KR20220140148A - Reverse-operating smart window film, manufacturing method thereof and smart window including the same - Google Patents

Abstract

The present invention relates to a reverse-operating smart window film, a manufacturing method thereof and a smart window including the same, and more specifically, to a reverse-operating smart window film which is transparent when voltage is not applied, increases opacity as voltage is applied, has low emission characteristics, can be easily applied to windows and doors even with a thin thickness, and can achieve high haze, a manufacturing method thereof and a smart window including the same.

Description

Reverse-operating smart window film, manufacturing method thereof, and smart window including the same

The present invention relates to a reverse driving smart window film, a method for manufacturing the same, and a smart window including the same. Specifically, it is transparent when no voltage is applied, and the opacity increases as a voltage is applied, and has low radiation characteristics, The present invention relates to a reverse driving smart window film capable of being easily applied to windows and achieving excellent opacity even with a thin thickness, a manufacturing method therefor, and a smart window including the same.

Recently, as interest in resource depletion problem and quality of life increases, energy saving effect, eco-friendliness, and convenience are important topics. Attention is being paid to smart window technology that simultaneously satisfies such requirements.

In general, smart windows are formed so as to be turned on and off, and refer to windows in which the amount of light or heat passing through is controlled by changing the transmittance of light when a voltage is applied. That is, the smart window is provided to be changed to a transparent, opaque or translucent state by a voltage, and is also referred to as variable transmittance glass, dimming glass, or smart glass.

In addition, the smart window can be used as a partition of an indoor space or can be used as a skylight placed in an opening of a building, and can be used as a highway sign, bulletin board, scoreboard, clock or advertisement screen, It can also be used as windows or sunroofs of ships or trains.

A typical example of such a smart window is a polymer dispersed liquid crystal (Polymer Dispersed Liquid Crystal) based smart window.

A polymer dispersed liquid crystal (PDLC)-based smart window is a form in which liquid crystal droplets are dispersed in a polymer binder. In the off state, light is scattered due to the difference in refractive index between the polymer and dispersed liquid crystal. In case (On state), the refractive index of the dispersed liquid crystal changes and the refractive index of the two materials match, meaning a transparent smart window.

On the other hand, in the application of smart window technology, in recent years, as interest in the environment and energy increases, the demand for energy-saving industrial products increases, and as one of them, heat shielding of shielding members such as glass of houses, buildings, automobiles, etc., That is, there is a demand for a glass or film that is effective in reducing the thermal load from sunlight. In general, in the case of buildings, the cause of more than 35% of the energy loss in the building is the window performance of the building.

In addition, the smart window can function as a privacy protection in that it is a glass that can adjust the transmittance. Since it is glass, there is a problem in that power efficiency is rather deteriorated because power must be always supplied in order to use it as a transparent window. Accordingly, there is a demand for smart windows that are driven in the reverse direction so that power can be supplied for privacy protection only when necessary for use on windows or internal glass walls.

Therefore, it is urgent to develop a smart window film that can reduce cooling and/or heating costs due to low solar heat gain and emissivity, and also improve power efficiency.

Registered Patent Publication No. 10-2154513 (2020.09.10.)

The present invention has been devised to solve the above-described problems, and the problem to be solved is that the change in transmittance depending on whether a voltage is applied or not occurs in the reverse direction, so power for use as a high transmittance glass is unnecessary and excellent even with a thin thickness It is possible to achieve the opacity and to provide a film for a reverse driving smart window having excellent durability, a smart window including the same, and a method of manufacturing the film.

In order to solve the above problems, the present invention is a low-emission (low-E) film portion comprising a first metal oxide layer, a reflective metal layer and a second metal oxide layer sequentially; and

a first electrode layer in contact with one surface of the low-emission film part and sequentially; a liquid crystal unit including a liquid crystal having negative dielectric anisotropy; and a liquid crystal film part comprising a; and a second electrode layer;

It provides a reverse driving smart window film that satisfies the following conditional expression 1).

1) T _on < T _off

In the above condition 1), T _on represents the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when an 80V voltage is applied between the first electrode layer and the second electrode layer, and T _off is It shows the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when no voltage is applied.

In a preferred embodiment of the present invention, the liquid crystal unit may sequentially include a first alignment layer, a liquid crystal layer, and a second alignment layer.

Here, the first alignment layer and the second alignment layer may include a polyimide-based polymer and each independently have a thickness of 100 to 300 nm.

In a preferred embodiment of the present invention, the reverse driving smart window film may further satisfy the following conditional expressions 2) and 3).

2) 6 ≤ T _off /T _on ≤ 30

3) 3% ≤ T _on ≤ 15%

In the above Conditional Expressions 2) and 3), T _off represents the light transmittance (%) of the reverse driving smart window film when no voltage is applied, and T _on is 80V between the first electrode and the second electrode. Shows the light transmittance (%) of the reverse driving smart window film when a voltage is applied.

In a preferred embodiment of the present invention, the liquid crystal layer includes a cured product of liquid crystal ink including liquid crystal and a polymer resin,

The liquid crystal may have a dielectric anisotropy (Δε) of -6.0 to -1.0 and a refractive index anisotropy (Δn) of 0.07 to 0.15.

In a preferred embodiment of the present invention,

The liquid crystal is a bicyclohexyl-based compound, a cyclohexylphenyl-based compound, a cyclohexene-based, cyclohexylcarboxylic acid ester-based, difluorine-phenylene (difluorine)-based compound ( phenylene), including at least one selected from a bicyclo hydrocarbon compound and a tricyclo hydrocarbon compound,

The polymer resin may include at least one oligomer selected from an aromatic urethane acrylate oligomer, an aliphatic urethane acrylate oligomer, and a polyester acrylate oligomer; and at least one monomer selected from an acrylate-based monomer, an epoxy-based monomer, and a siloxane-based monomer; As formed by polymerization of one or more of, the viscosity may be 800 to 1500 cPs.

In a preferred embodiment of the present invention, the liquid crystal ink may include the liquid crystal and the polymer resin in a weight ratio of 30:70 to 55:45.

In a preferred embodiment of the present invention, the first electrode layer and the second electrode layer each independently include at least one selected from indium tin oxide (ITO) and a conductive polymer, and each independently have a sheet resistance of 30 It may be ~200Ω/□.

In a preferred embodiment of the present invention, the reflective metal layer includes a silver-palladium-copper alloy (Ag-Pd-Cu alloy, APC), and the first metal oxide layer and the second metal oxide layer are each independent As a zinc oxide (ZnO) 25 to 45% by weight and tin oxide (SnO ₂ ) It may include a zinc tin oxide (Zinc Tin Oxide, ZTO) containing 55 to 75% by weight.

In a preferred embodiment of the present invention, the low-emission film unit further comprises a transparent protective layer and a low-emission film base layer, and the liquid crystal film unit further comprises a liquid crystal film base layer, each layer comprising a liquid crystal film base layer, The first electrode layer, the liquid crystal part, the second electrode layer, the low-emission film base layer, the first metal oxide layer, the reflective metal layer, may be provided in the order of the second metal oxide layer.

In a preferred embodiment of the present invention, the reverse driving smart window film may have a total thickness of 50 to 200 μm, and a thickness ratio between the low-emissivity film part and the liquid crystal film part may be 1:1 to 2.5.

In a preferred embodiment of the present invention, the adhesive force of the liquid crystal layer to the alignment layer measured according to the following measuring method may be 10 to 100 gf/inch.

[How to measure]

The first alignment layer and the second alignment layer of the reverse driving smart window film are peeled off by 180° at a rate of 10 mm/min, and the adhesive force of the liquid crystal layer to the alignment layer is measured.

The present invention also provides a first film portion in which a first electrode layer and a first alignment film are sequentially formed on one surface of the liquid crystal film base layer; and a first step of preparing a second film part in which a second electrode layer and a second alignment film are sequentially formed on one surface of the low-emission film base layer; and

The first alignment layer of the first film portion and the second alignment layer of the second film portion are opposed to each other, and a liquid crystal ink including liquid crystal having negative dielectric anisotropy is introduced between the first alignment layer and the second alignment layer, and then laminated and cured to A second step of obtaining a smart window film by forming a liquid crystal layer between the first alignment layer and the second alignment layer;

The smart window film provides a method for manufacturing a reverse driving smart window film, characterized in that it satisfies the following conditional expression 1).

1) T _on < T _off

In the above condition 1), T _on represents the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when an 80V voltage is applied between the first electrode layer and the second electrode layer, and T _off is It shows the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when no voltage is applied.

In a preferred embodiment of the present invention, the second film part sequentially forms a first metal oxide layer, a reflective metal layer and a second metal oxide layer on one surface of the low-emission film base layer, and the low-emission film base material It may be manufactured by sequentially forming the second electrode layer and the second alignment layer on the other surface of the layer.

In a preferred embodiment of the present invention, curing in the second step may be UV curing.

In a preferred embodiment of the present invention, in the second step, curing may be performed by irradiating ultraviolet rays with an intensity of 1 to 10 mW/cm ² for 1000 to 5000 seconds.

The present invention also provides a window; And the reverse driving smart window film provided on at least one side of the window; provides a reverse driving smart window comprising a.

Unlike the conventional smart window, the present invention can make it opaque by applying a voltage, so that it is driven in the reverse direction, and excellent opacity can be achieved even with a thin thickness, while at the same time, the adhesion between each layer of the smart window film is excellent, and the process is also It is simple and has excellent productivity, and has excellent efficiency in reducing cooling and heating costs due to low solar heat acquisition and emissivity.

1A schematically illustrates the principle of light transmission or non-transmission when voltage is applied to and when no voltage is applied to a PDLC liquid crystal film.
FIG. 1b is a photograph of a state when voltage is applied to a smart window to which a PDLC liquid crystal film is applied and when no voltage is applied, respectively.
Figure 2a schematically shows the principle that light transmission or non-transmission occurs when voltage is applied and not applied to a smart window film including a PNLC liquid crystal film according to a preferred embodiment of the present invention.
2B is a picture taken when voltage is applied or not applied to the smart window to which the smart window film is attached according to an exemplary embodiment of the present invention.
3 is a view schematically showing the layered structure of the reverse driving smart window film according to a preferred embodiment of the present invention.
4 is a view schematically illustrating a method of performing a coating process of an alignment layer during a manufacturing process of a reverse-driven smart window film according to a preferred embodiment of the present invention.
5 is a view schematically showing a method of performing a lamination and curing process during the manufacturing process of the reverse driving smart window according to a preferred embodiment of the present invention.

Hereinafter, the configuration and effects of the present invention will be described in more detail with reference to the accompanying drawings.

The smart window film including PDLC liquid crystal, which has been conventionally used as a smart window film, is a polymer dispersed liquid crystal (PDLC)-based smart window film, in which liquid crystal is dispersed in a polymer binder, and is semi-permeable (haze is present) in the absence of an electric field. It was a film whose transparency increased in the presence of an electric field. This is advantageous for privacy protection because the effect of transmitting light, which is a function of the window, can be exerted only when an electric field is applied, but there is a disadvantage that power must be continuously supplied to obtain transparency.

Accordingly, in the present invention, this problem was solved by developing a smart window film that is transparent when no electric field is present, but that can increase opacity by applying an electric field. At the same time, it is possible to provide a smart window film that can achieve this.

That is, the present invention sequentially includes a low-emission (low-E) film portion comprising a first metal oxide layer, a reflective metal layer and a second metal oxide layer; and

a first electrode layer in contact with one surface of the low-emission film part and sequentially; a liquid crystal unit including a liquid crystal having negative dielectric anisotropy; and a liquid crystal film part comprising a; and a second electrode layer;

It provides a reverse driving smart window film that satisfies the following conditional expression 1).

1) T _on < T _off

In the above condition 1), T _on represents the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when an 80V voltage is applied between the first electrode layer and the second electrode layer, and T _off is It shows the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when no voltage is applied.

In a preferred embodiment of the present invention, the reverse driving smart window film may further satisfy the following conditional expressions 2) and 3).

2) 6 ≤ T _off /T _on ≤ 30

3) 3% ≤ T _on ≤ 15%

In the above Conditional Expressions 2) and 3), T _off represents the light transmittance (%) of the reverse driving smart window film when no voltage is applied, and T _on is 80V between the first electrode and the second electrode. Shows the light transmittance (%) of the reverse driving smart window film when a voltage is applied.

By having such light transmission characteristics, the reverse driving smart window film according to the present invention can provide a smart window film that has clear transparency when no voltage is applied, but has excellent thermal insulation performance, and has excellent privacy protection effect by voltage application. there will be

Accordingly, the present invention is transparent when no voltage is applied, but excellent cooling and heating cost reduction efficiency can be obtained by the low-emission film unit, and when voltage is applied, transparency can be lowered to obtain the effect of privacy protection. A smart window can be provided.

According to a preferred embodiment of the present invention, the liquid crystal film unit may further include a liquid crystal film base layer, and more preferably, may further include an adhesive layer.

In addition, according to a preferred embodiment of the present invention, the low-emission film unit may further include a low-emission film base layer, more preferably, may further include a protective film layer.

3 is a view schematically showing a layered structure of a reverse driving smart window film according to a preferred embodiment of the present invention.

Referring to FIG. 3 , the reverse driving smart window film 1000 according to a preferred embodiment of the present invention includes a low-emission film unit 100 and a liquid crystal film unit 200 , and the low-emission film unit 100 . ) may include a low-emission film base layer 110 in contact with the liquid crystal film unit 200, and sequentially on the opposite side of the liquid crystal film unit 200 among both surfaces of the low-emission film base layer 110 A first metal oxide layer 120 , a reflective metal layer 130 , and a second metal oxide layer 120 ′ are formed, and a protective film layer 140 may be included on the second metal oxide layer 120 ′.

In addition, the liquid crystal film part 200 may include a liquid crystal film base layer 210, and the liquid crystal part 230 is the liquid crystal film base layer 210 by the first electrode layer 220 formed on one surface thereof. and is coupled to the reflective film unit 100 by the second electrode layer 220 ′ formed on the other surface of the liquid crystal unit 230 .

The liquid crystal unit 230 may include a liquid crystal layer 232 and a first alignment layer 231 and a second alignment layer 231 ′ formed on both surfaces of the liquid crystal layer.

According to a preferred embodiment of the present invention, the reverse driving smart window film has a total thickness of 50 to 200 μm, which may have a thinner thickness than that of a conventional smart window film. By having such a thin thickness, construction costs can be saved, and, nevertheless, the difference in transmittance between voltage applied and non-applied states is remarkable, so that shielding properties as a smart window can be excellently implemented.

Preferably, the thickness of the reverse driving smart window film may be 80 to 180 μm, more preferably 100 to 170 μm, and most preferably 120 to 150 μm. If the thickness of the reverse driving smart window film is less than 50 μm, product production may not be possible due to thermal deformation during manufacturing of the double-sided substrate. In addition, as the thickness further decreases, there may be a problem in that the shielding properties and interlayer adhesion when voltage is applied are deteriorated.

In addition, if the thickness of the reverse driving smart window film exceeds 200 μm, construction time and cost increase, and the transmittance when no voltage is applied decreases, thereby reducing transparency.

In addition, in a preferred embodiment of the present invention, the low-emission film portion and the liquid crystal film portion may have a thickness ratio of 1:1 to 1:2.5. More preferably, it may have a thickness ratio of 1:1.5 to 1:2.0, more preferably 1:1.6 to 1:1.8.

If the thickness ratio is less than 1:1 (that is, when the thickness of the low-emission film part is greater), there may be a problem of thermal deformation in the sputtering process of forming the electrode layer in the low-emission film base layer and the liquid crystal film part of the low-emission film part. If it exceeds 1:2.5 (that is, when the thickness of the liquid crystal film part becomes significantly thicker), the rate of defects in the process increases, such as tearing due to the difference in tension between the low-emissivity film part and the liquid crystal film part when manufacturing the smart window film there is a problem.

Hereinafter, each layer of the smart window film of the present invention will be described.

1. Low-emission film unit

Generally, a low-emission film or low-e film used for windows and doors refers to a film that passes visible or near-infrared rays but blocks rays with long wavelengths of mid-infrared to far-infrared rays from passing through.

The low-emission film (low-e film, 100) part of the present invention can reduce the solar heat gain (SHGC) and emissivity of the smart window to which the smart window film is applied, in addition to controlling the transparency of the smart window film, When applied to windows, it can exhibit the effect of reducing indoor heating and cooling costs. Since the smart window film according to the present invention has high transmittance when no voltage is applied, excellent solar heat gain (SHGC) and emissivity reduction are possible by combination with the low-emission film unit 100 .

In addition, due to the presence of the low-emissivity film part 100, it is possible to reduce the change in color difference in weather resistance, there is an advantage that can increase durability, thermal insulation performance and strength.

The low-emission film unit 100 is preferably a low-emission film base layer 110, a first metal oxide layer 120, a reflective metal layer 130, a second metal oxide layer 120' and a protective film layer ( 140) may be sequentially formed, and the first metal oxide layer 120, the reflective metal layer 130, and the second metal oxide layer 120' may be formed by a deposition process, such as sputtering, chemical vapor deposition or atomic layer deposition ( ALD) and the like. Preferably, it may be formed by a sputtering process.

1) Low-emission film base layer

The low-emission film unit 100 according to a preferred embodiment of the present invention may include a base layer 110 . The low-emissivity film base layer 110 serves as a support layer of the low-emission film unit 100, and serves as a substrate so that other layers of the low-emission film unit 100 can be formed thereon, thereby facilitating the process. to provide.

The base layer 110 may include without limitation as long as it is a material commonly used in the art, and may preferably include at least one selected from glass and polyethylene terephthalate (PET), and more preferably plasma or It may include a corona surface-treated PET film. When there is a process in which a roll is included during the lamination process, it is preferable to use a PET film having flexibility rather than a glass substrate as a substrate.

The low-emissivity film base layer 110 may have a thickness of 10-80 μm, preferably a thickness of 20-60 μm, and more preferably a thickness of 40-55 μm.

If the thickness is less than 10㎛, in manufacturing the smart window film, it may cause deformation of the substrate due to heat generated during drying and curing, and by the tension applied to the substrate during the roll-to-roll process There may be tearing issues. In addition, when the thickness exceeds 80 μm, the cost of the raw material increases, and the length that can be wound on one roll is shortened, which may lead to a problem of increasing the process time, such as an increase in the replacement time of the roll.

2) metal oxide layer

Next, the low-emission film unit 100 according to a preferred embodiment of the present invention includes metal oxide layers 120 and 120'. The metal oxide layer is formed on both surfaces of the reflective metal layer 130, respectively, and in this specification, for convenience, the side closer to the liquid crystal film 200 is the first metal oxide layer 120, and the oxide layer on the opposite side is the second metal. It is referred to as an oxide layer 120'.

The first metal oxide layer 120 and the second metal oxide layer 120 ′ each exhibit excellent emissivity maintenance durability, transmittance and thermal insulation performance, prevent weather resistance color difference change, and protect the reflective metal layer 30 . As to carry out, if it is a metal oxide commonly used in the art, it may include without limitation, but preferably zinc tin oxide (Zinc Tin Oxide, ZTO) may be included.

Preferably, the first metal oxide layer 120 and the second metal oxide layer 120 ′ each independently contain 25 to 45% by weight of zinc oxide (ZnO) based on the total weight, and tin oxide (SnO ₂ ) It may include zinc tin oxide containing 55 to 75% by weight.

If the content of zinc oxide (ZnO) is less than 25% by weight and the content of tin oxide (SnO2) exceeds 75% by weight, the durability of the metal oxide layer may be reduced, and the content of zinc oxide is 45% by weight. If it exceeds and the content of tin oxide (SnO2) is less than 55% by weight, the thermal insulation performance of the low-emission film part 100 may be reduced.

In addition, according to a preferred embodiment of the present invention, the first metal oxide layer 120 and the second metal oxide layer 120' are each independently 10 to 50 nm, preferably 20 to 40 nm, more preferably It may have a thickness of 25 to 35 nm.

If the thickness is less than 10 nm, the protective effect of the reflective metal layer 130 to be described later may be reduced, the emissivity and weather resistance color difference change may increase, and the durability of the reverse driving smart window film 1000 of the present invention may be reduced. , when the thickness exceeds 50 nm, the thermal insulation performance may be deteriorated due to an increase in emissivity.

3) Reflective metal layer

The reflective metal layer 130 included in the low-emission film unit 100 of the present invention is a layer capable of transmitting visible light (near infrared rays may also be included) and reflecting electromagnetic waves having a long wavelength of mid-infrared to far-infrared rays, and the The material may include, without limitation, any material that can be conventionally used for the reflective metal layer in the art, and preferably may include silver-palladium-copper alloy (Ag-Pd-Cu alloy, APC).

In addition, the reflective metal layer 130 may have a thickness of 10 to 20 nm, preferably 12 to 18 nm, more preferably 13.5 to 16.5 nm.

If the thickness of the reflective metal layer is less than 10 nm, there may be a problem in that the thermal insulation performance is lowered and the solar heat acquisition rate is increased. There may be issues that are going up.

According to a preferred embodiment of the present invention, the first metal oxide layer 120 , the reflective metal layer 130 , and the second metal oxide layer 120 ′ may satisfy both of the following conditions A) and B).

condition A)

condition B)

, 더욱 바람직하게는

일 수 있고, 조건 B)는 바람직하게는

, 더욱 바람직하게는

일 수 있다.Said condition A) is preferably

, more preferably

may be, and condition B) is preferably

, more preferably

can be

In the above conditions A) and B), a is the thickness of the first metal oxide layer 120 , b is the thickness of the second metal oxide layer 20 ′, and c is the thickness of the reflective metal layer 130 .

When the thickness of the reflective metal layer 130 is thin, the thermal insulation performance may not be good, and there may be a problem that the indoor temperature rises due to an increase in the solar heat acquisition rate. because it can increase. In addition, when the thickness of the first and second metal oxide layers 120 and 120 ′ is thin, the reflective metal layer 30 may not be protected, and durability may be reduced. There may be problems with degradation.

Therefore, the first metal oxide layer 120, the reflective metal layer 130, and the second metal oxide layer 120', which may be included in the reverse driving smart window film of the present invention, must have an appropriate thickness, and condition A) and conditions By satisfying all B), the above-mentioned problems can be solved.

이면, 역방향 구동 스마트 윈도우 필름의 내구성 및 단열 성능이 좋지 않을 수 있고, 방사율 및 내후성이 색차변화가 증가할 수 있으며, 태양열 차단 성능이 저하되어 태양열 취득율이 상승하는 문제가 있을 수 있다. 또한, 만일 상기 조건 B)에서

이면, 역방향 구동 스마트 윈도우 필름의 내구성이 저하될 수 있고, 내후성 색차변화가 증가할 수 있으며, 가시광선 투과율이 낮아지고 스마트 윈도우 필름의 반사율이 현저히 높아질 수 있다.If, in condition A) above,

If this is the case, the durability and thermal insulation performance of the reverse-driven smart window film may be poor, the color difference change in emissivity and weather resistance may increase, and the solar heat blocking performance may be lowered, so there may be a problem in that the solar heat gain is increased. Also, if condition B) above

In this case, the durability of the smart window film driven in the reverse direction may be reduced, the color difference change in weather resistance may be increased, the visible light transmittance may be lowered, and the reflectance of the smart window film may be significantly increased.

4) protective film layer

According to a preferred embodiment of the present invention, the low-emission film unit 100 may further include a protective film layer (140). The protective film layer 140 is formed on the second metal oxide layer 120', is formed at the outermost part of the smart window film, and serves to protect the reverse driving smart window film of the present invention. In particular, it functions to protect the first metal oxide layer 120 , the reflective metal layer 130 , and the second metal oxide layer 120 ′.

In addition, the protective film layer 140 can perform a function of remarkably improving the emissivity maintenance durability of the low-emissivity film unit 100, and the thickness thereof is preferably 0.5 to 2.5 μm, preferably 0.8 to 2.0 μm. may have a thickness of, more preferably, may have a thickness of 1.0 ~ 1.5㎛.

If the thickness of the protective film layer 140 is less than 0.5 μm, the emissivity maintenance durability and surface durability of the low-emissivity film part 100 may be reduced, and there may be a problem in that the weather resistance color difference change is increased. Conversely, when the thickness exceeds 2.5 μm, there may be a problem in that the emissivity increases.

In addition, the protective film layer 140 of the present invention may preferably include a copolymer of urethane acrylate, epoxy-modified acrylate, and acrylic resin. In this case, the urethane acrylate and the epoxy-modified acrylate may be oligomers or resins, preferably oligomers.

Specifically, the transparent protective layer 10 of the present invention contains urethane acrylate, epoxy-modified acrylate and acrylic resin in a weight ratio of 1: 0.2 to 3.5: 0.05 to 2.5, preferably 1: 0.3 to 3: 0.06 to 2 It may include a copolymer copolymerized in a weight ratio of At this time, if the weight ratio of the urethane acrylate and the epoxy-modified acrylate is less than 1:0.2, the surface hardness may be lowered and there may be a problem of scratching during smart window film construction. If the weight ratio exceeds 1:2.5, the smart window of the present invention The flexibility of the film is lowered, and cracks may occur on the surface. In addition, if the weight ratio of the urethane acrylate and the acrylic resin is less than 1:0.05, the degree of crosslinking may decrease and sufficient curing may not be achieved, and there may be a problem that the desired hardness cannot be reached. If the weight ratio exceeds 1:2.5, the degree of crosslinking may be reduced may rise and cracks may occur on the surface.

In addition, the copolymer that may be included in the transparent protective layer 10 of the present invention may have a weight average molecular weight of 800 to 15,000, preferably 1,000 to 10,000. If the weight average molecular weight is less than 800, the transparent protective layer 10 may become too hard and cracks may occur. If the weight average molecular weight exceeds 15,000, sufficient crosslinking may not occur and complete curing may not occur.

In addition, the copolymer that may be included in the transparent protective layer 10 of the present invention may have an acid value of 12 or less, preferably an acid value of 10 or less, an amine value of 7 or less, and preferably an amine value of 5 or less. have. If the acid value exceeds 12, there may be a problem of deterioration of durability and a large problem of weather resistance color difference change due to a radical reaction by light on the metal surface, and if the amine value exceeds 7, there may be a problem of yellowing by ultraviolet rays .

2. Liquid crystal film part

The liquid crystal film unit 200 is a part capable of variably controlling the light transmittance of the smart window film by applying external stimuli such as voltage, heat, and light, and may have high transmittance, low sheet resistance, and fast response speed. In particular, the liquid crystal of the liquid crystal part 230 has a negative dielectric anisotropy (Δε), so that when a voltage is applied, transparency is lowered due to a change in refractive index when a voltage is applied.

According to a preferred embodiment of the present invention, the liquid crystal film unit 200 includes a liquid crystal film base layer 210 , a first electrode layer 220 , a liquid crystal unit 230 , and a second electrode layer 220 ′ sequentially. can do. In this specification, for convenience, the electrode layer in contact with the liquid crystal film base layer 210 is referred to as the first electrode layer 220, and the electrode layer formed close to the low-emission film part 100 is referred to as the second electrode layer 220'.

In addition, the liquid crystal film base layer 210 may further include an adhesive layer 240 on the opposite surface of the first electrode layer 220 .

1) Liquid crystal part

The liquid crystal part of the present invention preferably includes the first alignment layers 231 and 231 ′ and a liquid crystal layer 232 interposed between the two alignment layers, and in the present specification, for convenience, the alignment layer in contact with the first electrode layer 220 is formed. The first alignment layer 231 and the alignment layer in contact with the second electrode layer are referred to as a second alignment layer 231 ′.

That is, in a preferred embodiment of the present invention, the liquid crystal unit may sequentially include a first alignment layer, a liquid crystal layer, and a second alignment layer.

The liquid crystal layer 232 of the present invention can change to a transparent, semi-transparent or opaque state by a driving voltage applied from the outside, and thus serves to change the transmittance of the smart window film, and a polymer network liquid crystal (Polymer Network Liquid) Crystal, PNLC) may include liquid crystals and polymer resins.

The liquid crystal layer preferably includes a cured product of liquid crystal ink including liquid crystal and a polymer resin, and the liquid crystal ink may further include a photoinitiator, a coupling agent and a spacer.

The polymer resin may be formed by polymerization of at least one of a monomer and an oligomer.

The monomer may preferably be polyfunctional, preferably styrene and its derivatives; Methyl, ethyl, propyl, butyl, pentyl, hexyl, amyl, 2-ethylhexyl, octyl, nonyl, dodecyl, isodecyl, lauryl, hexadecyl, cyclohexyl, benzyl, methoxyethyl, ethoxyethyl, part Toxyethyl, phenoxyethyl, allyl, metaallyl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-2-hydroxypropyl, dimethylaminohexyl, dimethylaminohexyl, isobornyl, etc. acrylate or methacrylate having the same substituent; Ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, tripropylene glycol, polypropylene glycol, butylene glycol, tetramethylene glycol, hexamethylene glycol, neopentine glycol, butanediol hexanediol, trimethylolpropane, penta Polyfunctional acrylates or methacrylates such as erythritol and dipentaerythritol and derivatives thereof may be used, but the present invention is not limited thereto, and those skilled in the art in consideration of the refractive index of the liquid crystal and the polymer among monomers that can be used in the polymer dispersed liquid crystal can choose the appropriate one. Preferably, the monomer may be an acrylate-based monomer, more preferably a polyfunctional acrylate-based monomer.

In addition, the oligomer may be preferably a polyfunctional oligomer, and preferably may be one or more selected from aromatic urethane acrylates, aliphatic urethane acrylates, epoxy acrylates, polyester acrylates, and derivatives thereof. However, the type of the oligomer is not necessarily limited thereto, and a person skilled in the art may select an appropriate one from among the oligomers that can be used in the polymer dispersed liquid crystal in consideration of the refractive indices of the liquid crystal and the polymer. Preferably, the oligomer may be a urethane acrylate oligomer, and more preferably a polyfunctional urethane acrylate oligomer.

The polymer resin is a polymer formed by polymerization of at least one of the oligomer and the monomer, and may have a viscosity of 800 to 1500 cPs, preferably 900 to 1200 cPs. If the viscosity of the polymer resin is less than 800 cPs, liquid crystal flows easily and there may be a problem in that the production yield decreases during the coating process. It is difficult to uniformly mix between liquids, and it is difficult to achieve a uniform thickness due to the characteristics of the gap coating method, so that the optical quality of the smart window film may be deteriorated.

In a preferred embodiment of the present invention, the liquid crystal may have a dielectric anisotropy (Δε) of -6.0 to -1.0, and a refractive index anisotropy (Δn) of 0.07 to 0.15.

Since the dielectric anisotropy has a negative value, when a voltage is applied, the liquid crystal molecules receive a force so that the long axis direction is perpendicular to the electric field direction, and accordingly, the liquid crystal orientation is randomized and transparency is lowered.

If the dielectric anisotropy is less than -6.0, the arrangement of the liquid crystal molecules becomes more aligned when a voltage is applied, so that the decrease in light transmittance and the occurrence of haze are not clear, so there may be a problem in that the functionality as a smart window is deteriorated.

Conversely, when the dielectric anisotropy exceeds -1.0, the liquid crystal molecules are less affected by the electric field in the range of 0 or less, so that the transmittance decrease and haze generation due to voltage application do not occur clearly. An impossible problem arises. If the dielectric anisotropy exceeds 0, when a voltage is applied, the long-axis direction of the liquid crystal molecules is aligned parallel to the electric field, so the reverse driving smart window film desired in the present invention does not work.

In the case of refractive index anisotropy, if the refractive index anisotropy of the liquid crystal is less than 0.07, the change in refractive index due to the rotation of the liquid crystal molecules is not clear, so the decrease in transmittance and the occurrence of haze do not occur sufficiently. have. In addition, when the refractive index anisotropy exceeds 0.15, there may be a problem in that the transmittance when no voltage is applied or the viewing angle is decreased.

In a preferred embodiment of the present invention,

The liquid crystal is a bicyclohexyl-based compound, a cyclohexylphenyl-based compound, a cyclohexene-based, cyclohexylcarboxylic acid ester-based, difluorine-phenylene (difluorine)-based compound ( It may include at least one selected from phenylene)-based compounds, bicyclo hydrocarbon compounds, and tricyclo hydrocarbon-based compounds. However, the liquid crystal compound is not necessarily limited to the above compound, and has a dielectric constant and refractive index anisotropy necessary for achieving the object of the present invention, can be well dispersed in a polymer resin, and can be well aligned in one direction by an alignment layer. A person skilled in the art can easily select from liquid crystal compounds that can be used in the art.

In a preferred embodiment of the present invention, the liquid crystal ink may include the liquid crystal and the polymer resin in a weight ratio of 30:70 to 55:45. More preferably, it may be included in a weight ratio of 35:65 to 50:50, and most preferably 40:60 to 50:50.

If the weight ratio of the liquid crystal is less than 30% of the sum of the weight of the liquid crystal and the polymer resin, the adhesion of the liquid crystal layer to the alignment film increases, but the degree of crosslinking of the polymer resin increases, so that the alignment performance of the liquid crystal is lowered, thereby the transmittance and haze of the smart window film There is a problem in that the rate of change is lowered. In addition, if the weight ratio of the liquid crystal exceeds 55%, on the contrary, the adhesion of the liquid crystal layer to the alignment film is reduced, thereby reducing durability.

In addition, the liquid crystal layer 232 may have a thickness of 10 to 25 μm, preferably a thickness of 16 to 24 μm, and most preferably a thickness of 18 to 22 μm. If the thickness is less than 10 μm, the uniformity of the product mura defect may occur, haze may not be sufficiently generated, and there is a problem in that adhesion to the alignment layer decreases. There may be a problem with the angle lowering.

In a preferred embodiment of the present invention, the first alignment layer 231 and the second alignment layer 231 ′ may include a polyimide-based polymer and each independently have a thickness of 100 to 300 nm. However, it is not necessarily limited to the polyimide-based polymer, and may be formed of a polymer layer having a uniform thickness having properties such as thin film coating property, high purity, and storage stability.

The alignment layer induces alignment of liquid crystal molecules in the liquid crystal layer 232 due to the alignment of the side chains, so that the liquid crystal molecules in the liquid crystal layer 232 are aligned in a direction perpendicular to the alignment layer when no voltage is applied. Accordingly, the liquid crystal layer 232 according to the present invention has high transmittance and low haze when no voltage is applied, thereby increasing transparency.

If the thickness of the alignment layer is less than 100 nm, the liquid crystal may not be properly aligned due to the lack of an absolute amount of side chains capable of aligning the liquid crystal. The optical properties of the sample may be degraded.

In a preferred embodiment of the present invention, the liquid crystal layer may have an adhesive force of the liquid crystal layer to the alignment layer measured according to the following measuring method with respect to the alignment layer of 10 to 100 gf/inch.

[How to measure]

The first alignment layer and the second alignment layer of the reverse driving smart window film are peeled off by 180° at a rate of 10 mm/min, and the adhesive force of the liquid crystal layer to the alignment layer is measured.

If the adhesive strength is less than 10 gf/inch, there may be a problem in that the durability of the smart window film is deteriorated. Conversely, if it exceeds 100 gf/inch, there is no problem in durability, but the performance of the liquid crystal molecules is lowered and the light transmittance of the smart window film is reduced. And there may be a problem that the haze change rate is lowered.

2) electrode layer

The liquid crystal film unit 200 of the present invention further includes electrode layers 220 and 220 ′ formed on both surfaces of the liquid crystal unit 230 . As described above, the electrode layer in contact with the liquid crystal film base layer 210 is referred to as the first electrode layer 220 , and the electrode layer close to the low-emission film part 100 is referred to as the second electrode layer 220 ′.

Driving power is applied to the first electrode layer 220 and the second electrode layer 220 ′, and serves to supply the applied driving power to the liquid crystal unit 230 . The first electrode layer 220 and the second electrode layer 220 ′ of the present invention may include at least one selected from various metals having conductivity, metal oxides, and conductive polymers, respectively, and preferably indium tin oxide (indium tin oxide). oxide, ITO) and at least one selected from a conductive polymer, more preferably indium tin oxide (ITO).

The first electrode layer 220 and the second electrode layer 220 ′ may each independently have a thickness of 15 to 40 nm, preferably 20 to 30 nm, more preferably 22.5 to 27.5 nm. If the thickness of the electrode layers 220 and 220' is less than 15 nm, there may be a problem in that the resistance is increased and the reaction rate is lowered, and if it exceeds 40 nm, the transmittance of the substrate is lowered and there may be a problem of visibility.

In addition, the first electrode layer 220 and the second electrode layer 220' each independently have a sheet resistance of 30 to 200 Ω/□, preferably 80 to 180 Ω/□, more preferably 135 to 165 Ω/□. can be

If the sheet resistance of the electrode layers 220 and 220' is less than 30 Ω/□, the transmittance of the substrate may be lowered and there may be a problem of visibility, and if it exceeds 200 Ω/□, there may be a problem that the reaction rate of the liquid crystal unit is lowered. can

3) Liquid crystal film base layer

Next, the liquid crystal film base layer 90 of the present invention serves as a support layer for the reverse film unit, and may include any material commonly used in the art without limitation, preferably glass and PET (Polyethylene terephthalate). ) may include at least one selected from among, more preferably, plasma or corona-treated PET.

In addition, the liquid crystal film base layer 90 of the present invention may have a thickness of 10 to 190 μm, preferably a thickness of 40 to 60 μm, more preferably a thickness of 45 to 55 μm, and if the thickness is 10 μm If it is less than this, in manufacturing the smart window film, deformation of the substrate due to heat generated during drying and curing may occur, and tearing may occur due to tension applied to the substrate during the roll-to-roll process. In addition, when the thickness exceeds 190 μm, there may be problems in increasing the raw material cost and increasing the process time due to the increase in the replacement time of the roll because the length that can be wound on one roll is shortened.

4) Adhesive layer

According to a preferred embodiment of the present invention, the liquid crystal film unit 200 may further include an adhesive layer 240 . The adhesive layer 240 serves to adhere the smart window film to the glass, and may include without limitation as long as it is a component of an adhesive layer that can be used in a conventional smart window film, preferably polyester resin, urethane resin, It may include one or more selected from resins including acrylic resins and derivatives thereof, and preferably, acrylic resins.

In addition, the pressure-sensitive adhesive layer 100 of the present invention may have a thickness of 10 to 30 μm, preferably 16 to 24 μm, more preferably 18 to 22 μm, and if the thickness is less than 10 μm, the adhesive force will decrease. If the thickness exceeds 30 μm, there may be a problem in that the cost of raw materials increases and the curing time becomes longer, which lowers the production rate and requires a large amount of heat, thereby increasing energy consumption.

On the other hand, the pressure-sensitive adhesive layer 100 of the present invention may further include a UV/near-infrared blocking agent in order to provide better UV and near-infrared blocking performance. The UV/NIR blocker may include without limitation any UV/NIR blocker commonly used in the art, preferably tungsten trioxide, antimony tin oxide (ATO), indium tin oxide (Indium Tin Oxide) , cesium tungstate oxide (CTO) and zinc oxide (Zinc Oxide, ZnO) may include at least one selected from the group consisting of. In this case, the ultraviolet/near-infrared blocking agent may be provided in the form of a sol, but is not limited thereto.

Hereinafter, each step will be described with respect to the manufacturing process of the reverse driving smart window film according to a preferred embodiment of the present invention. Among them, portions overlapping with those described in each configuration of the reverse driving smart window film will be omitted.

The reverse driving smart window film according to the present invention is manufactured by a process having the following steps.

First step: a first film unit in which a first electrode layer and a first alignment layer are sequentially formed on one surface of the liquid crystal film base layer; and preparing a second film part in which a second electrode layer and a second alignment film are sequentially formed on one surface of the low-emission film base layer.

Second step: After introducing a liquid crystal ink containing liquid crystal having a negative dielectric anisotropy to face the first alignment layer of the first film part and the second alignment layer of the second film part between the first alignment layer and the second alignment layer, lamination and curing to form a liquid crystal layer between the first alignment layer and the second alignment layer to obtain a smart window film.

That is, according to the present invention, the first and second film portions in which electrode layers 220 and 220 ′ and alignment layers 231 and 231 ′ are sequentially formed on two substrates 110 and 210 with the liquid crystal layer 232 as the center, respectively. A film part is prepared, and the first alignment layer 231 and the second alignment layer 231' respectively formed on the first film part and the second film part are made to face each other, and then liquid crystal ink is introduced therebetween and laminated to form a laminate. and curing the liquid crystal ink of the laminate to form the liquid crystal layer 232 .

Since the reflective metal layer 130 and the metal oxide layers 120 and 120' that function as the low-emission film part 100 are absent in the laminate formed by the above method, it is necessary to form them.

A method of forming the low-emission film portion is divided into two methods.

The first method is a first metal oxide layer 120, a reflective metal layer 130 and a second metal oxide layer 120' sequentially on the opposite surface of the surface on which the electrode layer 220' of the low-emission film base layer 110 is formed. ) to manufacture a first film part, and laminating this with the second film part and liquid crystal ink therebetween.

According to this method, only two base films 110 and 210 need to be used, and the process of laminating the low-emission film part 100 and the liquid crystal film part 200 is unnecessary, so the thickness is reduced and the process is simplified. have.

The second method is to sequentially form a first metal oxide layer 120, a reflective metal layer 130 and a second metal oxide layer 120' on one surface of the low-emission film base layer 110 to manufacture a low-emission film,

A second electrode layer 220 ′ and a second alignment layer 230 ′ are formed on a separate substrate layer (the same film as the low-emission film substrate layer or the liquid crystal film substrate layer can be used), and the second film unit and the alignment film ( 230, 230') to face each other, and then introducing a liquid crystal ink therebetween, laminating and curing to form a liquid crystal film, and laminating the low-emissivity film and the liquid crystal film with an adhesive to prepare a smart window film.

In the case of this method, there is a disadvantage in that the thickness increases, but since the low-emission film and the liquid crystal film can be manufactured as independent products, there is an advantage in that the implementation performance is increased.

In this case, when the electrode layers 220 and 220 ′, the metal oxide layers 120 and 120 ′, and the reflective metal layer 130 are formed on each substrate, they may be formed by the deposition process as described above. Preferably, a sputtering process may be used.

In addition, the alignment layers 231 and 231 ′, the adhesive layer, and the protective film layer may be formed by a coating process. The coating method may be selected without limitation as a method usable in the art, but preferably gravure coating or spin coating may be performed.

In a preferred embodiment of the present invention, curing in the second step may be UV curing.

In a preferred embodiment of the present invention, in the second step, curing may be performed by irradiating ultraviolet rays with an intensity of 1 to 10 mW/cm ² for 1000 to 5000 seconds.

The intensity of the ultraviolet rays is more preferably 4 to 9 mW/cm ² , more preferably 6 to 8 mW/cm ² It can be irradiated with an intensity of. If the intensity of ultraviolet light is less than 5 mW/cm ² , the adhesion between the alignment layer and the liquid crystal layer is not sufficient, which may be the reason for the deterioration of the durability of the smart window film. Conversely, when the intensity of UV light exceeds 10mW/cm ² , the adhesive force may increase, but the side chain of the alignment layer may be decomposed, which may cause the transparency of the smart window film to decrease when no voltage is applied. have.

The present invention also provides a window; And the reverse driving smart window film provided on at least one side of the window; provides a reverse driving smart window comprising a.

Hereinafter, the present invention will be described in detail with respect to its effects by way of examples. However, the technical spirit of the present invention is not limited to the following examples, and the following examples are merely exemplary embodiments for helping understanding of the present invention, and those of ordinary skill in the art are within the scope of the technical spirit of the present invention. It will be understood that the configuration can be easily implemented by adding, omitting, and changing the configuration to achieve individual purposes.

<Example>

Example 1: Preparation of smart window film

1) Preparation of liquid crystal ink:

A mixture of 0.7 g of aliphatic urethane acrylate, 0.1 g of butyl acrylate, 0.1 g of benzyl acrylate, 0.1 g of hydroxyphenoxypropyl acrylate and 0.1 g of 2,4,6-trimethylbenzoyldiphenyl phosphine oxide as a polymerization initiator. A total of 1.1 g of the polymer resin composition and 0.9 g of NVJ-71 as a liquid crystal compound were mixed to prepare a liquid crystal ink.

2) Preparation of the laminate:

A solution obtained by dissolving polyimide at a concentration of 5wt% in normal-methyl-2-pyrrolidone solvent as an alignment film solution on the electrode surface of a PET substrate (thickness 188㎛) on which an ITO electrode (thickness 25nm) is formed through a sputtering process It was applied using a spin coater and heat-treated at 130° C. for 10 minutes in an oven to form an alignment layer with a thickness of 150 nm.

Two substrates are prepared, one is referred to as an upper substrate and the other is referred to as a lower substrate.

Sputtering was performed on the opposite surface of the alignment layer of the upper substrate to sequentially form a ZTO layer, an APC layer, and a ZTO layer to a thickness of 30 nm, 15 nm, and 30 nm, respectively. After dropping the liquid crystal ink on the alignment layer of the upper substrate and facing the alignment layer of the lower substrate, bonding was performed, and gap coating was performed under the condition that the thickness of the liquid crystal layer was 10 μm to obtain a laminate.

3) UV curing

The laminate was irradiated with ultraviolet light for 1500 seconds using a BL lamp having an illuminance of 2 mW/cm ² to obtain a reverse driving smart window film.

Examples 2-15 and Comparative Example 1

A smart window film was prepared in the same manner as in Example 1, but the detailed configuration was different as shown in Table 1 below.

Comparative Example 1 uses a liquid crystal compound having a dielectric anisotropy of 7.1 and a refractive index anisotropy of 0.098, unlike Example 1, and the other configuration is Example 1 was prepared in the same way as

In Comparative Example 2, a smart window film was prepared in the same manner as in Example 1 except for the step of forming the ZTO and APC layers on the upper substrate.

division liquid crystal/polymer
weight ratio liquid crystal
type UV illuminance
(mW/cm ² ) liquid crystal layer thickness
(μm) alignment film thickness
(nm) low-emission film
The presence or absence Example 1 45:55 NVJ-71 2 10 150 ○ Example 2 35:65 NVJ-71 2 10 150 ○ Example 3 50:50 NVJ-71 2 10 150 ○ Example 4 55:45 NVJ-71 2 10 150 ○ Example 5 60:40 NVJ-71 2 10 150 ○ Example 6 50:50 NVJ-71 5 10 150 ○ Example 7 50:50 NVJ-71 7.5 10 150 ○ Example 8 50:50 NVJ-71 10 10 150 ○ Example 9 50:50 NVJ-71 14.5 10 150 ○ Example 10 50:50 NVJ-71 2 5 150 ○ Example 11 50:50 NVJ-71 2 18 150 ○ Example 12 50:50 NVJ-71 2 20 150 ○ Example 13 50:50 NVJ-71 2 22 150 ○ Example 14 50:50 NVJ-71 2 25 150 ○ Example 15 50:50 NVJ-71 2 30 150 ○ Example 16 50:50 NVJ-71 2 20 80 ○ Example 17 50:50 NVJ-71 2 20 400 ○ Comparative Example 1 45:55 NTJ-10 2 10 - ○ Comparative Example 2 45:55 NVJ-71 2 10 150 × * NVJ-71 is a liquid crystal compound and has a dielectric anisotropy (Δε) of -3.5 and a refractive index anisotropy (Δn) of 0.102.
* NTJ-10 is a liquid crystal compound and has a dielectric anisotropy (Δε) of 7.1 and a refractive index anisotropy (Δn) of 0.098.

<Experimental example>

Experimental Example 1: Measurement of transmittance and haze

Transmittance and haze of the smart window films prepared according to Examples and Comparative Examples were measured using a BYK haze-gard plus spectroscopic haze meter.

Specifically, by using the above equipment, light was transmitted through the smart window film to measure the opacity state due to diffusion in addition to reflection or absorption. Measurements were divided into a time when no voltage was applied (OFF) and a time when a voltage of 80V was applied between both electrodes (ON).

Experimental Example 2: Liquid crystal part adhesive force measurement

Each of the adhesive force measurement specimens according to Examples and Comparative Examples are prepared, and the prepared test specimens are cut to a width of 1 inch to prepare an adhesion test specimen.

Prepare the specimen so that it can be pulled in the 180 degree direction by folding the upper substrate among the specimens. At this time, the total length of the attached liquid crystal layer should be 100 mm or more. The prepared specimen was pulled at a speed of 10 mm/min using a UTM device and the value was measured. At this time, the measurement length was 100 mm, and the average value from the initial 10 mm section to the 90 mm section was recorded.

Experimental Example 3: Measurement of emissivity and solar heat gain

Spectroscopy capable of measuring at least 5 to 25 μm of the thermal radiation wavelength range of 5 to 50 μm at room temperature as the ratio of the heat radiation radiation power radiated by the glass plate to the heat radiation radiation power emitted by a black body of the same temperature The normal emissivity value (corrected emissivity) calculated by the method specified in KS L2514 is shown using the spectral reflectance measured with a measuring instrument.

In addition, with respect to solar radiation perpendicular to the surface of the window glass, the ratio of the radiation flux of solar radiation passing through the glass part and the heat flux absorbed by the glass and transferred to the room is the ratio to the radiation flux of the incident solar radiation, KS The solar heat gain was measured by the test method of L 2514.

Results evaluated according to the experimental example are shown in Table 2 below.

division emissivity
(%) solar heat gain
(%) adhesiveness
(gf/inch) Light transmittance (OFF/ON)
(%) Haze (OFF/ON)
(%) Example 1 0.13 0.26 7.8 78.1/8.3 7.0/95.3 Example 2 0.13 0.26 7.7 78.4/78.9 6.6/84.1 Example 3 0.13 0.26 4.2 77.8/16.2 10.2/90.9 Example 4 0.13 0.26 2.6 71.6/26.2 20.0/82.9 Example 5 0.13 0.26 0.8 58.8/27.7 39.1/80.7 Example 6 0.13 0.26 8.3 81.1/5.6 5.6/98.7 Example 7 0.13 0.26 9.2 81.6/6.3 4.7/97.6 Example 8 0.13 0.26 11.9 80.9/9.8 5.1/92.9 Example 9 0.13 0.26 19.8 77.8/9.5 9.3/93.7 Example 10 0.13 0.26 5.3 82.3/20.1 3.2/78.9 Example 11 0.13 0.26 7.6 76.4/10.1 10.2/94.0 Example 12 0.13 0.26 7.2 77.0/9.8 8.6/95.9 Example 13 0.13 0.26 7.2 73.8/8.1 12.9/96.5 Example 14 0.13 0.26 9.6 65.7/24.9 28.6/82.5 Example 15 0.13 0.26 12.3 43.6/50.7 52.9/72.3 Example 16 0.13 0.26 7.7 88.6/7.9 11.2/87.2 Example 17 0.13 0.26 7.9 68.1/4.7 16.2/94.4 Comparative Example 1 0.08 0.18 7.7 6.5/88.1 91.6/10.8 Comparative Example 2 0.21 0.44 7.6 78.4/9.1 89.6/9.1

Referring to Table 2, the smart window films of Examples using NVJ-71 having negative dielectric anisotropy as a liquid crystal had transmittance without voltage applied higher than transmittance when voltage was applied, and haze was the opposite.

However, it was confirmed that the smart window film according to Comparative Example 1 had a transmittance when a voltage was applied, higher than a transmittance when no voltage was applied, and a haze was lower when a voltage was applied compared to when no voltage was applied, thereby operating in the opposite direction.

In addition, as a result of Comparative Example 2 not including the low-emissivity film part, it was confirmed that the emissivity and the solar heat acquisition rate were significantly higher than those of Examples.

In addition, as the liquid crystal content in the liquid crystal layer increased, it was confirmed that the adhesive force of the liquid crystal layer to the alignment layer layer decreased. In the appropriate range, when the liquid crystal content was 55% or less, the change in adhesion and transmittance was excellent, and 45% was the best.

In addition, as a result of changing the UV curing conditions, it was found that the stronger the UV intensity, the stronger the adhesive force, but it was found that the changes in haze and light transmittance gradually decreased. The appropriate range was 10 mW/cm ² or less.

In addition, when the thickness of the liquid crystal layer was 20 μm, the difference in transmittance and haze when voltage was applied/not applied was increased.

When the thickness of the alignment layer was too small, there was a problem in that the alignment of the liquid crystal was not sufficient, and when the thickness was too large, the alignment performance deteriorated and the alignment layer had a unique color, and it was confirmed that the optical performance was impaired.

1000: smart window film
100: low-emission film unit
110: low-emission film base layer
120, 120': metal oxide layer
130: reflective metal layer
140: protective layer
200: liquid crystal film unit
210: liquid crystal film base layer
220, 220': electrode layer
230: liquid crystal unit
231, 231': alignment layer
232: liquid crystal layer
240: adhesive layer
300: first film unit
400: second film unit

Claims (16)

a low-emission (low-E) film unit including a first metal oxide layer, a reflective metal layer, and a second metal oxide layer sequentially; and
a first electrode layer formed on one surface of the low-emission film unit and sequentially; a liquid crystal unit including a liquid crystal having negative dielectric anisotropy; and a liquid crystal film unit comprising a; and a second electrode layer;
Reverse driving smart window film satisfying the following condition 1):
1) T _on < T _off
In the above condition 1), T _on represents the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when an 80V voltage is applied between the first electrode layer and the second electrode layer, and T _off is It shows the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when no voltage is applied. According to claim 1,
The liquid crystal unit sequentially includes a first alignment layer, a liquid crystal layer and a second alignment layer,
The first alignment layer and the second alignment layer include a polyimide-based polymer, and each independently a reverse driving smart window film having a thickness of 100 to 300 nm. According to claim 1,
The reverse driving smart window film is a reverse driving smart window film, characterized in that it further satisfies the following conditional expressions 2) and 3):
2) 6 ≤ T _off /T _on ≤ 30
3) 3% ≤ T _on ≤ 15%
In the above Conditional Expressions 2) and 3), T _off represents the light transmittance (%) of the reverse driving smart window film when no voltage is applied, and T _on is 80V between the first electrode and the second electrode. Shows the light transmittance (%) of the reverse driving smart window film when a voltage is applied. According to claim 1,
The liquid crystal layer includes a cured product of a liquid crystal ink containing a polymer resin and liquid crystal,
The liquid crystal has a dielectric anisotropy (Δε) of -6.0 to -1.0, and a reverse driving smart window film, characterized in that the refractive index anisotropy (Δn) is 0.07 to 0.15. 5. The method of claim 4,
The liquid crystal is a bicyclohexyl-based compound, a cyclohexylphenyl-based compound, a cyclohexene-based compound, a cyclohexylcarboxylic acid ester-based compound, a difluorophenylene-based compound, and a non It contains at least one selected from cyclohydrocarbon compounds and tricyclohydrocarbon-based compounds,
The polymer resin may include at least one oligomer selected from an aromatic urethane acrylate oligomer, an aliphatic urethane acrylate oligomer, and a polyester acrylate oligomer; and at least one monomer selected from acrylate-based monomers, epoxy-based monomers and siloxane-based monomers; As formed by polymerization of one or more of, the reverse driving smart window film, characterized in that the viscosity is 800 ~ 1500 cPs. According to claim 1,
The liquid crystal ink is a reverse driving smart window film, characterized in that it contains the liquid crystal and the polymer resin in a weight ratio of 30:70 to 55:45. According to claim 1,
The first electrode layer and the second electrode layer each independently include at least one selected from indium tin oxide (ITO) and a conductive polymer,
Reverse driving smart window film, characterized in that each independently has a sheet resistance of 30~200Ω/□. According to claim 1,
The reflective metal layer includes a silver-palladium-copper alloy (Ag-Pd-Cu alloy, APC),
The first metal oxide layer and the second metal oxide layer are each independently zinc oxide (ZnO) 25 to 45% by weight and tin oxide (SnO ₂ ) Zinc tin oxide containing 55 to 75% by weight (Zinc Tin Oxide, ZTO), characterized in that it comprises a reverse driving smart window film. According to claim 1,
The low-emission film unit further comprises a transparent protective layer and a low-emission film base layer, the liquid crystal film unit further comprising a liquid crystal film base layer,
Each layer is a liquid crystal film base layer, a first electrode layer, a liquid crystal part, a second electrode layer, a low-emission film base layer, a first metal oxide layer, a reflective metal layer, a reverse driving, characterized in that provided in the order of the second metal oxide layer Smart Window Film. According to claim 1,
The reverse driving smart window film has a total thickness of 50 ~ 200㎛,
A reverse driving smart window film, characterized in that the thickness ratio between the low-emission film part and the liquid crystal film part is 1:1 to 2.5. According to claim 1,
Reverse driving smart window film, characterized in that the adhesive force of the liquid crystal layer to the alignment film measured according to the following measuring method is 10 ~ 100 gf / inch:
[How to measure]
The adhesive force of the liquid crystal layer to the alignment layer is measured by peeling the first alignment layer and the second alignment layer 180° at a rate of 10 mm/min of the reverse driving smart window film. a first film unit in which a first electrode layer and a first alignment film are sequentially formed on one surface of the liquid crystal film base layer; and a first step of preparing a second film part in which a second electrode layer and a second alignment film are sequentially formed on one surface of the low-emission film base layer; and
The first alignment layer of the first film portion and the second alignment layer of the second film portion are opposed to each other, and a liquid crystal ink including liquid crystal having negative dielectric anisotropy is introduced between the first alignment layer and the second alignment layer, and then laminated and cured to a second step of forming a liquid crystal layer between the first alignment layer and the second alignment layer to obtain a smart window film;
including,
The smart window film is a method of manufacturing a reverse driving smart window film, characterized in that it satisfies the following condition 1):
1) T _on < T _off
In the above condition 1), T _on represents the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when an 80V voltage is applied between the first electrode layer and the second electrode layer, and T _off is It shows the light transmittance (%) for the D65 standard light source of the reverse driving smart window film when no voltage is applied. 13. The method of claim 12,
The second film unit sequentially forms a first metal oxide layer, a reflective metal layer and a second metal oxide layer on one surface of the low-emission film base layer,
A method of manufacturing a reverse driving smart window film, characterized in that it is manufactured by sequentially forming the second electrode layer and a second alignment layer on the other surface of the low-emission film base layer. 13. The method of claim 12,
Curing in the second step is a method of manufacturing a reverse driving smart window film, characterized in that UV curing. 13. The method of claim 12,
The second step is a method of manufacturing a smart window film, characterized in that curing is performed by irradiating ultraviolet rays with an intensity of 1 to 10 mW/cm ² for 1000 to 5000 seconds. windows; and a reverse driving smart window film according to any one of claims 1 to 11 provided on at least one side of the window.

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