Variable transmittance optical laminate and smart window including the same

Abstract

The present invention relates to a variable transmittance optical stack including a first laminate in which a first polarizer including a first hard coating layer, a first transparent conductive layer, and a first alignment film are sequentially stacked; a second laminate in which a second polarizer including a second hard coating layer, a second transparent conductive layer, and a second alignment film are sequentially stacked; and a liquid crystal layer disposed between the first alignment film and the second alignment film, wherein at least one of the first transparent conductive layer and the second transparent conductive layer is formed in direct contact with one of the first polarizer and the second polarizer, and includes ball spacers embedded and fixed in at least one of the first hard coating layer and the second hard coating layer to maintain a gap between layers above and below the liquid crystal layer, wherein the diameter A of the ball spacers is 3 to 14 μm, the thickness B of the hard coating layer embedding the ball spacers is 1 to 10 μm, and the value of AB is 2 to 10 μm. This invention also relates to a method for manufacturing the variable transmittance optical stack, a smart window including the same, and a means of transportation, automobiles, wearable devices, and building fixtures using the same.

Description

[Technical Field]

[0001] The present invention relates to a variable transmittance optical laminate, a method for manufacturing the same, and a smart window including the same. [Background technology]

[0002] Generally, glass windows of vehicles such as cars are often coated with an external light blocking coating. However, conventional glass windows of vehicles have a fixed transmittance, and the external light blocking coating also has a fixed transmittance. Therefore, such conventional vehicle windows have a fixed overall transmittance, which can lead to accidents. For example, if the overall transmittance is set low, there is no problem during the day when there is sufficient surrounding light. However, there is a problem that drivers have difficulty properly checking the surroundings of the vehicle when there is insufficient surrounding light, such as at night. Alternatively, if the overall transmittance is set high, there is a problem that drivers may experience glare during the day when there is sufficient surrounding light. For this reason, a light-control laminate capable of changing light transmittance when a voltage is applied has been developed.

[0003] The variable transmittance optical stack is driven by applying a voltage to drive the liquid crystal to change the transmittance. The variable transmittance optical stacks developed to date are manufactured by forming a conductive layer for driving the liquid crystal on a separate substrate and combining it with other elements such as a polarizer.

[0004] Korean Patent Publication No. 10-2017-0072573 is an invention relating to a liquid crystal window for an optical element and an optical element, and discloses a laminate including a liquid crystal layer whose transmittance changes depending on whether or not an external action (external force) is applied, and which can minimize spacer movement by fixing a portion of a spacer to one of the alignment films located on both sides of the liquid crystal layer. However, in this case, the spacer recessed in the alignment film may be pressed, causing damage to the alignment film, which may cause defects due to light leakage and degrade optical performance.

[0005] Therefore, there is a need to develop a variable transmittance optical laminate that can maintain a uniform cell gap of the liquid crystal, minimize current shorts in the laminate, maintain a constant in-plane optical color, and minimize liquid crystal defects. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Korean Patent Publication No. 10-2017-0072573 Summary of the Invention [Problem to be solved by the invention]

[0007] In order to solve the above problems, an object of the present invention is to provide a variable transmittance optical laminate in which spacers are fixed in a form in which they are recessed into one of a first hard coating layer and a second hard coating layer, thereby minimizing the movement of the spacers.

[0008] Another object of the present invention is to provide a variable transmittance optical laminate in which the appearance and / or liquid crystal color of the variable transmittance optical laminate is uniform and which has excellent optical properties.

[0009] Another object of the present invention is to provide a variable transmittance optical laminate that does not require a separate substrate for forming a conductive layer, thereby simplifying the manufacturing process.

[0010] Another object of the present invention is to provide a smart window including the variable transmittance optical laminate, and an automobile or building fixture to which the smart window is applied.

[0011] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0012] The present invention relates to a variable transmittance optical stack including: a first stack in which a first polarizer including a first hard coating layer, a first transparent conductive layer, and a first alignment film are sequentially stacked; a second stack in which a second polarizer including a second hard coating layer, a second transparent conductive layer, and a second alignment film are sequentially stacked; and a liquid crystal layer disposed between the first alignment film and the second alignment film, wherein at least one of the first transparent conductive layer and the second transparent conductive layer is formed in direct contact with one of the first polarizer and the second polarizer, and ball spacers are embedded in at least one of the first hard coating layer and the second hard coating layer to maintain a gap between layers above and below the liquid crystal layer, wherein a diameter A of the ball spacers is 3 to 14 μm, a thickness B of one of the first hard coating layer and the second hard coating layer embedding the ball spacers is 1 to 10 μm, and a value of AB is 2 to 10 μm.

[0013] In the present invention, the thickness of the first alignment film and the second alignment film may be independently 30 to 300 nm.

[0014] The present invention may be characterized in that when the respective optical axes of the first polarizer and the second polarizer are aligned at 0°, they are driven in VA (Vertical alignment) mode, and when they are aligned at 90°, they are driven in TN (Twisted nematic) mode.

[0015] In the present invention, the average recession depth of the ball spacer into the hard coating layer may be more than 50% of the thickness of the hard coating layer.

[0016] In the present invention, at least one of the first transparent conductive layer and the second transparent conductive layer may include an easy-adhesion layer between the transparent conductive layer and one of the first polarizing plate and the second polarizing plate, and may be formed in direct contact with the transparent conductive layer.

[0017] In the present invention, at least one of the first polarizing plate and the second polarizing plate may include at least one layer selected from the group consisting of a protective layer, a retardation adjusting layer, and a refractive index adjusting layer.

[0018] In the present invention, at least one of the first polarizing plate and the second polarizing plate may have a thickness of 30 to 200 μm.

[0019] In the present invention, the area occupied by the ball spacers in the liquid crystal layer may be 0.01 to 10% of the area of ​​the liquid crystal layer.

[0020] In the present invention, the variable transmittance optical laminate may further include one or more layers selected from the group consisting of an adhesive layer, an ultraviolet absorbing layer, and an impact resistant layer.

[0021] The present invention also relates to a method for producing the variable transmittance optical laminate.

[0022] The present invention also relates to a smart window comprising the variable transmittance optical laminate.

[0023] The present invention also relates to a smart window in which glass is bonded to one or both surfaces of the variable transmittance optical laminate.

[0024] The present invention also relates to a means of transportation including said smart window.

[0025] The present invention also relates to a vehicle in which the smart window is applied to at least one of a front window, a rear window, a side window, a sunroof window, and an interior partition.

[0026] The present invention also relates to a wearable device including the smart window.

[0027] The present invention also relates to architectural fittings including the smart window. [Effects of the Invention]

[0028] According to the variable transmittance optical laminate of the present invention, the ball spacers are fixed in a recessed form in the hard coating layer, minimizing the movement of the ball spacers, thereby preventing damage to the laminate. In particular, by preventing damage to the alignment layer due to the movement of the ball spacers, light leakage between the liquid crystal layer and other laminates can be prevented.

[0029] In addition, according to the variable transmittance optical laminate of the present invention, the diameter A of the ball spacers is 3 to 14 μm, the thickness B of the hard coating layer of the first hard coating layer and the second hard coating layer that envelops the ball spacers is 1 to 10 μm, and the value of AB is 2 to 10 μm. By satisfying these ranges, the liquid crystal cell gap maintaining property is excellent and a constant optical color can be maintained in the plane.

[0030] In addition, according to the variable transmittance optical laminate of the present invention, a conductive layer is formed directly on one side of a polarizer, so a separate substrate for forming the conductive layer is not required, and processes such as dispersing spacers can be omitted, thereby simplifying the manufacturing process compared to conventional optical laminates.

[0031] By applying the variable transmittance optical laminate according to the present invention, it is possible to provide a smart window with excellent device reliability, and to provide transportation means, automobiles, wearable devices, and building fixtures using the same. [Brief explanation of the drawings]

[0032] [Figure 1] FIG. 1 is a cross-sectional view showing the layer structure of a variable transmittance optical laminate according to an embodiment of the present invention. [Figure 2]FIG. 2 is an enlarged cross-sectional view showing a spacer recessed portion of a variable transmittance optical laminate according to an embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view showing the layer structure of a variable transmittance optical layered body according to another embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view showing a laminated structure of a smart window for a vehicle according to an embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view showing the layered structure of a smart window for architectural fittings according to one embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view showing a layered structure of a smart window for architectural fittings according to another embodiment of the present invention. [Figure 7] FIG. 7 is a process diagram showing a manufacturing process of a variable transmittance optical laminate according to an embodiment of the present invention. [Figure 8] FIG. 8 is a diagram showing the appearance of a portion where black amorphous irregularities have occurred in a variable transmittance optical laminate. [Figure 9] FIG. 9 is a diagram showing the appearance of a portion where liquid crystal unevenness occurs on the surface of the variable transmittance optical laminate. [Figure 10] FIG. 10 is a diagram showing the appearance of a portion where light leakage occurs on the surface of the variable transmittance optical laminate. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention relates to a variable transmittance optical laminate, which maintains a uniform cell gap by fixing ball spacers to a hard coating layer to minimize spacer movement, and has excellent optical properties and improved reliability, a manufacturing method thereof, and a smart window including the same.

[0034] More specifically, the present invention relates to a variable transmittance optical stack including: a first stack in which a first polarizer including a first hard coating layer, a first transparent conductive layer, and a first alignment film are sequentially stacked; a second stack in which a second polarizer including a second hard coating layer, a second transparent conductive layer, and a second alignment film are sequentially stacked; and a liquid crystal layer disposed between the first alignment film and the second alignment film, wherein at least one of the first transparent conductive layer and the second transparent conductive layer is formed in direct contact with one of the first polarizer and the second polarizer, and ball spacers are embedded in at least one of the first hard coating layer and the second hard coating layer to maintain a gap between layers above and below the liquid crystal layer, wherein a diameter A of the ball spacers is 3 to 14 μm, a thickness B of the hard coating layer of the first hard coating layer and the second hard coating layer embedding the ball spacers is 1 to 10 μm, and a value of AB is 2 to 10 μm.

[0035] The variable transmittance optical laminate of the present invention is particularly suitable for technical fields in which light transmittance can be changed by applying a voltage, and may be used, for example, in smart windows.

[0036] A smart window is an optical structure that controls the amount of light or heat passing through by changing its light transmittance in response to the application of an electrical signal. That is, a smart window can be changed between transparent, opaque, or translucent depending on the voltage applied, and is also called variable transmittance glass, light-control glass, or smart glass.

[0037] Smart windows can be used to divide the interior space of vehicles and buildings or as partitions for privacy, or as light windows placed in openings in buildings. They can also be used for highway signs, bulletin boards, odometers, clocks, or advertising screens, and can be used to replace glass in vehicles such as windows or sunroofs in automobiles, buses, airplanes, ships, or trains.

[0038] The light-control laminate of the present invention can also be used in smart windows in the various technical fields mentioned above. However, since the transparent conductive layer is formed directly on the polarizer, no separate substrate is required for forming the conductive layer, resulting in a thin thickness and advantageous flexibility, making it particularly suitable for use in smart windows for vehicles or buildings. In one or more embodiments, smart windows using the light-control laminate of the present invention can be used in transportation, such as front windows, rear windows, side windows, and sunroofs of automobiles, or building fixtures. In addition to applications in blocking external light, they can also be used to divide the interior space of automobiles or buildings, such as interior partitions, or for privacy protection. They can also be used in wearable devices such as helmets, glasses, and watches.

[0039] Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. However, the following drawings attached to this specification are intended to illustrate preferred embodiments of the present invention and, together with the above-described invention content, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited only to the matters depicted in these drawings.

[0040] The terms used herein are for the purpose of describing the embodiments and are not intended to limit the present invention. In this specification, the singular includes the plural unless otherwise specified. For example, the term "polarizer" used herein may refer to at least one polarizer selected from a first polarizer and a second polarizer, the term "transparent conductive layer" may refer to at least one transparent conductive layer selected from a first transparent conductive layer and a second transparent conductive layer, and the term "hard coating layer" may refer to at least one hard coating layer selected from a first hard coating layer and a second hard coating layer.

[0041] As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components, steps, operations and / or elements other than the stated components, steps, operations and / or elements. Like reference numerals refer to like elements throughout the specification.

[0042] Spatially relative terms such as "below," "bottom," "lower," "upper," "top," "top," and the like may be used to easily describe the relationship of one element or component to another, as illustrated in the figures. Spatially relative terms should be understood to encompass different orientations of elements in use or operation in addition to the orientation depicted in the figures. For example, if an element depicted in the figures is inverted, an element described as "below" or "below" another element may also be positioned "above" the other element. Thus, the exemplary term "below" may encompass both an orientation of below and above. Elements may be oriented in other directions, and thus the spatially relative terms may be interpreted accordingly.

[0043] As used herein, "substantially" can be interpreted not only to mean completely identical or identical to something, but also to mean being within the error range of measurement or manufacturing processes, for example, being within an error range of 0.1% or less.

[0044] 1 and 2, a variable transmittance optical stack according to an embodiment of the present invention may include a first stack, a second stack, and a liquid crystal layer 500. The first stack may include a first polarizer 100-1 including a first polarizer 110-1 and a first hard coating layer 120-1, a first transparent conductive layer 200-1, and a first alignment film 300-1, and the second stack may include a second polarizer 100-2 including a second polarizer 110-2 and a second hard coating layer 120-2, and a second transparent conductive layer 200-2. In an embodiment of the present invention, the ball spacers 400 are embedded in the first hard coating layer 120-1, but the present invention is not limited to this, as long as the first hard coating layer 120-1 or the second hard coating layer 120-2 is at least one of the hard coating layers.

[0045] 3, a variable transmittance optical laminate according to another embodiment of the present invention may further include an adhesive layer 700 on the outermost surface of the laminate. More specifically, referring to FIGS. 4 to 6, in one embodiment, a smart window may include the variable transmittance optical laminate, an adhesive layer 700, and glass sheets 800 and 900.

[0046] The polarizer 110 may be a conventional or later developed polarizer, for example, a stretched polarizer or a coated polarizer.

[0047] In one embodiment of the present invention, the polarizer 110 is preferably a stretched polarizer from the viewpoint of ease of processing. The stretched polarizer may include, for example, a stretched polyvinyl alcohol (PVA)-based resin. The polyvinyl alcohol-based resin may preferably be a polyvinyl alcohol-based resin obtained by saponifying a polyvinyl acetate-based resin. Examples of polyvinyl acetate-based resins include polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as copolymers of vinyl acetate with other monomers copolymerizable therewith. Examples of such other monomers include unsaturated carboxylic acid-based, unsaturated sulfonic acid-based, olefin-based, vinyl ether-based, and acrylamide-based monomers having an ammonium group. The polyvinyl alcohol-based resin may also be modified, such as polyvinyl formal or polyvinyl acetal modified with aldehydes.

[0048] In one embodiment, the coating type polarizer may be formed using a liquid crystal coating composition, and the liquid crystal coating composition may include a reactive liquid crystal compound and a dichroic dye.

[0049] The reactive liquid crystal compound may include, for example, a monomer molecule including a reactive mesogen (RM) and a polymerizable terminal functional group, and having a liquid crystal phase after a crosslinking reaction by heat or light. When the reactive liquid crystal compound is polymerized by light or heat, it can form a polymer network while maintaining the liquid crystal alignment.

[0050] The reactive liquid crystal compound may be a monofunctional or polyfunctional reactive liquid crystal compound. The monofunctional reactive liquid crystal compound is a compound having one polymerizable functional group, and the polyfunctional reactive liquid crystal compound is a compound having two or more polymerizable functional groups.

[0051] The dichroic dye is a component contained in the liquid crystal coating composition that imparts polarization properties and has a property that the absorbance in the long axis direction of the molecule is different from the absorbance in the short axis direction. Non-limiting examples of the dichroic dye include acridine dyes, oxazine dyes, cyanine dyes, naphthalene dyes, azo dyes, anthraquinone dyes, etc. These may be used alone or in combination of two or more.

[0052] The liquid crystal coating composition may further contain a solvent capable of dissolving the reactive liquid crystal compound and the dichroic dye, such as propylene glycol monomethyl ether acetate (PGMEA), methyl ethyl ketone (MEK), xylene, chloroform, etc. The liquid crystal coating composition may further contain a labeling agent, a polymerization initiator, etc., within a range that does not impair the polarization properties of the coating film.

[0053] The hard coating layer 120 is provided to improve the hardness of the polarizer 100 and is not particularly limited as long as it can improve the hardness of the polarizer. Any conventional or later-developed hard coating layer may be used. According to one embodiment of the present invention, the hard coating layer 120 may be formed from a hard coating composition including an acrylate-based or epoxy-based compound, inorganic particles, a photoinitiator, etc. The acrylate-based compound may include a monomer or oligomer containing a (meth)acrylate group. As used herein, the term "(meth)acrylic-" refers to either "methacrylic-", "acrylic-", or both. Non-limiting examples of the acrylate compound include neopentyl glycol acrylate, 1,6-hexanediol (meth)acrylate, propylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolethane tri(meth)acrylate, 1,2,4-cyclohexane tetra(meth)acrylate, pentaglycerol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol tri(meth)acrylate, and dipentaerythritol tri(meth)acrylate. acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol tri(meth)acrylate, tripentaerythritol hexatri(meth)acrylate, bis(2-hydroxyethyl)isocyanurate di(meth)acrylate, hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, hydroxybutyl (meth)acrylate, isooctyl (meth)acrylate, iso-dexyl (meth)acrylate, stearyl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, phenoxyethyl (meth)acrylate, or isoborneol (meth)acrylate.These may be used alone or in combination of two or more. The acrylate compound may include an epoxy (meth)acrylate compound and / or a urethane (meth)acrylate compound. The epoxy compound may also include a monomer or oligomer having at least one epoxy group in the molecule. The epoxy group may be an alicyclic epoxy group. The alicyclic ring contained in the epoxy group may have 3 to 7 carbon atoms, for example, an alicyclic epoxy group containing a cyclohexane ring (cyclohexyl epoxy). The alicyclic ring may have a substituent. For example, the alicyclic ring may include an alkyl substituent having 1 to 20 carbon atoms. If the carbon number of the alkyl substituent exceeds 20, it may be disadvantageous in terms of curing speed. The alkyl substituent may be linear or branched, and if branched, the carbon number may be 3 or more.

[0054] According to one embodiment of the present invention, in a method for manufacturing a hard coating layer, the hard coating composition includes inorganic fine particles. The inorganic fine particles may be nano-sized particles, e.g., particles having a particle size of 100 nm or less, preferably 10 to 100 nm, and more preferably 10 to 50 nm. Examples of the inorganic fine particles include silica fine particles, aluminum oxide particles, titanium oxide particles, and zinc oxide particles.

[0055] The inclusion of the inorganic fine particles can further improve the hardness of the hard coating layer. According to one embodiment of the present invention, the inorganic fine particles may be included in an amount of 10 to 60 parts by weight, preferably 20 to 50 parts by weight, based on 100 parts by weight of the hard coating composition. By including the inorganic fine particles in this range, the hardness of the hard coating layer can be improved without deteriorating the physical properties of the hard coating composition.

[0056] In one embodiment of the present invention, in a method for manufacturing a hard coating layer, the hard coating composition includes a photoinitiator, such as, but not limited to, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-1-[4-(2-hydroxyethoxy)phenyl]-2-methyl-1-propanone, methylbenzoyl formate, α,α-dimethoxy-α-phenylacetophenone, 2-benzoyl-2-(dimethylamino)-1-[4-(4-morpholine)phenyl]-1-butanone, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholine)-1-propanonediphenyl(2,4,6-trimethylbenzoyl)-phosphine oxide, or bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide. Currently available products include Irgacure 184, Irgacure 500, Irgacure 651, Irgacure 369, Irgacure 907, Darocur 1173, Darocur MBF, Irgacure 819, Darocur TPO, Irgacure 907, and Esacure KIP 100F.

[0057] These photoinitiators can be used alone or in combination of two or more different types.

[0058] According to one embodiment of the present invention, the photoinitiator may be included in an amount of 0.5 to 10 parts by weight, preferably 1 to 5 parts by weight, based on 100 parts by weight of the hard coating composition. When the photoinitiator is included in this range, sufficient cross-linking photopolymerization can be achieved while reducing the physical properties of the hard coating film.

[0059] Meanwhile, in the method for preparing a hard coating layer according to the present invention, the hard coating composition may further contain additives commonly used in the technical field to which the present invention pertains, such as a surfactant, an anti-yellowing agent, a labeling agent, or an antifouling agent, in addition to the above-mentioned components. The content of these additives is not particularly limited, as they can be variously adjusted within a range that does not deteriorate the physical properties of the hard coating composition according to the present invention.

[0060] The hard coating layer 120 may be used alone or in one embodiment as a multi-layer structure. The hard coating layer 120 may be formed on one surface of the polarizer 110 in direct contact with the polarizer 110 as shown in FIG. 1, but is not limited thereto. For example, when the polarizer includes a retardation control layer and / or a refractive index control layer, the hard coating layer 120 may be formed on one surface of the retardation control layer and the refractive index control layer, and the hard coating layer, the retardation control layer, the refractive index control layer, and the polarizer may be sequentially stacked.

[0061] The hard coating layer 120 is preferably formed on the liquid crystal layer 500 side of the polarizer 110, i.e., on the inner side of the polarizer 110, but is not limited thereto. The hard coating layer 120 may also be formed on the outer side of the polarizer 110, and the polarizer 110, hard coating layer 120, and protective layer (not shown) may be sequentially stacked. For example, the first hard coating layer 120-1 and the second hard coating layer 120-2 may be formed on the inner sides of the first polarizer 110-1 and the second polarizer 110-2, respectively, and arranged to face each other. In this case, the hard coating layer provides a level of hardness suitable for forming members such as a transparent conductive layer on the polarizer, thereby minimizing cracks and scratches that may occur during the manufacturing or processing of the optical laminate.

[0062] The hard coating layer 120 may have a Vickers hardness of 18 to 41. The Vickers hardness may be measured using a Vickers tip of a nanoindenter (HM500, Helmut Fischer) at a loading and unloading rate of 300 mN / 20 seconds, a creep time of 5 seconds, and a maximum load of 100 mN. When the Vickers hardness of the functional coating layer satisfies the above range, the functional coating layer may have excellent abrasion resistance and may further improve the flex resistance and durability of the optical laminate. More specifically, the occurrence of defects such as cracks in the conductive layer due to pressure applied by spacers or chemical reactions between liquid crystals, alignment layers, etc. during the bonding process of the optical laminate may be more effectively prevented.

[0063] In one embodiment, the hard coating layer 120 may have a thickness of 1 to 50 μm, and more preferably 1 to 40 μm. The first hard coating layer 120-1 and the second hard coating layer 120-2 each have a thickness of 1 to 10 μm. The thickness may refer to the thickness after drying. If the thickness of the hard coating layer 120 satisfies this range, the hard coating layer 120 may have excellent hardness, be thin, and have improved flex resistance and durability. If the thickness of the hard coating layer 120-1 and the second hard coating layer 120-2 each have a thickness exceeding this range, the ball spacers may not be sufficiently embedded, which may result in problems with the uniformity of the liquid crystal layer thickness and visibility of the device.

[0064] According to one embodiment of the present invention, at least one of the first hard coating layer 120-1 and the second hard coating layer 120-2 may have ball spacers embedded therein. The spacers serve to maintain a constant cell gap of the liquid crystal layer and may include at least one of ball spacers and column spacers. In one embodiment of the present invention, ball spacers 400 are preferred from the viewpoint of processability. In one embodiment of the present invention, a hard coating layer having ball spacers embedded therein may be manufactured by mixing ball spacers into a hard coating composition and then subjecting the hard coating composition to a drying and curing process. The ball spacers are positioned and fixed in the hard coating layer before curing, thereby minimizing spacer flow and preventing damage to the laminate due to pressure from the ball spacers. In particular, damage to the alignment layer due to ball spacer flow can be prevented, the incidence of defects such as light leakage between the liquid crystal layer and other laminates can be reduced, and a consistent in-plane optical color can be maintained.

[0065] Furthermore, the process of dispersing a separate spacer can be omitted, simplifying the manufacturing process compared to conventional optical laminates. The ball spacer 400 may be one or more, and preferably has a diameter of 3 to 14 μm to support the liquid crystal layer.

[0066] Also, when viewed from the planar direction, the area of ​​the ball spacers 400 in the liquid crystal layer is preferably 0.01 to 10% of the area of ​​the liquid crystal layer in terms of improving user visibility and transmittance in the light-transmitting mode.

[0067] 2 is an enlarged cross-sectional view showing a spacer recess in a variable transmittance optical laminate according to one embodiment of the present invention. Referring to FIG. 2, the average recession depth d of the ball spacer 400 in the hard coating layer according to one embodiment of the present invention preferably exceeds 50% of the hard coating layer thickness t in order to improve the adhesion of the ball spacer. Most preferably, the ball spacer is completely sunk into the hard coating composition before the hard coating layer is cured, and is recessed and adhered while in contact with the lower surface of the hard coating layer, i.e., the upper surface of the layer that abuts the lower surface of the hard coating layer. If the recession depth d of the ball spacer 400 in the hard coating layer is below this range, the ball spacer may not adhere sufficiently to the hard coating layer during curing, and the transparent conductive layer formed on the hard coating layer and the ball spacer may not be uniformly formed, potentially resulting in a current short circuit.

[0068] In addition, in one embodiment of the present invention, when the ball spacers 400 are embedded in the first hard coating layer 120-1, the first laminate may have a laminate structure including a first polarizer 110-1, a first hard coating layer 120-1 formed on one side of the first polarizer 110-1, a plurality of ball spacers 400 embedded in the first hard coating layer 120-1, a first transparent conductive layer 200-1 formed on the first hard coating layer 120-1 embedded with the plurality of ball spacers 400, and a first alignment film 300-1 formed on the first transparent conductive layer 200-1.

[0069] In one embodiment of the present invention, it is preferable that the value obtained by subtracting the thickness B of the hard coating layer enveloping the ball spacer from the diameter A of the ball spacer is 2 to 10 μm. When this range is satisfied, the liquid crystal color is formed uniformly, and the appearance of the device including the variable transmittance optical stack according to the present invention can be formed well.

[0070] The protective layer (not shown) may be formed on one or both surfaces of the polarizer in direct contact therewith, but is not limited thereto. For example, the protective layer may be used as a multi-layer structure in which one or more protective layers are continuously stacked, or may be formed on another member such as a retardation adjusting layer in direct contact therewith.

[0071] In one embodiment, the protective layer may include one or more selected from the group consisting of polyethylene terephthalate (PET), polyethylene isophthalate (PEI), polyethylene naphthalate (PEN), polybutylene terephthalate (PBT), diacetyl cellulose, triacetyl cellulose (TAC), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polymethyl acrylate (PMA), polymethyl methacrylate (PMMA), polyethyl acrylate (PEA), polyethyl methacrylate (PEMA), and cyclic olefin polymer (COP).

[0072] In addition, the protective layer may further contain an ultraviolet absorber on the outermost surface to prevent deterioration of the optical laminate. The ultraviolet absorber is not particularly limited as long as it prevents deterioration of the optical laminate due to ultraviolet rays, and examples thereof include salicylic acid-based ultraviolet absorbers (phenyl salicylate, p-tert-butyl salicylate, etc.), benzophenone-based ultraviolet absorbers (2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, etc.), benzotriazole-based ultraviolet absorbers (2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-t 2-(2'-hydroxy-3'-tert-butylphenyl)benzotriazole, 2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-(3'',4'',5'',6''-tetrahydrophthalimidomethyl)-5'-methylphenyl)benzotriazole, 2,2-methylenebis(4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazo 2-(2'-hydroxy-3'-tert-butyl-5'-methylphenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-tert-butyl-5'-(2-octyloxycarbonylethyl)-phenyl)-5-chlorobenzotriazole, 2-(2'-hydroxy-3'-(1-methyl-1-phenylethyl)-5'-(1,1,3,3-tetramethylbutyl)-phenyl)benzotriazole, 2-(2H-benzotriazol-2-yl)-6-(linear and side chain dodecyl)-4-methylphenol, a mixture of octyl-3-[3-tert-butyl-4-hydroxy-5-(chloro-2H-benzotriazol-2-yl)phenyl]propionate and 2-ethylhexyl-3-[3-tert-butyl-4-hydroxy-5-(5-chloro-2H-benzotriazol-2-yl)phenyl]propionate, etc.), cyanoacrylate ultraviolet absorbers (2'-ethylhexyl-2-cyano-3,3-diphenylacrylate, ethyl-2-cyano-3-(3',4'-methylenedioxyphenyl)acrylate, triazine-based UV absorbers, etc. may also be used, and benzotriazole-based UV absorbers or triazine-based UV absorbers, which have high transparency and are excellent in preventing deterioration of polarizing plates and transmittance-variable layers, are preferred, and benzotriazole-based UV absorbers with a more suitable spectral absorption spectrum are particularly preferred. The benzotriazole-based UV absorbers may be bis(bis)-modified, such as 6,6'-methylenebis(2-(2H-benzo[d][1,2,3]triazol-2-yl)-4-(2,4,4-trimethylpentan-2-yl)phenol) or 6,6'-methylenebis(2-(2H-benzo[d][1,2,3]triazol-2-yl)-4-(2-hydroxyethyl)phenol).

[0073] In one embodiment, the polarizing plate 100 may further include other components in addition to the above-mentioned components to supplement or enhance the properties of the optical laminate. For example, the polarizing plate 100 may further include a phase difference control layer, a refractive index control layer, etc. to further improve the optical properties.

[0074] The retardation control layer (not shown) complements the optical properties of the optical laminate and may be implemented in the form of a retardation film, etc., and may be a conventional or later-developed retardation film, etc. For example, a quarter-wave plate (1 / 4 wave plate) or a half-wave plate (1 / 2 wave plate) for delaying the phase of light may be used, and these may be used alone or in combination.

[0075] The retardation control layer may be formed in direct contact with one surface of the polarizer in place of a protective film, but is not limited thereto. For example, the retardation control layer may be formed in direct contact with one surface of a protective layer or a refractive index control layer. The retardation control layer may be a polymer stretched film or a liquid crystal polymer film obtained by stretching a polymer film that can be given optical anisotropy by stretching in an appropriate manner.

[0076] In one embodiment, the polymer stretched film may be a polymer layer containing polyolefins such as polyethylene (PE) or polypropylene (PP), cycloolefin polymers (COP) such as polynorbornene, polyesters such as polyvinyl chloride (PVC), polyacrylonitrile (PAN), polysulfone (PSU), acrylic resins, polycarbonate (PC), or polyethylene terephthalate (PET), polyacrylate, cellulose ester polymers such as polyvinyl alcohol (PVA), or triacetyl cellulose (TAC), or a copolymer of two or more monomers among the monomers forming the polymers.

[0077] The method for obtaining the stretched polymer film is not particularly limited, and can be, for example, by molding the polymer material into a film and then stretching it. The film-forming method is not particularly limited, and can be formed into a film by known methods such as injection molding, sheet molding, blow molding, injection blow molding, inflation molding, extrusion molding, foam molding, and cast molding. Secondary processing methods such as compressed air molding and vacuum forming can also be used. Among these, extrusion molding and cast molding are preferred. In this case, for example, an unstretched film can be extruded using an extruder equipped with a T-die, a circular die, or the like. When obtaining a molded product by extrusion molding, a material in which various resin components, additives, etc. have been melt-kneaded in advance can be used, or the product can be formed through melt-kneading during extrusion molding. Alternatively, an unstretched film can be cast-molded by dissolving various resin components in a solvent common to the various resin components, such as chloroform or methylene dichloride, followed by casting, drying, and solidification.

[0078] The polymer stretched film may be produced by uniaxially stretching the formed film in the mechanical direction (MD; machine direction, lengthwise or longitudinal direction) or uniaxially stretching the formed film in the transverse direction (TD; widthwise or transverse direction) of the mechanical direction. Alternatively, a biaxially stretched film may be produced by stretching the formed film using a method such as sequential biaxial stretching with roll stretching and tenter stretching, simultaneous biaxial stretching with tenter stretching, or biaxial stretching with tubular stretching.

[0079] The liquid crystal polymer film may include a reactive liquid crystal compound in a polymerized state. The reactive liquid crystal compound may be the same as the reactive liquid crystal compound of the coating-type polarizer described above.

[0080] In one or more embodiments, the thickness of the retardation adjusting layer may be 10 to 100 μm in the case of a polymer stretched film, and 0.1 to 5 μm in the case of a liquid crystal polymer film.

[0081] The refractive index adjustment layer (not shown) is provided to compensate for the refractive index difference of the optical laminate due to the transparent conductive layer 200 described below, and may serve to improve visibility by reducing the refractive index difference. The refractive index adjustment layer may also be provided to correct the color caused by the transparent conductive layer 200. Meanwhile, when the transparent conductive layer has a pattern, the refractive index adjustment layer can compensate for the transmittance difference between a patterned region where the pattern is formed and a non-patterned region where the pattern is not formed.

[0082] Specifically, the transparent conductive layer 200 described below is stacked adjacent to another member (e.g., a polarizer) having a different refractive index, and the difference in refractive index between the adjacent layers may cause a difference in light transmittance. In particular, when a pattern is formed on the transparent conductive layer, the patterned region and the non-patterned region may be visually distinguishable. Therefore, by including the refractive index control layer in the polarizer, the refractive index is compensated for, thereby reducing the difference in light transmittance of the optical laminate. In particular, when a pattern is formed on the transparent conductive layer, the patterned region and the non-patterned region are visually distinguishable.

[0083] In one embodiment, the refractive index of the refractive index adjusting layer may be appropriately selected depending on the material of other adjacent components, and is preferably 1.4 to 2.6, and more preferably 1.4 to 2.4. In this case, light loss due to a sharp difference in refractive index between other components such as the polarizer and the transparent conductive layer 200 can be prevented.

[0084] The refractive index adjustment layer is not particularly limited as long as it can prevent a sharp difference in refractive index between the transparent conductive layer 200 and other components such as a polarizer, and may be formed from a compound used to form a conventional or later-developed refractive index adjustment layer, for example, a refractive index adjustment layer-forming composition containing a polymerizable isocyanurate compound.

[0085] In one embodiment, the thickness of the polarizer 100 may be 10 to 300 μm, and at least one of the first polarizer 100-1 and the second polarizer 100-2 preferably has a thickness of 30 to 200 μm. When the thickness of the polarizer satisfies this range, the process is easy, it is suitable for manufacturing a uniform laminate, and excellent optical properties can be exhibited.

[0086] The transparent conductive layer 200 is provided for driving the liquid crystal layer and may be formed in direct contact with the polarizer 100. For example, as shown in FIGS. 1 to 6, the first transparent conductive layer 200-1 and the second transparent conductive layer 200-2 may be formed in direct contact with the first polarizer 100-1 and the second polarizer 100-2, respectively. Conventional optical stacks used in manufacturing smart windows, etc., are manufactured by forming a conductive layer for driving liquid crystals on one side of a substrate and bonding the other side of the substrate to a polarizer. However, the variable transmittance optical stack according to the present invention does not include a separate substrate for forming the conductive layer, and instead forms a conductive layer directly on one side of the polarizer, thereby reducing the thickness of the stack and improving the transmittance and bending characteristics in the transmission mode. In one embodiment, the transparent conductive layer 200 may be formed by direct deposition on one side of the polarizer 100. In this case, the transparent conductive layer 200 may be formed by directly contacting the pretreated surface of the polarizer 100 after pretreatment such as corona treatment or plasma treatment is performed on one surface of the polarizer 100 to improve adhesion to the polarizer 100. The pretreatment is not limited to corona treatment or plasma treatment, and any conventional or later-developed pretreatment process may be used as long as it does not impair the objectives of the present invention. In another embodiment, the transparent conductive layer 200 may be formed by directly contacting the polarizer 100 with an easy-adhesion layer (not shown) sandwiched between the one surface of the polarizer 100 to improve adhesion to the polarizer 100. The transparent conductive layer 200 preferably has a visible light transmittance of 50% or more and may include, for example, one or more materials selected from the group consisting of transparent conductive oxides, metals, carbon-based materials, conductive polymers, conductive inks, and nanowires. However, the present invention is not limited thereto, and any conventional or later-developed transparent conductive material may be used. The conductive layer may also be formed as a two-layer or more layer structure using a combination of the above materials. For example, the conductive layer may have a two-layer structure of a metal layer and a transparent conductive oxide layer, thereby reducing the reflectance of incident light and increasing the transmittance.A metal layer has high reflectivity and can reduce the visibility of the screen when used alone. However, by laminating a transparent conductive oxide layer on the metal layer, the reflectivity can be reduced and the transmittance can be improved.

[0087] More specifically, in one embodiment, the transparent conductive oxide may include one or more selected from the group consisting of indium tin oxide (ITO), indium zinc oxide (IZO), indium zinc tin oxide (IZTO), aluminum zinc oxide (AZO), gallium zinc oxide (GZO), fluorine tin oxide (FTO), zinc oxide (ZnO), etc. The metal may include one or more selected from the group consisting of gold (Au), silver (Ag), copper (Cu), aluminum (Al), platinum (Pt), palladium (Pd), chromium (Cr), titanium (Ti), tungsten (W), niobium (Nb), tantalum (Ta), vanadium (V), iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), zinc (Zn), and alloys containing at least one of these metals, such as a silver-palladium-copper (APC) alloy or a copper-calcium (CuCa) alloy. The carbon-based material may include at least one selected from the group consisting of carbon nanotubes (CNTs) and graphene, and the conductive polymer may include at least one selected from the group consisting of polypyrrole, polythiophene, polyacetylene, PEDOT, polyaniline, etc. The conductive ink may be an ink containing a mixture of metal powder and a curable polymer binder, and the nanowire may be, for example, a silver nanowire (AgNW).

[0088] The transparent conductive layer 200 may also be formed as a two-layer structure using a combination of the above materials. For example, it may be formed as a two-layer structure including a metal layer and a transparent conductive oxide layer to reduce the reflectance of incident light and increase the transmittance. The transparent conductive layer 200 may be formed by a method commonly used in the art, such as coating processes such as spin coating, roller coating, bar coating, dip coating, gravure coating, curtain coating, die coating, spray coating, doctor coating, and kneader coating; printing (coating) processes such as screen printing, spray printing, inkjet printing, relief printing, intaglio printing, and planographic printing; deposition processes such as chemical vapor deposition (CVD), physical vapor deposition (PVD), and plasma-enhanced chemical vapor deposition (PECVD), and dry or wet plating processes.

[0089] In one embodiment, the thickness of the transparent conductive layer 200 may be 1 to 80 nm, preferably 5 to 70 nm, and more preferably 10 to 60 nm. The thickness of the transparent conductive layer is preferably within this range in order to improve the optical properties, including the chromaticity and transmittance, of the optical laminate when a low voltage of 20 V or less is applied, and to improve mechanical stability by fixing or maintaining the thickness within a predetermined range.

[0090] The alignment film 300 is provided on one surface of the first polarizer 100-1 and the second polarizer 100-2 and is a layer that aligns liquid crystal molecules to a specific position and direction. The alignment film 300 may be provided on the liquid crystal layer 500 side of the polarizer, i.e., on the inner side, and may be disposed facing each other. The alignment film 300 may be formed by coating an alignment liquid commonly used in the technical field to which the present invention belongs and then drying it. In one embodiment, the alignment film 300 may have a thickness of 30 to 300 nm. Specifically, the thickness of the alignment film into which the ball spacers are embedded may be 30 to 300 nm, and the first and second alignment films disposed opposite each other with respect to the liquid crystal layer may have the same thickness or may differ by a deviation range of ±30%. If the thickness of the alignment film is less than the above range, the alignment liquid will not be applied uniformly when coating during the manufacturing process of the alignment film, which may cause a current short circuit due to interference between the alignment film and the transparent conductive layer, resulting in unevenness or other damage to the liquid crystal after the optical laminate is cured.If the thickness exceeds the above range, liquid crystal defects or afterimages may be visible, and the response speed may be slowed.

[0091] 1 to 6, in one embodiment of the present invention, the transparent conductive layer 200 and the alignment film 300 may be sequentially stacked on a hard coating layer having ball spacers embedded therein to form a curved portion. The first alignment film 300-1 and the second alignment film 300-2 may abut against each other at the positions where the ball spacers are embedded to support the liquid crystal layer, and a separation space may be formed between the first alignment film 300-1 and the second alignment film 300-2 to form the liquid crystal layer 500. The thickness of the separation space does not exceed the thickness of the liquid crystal layer 500, which will be described later.

[0092] The liquid crystal layer 500 can change the driving mode of the optical laminate by controlling the transmittance of light incident from one or more directions using an electric field. The liquid crystal layer may include a liquid crystal compound in a transmittance control layer. For example, the liquid crystal layer may be located in the space defined by the sealant 600 and ball spacers 400 between the first polarizer 100-1 and the second polarizer 100-2 in the light control region. The liquid crystal compound is not particularly limited as long as it is driven by an electric field and can control the light transmittance. Any conventional or later-developed liquid crystal compound may be used. For example, the same applies to the reactive liquid crystal compound of the coating-type polarizer described above. The liquid crystal behavior mode of the liquid crystal layer is not particularly limited, and may be driven in a twisted nematic (TN) mode, a super twisted nematic (STN) mode, a vertical alignment (VA) mode, or the like. The driving method can be applied depending on the alignment of the polarization axes. For example, when the optical axes of the first polarizer 100-1 and the second polarizer 100-2 are aligned at 0°, the liquid crystal display is driven in a vertical alignment (VA) mode, and when they are aligned at 90°, the liquid crystal display is driven in a twisted nematic (TN) mode. In one embodiment, the liquid crystal layer 500 may have a thickness of 1 to 20 μm, preferably 3 to 10 μm, and more preferably 4 to 7 μm. If the liquid crystal layer thickness is less than this range, the transmittance may decrease, and if it exceeds this range, haze may occur even in the transmissive mode.

[0093] The sealant 600 may be positioned between the first polarizer 100-1 and the second polarizer 100-2 in the inactive region. The sealant may serve to bond the first polarizer and the second polarizer, and together with the spacer, may secure a space between the first polarizer and the second polarizer for providing a liquid crystal layer.

[0094] The sealant may include a curable resin as a base resin. The base resin may be a UV-curable resin or a thermosetting resin known in the art for use in sealants. The UV-curable resin may be a polymer of a UV-curable monomer. The thermosetting resin may be a polymer of a thermosetting monomer. The base resin of the sealant 600 may be, for example, an acrylate-based resin, an epoxy-based resin, a urethane-based resin, a phenol-based resin, or a mixture of these resins. In one embodiment, the base resin may be an acrylate-based resin, and the acrylate-based resin may be a polymer of an acrylic monomer. The acrylic monomer may be, for example, a multifunctional acrylate. In another embodiment, the sealant may further include a monomer component in the base resin. The monomer component may be, for example, a monofunctional acrylate. In this specification, a monofunctional acrylate may refer to a compound having one acrylic group, and a multifunctional acrylate may refer to a compound having two or more acrylic groups. The curable resin may be cured by ultraviolet irradiation and / or heating. The ultraviolet irradiation conditions or heating conditions may be appropriately set within a range that does not impair the objectives of the present application. The sealant may further include an initiator, such as a photoinitiator or a thermal initiator, if necessary. The sealant may be formed by a method commonly used in the art, for example, by drawing the sealant onto the outer edge (i.e., non-active area) of the liquid crystal layer using a dispenser equipped with a nozzle.

[0095] The variable transmittance optical laminate of the present invention may further include other components within the scope that does not impair the object of the present invention, for example, it may further include an adhesive layer 700 (see Figures 3 to 6), or it may further include an ultraviolet absorbing layer (not shown) and an impact resistant layer (not shown).

[0096] The adhesive layer 700 may be formed using an adhesive or pressure-sensitive adhesive, and preferably has an appropriate adhesive strength to prevent peeling, bubbles, etc. from occurring when handling the optical laminate, as well as transparency and thermal stability, and may have viscoelastic properties applicable to smart windows.

[0097] The adhesive may be a conventional or later-developed adhesive, for example, a photocurable adhesive. The photocurable adhesive exhibits strong adhesive strength by crosslinking and curing upon exposure to active energy rays such as ultraviolet (UV) or electron beams (EB). It may be composed of a reactive oligomer, a reactive monomer, a photopolymerization initiator, and the like. The reactive oligomer is an important component that determines the adhesive's properties and forms a hardened coating by forming polymer bonds through a photopolymerization reaction. Usable reactive oligomers include polyester-based resins, polyether-based resins, polyurethane-based resins, epoxy-based resins, polyacrylic resins, and silicone-based resins. The reactive monomer functions as a crosslinker or diluent for the reactive oligomer and affects the adhesive properties. Usable reactive monomers include monofunctional monomers, polyfunctional monomers, epoxy-based monomers, vinyl ethers, and cyclic ethers. The photopolymerization initiator absorbs light energy to generate radicals or cations, thereby initiating photopolymerization. An appropriate photopolymerization initiator may be selected depending on the photopolymerizable resin. The pressure-sensitive adhesive may be a conventional or later-developed pressure-sensitive adhesive. In one or more embodiments, an acrylic pressure-sensitive adhesive, a rubber pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a polyvinyl alcohol pressure-sensitive adhesive, a polyvinylpyrrolidone pressure-sensitive adhesive, a polyacrylamide pressure-sensitive adhesive, a cellulose pressure-sensitive adhesive, a vinyl alkyl ether pressure-sensitive adhesive, or the like may be used. The pressure-sensitive adhesive is not particularly limited as long as it has adhesive strength and viscoelasticity. However, from the viewpoint of availability, an acrylic pressure-sensitive adhesive may be used, and may contain, for example, a (meth)acrylate copolymer, a crosslinking agent, and a solvent. The crosslinking agent may be a conventional or later-developed crosslinking agent, and may contain, for example, a polyisocyanate compound, an epoxy resin, a melamine resin, a urea resin, a dialdehyde, a methylol polymer, or the like, and preferably contains a polyisocyanate compound.The solvent may include conventional solvents used in the field of resin compositions, such as alcohol-based compounds such as methanol, ethanol, isopropanol, butanol, and propylene glycol methoxyalcohol; ketone-based compounds such as methyl ethyl ketone, methyl butyl ketone, methyl isobutyl ketone, diethyl ketone, and dipropyl ketone; acetate-based compounds such as methyl acetate, ethyl acetate, butyl acetate, and propylene glycol methoxyacetate; cellosolve-based compounds such as methyl cellosolve, ethyl cellosolve, and propyl cellosolve; and hydrocarbon-based compounds such as hexane, heptane, benzene, toluene, and xylene. These may be used alone or in combination of two or more.

[0098] For example, adhesive layer materials such as PVB (polyvinyl butyral) and EVA (ethylene vinyl acetate) may be suitable for use in the manufacture of smart windows for vehicles, and adhesive layers may be suitable for smart windows for architectural fixtures, but are not limited to these.

[0099] The thickness of the adhesive layer 700 can be determined appropriately depending on the type of resin acting as the adhesive, its adhesive strength, the environment in which the adhesive is used, etc. In one embodiment, the adhesive layer may have a thickness of 0.1 to 500 μm, preferably 0.5 to 450 μm, and more preferably 1 to 400 μm, in the case of an adhesive layer, in order to ensure sufficient adhesive strength and minimize the thickness of the optical laminate. In one embodiment, the adhesive layer 700 may have a thickness of 2 to 30 μm, preferably 3 to 20 μm, and more preferably 5 to 10 μm, in the case of an adhesive layer. In one embodiment, the adhesive layer 700 may be formed on one or both surfaces of the polarizing plate by lamination or vacuum bonding.

[0100] The ultraviolet absorbing layer (not shown) is not particularly limited as long as it is used to prevent deterioration of the optical laminate due to ultraviolet rays, and the same description of the ultraviolet absorber as described for the protective layer can be applied as is, so the description will be omitted.

[0101] The impact-resistant layer (not shown) is positioned inward and is not particularly limited as long as it functions to absorb impact and prevent damage to the internal substrate when an impact is applied to the entire surface of the window. Preferably, the impact-resistant layer is made of a material with a high tolerance for deformation energy, such as a thermoplastic resin with high toughness. Examples of such resins include polycarbonate resins, polyimide resins, polyamide resins, polyamideimide resins, and polyester resins. Furthermore, since the present invention is intended for use in display devices, it is preferable to use a resin with excellent light transmittance, preferably optically transparent.

[0102] The present invention includes the method for manufacturing the variable transmittance optical laminate described above. The method for manufacturing the variable transmittance optical laminate is not particularly limited, and the variable transmittance optical laminate can be manufactured using any bonding technique or the above-mentioned photolithography technique.

[0103] 4 to 6, the present invention includes a smart window including the variable transmittance optical laminate, an automobile in which the smart window is applied to at least one of a front window, a rear window, a side window, a sunroof window, and an interior partition, and a building fixture including the smart window. For example, a vehicle including the smart window of the present invention may have vehicle glass 800 bonded to both sides of a variable transmittance optical laminate including a polarizer 100 including a polarizer 110 and a hard coating layer 120, a transparent conductive layer 200, a liquid crystal layer 500, and an adhesive layer 700 (see FIG. 4). Any optical adhesive material known in the art for use as an adhesive material can be used for bonding the glass. For example, the optical adhesive may be one or more selected from PVB (Polyvinyl Butyral), EVA (Ethylene Vinyl Acetate), OCR (Optically Clear Resin) and / or OCA (Optically Clear Adhesive). Specifically, the optical adhesive has a storage modulus (G') of 1×10 at 25° C. for PVB. 5 〜1×10 7 Pa, and EVA is 1 x 10 4 〜1×10 5 Pa, and OCR and OCA are 1 × 10 3 〜1×10 6 Selecting Pa is preferable in that it not only provides excellent adhesion durability against changes in temperature and humidity in outdoor environmental conditions after bonding, increases sufficient adhesive strength and impact resistance of the glass window to enhance safety, but also provides sound insulation performance that compensates for the low transmission loss in some high frequency bands due to the waveform matching phenomenon of glass.

[0104] For example, the films may be manufactured by placing adhesive films such as EVA film or PVB film and vehicle glass on both sides of the optical laminate, and then heating them at 90°C and about 1 bar or higher in vacuum using a press for 10 to 20 minutes, or by coating one side of the vehicle glass with a resin such as OCR (Optically Clear Resin), vacuum-bonding the vehicle glass to both sides of the optical laminate, and then UV-curing the glass. Also, architectural fittings (glass for fittings) 900 may be bonded to both sides (see FIG. 5) or one side (see FIG. 6) of the variable transmittance optical laminate. A smart window product for architectural fittings having the same configuration as shown in FIG. 5 or 6 may be manufactured by applying a UV adhesive to glass for fittings on both sides of the variable transmittance optical laminate, bonding the glass for fittings, and then UV-curing the glass. Alternatively, a smart window product for fittings having the same configuration as shown in FIG. 5 or 6 may be manufactured by bonding glass for fittings to one side of the variable transmittance optical laminate by lamination.

[0105] In addition, the smart window may be applied to means of transportation and wearable devices commonly used in the field. [Example]

[0106] [Example] Examples of the present invention will be described in detail below. However, the present invention is not limited to the examples disclosed below and can be embodied in various different forms. However, these examples are provided to fully disclose the present invention and to fully convey the scope of the invention to those skilled in the art to which the present invention pertains, and the present invention is defined only by the scope of the claims. In the examples, "%" and "parts" refer to % by weight and parts by weight, respectively, unless otherwise specified.

[0107] 7 is a process diagram showing a manufacturing process of a variable transmittance optical laminate according to an embodiment of the present invention. Optical laminates of the example and comparative example were manufactured according to the process shown in FIG. 7 and the following details.

[0108] Production example 1: Polarizing plate production (S1) (1) Swelling treatment process A 60 μm thick polyvinyl alcohol film (raw film) (manufactured by Kuraray Co., Ltd., product name "Kuraray Poval Film VF-PE#6000", average polymerization degree 2400, saponification degree 99.9 mol%) was continuously unwound from a raw roll and transported, and immersed in a swelling bath containing pure water at 20°C for 30 seconds. In this swelling treatment process, inter-roll stretching (longitudinal uniaxial stretching) was performed with a difference in peripheral speed between the nip rolls. The stretching ratio based on the raw film was 2.5 times.

[0109] (2) Dyeing process Next, the film passed through the nip rolls was immersed in a dye bath containing pure water / potassium iodide / iodine / boric acid (mass ratio) of 100 / 2 / 0.01 / 0.3 at 30°C for 120 seconds. During this dyeing process, roll-to-roll stretching (longitudinal uniaxial stretching) was performed with a difference in peripheral speed between the nip rolls. The stretching ratio was 1.1 times, based on the film after the swelling treatment step.

[0110] (3) Crosslinking process Next, the film passed through the nip rolls and was immersed for 70 seconds in a first crosslinking bath at 56°C, containing pure water, potassium iodide, and boric acid (mass ratio: 100 / 12 / 4). Roll-to-roll stretching (longitudinal uniaxial stretching) was performed by setting a difference in peripheral speed between the nip rolls and a nip roll prepared between the first and second crosslinking baths. The stretching ratio was 1.9 times, based on the film after the dyeing treatment process.

[0111] (4) Complementary color processing process Next, the film after the crosslinking treatment was immersed for 10 seconds in a second crosslinking bath at 40° C. containing potassium iodide / boric acid / pure water (mass ratio) of 9 / 2.9 / 100.

[0112] (5) Cleaning process Next, the film after the second crosslinking treatment was immersed in a washing bath containing pure water at 14°C for 5 seconds, and the shower volume was 5 m 3 Washing was performed at 14°C / h and shower temperature.

[0113] At this time, the short wavelength region is absorbed [PVA + I3 - ]The complex is weak against water, and the b* value of the single transmittance hue varies greatly depending on the temperature of the cleaning solution, the residence time of the cleaning solution, the amount of shower, the temperature of the shower, and the water content of the PVA.

[0114] (6) Drying process The washed film was then passed through a drying oven and heated and dried at 80°C for 190 seconds to produce a polarizer film. The moisture content after drying was 13.6%, and the thickness of the resulting polarizer film was approximately 21µm.

[0115] (7) Bonding process Next, a water-based adhesive containing 5 parts by weight of polyvinyl alcohol per 100 parts by weight of water was prepared as the adhesive. Then, protective films were laminated on both sides of the polarizer film using the prepared UV adhesive. The resulting laminate was exposed to UV light to cure the adhesive, producing a first polarizing plate and a second polarizing plate. The thickness of the adhesive layer in the resulting polarizing plate was approximately 2 μm.

[0116] Preparation Example 2: Preparation of hard coating composition (S2) A hard coating composition was prepared by mixing 16.2 g of a dendrimer compound (MIWON Specialty Chemicals, SP-1106), 14.4 g of inorganic nanoparticles (Nissan Chemical, MEK-AC-2140, solid content 40 wt%), 1.8 g of a multifunctional (meth)acrylate containing an ethylene glycol group (Nippon Kayaku, DPEA126), 0.7 g of a photoinitiator, 1-hydroxycyclohexyl phenyl ketone (TCI), and 2.9 g of a solvent, methyl ethyl ketone (DAELIM Corporation).

[0117] Preparation Example 3: Preparation of first hard coating layer (S2-1) The hard coating composition prepared in Preparation Example 2 and ball spacers (SP series from SEKISUI Co., Ltd.) were mixed and the mixture was slot-die coated onto one surface of the first polarizing plate, adjusting the substrate moving speed (m / min) and the mixture flow rate (ml / sec) to obtain a thickness after drying. The coating was then dried at 80°C for 5 minutes and then irradiated with 500mJ / cm 2 of a high-pressure mercury lamp. 3 The first hard coating layer was formed by curing with a light dose of 10 ...

[0118] Preparation Example 4: Preparation of second hard coating layer (S2-2) The hard coating composition prepared in Preparation Example 2 was slot-die coated onto one surface of the second polarizing plate, adjusting the substrate moving speed (m / min) and composition flow rate (ml / sec) to obtain a thickness after drying. After drying at 80°C for 5 minutes, the coating was applied with a high-pressure mercury lamp at 500 mJ / cm. 3 The second hard coating layer was formed by curing with a light dose of 10 ...

[0119] Production Example 5: Production of first transparent conductive layer (S3-1) The first polarizer with the first hard coating layer prepared according to Preparation Example 3 was placed in the substrate, and a sputtering gun was operated at 450 W DC power. Plasma was then induced on an ITO (10 wt% SnO2) target to form a first transparent conductive layer (90 nm). The formed transparent conductive layer was then ion-treated using an ion gun at 50 W DC power. The pressure was maintained at 3 mTorr at room temperature, and argon gas and oxygen gas were supplied at 30 sccm and 1 sccm, respectively. The thickness of the transparent conductive layer was measured using a FT-SEM.

[0120] Manufacturing Example 6: Manufacturing of first alignment film (S4-1, S5-1) A TN alignment solution (RN-4662, Nissan Chemical Industries) was coated on the first transparent conductive layer prepared in Preparation Example 5, and the thickness after drying was adjusted using a Mayer bar, followed by drying (80°C / 2 minutes). Then, UV light was irradiated onto the dried alignment solution to form a first alignment film, thereby producing a first laminate.

[0121] Production Example 7: Production of second transparent conductive layer (S3-2) The second polarizer with the second hard coating layer prepared according to Preparation Example 4 was placed in the substrate, and a sputtering gun was operated at 450 W DC power. Plasma was then induced on an ITO (10 wt% SnO2) target to form a second transparent conductive layer (90 nm). The formed second transparent conductive layer was then ion-treated using an ion gun at 50 W DC power. The pressure was maintained at 3 mTorr at room temperature, and argon gas and oxygen gas were supplied at 30 sccm and 1 sccm, respectively. The thickness of the transparent conductive layer was measured using a FT-SEM.

[0122] Manufacturing Example 8: Manufacturing of second alignment film (S4-2, S5-2) A TN alignment solution (RN-4662, Nissan Chemical Industries) was coated on the second transparent conductive layer prepared in Preparation Example 7, and the thickness after drying was adjusted using a Mayer bar, followed by drying (80°C / 2 minutes). Then, UV light was irradiated onto the dried alignment solution to form a second alignment film, thereby producing a second laminate.

[0123] Production Example 9: Production of optical laminating agent (S6) Using a sealant dispenser (SHOTmini 200Ωx, MUSASHI), a sealant (UVF-006, 70,000 mPa·s, SEKISUI) was applied to the first transparent conductive layer manufactured according to Manufacturing Example 5 using a sharp needle (SPN-0.25-12.7L) at a discharge pressure of 200 mPa according to the product size drawing, and liquid crystal was injected onto the first alignment layer using the ODF process. Then, with the horizontal optical axes of the first polarizer and the second polarizer parallel to each other at 0° or 90°, the first laminate manufactured according to Manufacturing Example 6 and the second laminate manufactured according to Manufacturing Example 8 were applied at 3 kg / cm. 2 After pressure bonding, UV curing (500 mJ / cm) was performed along the sealant line. 2 ) was carried out to produce an optical laminate for smart windows. Then, conductive copper tape (TERAOKA, No. 8323) was adhered to the first transparent conductive layer and the second transparent conductive layer to connect them.

[0124] Comparative manufacturing example 1: Spacer scattering The mixed solvent was prepared by mixing 100 ml of IPA with a ball spacer (SP series, SEKISUI Corporation). The second laminate prepared in Preparation Example 8 was placed in a spacer sprayer (SDSS-KHU02, SHINDO ENG LAB), and the prepared mixed solvent was sprayed at 110°C and dried for 20 minutes.

[0125] Examples 1 to 7 and Comparative Examples 1 to 3: Production of optical laminates Optical laminates of Examples and Comparative Examples were fabricated according to Preparation Examples 1 to 9, except that the diameter A of the ball spacer, the thickness B of the first hard coating layer, and the thickness of the first alignment layer in which the ball spacer is embedded were set as shown in Table 1 below.

[0126] [Table 1]

[0127] Experimental example (1) Evaluation of ball spacer adhesion strength The first hard coating layer sample substrate with ball spacers embedded therein was prepared by carrying out the process of Example 1 up to Preparation Example 3, and the hard coating layer sample substrate of Comparative Preparation Example 1 in which ball spacers were separately sprayed without being embedded in the hard coating layer was prepared. An air gun (nozzle diameter: 2 mm) was positioned on the ball spacers at a distance of 30 mm from the center of the sample substrate, tilted at 45°, and 4 kg / cm was sprayed. 2 When air was discharged under pressure, the initial number of ball spacers and the number of ball spacers remaining on the hard coating layer after the air was discharged were counted using an optical microscope. 2 The number of ball spacers present within the space was counted, and the results are shown in Table 2 below, based on the initial number of 100.

[0128] [Table 2]

[0129] (2) Evaluation of optical properties The spectral characteristics of the optical laminates of Examples 1 to 7 and Comparative Examples 1 to 3 were evaluated using a spectrophotometer (CM-3700d, Konica Minolta). The upper polarizing plate was positioned in the direction of the light source, and the transmittance (%), parallel values, and perpendicular values ​​for the single transmission hue b* value were measured in the voltage application mode of voltage ON and voltage OFF at the center of the sample, and the average values ​​were calculated and shown in Table 1.

[0130] (3) Reliability-driven evaluation After connecting electrodes to the copper tape of the optical laminate sample in a room temperature environment, the sample was repeatedly subjected to voltage ON (10V AC voltage) and voltage OFF mode, and the reliability of the drive was evaluated by determining whether it was good or bad according to the following evaluation criteria, and the results are shown in Table 1. The criteria for good or bad were evaluated according to Table 3 below.

[0131] <Evaluation criteria> ○: Good after 100,000 or more cycles △: Defects occurred when repeated 20,000 to 100,000 times X: Defects occur when repeated less than 20,000 times

[0132] [Table 3]

[0133] When the voltage is on, the criteria for the liquid crystal hue to be black from the front means that the transmittance is 0.5% or less and the single transmission hue b* is within the range of -3 to 3, and when the voltage is off, the criteria for the liquid crystal hue to be transparent from the front means that the transmittance is 20% or more. In addition, when observing the appearance, if one or more changes are observed, such as black amorphous unevenness (see Figure 8), liquid crystal unevenness (see Figure 9), light leakage (see Figure 10), black spots, or white spots, it is marked as "changed." If any one of the criteria for the change in liquid crystal hue and appearance with or without voltage application is not met, it is judged as "failed."

[0134] Referring to the experimental data in Table 2, in Preparation Example 3, in which ball spacers were mixed into the hard coating layer composition and then dried and cured, it was observed that the ball spacers hardly fell off even under external impact and were firmly attached to the hard coating layer, compared to Comparative Preparation Example 1, in which the ball spacers were separately sprayed on the hard coating layer.

[0135] Furthermore, referring to the experimental data in Table 1, in Examples 1 to 4 in which the variable transmittance optical laminate of the present invention was applied, the diameter A of the ball spacer was 3 to 14 μm, the thickness B of the hard coating layer embedding the ball spacer was 1 to 10 μm, and the value of AB was 2 to 10 μm, and it was evaluated that the liquid crystal color and appearance were excellent regardless of the voltage application state.

[0136] In contrast, in Comparative Examples 1 to 3, where one or more of the ball spacer diameter A and the thickness B and AB of the hard coating layer in which the ball spacer is embedded were not satisfied, evaluation of driving reliability revealed that when the liquid crystal cell gap AB was 1 μm or less, the transparent conductive layers at particularly narrow positions were easily in contact with each other due to the uneven distance between the transparent conductive layers, resulting in current shorts and visible black amorphous irregularities (see FIG. 8). When the liquid crystal cell gap exceeded 10 μm, light leakage was observed due to viewing angle characteristics. Furthermore, when the hard coating thickness exceeded 10 μm, the surface irregularities caused by the deviation in hard coating thickness affected the liquid crystal gap, preventing a uniform liquid crystal thickness and resulting in visible liquid crystal irregularities (see FIG. 9). In such cases, the appearance was poor, light leakage occurred, and the visibility and reliability of the optical laminate could be reduced.

[0137] For reference, Examples 6 and 7 satisfied the above-mentioned conditions for the diameter A of the ball spacer and the thicknesses B and AB of the hard coating layer that embeds the ball spacer, but the thickness of the first alignment film was outside the range of 30 to 300 nm, and it was observed that one or more criteria in the evaluation of reliability of driving were poor. In the case of Example 6, when the first alignment film thickness was less than 30 nm, short circuits occurred between the transparent conductive layers, and black amorphous unevenness was visible (see Figure 8). In the case of Example 7, when the first alignment film thickness exceeded 300 nm, the front black color of the liquid crystal was not achieved, and poor liquid crystal unevenness (see Figure 9) and afterimages were visible during driving.

[0138] Therefore, the variable transmittance optical laminate according to the present invention has excellent liquid crystal cell gap maintaining properties as the ball spacers are fixed to the hard coating layer, and by satisfying the conditions that the diameter A of the ball spacers is 3 to 14 μm, the thickness B of the hard coating layer in which the ball spacers are embedded is 1 to 10 μm, and the value of AB is 2 to 10 μm, it is possible to ensure a uniform liquid crystal layer and it can be confirmed that the optical performance is excellent. [Industrial Applicability]

[0139] According to the variable transmittance optical laminate of the present invention, the ball spacers are fixed in a recessed form in the hard coating layer, minimizing the movement of the ball spacers, thereby preventing damage to the laminate. In particular, by preventing damage to the alignment layer due to the movement of the ball spacers, light leakage between the liquid crystal layer and other laminates can be prevented. [Explanation of symbols]

[0140] 100: Polarizing plate 110: Polarizer 120: Hard coating layer 200: Transparent conductive layer 300: Alignment film 400: Ball spacer 500: Liquid crystal layer 600: Sealant 700:Adhesive layer 800: Smart window glass for vehicles 900: Architectural fittings smart window glass

Claims

1. a first laminate in which a first polarizer including a first hard coating layer, a first transparent conductive layer, and a first alignment film are sequentially laminated; a second laminate in which a second polarizer including a second hard coating layer, a second transparent conductive layer, and a second alignment film are sequentially laminated; and a liquid crystal layer disposed between the first alignment film and the second alignment film; At least one of the first and second transparent conductive layers is formed in direct contact with one of the first and second polarizers, ball spacers recessed into at least one of the first hard coating layer and the second hard coating layer to maintain a gap between layers above and below the liquid crystal layer; A variable transmittance optical stack, wherein a diameter A of the ball spacer is 3 to 14 μm, a thickness B of the hard coating layer of the first hard coating layer and the second hard coating layer that envelops the ball spacer is 1 to 10 μm, and a value of A−B is 2 to 10 μm.

2. 2. The variable transmittance optical laminate according to claim 1, wherein the thickness of the first alignment film and the second alignment film is independently 30 to 300 nm.

3. 2. The variable transmittance optical laminate according to claim 1, wherein the first polarizer and the second polarizer are driven in a VA (Vertical Alignment) mode when their respective optical axes are aligned at 0°, and in a TN (Twisted Nematic) mode when their respective optical axes are aligned at 90°.

4. 10. The variable transmittance optical stack of claim 1, wherein the average recession depth of the ball spacers into the hard coating layer exceeds 50% of the hard coating layer thickness.

5. 2. The variable transmittance optical laminate of claim 1, wherein at least one of the first transparent conductive layer and the second transparent conductive layer includes an easy-adhesion layer between the first polarizer and the second polarizer and is formed in direct contact with the first polarizer and the second polarizer.

6. 2. The variable transmittance optical laminate according to claim 1, wherein at least one of the first polarizing plate and the second polarizing plate comprises at least one selected from the group consisting of a protective layer, a retardation control layer, and a refractive index control layer.

7. The variable transmittance optical laminate of claim 1 , wherein at least one of the first polarizer and the second polarizer has a thickness of 30 to 200 μm.

8. 2. The variable transmittance optical laminate according to claim 1, wherein the area occupied by the ball spacers in the liquid crystal layer is 0.01 to 10% of the area of ​​the liquid crystal layer.

9. The variable transmittance optical laminate according to claim 1 , further comprising at least one layer selected from the group consisting of an adhesive layer, an ultraviolet absorbing layer, and an impact resistant layer.

10. A method for producing the variable transmittance optical laminate according to any one of claims 1 to 9.

11. A smart window comprising the variable transmittance optical stack according to any one of claims 1 to 9.

12. The smart window of claim 11 , wherein the smart window has glass bonded to one or both sides of the variable transmittance optical stack.

13. A means of transportation comprising the smart window of claim 11.

14. 12. A car in which the smart window according to claim 11 is applied to at least one of a front window, a rear window, a side window, a sunroof window, and an interior partition.

15. A wearable device comprising the smart window of claim 11.

16. Architectural fittings comprising the smart window of claim 11.

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