阅读说明：本技术 具有非均匀取向层的无雾反向液晶光控膜 (Haze-free inverse liquid crystal light control film with non-uniform alignment layer ) 是由 郑文俊 蒙翠玲 邓树端 郭海成 于 2018-06-01 设计创作，主要内容包括：本发明提供一种与电动可切换光控器件相关的器件和方法。器件包括两块透明导电基板(10),两个非均匀取向层(20),各自涂覆在各自的透明基板(10)上,在所述两块透明基板(10)之间的间隔垫片(30),在所述两块透明基板(10)之间的液晶层；以及在所述液晶层内部的聚合物网络(40)。该器件可用于智能窗户、触摸屏或隐私窗户。(The present invention provides a device and method relating to an electrically switchable light control device. The device comprises two transparent conductive substrates (10), two non-uniform orientation layers (20) respectively coated on the respective transparent substrates (10), a spacer (30) between the two transparent substrates (10), and a liquid crystal layer between the two transparent substrates (10); and a polymer network (40) inside the liquid crystal layer. The device can be used for smart windows, touch screens or privacy windows.)

1. An electrically switchable light control device comprising:

two transparent conductive substrates;

the two non-uniform orientation layers are respectively coated on the two transparent conductive substrates;

the spacing gasket is arranged between the two transparent conductive substrates;

the liquid crystal layer is arranged between the two transparent conductive substrates; and

a polymer network disposed inside the liquid crystal layer.

2. The device of claim 1, wherein the two transparent conductive substrates comprise glass having an indium tin oxide layer thereon or a polyethylene terephthalate (PET) film having an indium tin oxide layer thereon.

3. The device of claim 1, wherein the spacer comprises a glass sheet, a plastic rod, beads, or a resin or polymer based structure.

4. The device of claim 1, wherein each of said two non-uniformly oriented layers comprises a different region comprising a different respective material and/or a different region comprising a different respective topography.

5. The device of claim 1, wherein the two non-uniformly oriented layers comprise vertically or horizontally oriented material and reactive mesogens, monomers, or sub-micron particles.

6. The device of claim 1, wherein at least one of the two non-uniformly oriented layers is a randomly oriented layer or a multi-directionally oriented layer.

7. The device of claim 1, wherein the two transparent conductive substrates are coated with an anti-reflective coating, an ultraviolet-protective coating, or an infrared-protective coating, respectively.

8. The device of claim 1, wherein the liquid crystal layer comprises a negative dielectric liquid crystal.

9. The device of claim 1, wherein the liquid crystal layer includes a dichroic dye.

10. The device of claim 1, wherein the at least one transparent conductive substrate comprises an active matrix Thin Film Transistor (TFT).

11. The device of claim 1, wherein a transparent conductive layer of the two transparent conductive layers is patterned such that a respective portion of the electrically switchable light control device can be in a voltage on state or a voltage off state.

12. A smart glass device comprising:

two pieces of glass coated with low emissivity coatings respectively;

two transparent conductive substrates arranged between the two pieces of glass;

two non-uniform orientation layers respectively coated on the two transparent conductive substrates;

the spacing gasket is arranged between the two transparent conductive substrates;

the liquid crystal layer is arranged between the two transparent conductive substrates; and

a polymer network disposed inside the liquid crystal layer.

13. A method of making an electrically switchable light control device, comprising:

providing two transparent conductive substrates;

coating a non-uniform orientation layer on a corresponding surface of each of the two transparent conductive substrates;

arranging a spacing gasket between the corresponding coating surfaces of the two transparent conductive substrates;

arranging a liquid crystal layer between the corresponding coating surfaces of the two transparent conductive substrates; and

a polymer network is disposed within the liquid crystal layer.

14. The method of claim 13, wherein disposing a spacer between the respective coated surfaces of the two transparent conductive substrates comprises:

and photoetching, screen printing or photopolymerizing the spacing gasket to at least one transparent conductive substrate in the two transparent conductive substrates.

15. The method of claim 13, wherein applying a non-uniform alignment layer on a respective surface of each of the two transparent conductive substrates comprises:

adding reactive mesogens, monomers, or sub-micron particles to a vertically or horizontally oriented material to form a mixture;

coating the mixture on the respective surfaces of the two transparent conductive substrates; and

curing the mixture with heat or light to form the non-uniform alignment layer.

16. The method of claim 13, wherein applying a non-uniform alignment layer on a respective surface of each of the two transparent conductive substrates comprises:

coating vertically or horizontally oriented material on the respective surfaces of the two transparent conductive substrates; and

a reactive mesogen or monomer is coated on the vertically or horizontally oriented material.

17. The method of claim 13, wherein applying a non-uniform alignment layer on a respective surface of each of the two transparent conductive substrates comprises:

coating reactive mesogens or monomers on the respective surfaces of the two transparent conductive substrates;

a vertically or horizontally oriented material is coated on the reactive mesogen or monomer.

18. The method of claim 13, wherein applying a non-uniform alignment layer on a respective surface of each of the two transparent conductive substrates comprises:

coating reactive mesogens, monomers or sub-micron particles on the respective surfaces of the two transparent conductive substrates.

19. The method of claim 13, wherein applying a non-uniform alignment layer on a respective surface of each of the two transparent conductive substrates comprises:

directly coating vertical or horizontal orientation materials on the corresponding surfaces of the two transparent conductive substrates without adding additional monomers or polymers,

wherein the respective surfaces of each of the two transparent conductive substrates have a non-uniform topography.

20. The method of claim 13, further comprising polymerizing the reactive mesogen or monomer by heating or Ultraviolet (UV) irradiation.

21. The method of claim 13, further comprising:

patterning at least one of the two transparent conductive substrates such that a respective portion of the electrically switchable light control device may be in a voltage on state or a voltage off state.

Technical Field

The present invention relates to a light control device using light scattering.

Background

Commercially available electrically switchable windows may be divided into liquid crystal and non-liquid crystal categories. Non-liquid crystals include Electrochromic (EC) windows and Suspended Particle Device (SPD) windows. However, EC and SPD windows, while suitable standard windows, are not suitable for privacy windows due to long switching times and light leakage.

On the other hand, liquid crystal based smart windows, such as Polymer Dispersed Liquid Crystal (PDLC) devices, can switch from a voltage-on transparent state to a voltage-off scattering (diffusive) state within milliseconds. Light waves are scattered by the device rather than absorbed. PDLC devices are suitable for privacy windows but do not block light from entering the room and are therefore not preferred for standard windows.

Disclosure of Invention

Embodiments of the present invention provide a reverse light control device having a voltage off transparent state and a voltage on opaque state. In one embodiment of the invention, a polymer may be added to the liquid crystal to form a polymer network impregnated with the liquid crystal. This may be referred to as a Polymer Network Liquid Crystal (PNLC) structure or a Polymer Stabilized Liquid Crystal (PSLC) device. A vertical surface alignment layer may be applied to align the liquid crystal molecules in a vertical direction in a voltage off state.

A negative type liquid crystal having a negative dielectric anisotropy may be employed such that when it is subjected to a vertical electric field, the liquid crystal molecules are aligned perpendicular to the electric field. A polymer network with a refractive index close to that of the liquid crystal can be used to minimize light scattering at all viewing angles in the voltage off state. The matched refractive index does not vary with the viewing angle, and thus a wide haze-free viewing angle can be obtained.

In another embodiment, the polymer structure may be embedded in a liquid crystal alignment material to form a non-uniform alignment layer. The non-uniform alignment layer aligns the liquid crystal vertically in a voltage-off state and promotes randomness of the alignment of the liquid crystal in a voltage-on state.

When the applied voltage exceeds the threshold voltage, the negative-type liquid crystal molecules start to deviate from the position of vertical alignment. Due to the presence of the non-uniformly oriented surface and the polymer network, a number of randomly oriented LC domains are formed and enter the scattering state. The scattering increases as the voltage increases and eventually reaches a maximum level. However, if too much voltage is applied, scattering may begin to decrease. When the applied voltage is switched off, the liquid crystal returns to the original vertical orientation and the device is transparent again.

Instead of using homeotropic alignment materials, non-uniform alignment layers, polymer network liquid crystals and horizontally (planar) aligned liquid crystals with positive dielectric anisotropy can also be used to create the reverse operation.

Embodiments of the present invention may be used in smart windows, transparent displays, windows outside buildings, and indoor privacy windows. These windows and displays may be used in buildings, conference rooms, hotel rooms, and possibly as vehicle windows.

Drawings

FIG. 1 is a schematic diagram of a reverse Polymer Network Liquid Crystal (PNLC) device.

Figure 2 shows an atomic force microscope image of a non-uniform surface alignment layer.

Fig. 3 shows the line profile of the non-uniform layer.

FIG. 4 is a schematic view showing the alignment of liquid crystals in the vicinity of a non-uniform alignment layer.

Fig. 5 is a schematic diagram showing the device in a voltage off state.

Fig. 6 is a schematic diagram showing the device in the voltage-on state.

Fig. 7 is a graph of transmittance voltage curves for the present invention.

Fig. 8 is a schematic diagram showing the liquid crystal plane alignment in a voltage-off state when a positive dielectric anisotropy liquid crystal is used.

Fig. 9 is a schematic diagram showing the alignment of positive liquid crystals in a voltage-on state.

Fig. 10 is a schematic diagram illustrating a device incorporating the use of dichroic dyes in a voltage off state.

Fig. 11 is a schematic diagram illustrating a device incorporating the use of dichroic dyes in the voltage on state.

Fig. 12 shows three diagrams illustrating three possible switchable window configurations.

Fig. 13 shows two diagrams illustrating a patterned switchable window.

Detailed Description

The disclosure and exemplary embodiments presented below enable one of ordinary skill in the art to make and use electrically switchable light control devices in accordance with the present invention. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the generic principles herein may be applied to other embodiments. Thus, the devices and methods related to electrically switchable light control devices are not intended to be limited to the embodiments shown, but are to be accorded the widest scope consistent with the principles and features described herein.

As shown in fig. 1, each substrate 10 is connected to a respective non-uniform alignment layer 20. The distance between the two substrates is determined by the spacer 30 between the top and bottom substrates 10. The top and bottom substrates 10 may be transparent conductive electrodes. In one embodiment, the top and bottom substrates 10 comprise Indium Tin Oxide (ITO) on glass, indium tin oxide on polyethylene terephthalate (PET) film, or other transparent conductive coatings on glass or plastic substrates. The space between the two substrates 10 is filled with liquid crystals in the polymer network 40.

Spacer 30 may be made of glass, plastic rods or beads dispersed in a liquid crystal polymer composite. Spacer 30 may be a built-in structure such as a cylinder, bump or wall on a transparent conductive substrate and may be fabricated by photolithography, screen printing or photopolymerization.

If the substrate is made of a flexible plastic, the device may be sandwiched between the glass of a building or privacy window. In addition, the glass substrate or the outer glass (for plastic substrates) may have other functional coatings, such as an antireflective coating, an Ultraviolet (UV) protective coating, or an Infrared (IR) protective coating.

In one embodiment, the alignment layer is made of a vertical alignment material to which reactive mesogens are added. The vertical alignment material functions to align the liquid crystal in a vertical direction during a voltage off state. The addition of reactive mesogens creates a non-uniform rough surface. The polymerization of the reactive mesogen forms local irregularities (local irregularities) on the alignment layer 20, as shown in fig. 2. Fig. 2 shows the non-uniform surface alignment layer 20 having a cross-sectional depth of about 100 nm and a domain size (micrometer) in the micrometer range (see also fig. 3).

The effect of the non-uniform surface is to give the vertically aligned liquid crystal molecules a small polar angle and random azimuthal angle. Another function of the non-uniform surface is to promote the formation of a polymer network on the substrate surface, thereby enhancing the adhesion between the substrates. In one embodiment, the homeotropic layer material may be SE-4811 homeotropic material from Nissan Chemical Industries and the reactive mesogen may be UCL 017 from DIC. Fig. 4 shows the liquid crystal alignment 50 in the vicinity of the non-uniform alignment layer 20.

In one embodiment, the non-uniformly oriented surface may be a monolayer formed by mixing an oriented material with a reactive mesogen in a uniform solution. The solution may then be coated on the top and bottom substrates, and then the reactive mesogens may be cured to form a non-uniform surface on each of the individual substrates.

In another embodiment, the non-uniformly oriented surface is formed of two layers, first coating a vertical alignment layer on each respective top and bottom substrate, and then coating a reactive mesogen layer on each respective vertical alignment layer. In yet another embodiment, a reactive mesogen layer may be coated on each respective top and bottom substrate, and then a vertical alignment layer is coated on each respective reactive mesogen layer. In each embodiment, the amount of reactive mesogen used and the curing conditions directly affect the non-uniformity and morphology of the non-uniform alignment layer.

In another embodiment, the non-uniform alignment layer may be formed by adding monomers or small particles; or directly applying an alignment layer on the surface of the roughened transparent conductive layer without using additional monomers or polymers. In yet another embodiment, the non-uniformly oriented layer may form a surface layer that is randomly oriented or multi-directionally oriented.

In one embodiment, the liquid crystal and the monomer may be filled between two transparent conductive substrates. The liquid crystal to monomer weight ratio may be less than in conventional Polymer Dispersed Liquid Crystal (PDLC) devices. In one embodiment, the weight of the monomer is less than 10% of the weight of the liquid crystal. The liquid crystal and monomer mixture can be cured under appropriate conditions and form a polymer network, as shown in fig. 5. In one embodiment, the monomer used is UCL 017 from DIC. The liquid crystal may be a refractive index matched negative column phase liquid crystal. Small amounts of photoinitiator may also be added to promote polymerization of the monomers.

As shown in fig. 5, the liquid crystals 50 are vertically aligned, forming a polymer network between the top and bottom substrates 10. Each substrate 10 is coated with a respective non-uniform alignment layer 20. Voltage source 60 is not on and the device is in a voltage off transparent state, thus allowing light waves 70 to pass through the device with minimal scattering. Polymers may be selected that have a refractive index that matches the refractive index of the liquid crystal.

When a voltage is applied by the voltage source 60, an electric field is generated. When the liquid crystal 50 has negative dielectric anisotropy, the liquid crystal 50 is horizontally rotated to be aligned with a vertical electric field, as shown in fig. 6. Light waves 80 passing through the randomly oriented liquid crystal domains show enhanced scattering due to the rotation of the liquid crystals 50.

The liquid crystals that are not near the non-uniformly oriented surface or the polymer network turn first to the horizontal position. The liquid crystal near the non-uniformly aligned surface resists rotation due to the anchoring force that resists the rotation of the molecules. In addition, the random surface non-uniformity gives the liquid crystal molecules random azimuthal angles. The polymer network also hinders the rotation of the liquid crystal molecules. As a result, small liquid crystal domains having different liquid crystal directions are formed. When a voltage is applied, liquid crystal domain scattering and liquid crystal-polymer network scattering occur. When the voltage increases beyond a certain level, the device reaches a diffused state. Fig. 7 shows a typical light transmission voltage curve. Light passes through the device at a constant transmittance until the applied voltage begins to approach 5V, at which time the percentage of light passing through the device drops sharply. The curves in fig. 7 also show that the device can operate at low voltage levels.

In another embodiment, no homeotropic alignment material is used to align the liquid crystal molecules. The liquid crystal 90 having positive dielectric anisotropy is oriented in a horizontal or planar manner in a voltage-off transparent state, as shown in fig. 8. When the voltage source 60 generates a voltage, a vertical electric field is generated. The liquid crystal rotates to be parallel to the electric field. Due to surface inhomogeneities and the polymer network, liquid crystal domains are formed and the light wave 100 passing through the device shows enhanced scattering, as shown in fig. 9.

In another embodiment, a dichroic dye is added to the negative dielectric liquid crystal polymer network layer. In one embodiment, the dichroic dye used is black dye S428 from Mitsui Fine Chemicals. The dichroic dye molecules have an elongated shape and follow the alignment direction of the adjacent liquid crystal molecules. Dichroic dyes absorb light along the long axis of each dye molecule, but allow light waves to travel in the vertical direction to pass through. In the voltage off state, normally incident light can pass through the device without being significantly absorbed.

As shown in fig. 10, when the device is in the voltage off state, the dichroic dye molecules 110 are oriented vertically and do not absorb light passing through the device. However, the dichroic dye 110 does absorb some of the light waves that pass through the device at oblique angles. Complete absorption of the light wave is not achieved by a single dye molecule 110, but by multiple absorptions by many dye molecules. As shown in fig. 11, when a voltage is generated from the voltage source 60, the randomly oriented liquid crystal domains with the dichroic dye 110 absorb light waves 120 from all incident angles, and thus the device is in an opaque dark state.

The reverse polymer network non-uniform surface liquid crystal light control device is well suited for smart glass, touch screen or privacy window applications. As shown in fig. 12, the smart glass or privacy window may be in a transparent voltage off state 130, an opaque scattering state 140 with diffuse light passing through, and an opaque absorbing state 150 with minimal light penetration. Devices employing dichroic dyes can be used for windows where light transmission control is desired. It is also well suited for transparent displays that do not require a truly dark state.

The transparent conductive layer may be an active matrix thin film transistor for pixel-by-pixel driving or may be combined with an active matrix device to become an active matrix driven smart display. In one embodiment, the device may be positioned between two sheets of glass, each sheet of glass coated with a low emissivity coating. In another embodiment, as shown in fig. 13, a simple text or clock pattern 160, 170 may be formed on the substrate. In the upper right corner, the pattern area may display a diffuse pattern (voltage on) 160 and a transparent background (voltage off) 170. This can be used for viewfinder display applications.

The invention as shown herein and the specific aspects or embodiments illustrated or the materials used in the examples are not meant to be limiting but may include variations, modifications or adaptations associated with the principles of the invention. As previously mentioned, all the figures shown are not drawn to scale nor are they exact copies of real devices.

All patents, patent applications, provisional applications, and publications mentioned or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent they are not inconsistent with the explicit teachings of this specification.

It is understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and scope of the appended claims. Furthermore, any element, any inventive limitation, or embodiments thereof disclosed herein may be combined with any and/or all other elements or limitations disclosed herein (alone or in any combination), or any other invention or embodiments thereof, and all such combinations are within the scope of the present invention, but are not limited thereto.