KR20210106264A - A liquid cristal device that can switch between transparent and opaque state - Google Patents

Abstract

According to an embodiment of the present invention, a liquid crystal device comprises: a first substrate and a second substrate opposing to each other and bonded at edges; a first electrode and a second electrode formed inside the first substrate and the second substrate respectively; a liquid crystal layer formed between the first electrode and the second electrode and made of a polymer dispersed liquid crystal material; a vertical alignment film bonded at the liquid crystal layer and vertically aligned; and a horizontal alignment film opposing to the vertical alignment film, bonded at the liquid crystal layer, and horizontally aligned.

Description

Transparent and opaque state transition liquid crystal element {A LIQUID CRISTAL DEVICE THAT CAN SWITCH BETWEEN TRANSPARENT AND OPAQUE STATE}

The present invention relates to a liquid crystal device in which a transparent state and an opaque state are switched. It can be applied to architectural glass or vehicle glass, can be used as a transmittance variable smart window and optical shutter, and can be used as a projection screen when it is opaque. It relates to a liquid crystal device capable of this.

In recent years, the display field for processing and displaying a large amount of information has been rapidly developed in accordance with the information age in which society is full-fledged, and various various flat panel display devices have been developed and spotlighted in response to this.

Specific examples of such a flat panel display device include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an electroluminescence display device. (Electro Luminescence Display device, ELD), Organic Light Emitting Diodes (OLED), etc. are mentioned. These flat panel display devices show excellent performance of thinness, light weight, and low power consumption. CRT) is rapidly being replaced.

Meanwhile, recently, research on a transparent display device that allows a user to see an object or image located on the opposite side through the flat panel display device has been actively conducted due to its characteristics.

For transparent display devices, a state conversion liquid crystal device technology that switches between transparent and opaque states is being researched. Poly Dispersed Liquid Crystal (PDLC: hereinafter referred to as “PDLC”) as a liquid crystal device technology that switches between transparent and opaque states. referred to), and polymer network liquid crystal (Poly Network Liquid Crystal, PNLC: hereinafter referred to as "PNLC") technology.

This state-converted liquid crystal device uses a polymer network liquid crystal for the liquid crystal layer and controls the light transmission and light scattering intensity by the liquid crystal to perform white display that does not require a separate polarizing plate.

On the other hand, PDLC is a structure in which liquid crystal droplets are dispersed in a polymer matrix. If the refractive index in the uniaxial direction of the liquid crystal is designed to be the same as that of the polymer, the liquid crystal is aligned in the electric field direction when a voltage is applied and becomes transparent. When the voltage is turned off, the refractive index of the liquid crystal The refractive indices of the polymer and the polymer are different, so that diffuse reflection occurs at the interface between the liquid crystal drop and the polymer and scatters the light, resulting in an opaque state. These PDLCs are widely used as smart windows and optical shutters, and since they last longer in a transparent state than in an opaque state, the time required to apply a voltage to maintain the transparent state increases, and thus, power consumption is large.

PNLC has the electrical and optical properties of being transparent when no voltage is applied and opaque when voltage is applied. Such PNLC has an advantage of lower power consumption than PDLC, but has a disadvantage in that scattering characteristics are relatively lower than that of PDLC.

Therefore, the state conversion liquid crystal device is required to have the highest transmittance in the transparent state, the maximum scattering in the non-transparent state, and the low voltage applied to maintain the opaque state.

The present invention is to solve the problems of the prior art described above, the state conversion liquid crystal element has the highest transmittance in the transparent state, the maximum scattering in the opaque state, and the voltage applied to maintain the opaque state can be lowered. An object of the present invention is to provide a state-switched liquid crystal device.

The liquid crystal device according to an embodiment of the present invention includes a first substrate and a second substrate having opposite edges, and a first electrode and a second electrode, a first electrode and a second electrode respectively formed inside the first substrate and the second substrate. It includes a liquid crystal layer formed between the electrodes and made of a polymer dispersed liquid crystal material, and a vertical alignment film positioned and vertically aligned with the liquid crystal layer, positioned opposite the vertical alignment layer and bonded to the liquid crystal layer, and horizontally aligned and a planar alignment film.

According to an embodiment of the present invention, the horizontal alignment layer may be a liquid crystal alignment treatment in a concentric circle structure. In addition, according to an embodiment of the present invention, the horizontal alignment layer may be a liquid crystal alignment treatment in a radial structure.

According to an embodiment of the present invention, the first substrate may be made of a light-transmitting glass or a flexible polymer material. In addition, according to an embodiment of the present invention, the second substrate may be made of plastic or a flexible polymer material.

According to an embodiment of the present invention, a sealing agent for preventing the liquid crystal material from flowing between the first substrate and the second substrate may be further included.

According to an embodiment of the present invention, the state conversion liquid crystal device of the present invention has the highest transmittance in the transparent state, the maximum scattering in the opaque state, and the voltage applied to maintain the opaque state can be lowered.

1 is a view schematically showing a transparent and opaque state conversion liquid crystal device according to an embodiment of the present invention.
2 (a) to (b) are diagrams showing schematic diagrams of symmetrically horizontally aligned liquid crystal molecules according to an embodiment of the present invention.
3 (a) to (b) are views showing the cross-sectional state of the liquid crystal element when voltage is applied and when not applied to the transparent opaque state conversion liquid crystal element according to the present invention.
4 (a) to (b) are views showing the state when voltage is applied and when no voltage is applied by aligning the liquid crystal and the polymer in a horizontal state according to an embodiment of the present invention.
5 (a) to (b) are diagrams showing a state when a voltage is applied and when a voltage is not applied by aligning the liquid crystal and the polymer in a vertical state according to an embodiment of the present invention.

Hereinafter, embodiments of the present application will be described in more detail with reference to the accompanying drawings. However, the technology disclosed in the present application is not limited to the embodiments described herein and may be embodied in other forms. However, the embodiments introduced herein are provided so that the disclosed content may be thorough and complete and the spirit of the present application may be sufficiently conveyed to those skilled in the art. In the drawings, in order to clearly express the various layers (or films) and regions, the widths or thicknesses of the layers (or films) and regions are slightly enlarged. In the description of the drawings as a whole, it has been described from an observer's point of view, and when an element is referred to as being positioned on another element or substrate, this means that the element may be positioned directly on another element or substrate, or an additional element may be interposed between those elements. includes all meanings. In addition, those skilled in the art will be able to implement the idea of the present application in various other forms without departing from the technical spirit of the present application. And, like reference numerals on a plurality of drawings refer to substantially the same elements.

Transparent and opaque state transition liquid crystal element

1 is a view schematically showing a transparent and opaque state conversion liquid crystal device according to an embodiment of the present invention.

Referring to FIG. 1 , a liquid crystal device capable of switching between transparent and opaque states according to an embodiment of the present invention includes a first substrate 110 , a first electrode 130 , a vertical alignment layer 150 , a liquid crystal layer 170 , It includes a horizontal alignment layer 160 , a second electrode 140 , and a second substrate 120 .

First, the first electrode 130 and the second electrode 140 for supplying an electrical signal are positioned between the first substrate 110 and the second substrate 120 according to an embodiment of the present invention, and between the two electrodes The liquid crystal layer 170 is provided so that the arrangement of the liquid crystal is changed according to an electrical signal. In addition, a vertical alignment layer 150 and a horizontal alignment layer 160 are further included between the first electrode 130 and the second electrode 140 to determine the initial arrangement of the liquid crystal layer 170 .

Meanwhile, the first substrate 110 may be made of transparent glass or a flexible polymer material. For example, the flexible polymer may be polyimide, polyester sulfone, polyethylene terephthalate, or polystyrene. In addition, the first substrate 110 may be a glass substrate having a thickness of 1000 um to 7000 um or a flexible polymer substrate having a thickness of 50 um to 1000 um, depending on the implementation. The first substrate 110 serves to transmit light incident from the outside and light reflected from the reflective layer.

In addition, the second substrate 120 may be made of plastic or a flexible polymer material. Here, the flexible polymer material may be polyimide, polyester sulfone, polyethylene terephthalate, polystyrene, or the like, like the first substrate 110 .

The sealing agent 180 serves as an adhesive to the edge of the first substrate 110 or the second substrate 120 and serves to bond the first substrate 110 and the second substrate 120 to each other. .

The first electrode 130 and the second electrode 140 are made of a transparent conductive material, and may serve to transmit reflected light. Also, the first electrode 130 and the second electrode 140 may be formed of indium tin oxide (ITO) or indium zinc oxide (IZO). In addition, depending on the implementation, the first electrode 130 and the second electrode 140 may be formed to a thickness of 10 to 200 nm, and may be formed by depositing a transparent conductive material and then patterning it using a photolithography technique. can

The liquid crystal layer 170 according to an embodiment of the present invention is made of a polymer liquid crystal material, and the polymer used as the liquid crystal material is polystyrene, polyethylene, polyurethane, polychloride. Transparent polymers such as vinyl (Poly chloride Vinyl), polymethyl methacrylate (Poly Methyl Methane Acrylate), polycarbonate epoxy resin (Poly Carbonate Epoxy Resin), and polyvinyl acrylate (Poly Vinyl Acrylate) are mostly used. In addition, the liquid crystal is aligned in the direction of the electric field, and transparent and opaque states may be switched by the vertical alignment layer 150 , which is aligned in the vertical direction, and the horizontal alignment layer 160 , which is aligned in the horizontal direction. In addition, a hollow polymer ball can be produced by foaming the polymer. Methods for releasing the polymer include a method using mechanical stirring, a method using a reaction product gas, a method using a foaming agent, a method by spraying, and the like.

On the other hand, the vertical alignment layer 150 according to an embodiment of the present invention is positioned to be bonded to the liquid crystal layer 170 and has a property of vertically arranging the liquid crystal with respect to the first substrate 110 or the second substrate 120 . , as long as it is a material having such properties, it may be used without any particular limitation, and representatively, polyimide, lecithin, SiOx, or the like may be used.

The horizontal alignment layer 160 has a property of arranging the liquid crystal horizontally with respect to the first substrate 110 or the second substrate 120, and any material having such a property may be used without any particular limitation. Mid (polyimide), polystyrene (polystyrene), nylon (nylon), or a photo-aligning agent may be used.

In the case of the vertical alignment layer 150 and the horizontal alignment layer 160 according to an embodiment of the present invention, they are disposed in contact with the liquid crystal, and the vertical alignment layer 150 may be located adjacent to the first substrate 110 and the second substrate It can also be located close to each other. Also, the horizontal alignment layer 160 may be positioned adjacent to the first substrate 110 and adjacent to the second substrate 120 . In other words, the vertical alignment layer 150 may be located on the upper plate or the lower plate, and the horizontal alignment layer 160 may be located on the upper plate or the lower plate. In addition, the positions of the vertical alignment layer 150 and the horizontal alignment layer 160 are not particularly limited, but it is preferable to form one side of the vertical alignment layer 150 and the other side of the horizontal alignment layer 160 .

2 is a view showing a schematic diagram of liquid crystal molecules aligned in a horizontal direction according to an embodiment of the present invention. Figure 2 (a) is a view showing a liquid crystal alignment treatment that is a concentric structure in the horizontal direction according to an embodiment of the present invention, Figure 2 (b) is a horizontal direction according to an embodiment of the present invention It is a view showing a liquid crystal cell with a liquid crystal alignment treatment, which is a radial structure of

Referring to FIG. 2A , the horizontal alignment layer 160 according to an embodiment of the present invention may be manufactured in the form of concentric circles in which a plurality of polymer balls are dispersed. Also, referring to FIG. 2B , the horizontal alignment layer 160 according to an embodiment of the present invention may be manufactured in a radial shape in which a plurality of polymer balls are dispersed. This shape has the effect of increasing the scattering effect by making the liquid crystal molecules lie in a more random direction in the liquid crystal domain by making them symmetric in the plane. In addition, this method has the effect of reducing the driving voltage. Compared to the case of a vertically oriented liquid crystal cell, the upper and lower plates are oriented in a vertical direction and the other in a horizontal direction. Because there is a rotating interaction.

On the other hand, a method of aligning liquid crystal molecules in a concentric circle or a radial shape can be implemented by a photo-alignment method. Here, the photo-alignment method is a method of using a photo-alignment film in which polymer facts are aligned in a certain direction by polarized UV, and when polarized UV is irradiated, the alignment direction of liquid crystal molecules can be controlled as desired for each position. In addition, the vertical alignment layer 150 or the horizontal alignment layer 160 may be used after a rubbing treatment, through which the alignment of the liquid crystal can be adjusted. However, it is not necessary to undergo a rubbing treatment, and other alignment methods such as photo-alignment and nano-groove patterning may be used.

3 (a) to (b) is a view showing a cross-sectional state of the liquid crystal element when the voltage is applied and not applied to the transparent opaque state conversion liquid crystal element according to the present invention.

Figure 3 (a) is a view showing the state of the liquid crystal when no voltage is applied to the transparent opaque state conversion liquid crystal device according to the present invention.

Referring to (a) of FIG. 3 , when no voltage is applied, the liquid crystal cell is aligned so that the liquid crystal is aligned in a vertical or horizontal state. At this time, since the polymer network affects the rotation of liquid crystal molecules, it is preferable to make the average arrangement state as random as possible in order to maximize scattering.

On the other hand, Figure 3 (b) is a view showing the state of the liquid crystal when a voltage is applied to the transparent opaque state conversion liquid crystal device according to the present invention.

Referring to FIG. 3B , when a voltage is applied to the transparent opaque state conversion liquid crystal device according to an embodiment of the present invention, the horizontally aligned liquid crystal can be rotated by other liquid crystals. Also, the vertically aligned liquid crystal can be rotated by other liquid crystals.

On the other hand, the polymer network formed in the liquid crystal of the liquid crystal is anisotropic and may affect the orientation of the liquid crystal. In addition, it has the characteristic of trying to align the liquid crystal in the direction of the fibers.

4 (a) to (b) are diagrams showing a state when a voltage is applied and when a voltage is not applied by aligning the liquid crystal and the polymer in a horizontal state according to an embodiment of the present invention.

Figure 4 (a) shows the structure of the liquid crystal and polymer network when no voltage is applied to the entire cell. Referring to (a) of FIG. 4 , when there is no voltage applied to the entire cell, the liquid crystal and the polymer network are uniformly aligned in the x direction. When light passes through the material, it encounters the same refractive index in the liquid crystal and polymer regions, and passes through the material without scattering.

Figure 4 (b) shows the structure of the liquid crystal and polymer network when a voltage is applied to the entire cell. Referring to (b) of FIG. 4 , when a voltage is applied, the liquid crystal is aligned due to the voltage applied across the battery, and the polymer network has a characteristic of trying to maintain the liquid crystal in the x direction.

5 (a) to (b) are views showing the state when the voltage is applied and when no voltage is applied by aligning the liquid crystal and the polymer in a vertical state according to an embodiment of the present invention.

Referring to (a) to (b) of FIG. 5 , when liquid crystal and polymer are aligned in a vertical state and an electric field is applied, the liquid crystal molecules are tilted away from the field direction due to negative dielectric anisotropy. As shown in (b) of FIG. 5 , when the liquid crystal molecules are tilted, they are tilted in the x-direction in some regions, but in the y-direction in other regions. Accordingly, light polarized in the x-direction and the y-direction may be scattered.

In this way, the polymer network can bring about the effect of improving the performance of the driving voltage and response time of the existing liquid crystal device, and can bring about the effect of reducing the driving voltage.

In the above, preferred embodiments of the present invention have been described with reference to the accompanying drawings, but those of ordinary skill in the art to which the present invention pertains will implement the present invention in other specific forms without changing the technical spirit or essential features. You will understand that it can be Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive.

10: liquid crystal element
110: first substrate
120: second substrate
130: first electrode
140: second electrode
150: vertical alignment layer
160: horizontal alignment layer
170: liquid crystal layer
180: seal

Claims (6)

In the liquid crystal device,
A first substrate and a second substrate having opposite edges bonded to each other;
first and second electrodes respectively formed in the first and second substrates;
A liquid crystal layer formed between the first electrode and the second electrode and made of a polymer dispersed liquid crystal material, and
It includes a vertical alignment film positioned by bonding with the liquid crystal layer and subjected to vertical alignment treatment,
A transparent opaque state conversion liquid crystal device, which is positioned opposite to the vertical alignment layer and adheres to the liquid crystal layer, and includes a horizontal alignment layer that is horizontally aligned. According to claim 1,
The horizontal alignment layer is a transparent opaque state conversion liquid crystal device in which the liquid crystal alignment process is performed in a concentric circle structure. According to claim 1,
The horizontal alignment layer is a transparent opaque state conversion liquid crystal device in which liquid crystal alignment treatment is performed in a radial structure. According to claim 1,
The first substrate is a transparent opaque state conversion liquid crystal device made of a translucent glass or a flexible polymer material. According to claim 1,
The second substrate is a transparent opaque state conversion liquid crystal device made of a plastic or flexible polymer material. According to claim 1,
Transparent opaque state conversion liquid crystal device further comprising a sealing agent for preventing the liquid crystal material from flowing between the first substrate and the second substrate.

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