KR20160115428A - Liquid crystal cell - Google Patents

Abstract

The present invention relates to a liquid crystal cell and a use thereof. An exemplary liquid crystal cell can generally realize a transmissive mode, be driven at a low driving voltage, and show an excellent haze feature. The liquid crystal cell can be applied to a variety of light modulation devices such as a smart window, a window protection film, a flexible display device, a light blocking plate for a transparent display, an active retarder for displaying a 3D image, a viewing angle adjusting film or the like.

Description

Liquid crystal cell {LIQUID CRYSTAL CELL}

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

A normal transmission mode element is a device in which a transmission mode is realized in the absence of an external action, a switching mode is switched to an interrupting mode under an external action, and the transmission mode is switched to a transmission mode again when an external action is removed.

Patent Document 1 discloses a normal transmission mode element capable of varying between a transmission mode and a haze mode. The device of Patent Document 1 is a so-called PDLC (Polymer Dispersed Liquid Crystal) device realized by dispersing a liquid crystal in a polymer matrix. Since the liquid crystal compound is usually not aligned in the PDLC, the scattering state However, a normal transmission mode is realized by applying a vertical alignment film.

However, in the conventional transmission mode device using the PDLC of Patent Document 1, development of a normal transmission mode device capable of compensating for the above problem due to high drive voltage, fluctuation of residual haze level due to exposure characteristics, It is necessary.

Korean Patent Laid-Open Publication No. 2014-0077861

The present application provides liquid crystal cells and uses thereof.

An exemplary liquid crystal cell may include two substrates and a liquid crystal layer. 1, the two substrates 1011 and 1012 are disposed opposite to each other in the liquid crystal cell, and the liquid crystal layer 102 is present between the two substrates 1011 and 1012 arranged opposite to each other .

The liquid crystal cell can usually implement a transmissive mode element. The term " normal transmission mode element " in the present application means that the transmission mode is realized in a state in which there is no external action (i.e., an initial state or a normal state), the mode is switched to the haze mode under external action, May be referred to as a switching device. The term " external action " in this application means all kinds of operations performed so as to change the alignment of the liquid crystal compound, and a representative example is the application of a voltage.

In the liquid crystal cell, the liquid crystal layer may include a liquid crystal compound. For example, the liquid crystal compound may be a nematic liquid crystal compound. The term " nematic liquid crystal compound " in the present application may mean a liquid crystal compound exhibiting a nematic phase, for example, a liquid crystal compound having a property that a director of a liquid crystal compound is arranged in a predetermined direction.

In the liquid crystal cell, the liquid crystal layer may have a specific resistance of 1.0 x ¹⁰ < ¹⁰ > More specifically, the resistivity of the liquid crystal layer may be 5.0 x 10 ^{+ 9} ? · Cm or less, 1.0 x 10 ^{+ 9} ? · Cm or less, 5.0 x 10 ⁺⁸ ? · Cm or less or 1.0 x 10 ⁺⁸ ? · Cm or less. In the present specification, the " resistivity " may mean a value converted from the electric conductivity value of the liquid crystal layer. The manner of measuring the electrical conductivity is not particularly limited and can be measured, for example, through an LCR meter. In one example, the resistivity may be a value converted from a horizontal conductivity (? //) or a vertical conductivity (??) Of the liquid crystal layer. The method of converting the resistivity from the conductivity of the liquid crystal layer is not particularly limited, and can be converted by, for example, the equations C and D described in the " Conductivity and Resistivity Evaluation " According to one embodiment of the present application, the resistivity may be a value converted from horizontal conductivity (? //) of the liquid crystal layer. The horizontal conductivity (? //) and the vertical conductivity (??) Will be described in more detail below.

In the present specification, the " resistivity " may be a room temperature resistivity converted on the basis of an area of 1 cm ² and an interval of 1 cm. As used herein, the " normal temperature " may mean a temperature of natural or unheated or unheated temperature, for example, about 23 DEG C or about 25 DEG C within a range of about 10 DEG C to 30 DEG C. When the measured temperature affects the numerical value of the properties described in the present specification, unless otherwise specified, the physical properties are values measured at room temperature. The specific resistance herein is a liquid crystal cell having a size and spacing of 1cm 1cm ² of the actually measured data measured at room temperature with respect to the liquid crystal cell has an area and spacing of the 9㎛ 2.2x4.0cm ² unless otherwise noted May refer to data converted into a standard.

When the liquid crystal layer has a specific resistance value within the above range, the liquid crystal layer may exhibit electrohydrodynamic instability (EHDI) characteristics. The term " EHDI characteristic " in the present specification may mean a characteristic capable of causing haze by causing an irregular arrangement state in a nematic liquid crystal compound by applying external energy to the liquid crystal layer. The lower limit of the specific resistance of the liquid crystal layer can be suitably selected within a range that does not impair the physical properties desired, and for example, 1.0 x 10 ⁺⁷ Ω · cm or more, 5.0 x 10 ⁺⁷ or ⁺⁸ Ω · cm or more 10 x 1.0 .

When the liquid crystal layer exhibits a resistivity in the above-mentioned numerical range, not only an excellent haze characteristic can be exhibited by external energy application but also the haze characteristic can exhibit a linear relationship with respect to the electric conductivity to be described later. The adjustment of the resistivity to the above-mentioned numerical range is carried out by adding additives to the liquid crystal layer such as an ionic impurity, an ionic liquid, a salt, a monomer having a reactive functional group, an initiator or an anisotropic dye By adding them appropriately.

The initial alignment state of the liquid crystal layer may be a state in which the liquid crystal compound of the liquid crystal layer is aligned in a predetermined direction. As used herein, the term " initial alignment state " may mean the alignment or alignment direction of the liquid crystal compound in the absence of any external action on the liquid crystal cell or the optical axis of the liquid crystal layer formed by the liquid crystal compound. The liquid crystal layer may be in a vertically aligned state or a horizontally aligned state, for example, in an initial state. The "vertical alignment state of the liquid crystal layer" in the present application means that the optical axis of the liquid crystal layer is in the range of about 90 degrees to about 65 degrees, about 90 degrees to about 75 degrees, about 90 degrees to about 80 degrees, To about 85 degrees and a tilt angle of about 90 degrees. The term "horizontal alignment state of the liquid crystal layer" in this specification means that the optical axis of the liquid crystal layer is in a range of from about 0 degrees to about 25 degrees, from about 0 degrees to about 15 degrees, from about 0 degrees to about 10 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 cell can realize the transmission mode in the initial state by adjusting the initial alignment state of the liquid crystal layer to the vertical alignment state or the horizontal alignment state. The initial alignment state of the liquid crystal layer can be controlled by imparting liquid crystal alignment properties to the side surfaces of the liquid crystal layers of the two opposing substrates as described later.

In a liquid crystal cell, the liquid crystal layer may have a horizontal conductivity (σ //) or a vertical conductivity (σ⊥) of 10.0 × 10 ^-4 μS / cm or more. More specifically, the horizontal conductivity (σ //) or the vertical conductivity (σ⊥) of the liquid crystal layer is not less than 9.5 × 10 ^-5 μS / cm, not less than 1.0 × 10 ^-4 μS / cm, not less than 5.0 × 10 ^-4 μS / cm , 1.0 x 10 ^-3 μS / cm or more, or 1.0 x 10 ^-2 μS / cm or more. When the horizontal conductivity (σ //) or the vertical conductivity (σ⊥) of the liquid crystal layer is adjusted to the above numerical range, the electrohydrodynamic instability (EHDI) characteristic can be effectively exhibited by applying external energy to the liquid crystal layer. The upper limit of the horizontal conductivity (σ //) or the vertical conductivity (σ⊥) of the liquid crystal layer can be appropriately selected within a range that does not impair the desired physical properties, for example, 1.0 × 10 ^-2 μS / ^-3 μS / cm or less, 9.0 × 10 ^-4 μS / cm or less, or 5.0 × 10 ^-4 μS / cm or less. Adjusting the horizontal conductivity (σ //) or the vertical conductivity (σ⊥) of the liquid crystal layer to the above-described numerical range may be performed by adding appropriate additives to the liquid crystal layer, for example, ionic impurities, ionic liquid, , A monomer having a reactive functional group, an initiator, or an anisotropic dye.

In this specification, the term "horizontal conductivity (σ //)" as used herein means that the direction of the electric field due to the optical axis of the liquid crystal layer and the applied voltage is substantially Quot; refers to a conductivity value measured along the direction of the electric field in a state where a voltage is applied so as to be horizontal with respect to the liquid crystal layer, and " The conductivity value measured along the direction of the electric field. The measurement frequency of the voltage applied in the above is, for example, 60 Hz, and the measured voltage may be 0.5 V, for example.

Fig. 2 is a schematic diagram for explaining a method of measuring the horizontal conductivity σ // and the vertical conductivity σ⊥. As described above, the optical axis of the liquid crystal layer can be determined according to the shape of the liquid crystal compound. As shown in Fig. 2, when the liquid crystal compound 201 has a rod shape, the optical axis of the liquid crystal layer can be seen in its long axis direction (indicated by red color) in a state in which the liquid crystal compound is oriented. In one example, when the long axis direction of the liquid crystal compounds in the liquid crystal layer is parallel to the thickness direction of the liquid crystal layer, i.e., vertically aligned, as shown in Fig. 2A, the horizontal conductivity (σ //) And may be a conductivity measured along the thickness direction in a state in which a voltage is applied so that the electric field E is formed along the direction. In another example, when the major axis direction of the liquid crystal compounds in the liquid crystal layer is orthogonal to the thickness direction, i.e., horizontally oriented, as shown in FIG. 2B, the vertical conductivity (? E may be formed in the thickness direction.

In this specification, unless otherwise specified, the horizontal conductivity (σ //) or the vertical conductivity (σ⊥) is measured with a LCR meter , A value measured at room temperature for a liquid crystal cell having an area of 2.2 x 4.0 cm < ² > and an interval of 9 m was calculated on the basis of an area of 1 cm < ² > and a liquid crystal cell having an interval of 1 cm .

In the measurement of the horizontal conductivity (? //) or the vertical conductivity (??), The horizontal alignment state of the liquid crystal layer is a state in which the liquid crystal compound in the liquid crystal layer is substantially horizontally oriented For example, a retardation value Rin in the range of 150 nm to 3,000 nm according to the following formula A and a thickness direction retardation Rth according to the following formula B is 0 nm to 100 nm, more specifically 0 nm to 100 nm, Lt; RTI ID = 0.0 > nm. ≪ / RTI > In the measurement of the horizontal conductivity (? //) or the vertical conductivity (??), The vertical alignment state of the liquid crystal layer is a state in which the liquid crystal compound in the liquid crystal layer is in a substantially vertical orientation (Rin) according to the following formula (A) is in the range of 0 nm to 100 nm, more specifically 0 nm to 50 nm, and the thickness direction retardation (Rth) according to the following formula And may be within a range of 150 nm to 3000 nm.

[Formula A]

Rin = d (nx - ny)

[Formula B]

Rth = d (nz - ny)

In the equations A and B, d is the thickness of the liquid crystal layer, nx is the refraction index in the slow axis direction in the plane of the liquid crystal layer, ny is the refraction index in the direction perpendicular to the slow axis of the liquid crystal layer, nz is the thickness direction of the liquid crystal layer, That is, a refractive index in a direction perpendicular to both the slow axis and the direction perpendicular thereto. The term "refractive index" in this specification can be a refractive index for light with a wavelength of 550 nm, unless otherwise specified.

The ratio of the vertical conductivity (??) And the horizontal conductivity (? //) of the liquid crystal layer in the liquid crystal cell can be appropriately adjusted in consideration of the physical properties of the desired liquid crystal cell. For example, the ratio (? //? /?) Of the horizontal conductivity (? //) to the vertical conductivity (??) Of the liquid crystal layer is 0.2 or more, 0.25 or more, 0.3 or more, 0.35 or more, 0.4 or more, 0.5 or more, 0.5 or more, 0.6 or more, 0.65 or more, or 0.7 or more. The definitions and measurement methods of the vertical conductivity (σ⊥) and the horizontal conductivity (σ //) can be applied equally to the above description. Therefore, the conductivity ratio may be a room temperature conductivity ratio based on an area of 1 cm ² and an interval of 1 cm. When the ratio of the vertical conductivity (σ⊥) and the horizontal conductivity (σ //) of the liquid crystal layer is controlled within the above numerical range, the liquid crystal cell can be driven with a low driving voltage and can realize a normal transmission mode device exhibiting excellent haze characteristics have. The upper limit of the ratio (? //? /?) Of the horizontal conductivity (? //) to the vertical conductivity (??) Of the liquid crystal layer can be appropriately selected within a range that does not impair the desired physical properties, 2.5 or less, 2.0 or less, 1.5 or less, or 1.0 or less. Adjusting the ratio (σ // ÷ σ⊥) of the horizontal conductivity (σ //) to the vertical conductivity (σ⊥) of the liquid crystal layer to the above-mentioned numerical range means that an appropriate additive such as an ionic impurity, By appropriately adding additives such as an ionic liquid, a salt, a monomer having a reactive functional group, an initiator, or an anisotropic dye.

The ratio (?? /? //) of the vertical conductivity (??) To the horizontal conductivity (? //) of the liquid crystal layer is, for example, 2.0 or less, 1.9 or less, 1.8 or less, 1.7 or less, 1.6 or less , 1.5 or less, 1.4 or less, 1.3 or less, 1.2 or less, 1.1 or less or 1.0 or less. The definitions and measurement methods of the vertical conductivity (σ⊥) and the horizontal conductivity (σ //) can be applied equally to the above description. Therefore, the conductivity ratio is a room temperature conductivity ratio based on an area of 1 cm ² and an interval of 1 cm. When the ratio of the vertical conductivity (σ⊥) and the horizontal conductivity (σ //) of the liquid crystal layer is controlled within the above numerical range, the liquid crystal cell can be driven with a low driving voltage and can realize a normal transmission mode device exhibiting excellent haze characteristics have. The lower limit of the ratio (?? /? //) of the vertical conductivity (??) To the horizontal conductivity (? //) of the liquid crystal layer can be appropriately selected within a range that does not impair the desired physical properties, For example, 0.5 or more, 0.3 or more, 0.2 or more, or 0.1 or more. Adjusting the ratio (?? /? //) of the vertical conductivity (??) To the horizontal conductivity (? //) of the liquid crystal layer to the above-described numerical range is suitable for the liquid crystal layer, Such as an ionic liquid, a salt, a monomer having a reactive functional group, an initiator, or an anisotropic dye.

The liquid crystal compound present in the liquid crystal layer may have a positive dielectric anisotropy or a negative dielectric anisotropy. The term "dielectric constant anisotropy" in this application 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 (In the following, the (+) sign means positive dielectric anisotropy and the (-) sign means negative dielectric anisotropy). The dielectric anisotropy of the liquid crystal compound may be within a range of, for example, ± 40 or less, ± 30 or less, ± 10 or less, or ± 5 or less. When the dielectric anisotropy of the liquid crystal compound is controlled within the above range, for example, a liquid crystal compound capable of being driven with a low driving voltage and exhibiting excellent haze characteristics and having a negative dielectric constant anisotropy in view of better haze characteristics, You can choose to use it. The lower limit of the dielectric anisotropy of the liquid crystal compound can be appropriately selected within a range that does not impair the desired physical properties and can be, for example, 賊 3 or more, 賊 5 or more, 賊 5 or 賊 7 or more.

The refractive index anisotropy of the liquid crystal compound present in the liquid crystal layer can be appropriately selected in consideration of the objective properties, for example, the haze characteristics of the liquid crystal cell. The term " refractive index anisotropy " in the present application may mean a difference between an ordinary refractive index and an extraordinary refractive index of a liquid crystal compound. The refractive index anisotropy of the liquid crystal compound may be in the range of, for example, 0.1 or more, 0.12 or more or 0.15 or more to 0.23 or less or 0.25 or less or 0.3 or less. When the refractive index anisotropy of the liquid crystal compound satisfies the above range, for example, a normal transmission mode device having excellent haze characteristics can be realized.

The two substrates opposed to each other in the liquid crystal cell may be substrates having liquid crystal alignability. The term " substrate having liquid crystal alignability " in the present application can refer to, for example, a substrate to which alignment ability capable of aligning adjoining liquid crystal compounds in a predetermined direction can be affected . In the liquid crystal cell, the liquid crystal layer is present between two substrates having liquid crystal aligning properties, so that an appropriate alignment state can be maintained in an initial state. The two substrates opposed to each other in the liquid crystal cell may be, for example, substrates having vertical orientation or horizontal orientation. As used herein, the term " substrate having vertical orientation or horizontal orientation " may mean a substrate having an orientation capable of orienting adjoining liquid crystal compounds in a vertical direction or a horizontal direction.

As the substrate having liquid crystal alignability, for example, a substrate having an alignment film formed thereon can be used. For example, the alignment films 301 and 302 may exist on the side of the liquid crystal layer 102 of the two opposing substrates 1011 and 1012, as shown in Fig. As the alignment film, for example, an alignment film known to be capable of exhibiting alignment characteristics by a non-contact method such as irradiation of linearly polarized light including a contact type alignment film or a photo alignment film compound such as a rubbing alignment film can be used.

As another example of the orientation-induced substrate, a substrate to which the liquid crystal alignment property is directly applied can be used. For example, a substrate having a hydrophilic surface can be used as the substrate to which the vertical alignment ability is imparted. A substrate having a hydrophilic surface can have a wetting angle for water of, for example, 0 to 50 degrees, 0 to 40 degrees, 0 to 30 degrees, 0 to 20 degrees, or 0 to 10 degrees Or from 10 degrees to 50 degrees, from 20 degrees to 50 degrees, and from 30 degrees to 50 degrees. The method of measuring the wetting angle of the substrate with respect to water is not particularly limited and a wetting angle measurement method known in the art can be used. For example, a DSA100 device manufactured by KRUSS is used to measure the wetting angle of the substrate It can be measured according to the manual. In order to have a hydrophilic surface on the substrate, for example, a hydrophilic treatment may be performed on the surface of the substrate, or a substrate containing a hydrophilic functional group may be used. As the hydrophilizing treatment, corona treatment, plasma treatment or alkali treatment can be exemplified.

As the substrate, 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 substrate, 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 can be used as the substrate, but it is possible to use a substrate such as PPS (polyphenylsulfone), PEI (polyetherimide), PEN (polyethylenemaphthatate) 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.

An exemplary liquid crystal cell can implement the normal transmissive mode as described above. For example, the liquid crystal cell can switch between the transmission mode and the scattering mode. The initial alignment state of the liquid crystal layer may be a state in which the nematic liquid crystal compound is aligned in a predetermined direction, for example, a vertically aligned state or a horizontally aligned state, whereby the liquid crystal cell can realize a transmissive mode in an initial state. The initial alignment state of the liquid crystal layer can be changed by the application of external energy. For example, when external energy is applied to the liquid crystal layer, EHDI characteristics are generated and converted into irregularly arranged states to cause haze. Can be switched to the scattering mode.

The external energy, for example, the electric field, applied to induce haze in the liquid crystal cell can be appropriately selected within a range that does not impair the intended purpose. For example, when the initial alignment state of the liquid crystal layer is a vertically aligned state or a horizontally aligned state, an EHDI characteristic is induced in the liquid crystal layer by applying a vertical electric field, for example, a vertical electric field of about 20 V to 100 V to the liquid crystal cell . The frequency of the applied electric field may be, for example, 500 Hz or less, and an electric field having a frequency of 60 Hz may be applied according to one embodiment of the present application. When the external energy disappears, the liquid crystal layer can return to the initial alignment state, and can be switched back to the transmissive mode.

The term " transmission mode " in the present application may mean a mode capable of transmitting light, or a mode indicating haze below a predetermined level, and the " scattering mode " means a mode in which a liquid crystal cell indicates a haze exceeding a predetermined level have. In the transmission mode, for example, the liquid crystal cell may have a transmittance of 80% or more and a haze of 10% or less with respect to light having a wavelength of 400 nm to 700 nm. In the scattering mode, the liquid crystal cell may have a transmittance of 75% or more, for example, and a haze of 90% or more for light having a wavelength of 400 nm. The haze and transmittance values may be measured by an ASTM method using, for example, a hazemeter (NDH-5000SP).

The liquid crystal cell can be driven with a low driving voltage. For example, the liquid crystal cell is haze per unit area to the switching to the scattering mode, a haze value is less than 90-10% greater than transmission mode (2.2x4.0 cm ²⁾ required voltage is above 10V is, 20V or more, more than 30V, 40V Or more, 50V or more, or 60V or more. The liquid crystal cell can be switched to the scattering mode having excellent haze characteristics in the transmission mode even at a low driving voltage as described above by employing the liquid crystal layer exhibiting the above-mentioned resistivity and conductivity characteristics.

The liquid crystal cell may have a variable transmittance characteristic. The degree of the variable transmittance characteristic of the liquid crystal cell is not particularly limited. For example, liquid crystal cells can switch between two modes in which the difference in transmittance is about 2% to 3% or more. The liquid crystal cell may have excellent transmittance variable characteristics in, for example, a transmission mode and a scattering mode. For example, in a liquid crystal cell, the difference between the transmissivity of the transmission mode and the transmissivity of the scattering mode is 30% or more, 32% or more, 34% or more, 36% or more, 38% or more, 40% or more, 42% . The liquid crystal cell can exhibit excellent transmittance variable characteristics as described above by employing the liquid crystal layer exhibiting the above-mentioned specific resistance and conductivity characteristics.

The liquid crystal cell may further include an anisotropic dye in the liquid crystal layer. The anisotropic dye can improve the light transmittance characteristic of the liquid crystal cell, for example, and improve the transmittance variable characteristics. The term " dye " in the present application may mean a material 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. However, the dyes are not limited thereto, and suitable anisotropic dyes can be selected and used as needed.

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, 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% or less, 1.4 wt% 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.

When the liquid crystal layer contains an anisotropic dye, the liquid crystal cell can switch between the transmission mode and the scattering mode, which have excellent transmittance variable characteristics. For example, when the liquid crystal layer includes an anisotropic dye, the liquid crystal cell may have a transmittance of 60% or more and a haze of 10% or less with respect to light having a wavelength of 400 nm to 700 nm in the transmission mode. When the liquid crystal layer contains an anisotropic dye, the liquid crystal cell may have a transmittance of 50% or less with respect to light having a wavelength of 400 nm to 700 nm in a scattering mode, and a haze may be 90% or more. The haze and transmittance values may be measured by an ASTM method using, for example, a hazemeter (NDH-5000SP).

The liquid crystal cell may further include a polymer network in the liquid crystal layer. The polymer network may serve as a spacer, for example, to maintain a gap inside the liquid crystal layer. The polymer network may be in phase-separated form with the liquid crystal compound. The polymer network in the liquid crystal layer can be contained in the liquid crystal layer by, for example, a structure in which a polymer network is distributed in a continuous liquid crystal compound, a so-called PNLC (Polymer Network Liquid Crystal) structure, (PDLC) structure in which the liquid crystal layer exists in a state in which the liquid crystal layer is dispersed in the liquid crystal layer.

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.

The liquid crystal cell may further include suitable additives in the liquid crystal layer to control the resistivity or conductivity of the liquid crystal layer. Examples of the additive include ionic impurities, ionic liquids, salts, monomers having reactive functional groups, initiators, and anisotropic dyes. As the ionic impurities, for example, 2,2,6,6-Tetramethylpiperidine-1-Oxyl Free radical can be used. As the ionic liquid, for example, TMA-PF ₆ , BMIN-BF ₄ can be used ([1-butyl-3- methylimideazolium] BF 4), a salt with, for example, CTAB (Cetrimonium bromide), CTAI (Cetrimonium Iodide), CTAI3 (Cetrimonium triiodide) a can be used, reactive functional groups For example, a reactive mesogen having a mesogen functional group having good compatibility with a liquid crystal can be used. As the initiator, for example, TPO can be used, and an anisotropic dye For example, azo dyes such as X12 of BASF can be used, but the present invention is not limited thereto. When the additive is contained in the liquid crystal layer, the content ratio of the additive in the liquid crystal layer may be, for example, more than 0 wt% to 30 wt% or less. More specifically, the proportion of the additive in the liquid crystal layer is more than 0 wt% to 30 wt% or less, 25 wt% or less, 20 wt% or less, 15 wt% or less, 10 wt% or less, 5 wt% or less, 1 wt% , 0.8 wt% or less, 0.6 wt% or less, 0.4 wt% or less, 0.2 wt% or less, or 0.1 wt% or less. However, the content ratio of the additive is not limited to the above, but may be appropriately adjusted in consideration of the intrinsic resistivity of the liquid crystal compound contained in the liquid crystal layer and the resistivity or conductivity of the desired liquid crystal layer

The liquid crystal cell may further include an electrode layer. The electrode layer may be present on the side of the liquid crystal layer of the substrate. For example, the electrode layers 401 and 402 may exist on the side of the liquid crystal layer 102 of the two opposing substrates 1011 and 1012, as shown in Fig. As described above, when the alignment film exists on the side of the liquid crystal layer of the substrate, the substrate, the electrode layer, and the alignment film may be sequentially present. Such an electrode layer can be applied 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 appropriately patterned.

The present application also relates to the use of a liquid crystal cell. The exemplary liquid crystal cell is capable of realizing a normal transmission mode, is driven with a low driving voltage, and can exhibit excellent haze characteristics. 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, a transparent display shading plate, an active retarder for 3D image display, or a viewing angle adjusting film.

The exemplary liquid crystal cell is capable of realizing a normal transmission mode, is driven with a low driving voltage, and can exhibit excellent haze characteristics. 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, a transparent display shading plate, an active retarder for 3D image display, or a viewing angle adjusting film.

Fig. 1 exemplarily shows a liquid crystal cell.
Fig. 2 is a schematic diagram of measurement of horizontal conductivity and vertical conductivity.
Figs. 3 to 4 show an exemplary liquid crystal cell.
FIG. 5 is a graph showing haze trends of liquid crystal cells according to Examples 1 to 4 and Comparative Examples 1 and 2 with respect to measured values of horizontal conductivity. FIG.
FIG. 6 is a graph showing haze trends of the liquid crystal cells of Examples 1 to 4 and Comparative Examples 1 and 2 with respect to the horizontal conductivity converted value. FIG.
7 is an image of a transmission mode (A) and a haze mode (B) of Comparative Example 5. Fig.
8 is an image of the transmission mode (A) and the haze mode (B) of the thirteenth embodiment.

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. Conductivity and resistivity evaluation

The liquid crystal cell manufactured in Examples and Comparative Examples was measured for room temperature conductivity using a LCR meter (E4980A, Agilent) under the conditions of a measurement frequency of 60 Hz and a measurement voltage of 0.5. The horizontal conductivity (σ //) was measured by applying a voltage to a vertically aligned liquid crystal layer, that is, a voltage in the thickness direction of the liquid crystal layer. The vertical conductivity (σ⊥) . The liquid crystal cell having an area of 2.2 cm x 4.0 cm and an interval of 9 m was measured the measured conductivity [? _ Actual] at room temperature according to the above method, and the resistance [R] value was derived from the following equation The resistivity and the conductivity converted into the area of 1.0 cm ² and the interval of 1 cm for the liquid crystal cell were determined by the formulas D and E, respectively. In the following, the electrode area [A] and the interelectrode distance [L] correspond to the area and the interval of the liquid crystal cell, respectively.

[Formula C]

Resistance [R] = 1 / electric conductivity [? _ Actual]

[Formula D]

Resistance [R] = Resistance [rho] x Electrode area [A] / Electrode distance [L]

[Formula E]

Converted electrical conductivity = 1 / resistivity [rho]

2. Hayes  And transmittance evaluation

The haze and the transmittance of the liquid crystal cell prepared in Examples and Comparative Examples were measured by ASTM method using a haze meter, NDH-5000SP. That is, the light is transmitted through the measurement object and enters the integrating sphere. In this process, the light is diffused by the measurement object (DT, meaning the sum of all light emitted and diffused) and parallel light (PT, Direction, which light is condensed in the light receiving element in the integrating sphere, and the haze can be measured through the condensed light. That is, the total transmitted light TT according to the above process is the sum DT + PT of the diffused light DT and the parallel light PT, and the haze is the percentage of the diffused light with respect to the total transmitted light (Haze (%) = 100XDT / TT). In the following test example, the total transmittance refers to the total transmitted light (TT), and the linear transmittance refers to the parallel light (PT).

Example  One

Two polycarbonate films, in which an ITO (Indium Tin Oxide) transparent electrode layer and a vertical alignment film are sequentially formed, are spaced apart from each other such that the vertical alignment films face each other with a gap of about 9 mu m, A liquid crystal composition was injected between the PC films and the edges were sealed to fabricate a liquid crystal cell having an area of 2.2 cm x 4.0 cm and an interval of 9 m. As the vertical alignment layer, a vertical alignment composition (Nissan 5661) was coated on the ITO transparent electrode layer and fired at a temperature of 100 ° C or more for 5 minutes or more was used. The liquid crystal composition was prepared by mixing a commercially available liquid crystal (HNG730600-200, product of HCCH, dielectric anisotropy: -5.0, specific resistance: 10 ¹¹ ) and CTAI3 (Cetrimonium triiodide) in a weight ratio of 99.9: 0.1 (commercial liquid crystal: CTAI3) .

Example  2

Except that a liquid crystal composition in which a commercial liquid crystal (HNG730600-200, manufactured by HCCH, dielectric anisotropy: -5.0, resistivity: 10 ¹¹ ) and CTAB (Cetrimonium triiodide) were mixed in a weight ratio of 99.5: 0.05 (commercial liquid crystal: CTAB) , A liquid crystal cell was prepared in the same manner as in Example 1.

Example  3

Commercial liquid crystal (HNG730600-200, HCCH社claim, dielectric anisotropy: -5.0, specific resistance: 10 ¹¹⁾ and the ionic liquid _{(BMIN-BF 4) 99.9:} 0.1 ( commercially available liquid crystal: BMIN-BF ₄₎ mixed at a weight ratio of A liquid crystal cell was prepared in the same manner as in Example 1 except that one liquid crystal composition was used.

Example  4

Commercial liquid crystal mixture in a weight ratio of (HNG730600-200, HCCH社claim, dielectric anisotropy: -5.0, specific resistance: 10 ¹¹⁾ and the ionic liquid (TMA-PF ₆₎ a 99.9:: 0.1 (TMA-PF 6 commercially available liquid crystal) A liquid crystal cell was prepared in the same manner as in Example 1 except that one liquid crystal composition was used.

Comparative Example  One

Commercial liquid crystal (HPC216000, HCCH社claim, dielectric anisotropy: 17, specific resistance: 10 ¹²⁾ and the commercial liquid crystal (MT-13-1422, Merck社claim, dielectric anisotropy: 23, specific resistance: 10 ^13), a 70:30 (HPC216000 : MT-13-1422) was used in place of the liquid crystal composition of Example 1, and a liquid crystal cell was prepared in the same manner as in Example 1.

Comparative Example  2

(Liquid crystal anisotropy: 17, specific resistance: 10 ¹² ) and commercial liquid crystal (MT-13-1422, made by Merck, dielectric constant anisotropy: -5, resistivity: 10 ¹³ ) at 30:70 (HPC216000, : MT-13-1422) was used in place of the liquid crystal composition of Example 1, and a liquid crystal cell was prepared in the same manner as in Example 1.

Test Example  1. Resistivity and Conductivity Hayes  evaluation

The horizontal conductivity (σ //) of the liquid crystal cell of each of Examples 1 to 4 and Comparative Examples 1 and 2 and the measured value of horizontal resistance (σ //) and resistance (R) measured by the above- (ρ //) and haze by applying voltage to the liquid crystal layer in the initial vertical state were measured, and the results are shown in Table 1 below. The haze was measured while connecting an AC power source (frequency: 60 Hz and a vertical electric field of voltage: 100 V) to the ITO transparent electrode layer of the upper and lower substrates of the manufactured liquid crystal cell.

As shown in Table 1, in the case of Examples 1 to 4, in which the resistivity (ρ //) was 5.0E + 09 Ω · cm or less and the conductivity (σ //) was 5.0E-04 μS / cm or more, The haze expressed is higher than that shown in FIGS. 4 and 5, and it can be confirmed that the haze has a linear relationship with respect to the electric conductivity value. (In Figs. 5 and 6, R ² is set to the x coordinate as a horizontal conductivity (σ //) Measured value (Fig. 5) and a horizontal conductivity (σ //) in terms of value (Figure 6), and the y coordinate haze (FIG. 5) and y = 81660x + 6.9903 (FIG. 6) when the values of x and y are set to be 1, when R ² is 1 100%, and it can be seen that according to FIG. 5 and FIG. 6, it corresponds to 97.71% in the above formula).

Actual data Conversion data Hayes σ // [S] R // [Ω] σ // [μS / cm] ρ // [Ω · cm] Example 1
(LC4) 9.34E-06 1.07E + 05 9.55E-04 1.05E + 9 91.51% Example 2
(LC5) 8.60E-06 1.16E + 05 8.80E-04 1.14E + 9 70.87% Example 3
(LC2) 9.80E-07 1.02E + 06 1.00E-04 9.10E + 9 19.6% Example 4
(LC1) 1.07E-06 9.35E + 05 1.09E-04 9.98E + 9 19.08% Comparative Example 1
(LC6) 5.56E-08 1.77E + 07 5.78E-06 1.73E + 11 5.66% Comparative Example 2
(LC3) 4.53E-08 2.21E + 07 4.63E-06 2.16E + 11 3.02%

Example  5 to 12 and Comparative Example  3 to 4

Two polycarbonate films, in which an ITO (Indium Tin Oxide) transparent electrode layer and a vertical alignment film are sequentially formed, are spaced apart from each other such that the vertical alignment films face each other with a gap of about 9 mu m, A liquid crystal composition was injected between the PC films and the edges were sealed to prepare liquid crystal cells of Examples 5 to 12 and Comparative Examples 3 to 4 having an area of 2.2 cm x 4.0 cm and an interval of 9 m. The compositions of the liquid crystal compositions of Examples 5 to 12 and Comparative Examples 3 to 4 are shown in Table 2 below.

Liquid crystal composition
(LC: additive = 90% by weight: 10% by weight) LC additive Example 5 (No. 1) LC1 RM1 Example 6 (No. 2) LC1 RM2 Comparative Example 3 (No. 3) LC2 RM3 Comparative Example 4 (No. 4) LC2 RM4 Example 7 (No. 5) LC1 RM2 + Dye + initiator
(Weight ratio of 10: 1: 0.3) Example 8 (No. 6) LC2 RM1 + Dye + initiator
(Weight ratio of 10: 1: 0.3) Example 9 (No. 7) LC2 RM2 + Dye + initiator
(Weight ratio of 10: 1: 0.3) Example 10 (No. 8) LC3 RM1 + Dye + initiator
(Weight ratio of 10: 1: 0.3) Example 11 (No. 9) LC3 RM2 + Dye + initiator
(Weight ratio of 10: 1: 0.3) Example 12 (No. 10) LC3 CTAI3

RM2:

RM3:

RM4:

Dye: X12, BASF社제
개시제: Igacure 651,Ciba社제 LC1: HNG715600, manufactured by HCCH, dielectric constant anisotropy: -5.0 and resistivity: 10 ¹² )
LC2: HNG218000, manufactured by HCCH, dielectric constant anisotropy: -12.0 and resistivity: 10 ¹² )
LC3: HNG726200, manufactured by HCCH, dielectric anisotropy: -4.0 and resistivity: 10 ¹² )
RM1:

RM2:

RM3:

RM4:

Dye: X12, manufactured by BASF
Initiator: Igacure 651, manufactured by Ciba

Test Example  2. Depending on the conductivity ratio Hayes  evaluation

The ratio of the vertical conductivity and the horizontal conductivity derived from the vertical conductivity (σ⊥) and the horizontal conductivity (σ //) of the liquid crystal layer measured by the above-described method for the liquid crystal cell of Examples 5 to 12 and Comparative Examples 3 to 4 Are shown in Table 3 below. The haze of the liquid crystal layer in the initial vertical alignment state and the initial horizontal alignment state is shown in Table 3 below. Haze was measured by connecting an AC power source (frequency: 60 Hz and a voltage: 60 V to 100 V vertical electric field) to the ITO transparent electrode layer of the upper and lower substrates while driving the manufactured liquid crystal cell.

Conductivity characteristics Haze according to initial alignment state σ // ÷ σ⊥ σ⊥ ÷ σ // In vertical orientation
Haze (%) Horizontal orientation
Haze (%) Example 5 (No. 1) 1.4 0.7 93.5 93.5 Example 6 (No. 2) 1.6 0.6 79.1 84.0 Example 7 (No. 5) 2.1 0.5 92.6 94.4 Example 8 (No. 6) 3.0 0.1 93.5 95.5 Example 9 (No. 7) 2.4 0.4 87.8 95.6 Example 10 (No. 8) 2.1 0.5 94.9 95.6 Example 11 (No. 9) 3.1 0.3 93.2 94.9 Example 12 (No. 10) 2.4 0.4 69.3 91.0 Comparative Example 3 (No. 3) 0.9 1.1 57.4 76.5 Comparative Example 4 (No. 4) 0.9 1.1 42.1 73.7 σ // ÷ σ⊥: ratio of horizontal conductivity to vertical conductivity
σ⊥ ÷ σ //: ratio of vertical conductivity to horizontal conductivity

Test Example  3. Driving voltage, transmittance and Hayes  evaluation

An AC power source (Example 13: application of a vertical electric field of a frequency of 60 Hz and a voltage of 60 V, and a voltage of 60 V) was applied to the ITO transparent electrode layers of the upper and lower substrates of the liquid crystal cell in the initial vertical alignment state of Example 13 and Comparative Example 5 formed in a normal transmission mode (Normally Transparent Mode) Comparative Example 5: With a vertical electric field of 60 Hz and a voltage of 120 V), the total transmittance, the linear transmittance and the haze measured in the transmission mode and the haze mode after switching to the haze mode are shown in Table 4, Mode and the haze mode are shown in Figs. 7 and 8 (A: transmission mode and B: haze mode), respectively.

Example 13 Comparative Example 5 OFF state
(Transmission mode) Total transmittance 72.2% 68% Straight Transmittance 71.9% 66.5% Hayes 0.4% 1.5%
ON state
(Haze mode) Driving voltage 60V 120V Total transmittance 28.0% 40% Straight Transmittance 1.3% 2.9% Hayes 95.5% 93.0% Transmittance difference ΔT
(Total transmittance difference between OFF state and ON state) 44.2% 28.0%

1011 and 1012: two substrates arranged opposite to each other
102: liquid crystal layer
201: liquid crystal compound
E: Electric field
301, 302:
401, 402: electrode layer

Claims (19)

Two substrates arranged opposite to each other; And is present between the two substrates, and the specific resistance is 1.0 x 10 Ω · ⁺¹⁰ liquid crystal cell (provided that the specific resistance, including cm or less liquid crystal layer is a room temperature resistivity in terms of the reference area and the distance of 1cm 1cm ² ). The liquid crystal cell according to claim 1, wherein the liquid crystal layer comprises a nematic liquid crystal compound. The liquid crystal cell according to claim 1, wherein the liquid crystal layer in the initial state is in a vertically aligned state. The liquid crystal cell according to claim 1, wherein the liquid crystal layer in the initial state is in a horizontally aligned state. The liquid crystal display device according to claim 1, wherein the liquid crystal cell has a horizontal conductivity (σ //) or a vertical conductivity (σ⊥) of 1.0 × 10 ^-4 μS / cm or more (note that the horizontal conductivity and the vertical conductivity are 1 cm ² Lt; 0 > C). The liquid crystal display device according to claim 1, wherein the ratio (? //? /?) Of the horizontal conductivity (? //) to the vertical conductivity (??) Of the liquid crystal layer is 0.2 or more and the horizontal conductivity Of the vertical conductivity (??) To the vertical conductivity (?? /??) Of 2.0 or less (provided that the conductivity ratio is an area of 1 cm ² and a room temperature conductivity ratio converted on the basis of an interval of 1 cm). The liquid crystal display device according to claim 1, wherein the ratio (? //? /?) Of the horizontal conductivity (? //) to the vertical conductivity (??) Of the liquid crystal layer is 0.7 or more and the horizontal conductivity Of the vertical conductivity (??) To the vertical conductivity (??) Is 1.0 or less (provided that the conductivity ratio is an area of 1 cm ² and a room temperature conductivity ratio converted on the basis of an interval of 1 cm). The liquid crystal cell according to claim 1, wherein the transmittance is 80% or more and the haze is 10% or less with respect to light having a wavelength of 400 nm to 700 nm in an initial state. The liquid crystal cell according to claim 8, wherein the liquid crystal cell is switched to a scattering mode having a transmittance of 75% or more and a haze of 90% or more with respect to light having a wavelength of 400 nm to 700 nm by external energy application. The liquid crystal cell according to claim 1, wherein the liquid crystal layer further comprises an anisotropic dye. The liquid crystal cell according to claim 10, wherein the transmission mode is a transmission mode in which the transmittance to light having a wavelength of 400 nm to 700 nm is 60% or more and the haze is 10% or less in the initial state. 12. The liquid crystal cell according to claim 11, wherein the liquid crystal cell is switched to a scattering mode having a transmittance of 50% or less and a haze of 90% or more with respect to light having a wavelength of 400 nm to 700 nm by external energy application. 11. The liquid crystal cell according to claim 10, wherein the anisotropic dye is a black dye. The liquid crystal cell according to claim 1, wherein the liquid crystal layer further comprises an ionic impurity, an ionic liquid, a salt, a monomer having a reactive functional group, or an initiator. The liquid crystal cell of claim 1, wherein the liquid crystal layer further comprises a polymer network. The liquid crystal cell according to claim 1, further comprising an orientation film existing on a side of the liquid crystal layer of the substrate. The liquid crystal cell according to claim 1, further comprising an electrode layer present on a side of the liquid crystal layer of the substrate. 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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