 wt% or less, or 5 wt% or less. If the content of the dichroic dye in the liquid crystal layer is too small, it may be difficult to express the desired transmittance variable characteristic, and it may be insufficient to reduce the thickness of the intermediate layer for reducing the variation of the cell gap that may occur during the bonding process of the outer substrate. On the other hand, if the content of the dichroic dye in the liquid crystal layer is too large, there is a concern of precipitation. Therefore, it may be advantageous for the content of the dichroic dye to be within the above range.

The thickness of the liquid crystal layer is not particularly limited, and for example, the thickness of the liquid crystal layer may be about 0.01 μm or more, 0.05 μm or more, 0.1 μm or more, 0.5 μm or more, 1 μm or more, 1.5 μm or more, 2 μm or more, 2.5 μm or more, 3 μm or more, 3.5 μm or more, 4 μm or more, 4.5 μm or more, 5 μm or more, 5.5 μm or more, 6 μm or more, 6.5 μm or more, 7 μm or more, 7.5 μm or more, 8 μm or more, 8.5 μm or more, 9 μm or more, or 9.5 μm or more. The upper limit of the thickness of the liquid crystal layer is not particularly limited, and generally may be about 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less.

The liquid crystal layer can switch between a first alignment state and a second alignment state different from the first alignment state. The switching can be controlled, for example, by application of external energy such as voltage. For example, the liquid crystal layer can be maintained in one of the first and second alignment states in a voltage-free state, and then switched to the other alignment state by application of voltage.

In one example, the first alignment state may be a twist alignment state, i.e., the liquid crystal layer can be switched between the twist alignment and another alignment state by applying external energy.

In one example, the liquid crystal layer can switch between a twisted alignment state and a vertical alignment state. In one example, the liquid crystal layer can be in a vertical alignment state when no voltage is applied, and can be in a twisted alignment state when voltage is applied.

In this specification, the 'vertical alignment state' is a state in which the director of the liquid crystal compound in the liquid crystal layer is arranged approximately perpendicularly to the plane of the liquid crystal layer, and for example, the angle formed by the director of the liquid crystal compound with respect to the plane of the liquid crystal layer may be, for example, within a range of about 80 to 100 degrees or 85 to 95 degrees, or approximately about 90 degrees.

In this specification, the 'twist alignment state' may mean a spiral structure in which the directors of liquid crystal compounds within a liquid crystal layer are twisted along an imaginary spiral axis and aligned to form layers. The twist alignment state may be implemented in a vertical, horizontal, or inclined alignment state. That is, the vertical twist alignment mode is a state in which individual liquid crystal compounds are twisted along the spiral axis in a vertically aligned state to form layers, the horizontal twist alignment mode is a state in which individual liquid crystal compounds are twisted along the spiral axis in a horizontally aligned state to form layers, and the inclined twist alignment mode is a state in which individual liquid crystal compounds are twisted along the spiral axis in an inclined aligned state to form layers. According to the present application, the twist alignment state may be a twist alignment state of a horizontal alignment state.

In the twisted alignment state, the ratio (d/p) of the thickness (d) to the pitch (p) of the liquid crystal layer can be 20 or less, and the lower limit can be 0.5 or more. When the ratio (d/p) of the thickness (d) to the pitch (p) in the twisted alignment state is within the above range, the optical device can exhibit excellent optical transmittance variable characteristics even in a state where it does not include a polarizer. Typically, when the ratio d/p is 0.7 or more and less than 2.5, it can be called an STN (Super Twisted Nematic) mode, and when the ratio d/p is 2.5 or more, it can be called an HTN (Highly Twisted Nematic) driving mode.

The pitch (p) of the liquid crystal layer can be measured by a measurement method using a wedge cell, and specifically, it can be measured by the method described in Simple method for accurate measurements of the cholesteric pitch using a "stripe-wedge Grandjean-Cano cell" by D. Podolskyy et al. (Liquid Crystals, Vol. 35, No. 7, July 2008, 789-791). The above ratio (d/p) can be achieved by introducing an appropriate amount of chiral dopant into the liquid crystal layer.

The liquid crystal layer may further include a chiral dopant. When the liquid crystal layer includes a chiral agent, a twisted alignment state can be implemented. As a chiral agent that can be included in the liquid crystal layer, if it can induce a desired rotation (twisting) without damaging liquid crystal properties, for example, nematic regularity, it can be used without particular limitation. The chiral agent for inducing rotation in the liquid crystal compound needs to include at least chirality in its molecular structure. As the chiral agent, for example, a compound having one or more asymmetric carbons, a compound having an asymmetric point on a heteroatom such as a chiral amine or chiral sulfoxide, or a compound having an axially asymmetric, optically active site having an axial agent such as cumulene or binaphthol can be exemplified. The chiral agent can 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, the chiral dopant liquid crystal S-811 commercially available from Merck or LC756 from BASF, can be used.

The application ratio of the chiral dopant is selected so as to achieve the desired ratio (d/p). Generally, the content (weight %) of the chiral dopant can be calculated by the formula of 100/HTP (Helixcal Twisting power) × pitch (p) (nm). The HTP represents the strength of the twisting of the chiral dopant, and the content of the chiral dopant can be determined by considering the desired pitch with reference to the above method.

The liquid crystal element may additionally include a first electrode layer (10b) formed on the inner surface of the first substrate layer (10a). At this time, the adhesive layer (10c) may be present on the inner surface of the first electrode layer (10b). That is, the first electrode layer (10b) may be present between the first substrate layer (10a) and the adhesive layer (10c). The liquid crystal element may additionally include a second electrode layer (20b) formed on the inner surface of the second substrate layer (20a). At this time, the spacer (20d) may be present on the inner surface of the second electrode layer (20b). That is, the second electrode layer (20b) may be present between the second substrate layer (20a) and the spacer (20d).

The first electrode layer and the second electrode layer may perform a function of applying an external action, for example, an electric field, to cause a material included in the liquid crystal layer to transmit or block incident light. In one example, the first electrode layer and/or the second electrode layer may include, but is not limited to, a conductive polymer, a conductive metal, a conductive nanowire, or a metal oxide such as ITO (Indium Tin Oxide). The upper and/or lower second electrode layers may be formed by depositing, for example, the conductive polymer, the conductive metal, the conductive nanowire, or the metal oxide such as ITO (Indium Tin Oxide).

The liquid crystal element may further include an alignment film (20d) present on the inner surface of the second electrode layer (20b). A spacer (20c) may be present between the second electrode layer (20b) and the alignment film (20d). The alignment film may be formed on the spacer. That is, the upper surface and/or the side surface of the spacer may be in contact with the alignment film. The lower surface of the spacer may be in contact with the second electrode layer. Since the adhesive layer may have liquid crystal alignment properties, the inner surface of the first electrode layer may not include an alignment film.

In this specification, the combination of the first substrate layer, the first electrode layer, and the adhesive layer may be referred to as the upper substrate, and the combination of the second substrate layer, the second electrode layer, the spacer, and the alignment film may be referred to as the lower substrate. In the liquid crystal device, the upper substrate may not include a separate alignment film other than the adhesive layer, and the lower substrate may include the alignment film.

The alignment film and the liquid crystal layer may be in contact. The alignment film may be a vertical alignment film or a horizontal alignment film. In the present specification, the term “horizontal alignment film” may mean a layer including an alignment material that provides horizontal alignment force to a liquid crystal compound present in an adjacent liquid crystal layer. In the present specification, the term “vertical alignment film” may mean a layer including an alignment material that provides vertical alignment force to a liquid crystal compound present in an adjacent liquid crystal layer. The pretilt angle of the adjacent liquid crystal compound with respect to the vertical alignment film may be in the range of 80 degrees to 90 degrees, 85 degrees to 90 degrees, or about 87 degrees to 90 degrees, and the pretilt angle of the adjacent liquid crystal compound with respect to the horizontal alignment film may be in the range of 0 degrees to 10 degrees, 0 degrees to 5 degrees, or 0 degrees to 3 degrees. Unlike an adhesive layer, the alignment film may not have an adhesive force that adheres the upper substrate and the lower substrate. In one example, the alignment film may have a peeling force close to 0 with respect to the upper substrate in the state of the liquid crystal element of Fig. 2.

The alignment film may be a rubbing alignment film or a photo-alignment film. The alignment direction of the alignment film may be the rubbing direction in the case of a rubbing alignment film, or the direction of the polarized light being irradiated in the case of a photo-alignment film. This alignment direction can be confirmed by a detection method using an absorption-type linear polarizer. Specifically, the alignment direction can be confirmed by arranging an absorption-type linear polarizer on one side of the liquid crystal layer in a state where the liquid crystal compound included in the liquid crystal layer is horizontally aligned, and measuring the transmittance while rotating the polarizer 360 degrees. In this state, when irradiating light toward the liquid crystal layer or the absorption-type linear polarizer side and measuring the luminance (transmittance) from the other side, the transmittance tends to be low when the absorption axis or the transmission axis and the alignment direction of the liquid crystal alignment film coincide, and the alignment direction can be confirmed through a simulation that reflects the refractive index anisotropy of the applied liquid crystal compound, etc. A method for confirming the alignment direction according to the mode of the liquid crystal layer is known, and in the present application, the alignment direction of the alignment film can be confirmed by this known method.

As the alignment film, a material known to exhibit alignment ability by rubbing alignment, such as a polyimide compound, a polyvinyl alcohol compound, a polyamic acid compound, a polystyrene compound, a polyamide compound, and a polyoxyethylene compound, or a polyimide compound, a polyamic acid compound, a polynorbornene compound, a phenylmaleimide copolymer compound, a polyvinylcinnamate compound, a polyazobenzene compound, a polyethyleneimide compound, a polyvinylalcohol compound, a polyamide compound, a polyethylene compound, a polystylene compound, a polyphenylenephthalamide compound, It may include at least one selected from the group consisting of materials known to be capable of exhibiting orientation ability upon light irradiation, such as a polyester compound, a chloromethylated polyimide (CMPI) compound, a polyvinylcinnamate (PVI) compound, and a polymethyl methacrylate compound, but is not limited thereto.

The spacer (20c) can maintain a gap between the upper substrate and the lower substrate. A liquid crystal layer can exist in an area where the spacer does not exist between the upper substrate and the lower substrate.

The spacer may be a patterned spacer. The spacer may have a column shape or a partition wall shape. The partition wall may divide the space between the lower substrate and the upper substrate into two or more spaces. In an area where the spacer does not exist, another film or another layer existing underneath may be exposed. For example, a second electrode layer may be exposed in an area where the spacer does not exist. The alignment film may cover the spacer and the second electrode layer exposed in the area where the spacer does not exist. In a liquid crystal device in which the upper substrate and the lower substrate are bonded, the alignment film existing on the spacer of the lower substrate and the adhesive layer of the upper substrate may be in contact with each other.

In the region where there is no spacer between the upper substrate and the lower substrate, a liquid crystal compound and the aforementioned additives, such as a dichroic dye, a chiral agent, etc., may be present. The shape of the spacer is not particularly limited, and may be applied without limitation to have, for example, a circular, elliptical, or other polygonal shape.

The spacer may include a curable resin. The type of the curable resin is not particularly limited, and for example, a thermosetting resin or a photocurable resin, for example, an ultraviolet-curable resin, can be used. Examples of the thermosetting resin that can be used include, but are not limited to, a silicone resin, a silicon resin, a franc resin, a polyurethane resin, an epoxy resin, an amino resin, a phenol resin, a urea resin, a polyester resin, or a melamine resin. Examples of the ultraviolet-curable resin that can be used include, but are not limited to, 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 polymer.

The spacer can be formed by a patterning process. For example, the spacer can be formed by a photolithography process. The photolithography process can include a process of applying a curable resin composition on a substrate layer or an electrode layer and then irradiating ultraviolet rays through a pattern mask. The pattern mask can be patterned into an ultraviolet-transmitting region and an ultraviolet-blocking region. The photolithography process can further include a process of washing the curable resin composition irradiated with ultraviolet rays. The region irradiated with ultraviolet rays is cured, and the region not irradiated with ultraviolet rays remains in a liquid state, so that it can be patterned into a partition shape by removing it through the washing process. In the photolithography process, in order to easily separate the resin composition and the pattern mask after the ultraviolet irradiation, a release treatment may be performed on the pattern mask, or a release paper may be positioned between the layer of the resin composition and the pattern mask.

The width (line width), interval (pitch), thickness, and area of the spacer can be appropriately selected within a range that does not impair the purpose of the present application. For example, the width (line width) of the spacer can be in a range of 10 ㎛ to 500 ㎛ or in a range of 10 ㎛ to 50 ㎛. The interval (pitch) of the spacer can be in a range of 100 ㎛ to 1000 ㎛. The area of the spacer can be about 5% or more and 50% or less with respect to 100% of the total area of the second substrate layer. When the area of the spacer is within the above range, it can be advantageous in securing excellent electro-optical characteristics while appropriately securing the adhesion between the upper substrate and the lower substrate. The thickness of the spacer can be, for example, in a range of 1 ㎛ to 30 ㎛ or 3 ㎛ to 20 ㎛.

The optical device may include at least one intermediate layer positioned between the first outer substrate and the liquid crystal element, and may include at least one intermediate layer positioned between the second outer substrate and the liquid crystal element. Accordingly, the optical device may include at least two intermediate layers. One surface of the first outer substrate and the second outer substrate may be in contact with the adjacent intermediate layers, respectively. Both surfaces of the liquid crystal element may be in contact with the adjacent intermediate layers, respectively.

The number of intermediate layers of the optical device may be determined depending on whether the optical device further includes elements other than the first outer substrate, the second outer substrate, and the liquid crystal element. The other elements may be, for example, polarizers.

The optical device according to the present application may further include a first polarizer between the first outer substrate and the liquid crystal element, and may further include a second polarizer between the second outer substrate and the liquid crystal element. In this case, the optical device may have a structure in which the first outer substrate, an intermediate layer, a first polarizer, an intermediate layer, a liquid crystal element, an intermediate layer, a second polarizer, an intermediate layer, and the second outer substrate are laminated in this order.

In order to overcome the limitations of the physical properties of a liquid crystal device, an outer substrate can be bonded to both sides of the liquid crystal device via an intermediate layer. However, due to the low modulus of the adhesive layer, it is vulnerable to external pressure, and defects such as collapse of the cell gap or flow or crowding of the liquid crystal may occur during the bonding process. By controlling the thickness of the intermediate layers included in the optical device, the defects can be minimized, and the structural stability and uniform appearance characteristics of the optical device can be secured.

As an example, the sum of the total thicknesses of the at least one intermediate layer may be 1,520 μm or more. The sum of the total thicknesses of the at least one intermediate layer means the sum of the thicknesses of all intermediate layers existing between the first outer substrate and the liquid crystal element film and between the second outer substrate and the liquid crystal element film. When the total thickness of the intermediate layer is within the above range, the structural stability and uniform appearance characteristics of the optical device can be secured by minimizing defects in the bonding process of the outer substrate. The sum of the total thicknesses of the at least one intermediate layer can be specifically 1,600 μm or more, about 1,650 μm or more, 1,700 μm or more, 1,750 μm or more, 1,800 μm or more, 1,850 μm or more, 1,900 μm or more, 1,950 μm or more, 2,000 μm or more, 2,100 μm or more, 2,150 μm or more, or about 2,200 μm or more. The sum of the total thicknesses of the at least one intermediate layer may be, for example, about 6,000 μm or less, 5,900 μm or less, 5,800 μm or less, 5,700 μm or less, 5,600 μm or less, 5,500 μm or less, 5,400 μm or less, 5,300 μm or less, 5,200 μm or less, 5,100 μm or less, or about 5,000 μm or less. It may be advantageous for the total thickness of the intermediate layers to be within the above range because if the total thickness of the intermediate layers is too thick, the electro-optical characteristics such as the transmittance characteristics of the optical device may be deteriorated.

The above at least one intermediate layer may have a single-layer structure of one intermediate layer or may be a laminate of two or more sub-intermediate layers. The thickness and number of the sub-intermediate layers may be controlled in consideration of the thickness of the desired intermediate layer. In one example, the thickness of the sub-intermediate layer may be in the range of 100 ㎛ to 500 ㎛ or in the range of 300 ㎛ to 400 ㎛.

In one example, the thickness of the intermediate layer positioned between the first outer substrate and the first polarizer and the thickness of the intermediate layer positioned between the second outer substrate and the second polarizer can each be in a range of 400 μm to 3,000 μm. As another example, in one example, the thickness of the intermediate layer positioned between the first outer substrate and the first polarizer and the intermediate layer positioned between the second outer substrate and the second polarizer may be about 400 μm or more, 500 μm or more, 600 μm or more, 700 μm or more, 800 μm or more, 900 μm or more, 1000 μm or more, or 1100 μm or more, and may be about 3,000 μm or less, 2,800 μm or less, 2,600 μm or less, 2,400 μm or less, about 2,200 μm or less, about 2,000 μm or less, about 1,800 μm or less, about 1,600 μm or less, or about 1,400 μm or less. In one example, when the thicknesses of the intermediate layer positioned between the first outer substrate and the first polarizer and the intermediate layer positioned between the second outer substrate and the second polarizer are each within the above ranges, it can be advantageous in securing structural stability and uniform appearance characteristics without defects in the bonding process of the outer substrates, without impairing the electro-optical characteristics of the optical device.

As an example, the total thickness (Ta) of at least one intermediate layer positioned between the first outer substrate and the liquid crystal element film and the total thickness (Tb) of at least one intermediate layer positioned between the second outer substrate and the liquid crystal element film may be about 400 μm or more, 500 μm or more, 600 μm or more, 700 μm or more, 800 μm or more, 900 μm or more, 1000 μm or more, or 1100 μm or more, and may be about 3,000 μm or less, 2,900 μm or less, 2,800 μm or less, 2,700 μm or less, about 2,600 μm or less, about 2,500 μm or less, about 2,400 μm or less, or about 2,300 μm or less, respectively. When the thicknesses Ta and Tb are each within the above ranges, it can be advantageous in securing structural stability and uniform appearance characteristics without defects in the bonding process of the outer substrate, without impairing the electro-optical characteristics of the optical device. The sum of the total thicknesses (Ta) of at least one intermediate layer positioned between the first outer substrate and the liquid crystal element film means the sum of the thicknesses of all intermediate layers positioned between the first outer substrate and the liquid crystal element film. In addition, the sum of the total thicknesses (Tb) of at least one intermediate layer positioned between the second outer substrate and the liquid crystal element film means the sum of the thicknesses of all intermediate layers positioned between the second outer substrate and the liquid crystal element film.

As an example, a thickness ratio (Ta/Tb) of a total thickness (Ta) of at least one intermediate layer (30) positioned between the first outer substrate (20a) and the liquid crystal element film (10) to a total thickness (Tb) of at least one intermediate layer (30) positioned between the second outer substrate (20b) and the liquid crystal element film (10) may be in a range of 0.1 to 10. As another example, the thickness ratio (Ta/Tb) may be about 0.12 or more, about 0.13 or more, or about 0.14 or more, and may be about 9.5 or less, 9.0 or less, 8.5 or less, 8.0 or less, 7.5 or less, or about 7.0 or less. When the thickness ratio is in a range of 0.1 to 10, the appearance defect of the liquid crystal element film can be improved more effectively.

As an example, the storage modulus of at least one of the intermediate layers can each be in a range of 1 MPa to 100 MPa. As another example, the storage modulus of the intermediate layer can be at least 2 MPa or at least 4 MPa, and at most 100 MPa, at most 80 MPa, at most 60 MPa, at most 40 MPa, or at most 20 MPa. The storage modulus can be a value measured at a temperature of 25°C and a frequency of 6 rad/sec.

As an example, the at least one intermediate layer can each have a Young's modulus (E) in the range of 0.1 MPa to 100 MPa. As another example, the Young's modulus (E) of the intermediate layer can be at least 0.2 MPa, at least 0.4 MPa, at least 0.6 MPa, at least 0.8 MPa, at least 1 MPa, at least 5 MPa, or at least about 10 MPa, and at most about 95 MPa, at most 80 MPa, at most 75 MPa, at most 70 MPa, at most 65 MPa, at most 60 MPa, at most 55 MPa, or at most about 50 MPa. The above Young's modulus (E) can be measured, for example, in the manner specified in ASTM D882, by cutting the film into the form provided in the relevant standard, and using equipment capable of measuring the Stress-Strain curve (capable of measuring force and length simultaneously), for example, a UTM (Universal testing machine). When the Young's modulus of the intermediate layers included in the optical device is within the above range, it can be more advantageous in securing excellent durability of the optical device. When the intermediate layer is a laminate of at least two or more sub-intermediate layers, each of the sub-intermediate layers can satisfy the above range of Young's modulus.

As an example, each of the at least one intermediate layer may have a coefficient of thermal expansion of 2,000 ppm/K or less. The above thermal expansion coefficient may be, in other examples, about 1,900 ppm/K or less, 1,700 ppm/K or less, 1,600 ppm/K or less, or about 1.500 ppm/K or less, or about 10 ppm/K or more, 20 ppm/K or more, 30 ppm/K or more, 40 ppm/K or more, 50 ppm/K or more, 60 ppm/K or more, 70 ppm/K or more, 80 ppm/K or more, 90 ppm/K or more, 100 ppm/K or more, 200 ppm/K or more, 300 ppm/K or more, 400 ppm/K or more, 500 ppm/K or more, 600 ppm/K or more, 700 ppm/K or more, or about 800 ppm/K or more. The coefficient of thermal expansion of the intermediate layer can be measured, for example, according to the provisions of ASTM D696, cut into a form provided in the relevant standard, and the coefficient of thermal expansion can be calculated by measuring the change in length per unit temperature, or can be measured by a known method such as TMA (ThermoMechanic Analysis). When the coefficients of thermal expansion of the intermediate layers included in the optical device are within the above range, it can be more advantageous in securing excellent durability of the optical device. When the intermediate layer is a laminate of at least two or more sub-intermediate layers, each of the sub-intermediate layers can satisfy the range of the above-mentioned coefficient of thermal expansion.

The at least one intermediate layer may be a thermoplastic polyurethane (TPU) adhesive layer, a polyamide adhesive layer, a polyester adhesive layer, an Ethylene Vinyl Acetate (EVA) adhesive layer, an acrylic adhesive layer, a silicone adhesive layer, or a polyolefin adhesive layer, respectively. According to one embodiment of the present application, the at least one intermediate layer may be thermoplastic polyurethane, respectively.

The optical device may further include an outer layer surrounding a side surface of the liquid crystal element. In the optical device, an upper area of the liquid crystal element may be smaller than an upper area of the first outer substrate or the second outer substrate. In addition, the upper area of the liquid crystal element may be smaller than an upper area of at least one intermediate layer included in the optical device. In one example, the liquid crystal element may be encapsulated by an intermediate layer positioned between the first outer substrate and the liquid crystal element, an intermediate layer positioned between the second outer substrate and the liquid crystal element, and the outer layer. In the present application, the term encapsulation may mean covering the entire surface of the liquid crystal element with the intermediate layer and the outer layer. Depending on the desired structure, for example, the encapsulation structure may be implemented by pressing a laminate including a first outer substrate, an intermediate layer, a first polarizer, an intermediate layer, a liquid crystal element, an intermediate layer, a second polarizer, an intermediate layer, and a second outer substrate in sequence, and an outer layer surrounding a side surface of the liquid crystal element in a vacuum state. This encapsulation structure greatly improves the durability and weather resistance of optical devices, and as a result, they can be reliably applied to outdoor applications such as sunroofs.

The outer layer may include, for example, a thermoplastic polyurethane (TPU) adhesive, a polyamide adhesive, a polyester adhesive, an ethylene vinyl acetate (EVA) adhesive, an acrylic adhesive, a silicone adhesive, or a polyolefin adhesive. In one example, the outer layer may be formed of the same material as the middle layer.

The present application also relates to a method for manufacturing an optical device. The method for manufacturing the optical device may include a step of preparing a laminate sequentially including a first outer substrate, at least one intermediate layer, a first polarizer, at least one intermediate layer, a liquid crystal element, at least one intermediate layer, a second polarizer, at least one intermediate layer, and a second outer substrate, and a step of subjecting the laminate to an autoclave treatment. Unless otherwise specifically stated in the method for manufacturing the optical device, the contents described in the optical device may be equally applied.

The above laminate may further include an outer layer surrounding a side surface of the liquid crystal element.

When the optical device further includes elements other than the liquid crystal element and the polarizer, the laminate may further include elements other than the liquid crystal element and the polarizer at a desired location.

The above autoclave process can be performed by heating and/or pressurizing the laminate formed after the laminating step.

The conditions of the above autoclave process are not particularly limited, and can be performed under an appropriate temperature and pressure, for example, depending on the type of the applied intermediate layer. The temperature of a typical autoclave process is about 80°C or higher, 90°C or higher, or 100°C or higher, and the pressure is 2 atm or higher, but is not limited thereto. The upper limit of the process temperature may be about 200°C or lower, 190°C or lower, 180°C or lower, or 170°C or lower, and the upper limit of the process pressure may be about 10 atm or lower, 9 atm or lower, 8 atm or lower, 7 atm or lower, or 6 atm or lower.

The optical device as described above can be used for various purposes, and for example, can be used for eyewear such as sunglasses or eyewear for Augmented Reality (AR) or Virtual Reality (VR), exterior walls of buildings or sunroofs for vehicles, etc. In one example, the optical device can be a sunroof for vehicles in and of itself. For example, in a vehicle including a body having at least one opening formed therein, the optical device or sunroof for vehicles can be mounted and used by mounting it in the opening.

The optical device of the present application can secure structural stability and good quality uniformity by properly maintaining the cell gap of the liquid crystal element and having excellent adhesion between the upper and lower substrates, and minimizing defects such as pressing or crowding during the bonding process of the outer substrate.

FIG. 1 is a cross-sectional view of an exemplary optical device of the present application.
Figure 2 is a cross-sectional view of an exemplary liquid crystal device of the present application.
Figure 3 is an image of an optical device manufactured in an example and a comparative example.
Figure 4 shows the results of measuring transmittance for optical devices manufactured in examples and comparative examples.

The present application is specifically described through the following examples, but the scope of the present application is not limited by the following examples.

Measurement Example 1. Measurement of storage elastic modulus

The storage modulus was measured using TA's DMA Q800. Specifically, the storage modulus values were recorded under the conditions of temperature 25℃, Force 0.01N, and Ramp rate 3 °/min in Multi-Frequency-Strain mode.

Example 1

Liquid crystal device manufacturing

A polycarbonate film (Keiwa) having a thickness of about 100 μm and a length x width area of 600 mm x 300 mm was prepared as the first substrate layer. ITO (indium-tin-oxide) was deposited to a thickness of 50 nm on the first substrate layer to form a first electrode layer. An adhesive composition (KR-3700, Shin-Etsu Corporation) was bar-coated on the first electrode layer, and then dried at about 150° C. for about 5 minutes to form an adhesive layer having a thickness of about 10 μm. The storage modulus of the adhesive layer was about 0.1 MPa. The combination of the first substrate layer, the first electrode layer, and the adhesive layer is referred to as an upper substrate.

A polycarbonate film (Keiwa) having a thickness of approximately 100 μm and a length x width area of 600 mm x 300 mm was prepared as a second substrate layer. A second electrode layer was formed by depositing ITO (indium-tin-oxide) with a thickness of 50 nm on the second substrate layer. An acrylic resin composition (KAD-03, Minutatech) was coated on the second electrode layer, and then a honeycomb-shaped spacer was formed by a photolithography method. The pitch of the regular hexagons (closed shapes) constituting the honeycomb was approximately 450 μm, the height was approximately 12 μm, and the line width was approximately 30 μm. The area of the closed shapes (regular hexagons) formed by the spacer was approximately 2.14 mm ² . A vertical alignment film (Nissan, SE-5661) was coated on the above spacer with a thickness of about 300 nm, and then rubbed in one direction. The combination of the second base layer, the second electrode layer, the spacer, and the horizontal alignment film is referred to as the lower substrate.

A liquid crystal composition was coated on a vertical alignment film of a lower substrate to form a liquid crystal layer, and then an adhesive layer of an upper substrate was laminated so that it faced the coated surface of the liquid crystal composition. The liquid crystal composition contained a liquid crystal compound (Merck, MAT-16-568) and a chiral dopant (HCCH, S811), and the pitch (p) of the liquid crystal layer formed as described above was about 20 μm.

Optical device manufacturing

A laminate was prepared, which sequentially includes a first outer substrate, a first intermediate layer, a first polarizer, a second intermediate layer, a liquid crystal element manufactured as described above, a third intermediate layer, a second polarizer, a fourth intermediate layer, and a second outer substrate, and which includes an outer layer surrounding a side surface of the liquid crystal element. The second outer substrate was arranged in the direction of gravity relative to the first outer substrate.

The first polarizer and the second polarizer are each PVA-based polarizers, and the light transmission axes of the first polarizer and the second polarizer are arranged to form an angle of approximately 90 degrees. A glass substrate having a thickness of approximately 3 mm, an area of (width x length = 300 mm x 300 mm), and a radius of curvature of approximately 2,470R was used as the first outer substrate. A glass substrate having a thickness of approximately 3 mm, an area of (width x length = 300 mm x 300 mm), and a radius of curvature of approximately 2,400R was used as the second outer substrate. The second intermediate layer and the third intermediate layer are each a single-layer TPU layer (Argotec) having a thickness of approximately 380 μm. The first intermediate layer and the fourth intermediate layer are each a laminate of three TPU layers (Argotec) having a thickness of approximately 380 μm. The above TPU layer (Argotec) has a coefficient of thermal expansion of 307 ppm/K and a storage modulus of 8 to 15 MPa. The outer layer was formed of the same material as the intermediate layer. An autoclave process was performed on the laminate at a temperature of about 110° C. and a pressure of about 2 atm to produce an optical device having the structure of FIG. 1. In the optical device of Example 1, the thicknesses of the second intermediate layer and the third intermediate layer were each about 380 μm, and the total thickness of the intermediate layers was about 3,040 μm.

Comparative Example 1

An optical device was manufactured by performing the same process as in Example 1, except that the first intermediate layer and the fourth intermediate layer were each changed to a single TPU layer (Argotec) having a thickness of approximately 380 μm, and that the first intermediate layer and the fourth intermediate layer were each changed to a laminate of three TPU layers (Argotec) having a thickness of approximately 380 μm per layer. In the optical device of Comparative Example 1, the total thickness of the intermediate layers was approximately 3,040 μm.

Evaluation Example 1. Observation of light leakage

FIG. 3 is a photograph (Olympus, BX51-N33MB) taken of optical devices manufactured in Examples and Comparative Examples under no voltage applied. FIG. 3 (a) and (b) are images of Example 1 and Comparative Example 1, respectively, under no voltage applied, and FIG. 3 (c) and (d) are images of Example 1 and Comparative Example 1, respectively, under a 50 V voltage applied. From FIG. 3 (a) and (b), it can be observed that Example 1 has less light leakage under no voltage applied than Comparative Example 1.

Evaluation Example 2. Evaluation of electro-optical characteristics

For the optical devices manufactured in the examples and comparative examples, the omnidirectional (azimuth angle 0° to 360°) transmittance was measured at a polar angle of 60°, and the results are shown in Fig. 4. The transmittance was measured using a haze meter (CA-2500, manufactured by Konica Minolta Co., Ltd.) in a state where no voltage was applied to the optical device. The transmittance is the average transmittance for light having a wavelength of 380 nm to 780 nm, and a lower transmittance means less light leakage. In Fig. 4, relative transmittance means the relative transmittance when the backlight amount is viewed as 100%. An azimuth angle of 0° is parallel to the rubbing axis of the alignment film of the liquid crystal element. Example 1 and Comparative Example 1 each exhibited the maximum transmittance at an azimuth of 110°, with Example 1 exhibiting a transmittance of 5.51% at an azimuth of 110° and Comparative Example 1 exhibiting a transmittance of 6.03% at an azimuth of 110°. In addition, Example 1 and Comparative Example 1 exhibited the greatest difference in transmittance at an azimuth of 60°, with Example 1 exhibiting a transmittance of 3.17% at an azimuth of 60° and Comparative Example 1 exhibiting a transmittance of 4.04% at an azimuth of 60°.

100a: first outer substrate, 100b; second outer substrate, 200a: first polarizer, 200b: second polarizer, 300a, 300b, 300c, 300d: intermediate layer, 400: liquid crystal element, 500: outer layer, 10a: first substrate layer, 10b: first electrode layer, 10c: adhesive layer, 20a: second substrate layer, 20b: second electrode layer, 20c: spacer, 20d: alignment film

Claims (18)

A first outer substrate; a second outer substrate positioned opposite to the first outer substrate;
A liquid crystal element positioned between the first outer substrate and the second outer substrate;
A first polarizer positioned between the first outer substrate and the liquid crystal element;
A second polarizer positioned between the second outer substrate and the liquid crystal element; and
It comprises at least one intermediate layer positioned between the first outer substrate and the liquid crystal element, and between the second outer substrate and the liquid crystal element,
The optical transmission axis of the first polarizer and the optical transmission axis of the second polarizer are perpendicular to each other,
The liquid crystal element includes a first substrate layer, an adhesive layer formed on the inner side of the first substrate layer, a second substrate layer positioned opposite the first substrate layer, a spacer formed on the inner side of the second substrate layer, and a liquid crystal layer positioned between the first substrate layer and the second substrate layer.
The sum of the thicknesses of all intermediate layers existing between the first outer substrate and the liquid crystal element film and between the second outer substrate and the liquid crystal element film is 1,520 ㎛ or more,
An optical device comprising at least one intermediate layer positioned between the first polarizer and the liquid crystal element and between the second polarizer and the liquid crystal element, and having a thickness of 380 μm or less. delete An optical device according to claim 1, wherein each of the first outer substrate and the second outer substrate is a glass substrate. An optical device according to claim 1, wherein at least one intermediate layer is positioned between the first outer substrate and the first polarizer, and between the second outer substrate and the second polarizer. An optical device in accordance with claim 4, wherein the thickness of the intermediate layers positioned between the first outer substrate and the first polarizer, and between the second outer substrate and the second polarizer, respectively, is greater than the thickness of the intermediate layers positioned between the first polarizer and the liquid crystal element, and between the second polarizer and the liquid crystal element, respectively. delete delete An optical device according to claim 1, wherein the storage modulus of the adhesive layer is in the range of 0.01 MPa to 1 MPa. An optical device according to claim 1, wherein the liquid crystal layer further comprises a dichroic dye. In the first aspect, the liquid crystal layer is an optical device that switches between a first alignment state and a second alignment state different from the first alignment state through application of external energy. An optical device in accordance with claim 1, wherein the ratio (B/A) of the area (B) of the spacer to the area (A) of the second substrate layer is in the range of 5% to 50%. An optical device, in claim 1, further comprising a first electrode layer formed on an inner surface of a first substrate layer and a second electrode layer present on an inner surface of a second substrate layer, wherein the adhesive layer is present on the inner surface of the first electrode layer and the spacer is present on the inner surface of the second electrode layer. An optical device in accordance with claim 12, wherein the liquid crystal element further includes an alignment film present on the inner surface of the second electrode layer, and the inner surface of the first substrate layer does not include an alignment film. An optical device in claim 1, wherein the storage modulus of at least one intermediate layer is in the range of 1 MPa to 100 MPa. An optical device in accordance with claim 1, wherein the Young's modulus of at least one intermediate layer is in a range of 0.1 MPa to 100 MPa. An optical device in accordance with claim 1, wherein each of the thermal expansion coefficients of at least one intermediate layer is 2,000 ppm/K or less. An optical device in claim 1, wherein at least one intermediate layer is each a thermoplastic polyurethane adhesive layer, a polyamide adhesive layer, a polyester adhesive layer, an EVA (Ethylene Vinyl Acetate) adhesive layer, an acrylic adhesive layer, a silicone adhesive layer, or a polyolefin adhesive layer. A vehicle comprising a body having one or more openings formed therein; and an optical device according to any one of claims 1, 3 to 5, and 8 to 17 mounted in the openings.