JP5797323B2 - Double-cell liquid crystal device with rapid switching - Google Patents

Description

  The present invention relates to a liquid crystal device for modulating light passing therethrough. The invention further relates to a method for controlling such a liquid crystal device.

In many applications, rapid switching between a transparent (“light”) state and an opaque (“dark”) state is desirable.
The liquid crystal device is used as an optical shutter that realizes switching between a bright state and a dark state, for example. In particular, a conventional nematic liquid crystal material that is currently widely used in various liquid crystal displays and available electronic driving technologies. It has been found difficult to achieve sufficiently rapid switching speeds using. In particular, the relaxation of nematic liquid crystal materials is a slow process.
Many solutions have been proposed and tried to increase the switching speed of liquid crystal devices, but it turns out that it is difficult to achieve switching in a short time from dark to light and from light to dark simultaneously. doing.

  It is an object of the present invention to address the above-described problems of the prior art, and the present invention is an improvement that is configured to allow faster switching speeds between bright and dark states. Provided liquid crystal device.

  According to the first embodiment of the present invention, therefore, a liquid crystal device for modulating light passing therethrough, the liquid crystal device comprising a plurality of liquid crystal molecules sandwiched between a pair of first substrates. A first liquid crystal cell having a liquid crystal material, and a second liquid crystal cell having a liquid crystal material including a plurality of liquid crystal molecules sandwiched between a pair of second substrates, the first liquid crystal cell and the second liquid crystal cell The liquid crystal cell is arranged in a layered structure so that light passing through the first liquid crystal cell reaches the second liquid crystal cell, and each of the first liquid crystal cell and the second liquid crystal cell is a liquid crystal cell Is individually controllable between a relaxed state in which the first birefringence index is displayed and a switching state in which the liquid crystal cell exhibits the second birefringence index, and the liquid crystal cell is in the relaxed state with the second liquid crystal cell remaining in the relaxed state. When the first liquid crystal cell transitions from the relaxed state to the switched state The total birefringence of the liquid crystal device changes from the first total birefringence to the second total birefringence, the liquid crystal device transitions from the first light modulation state to the second light modulation state, and then When the first liquid crystal cell remains in the switched state and the second liquid crystal cell transitions from the relaxed state to the switched state, the total birefringence of the liquid crystal device is changed from the second total birefringence to the first total birefringence. A liquid crystal device is provided, wherein the liquid crystal device is arranged and configured to change so that the liquid crystal device changes from the second light modulation state to the first light modulation state. .

A nematic liquid crystal cell with uniform orientation functions optically as a uniaxial (birefringent) optical plate with an optical axis that matches the preferred orientation direction of the liquid crystal molecules in the cell. When such a liquid crystal cell is inserted between two intersecting polarizing plates, the luminous intensity l transmitted through the cell and the polarizing plate is aligned at an optical axis of 45 ° with respect to the transmission direction of the polarizing plate. Is simply given by the following equation:

l = l ₀ sin ² δ / 2

Here, δ = 2πdΔn / λ, the birefringence index _{Δn = n e -n 0 (n} e and _{n 0} are其s is the refractive index of the extraordinary ray and ordinary ray of the liquid crystal material) cell phase delay by Where λ is the wavelength of the light source.

Two liquid crystal cells each having a birefringence index Δn ₁ = n _e1 −n ₀₁ and Δn ₂ = n _e2 −n ₀₂ and thicknesses d ₁ and d ₂ are aligned parallel to each other, and each optical axis Is superimposed as a layered structure, the total phase delay of the two cells is given by:

δ _total = δ ₁ + δ ₂ = 2π (d ₁ Δn ₁ + d ₂ Δn ₂ ) / λ

However, if the optical axis of the cell is 90 °, the total phase delay of the two liquid crystal cells is

δ _total = δ ₁ −δ ₂ = 2π (d ₁ Δn ₁ −d ₂ Δn ₂ ) / λ,

Or may be expressed as a sum as follows:

δ _total = δ ₁ + (− δ ₂ ) = 2π [d ₁ Δn ₁ + d ₂ (−Δn ₂ )] / λ,

Here, Δn ₂ has a negative sign. This is a notation used as a background to the application of the present invention.

  The cell gap thickness in this dual cell device is a constant parameter of the cell, i.e. independent of the applied electric field. On the other hand, the birefringence of the cell can be controlled by applying an electric field. Thus, it is contemplated that “birefringence” and “phase retardation” are synonymous with liquid crystal devices in accordance with various aspects of the present invention.

  Further, the “relaxed” state has a meaning as an “electric field off” state in which the electric field applied by switching does not exist in the liquid crystal device, and the “switched” state indicates that the electric field applied by switching is in the liquid crystal device. Has the meaning of the “electric field on” state.

  In the present invention, the relaxation of the liquid crystal material in the liquid crystal cell (the duration of this relaxation is determined by the thickness of the cell gap and the anchoring strength, and the viscosity and elastic constant of the liquid crystal material) Recognize that this is a factor that limits the switching speed between dark states and that this relaxation process is optically "cancelled" by properly arranging two appropriate liquid crystal cells in succession. Based on what you are doing. The inventor of the present invention further enables the total birefringence of two liquid crystal cells arranged in succession to change the liquid crystal device (such as dark and bright) 2 by actively switching the individual liquid crystal cells. It is understood that it can be used to switch between two light modulation states. Also, the liquid crystal cell can relax at the same time while allowing the liquid crystal device to remain in one of the light modulation states, which is the state in which the liquid crystal device can be actively switched again between the two light modulation states. It is in.

  Thus, both switching from the first modulation state of the liquid crystal device to the second modulation state of the liquid crystal device and switching back to the first modulation state activate the liquid crystal molecules in each liquid crystal cell by applying an electric field. This is achieved using a rapid process for reorienting the target.

  Once the liquid crystal device is relaxed to return from the switched state to the relaxed state in the first light modulation state of the liquid crystal device, the liquid crystal device controls the first liquid crystal cell from the relaxed state to the switched state by The state is switched to the second modulation state again.

  In the liquid crystal device according to various embodiments of the present invention, the liquid crystal molecules of the first and second liquid crystal cells are substantially parallel to each other in the relaxed state of the first and second liquid crystal cells. When the first liquid crystal cell is controlled by applying an electric field inside the liquid crystal cell and transitions to the switching state, the orientation of the liquid crystal molecules in the first liquid crystal cell changes, and again, the liquid crystal molecules are almost parallel to each other. In other common orientation directions, the birefringence of the first liquid crystal cell will change more than in the relaxed state. This will result in a change in the birefringence of the first liquid crystal cell and a change in the total birefringence of the liquid crystal device since the second liquid crystal device remains in a relaxed state.

  Due to this change in the total birefringence of the liquid crystal device, the light intensity level passing through the first and second liquid crystal cells disposed between the intersecting polarizing plates further changes, for example, from the first light modulation state to the second light modulation state. Bring about a transition to

  It should be noted that this birefringence-based control for the transitioned light intensity level is quite different from the polarization control performed by a gradually changing waveguide through a liquid crystal cell, for example in a twisted nematic cell. It is. The use of this birefringence-based control of the liquid crystal device according to various embodiments of the present invention allows a design that is selected such that the first and second light modulation states described above are in a light / dark state. To. This means, for example, whether the simultaneous relaxation of the first and second liquid crystal cells occurs in the dark state or the bright state, depending on the design of the liquid crystal cell. As a result, utilizing the birefringence-based control of the liquid crystal cell allows the characteristics of the liquid crystal cell to adapt to various requirements, such as optical performance, production yield, structural stability, and the like. Furthermore, the sensitivity of deviation between the polarizing plate, the analyzer and the liquid crystal cell is reduced.

Each of the first liquid crystal cell and the second liquid crystal cell is a so-called meaning that the liquid crystal molecules are reoriented in one plane perpendicular to the substrate of the liquid crystal cell when an electric field is applied as described above. It is advantageously configured for “out of plane” switching.
The liquid crystal material of the first and second liquid crystal cells is advantageous in the nematic phase (relative to the expected operating state of the liquid crystal device).

  It is desirable to cause simultaneous relaxation of the first liquid crystal cell and the second liquid crystal cell from the switched state to the relaxed state by a method that is not optically noticeable to the user of the liquid crystal device. For this purpose, the first liquid crystal cell and the second liquid crystal cell may have a birefringence of the first liquid crystal cell during simultaneous relaxation from the switching state to the relaxation state of the first liquid crystal cell and the second liquid crystal cell. And the sum of the birefringence of the second liquid crystal cell are arranged and configured so as to remain substantially constant as the first total birefringence.

  The total birefringence of this device remains constant due to the birefringence correction effect that occurs during the relaxation process in the cell. A characteristic characteristic of the relaxation process in the cell is that the birefringence of the first liquid crystal cell increases / decreases while the birefringence of the second liquid crystal cell decreases / increases, and is constant with respect to the total birefringence. Is to make the relaxation process invisible.

In principle, the liquid crystal device may be controlled by control means arranged outside the liquid crystal device. However, the first liquid crystal cell includes a first control electrode and a second control electrode, and the first control electrode and the second control electrode of the first liquid crystal cell are the first control electrode and the second control electrode of the first liquid crystal cell. The first liquid crystal cell is arranged to be controlled from a relaxed state to a switched state by applying a voltage to the control electrode, and the second liquid crystal cell includes the first control electrode and the first control electrode. The first control electrode and the second control electrode of the second liquid crystal cell by applying a voltage between the first control electrode and the second control electrode of the second liquid crystal cell. The liquid crystal device is advantageously configured to be arranged to allow the two liquid crystal cells to be controlled from the relaxed state to the switched state.
Such control electrodes are advantageously arranged to provide out-of-plane switching of the liquid crystal cell described above.

  According to various embodiments of the present invention, a first birefringence of the first liquid crystal cell is not zero, and a first birefringence of the second liquid crystal cell is substantially zero, and the first liquid crystal cell The second liquid crystal cell is arranged so that the first total birefringence does not become zero.

When the liquid crystal device according to these embodiments is installed between crossed polarizers, it is preferably equal to approximately 45 °, but the transmission direction of one polarizer changing within the range 0 ° <φ <90 ° Provided with at least one optical axis of the first liquid crystal cell or the second liquid crystal cell having an angle φ, the first modulation state is a bright state (when both the first liquid crystal cell and the second liquid crystal cell are in a relaxed state). Will.
Further, in these embodiments, the second birefringence of the first liquid crystal cell is substantially zero, and the second total birefringence is substantially zero. This results in a dark state when the second modulation state is properly placed between the crossed polarizing plates.

  According to an embodiment of the present invention, the first liquid crystal cell is planarly aligned in a relaxed state so that the liquid crystal molecules contained in the first liquid crystal cell are arranged substantially parallel to the pair of first substrates. The second liquid crystal cell has a configuration in which the liquid crystal molecules included in the second liquid crystal cell are vertically aligned in a relaxed state so that the liquid crystal molecules are disposed substantially perpendicular to the pair of second substrates.

  In the following, a liquid crystal cell in a planar alignment configuration in a relaxed state is referred to as a “PA cell”, and a liquid crystal cell in a vertical alignment configuration in a relaxed state is referred to as a “VA cell”. A liquid crystal device in which the first liquid crystal cell is a PA cell and the second liquid crystal cell is a VA cell is called a VA / PA double cell device.

  The liquid crystal molecules contained in the VA cell can advantageously exhibit negative dielectric anisotropy, so that the first control electrode is disposed on the first substrate of the first liquid crystal cell and the second control electrode In the second substrate of the first liquid crystal cell. As a result, the liquid crystal molecules in the VA cell are arranged in a state where the liquid crystal molecules arranged in parallel to the substrate are arranged on a plane from a state in which the liquid crystal molecules are arranged in a vertical direction (a state in which the birefringence is substantially equal to zero) Thus, the birefringence is controlled to a non-zero state.

Further, the liquid crystal molecules of the VA cell can exhibit positive dielectric anisotropy, and in this case, the first and second control electrodes are arranged on the same substrate to create a so-called in-plane magnetic field or fringe electric field.
In the VA cell, when the VA cell is in the switching state, the liquid crystal molecules in the VA cell are oriented in substantially the same direction as the liquid crystal molecules in the PA cell when the PA cell is in the relaxed state in the VA / PA dual cell apparatus. Constructed advantageously.

According to various embodiments of the liquid crystal device according to the present invention, the magnitude of the first birefringence of the first liquid crystal cell is approximately equal to the magnitude of the first birefringence of the second liquid crystal cell.
In particular, the first liquid crystal cell and the second liquid crystal cell may have substantially the same configuration with respect to liquid crystal materials such as cell gap, anchoring characteristics, and electrode structure. This is so that the total birefringence of the liquid crystal device remains constant during the simultaneous relaxation of the liquid crystal cell (during the simultaneous transition from the switched state of the first liquid crystal cell and the second liquid crystal cell to the relaxed state). Would make it easier to design.

  According to a second embodiment of the present invention, there is a method for controlling the operation of the liquid crystal device according to the first embodiment of the present invention, wherein the method allows the first liquid crystal cell to remain in the switched state while the second liquid crystal cell remains in the switching state. The cell is controlled from the relaxed state to the switched state, and the second liquid crystal cell is controlled from the relaxed state to the switched state while the first liquid crystal cell remains in the switched state, and the first liquid crystal cell and the first liquid crystal cell A method comprising the steps of simultaneously controlling two liquid crystal cells to relax from their respective switching states to their respective relaxation states is provided.

  Each of the first liquid crystal cell and the second liquid crystal cell is such that the total birefringence of the liquid crystal device remains substantially constant during relaxation of the first liquid crystal cell and the second liquid crystal cell. , It is advantageously controlled to relax from each switching state to each relaxation state.

  The effects obtained by the various embodiments and the second embodiment of the present invention are substantially the same as those described above for the first embodiment of the present invention.

  As described above, in the first embodiment of the present invention, the first liquid crystal cell and the second liquid crystal cell are arranged as a layered structure so that light passing through the first liquid crystal cell reaches the second liquid crystal cell. It is related with the liquid crystal device containing. Each of the first liquid crystal cell and the second liquid crystal cell can be individually controlled between a relaxed state in which the liquid crystal cell exhibits a first birefringence and a switching state in which the liquid crystal cell exhibits a second birefringence. The transition of the first liquid crystal cell from the state to the switched state results in a change in the total birefringence of the liquid crystal device from the first total birefringence to the second total birefringence, and the liquid crystal device is moved from the first light modulation state. The transition to the second light modulation state and the subsequent transition of the second liquid crystal cell from the relaxed state to the switched state is the total birefringence of the liquid crystal device from the second total birefringence to the first total birefringence. Causing a change in rate, whereby the liquid crystal device transitions back from the second light modulation state to the first light modulation state.

These and other aspects of the invention will be described in more detail with reference to the accompanying drawings, which illustrate exemplary embodiments of the invention.
FIG. 1 is a schematic perspective view of a liquid crystal device according to various embodiments of the present invention. FIG. 2 is a diagram schematically illustrating an exemplary driving method of the liquid crystal device according to the first embodiment of the present invention. 3a to 3d are diagrams schematically showing the state of the liquid crystal device at various stages of the driving method of FIG. 2 according to the first embodiment of the present invention .

  FIG. 1 is a schematic perspective view of a liquid crystal device 1 according to various embodiments of the present invention. This liquid crystal device 1 is layered between crossed polarizing plates 4 and 5 (“polarizing plate” 4 is closest to the light source 7 and “analyzer” 5 is closest to the observer 8). The first liquid crystal cell 2 and the second liquid crystal cell 3 are included. The polarization directions of the polarizing plate 4 and the analyzer 5 are indicated by broken lines in FIG. Each of the first liquid crystal cell and the second liquid crystal cell is individually between a relaxation state in which the liquid crystal cell exhibits a first birefringence and a switching state in which the liquid crystal cell exhibits a second birefringence different from the first birefringence. Can be controlled.

  When the light from the light source 7 that passes through the polarizing plate 4 and is linearly polarized in the direction shown in FIG. 1 passes through the first liquid crystal cell 2 and the second liquid crystal cell 3, the birefringence of the first liquid crystal cell 2. And an overall phase delay, expressed as the sum of the birefringence of the second liquid crystal cell 3. When the total birefringence is zero, the light never passes through the analyzer 5, but when the total birefringence is not zero, at least a part of the light passes through the analyzer 5 and reaches the observer 8. The polarization state of the light is corrected, and the birefringence state of the optical axis is appropriately oriented with respect to the transmission direction of the polarizing plate 4.

  As described above, since the total birefringence corresponds to the sum of the birefringence of the first liquid crystal cell 2 and the birefringence of the second liquid crystal cell 3, the total birefringence is naturally the first liquid crystal cell 2. It is controlled by controlling either the second liquid crystal cell 3 or the second liquid crystal cell 3. By appropriately configuring the first liquid crystal cell 2 and the second liquid crystal cell 3, the liquid crystal device 1 can be actively switched between the dark state and the bright state, and thus can return to the dark state. Means that one state transition in the nematic liquid crystal takes place much faster than with a single cell liquid crystal device, usually very slow, caused by elastic relaxation of the liquid crystal material. As will be described in more detail below, in various embodiments of the liquid crystal device according to the present invention, the first liquid crystal cell 2 and the second liquid crystal cell 3 can be switched if both liquid crystal cells are switched so as to be relaxed. The double cell liquid crystal device 1 is configured to be in the same light modulation state (such as bright or dark). In this way, the liquid crystal device 1 can be relaxed during a switching event, and switching between light modulation states can always be active, which means that liquid crystal molecules along a selected direction. Brought about by the application of electric fields in parallel.

Two exemplary embodiments and driving schemes of the liquid crystal device in FIG. 1 are described below.
First, exemplary driving schemes of the VA / PA double cell device 10 and the VA / PA double cell device 10 will be described with reference to FIGS. 2 and 3a to d. 3A to 3D are cross-sectional views represented by exploded views of the liquid crystal device 1 of FIG. 1 in a cross section taken along the line AA ′ of FIG.

Referring first to FIG. 3a, the VA / PA dual cell apparatus 10 is schematically shown with no control voltage applied. The VA / PA double cell device 10 includes a first liquid crystal cell 11 and a second liquid crystal cell 12 arranged as a layered structure between crossed polarizing plates 4 and 5. The first liquid crystal cell 11 includes a nematic liquid crystal material sandwiched between the first substrate 14 and the second substrate 15. As schematically shown in FIG. 3a, in order to align the liquid crystal molecules 18 of the liquid crystal material in a plane orientation, the first control electrode 16 is formed on the side of the substrate 14, 15 facing this nematic liquid crystal material. And a second control electrode 17 and an alignment layer (not shown). It should be noted that the liquid crystal molecules 18 are arranged at an angle of about 45 ° with respect to the polarization direction of the incident light determined by the polarizing plate 4. In this configuration, the liquid crystal material in the first liquid crystal cell 11 will exhibit a constant non-zero birefringence Δn _PA .

The second liquid crystal cell 12 includes a nematic liquid crystal material sandwiched between the first substrate 19 and the second substrate 20 (the same as the material included in the first liquid crystal cell 11). As schematically shown in FIG. 3a, in order to align the liquid crystal molecules 23 of the liquid crystal material in a vertical (homeotropic) alignment, a first control electrode 21, a second control electrode 22, and an alignment layer (not shown) Are provided on the sides of the substrates 19, 20 facing this nematic liquid crystal material. In this configuration, the liquid crystal material in the second liquid crystal cell 12 will exhibit a zero birefringence Δn _VA = 0.

After introducing the VA / PA double cell device 10 in FIGS. 3a-d, an exemplary drive scheme for controlling the VA / PA double cell device 10 between different light modulation states (dark and light) is provided. 2 and FIGS. 3a-d will now be described.
In FIG. 2, a voltage V _PA supplied across the electrodes 16 and 17 of the first liquid crystal cell 11 (PA cell) and a voltage V _VA supplied across the electrodes 21 and 22 of the second liquid crystal cell 12 (VA cell) are represented. It is shown in the upper two figures as shown.
In the lower figure, the birefringence of the PA cell 11 (broken line) generated by supplying the voltages V _PA and V _VA to the PA cell 11 and the VA cell 12 shown in FIG. The birefringence (dotted line) and the optical response (solid line) of the VA / PA double cell device 10 are shown.

Between time t ₀ and time t ₁ , the voltage V _PA applied to the PA cell 11 is 0 V, and the voltage V _VA applied to the VA cell 12 is also 0 V, and the VA / PA double cell apparatus 10 is planarly aligned. FIG. 3 a shows the liquid crystal molecules 18 of the PA cell 11 in FIG. 3 and the liquid crystal molecules 23 of the PA cell 11 in the vertical alignment. In this state, the total birefringence is not zero (Δn _{tot =} Δn _PA + Δn _VA ≠ 0), and this is because the optical axis of the PA cell 11 is in an appropriate orientation with respect to the polarization direction of the polarizing plate 4 It means that the light passes through the crossed polarizing plates 4 and 5 into which the VA / PA double cell device 10 is inserted. Therefore, the apparatus 10 is in a bright state (BRIGHT) as shown in FIG. 2 in order to transmit incident light from the light source 7.

At time t ₁ , a voltage is applied to the PA cell 11 to reorient the liquid crystal molecules 18 to a vertical alignment, as schematically shown in FIG. 3b. The voltage V _VA applied to the VA cell 12 is still 0 V (or at least low enough to prevent the liquid crystal molecules 23 in the VA cell 12 from being realigned). By applying a voltage to the PA cell 11, when the liquid crystal molecules 18 in the PA cell 11 is changed, the birefringence of the PA cell 11 is switched from the [Delta] n _PA ≠ 0 to [Delta] n _PA * = 0. As shown schematically in FIG. 2, this switching is relatively fast and results in a total birefringence transition such that Δn _tot = Δn _{PA *} + Δn _VA = 0. As a result, the light passing through the polarizing plate 4 in FIG. 3b will pass through the PA cell 11 and VA cell 12 without a change in polarization state, which is illustrated in FIG. This means that it is switched to the dark state (DARK) as further shown in FIG.

At time t _2, the voltage applied to the VA cell 12, the liquid crystal molecules 23, as shown schematically in Figure 3c, reorienting the plane orientation. The voltage V _PA applied to the PA cell 11 is still applied so that the liquid crystal molecules 18 in the PA cell 11 remain in the vertical alignment. By applying a voltage VA cell 12, when the liquid crystal molecules 23 in the VA cell 12 is switched, the birefringence of the VA cell 12 is switched from [Delta] n _VA = 0 to _{Δn VA * = Δn PA ≠ 0} . As shown schematically in FIG. 2, this switching is relatively fast, resulting in a transition of the total birefringence of the cell such that Δn _tot = Δn _{PA *} + Δn _{VA *} = Δn _PA ≠ 0, This transition means that the light again passes through the crossed polarizers 4, 5 into which the VA / PA double cell device 10 is plugged, so this device 10 is shown in FIGS. As shown, it is in a bright state (BRIGHT).

At time t ₃ , the voltage is removed across both PA cell 11 and VA cell 12. As a result, the liquid crystal cells 11 and 12 are simultaneously relaxed to their respective relaxed states. As schematically shown in FIG. 3d, the liquid crystal molecules 18 in the PA cell 11 are relaxed to planar alignment, and the liquid crystal molecules 23 in the VA cell 12 are relaxed to vertical alignment. During this relaxation process, the birefringence of the PA cell 11 increases from Δn _{PA *} = 0 to Δn _PA ≠ 0, and the birefringence of the VA cell 12 increases from Δn _{VA *} = Δn _PA ≠ 0 to Δn _VA = 0. After decreasing and after a certain relaxation time, it returns to the relaxed state shown in FIG. 3a.

During this relaxation, the total birefringence Δn _tot remains substantially constant (and not zero) depending on the configuration of the PA cell 11 and the VA cell 12 and / or the applied control voltage. However, there is only a slight mismatch in the relaxation of the PA cell 11 and the VA cell 12, causing a change in transmitted light intensity, shown as a small “kink” 25 in FIG. Since this change can only take place in the order of ms and only in the bright state of the VA / PA dual cell device 10 in FIGS. 3a-d, this change will be hardly visible to the observer 8. . This change is expected to be avoided by optimizing the characteristics of the cell parameters and the driving method, or at least the influence can be ignored. While the liquid crystal device 1 is in the bright state, the change is expected. , Advantageous for applications with simultaneous relaxation (occurring at time t ₃ ). This is achieved using the VA / PA dual cell device 10 of FIGS.

Finally, at time _{t 4,} the voltage is again applied to the PA cell 11 returns the VA / PA dual cell system 10 in the dark state (DARK) shown in Figure 3b.

Moreover, those skilled in the art, without excessive degree of burden, can be selected suitable liquid crystal material, cell size, orientation layer, and more complicated driving method.

  Those skilled in the art will recognize that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and changes, for example VA (s) in a VA / PA or VA / VA class of dual cell devices comprising a liquid crystal material with positive dielectric anisotropy due to an in-plane electric field or fringe region Cell switching is possible within the scope of the appended claims.

  In the claims, the word “comprising” does not exclude other elements or steps, and the “singular” indefinite article does not exclude a plurality. The mere fact that inventive features are recited in mutually different dependent claims does not indicate that a combination of these specified inventive matters is not used.

Claims (7)

A liquid crystal device for modulating light passing therethrough ,
The first liquid crystal cell及beauty second liquid crystal cell, the light passing through the first liquid crystal cell is arranged as a layered structure, such as reaching the second liquid crystal cell,
A pair of crossed polarizing plates are disposed on both sides of the layered first liquid crystal cell and the second liquid crystal cell,
The total birefringence exhibited by the liquid crystal device is the sum of the birefringence of the first liquid crystal cell and the birefringence of the second liquid crystal cell;
Before Symbol first liquid crystal cell Le has a relaxed OFF state indicating that birefringence is not zero, an individually controllable between a switching ON state indicating that birefringence is substantially zero ,
The second liquid crystal cell is individually controllable between a relaxation OFF state indicating that the birefringence is substantially zero and a switching ON state indicating that the birefringence is not zero.
The first liquid crystal cell and the second liquid crystal cell are
The second left liquid crystal cells of the relaxed OFF state, by the first liquid crystal cell (at time t ₁₎ is the transition from the relaxed OFF state to switch ON state, the total birefringence of the liquid crystal device is zero The first total birefringence is not changed to a second total birefringence that is substantially zero, and the liquid crystal device changes from a light modulation state in a bright state to a light modulation state in a dark state ,
Later, while the first liquid crystal cell is switched ON, by the second liquid crystal cell (at time t ₂₎ transitions from the relaxed OFF state to switch ON state, the total birefringence of the liquid crystal device rate is returned from the second total birefringence to the first total birefringence, the liquid crystal device, a transition from said light modulation states in a dark state to return to the light modulation states of the bright state,
Thereafter, (the time at t ₃₎ the first liquid crystal cell from the switching ON state to alleviate the OFF state, and, by the simultaneous relaxation of the second liquid crystal cell from the switch ON state to the relaxed OFF state, the total of the liquid crystal device Since the birefringence remains substantially constant and equal to the first total birefringence, the liquid crystal device remains in the bright light modulation state during this simultaneous relaxation.
O urchin, it is arranged and configured, it liquid crystal device according to claim. The first liquid crystal cell includes a first control electrode and a second control electrode, and the first control electrode and the second control electrode of the first liquid crystal cell are the first control electrode and the second control electrode of the first liquid crystal cell. Arranged to allow the first liquid crystal cell to be controlled from the relaxed OFF state to the switched ON state by applying a voltage between and
The second liquid crystal cell includes a first control electrode and a second control electrode, and the first control electrode and the second control electrode of the second liquid crystal cell are the first control electrode and the second control electrode of the second liquid crystal cell. the liquid crystal device according to claim 1 by applying a voltage, characterized by being arranged to allow the controller controls the second liquid crystal cell from the relaxed OFF state to switch the oN state between the. The first liquid crystal cell has a planar alignment configuration in a relaxed OFF state so that liquid crystal molecules contained in the first liquid crystal cell are arranged substantially parallel to a pair of substrates of the first liquid crystal cell , and
The second liquid crystal cell has a vertical alignment configuration in a relaxed OFF state so that liquid crystal molecules contained in the second liquid crystal cell are arranged substantially perpendicular to a pair of substrates of the second liquid crystal cell. The liquid crystal device according to claim 1 or 2 . The liquid crystal molecules contained in the second liquid crystal cell exhibit negative dielectric anisotropy,
4. The method according to claim 3 , further comprising: a first control electrode disposed on the first substrate of the second liquid crystal cell; and a second control electrode disposed on the second substrate of the second liquid crystal cell. The liquid crystal device described. The liquid crystal molecules included in the second liquid crystal cell exhibit a positive dielectric anisotropy, and the liquid crystal device is disposed on the first substrate of the second liquid crystal cell to generate an in-plane electric field. The liquid crystal device according to claim 3 , comprising first and second control electrodes. A method for controlling the operation of the liquid crystal device according to any one of claims 1 to 5 , wherein the method comprises:
While allowing the second liquid crystal cell remains relaxed OFF state, the first liquid crystal cell controls from the relaxed OFF state to switch ON state,
While the first liquid crystal cell is to remain in the switched ON state, and controls the second liquid crystal cell from the relaxed OFF state to switch ON state, and,
A method comprising the steps of simultaneously controlling the first liquid crystal cell and the second liquid crystal cell so as to relax from each switching ON state to each relaxation OFF state. Each of the first liquid crystal cell and the second liquid crystal cell is such that the total birefringence of the liquid crystal device remains substantially constant during relaxation of the first liquid crystal cell and the second liquid crystal cell. The method according to claim 6 , wherein control is performed so as to relax from each switching ON state to each relaxation OFF state.

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