KR20230102899A - Liquid crystal-based smart window film - Google Patents

Abstract

Provided is a liquid crystal-based smart window film that improves deterioration by minimizing liquid crystal fluidity that may occur due to external pressure (including gravity). A liquid crystal-based smart window film according to an embodiment includes a liquid crystal layer provided in a cell gap and including a liquid crystal and a polymer mesh, and a first alignment layer disposed on a light input side and a light output side of the liquid crystal layer to set the cell gap. and a second alignment layer, a first transparent electrode and a second transparent electrode disposed on each of the first alignment layer and the second alignment layer, and a polarizing plate and a photolithography plate disposed on each of the first transparent electrode and the second transparent electrode. The polymer mesh film fixes the liquid crystal to the first alignment layer and the second alignment layer.

Description

Liquid crystal-based smart window film {LIQUID CRYSTAL-BASED SMART WINDOW FILM}

The present invention relates to a liquid crystal-based smart window film, and more particularly, to a liquid crystal-based smart window film that adjusts transmittance using polarization of light.

As is known, a conventional liquid crystal-based smart window film includes a polymer disperse liquid crystal (PDLC) and a polymer network liquid crystal (PNLC).

Polymer dispersed liquid crystal (PDLC) converts from opaque to transparent by transmitting or scattering light according to the application of power, and polymer mesh liquid crystal (PNLC) converts from transparent to opaque.

Since PDLC and PNLC-based smart window films use light scattering, they block the front view while blocking light in the scattering state.

Provided is a liquid crystal-based smart window film that improves deterioration by minimizing liquid crystal fluidity that may occur due to external pressure (including gravity).

A liquid crystal-based smart window film according to an embodiment of the present invention is provided in a cell gap and includes a liquid crystal layer including a liquid crystal and a polymer net film, respectively disposed on a light incident side and a light output side of the liquid crystal layer to set the cell gap. A first alignment layer and a second alignment layer, a first transparent electrode and a second transparent electrode disposed on the first alignment layer and the second alignment layer, respectively, and a polarizing plate and a photodetector disposed on each of the first transparent electrode and the second transparent electrode. It includes a plate, and the polymer mesh film fixes the liquid crystal to the first alignment layer and the second alignment layer.

The liquid crystal has a positive dielectric constant anisotropy (Δε) and may include a chiral dopant.

The dielectric constant anisotropy (Δε) of the liquid crystal may have a negative value.

The polymer mesh is formed of a monomer for UV curing, and may be formed of one of a polyide-based material and an acrylate material.

The liquid crystal-based smart window film according to an embodiment of the present invention further includes a spacer disposed between the first alignment layer and the second alignment layer to set the thickness of the liquid crystal layer, and the polymer mesh film forms the spacer as described above. It may be fixed to the first alignment layer and the second alignment layer.

The spacer may be formed of a ball or columnar polymer.

The first alignment layer and the second alignment layer may be formed of a polymer layer that determines initial alignment of liquid crystal molecules.

A polarization axis of the polarizer and a polarization axis of the detector plate may be orthogonal to each other.

The first alignment layer and the second alignment layer are formed as horizontal alignment layers, the first alignment layer is oriented in the same direction as the polarization axis of the polarizing plate, and the pre-tilt angle of the liquid crystal is 1 to 5 degrees, The second alignment layer may be aligned in the same direction as the polarization axis of the detector plate.

The first alignment layer and the second alignment layer are formed of vertical alignment layers, the first alignment layer is oriented in a direction of 45 degrees to the polarization axis of the polarizing plate, and the pre-tilt angle of the liquid crystal is 98 to 99 degrees. , the second alignment layer may be aligned in a direction of 45 degrees to the polarization axis of the detector plate.

The first alignment layer and the second alignment layer may have surface curves and polymer arrangements regularly formed by mechanical friction.

A mechanical rubbing direction of the first alignment layer and a mechanical rubbing direction of the second alignment layer may be orthogonal to each other.

The first alignment layer and the second alignment layer may have a regular arrangement of polymers by polarized UV irradiation.

A liquid crystal-based smart window film according to an embodiment of the present invention is disposed between the polarizing plate and the first alignment film, and includes a first substrate made of transparent plastic material on which the first transparent electrode is formed, and the light detector plate and the second substrate. A second substrate made of a transparent plastic material disposed between the alignment layers and having the second transparent electrode formed thereon may be further included.

As described above, since the liquid crystal layer includes the liquid crystal and the polymer mesh and the polymer mesh fixes the liquid crystal to the first alignment layer and the second alignment layer, liquid crystal liquidity and deterioration may be improved. Therefore, the durability of the liquid crystal-based smart window film is improved, and the transmittance can be adjusted without light scattering.

In addition, since the polymer mesh fixes the spacer to the first alignment layer and the second alignment layer, liquid crystal fluidity and deterioration may be improved.

1 is a cross-sectional view of a liquid crystal-based smart window film according to a first embodiment of the present invention.
FIG. 2 is a plan view illustrating polarization axis directions of the polarizer and the detector plate of FIG. 1 and alignment directions of the first alignment layer and the second alignment layer.
3 is a cross-sectional view of a liquid crystal-based smart window film according to a second embodiment of the present invention.
FIG. 4 is a plan view illustrating directions of polarization axes of the polarizer and the detector plate of FIG. 3 and alignment directions of the first alignment layer and the second alignment layer.
5 is a cross-sectional view of a liquid crystal-based smart window film according to a third embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. In order to clearly describe the present invention in the drawings, parts irrelevant to the description are omitted, and the same reference numerals are assigned to the same or similar components throughout the specification.

1 is a cross-sectional view of a liquid crystal-based smart window film according to a first embodiment of the present invention. Referring to FIG. 1 , the liquid crystal-based smart window film 100 of the first embodiment includes a liquid crystal layer 10, a first alignment layer 21 and a second alignment layer 22, a first transparent electrode 31 and a second It includes a transparent electrode 32, a polarizing plate 41, and a detector plate 42.

The liquid crystal layer 10 is provided in the cell gap and includes a liquid crystal 11 and a polymer mesh film 12 . The liquid crystal 11 has a function of controlling polarization. The dielectric constant anisotropy (Δε) of the liquid crystal 11 has a positive value and may include a chiral dopant. Δε of the liquid crystal 11 may have a negative value.

For example, the liquid crystal layer 10 includes liquid crystal 11 and a photoreactive material. The photoreactive material includes a first mixture of 70 to 90 wt% of a monomer, 5 to 20 wt% of a crosslinking agent, and 1 to 10 wt% of a photoinitiator. 1 to 30wt% of the first mixed photoreactive material is secondly mixed with 70 to 99wt% of the liquid crystal 11. A final liquid crystal mixture is prepared by mixing 1 to 10 wt% of the spacer 50 capable of maintaining a cell gap with 90 to 99 wt% of the second mixed liquid crystal mixture.

The polymer net film 12 is formed of a monomer that is polymerized by ultraviolet (UV) light. That is, the polymer net film 12 is formed of a monomer for UV curing, and may be formed of one of a polyide-based material and an acrylate material.

The liquid crystal-based smart window film 100 further includes a spacer 50. The spacer 50 is disposed between the first alignment layer 21 and the second alignment layer 22 to set the thickness of the liquid crystal layer 10 . As an example, the spacer 50 may be formed of a polymer in the shape of a ball or column (not shown).

The spacer 50 is fixed to the first alignment layer 21 and the second alignment layer 22 by the polymer mesh 12 to maintain a cell gap. The cell gap is set as a gap between the first alignment layer 21 and the second alignment layer 22 . That is, the spacer 50 minimizes the fluidity of the liquid crystal 11 that may occur due to external pressure (eg, gravity included) on the polarizer 41 and the detector plate 42 . Deterioration of the liquid crystal 11 is improved by minimizing the flow of the liquid crystal 11 in the cell gap. Therefore, it is possible to make a liquid crystal-based smart window film 100 having an improved configuration.

The polymer net film 12 is mixed with the liquid crystal 11 to prepare the smart window film 100, and the polymer net film 12 is formed in the liquid crystal layer 10 by irradiating UV light. Transmittance of the smart window film 100 can be adjusted without light scattering due to the liquid crystal layer 10 .

FIG. 2 is a plan view illustrating polarization axis directions of the polarizer and the detector plate of FIG. 1 and alignment directions of the first alignment layer and the second alignment layer. Referring to FIGS. 1 and 2 , the first alignment layer 21 and the second alignment layer 22 are respectively disposed on a light incident side and a light output side of the liquid crystal layer 10 .

The first alignment layer 21 and the second alignment layer 22 are formed of polymer layers that determine the initial orientation of molecules of the liquid crystal 11 . As an example, the first alignment layer 21 has an alignment direction 211 formed left and right, and the second alignment layer 22 has an alignment direction 221 formed vertically. Alignment directions 211 and 221 of the first and second alignment layers 21 and 22 are orthogonal to each other.

The first transparent electrode 31 and the second transparent electrode 32 are disposed on the first alignment layer 21 and the second alignment layer 22 , respectively. The polarizing plate 41 on the light incident side and the detector plate 42 on the light output side are disposed on the first transparent electrode 31 and the second transparent electrode 32, respectively.

A polarization axis 411 of the polarizer 41 and a polarization axis 421 of the detector 42 are orthogonal to each other. The polarization axis 411 of the polarizing plate 41 is set in the left-right direction, and the polarization axis 421 of the detector plate 42 is set in the up-down direction.

The first alignment layer 21 and the second alignment layer 22 are formed as horizontal alignment layers. The first alignment layer 21 is aligned in the same direction as the polarization axis 411 of the polarizer 41, that is, in the left-right direction, and the pre-tilt angle of the liquid crystal 11 is 1 to 5 degrees. That is, the alignment direction 211 of the first alignment layer 21 and the polarization axis 411 of the polarizer 41 are parallel to each other.

The second alignment layer 22 is oriented in the same direction as the polarization axis 421 of the detector plate 42, that is, in the vertical direction. That is, the alignment direction 221 of the second alignment layer 22 and the polarization axis 421 of the detector plate 42 are parallel to each other.

As an example, the first alignment layer 21 and the second alignment layer 22 may have surface curves and polymer arrangements regularly formed by mechanical friction. In the first alignment layer 21 and the second alignment layer 22 , the mechanical rubbing direction (rubbing method) of the first alignment layer 21 and the mechanical rubbing direction of the second alignment layer 22 may be orthogonal to each other. As another example, the first alignment layer 21 and the second alignment layer 22 may be regularly arranged in a polymer arrangement by polarized UV irradiation (optical alignment method).

Specifically, the alignment layer may be formed on a film on which a transparent electrode is deposited (see FIG. 5) or a polarizing film having a polarization function (see FIGS. 1 and 3). An alignment layer may be formed on the film or polarizing film by coating the film or polarizing film with a solution (PI; Polyimide, PA; Photo Alignment) and then drying. Solution coating methods include spin coating, roll printing, slot die coating, and inkjet printing.

The transparent electrode may be formed of indium tin oxide (ITO) or indium zinc oxide (IZO). The films (71 and 72 in FIG. 5) are polyethylene terephthalate (PET), polycarbonate (PC), tri-acetyl-cellulose (TAC) or cyclo olefin polymer (COP; Cyclo Olefin). Polymer).

Alignment treatment is performed for liquid crystal alignment on the surface of the alignment film. When a polarizing film is used (see FIGS. 1 and 3), alignment treatment is performed in the same direction as the polarization axis.

A sealant is applied to an alignment layer of one substrate on which an alignment-treated one-side alignment layer (first alignment layer in FIG. 1 ) is formed. A liquid crystal mixture is applied to the double layer film on one side to which the sealant is applied. Sealant application is possible by dispensing and screen printing.

Thereafter, a cell is formed by bonding the other side substrate on which the other side alignment film (the second alignment layer in FIG. 1 ) having been subjected to the alignment process is formed. The lamination of the two substrates can be accomplished by One Drop Filling (ODF) or lamination.

At this time, the alignment axes of the two alignment films are 90 degrees from each other. When a polarizing film having a polarizing function is used, the polarization axis (411 in FIG. 1) on one side and the polarization axis (421 in FIG. 1) on the other side are arranged at 90 degrees from each other.

UV is irradiated to form a polymer net film 12 on the laminated cell. Since UV is irradiated, the monomer and crosslinked material of the photoreactive material and the photoinitiator are cured to form the polymer mesh 12 .

When a film having no polarization function is used, a polarizing film having a polarization function is attached to the outer surface of the films on both sides of the laminated cell (71 and 72 in FIG. 5). At this time, the polarization axis of the polarizing film is the same as that of the film having an alignment film.

Referring back to FIG. 1 , a first substrate assembly 101 and a second substrate assembly 102 are disposed on both sides of the liquid crystal layer 10, and the sealant 51 is applied to the first substrate assembly 101 and the second substrate. The assemblies 102 are hermetically bonded to each other. The first substrate assembly 101 includes a first alignment layer 21, a first transparent electrode 31, and a polarizing plate 41, and the second substrate assembly 102 includes a second alignment layer 22 and a second transparent electrode. (32) and the detector plate (42). That is, when the polymer mesh 12 fixes the spacer 50 to the first alignment layer 21 and the second alignment layer 22 to maintain a cell gap, the sealant 51 is applied to the first alignment layer 21 and the second alignment layer 22 . The second alignment layer 22 is mutually sealed. Therefore, the fluidity of the spacer 50 is minimized.

The liquid crystal 11 has a function of controlling polarization and can be controlled in a vertically aligned (VA) liquid crystal mode and a twisted neumatic (TN) liquid crystal mode.

A VA (Vertically Aligned) liquid crystal mode cell is a liquid crystal cell in which liquid crystal molecules are tilted in a direction of 45 degrees to each transmission axis and aligned vertically between two polarizers with vertical transmission axes (FIG. 3 and see Figure 4). The VA liquid crystal cell has the lowest transmittance in the initial state and the transmittance increases as the applied voltage increases.

In a TN (Twisted Nematic) liquid crystal mode cell, liquid crystal molecules are rubbed with each polarizer transmission axis between two polarizers having vertical transmission axes, and are twisted at 90 degrees (see FIGS. 1 and 2). The TN liquid crystal cell has the highest transmittance in the initial state and the transmittance decreases as the applied voltage increases.

Meanwhile, the liquid crystal-based smart window film 100 of the first embodiment is formed by mutually sealing the first substrate assembly 101 and the second substrate assembly 102 . The liquid crystal layer 10 includes a liquid crystal 11 and a polymer mesh film 12 .

The liquid crystal 11 has fluidity between the first and second substrate assemblies 101 and 102 . However, the polymer mesh 12 is fixed to the first substrate assembly 101 and the second substrate assembly 102 to maintain a cell gap by fixing them. The polymer mesh film 12 fixes the liquid crystal 11 and the spacer 50 to the first substrate assembly 101 and the second substrate assembly 102 in the cell gap. Accordingly, the fluidity of the liquid crystal 11 is minimized.

In addition, when lamination is performed using a roller in the process of attaching the liquid crystal-based smart window film 100 to the target glass, the polymer net film 12 separates the liquid crystal 11 and the spacer 50 from the first substrate assembly 101. Since it is fixed to the two-substrate assembly 102, the liquid crystal 11 and the spacer 50 are prevented from being pushed.

Therefore, when the liquid crystal-based smart window film 100 is placed upright, the liquid crystal 11 and the spacer 50 are tilted to the bottom where the liquid crystal 11 and the spacer 50 are erected due to external pressure including gravity, and the non-uniformity of the density of the liquid crystal 11 and the spacer 50 Density unevenness can be minimized. That is, the fluidity of the liquid crystal 11 and the spacer 50 is minimized, and since the cell gap, the density of the liquid crystal 11 and the density of the spacer 50 are kept constant, deterioration can be minimized.

3 is a cross-sectional view of a liquid crystal-based smart window film according to a second embodiment of the present invention. Referring to FIG. 3 , in the liquid crystal-based smart window film 200 of the second embodiment, the first alignment layer 61 and the second alignment layer 62 are formed as vertical alignment layers.

As an example, the first alignment layer 61 has an alignment direction 611 crossing the polarization axis 411 of the polarizing plate 41 in a direction of 45 degrees, and the second alignment layer 62 has a polarization axis 421 of the detector plate 42. ) has an orientation direction 621 intersecting in the 45° direction. Alignment directions 611 and 621 of the first and second alignment layers 61 and 62 are parallel to each other and opposite to each other.

FIG. 4 is a plan view illustrating directions of polarization axes of the polarizer and the detector plate of FIG. 3 and alignment directions of the first alignment layer and the second alignment layer. Referring to FIGS. 3 and 4 , the first alignment layer 61 is aligned in a direction of 45 degrees to the polarization axis 411 of the polarizer 41, and the liquid crystal 16 in the liquid crystal layer 15 is pre-tilted. ) angle is 98~99˚. That is, the alignment direction 611 of the first alignment layer 61 and the polarizer 41 intersect the polarization axis 411 at 45 degrees.

The second alignment layer 62 is oriented in a direction of 45 degrees to the polarization axis 421 of the detector plate 42 . That is, the alignment direction 621 of the second alignment layer 62 and the polarization axis 421 of the detector plate 42 intersect at 45 degrees.

The polymer mesh 17 maintains a cell gap by fixing the first alignment layer 61 on the polarizer 41 side and the second alignment layer 62 on the detector plate 42 side. The polymer mesh film 17 fixes the liquid crystal 16 and the spacer 50 in the cell gap. The polymer mesh film 17 prevents the liquid crystal 16 and the spacer 50 from being pushed.

5 is a cross-sectional view of a liquid crystal-based smart window film according to a third embodiment of the present invention. Referring to FIG. 5 , the liquid crystal-based smart window film 300 of the third embodiment further includes a first substrate 71 and a second substrate 72 .

The first substrate 71 is disposed between the polarizer 41 and the first alignment layer 21, and includes a first transparent electrode 31 as a transparent plastic substrate. The second substrate 72 is disposed between the detector plate 42 and the second alignment layer 22, and includes a second transparent electrode 32 as a transparent plastic substrate.

After the liquid crystal layer 10 is formed between the first substrate 71 and the second substrate 72, the polarizer 41 and the light detector 42 are attached to each other to complete the liquid crystal-based smart window film 300. can

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to these, and it is possible to make various modifications and practice within the scope of the claims, the description of the invention and the accompanying drawings, and this is also the present invention. It goes without saying that it falls within the scope of the invention.

10, 15: liquid crystal layer 11, 16: liquid crystal
12, 17: polymer mesh 21: first alignment layer
22: second alignment layer 31: first transparent electrode
32: second transparent electrode 41: polarizer
42: light inspection plate 50: spacer
61: first alignment layer 62: second alignment layer
100, 200, 300: liquid crystal-based smart window film
101: first substrate assembly 102: second substrate assembly
211, 221: alignment direction 411, 421: polarization axis
611, 621: orientation direction

Claims (14)

a liquid crystal layer provided in the cell gap and including a liquid crystal and a polymer mesh;
a first alignment layer and a second alignment layer disposed on light incident side and light output side of the liquid crystal layer to set the cell gap;
a first transparent electrode and a second transparent electrode disposed on the first alignment layer and the second alignment layer, respectively; and
A polarizing plate and a light detector disposed on the first transparent electrode and the second transparent electrode, respectively.
Including,
The polymer mesh film fixes the liquid crystal to the first alignment layer and the second alignment layer, the liquid crystal-based smart window film. According to claim 1,
The liquid crystal-based smart window film having a positive dielectric anisotropy (Δε) of the liquid crystal and including a chiral dopant. According to claim 1,
The liquid crystal-based smart window film having a negative dielectric constant anisotropy (Δε) of the liquid crystal. According to claim 1,
The polymer net film is formed of a monomer for UV curing, and is a liquid crystal-based smart window film formed of one of a polyide-based material and an acrylate material. According to claim 1,
Further comprising a spacer disposed between the first alignment layer and the second alignment layer to set the thickness of the liquid crystal layer;
The liquid crystal-based smart window film in which the polymer net film fixes the spacer to the first alignment layer and the second alignment layer. According to claim 5,
The spacer is a liquid crystal-based smart window film formed of a ball or columnar polymer. According to claim 1,
The first alignment film and the second alignment film are formed of a polymer film that determines the initial orientation of liquid crystal molecules. According to claim 1,
A liquid crystal-based smart window film wherein a polarization axis of the polarizer and a polarization axis of the detector plate are orthogonal to each other. According to claim 8,
The first alignment layer and the second alignment layer are formed as horizontal alignment layers,
The first alignment layer is oriented in the same direction as the polarization axis of the polarizing plate, and the pre-tilt angle of the liquid crystal is 1 to 5 degrees,
The second alignment film is oriented in the same direction as the polarization axis of the detector plate. According to claim 8,
The first alignment layer and the second alignment layer are formed as vertical alignment layers,
The first alignment layer is oriented in a direction of 45 degrees to the polarization axis of the polarizing plate, and the pre-tilt angle of the liquid crystal is 98 to 99 degrees,
The second alignment film is a liquid crystal-based smart window film aligned in a direction of 45 degrees to the polarization axis of the detector plate. According to claim 7,
The first alignment layer and the second alignment layer are
A liquid crystal-based smart window film in which the curvature of the surface and the arrangement of polymers are regularly formed by mechanical friction. According to claim 11,
A liquid crystal-based smart window film wherein a mechanical rubbing direction of the first alignment layer and a mechanical rubbing direction of the second alignment layer are orthogonal to each other. According to claim 7,
The first alignment layer and the second alignment layer are
A liquid crystal-based smart window film in which polymer arrangements are regularly formed by polarized UV irradiation. According to claim 1,
A first substrate made of a transparent plastic material disposed between the polarizing plate and the first alignment layer and having the first transparent electrode formed thereon; and
The liquid crystal-based smart window film further comprising a second substrate made of a transparent plastic material disposed between the photodetector plate and the second alignment layer and having the second transparent electrode formed thereon.

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