KR20170001396A - Liquid crystal cell - Google Patents

Abstract

The present application relates to a liquid crystal cell and a use thereof. The exemplary liquid crystal cell can implement a bistable mode switching between a haze mode and a transmissive mode, or between a non-haze mode and a transmissive mode with only a low driving voltage and temperature. Such a liquid crystal cell can be applied to various optical modulation devices such as a smart window, a window protective film, a flexible display device, an active retarder for 3D image display, or a viewing angle adjusting film.

Description

Liquid crystal cell {LIQUID CRYSTAL CELL}

The present application relates to a liquid crystal cell and a use thereof.

The liquid crystal mode can be classified into a monostable mode and a bistable mode according to a stable state. The monostable mode is a mode in which application of external energy is continuously required to maintain at least one state of the liquid crystal, and the bistable mode is a mode in which external energy is required only at a state change.

Patent Document 1 discloses a bistable mode liquid crystal cell capable of switching between a haze mode and a non-haze mode.

U.S. Published Patent Application No. 2006-0091538

The present application provides liquid crystal cells and uses thereof.

The liquid crystal cell includes two substrates arranged opposite to each other; A liquid crystal layer disposed between the two substrates and including a liquid crystal compound; An electrode unit for applying a voltage to the liquid crystal layer; And a heat generating unit for applying heat to the liquid crystal layer.

 A liquid crystal layer may be present between the two oppositely disposed substrates. The liquid crystal layer may also include a liquid crystal compound. The liquid crystal compound may be a liquid crystal compound showing a smectic liquid crystal phase (hereinafter, referred to as a smectic liquid crystal compound). In the present specification, the smectic liquid crystal phase may mean a liquid crystal phase having a property that the director of the liquid crystal compound aligns in a predetermined direction and the liquid crystal compound is arranged while forming a layer or a plane. Such a liquid crystal cell can realize a bistable mode capable of switching between a transmissive mode and a haze mode and between a transmissive mode and a non-hazy mode even at a low driving voltage and a driving temperature.

As the liquid crystal compound, any liquid crystal compound capable of exhibiting a smectic phase can be used without any particular limitation. Such smectic liquid crystal compounds can be classified into smectic A-phase to H-phase liquid crystalline compounds according to the orientation method, and they can be selected and used without limitation. As the smectic liquid crystal compound, for example, a liquid crystal compound capable of exhibiting a smectic A phase (hereinafter referred to as Smectic A liquid crystal compound) can be used. In this specification, the Smectic A phase may refer to a liquid crystal phase in which the aligned liquid crystal compound in the Smectic liquid crystal phase is oriented perpendicular to the Smectic layer or plane. As the smectic liquid crystal compound, besides the smectic A liquid crystal compound, the above-mentioned other kind of smectic liquid crystal compound can also be used, and if necessary, it can be used together with a suitable alignment film as described later.

As the smectic liquid crystal compound, for example, a liquid crystal compound represented by the following formula (1) can be used.

[Chemical Formula 1]

Wherein A is a single bond, -COO- or -OCO-, and R ₁ to R ₁₀ are each independently selected from the group consisting of hydrogen, a halogen, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a cyano group, to be.

(2)

In formula (2), B is a single bond, -COO- or -OCO-, and R ₁₁ to R ₁₅ are each independently hydrogen, halogen, alkyl group, alkoxy group, alkoxycarbonyl group, cyano group or nitro group.

In the formula (2), "-" on the left side of B may mean that B is directly connected to benzene of the formula (1).

In the formulas (1) and (2), the term " single bond " means a case where no separate atom is present in a portion represented by A or B; For example, when A is a single bond in formula (2), benzene on both sides of A may be directly connected to form a biphenyl structure.

Examples of the halogen in the formulas (1) and (2) include, for example, chlorine, bromine, iodine and the like.

Unless otherwise specified, the term "alkyl group" in the present application means, for example, a linear or branched alkyl group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, , Or may mean, for example, a cycloalkyl group having 3 to 20 carbon atoms, 3 to 16 carbon atoms, or 4 to 12 carbon atoms. The alkyl group may be optionally substituted with one or more substituents.

The term "alkoxy group" in the present application means, for example, an alkoxy group having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms or 1 to 4 carbon atoms unless otherwise specified . The alkoxy group may be linear, branched or cyclic. In addition, the alkoxy group may be optionally substituted with one or more substituents.

Examples of the substituent which may be substituted in the specific functional group in the present invention include an alkyl group, an alkoxy group, an alkenyl group, an epoxy group, an oxo group, an oxetanyl group, a thiol group, a cyano group, a carboxyl group, May be exemplified, but the present invention is not limited thereto.

In the general formulas (1) and (2), any one of R ₁ to R ₁₅ may be an alkyl group, an alkoxy group or an alkoxycarbonyl group having 5 or more carbon atoms, 6 or more, 7 or more, 8 or more, 9 or more or 10 or more carbon atoms. Such a liquid crystal compound can exhibit a smectic phase while being arranged in a typical layer shape, for example, between a temperature lower than a temperature at which the nematic phase is exhibited and a temperature at which it is solidified. Examples of such liquid crystal compounds include 4-cyano-4'-heptylbiphenyl, 4-cyano-4'-heptyloxybiphenyl, 4-cyano- 4'-decylbiphenyl, 4-cyano-4'-nonylbiphenyl, 4-cyano-4'-nonyloxybiphenyl, 4-cyano- -Decyloxybiphenyl, and the like, but are not limited thereto. As a specific example, HJA1512000-000 of HCCH may be used as the liquid crystal compound, but the present invention is not limited thereto.

Smectic liquid crystal compounds can be interconverted in an irregularly arranged state and in a vertically aligned state or a horizontally aligned state. The irregularly arranged state may mean that the liquid crystal compound is irregularly arranged, and the vertical or horizontal alignment state may be a state in which the liquid crystal layer is vertically or horizontally aligned in the liquid crystal layer depending on the characteristics of the smectic liquid crystal compound It can mean.

As used herein, the term " vertical alignment " means that the optical axis of the liquid crystal compound is in the range of about 90 to 65 degrees, about 90 to 75 degrees, about 90 to 80 degrees, about 90 to 85 degrees, Quot; horizontal alignment " means that the optical axis of the liquid crystal compound is in the range of about 0 to 25 degrees, about 0 to 15 degrees, about 0 to 10 degrees, about 0 degrees To about 5 degrees or about 0 degrees. The term " optical axis " in this specification means an axis in the long axis direction of the liquid crystal compound when the liquid crystal compound is a rod shape, and an axis in the normal direction of a plane when the liquid crystal compound is a discotic shape.

The liquid crystal compound may have a positive dielectric anisotropy or a negative dielectric anisotropy. In this specification, "a dielectric anisotropy" can mean the difference between the above dielectric constant (ε _e, extraordinary dielectric anisotropy, the long axis direction of the dielectric constant) and the normal dielectric constant (ε _o, ordinary dielectric anisotropy, the dielectric constant in the minor axis direction) of the liquid crystal compound. As described later, a vertical electric field can be appropriately applied for alignment according to the dielectric anisotropy of the liquid crystal compound. The dielectric anisotropy (DELTA epsilon) of the liquid crystal compound can be, for example, in the range of 3 to 20. In addition, the liquid crystal compound may have a vertical permittivity ([epsilon]) within the range of, for example, 1 to 10. [ Refers to a dielectric constant measured along the direction of the electric field in a state where a voltage is applied so that the direction of the electric field due to the applied voltage and the optical axis of the liquid crystal layer containing the liquid crystal compound are substantially perpendicular. In one example, when the direction of the electric field is vertical, the vertical permittivity may refer to the dielectric constant measured with the liquid crystal compound oriented horizontally. When the dielectric anisotropy and the vertical permittivity of the liquid crystal compound satisfy the above range, for example, each mode of the liquid crystal cell can be switched even with a low driving voltage. Unless otherwise specified herein, the dielectric constant of a liquid crystal compound may refer to a dielectric constant at a frequency of 1 KHz and room temperature, for example, 25 占 폚.

The modulus of elasticity of the liquid crystal compound can be suitably selected in consideration of the target physical properties, for example, irregularly arranged states and mutual switching characteristics in the vertical or horizontal alignment state. In the present specification, the " elastic modulus of liquid crystal compound " may mean a value obtained by quantifying the strength of a force that is restored to the original state due to the elastic restoring force in a state in which the molecular arrangement of the liquid crystal compound is uniformly changed by external action . In one example, the modulus of elasticity of the liquid crystal compound can be in the range of 5 to 30. When the elastic modulus of the liquid crystal compound satisfies the above range, for example, a stable bistable mode can be realized through interaction with an ionic compound.

The refractive index anisotropy of the liquid crystal compound can be appropriately selected in consideration of the object physical properties, for example, the haze or the transmittance characteristics of the liquid crystal cell. In the present specification, "refractive index anisotropy" may mean a difference between an ordinary refractive index and an extraordinary refractive index of a liquid crystal compound. In one example, the refractive index anisotropy of the liquid crystal compound may be in the range of 0.1 to 0.25. The normal refractive index and the extraordinary refractive index of the liquid crystal compound can be appropriately selected so long as the difference satisfies the above range. For example, the normal refractive index of the liquid crystal compound can be within the range of 1.4 to 1.6, . When the refractive index anisotropy of the liquid crystal compound satisfies the above range, for example, a liquid crystal cell capable of switching between a haze mode and a non-haze mode having excellent haze characteristics can be realized. Unless otherwise specified herein, the refractive index of a liquid crystal compound may refer to a refractive index at 589 nm and room temperature, for example, at 25 占 폚.

The phase transition temperature of the liquid crystal compound can be appropriately selected within a range that does not impair the purpose of the present application. As described below, the bistable liquid crystal cell of the present application can switch from the transmissive mode to the non-haze mode or the haze mode by heating the liquid crystal layer to the temperature necessary for the phase transition of the smectic A phase to the nematic phase or the isotropic phase . The temperature at which the smectic A phase of the liquid crystal compound transitions to the nematic phase or the isotropic phase can be, for example, within a range of about 30 캜 to 100 캜, but is not limited thereto.

The liquid crystal cell may further include an anisotropic dye in the liquid crystal layer. The anisotropic dye can improve, for example, the property of varying the transmittance of the liquid crystal cell. As used herein, the term " dye " may refer to a material that is capable of intensively absorbing and / or deforming light within a visible light region, for example, within a wavelength range of 400 nm to 700 nm, The term " anisotropic dye " may mean a material capable of anisotropic absorption of light in at least a part or the entire range of the visible light region.

As the anisotropic dye, for example, known dyes known to have properties that can be aligned according to the alignment state of the liquid crystal compound can be selected and used. As the anisotropic dye, for example, a black dye can be used. Such dyes are known, for example, as azo dyes or anthraquinone dyes, but are not limited thereto.

The anisotropic dye is a dye having a dichroic ratio, that is, a value obtained by dividing the absorption of polarized light parallel to the long axis direction of an anisotropic dye by the absorption of polarized light parallel to the direction perpendicular to the major axis direction of 5 or more, 6 or more, Can be used. The dye may satisfy the dichroic ratio at least at some wavelength or at any wavelength within the wavelength range of the visible light region, for example, within the wavelength range of about 380 nm to 700 nm or about 400 nm to 700 nm. The upper limit of the dichroic ratio may be, for example, 20 or less, 18 or less, 16 or less, or 14 or less.

The ratio of the anisotropic dye in the liquid crystal layer can be appropriately selected according to the objective properties, for example, the desired transmittance variable characteristics of the liquid crystal cell. For example, the anisotropic dye may be present in an amount of at least 0.01, at least 0.1, at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, Or more, 0.9% or more, or 1.0% or more by weight of the liquid crystal layer. The upper limit of the proportion of the anisotropic dye in the liquid crystal layer is, for example, 3 wt% or less, 2 wt% or less, 1.9 wt% or less, 1.8 wt% or less, 1.7 wt% or less, 1.6 wt% or less, 1.5 wt% 1.4 wt% or less, 1.3 wt% or less, 1.2 wt% or less, or 1.1 wt% or less. When the ratio of the anisotropic dyes in the liquid crystal layer satisfies the above range, for example, the transmittance variation characteristic of the liquid crystal cell can be improved by about 10% or more as compared with the case where the anisotropic dye is not included.

As described above, the liquid crystal cell can exhibit excellent transmittance variable characteristics when it contains an anisotropic dye. For example, the liquid crystal cell may have a transmissive mode with a transmittance of at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90% And a black mode in which the transmittance is 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less or 5% or less. When the liquid crystal cell is implemented so as to switch between the transmissive mode and the black mode, the liquid crystal compound may exist in an aligned state in the transmission mode, for example, and in an irregularly arranged state in the black mode . This excellent transmittance variable property can be achieved, for example, by further including an anisotropic dye in the liquid crystal cell and adjusting the alignment state of the liquid crystal compound by applying an electric field of a suitable frequency. Further, the transmittance range can be adjusted by appropriately selecting the ratio of anisotropic dyes in the liquid crystal layer, the absorption wavelength or extinction coefficient of anisotropic dyes, and the like.

The liquid crystal cell may further include a polymer network in the liquid crystal layer. The polymer network may further be included, for example, to control the haze or transmittance characteristics of the liquid crystal cell. The polymer network may also be in phase separated form from the liquid crystal compound. The polymer network in the liquid crystal layer can be contained in the liquid crystal layer in a structure in which a polymer network is distributed in a continuous liquid crystal compound, that is, a so-called PNLC (Polymer Network Liquid Crystal) structure. Alternatively, the liquid crystal layer may be contained in a liquid crystal layer in a polymer dispersed liquid crystal (PDLC) structure in which a liquid crystal region containing a liquid crystal compound is dispersed in a polymer network.

The polymer network may be, for example, a network of precursors comprising polymeric compounds. Thus, the polymer network may comprise polymeric compounds in a polymerized state. As the polymerizable compound, a non-liquid crystalline compound which does not exhibit liquid crystallinity can be used. As the polymerizable compound, a compound having at least one polymerizable functional group known to be capable of forming a polymer network of a so-called PDLC or PNLC device or a non-polymerizable compound having no polymerizable functional group, if necessary, can be used. Examples of the polymerizable compound that can be contained in the precursor include acrylate compounds and the like, but are not limited thereto.

The ratio in the liquid crystal layer of the polymer network can be appropriately selected in consideration of the target properties, for example, the haze or the transmittance characteristics of the liquid crystal cell. The polymer network may be included in the liquid crystal layer in a ratio of, for example, 40 wt% or less, 38 wt% or less, 36 wt% or less, 34 wt% or less, 32 wt% or less, or 30 wt% or less. The lower limit of the ratio in the liquid crystal layer of the polymer network is not particularly limited but may be, for example, 0.1 wt% or more, 1 wt%, 2 wt% or more, 3 wt% or more, 4 wt% or more, 5 wt% %, 7 wt% or more, 8 wt% or more, 9 wt% or more, or 10 wt% or more.

Figure 1 illustrates, by way of example, a bistable liquid crystal cell 10. The liquid crystal cell 10 includes two substrates 110 arranged opposite to each other and the liquid crystal layer 130 may exist between the two substrates 110 arranged opposite to each other. The electrode unit 120 is disposed on one surface of the liquid crystal layer 130 and the heat generating unit 140 is disposed on the other surface of the liquid crystal layer 130 to provide a driving voltage and a driving temperature to the liquid crystal layer.

The heating unit

The heating unit 140 may include a heating electrode having a conductive material. Such an exothermic electrode may include a conductive material to allow a current to flow, and heat may be generated by resistance heat when an electric current flows. The exothermic electrode may be formed of an alloy of Al, Ag, Mg, Cr, Ti, Ni, Au, Ta, Cu, Ca, Co, Fe, Mo, W, Pt, Yb, Lt; / RTI > Alternatively, the exothermic electrode may be formed of a light-transmitting material including ITO, ZnO, SnO ₂ , TiO ₂ , AZO, GZO, WO ₃ , or the like. Of course, the material for the heating electrode included in the heating unit 140 is not limited thereto, and conductive polymer materials such as polyacetylene, polypyrrole, polyaniline, polyphenylene, and PEDOT may also be used for forming the heating electrode.

In one example, the heating electrode of the heat generating unit 140 may be formed corresponding to the entire surface of the liquid crystal layer, or may be formed only on a part of the surface of the liquid crystal layer. The heating electrode may have a shape longer than the width like a wiring or may have the same shape as a common electrode like a counter electrode formed integrally in a display region of an organic light emitting display device.

In one example, the heating electrode of the heat generating unit 140 may have a shape longer than the width, such as a wiring, and may have a shape similar to a tube electrode such as an opposing electrode integrally formed in a display region of the organic light- .

2 and 3, the heating electrode may be a transparent heating electrode 141 formed of a metal mesh pattern or a zigzag pattern. At this time, in order to make the exothermic electrode transparent, the line width of the transparent heat generating electrode 141 may be 7 μm or less.

Although the transparent heat generating electrode 141 may be formed by, for example, a photo resist, a silver salt process, or a roll to roll process, the method of forming the transparent heat generating electrode 141 of the present invention But is not limited thereto.

Here, in the method of forming the transparent heat generating electrode 141 by the photoresist method, a metal foil is first laminated on the substrate 110, and a dry film is laminated on the metal foil. When the dry film is irradiated with ultraviolet rays, the dry film is selectively cured. In addition, since the dry film is selectively cured, the unhardened portion of the dry film can be removed by dissolving it in a developing solution such as sodium carbonate (Na2CO3) or potassium carbonate (K2CO3). In addition, the dry film can be selectively removed to pattern the opening to form the opening. Accordingly, the metal foil exposed through the opening of the dry film is selectively etched and patterned, whereby the metal mesh pattern transparent heat generating electrode 141 can be formed.

A method of forming the transparent heat generating electrode 140 by a silver salt treatment method is a method of applying a silver salt emulsion to the substrate 110 and selectively exposing the silver salt emulsion, As the pattern is formed, a metal mesh pattern transparent heat generating electrode 141 is formed. At this time, the silver salt may be composed of, for example, silver chloride (AgCl).

A method of forming a transparent heating electrode 141 by a roll to roll method is a method in which silver nano ink is pattern printed on a substrate 110 in the form of a mesh by screen printing or the like (DPT: Direct Printing Technology To form a mesh-pattern transparent heat generating electrode 141 made of a metal.

2 and 3, the heat generating unit 140 includes a terminal electrode 142 electrically connected to the edge of the transparent heat generating electrode 141. Here, the terminal electrode 142 can be integrally formed using the same components as the transparent heat generating electrode 141. The terminal electrode 142 may be formed separately from the transparent heating electrode 140 by using a screen printing method, a gravure printing method, or an inkjet printing method, for example. It is possible to print. At this time, as the material of the terminal electrode 142, a silver paste or an organic silver material having excellent electric conductivity may be used. Although the terminal electrodes 143 are connected to both ends of the transparent heating electrode 141 in the drawing, they are illustrative and may be connected only to one end of the transparent heating electrode 141.

Here, the terminal electrode 143 is electrically connected to the edge of the transparent heat generating electrode 141, and supplies electricity to the transparent heat generating electrode 141. At this time, the terminal electrodes 143 may be formed as a pair in the form of a rectangle bar, and may be positioned on both sides of the transparent heat generating electrode 141, but the shape and position of the terminal electrode 143 must be limited thereto It is not. Further, the terminal electrode 143 can be supplied with electricity through a power supply control section including a power supply means and a switch.

3, the heating unit 140 includes a transparent heating electrode 141 and a terminal electrode 142 connected to the transparent heating electrode 141. The terminal electrode 142 is connected to the transparent heating electrode 141 It is connected to both sides of the edge.

Here, the transparent heat generating electrode 141 is formed on the substrate in a large number. At this time, the transparent heat generating electrodes 141 may be spaced apart by a predetermined height to be patterned into a plurality of rows or columns, but the patterning shape is not necessarily limited to a plurality of rows or columns.

In addition, a plurality of connection terminals 143 are formed so that the terminal electrodes 143 are connected to both sides of the edges of the transparent heat generating electrodes 141 patterned in the plurality. Thus, the terminal electrode 143 can transmit electricity received through the power control unit (not shown) to the plurality of transparent heating electrodes 141 through the plurality of connection terminals 143, respectively.

Board

As the substrate 110, a known material can be used without any particular limitation. For example, inorganic films such as glass films, crystalline or amorphous silicon films, quartz or indium tin oxide (ITO) films, and plastic films can be used. As the substrates 110 and 210, an optically isotropic substrate, a substrate optically anisotropic like a retardation layer, a polarizing plate, a color filter substrate, or the like can be used.

Plastic substrates include TAC (triacetyl cellulose); A cycloolefin copolymer (COP) such as a norbornene derivative; Poly (methyl methacrylate), PC (polycarbonate), polyethylene (PE), polypropylene (PVP), polyvinyl alcohol (PVA), diacetyl cellulose (DAC), polyacrylate (PAC), polyether sulfone (PES) (PPS), polyarylate (PAR), amorphous fluorine resin, or the like may be used as the substrate, but the present invention is not limited thereto. A coating layer of a silicon compound such as gold, silver, silicon dioxide or silicon monoxide, or a coating layer such as an antireflection layer may be present on the substrate.

The electrode portion

The electrode unit 120 of the liquid crystal cell may include at least one electrode layer, and the electrode layer may be disposed adjacent to the liquid crystal layer. Such an electrode layer can apply a vertical electric field to the liquid crystal layer so that the alignment state of the liquid crystal compound in the liquid crystal layer can be switched. The electrode layer can be formed by, for example, depositing a conductive polymer, a conductive metal, a conductive nanowire, or a metal oxide such as ITO (Indium Tin Oxide). The electrode layer may be formed to have transparency. In this field, various materials and forming methods capable of forming a transparent electrode layer are known, and all of these methods can be applied. If necessary, the electrode layer formed on the surface of the substrate may be formed to correspond to the entire surface of the substrate, and may be appropriately patterned to correspond to only a part of the surface of the substrate.

Bistable liquid cells according to the first and second embodiments are shown in Figs. 1 and 4. Fig. 1, the heating unit 140 is a heating electrode, and the electrode unit 120 and the heating electrode are opposed to each other to form a liquid crystal layer 130. In the bistable liquid crystal cell 10 according to the first embodiment, A vertical voltage can be applied.

4, in the bistable liquid crystal cell 20 according to the second embodiment, the electrode unit 220 is two oppositely disposed electrodes for applying a vertical voltage to the liquid crystal layer 230, Is a heating electrode formed separately from the electrode.

A barrier layer 250 functioning as an insulating film for electrically insulating the respective electrodes may be formed between the electrodes for applying the vertical voltage and the heating electrodes. Barrier layer 250 may also have the function of preventing permeation of oxygen, moisture, nitrogen oxides, sulfur oxides or ozone in the atmosphere. As the barrier layer 250, an organic insulating film or an inorganic insulating film can be suitably selected and used according to the intended use without particular limitation, as long as it has the function of the electric insulating film.

The barrier layer 250 can be used without limitation as long as it is a non-conductive material. Specific examples of the barrier layer include metals such as In, Sn, Pb, Au, Cu, Ag, Al, Ti, and Ni; _{TiO, TiO 2, Ti 3 O} 3, Al 2 O 3, MgO, SiO, SiO 2, GeO, NiO, CaO, BaO, Fe 2 O 3, Y2O 3, ZrO 2, Nb 2 O 3 and, CeO _2, and ; Metal nitrides such as SiN; Metal oxynitrides such as SiON; Metal fluorides such as MgF ₂ , LiF, AlF ₃ and CaF ₂ ; Examples of the polyolefin include polyethylene, polypropylene, polymethyl methacrylate, polyimide, polyurea, polytetrafluoroethylene, polychlorotrifluoroethylene, polydichloro difluoroethylene, or a mixture of chlorotrifluoroethylene and dichlorodifluoroethylene Copolymer; A copolymer obtained by copolymerizing tetrafluoroethylene with a comonomer mixture comprising at least one comonomer; A fluorine-containing copolymer having a cyclic structure in the copolymer main chain; An absorbent material having an absorption rate of 1% or more; And a moisture-proof material having an absorption coefficient of 0.1% or less. In one example, it may be a monolayer structure of a barrier layer or a multi-layer structure.

The thickness of the barrier layer is not particularly limited and may be appropriately selected depending on the intended use. In one example, the thickness of the barrier layer may be from 5 nm to 1000 nm, from 7 nm to 750 nm, or from 10 nm to 500 nm. When the thickness of the barrier layer satisfies the above numerical range, the function as an electrical insulating film is sufficient, and transparency of the transparent substrate can be maintained with an appropriate light transmittance.

The light transmittance of the barrier layer is not particularly limited and may be appropriately selected depending on the intended use. In one example, the light transmittance of the barrier layer may be at least about 80%, at least 85%, or at least 90%.

Although the heat generating units 140 and 240 are illustrated as being formed on the lower substrates 110 and 210 in the drawing, it is possible to apply heat to the liquid crystal cells 10 and 20 As far as possible, its location is not limited. For example, the heat generating units 140 and 240 may be located below the upper substrates 110 and 210, or may be located below the lower substrates 110 and 210. [

In addition, although only one heat generating portion 140 or 240 is shown in the liquid crystal cell, the liquid crystal cell may further include one or more heat generating portions 140 and 240 to increase a temperature rising speed. The liquid crystal cell 20 is formed on the lower substrate 210 and the lower substrate 110 under the liquid crystal layer 230 by using the first counter electrode 220 and the second counter electrode 220 formed on the first counter electrode 220, A first barrier layer 250 and a first heating electrode 240 formed on the first barrier layer 250 are formed on the upper substrate 210 and the upper substrate 110, A second barrier layer 250 formed under the second counter electrode 220 and a second heating electrode 240 formed under the second barrier layer 250 may be formed on the second counter electrode 220, .

The bistable liquid cell according to the third and fourth embodiments is shown in Figs. 5 and 6. Fig.

Comparing the liquid crystal cells 30 and 40 of Figs. 5 and 6 with the liquid crystal cells 10 and 20 shown in Figs. 1 and 4, a pair of alignment films 360 and 460 ). ≪ / RTI > Explanations of other structures except for the orientation films 360 and 460 are the same as those described above and thus will be omitted.

Exemplary alignment films 360 and 460 are horizontal alignment films. The alignment films 360 and 460 may be disposed adjacent to the liquid crystal layer. The fact that the alignment films 360 and 460 are disposed adjacent to the liquid crystal layer in this specification means that the alignment films 360 and 460 are arranged so as to influence the orientation of the liquid crystal compound in the liquid crystal layer.

The kind of the alignment film can be appropriately selected depending on the kind of the smectic liquid crystal compound contained in the liquid crystal layer, for example. In one example, if the smectic liquid crystal compound contained in the liquid crystal layer is a Smectic A liquid crystal compound, an alignment film is not necessarily required for driving the liquid crystal device, but an alignment film may be further used to control alignment of the liquid crystal compound . Such an alignment film may be, for example, a vertical or horizontal alignment film. As the vertical or horizontal alignment film, an alignment film having a vertical or horizontal alignment capability with respect to the liquid crystal compound of the adjacent liquid crystal layer can be used without any particular limitation. As such an orientation film, for example, an orientation film known to be capable of exhibiting orientation characteristics by a non-contact method such as irradiation of linear polarization including a contact type orientation film or a photo orientation film compound such as a rubbing orientation film can be used.

These liquid crystal cells can be driven in various ways. The liquid crystal cell can be driven in a bistable mode. For example, the liquid crystal cell can switch between the transmissive mode and the haze mode, and between the transmissive mode and the non-hazy mode, and application of external energy such as voltage or heat is required only at the switching of the mode. Such a liquid crystal cell can switch between the transmission mode, the haze mode and the non-haze mode depending on the alignment state of the liquid crystal compound, and external energy such as voltage and heat is required upon changing the alignment state of the liquid crystal compound.

The term "haze mode" as used herein means a mode in which the liquid crystal cell exhibits haze above a predetermined level, and "non-haze mode" means a mode in which light is transmissive or a mode that indicates haze below a predetermined level.

For example, in the haze mode, the liquid crystal cell may have a haze of 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, or 50% or more. In the haze mode, the transmittance of the liquid crystal cell may be 10 to 50%, 20 to 45%, and 30 to 40%.

In the non-haze mode, for example, the liquid crystal cell may have a haze of 10% or less, 8% or less, 6% or less, or 5% or less. In the haze mode, the transmittance of the liquid crystal cell may be 10 to 50%, 20 to 45%, and 30 to 40%.

In this specification, the term " transmissive mode " means a mode in which the liquid crystal cell exhibits a transmittance higher than a predetermined level. For example, in the transmission mode, the liquid crystal cell may have a transmittance of 50% or more, 55% or more, 60% or more, or 65% or more. In the transmissive mode, the haze of the liquid crystal cell may be 5% or less, 3% or less, 2% or less, or 1% or less.

The transmittance and haze can be evaluated using a hazemeter (NDH-5000SP). The haze may be a percentage of the transmittance of the diffused light to the transmittance of the total transmitted light passing through the object to be measured. The haze can be evaluated in the following manner using the haze meter. That is, light is transmitted through the object to be measured and is incident into the integrating sphere. In this process, light is separated into diffused light (DT) and parallel light (PT) by the object to be measured. The light is reflected in the integrating sphere and condensed on the light receiving element, and the haze can be measured through the condensed light Do. That is, the total transmitted light TT according to the above procedure is the sum (DT + PT) of the diffused light DT and the parallel light PT and the haze is the percentage of diffused light with respect to the total transmitted light (Haze (%) = 100 X DT / TT).

The liquid crystal cells 10 and 20 of the first and second embodiments do not include an alignment film. The driving of the liquid crystal cell of the liquid crystal cell of the first and second embodiments is shown in Fig. 7 (liquid crystal compound gray display and anisotropic dye black display). When the vertical voltage V is applied to the liquid crystal layers 130 and 230, the liquid crystal compounds in the liquid crystal layers 130 and 230 are vertically aligned, and the transmissive mode is switched to a transmissive mode having a transmittance of 60% or more. After switching to the transmission mode, the transmission mode can be maintained even if the electric field is removed. When the vertically aligned liquid crystal layers 130 and 230 are heated through the heat generating portions 140 and 240 in the transmissive mode state, the liquid crystal compounds in the liquid crystal layer are irregularly aligned (H) and the haze mode is switched to a haze mode with a haze of 15% or more.

The liquid crystal cells 30 and 40 of the third and fourth embodiments include horizontal alignment films 360 and 460. The driving of the liquid crystal cell of the liquid crystal cell of the third and fourth embodiments is shown in Fig. 8 (liquid crystal compound gray display and anisotropic dye black display). When a vertical voltage V is applied to the liquid crystal layers 330 and 430, the liquid crystal compounds in the liquid crystal layers 330 and 430 are aligned vertically and the transmissive mode is switched to a transmissive mode having a transmittance of 60% or more. After switching to the transmission mode, the transmission mode can be maintained even if the electric field is removed. When the liquid crystal layer vertically aligned through the heat generating portions 340 and 440 in the transmissive mode is heated (H), the liquid crystal compound in the liquid crystal layer is aligned horizontally due to the influence of the horizontal alignment film, Or less.

The electric field frequency required to switch to the transmission mode in the non-haze mode or the haze mode may be a low frequency within the range of 1 Hz to 500 Hz. The range of the electric field frequency required for switching each mode of the liquid crystal cell is not limited to the above range and can be appropriately changed in consideration of the object property, for example, the haze or the transmittance characteristic of each mode.

The liquid crystal cell can switch between the haze mode and the non-haze mode to the transmissive mode with a low driving voltage. In one example, the lower limit of the required voltage for switching to the transmissive mode is about 50V or more, 55V or more, 60V or more, 65V or more, 70V or more, V or more, 75V or more, or 80V or more, but is not limited thereto.

The driving temperature required for switching from the transmissive mode to the non-haze mode or the haze mode may vary depending on the type of liquid crystal compound used. Specifically, it is necessary to heat the liquid crystal layer to a temperature necessary for phase transition of the smectic A phase to the nematic phase or the isotropic phase. The driving temperature required to switch to the non-haze mode or the haze mode may be, for example, within the range of about 30 占 폚 to 100 占 폚. More specifically, the lower limit of the drive temperature may be 30 ° C or higher, 35 ° C or higher, 40 ° C or higher, 45 ° C or higher, 50 ° C or higher, or 55 ° C or higher, and the upper limit of the drive temperature may be 100 ° C or lower, Less than or equal to 85 ° C, less than or equal to 80 ° C, less than or equal to 75 ° C, less than or equal to 70 ° C, less than or equal to 65 ° C, or less than or equal to 60 ° C.

The present application also relates to the use of a liquid crystal cell. An exemplary liquid crystal cell can implement a bistable mode that switches between a haze mode (or a non-haze mode) and a transmissive mode with a low driving voltage. Such a liquid crystal cell can be usefully used in an optical modulator. Examples of the optical modulation device include, but are not limited to, a smart window, a window protective film, a flexible display device, an active retarder for 3D image display, or a viewing angle adjusting film. The method of forming the optical modulator as described above is not particularly limited, and a conventional method can be applied as long as the liquid crystal cell is used.

The exemplary liquid crystal cell has a low driving voltage and a high heating temperature, and is operated between the haze mode and the transmissive mode; Or a bistable mode for switching between the non-haze mode and the transmissive mode. Such a liquid crystal cell can be applied to various optical modulation devices such as a smart window, a window protective film, a flexible display device, an active retarder for 3D image display, or a viewing angle adjusting film.

Fig. 1 exemplarily shows a liquid crystal cell according to the first embodiment.
Figs. 2 and 3 illustrate a pattern of the heat generating portion by way of example.
Figs. 4 to 6 illustrate exemplary liquid crystal cells according to the second to fourth embodiments. Fig.
Figs. 7 and 8 illustrate schematically the driving method of the liquid crystal cell.
Fig. 9 shows a state of the liquid crystal cell according to the first embodiment according to the heating driving.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the scope of the present application is not limited to the following examples.

1. Transmittance and Hayes's  Measure

The transmittance and haze of the liquid crystal cell prepared in Examples and Comparative Examples were measured by ASTM method using a haze meter, NDH-5000SP.

Example  One.

An ITO layer for a heating electrode was formed on a part of a glass substrate (width x length = 5 cm x 5 cm), and then a 400 nm thick SiO x layer, an ITO layer for a transparent electrode and a known horizontal alignment layer were sequentially formed A first substrate laminate was prepared, and a second substrate laminate was produced by sequentially forming an ITO layer for a transparent electrode and a known horizontal photo alignment layer on a glass substrate (width x length = 5 cm x 5 cm).

The first and second substrate stacks are arranged so that the horizontal light alignment films face each other and are spaced apart to have a gap of about 9 mu m and then the liquid crystal composition is injected between the spaced apart first and second substrate stacks , And an edge were sealed to fabricate a liquid crystal cell. The liquid crystal composition was prepared by mixing a liquid crystal compound (HJA151200-000, manufactured by HCCH) exhibiting a Smectic A phase and an anisotropic dye (X12, manufactured by BASF) in a weight ratio of 99.3: 0.7 (liquid crystal compound: anisotropic dye) .

Example  2

In the production of the first and second substrate stacks, a liquid crystal cell was produced in the same manner as in Example 1 except that a horizontal photo alignment film was not formed.

Test Example  1. Driving of liquid crystal cell

A power source for applying a vertical electric field was connected to the upper and lower transparent electrode ITO layers of each of the liquid crystal cells manufactured in the Example and the power was connected to the ITO layer for the heating electrode, . FIG. 9 is a graph showing a state in which a vertical electric field is applied to the entire region of the liquid crystal cell of Example 1 at a frequency of 60 Hz and a voltage of 80 V, and then a heating electrode is driven only in a partial region of the liquid crystal cell, It is an image. As shown in Fig. 9, it can be seen that the region (upper portion) where the heat is not applied remains in a transparent state while the transmittance is decreased in the region where heat is applied (lower portion).

Table 1 shows the total transmittance and haze of each mode while driving the liquid crystal cell by applying the vertical electric field and heat as described above.

As shown in Table 1, in the case of the liquid crystal cell of Example 1, when a vertical electric field was applied at a frequency of 60 Hz and a voltage of 80 V, a transmissive mode with a transmittance of about 69.06% and a haze of about 0.5% was realized, When the temperature was heated to 60 占 폚, the non-haze mode conversion was achieved with a transmittance of about 39.72% and a haze of about 1.16%. Also, in the implementation of the transmission mode, the transmission mode was maintained for about 240 hours or more even after removing the vertical electric field, and the non-haze mode was maintained for about 240 hours or more without driving the heating electrode after switching to the non-haze mode.

In the case of the liquid crystal cell of Example 2 in which the alignment film was not formed, when a vertical electric field was applied at a frequency of 60 Hz and a voltage of 80 V, a transmissive mode with a transmittance of about 68.27% and a haze of about 0.7% was realized, When the temperature was heated to about 60 DEG C by driving, it was converted to the haze mode having a transmittance of about 35.50% and a haze of about 54%. Also, in the implementation of the transmission mode, the transmission mode was maintained for about 240 hours or more even after removing the vertical electric field, and the non-haze mode was maintained for about 240 hours or more without driving the heating electrode after switching to the non-haze mode.

Vertical electric field 80V [60Hz] with Heating electrode drive [60 ℃] Example 1 Total transmittance 69.06% Total transmittance 39.72% Hayes 0.5% Hayes 1.16% Example 2 Total transmittance 68.27% Total transmittance 35.50% Hayes 0.7% Hayes 54%

110, 210, 310, 410: substrate
130, 230, 330, 430: liquid crystal layer
131, 331: Smectic liquid crystal compound
120, 220, 320, 420:
140, 240, 340, 440:
360, 460: Orientation film

Claims (23)

Two substrates arranged opposite to each other;
A liquid crystal layer disposed between the two substrates and including a liquid crystal compound;
An electrode unit for applying a voltage to the liquid crystal layer; And
And a heat generating portion for applying heat to the liquid crystal layer. The method according to claim 1,
Wherein the liquid crystal compound is a Smectic A liquid crystal compound. The method according to claim 1,
Wherein the liquid crystal compound is a compound represented by the following Formula 2:
[Chemical Formula 1]

Wherein A is a single bond, -COO- or -OCO-, R ₁ to R ₁₀ are each independently selected from the group consisting of hydrogen, a halogen, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a cyano group, Lt; / RTI >
(2)

Wherein B is a single bond, -COO- or -OCO-, and R ₁₁ to R ₁₅ are each independently hydrogen, a halogen, an alkyl group, an alkoxy group, an alkoxycarbonyl group, a cyano group or a nitro group,
In Formula 1 and Formula 2, any one of R ₁ to R ₁₅ is an alkyl group, alkoxy group, or alkoxycarbonyl group having 5 or more carbon atoms. The method according to claim 1,
Wherein the liquid crystal layer further comprises an anisotropic dye. 5. The method of claim 4,
Wherein the anisotropic dye is included in the liquid crystal layer in a ratio within a range of 0.01 wt% to 3 wt%. The method according to claim 1,
Wherein the heat generating portion comprises a heating electrode having a conductive material. The method according to claim 6,
Wherein the conductive material is a metal or a metal oxide. The method according to claim 6,
Wherein the heating electrode has a linearly patterned shape having a length longer than a width. The method according to claim 6,
Wherein the heating portion further comprises a terminal electrode formed at an edge of the heating electrode. 10. The method of claim 9,
Wherein the heating electrode is formed on the substrate in a plurality of rows or columns,
Wherein the terminal electrode further comprises a plurality of connection terminals extended to be connected to the heating electrodes formed in a plurality of rows or columns. The method according to claim 1,
Wherein the heating portion is an exothermic electrode,
Wherein the electrode portion and the heating electrode are opposed to each other, and a vertical voltage is applied to the liquid crystal layer. The method according to claim 1,
The electrode portion is two opposed electrodes for applying a vertical voltage to the liquid crystal layer,
Wherein the heat generating portion is an exothermic electrode. 13. The method of claim 12,
And a barrier layer formed between the electrode and the heating electrode. 13. The method according to claim 11 or 12,
When a vertical voltage is applied to the liquid crystal layer, the liquid crystal compound in the liquid crystal layer is vertically aligned to switch to a transmission mode having a transmittance of 50% or more,
Wherein when the liquid crystal layer is heated through the heating electrode, the liquid crystal compound in the liquid crystal layer is irregularly aligned to switch to a haze mode having a haze of 15% or more. 15. The method of claim 14,
Wherein the frequency of the electric field applied for switching to the transmissive mode in the haze mode is in the range of 1 to 500 Hz. 15. The method of claim 14,
Wherein the required temperature for switching from the transmission mode to the haze mode is within the range of 30 占 폚 to 100 占 폚. 12. The method of claim 11,
And an alignment layer disposed adjacent to the liquid crystal layer. 13. The method of claim 12,
And a horizontal alignment film disposed adjacent to the liquid crystal layer. The method according to claim 17 or 18,
When a vertical voltage is applied to the liquid crystal layer, the liquid crystal compound in the liquid crystal layer is vertically aligned to switch to a transmission mode having a transmittance of 50% or more,
Wherein when the liquid crystal layer is heated through the heating electrode, the liquid crystal compound in the liquid crystal layer is horizontally aligned to switch to a non-haze mode with a haze of 10% or less. 20. The method of claim 19,
Wherein the frequency of the electric field applied to switch from the non-haze mode to the transmissive mode is in the range of 1 to 500 Hz. 20. The method of claim 19,
Wherein the required temperature for switching from the transmissive mode to the non-hazy mode is within the range of 30 占 폚 to 100 占 폚. A light modulation device comprising the liquid crystal cell of claim 1. A smart window comprising the liquid crystal cell of claim 1.

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