KR20110068336A - LCD Light Attenuation Device and Vehicle Smart Mirror Using the Same - Google Patents

Abstract

The present invention relates to an LCD light attenuator applied to a room mirror or a side mirror of a vehicle to protect the eyesight of a vehicle driver and prevent glare from the strong light from the rear when driving at night, and a smart mirror for a vehicle using the same.

An LCD optical attenuation device according to the present invention includes an LCD panel including at least one liquid crystal cell, and a power supply device for supplying an electric field to the LCD panel. The liquid crystal cell includes a liquid crystal layer and two substrate layers facing the liquid crystal layer. The liquid crystal layer is a nematic liquid crystal having a negative dielectric anisotropy, a chiral material such that the nematic liquid crystal is a cholesteric phase having a pitch of 1 to 4 times the cell gap of the liquid crystal layer, and whether or not the electric field is supplied. It is rearranged with nematic liquid crystals and filled with a mixture of dichroic dyes that transmit or absorb light. The substrate layer includes a vertical alignment layer for arranging the nematic liquid crystal and the dichroic dye in a first array perpendicular to the substrate layer plane, and an electric field passing through the liquid crystal layer to generate the nematic liquid crystal and the dichroic dye. And an electrode that allows the dye to be rearranged in a second arrangement different from the first arrangement.

Description

LCD Light Attenuating Device and Vehicle Smart Mirror

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an LCD light attenuator for a smart mirror for a vehicle. More specifically, the present invention relates to a room mirror or side mirror of a vehicle in order to protect a driver's eyesight and prevent glare from strong light from behind during night driving. The present invention relates to an LCD light attenuation device and a smart mirror for a vehicle using the same.

In general, the light attenuator is widely applied to ski goggles, sunglasses, vehicle smart mirrors to prevent the glare of the vehicle driver, and light transmittance control windows. Sunglasses and ski goggles mainly use a photo-chromic material to implement a light attenuation device. This photochromic material has the advantage of being easy to apply, but it is difficult to apply to a smart mirror for a vehicle due to the slow reaction speed. Do. On the other hand, the light attenuation device of the smart mirror for the vehicle is mainly implemented by ECM (Electro chronic mirror) technology, but this ECM technology is also relatively inadequate to be applied to the automotive exterior smart mirror, because the response speed is relatively slow from several seconds to several tens of seconds. Do.

In order to improve the reaction speed, an optical attenuator implemented by LCD (LCD) has been proposed, and as a representative patent, US Patent US4,272,162, US4,278,328, US4,357,374, US4,676,601, US4,696,548, US4729638, US Pat. No. 4,848,878, US5,015,086, US6,239,778, US6,759,945, and KR10-0646444 have been disclosed.

In US Pat. No. 5,015,086 and KR10-0646444, an optical attenuator is implemented using an LCD including a polarizer. However, when the polarizing plate is included, the light transmittance has a different value according to the polarization direction of the incident light, and the light transmittance or the light reflectance is lowered. The maximum transmittance of the technique proposed in US Pat. No. 5,015,086 is 35%, KR10 The maximum transmission of the technique proposed in -0646444 is 44%.

US Pat. No. 4,272,162 and US Pat. No. 4,278,328 disclose techniques for controlling light transmittance by adding a dichroic dye to a nematic liquid crystal (NLC) with a positive dielectric anisotropic. . Since the light attenuation apparatus to which this technique is applied has a lower light transmittance in a state where no electric field is applied, the light transmittance is lowered and maintains a dark state when no electric field is applied. Therefore, when applied to the smart mirror of the vehicle, the smart mirror in the emergency that the electricity supply is cut off, which hinders the driver's safe driving, which in turn violates the international safety regulations of the automotive mirror.

In US Pat. No. 6,239,778, a guest-host LCD is formed by mixing a negative dielectric liquidity and a small amount of dichroic dye between two substrates coated with a vertical alignment layer to form a liquid crystal layer. To implement the transmissive light attenuation device. This means that the dichroic dye molecules are anisotropically arranged on the substrate plane with the pitch of the cholesteric phase being more than four times the thickness of the liquid crystal cell in a state where voltage is applied. Will be. If the pitch of the cholesteric phase is more than four times the thickness of the liquid crystal cell, the liquid crystal molecules have a twisted structure of up to 90 degrees on the substrate's flat surface, and the dichroic dye molecules that absorb light also line up with the liquid crystal molecules. Therefore, it has a structure that is twisted 90 degrees on the “plane” of the substrate. That is, since almost all dichroic dye molecules are arranged only in the azimuth direction of 180 degrees, light having a polarization direction parallel to liquid crystal molecules is absorbed well, but light having a polarization direction perpendicular to the liquid crystal molecules is difficult to absorb light. . That is, the anisotropic arrangement of dye molecules cannot maximize absorption of incident light polarized isotropically with the same dye molecular weight.

US 6,621, 550 discloses a technique for incorporating a dichroic dye into a nematic liquid crystal having a negative dielectric anisotropy in the structure of a reflective LCD and injecting it into a vertically oriented cell. In order to improve the light absorption of the dichroic dye, a 1/4 wavelength film is formed between the liquid crystal layer and the reflecting plate in the liquid crystal cell to rotate the polarization direction of the light by 90 degrees when the light is incident and reflected, thereby absorbing the incident light. Improve. However, in order to form the 1/4 wavelength polymer liquid crystal film in the cell, a more complicated process is required, and there is a disadvantage in that light absorption is not constant according to the polarization direction of incident light.

The present invention has been made to solve the above-mentioned problems of the prior art, and the object of the present invention is to provide an LCD optical attenuator that has a fast response rate of transmittance or reflectance change and low power consumption without depending on the polarization direction of incident light. There is this.

Another object of the present invention is to provide a smart mirror for a vehicle using the above-described LCD light attenuating device.

LCD light attenuation apparatus according to the present invention for achieving the above object,

An LCD panel including at least one liquid crystal cell, and a power supply device for supplying an electric field to the LCD panel, wherein the liquid crystal cell includes a liquid crystal layer and two substrate layers facing the liquid crystal layer. In the device,

The liquid crystal layer is a nematic liquid crystal having a negative dielectric anisotropy, a chiral material such that the nematic liquid crystal is a cholesteric phase having a pitch of 1 to 4 times the cell gap of the liquid crystal layer, and whether or not the electric field is supplied. Filled with a mixture of dichroic dyes that are rearranged with nematic liquid crystals to transmit or absorb light,

The substrate layer includes a vertical alignment layer for arranging the nematic liquid crystal and the dichroic dye in a first array perpendicular to the substrate layer plane, and an electric field passing through the liquid crystal layer to generate the nematic liquid crystal and the dichroic dye. And an electrode to allow the dye to be rearranged in a second array different from the first array.

In addition, a smart mirror for a vehicle according to the present invention for achieving the above object,

An LCD panel including at least one liquid crystal cell, a power supply for supplying an electric field to the LCD panel, an incident light sensing unit for sensing the brightness of the surroundings, and the power supply apparatus according to the ambient brightness detected by the incident light sensing unit. In the smart mirror for a vehicle including an operation status analysis unit for operating the LCD panel by controlling the liquid crystal cell and a liquid crystal layer and two substrate layers facing the liquid crystal layer,

The liquid crystal layer is a nematic liquid crystal having a negative dielectric anisotropy, a chiral material such that the nematic liquid crystal is a cholesteric phase having a pitch of 1 to 4 times the cell gap of the liquid crystal layer, and whether or not the electric field is supplied. Filled with a mixture of dichroic dyes that are rearranged with nematic liquid crystals to transmit or absorb light,

The substrate layer includes a vertical alignment layer for arranging the nematic liquid crystal and the dichroic dye in a first array perpendicular to the substrate layer plane, and an electric field passing through the liquid crystal layer to generate the nematic liquid crystal and the dichroic dye. And an electrode to allow the dye to be rearranged in a second array different from the first array.

As described above, the present invention has the following effects.

First, an optical attenuator capable of controlling light transmittance or light reflectance may be configured as an LCD panel that does not use a polarizing plate.

Second, an optical attenuator capable of uniformly controlling both polarized light and unpolarized light can be configured.

Third, since the power consumption of the LCD panel is low, an energy-saving optical attenuation device can be configured.

Fourth, the light transmittance or the light reflectance and the reaction rate can be arbitrarily adjusted according to the change in the brightness of the surroundings by using the fast response speed and halftone of the LCD.

Fifth, even when the power supply is cut off, the light transmittance and the light reflectance of the optical attenuator can be maintained in a high state.

Sixth, according to the characteristics of the dichroic dye to be used, it is possible to arbitrarily select a region in which the light transmittance or the light reflectance can be adjusted in the wavelength range of the visible ray band.

Seventh, flat or curved glass or plastic may be used as the LCD substrate.

Hereinafter, an LCD light attenuation device and a vehicle smart mirror using the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

The present invention implements a transmissive and reflective optical attenuator using an LCD comprising a dichroic dye and a chiral material in a nematic liquid crystal having a negative dielectric anisotropy.

In more detail, the LCD light attenuation apparatus according to the present invention comprises at least one liquid crystal cell and a power supply unit for supplying an electric field to the liquid crystal cell. Each liquid crystal cell includes a liquid crystal layer formed between two substrate layers. Each liquid crystal layer can be rearranged according to the intensity of the electric field, and a nematic liquid crystal in which the dielectric anisotropy is negative and the nematic liquid crystal are mixed with each other to produce light of a constant wavelength range. It comprises an absorbing amount of dichroic dye and a chiral material that allows the nematic liquid crystal to have a twisted structure.

By the voltage applied from the voltage supply part, the transparent nematic liquid crystal material of the liquid crystal layer is rearranged on a plane parallel to the substrate, and the dichroic dye molecules are also isotropically rearranged together with the liquid crystal molecules. The dichroic dye molecules have different wavelengths of light to be absorbed depending on the arrangement state, and the dichroic dye molecules can realize a light attenuation function without a polarizing plate.

1 and 2 are structural diagrams showing a transmissive LCD optical attenuator according to a first embodiment of the present invention, in which FIG. 1 shows a state where no power is supplied, and FIG. 2 shows a state where power is supplied. .

The LCD light attenuation apparatus according to the present invention includes a guest-host LCD panel including at least one liquid crystal cell 100, and a power supply unit 200 for supplying an electric field to each liquid crystal cell 100 of the LCD panel. The liquid crystal cell 100 includes a liquid crystal layer 110 and two substrate layers 120 and 130 stacked opposite to both sides of the liquid crystal layer 110.

The liquid crystal layer 110 includes a spacer 111 for maintaining a gap between the two substrate layers 120 and 130, and can be rearranged according to the electric field strength, transparent, and have a dielectric anisotropy. (negative) nematic liquid crystal (112), positive dichroic dye (113) mixed with the nematic liquid crystal 112 to absorb light of a predetermined wavelength band (113), and The nematic liquid crystal 112 is filled with a mixture of chiral material 114 such that it has a twisted structure. In addition, the liquid crystal layer 110 is sealed by the sealant 115. Here, positive dichroism refers to a characteristic of absorbing light waved in the long axis direction of a dye molecule.

Each of the substrate layers 120 and 130 has antireflection layers 121 and 131, transparent substrates 122 and 132, transparent electrode layers 123 and 133, transparent protective layers 124 and 134, and liquid crystals from the outside. The alignment layers 125 and 135 are stacked, and the liquid crystal layer 110 is formed between the two liquid crystal alignment layers 125 and 135.

The anti-reflective layers 121 and 131 are located at the outermost surface of the LCD panel to minimize the reflectance of light entering or passing through the transparent substrates 122 and 132 and the air interface. It is designed to have a reflectance of less than 1% at the fleet.

The transparent substrates 122 and 132 are made of glass or plastic material, and have a flat or curved surface shape. In the case of a flexible plastic substrate, it may be attached to flat and transparent glass to maintain a flatness or curvature.

The transparent electrode layers 123 and 133 are generally formed of an indium tin oxide (ITO) thin film having a thickness of about 300 nm or less, and may be manufactured by coating a thickness of about 1500 mm on the transparent substrates 122 and 132, or using a metal of about 100 nm or less. It can also be used with very thin coatings. However, there is a problem that the light transmittance loss is increased when the metal is coated.

The transparent protective layers 124 and 134 are thin silicon nitride films or silicon oxide thin films, and block various impurities introduced into the liquid crystal layer 110 from the transparent substrates 122 and 132 or the transparent electrode layers 123 and 133.

The liquid crystal alignment layers 125 and 135 allow the nematic liquid crystal molecules 112 of the liquid crystal layer 110 to be arranged in a direction perpendicular to the plane of the substrate layer. Generally, liquid crystal molecules are arranged at an angle of 80 degrees to 90 degrees with respect to the substrate. The functional vertical alignment agent mainly uses a silane surfactant or polyimide (PI), and rubbing with a soft cloth to obtain a slightly tilted homeotropic alignment. )do.

The spacer 111 maintains a constant gap between the two substrate layers 120 and 130, so that even if the two substrate layers 120 and 130 are bent in a curved surface shape, the thickness of the liquid crystal layer 110 is a cell gap. keep (d) constant. The spacer 111 is generally formed by dispersing a spherical cinnabar or round rod-shaped micro pearl, and forming a partition or column using polyimide (PI) on the substrate layers 120 and 130. It can be formed by the method.

The liquid crystal layer 110 is filled with a mixture of the nematic liquid crystal 112, the dichroic dye 113, and the chiral material 114 while maintaining the cell gap d by the spacer 111.

The cell gap d of the liquid crystal layer 110 is several micrometers to several tens of micrometers, and is formed in VA (Vertically Aligned) mode. By the liquid crystal alignment layers 125 and 135, the liquid crystal molecules 112 are vertically arranged in a direction of 80 degrees to 90 degrees with respect to the substrate plane. This vertical alignment state is extended to the inside of the cell by the interaction between the liquid crystal molecules, and has an induced nematic phase over the entire liquid crystal layer 110.

Papers G. W. Gray and D. G. McDonnell, Mol. Cryst. Liq. As disclosed in Cryst., 37, 189, 1976 and the like, when a small amount of chiral material 114 is added to the nematic liquid crystal as in the present invention, the liquid crystal molecules are in a twisted arrangement and thus a cholesteric phase. phase). In this invention, a chiral substance is added to a nematic liquid crystal so that a chiral substance acts on a nematic liquid crystal and the pitch becomes a cholesteric phase whose pitch is 1 to 4 times the cell gap of a liquid crystal layer.

The cholesteric phase is a helical structure, the pitch P _{0 of which} is proportional to the inverse of the content of the chiral material, so that it can be controlled relatively accurately. This pitch P ₀ is the pitch of the cholesteric phase when the liquid crystal is not affected from the outside in the bulk state, and is strongly influenced by the liquid crystal alignment layer in the liquid crystal cell of the thin film state as in the present invention. That is, in the vertically aligned thin cell as in the present invention, the vertical alignment force of the liquid crystal alignment layer deforms the helical structure of the cholesteric phase into the induced nematic phase. The smaller the cell gap d and the larger the pitch P ₀ of the cholesteric phase, the better the induced nematic phase is formed.

The limitation that the cholesteric phase has a nematic phase simply by the vertical alignment force of the thin film state greatly depends on the physical properties of the liquid crystal itself. PR Gerber (Z. Naturforsch., 36A, 718, 1981) reported (P ₀ / d) = 0.98, and the inventor of this invention, Jong-cheon Lee (Ph.D thesis, Kent State University, 1990) Reported (d / P ₀ ) = 0.74. Common to the cell gap (d) is P is larger than _0/2, which in other words 180 twisted cholesteric liquid crystal phase, or P _0/2 cholesteric liquid when the liquid crystal phase is located between a vertically oriented substrate-induced nematic liquid crystal having a thickness of It means that the phase exists stably. In this invention, the chiral material 114 is mixed such that the pitch Po on the cholesteric of the nematic liquid crystal is 2d so that the nematic liquid crystal molecules have a spiral structure twisted about 180 degrees between both substrates.

Since the dichroic dye 113 has a rectangular shape similar to that of the nematic liquid crystal molecules, the nematic liquid crystal molecules and the dichroic dye molecules are well mixed with each other. Representative dichroic dyes include azo base dyes G165, G205, G232, G239 and anthraquinone dyes commercialized by Mitsui. Dichroic dye molecules strongly absorb light in a particular wavelength range in the visible range and display a particular color. Thus, mixing dichroic dyes that display multiple colors can produce a black dye mixture that absorbs light evenly in the visible range.

The liquid crystal layer of the present invention is composed by mixing 90% to 98% of the negative dielectric anisotropy, 1% to 5% of the dichroic dye, and 0.1% to 5% of the chiral material. The mixture of the nematic liquid crystal and the dichroic dye constituting the liquid crystal layer has a nematic liquid crystal phase by the liquid crystal alignment layer in a state where no electric field is applied from the outside, and a cholesteric liquid crystal phase in a state where the electric field is applied from the outside. Has

The sealant 115 protects the liquid crystal mixture filled in the liquid crystal layer 110 from external air or impurities and limits the region of the liquid crystal layer 110.

The power supply unit 200 includes a power source 210 connected between the transparent electrode layers 123 and 133 of the two substrate layers 120 and 130, and a switch 220 that switches between the power source 210 and the transparent electrode layers 123 and 133. ).

Referring to Figure 1, the operation of the LCD optical attenuator according to the present invention in a state in which power is not applied to the LCD panel by opening the switch of the voltage supply.

When no power is supplied from the power supply unit 200 to the LCD panel, the nematic liquid crystal molecules are vertically aligned by the liquid crystal alignment layers 125 and 135, and the dichroic dye molecules are also arranged in a direction perpendicular to the substrate plane. It is arranged in a direction perpendicular to the plane.

In this state, since the incident light Oin proceeds in parallel with the long axis of the dichroic dye molecule of the liquid crystal layer, since the vibration direction of the light is orthogonal to the long axis of the dye molecule, light absorption is minimized and the light emitted through the liquid crystal layer ( Oout) is the maximum value, so it becomes bright. Experiments show that the light transmittance of the LCD light attenuator according to the present invention is 60 to 70%.

Referring to Figure 2, the operation of the LCD optical attenuator according to the present invention in a state in which power is supplied to the LCD panel by switching on the voltage supply.

When a sufficient potential difference of more than a threshold voltage is applied between the transparent electrode layers 123 and 133 of the two substrate layers 120 and 130, an electric field is formed in the liquid crystal layer 110. Then, the nematic liquid crystal molecules having negative dielectric anisotropy are rearranged in a direction parallel to the substrate plane.

The nematic liquid crystal molecules mixed with the chiral material 114 have a pitch P ₀ on the cholesteric phase. 2d, the nematic liquid crystal molecules have a helical arrangement twisted about 180 degrees between both substrate layers. That is, the liquid crystal molecules close to the substrate layer are arranged parallel to the substrate plane while being parallel to the substrate plane, and the liquid crystal molecules twisted spirally and positioned at the center of the liquid crystal layer are rotated 90 degrees while being parallel to the substrate plane to rotate the substrate up and down. The liquid crystal molecules close to the direction and adjacent to the opposite substrate layer are rotated by 180 degrees and are arranged in parallel with the vertical direction of the substrate.

That is, the nematic liquid crystal molecules 112 are arranged in a helical structure rotated 180 degrees corresponding to 1/2 pitch of the cholesteric phase over the entire liquid crystal layer 110, and the positive dichroic dye molecules 113 Since they are arranged side by side with the nematic liquid crystal molecules 112, the rectangular nematic liquid crystal molecules and the dichroic dye molecules are uniformly arranged at 360 degree azimuth angle on the plane parallel to the substrate by the symmetry of the head and tail portions. Therefore, it is transmitted with uniform intensity regardless of the polarization direction of incident light Oin. In addition, since the incident light Oin proceeds in a direction orthogonal to the dichroic dye molecules, the light absorption rate becomes a maximum value and the transmitted light Oout has a minimum value.

In this case, when an electric field is applied to the liquid crystal layer and the nematic liquid crystal and the dichroic dye have a cholesteric phase, light having a full azimuth angle is uniformly absorbed regardless of whether the light is polarized, thereby having a uniform reflectance.

3 is a structural diagram illustrating an LCD panel of an LCD light attenuating device according to another embodiment of the present invention. The LCD light attenuator shown in FIG. 3 has a reflective structure. In the LCD light attenuators shown in FIGS. 1 and 2, the opaque metal film 31 is applied to the substrate 132 instead of the transparent electrode layer 133 of one substrate layer. By coating, the function as an electrode and the light reflection plate which are necessary for an LCD drive are simultaneously implemented. In this case, the antireflective layer of the one substrate layer is omitted.

As the material of the opaque metal film 31, any one of aluminum, chromium and silver is suitable, and the light reflectance of the opaque metal film 31 is 50% to 99%. The opaque metal film 31 is protected by the protective layer 134 in the liquid crystal process and impurities which can be supplied to the liquid crystal layer 110 are blocked. The substrate 132 may be made of glass or plastic, and may be easily applied to a flat surface or a curved surface.

The incident light Oin passes through the liquid crystal layer 110 of the LCD panel and is reflected by the metal film 31, and then passes through the liquid crystal layer 110 of the LCD panel and is emitted to the outside. Accordingly, since the reflective optical attenuator has a two-fold increase in optical path compared with the transmission type optical attenuator as shown in Figs. 1 and 2, the intensity of light emitted from the reflective optical attenuator is minimized. The light attenuation device can be applied to an anti-glare mirror for automobiles.

The operation of the liquid crystal layer in the state in which no power is applied to the LCD panel and in the state in which the power is applied is the same as the LCD panel of the transmissive optical attenuator shown in FIGS. 1 and 2.

4 is a structural diagram illustrating an LCD panel of an LCD light attenuating device according to another embodiment of the present invention.

The metal reflective layer 41 and the metal protective layer 42 are further deposited on the outer surface of the transparent substrate 132 of one substrate layer of the transmissive LCD optical attenuator shown in FIGS. 1 and 2, and the antireflective layer is omitted. The metal reflection layer 41 serves to reflect incident light, and the metal protective layer 42 serves to prevent damage of the metal reflection layer 41. The substrate 132 may be made of glass or plastic, and may be easily applied to a flat surface or a curved surface. The metal reflection layer is made of any one of aluminum, chromium and silver.

The operation of the liquid crystal layer in the state in which no power is applied to the LCD panel and in the state in which the power is applied is the same as the LCD panel of the transmissive optical attenuator shown in FIGS. 1 and 2.

5 is a structural diagram illustrating an LCD panel of an LCD light attenuating device according to another embodiment of the present invention.

A substrate 52 (ie, a substrate having a mirror function) in which a reflective layer 51 is coated on an outer surface of the transparent substrate 132 without omitting an antireflection layer of one substrate layer of the transmissive LCD light attenuator shown in FIGS. 1 and 2. ) Is bonded with a transparent curing agent. This transparent curing agent is a transparent thermosetting resin or UV curing resin, and forms a hardening layer 53 between the transparent substrate 132 and the reflective layer 51. The cured layer 53 has a refractive index of 1.4 to 1.55 in the visible light band, which is similar to that of the transparent glass substrate and the plastic substrate, thereby minimizing internal reflection at the interface between other materials.

The operation of the liquid crystal layer in the state in which no power is applied to the LCD panel and in the state in which the power is applied is the same as the LCD panel of the transmissive optical attenuator shown in FIGS. 1 and 2.

The light attenuation apparatus according to the present invention described above can be applied to a transmittance variable ski goggles, a helmet window or a smart window, or can be applied to a reflectance variable automobile smart mirror. Such a variable optical attenuator can adjust transmittance or reflectance at a fast response rate of several tens of msec. In addition, since the power consumption of LCD is several tens of mA or less and the driving voltage required by this invention is less than 10V, portable batteries can be used as a power source. good. In addition, an optical attenuation apparatus independent of the polarization direction of incident light is possible. When using a portable battery, only a primary battery such as an alkaline battery may be used, or a solar cell and a rechargeable secondary battery may be used in parallel.

The smart mirror of the vehicle to which the LCD light attenuating device according to the present invention is applied comprises an incident light detecting unit, an operation status analyzing unit, a power supply and a driving unit, and an LCD light attenuating device. The incident light detecting unit recognizes the brightness of the front and rear of the vehicle with an optical sensor, and the operation analysis unit operates the power and the driving unit to operate the LCD light attenuating device when the brightness of the incident light corresponds to the glare condition of the driver. The reflectance reflected from the lower the.

On the other hand, if the brightness of the incident light from the operation analysis unit does not correspond to the glare condition of the driver, the power is not applied to the LCD light attenuator, and as shown in FIG. Since it is arranged perpendicular to the plane to maintain a high light transmittance and a high reflectance, it satisfies the safety condition criteria of the automotive mirror that must maintain a bright condition in the absence of voltage.

Although the technical spirit of the present invention has been described above with reference to the accompanying drawings, this is intended to describe exemplary embodiments of the present invention by way of example and not to limit the present invention. In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

1 and 2 are structural diagrams showing a transmissive LCD optical attenuator according to a first embodiment of the present invention, in which FIG. 1 shows a state where no power is supplied, and FIG. 2 shows a state where power is supplied. .

3 is a structural diagram illustrating an LCD panel of an LCD light attenuating device according to another embodiment of the present invention.

Figure 4 is a structural diagram showing the LCD panel of the LCD light attenuating device according to another embodiment of the present invention.

5 is a structural diagram illustrating an LCD panel of an LCD light attenuating device according to another embodiment of the present invention.

Claims (30)

An LCD panel including at least one liquid crystal cell, and a power supply device for supplying an electric field to the LCD panel, wherein the liquid crystal cell includes a liquid crystal layer and two substrate layers facing the liquid crystal layer. In the device, The liquid crystal layer is a nematic liquid crystal having a negative dielectric anisotropy, a chiral material such that the nematic liquid crystal is a cholesteric phase having a pitch of 1 to 4 times the cell gap of the liquid crystal layer, and whether or not the electric field is supplied. Filled with a mixture of dichroic dyes that are rearranged with nematic liquid crystals to transmit or absorb light, The substrate layer includes a vertical alignment layer for arranging the nematic liquid crystal and the dichroic dye in a first array perpendicular to the substrate layer plane, and an electric field passing through the liquid crystal layer to generate the nematic liquid crystal and the dichroic dye. And an electrode which allows the dye to be rearranged in a second array different from the first array. The LCD of claim 1, wherein the liquid crystal layer further comprises a spacer for maintaining a constant cell gap of the liquid crystal layer. The device of claim 1, wherein the dichroic dye has a positive dichroism with respect to visible light. 2. The LCD of claim 1, wherein the substrate layer further comprises a protective layer that blocks impurities introduced into the liquid crystal layer. 2. The LCD of claim 1, wherein the chiral material has any one of a cholesteric phase and a nematic phase. The device of claim 1, wherein the mixture forms a vertically oriented nematic phase when the electric field is not applied, and a cholesteric phase when the electric field is applied. 7. The LCD of claim 6, wherein the light transmittance of the liquid crystal layer to which the electric field is not applied is higher than the light transmittance of the liquid crystal layer to which the electric field is applied. The method according to claim 1, wherein the mixture is mixed with 90% to 98% of the nematic liquid crystal, 1% to 5% of the dichroic dye, and 0.1% to 5% of the chiral material. LCD light attenuator. 9. The LCD light attenuating device according to any one of claims 1 to 8, wherein the electrode is a transparent electrode. 11. The LCD of claim 10, wherein each of the substrate layers has an outermost surface coated with an anti-reflective layer. 9. The LED of any one of claims 1 to 8, wherein an electrode of the substrate layer into which light is incident among the two substrate layers is a transparent electrode, and an electrode of the remaining substrate layers is an opaque metal film electrode. Damping device. 12. The LCD of claim 11, wherein the opaque metal film electrode is formed by coating any one of aluminum, chromium, and silver on a substrate surface. 12. The LCD of claim 11, wherein the outermost surface of the substrate layer to which light is incident is coated with an antireflective layer. 12. The LCD of claim 11, wherein the light reflectance of the opaque metal film electrode is 50% to 99%. The electrode according to any one of claims 1 to 8, wherein the electrode is a transparent electrode, And the substrates of the two substrate layers are transparent substrates, and a reflective layer is formed outside the substrate of one of the two substrate layers. 16. The LCD of claim 15, wherein the reflective layer comprises a metal film and a protective film. 16. The LCD of claim 15, wherein the outermost surface of the remaining substrate layers of the two substrate layers is coated with an anti-reflective layer. 12. The LCD of claim 11, wherein the light reflectance of the reflective layer is 50% to 99%. The method of claim 1, wherein the electrode is a transparent electrode, the substrate of the two substrate layers is a transparent substrate, and a reflective film is coated on an outer surface of one of the two substrate layers. LCD light attenuator, characterized in that formed by adhering the substrate to the adhesive. 20. The LCD of claim 19, wherein the outermost surface of the remaining substrate layers of the two substrate layers is coated with an anti-reflective layer. 20. The LCD of claim 19, wherein the adhesive is transparent and the visible light band refractive index of the adhesive layer is 1.4 to 1.55. An LCD panel including at least one liquid crystal cell, a power supply for supplying an electric field to the LCD panel, an incident light sensing unit for sensing the brightness of the surroundings, and the power supply apparatus according to the ambient brightness detected by the incident light sensing unit. In the smart mirror for a vehicle including an operation status analysis unit for operating the LCD panel by controlling the liquid crystal cell and a liquid crystal layer and two substrate layers facing the liquid crystal layer, The liquid crystal layer is a nematic liquid crystal having a negative dielectric anisotropy, a chiral material such that the nematic liquid crystal is a cholesteric phase having a pitch of 1 to 4 times the cell gap of the liquid crystal layer, and whether or not the electric field is supplied. Filled with a mixture of dichroic dyes that are rearranged with nematic liquid crystals to transmit or absorb light, The substrate layer includes a vertical alignment layer for arranging the nematic liquid crystal and the dichroic dye in a first array perpendicular to the substrate layer plane, and an electric field passing through the liquid crystal layer to generate the nematic liquid crystal and the dichroic dye. Smart mirror for a vehicle comprising an electrode to allow the dye to be rearranged in a second array different from the first array. The smart mirror of claim 22, wherein the power supply unit is one of a power source, a primary battery, a secondary battery, and a solar cell of the vehicle. 23. The vehicle smart mirror of claim 22, wherein the liquid crystal layer further comprises a spacer for maintaining a constant cell gap of the liquid crystal layer. 23. The smart mirror for a vehicle according to claim 22, wherein the dichroic dye has a positive dichroism with respect to visible light. The vehicle smart mirror of claim 22, wherein the substrate layer further comprises a protective layer that blocks impurities introduced into the liquid crystal layer. 23. The smart mirror of claim 22, wherein the chiral material has any one of a cholesteric phase and a nematic phase. The smart mirror of claim 22, wherein the mixture forms a vertically oriented nematic phase when the electric field is not applied, and a cholesteric phase when the electric field is applied. 29. The vehicle smart mirror of claim 28, wherein the light transmittance of the liquid crystal layer to which the electric field is not applied is higher than the light transmittance of the liquid crystal layer to which the electric field is applied. 23. The method of claim 22, wherein the mixture is mixed with 90% to 98% of the nematic liquid crystal, 1% to 5% of the dichroic dye, and 0.1% to 5% of the chiral material. Car smart mirror.

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