KR20190037955A - Optical Device - Google Patents

Abstract

The present application relates to an optical element, a transmittance variable device, and uses thereof. In one example of the present application, a back flow phenomenon by the bulk crystal host is suppressed even when a cell gap of a GH cell becomes thick, thereby being capable of providing the optical element having excellent response speed and driving characteristics, and a variable transmittance device including the same.

Description

[0001]

The present application relates to an optical element.

A transmittance variable device using a so-called GH cell (Guest host cell), which is a mixture of a liquid crystal host, which is a liquid crystal compound, and a dichroic dye guest, is known (for example, Patent Document 1).

Such a transmittance variable device is applied to various applications including eyewear such as sunglasses, outer wall of a building, sunroof of a vehicle, and the like. In recent years, application of the transmittance variable element to eyewear for the so-called Augmented Reality (AR) experience has been studied.

Such a transmittance variable device adjusts the transmittance by adjusting the orientation of the dichroic dye guest in the GH cell. For example, when the transmittance is adjusted by switching the orientation of the liquid crystal host between the vertically and horizontally aligned states .

European Patent No. 0022311

The present application aims at providing an optical element. In one example, the present invention provides a liquid crystal display device capable of suppressing a back flow phenomenon by a bulk liquid crystal compound even when a cell gap of a liquid crystal layer becomes thick, And an object thereof is to provide a device.

The present application is directed to optical elements. The optical element of the present application can form a variable transmittance device, alone or in combination with other elements. The term transmittance variable device may mean a device designed to switch between a state of high transmittance and a state of low transmittance.

In this specification, the high transmittance state can be referred to as a transmission state, and the low transmittance state can be referred to as a blocking state.

The transmission state may mean, for example, a state where the transmittance of the apparatus is 40% or more, and the cutoff state may mean a state where the transmittance of the apparatus is 10% or less.

The higher the numerical value is, the better the transmittance in the transparent state is, and the lower the transmittance in the blocking state is, the better the upper and lower limits are not particularly limited. In one example, the upper limit of the transmittance in the transmissive state can be about 100%, about 95%, about 90%, about 85%, about 80%, about 75%, about 70%, about 65% . In another embodiment, the transmittance in the transmitted state is at least about 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80% Or 95% or more. The lower limit of the transmittance in the blocking state may be about 0%, about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7% 10%. ≪ / RTI >

The transmittance may be a linear light transmittance. The term linear optical transmittance may be a ratio of the light (linear light) transmitted through the transmittance variable device in the same direction as the incident direction with respect to the light incident on the transmittance variable device in a predetermined direction. In one example, the transmittance may be a result (normal linear light transmittance) measured with respect to light incident in a direction parallel to the surface normal of the transmittance varying device, or an angle exceeding 0 degrees and within 20 degrees with the surface normal (Oblique light transmittance) measured with respect to the light incident in the direction of the incident light. The angle of incidence of the incident light with respect to the surface normal for the measurement of the oblique light transmittance may be about 0.5 degree or more, about 1 degree or more, or about 1.5 degree or more, about 19.5 degrees or less, about 19 degrees or less, About 18.5 degrees, about 17 degrees, about 17 degrees, about 16.5 degrees, about 16 degrees, about 15.5 degrees, about 15 degrees, about 14.5 degrees, about 14 degrees, about About 13.5 degrees, about 13.5 degrees, about 12.5 degrees, about 12 degrees, about 11.5 degrees, about 11 degrees, about 10.5 degrees, about 10 degrees, about 9.5 degrees, about 9 degrees, about About 8 degrees or less, about 7.5 degrees or less, about 7 degrees or less, about 6.5 degrees or less, about 6 degrees or less, about 5.5 degrees or less, about 5 degrees or less, about 4.5 degrees or less, Can be less than 3.5 degrees or less than about 3 degrees

The transmittance may be a numerical value for light of any wavelength within a wavelength range of visible light, that is, a wavelength range of 400 to 700 nm, or an average value of numerical values for light of the whole wavelength.

Further, the linear light transmittance in each of the above-mentioned transmission states is a transmittance in a state in which the transmittance of the transmittance variable apparatus is the highest, and the linear transmittance in the cutoff state is a transmittance in a state where the transmittance of the transmittance variable apparatus is lowest .

The optical element of the present invention includes at least an active liquid crystal layer. In one example, the active liquid crystal layer is an active guest host liquid crystal layer (hereinafter, referred to as an active GH layer) . The active GH layer may be a liquid crystal compound (liquid crystal host), a liquid crystal compound (liquid crystal host), or the like. The active liquid crystal layer is a liquid crystal layer containing at least a liquid crystal compound and capable of changing the direction of the optical axis of the liquid crystal by an external signal, And a dichroic dye guest, and can also mean a liquid crystal layer formed so that the direction of the optical axis can be changed by an external signal, for example, a voltage.

Hereinafter, for the sake of convenience, the active liquid crystal layer is described as an active GH layer, but the active GH layer may also be applied to the active liquid crystal layer.

In this case, the optical axis means an optical axis or a slow axis of a liquid crystal compound of the active liquid crystal layer or the GH layer, and the direction of the major axis when the liquid crystal compound is a rod, In the case of a discotic liquid crystal, it may mean an axis parallel to the normal direction of the disc plane.

The orientation of the dichroic dye contained in the GH layer is determined by the liquid crystal compound by a mechanism known as the so-called guest host effect.

The optical axis of the active GH layer can switch between a vertically aligned state and a horizontally aligned state.

The vertical alignment state is a state in which the optical axis or the average optical axis of the active liquid crystal layer or the GH layer is within a range of -10 degrees to -10 degrees, -8 degrees to 8 degrees, and -6 degrees to the normal direction of the plane of the GH layer, Means an angle within a range of -4 degrees to 4 degrees, an angle within a range of -2 degrees to 2 degrees, or substantially parallel to each other. The horizontal alignment state is a state in which the optical axis or the average optical axis of the active liquid crystal layer or the GH layer is within a range of approximately -10 degrees to 10 degrees from the direction perpendicular to the normal direction of the liquid crystal layer or the GH layer, Means an angle within a range of -6 to 6 degrees, a range of -4 to 4 degrees, a range of -2 to 2 degrees, or substantially parallel.

The average optical axis may be the vector sum of the optical axes of the liquid crystal compound of the active liquid crystal layer or the GH layer.

In one example, the active liquid crystal layer or the GH layer of the optical element is present in the vertically aligned state in the state where no external signal such as a voltage is applied, and is switched to the horizontally aligned state when an external signal is applied. And when the external signal is applied, it is switched to the vertically aligned state, and when the external signal is no longer present, it is switched to the horizontally aligned state. .

The ratio (d / p) of the thickness (d) of the active liquid crystal layer or GH layer to the pitch (p) of the liquid crystal compound in the vertically aligned state in the optical element may be within a range of 0.1 to 0.2. The ratio d / p may be about 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more or 0.155 or more, 0.19 or less, 0.18 or less or 0.17 or less in other examples.

The thickness d of the GH layer is the same as the cell gap of the GH layer. For example, when the two substrates and the GH layer are formed therebetween as described later, The distance between the opposing surfaces of the first and second plates 22, 24,

The pitch (p) of the liquid crystal compound can be measured by a measuring method using a wedge cell, and specifically, a simple method for determining the cholesteric pitch using a D. strike-wedge Grandjean-Cano cell (Liquid Crystals, Vol. 35, No. 7, July 2008, 789-791).

By controlling the ratio d / p between the cell gap d and the pitch p as described above, even when the cell gap becomes thick, for example, even when the liquid crystal is not controlled by the orientation layer due to the orientation layer or external signals, The layer (the liquid crystal layer) can be minimized and a fast response speed and a wide transmittance band can be achieved. In the above, the transmittance band means the difference between the maximum transmittance and the minimum transmittance that the optical element can exhibit. If the ratio d / p becomes too low, the response speed may decrease, and if the ratio d / p has an excessively high value, the twist alignment state of the undesired liquid crystal compound may be induced in the horizontal alignment state.

In this state, the thickness of the GH layer, that is, the cell gap may be about 4 탆 or more. The thicker the GH layer is, the wider the transmittance band can be realized, but in this case the ratio of the bulk liquid crystal layer becomes higher. However, under the above ratio (d / p), the ratio of the bulk liquid crystal layer can be minimized or suppressed even under a thick cell gap, and an optical element with excellent characteristics can be provided.

The cell gap may be at least about 5 占 퐉, at least 6 占 퐉, at least 7 占 퐉, at least 8 占 퐉, at least 9 占 퐉, at least 10 占 퐉, at least 11 占 퐉, at least 12 占 퐉, at least 13 占 퐉, Less than or equal to 30 μm, less than or equal to 29 μm, less than or equal to 28 μm, less than or equal to 27 μm, less than or equal to 26 μm, less than or equal to 25 μm, less than or equal to 24 μm, less than or equal to 23 μm, less than or equal to 22 μm, , 18 μm or less, 17 μm or less, 16 μm or less, or 16.5 μm or less.

The ratio (d / p) can be achieved, for example, by introducing an appropriate amount of a chiral dopant into the GH layer.

The kind of the chiral dopant that can be applied is not limited and can be used without particular limitation as long as it can secure the desired pitch without damaging the liquid crystallinity (for example, nematic regularity) of the liquid crystal compound. The chiral dopant needs to include at least the chirality in the molecular structure. As the chiral dopant, for example, a compound having one or two or more asymmetric carbons, a compound having an asymmetric point on a hetero atom such as a chiral amine or a chiral sulfoxide, or a compound having an asymmetric carbon atom a compound having an axially asymmetric (optically active site) with a shrinking agent such as cumulene or binaphthol may be exemplified. As the chiral dopant, a commercially available chiral nematic liquid crystal, for example, Chiral dopant liquid crystal S-811 of Merck or LC756 of BASF may be used.

The application ratio of the chiral dopant is not particularly limited as it is selected so as to achieve the above ratio (d / p). In general, the content (% by weight) of the chiral dopant is calculated by a formula of 100 / (Helixcal Twisting power) × pitch (nm), and a proper ratio can be selected in consideration of the desired pitch with reference to this method .

The kind of the liquid crystal compound contained in the active GH layer is not limited, and a known liquid crystal compound known to be capable of forming a GH cell can be applied. For example, a nematic liquid crystal compound can be used as the liquid crystal compound. The liquid crystal compound may be a non-reactive liquid crystal compound. The non-reactive liquid crystal compound may mean a liquid crystal compound having no polymerizable group. Examples of the polymerizable group include acryloyl groups, acryloyloxy groups, methacryloyl groups, methacryloyloxy groups, carboxyl groups, hydroxyl groups, vinyl groups, and epoxy groups, but not limited thereto, May be included.

The liquid crystal compound contained in the GH layer may have a positive dielectric anisotropy or a negative dielectric anisotropy. The term " dielectric anisotropy " in the present application can mean a difference between an ideal dielectric constant (epsilon e, extraordinary dielectric anisotropy) and a normal dielectric anisotropy (dielectric constant in short axis direction). The dielectric anisotropy of the liquid crystal compound may be within ± 40, within ± 30, within ± 10, within ± 7, within ± 5 or within ± 3, for example. Adjusting the dielectric anisotropy of the liquid crystal compound within the above range may be advantageous in terms of driving efficiency of the liquid crystal device.

The refractive index anisotropy of the liquid crystal compound present in the GH layer can be appropriately selected in consideration of the object physical properties, for example, the transmission characteristics, the contrast ratio, and the like. The term " refractive index anisotropy " may mean a difference between an extraordinary refractive index and an ordinary 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.

The GH layer further comprises a dichroic dye. The dye may be included as a guest material. The dichroic dye can serve, for example, to control the transmittance of the device in accordance with the orientation of the host material. 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 " dichroic 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 dichroic dye, for example, known dyes known to have properties that can be aligned according to the alignment state of the liquid crystal compound by a so-called host guest effect can be selected and used. Examples of such dichroic dyes include so-called azo dyes, anthraquinone dyes, methine dyes, azomethine dyes, merocyanine dyes, naphthoquinone dyes, tetrazine dyes, phenylene dyes, quaterlylene dyes, benzothiadiazole dyes , Diketopyrrolopyrrole dyes, squalene dyes or pyromethene dyes. However, the dyes applicable in the present application are not limited to the above. As the dichroic 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 dichroic dye preferably has a dichroic ratio, that is, a value obtained by dividing the absorption of the polarized light parallel to the long axis direction of the dichroic dye by the absorption of the polarized light parallel to the direction perpendicular to the long axis direction, 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 dichroic dye in the GH layer can be appropriately selected in accordance with the objective properties, for example, the transmittance variable characteristics. For example, the dichroic 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, % Or more, 0.9 wt% or more, or 1.0 wt% or more in the GH layer. The upper limit of the proportion of the dichroic dye in the GH 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.

The total weight of the liquid crystal compound and the dichroic dye in the GH layer may be, for example, about 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 At least 90 wt%, or at least 95 wt%, and in other instances less than about 100 wt%, 98 wt% or less, or 96 wt% or less.

The GH layer may further comprise optional additives used in forming the known GH layers, if necessary, in addition to the components, i.e. liquid crystal compounds, dichroic dyes and chiral dopants.

The GH layer may have an anisotropic degree (R) of, for example, about 0.5 or more. The anisotropy (R) can be measured by the method described in "Polarized Light in Optics and Spectroscopy", D. S. Kliger et al., Academic Press, 1990.

The anisotropy (R) may, in another example, be at least about 0.55, at least 0.6, or at least 0.65. The anisotropy (R) may be, for example, about 0.9 or less, about 0.85 or less, about 0.8 or less, about 0.75 or less, or about 0.7 or less.

The anisotropy (R) can be achieved by controlling, for example, the kind and / or ratio of the liquid crystal compound (host), the kind and / or the ratio of the anisotropic dye, the cell gap and the like.

The GH layer may be designed to have a pre-tilt angle in a predetermined range in the vertically aligned state.

The pretilt angle may mean an angle formed by the direction of the director of the liquid crystal compound with the plane of the GH layer.

The method of controlling the pretilt angle of such a liquid crystal compound is not particularly limited and can be controlled by a known method.

The pretilt angle may be, for example, 70 degrees or more and less than 90 degrees. By setting the pre-tilt angle, it is possible to provide an optical element having a broader transmittance band and excellent response speed and drive characteristics.

The pretilt angle may be at least about 71 degrees, at least about 72 degrees, at least about 73 degrees, at least about 74 degrees, at least about 75 degrees, at least about 76 degrees, at least about 77 degrees, at least about 78 degrees, at least about 79 degrees, at least about 80 degrees , About 81 degrees, about 82 degrees, about 83 degrees, about 84 degrees, about 85 degrees, about 86 degrees, about 87 degrees, about 89 degrees, about 88.5 degrees, Or less.

The optical element may further include various other elements including at least the GH layer.

In one example, the optical element may include first and second substrates disposed opposite to each other, wherein the GH layer may be positioned between the first and second substrates.

As the substrate, known materials can be used without any particular limitation. For example, the substrate may be a glass film, a crystalline or amorphous silicon film, an inorganic film such as quartz or ITO (Indium Tin Oxide) film, or a plastic film.

As the plastic substrate, a TAC (triacetyl cellulose) substrate; A COP (cyclo olefin copolymer) substrate such as a norbornene derivative substrate; (PMMA) substrate, a polycarbonate substrate, a polyethylene (PE) substrate, a polypropylene (PV) substrate, a polyvinyl alcohol (PVA) substrate, a diacetyl cellulose (DAC) substrate, a poly ether sulfone substrate, a polyetheretherketone (PEEK) substrate, a polyetheretherketone (PPS) substrate, a polyetherimide (PEN) substrate, a polyethylenemaphthatate (PEN) substrate, a polyethyleneterephtalate (PET) substrate, a polyimide (PS) A substrate or a substrate including an amorphous fluororesin can be used but is not limited thereto. The thickness of such a substrate is not particularly limited and may be selected within an appropriate range.

An electrode layer may be present on the substrate. For example, an electrode layer may be present on at least one surface or both surfaces of the surface of the substrate facing the GH layer. This electrode layer may be an element for applying an external signal capable of switching the optical axis of the GH layer. The term " inner surface " of the substrate in this application means a surface near both the GH layer and the both surfaces of the substrate.

The electrode layer may be formed using a known material. For example, the electrode layer may include 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.

A liquid crystal alignment layer may be present on the substrate. The liquid crystal alignment layer may also be formed on an inner surface of the substrate, that is, a surface facing the GH layer. When the above-mentioned electrode layer exists on the substrate, the liquid crystal alignment layer may be formed on the surface of the electrode layer, or may be formed between the electrode layer and the substrate. For example, a liquid crystal alignment layer may be present on at least one surface or both surfaces of the inner surface of the substrate included in the transmittance variable device.

As the alignment layer, various rubbing alignment layers or photo alignment layers known in the art can be used without any particular limitation. The alignment layer may be a horizontal alignment layer or a vertical alignment layer, and in one example, it may be a vertical alignment layer.

The optical element may further include known elements such as an antireflection layer and a hard coating layer in addition to the above-described structure.

The present application also relates to a transmittance variable device. The term transmissive variable device may refer to a device designed to switch between a transmissive state and a blocked state as described above.

The transmittance variable device may be constituted by the above-mentioned optical element alone, or may include other elements. The kind of the other element is not particularly limited and may be, for example, a passive polarization layer or an active GH layer (hereinafter referred to as a second active GH layer for the sake of distinction from an active GH layer of an optical element) . As the passive polarization layer, for example, a known linear polarizer such as a PVA (polyvinyl alcohol) polarizer can be used. The passive polarization layer or the active GH layer may be disposed to overlap with the optical element. For example, in the transmission state, the optical axis of the active GH layer of the optical element of the present application can be maintained parallel to the absorption axis of the passive polarization layer, or the active GH layer can be vertically aligned, The optical axis of the GH layer can be vertically aligned with the absorption axis of the passive polarization layer to maintain the transmission and blocking state.

When the optical element and the second active GH layer are included, in the transmission state, the optical axis of the active GH layer of the optical element and the second active GH layer are maintained in a mutually vertically aligned state, or one is in a vertically aligned state, Can be horizontally aligned so that the optical axes of the two GH layers can be aligned horizontally, and the optical axes of the two GH layers can be oriented perpendicular to each other in the blocking state.

As the second active GH layer, it is possible to use a GH layer of the same kind as that contained in the previously described optical element, or to use another known active GH layer. This second active GH layer can also switch between a vertically oriented state and a horizontally oriented state.

Hereinafter, a case where the transmittance variable device includes the optical element and the second active GH layer will be exemplified. In this case, for convenience, the GH layer included in the optical element may be referred to as a first active GH layer.

In the structure including the two active GH layers as described above, switching between the transmission and blocking states can be made by controlling the orientation of the dichroic dye in each active GH layer.

The first and second active GH layers may be overlapped with each other. Accordingly, the light transmitted through the first active GH layer can be incident on the second active GH layer, and conversely, the light transmitted through the second active GH layer can be incident on the first active GH layer.

Fig. 1 is a diagram schematically showing the states of the first active GH layer 10 and the second active GH layer 20 superposed on each other as described above.

This structure may be referred to herein as a double cell structure.

The first and second active GH layers may switch between vertical and horizontal alignment states, respectively. In one example, switching between the vertical and horizontal alignment states can be performed by applying a voltage. For example, a voltage may be applied to the active GH layer in the vertically aligned state to switch to the horizontally oriented state, or conversely, to the vertically aligned state by applying a voltage to the horizontally oriented active GH layer.

In the horizontally oriented state, the optical axes of the first active GH layer and the second active GH layer form an angle within a range of about 85 degrees to 95 degrees, or may be orthogonal. In one example, as shown in FIG. 2, any of the first and second active GH layers 10 and 20, for example, the first active GH layer 10 in the horizontal alignment state, For example, the second active GH layer 20 has an optical axis OA in the range of 40 to 50 degrees clockwise with respect to the transverse axis WA of the active GH layer (OA) within a range of 130 degrees to 140 degrees in the clockwise direction on the basis of the optical axis OA. The optical axis relationship between the first active GH layer and the second active GH layer reduces the difference in the contrast ratio between the left and right viewing angles, thereby providing a variable transmissivity film having excellent symmetry.

In the present specification, the abscissa axis WA of the active GH layer is used to observe an observer or a display device wearing the eyewear when applied to a display device such as an eyewear or a TV, in a direction parallel to the long axis direction of the active GH layer It can mean a direction parallel to the line connecting the eyes of the observer.

As described above, the term " active GH layer " refers to a layer in which anisotropic dyes are arranged together according to the arrangement of liquid crystal compounds to form functional layers exhibiting anisotropic light absorption characteristics respectively with respect to the alignment direction of the anisotropic dyes and the direction perpendicular to the alignment direction It can mean. For example, an anisotropic dye is a substance whose absorption rate of light changes according to the direction of polarization. When an absorption rate of light polarized in the long axis direction is large, it is referred to as a p-type dye. When the absorption rate of polarized light in a short axis direction is large, can do. In one example, when a p-type dye is used, the polarized light vibrating in the longitudinal direction of the dye is absorbed and the polarized light vibrating in the direction of the short axis of the dye is less absorbed and can be transmitted. Unless otherwise specified, anisotropic dyes are assumed to be p-type dyes.

The active GH layer can function as an active polarizer. As used herein, the term " Active Polarizer " may refer to a functional element capable of controlling anisotropic light absorption according to external application. For example, the active GH layer can control the anisotropic light absorption of polarized light in the direction parallel to the arrangement direction of the anisotropic dye and polarization in the vertical direction by controlling the arrangement of the liquid crystal compound and the anisotropic dye. Since the arrangement of liquid crystal and anisotropic dyes can be controlled by the application of an external action such as a magnetic field or an electric field, the active GH layer can control anisotropic light absorption according to external action.

The transmittance variable device may further include two alignment layers disposed on both sides of the first active GH layer and the second active GH layer, respectively. In one example, the transmittance variable device comprises a first optical element and a third vertical alignment layer, a second active GH layer, and a second optical element sequentially including a first vertical alignment layer, a first active GH layer, and a second vertical alignment layer, And a fourth vertical alignment layer, wherein the first optical element may be the above-described optical element.

The transmittance of the first active GH layer and the second active GH layer can be adjusted by controlling the orientation of the first active GH layer and the second active GH layer when the voltage is not applied and / or when the voltage is applied. The alignment direction can be adjusted by adjusting the pretilt angle and the pretilt direction of the first to fourth vertical alignment layers.

Herein, the pretilt may have an angle and a direction. The pre-tilt angle may be referred to as a polar angle, and the pre-tilt direction may be referred to as an azimuthal angle.

The pre-tilt angle has the same meaning as the pre-tilt angle described in the optical element section.

In one example, the first to fourth vertical alignment layers are formed so that the pretilt angles are within the above-mentioned range, that is, 70 degrees or more and less than 90 degrees, or the pretilt angles of the various examples mentioned in the optical element item Lt; / RTI > It is possible to provide a variable transmittance device having an initial transmittance in this range.

In one example, the pre-tilt angle of the first vertical alignment layer is an angle measured clockwise or counterclockwise with respect to a plane parallel to the alignment layer, and the pre-tilt angle of the second vertical alignment layer is A counterclockwise direction when the pretilt angle of the first vertical alignment layer is measured in the clockwise direction, or a clockwise angle when the pretilt angle of the first vertical alignment layer is measured in the counterclockwise direction have.

The pretilt angle of the third vertical alignment layer is an angle measured in a clockwise or counterclockwise direction with respect to a plane parallel to the orientation layer, and the pretilt angle of the fourth vertical alignment layer is in a direction opposite to the pretilt angle, 3 may be a counterclockwise direction when the pretilt angle of the vertical orientation layer is measured in a clockwise direction or an angle measured in a clockwise direction when the pretilt angle of the third vertical orientation layer is measured in a counterclockwise direction.

The pretilt direction may mean a direction in which a director of the liquid crystal molecules is projected on a horizontal surface of the alignment layer. In one example, the pretilt direction may be an angle formed by the projected direction and the horizontal axis WA. The pretilt direction of the vertical alignment layer can induce the alignment direction of the horizontally aligned state when a voltage is applied to the liquid crystal cell

The pre-tilt directions of the first and second vertical alignment layers and the pre-tilt directions of the third and fourth vertical alignment layers may intersect with each other. In one example, the pre-tilt directions of the first and second vertical alignment layers and the pre-tilt directions of the third and fourth vertical alignment layers are orthogonal to each other, for example, from 85 degrees to 95 degrees or about 90 degrees . When the pretilt direction satisfies the above condition, it is possible to provide a variable transmittance device having a high light shielding ratio at the time of voltage application.

In one example, the direction of the pre-tilt of the first and second vertical alignment layers and the pretilt direction of the third and fourth vertical alignment layers, for example, the direction of the first and second vertical alignment layers The pretilt direction has an optical axis (OA) within a range of 40 degrees to 50 degrees in the clockwise direction with respect to the horizontal axis WA of the active GH layer, and has an optical axis OA in the other direction such as the third and fourth vertical orientations The pretilt direction of the layer may have an optical axis OA in the range of 130 to 140 degrees clockwise with respect to the transverse axis WA of the active GH layer. Through this relationship, it is possible to provide a variable transmittance device having a good symmetry by reducing the difference in contrast ratio between right and left viewing angles.

The pretilt angle and direction mentioned above may be a pretilt angle and a direction measured in each active GH layer in the case where the active GH layer of each active GH layer is in the vertical alignment state in one example.

The first to fourth vertical alignment layers may be a rubbing alignment layer or a photo alignment layer. In the case of the rubbing orientation layer, the orientation direction is determined by the rubbing direction, and in the case of the photo-alignment layer, by the polarization direction of the irradiated light. The pretilt angle and the pretilt direction of the vertical alignment layer can be adjusted by changing the alignment condition, for example, the rubbing condition or the pressure condition at the time of the rubbing alignment or the light alignment condition, for example, the polarization state of light, Can be realized by appropriately adjusting.

For example, when the vertical alignment layer is a rubbing orientation layer, the pretilt angle can be achieved by controlling the rubbing intensity of the rubbing orientation layer, and the pretilt direction can be achieved by controlling the rubbing direction of the rubbing orientation layer And this approach is well known. Further, in the case of the photo-alignment layer, it can be achieved by the orientation layer material, direction, state or intensity of polarization applied to the orientation.

In one example, the first to fourth vertical alignment layers may be rubbing orientation layers. Each of the first to fourth vertical alignment layers may have a specific alignment direction.

For example, the rubbing directions of the first and second vertical alignment layers may be opposite to each other to about 170 to 190 degrees, and the rubbing directions of the third and fourth vertical alignment layers may also be about 170 Lt; RTI ID = 0.0 > 190 C. < / RTI >

The rubbing direction can be confirmed by measuring the pretilt angle. In general, since the liquid crystal lays along the rubbing direction and generates a pretilt angle, the pretilt angle is measured in the manner described in the following examples, Measurement may be possible.

3, the direction RA of the rubbing orientation of the first vertical alignment layer 12 is in a range of 40 degrees to 50 degrees, and the direction RA of the rubbing orientation of the second vertical alignment layer 14 And the direction RA of the rubbing orientation of the third vertical alignment layer 22 is in the range of 130 to 140 degrees and the direction RA of the rubbing orientation of the third vertical alignment layer 22 is in the range of 220 to 230 degrees, The direction RA may range from 310 degrees to 320 degrees. It is possible to provide a variable transmittance device capable of effectively switching between the vertical alignment state and the horizontal alignment state through the relationship of the rubbing alignment directions of the first to fourth vertical alignment layers. The direction RA of each of the rubbing orientations is an angle measured in a clockwise direction or a counterclockwise direction with respect to the horizontal axis WA as a reference. However, the direction (RA) of each of the rubbing orientations is measured by selecting only one of the clockwise and counterclockwise directions.

3, the angle between the direction RA of the rubbing orientation of the first vertical alignment layer 12 and the horizontal axis WA, the rubbing direction RA of the second vertical alignment layer 14, The angle formed by the horizontal axis WA is within the range of 40 degrees to 50 degrees when measured in the clockwise direction with respect to the horizontal axis WA and the angle RA in the direction of the rubbing alignment of the first vertical alignment layer 12, And the rubbing direction RA of the second vertical alignment layer 14 may be opposite to each other.

3, the angle formed by the direction RA of the rubbing orientation of the third vertical alignment layer 22 and the horizontal axis WA, the rubbing direction RA of the fourth vertical alignment layer 24, The angle formed by the horizontal axis WA is in the range of 130 to 140 degrees when measured in the clockwise direction with respect to the horizontal axis WA and the angle RA in the rubbing orientation of the third vertical alignment layer 22 And the rubbing direction RA of the fourth vertical alignment layer 24 may be opposite to each other.

The conditions can be controlled such that the above-mentioned pretilt angle and direction can be achieved even when the photo alignment layer is used as the first to fourth vertical alignment layers.

The exemplary transmissive variable device may further include an electrode layer disposed outside the first to fourth vertical alignment layers, and the specific kind of the electrode layer is as described in the description of the optical element.

Fig. 4 exemplarily shows a first optical element including an active GH layer, an electrode layer and a vertical alignment layer. 4, the first optical element 10 includes a first electrode layer 11, a first vertical alignment layer 12, a first active GH layer 13, a second vertical alignment layer 14, And a two-electrode layer 15 may be successively formed. The thicknesses of the first and second electrode layers and the first and second vertical alignment layers may be suitably selected in consideration of the object of the present application.

Fig. 5 exemplarily shows a second optical element including an active GH layer, an electrode layer and a vertical alignment layer. 5, the second optical element 20 includes a third electrode layer 21, a third vertical alignment layer 22, a second active GH layer 23, a fourth vertical alignment layer 24, And a four-electrode layer 25 may be successively formed. The thicknesses of the third and fourth electrode layers and the third and fourth vertical alignment layers may be appropriately selected in consideration of the object of the present application.

The transmittance variable device of the present application may further include a pressure-sensitive adhesive. The first and second optical elements may be bonded together by the adhesive. As the pressure sensitive adhesive, a pressure sensitive adhesive layer used for attaching the optical film may be appropriately selected and used. The thickness of the pressure-sensitive adhesive may be appropriately selected in consideration of the object of the present application.

The transmissive variable device of the present application may further comprise a hard coating film. The hard coating film may include a base film and a hard coating layer on the base film. The hard coating film may be appropriately selected from known hard coating films in consideration of the object of the present application. The thickness of the hard coating film may be appropriately selected in consideration of the object of the present application.

The hard coating film may be formed on the outside of the first and / or second optical elements through a pressure-sensitive adhesive. For example, the hard coating film may be attached to the outside of the substrate on which the first and / or fourth electrode layers are formed through a pressure-sensitive adhesive. As the pressure-sensitive adhesive, a pressure-sensitive adhesive to be used for adhering the optical film may be appropriately selected and used.

The present application may further include an antireflection film as the variable transmissivity device. The antireflection film may include a base film and an antireflection layer on the base film. The antireflection film may be appropriately selected from known antireflection films in view of the object of the present application. The thickness of the antireflection film can be suitably selected in consideration of the object of the present application.

The antireflection film may be formed on the outside of the first and / or second optical elements through a pressure-sensitive adhesive. For example, the antireflection film may be attached to the outside of the substrate on which the first electrode layer and / or the fourth electrode layer is present, via a pressure-sensitive adhesive. As the pressure-sensitive adhesive, a pressure-sensitive adhesive to be used for adhering the optical film may be appropriately selected and used.

As described above, the transmittance tuning device of the present application can adjust the transmittance according to whether a voltage is applied or not by controlling the orientation of the first and second active GH layers when no voltage is applied and when applying a voltage. The liquid crystal and the anisotropic dye can be aligned according to the alignment direction. Therefore, the alignment direction can be parallel to the optical axis direction of the liquid crystal and / or the absorption axis direction of the anisotropic dye.

In one example, the transmissivity tuning device can implement a transmissive state when the first and second optical elements are respectively in a vertically aligned state, and can implement a blocked state in a horizontally aligned state.

As described above, in the horizontally aligned state, the first active GH layer has an optical axis within a range of 40 to 50 degrees in a clockwise direction with respect to the abscissa of the active GH layer, and the second active GH layer has an optical axis in the active GH layer The optical axis can be in the range of 130 to 140 degrees in the clockwise direction. The difference in contrast ratio between the first active GH layer and the second active GH layer in the right and left viewing angles is reduced through the optical axis relationship, thereby providing a variable transmissivity device having excellent symmetry.

The transmittance variable device as described above can be applied to various applications. Applications for which the transmittance variable device can be applied include openings in an enclosed space including a building such as a window or a sunroof, a container or a vehicle, an eyewear, or the like. The range of the eyewear may include all the eyewear formed so that the observer can observe the outside through the lens, such as general glasses, sunglasses, sports goggles, helmets or augmented reality experience devices.

A typical application to which the transmittance variable device of the present application may be applied is eyewear. In recent years, eyewear in which a lens is mounted such that sunglasses, sports goggles, augmented reality experience devices, and the like are tilted from an observer's front line of sight are commercially available. In the case of the transmittance variable device of the present application, excellent symmetry can be ensured by reducing the difference in the contrast ratio between the right and left tilt angles when obliquely observed, as described above. Can be applied.

In the case where the transmittance variable device of the present application is applied to an eyewear, the structure of the eyewear is not particularly limited. That is, the transmittance variable device may be mounted and applied in a lens for a left eye and / or a right eye of a known eyewear structure.

For example, the eye wear includes a left eye lens and a right eye lens; And a frame for supporting the left eye lens and the right eye lens.

Fig. 6 is an exemplary schematic diagram of the eyewear, which is a schematic diagram of the eyewear including the frame 12 and the left and right eye lenses 14, and the eyewear structure to which the transmittance variable device of the present application can be applied Is not limited to Fig.

In the eyewear, the left eye lens and the right eye lens may each include the transmittance variable device. Such a lens may include only the transmittance variable device or may include other configurations.

The eyewear may have various designs. For example, the frame may have an angle of 15 to 40 degrees with respect to the observer's front sight line direction when the observer wears the eyewear and the normal line of the transmissivity variable apparatus surface. May be formed to be inclined so as to be in a range. Examples of such eyewear include sports goggles and augmented reality experience devices. When the variable transmissivity device is formed to be inclined to the eyewear, the contrast ratio at the inclination angle may be improved by adjusting the pretilt angles of the first to fourth vertical alignment layers.

In one example, the present invention provides a liquid crystal display device capable of suppressing a back flow phenomenon by a bulk liquid crystal compound even when a cell gap of a liquid crystal layer becomes thick, A device and a variable transmittance device including the device can be provided. The optical element and the transmittance variable device of the present application are applicable to various applications including a variety of architectural or automotive materials requiring adjustment of the transmittance, eyewear such as augmented reality experience goggles, sunglasses or helmets .

Figure 1 illustrates, by way of example, the transmissibility film of the present application.
Fig. 2 shows the optical axis in the horizontal alignment state of the first and second optical elements.
Fig. 3 shows pre-tilt directions of the first to fourth vertical alignment films.
Fig. 4 exemplarily shows a first optical element.
Fig. 5 exemplarily shows a second optical element.
Figure 6 illustrates an exemplary eyewear.
Figs. 7 and 8 show changes in normalized transmittance according to the voltage application time of the first and second embodiments of the present application, respectively.
FIG. 9 shows a change in the normalized transmittance according to the voltage application time in the comparative example of the present application.

Hereinafter, the optical element of the present application will be described in detail by way of examples and comparative examples, but the scope of the optical element of the present application is not limited by the following examples.

Example 1

An optical element was fabricated by forming a GH layer between two COP (cycloolefin polymer) films in which an ITO (Indium Tin Oxide) electrode layer and a vertical alignment layer were sequentially formed on the surface. The thickness of the GH layer, that is, the cell gap, was about 15 mu m. In this case, an alignment layer having a pre-tilt angle of about 88 degrees was used as the vertical alignment layer. The orientation layer was formed by coating a vertical alignment layer of polyimide type on the ITO electrode layer by bar coating, holding it at 130 DEG C for about 30 minutes, rubbing with a rubbing treatment to a thickness of about 200 nm, The COP film was laminated such that the rubbing directions were equal to each other. The GH layer is a nematic liquid crystal (MDA-06-821, Merck) having a dielectric anisotropy of about -4.9 and a refractive index anisotropy of about 0.132, a dichroic dye having a dichroic ratio of about 6.5 to 8 (X12, BASF) and a chiral dopant (S811, Merck) in a weight ratio of 98.9: 1: 0.1 (nematic liquid crystal: dichroic dye: chiral dopant). The pitch (p) of the GH layer formed as described above was about 90 μm, and the ratio (d / p) of the cell gap (d) to the pitch (p) was about 1.67. The pitch of the GH layer in the above is determined by the method of D. Podolskyy et al. Simple methods for accurate measurements of the cholesteric pitch using a stripe-wedge Grandjean-Cano cell (Liquid Crystals, Vol. 35, No. 7, July 2008, 789-791 ) Was measured by a measuring method using a wedge cell.

Example 2.

The weight ratio of nematic liquid crystal (MDA-06-821, Merck), dichroic dye (X12, BASF) and chiral dopant (S811, Merck) was controlled to 98.92: 1: 0.08 (nematic liquid crystal: dichroic dye: chiral Dopant), the optical device was manufactured in the same manner as in Example 1. [ The pitch (p) of the GH layer thus formed was about 120 μm, and the ratio (d / p) of the cell gap (d) to the pitch (p) was about 0.13.

Comparative Example 1

An optical element was prepared in the same manner as in Example 1, except that the chiral dopant was not added. Since there is no combination of chiral dopants, the pitch p is infinite, and therefore the ratio of the cell gap d to the pitch p is zero.

Test Example 1

The optical elements prepared in Examples and Comparative Examples were measured for changes in normalized transmittance by voltage application time using LCMS-200. Figs. 7 and 8 are the results for Examples 1 and 2, respectively, and Fig. 9 are the results for Comparative Example 1, respectively. In the case of Examples 1 and 2 as seen from the figure, the back flow phenomenon was hardly observed (Back Flow Tmax = about 2.9% in Example 1, Back Flow Tmax = about 4.2% in Example 2). Also, in the case of Example 1, the time taken to adjust the normalized transmittance from 90% to 10% was about 2.4 ms, and the time taken to adjust from 95% to 5% was about 19 ms. Also, in the case of Example 2, the time taken to adjust the normalized transmittance from 90% to 10% was about 43 ms, and the time taken to adjust from 95% to 5% was about 215 ms.

On the other hand, in Comparative Example 1, a back flow phenomenon was observed in which Back Flow Tmax was about 10.4%. Also, in the case of Comparative Example 1, the time taken to adjust the normalized transmittance from 90% to 10% was about 1.8 s, and the time taken to adjust from 95% to 5% was more than about 2 s.

Claims (11)

A liquid crystal display device comprising an active liquid crystal layer including a liquid crystal compound,
The optical axis of the active liquid crystal layer switches between a vertically aligned state and a horizontally aligned state,
(D / p) of the thickness (d) of the active liquid crystal layer and the pitch (p) of the liquid crystal compound in the vertically aligned state is in the range of 0.1 to 0.2. The optical element according to claim 1, wherein the liquid crystal compound is a nematic liquid crystal. The optical element of claim 1, wherein the active liquid crystal layer further comprises a dichroic dye guest. The dyed dye according to claim 3, wherein the dichroic dye is selected from the group consisting of azo dyes, anthraquinone dyes, methine dyes, azomethine dyes, merocyanine dyes, naphthoquinone dyes, tetrazine dyes, phenylene dyes, An optical element which is a dyestuff dye, a diketopyrrolopyrrole dye, a squalene dye or a pyromethene dye. The optical element according to claim 1, wherein the liquid crystal layer further comprises a chiral dopant. The optical element according to claim 1, wherein the pretilt angle of the liquid crystal compound in the vertically aligned state is in the range of 70 degrees or more but less than 90 degrees. The optical element according to claim 1, wherein the thickness (d) of the liquid crystal layer is 4 占 퐉 or more. An optical element according to claim 1; And a second active liquid crystal layer or a passive polarization layer superimposed on the active liquid crystal layer included in the optical element. 9. The variable transmittance device according to claim 8, wherein the optical axis of the second active liquid crystal layer switches between a horizontally aligned state and a vertically aligned state. A left eye lens and a right eye lens; And a frame for supporting the left eye lens and the right eye lens,
Wherein the left eye lens and the right eye lens each include the optical element according to claim 1. 11. The device according to claim 10, wherein the eyewear is an augmented reality experience device.

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