JP2010224407A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To simultaneously attain high response speed and high contrast ratio. <P>SOLUTION: The liquid crystal display device includes: a liquid crystal layer which shows a Kerr effect; a first back electrode 108a which faces one principal plane of the liquid crystal layer; and a plurality of first parts which face the one principal plane, are electrically insulated from the first back electrode 108a, and electrically connected to each other, wherein the plurality of first parts have: second back electrodes 108b each of which has the shape extending in the first direction and which are arranged in the second direction crossing the first direction; second front electrodes 208a which face the other principal plane of the liquid crystal layer; and a plurality of second parts which faces the other principal plane, are electrically insulated from the first front electrode 208a and electrically connected to each other, wherein the plurality of second parts are equipped with: second front electrodes 208b each of which has the shape extending in a third direction crossing the first direction, and which are arranged in a fourth direction crossing the third direction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a liquid crystal display technology.

  Patent Documents 1 and 2 describe liquid crystal display devices using the Kerr effect. The Kerr effect is an effect in which the refractive index of a transparent isotropic medium exhibits anisotropy proportional to the square of the external electric field. A liquid crystal material exhibiting the Kerr effect exhibits a high-speed electric field response of several milliseconds or less because of the short correlation length of liquid crystal molecules. Known liquid crystal phases exhibiting the Kerr effect include a cholesteric blue phase, a smectic blue phase, and a pseudo isotropic phase.

  In a liquid crystal display device using the Kerr effect, for example, a common electrode and a pixel electrode are provided on a substrate. The common electrode is, for example, a continuous film spreading without a gap. The pixel electrode is, for example, a comb-like conductor pattern facing the common electrode with an insulating film interposed therebetween.

  When a voltage is applied between the pixel electrode and the common electrode, in the liquid crystal layer, a transverse electric field is generated in which electric lines of force are substantially perpendicular to the normal line of the substrate and the length direction of the comb teeth. The transmittance of each pixel changes according to the strength of the lateral electric field.

JP 2005-202390 A JP 2008-112021 A

As described above, the liquid crystal display device using the Kerr effect can achieve a high response speed. However, the present inventors have found that there is room for improvement in the contrast ratio in the liquid crystal display device using the Kerr effect when carrying out the present invention.
An object of the present invention is to achieve a high response speed and a high contrast ratio at the same time.

  According to the first aspect of the present invention, a liquid crystal layer showing a Kerr effect, a first back electrode facing one main surface of the liquid crystal layer, and facing the one main surface of the liquid crystal layer, the first back surface A second back electrode electrically insulated from the electrode, comprising a plurality of first portions electrically connected to each other, each of the plurality of first portions having a shape extending in the first direction; A second back electrode arranged in a second direction intersecting the first direction, a second front electrode facing the other main surface of the liquid crystal layer, and facing the other main surface of the liquid crystal layer, A second front electrode electrically insulated from the first front electrode, the second front electrode including a plurality of second portions electrically connected to each other, wherein the plurality of second portions intersects the first direction; Each has a shape extending in the third direction, arranged in a fourth direction intersecting the third direction. The liquid crystal display device and a second front electrode.

  According to the second aspect of the present invention, a liquid crystal layer exhibiting a Kerr effect, a first back electrode facing one main surface of the liquid crystal layer, and facing the one main surface of the liquid crystal layer, the first back surface A second back electrode electrically insulated from the electrode, comprising a plurality of first portions electrically connected to each other, each of the plurality of first portions having a shape extending in the first direction; A second back electrode arranged in a second direction intersecting the first direction, a first front electrode facing the other main surface of the liquid crystal layer, and facing the other main surface of the liquid crystal layer, A second front electrode electrically insulated from the first front electrode, comprising a plurality of second portions electrically connected to each other, wherein the plurality of second portions extend in the first direction; Each having a shape, wherein one or more of the plurality of second portions is adjacent to the plurality of first portions. A second region sandwiched between two adjacent ones of the plurality of second portions so as to at least partially face the first region sandwiched between the two or at least one of the plurality of first portions. There is provided a liquid crystal display device comprising a second front electrode arranged in the second direction so as to at least partially face a region.

  According to the present invention, it is possible to simultaneously achieve a high response speed and a high contrast ratio.

1 is a plan view schematically showing a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is a cross-sectional view schematically showing a liquid crystal display panel of the liquid crystal display device shown in FIG. 1. FIG. 6 is another cross-sectional view schematically showing the liquid crystal display panel of the liquid crystal display device shown in FIG. 1. FIG. 4 is a perspective view schematically showing a back substrate included in the liquid crystal display panel shown in FIGS. 2 and 3. FIG. 4 is a perspective view schematically showing a front substrate included in the liquid crystal display panel shown in FIGS. 2 and 3. Sectional drawing which shows schematically an example of the electric field which the liquid crystal display panel which concerns on a comparative example forms in a liquid-crystal layer. Sectional drawing which shows schematically an example of the electric field which the liquid crystal display panel shown in FIG.2 and FIG.3 forms in a liquid-crystal layer. The graph which shows an example of the luminance distribution of the liquid crystal display panel shown in FIG. The graph which shows an example of the luminance distribution of the liquid crystal display panel shown in FIG. Sectional drawing which shows schematically the modification of the liquid crystal display panel shown in FIG.2 and FIG.3. Sectional drawing which shows schematically the other modification of the liquid crystal display panel shown in FIG.2 and FIG.3. The figure which shows schematically the pixel which the liquid crystal display device which concerns on the 2nd aspect of this invention contains. The perspective view which shows schematically the front substrate of the liquid crystal display panel containing the pixel shown in FIG. Sectional drawing which shows schematically the liquid crystal display panel which the liquid crystal display device which concerns on the 3rd aspect of this invention contains.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same referential mark is attached | subjected to the component which exhibits the same or similar function through all the drawings, and the overlapping description is abbreviate | omitted.

First, the first aspect of the present invention will be described.
FIG. 1 schematically shows a liquid crystal display device according to the first embodiment. 2 to 5 schematically show components included in the liquid crystal display device of FIG.

  Note that FIG. 1 is a perspective view of rear electrodes 108a and 108b and front electrodes 208a and 208b, which will be described later, in order to facilitate understanding of their arrangement. In FIG. 1 to FIG. 5, some components are omitted for simplification.

  The liquid crystal display device shown in FIG. 1 is an active matrix liquid crystal display device. The liquid crystal display device includes a liquid crystal display panel 1, a backlight (not shown) installed to face the liquid crystal display panel 1, a scanning line driving circuit 2, a signal line driving circuit 3 connected to the liquid crystal display panel 1, and an auxiliary device. The capacitor line driving circuit 4 and a controller 5 connected to the driving circuits 2 to 4 are included.

  The liquid crystal display panel 1 includes a back substrate 10 and a front substrate 20. A frame-shaped seal layer (not shown) is interposed between the back substrate 10 and the front substrate 20. A space surrounded by the back substrate 10, the front substrate 20, and the seal layer is filled with a liquid crystal material, and the liquid crystal material forms a liquid crystal layer 30. On the outer surface of the back substrate 10, a linear polarizer 50R is installed. A linear polarizer 50 </ b> F is installed on the outer surface of the front substrate 20.

  The back substrate 10 includes a light transmissive substrate 100. The substrate 100 is, for example, a glass substrate or a plastic substrate.

  On the substrate 100, scanning lines 101a and auxiliary capacitance lines 101b are arranged. The scanning lines 101a and the auxiliary capacitance lines 101b each extend in the X direction, and are alternately arranged in the Y direction that intersects the X direction.

  The X direction and the Y direction are parallel to one main surface of the substrate 100 and intersect each other. A Z direction to be described later is a direction perpendicular to the X direction and the Y direction.

  Each of the scanning lines 101a includes a protruding portion protruding in the Y direction. These protrusions are used as gate electrodes of thin film transistors described later.

  Each of the storage capacitor lines 101b includes a protruding portion protruding in the Y direction. These protrusions are used as electrodes of a capacitor to be described later.

  The scanning line 101a and the auxiliary capacitance line 101b can be formed in the same process. Moreover, as these materials, a metal or an alloy can be used, for example.

  The scanning line 101 a and the auxiliary capacitance line 101 b are covered with an insulating film 102. As the insulating film 102, for example, a silicon oxide film can be used.

  On the insulating film 102, the semiconductor layer 103 is arranged corresponding to the gate electrode. Each of these semiconductor layers 103 intersects with the gate electrode. The semiconductor layer 103 is made of, for example, amorphous silicon.

  A portion of the gate electrode, the semiconductor layer 103, and the insulating film 102 located between the gate electrode and the semiconductor layer 103, that is, the gate insulating film forms a thin film transistor. These thin film transistors are used as the switch 104.

  Note that in this embodiment, the switch 104 is an n-channel thin film transistor. A channel protective layer and an ohmic layer (not shown) are formed on each semiconductor layer 103.

  The switch 104 may be a p-channel thin film transistor. Alternatively, the switch 104 may be another switching element such as a diode.

  On the insulating film 102, a signal line 105a, a source electrode 105b, and a feed line 105c are further arranged.

  Each of the signal lines 105a extends in the Y direction, and is arranged in the X direction corresponding to the column formed by the switch 104. The signal line 105 a covers the drain of the semiconductor layer 103 included in the switch 104. That is, part of the signal line 105 a is a drain electrode connected to the switch 104.

  The source electrode 105 b is arranged corresponding to the switch 104. The source electrode 105 b covers the source of the switch 104.

  The source electrode 105 b is arranged corresponding to the switch 104. The source electrode 105b covers the source of the switch 104 and faces the storage capacitor line 101b. The source electrode 105b, the auxiliary capacitance line 101b, and the insulating film 102 interposed therebetween form a capacitor 106.

  Each of the power supply lines 105c extends in the Y direction and is arranged in the X direction. Each of the feeder lines 105c may extend in the X direction and may be arranged in the Y direction.

  On the insulating film 102, first back electrodes 108 a are further arranged corresponding to the switches 104. Each of these back electrodes 108a at least partially covers the power supply line 105c. As a material of the back electrode 108a, for example, ITO (indium tin oxide) can be used. As shown in FIG. 4, when the back electrodes 108a adjacent to each other in the Y direction are joined to each other, the power supply line 105c may be omitted.

  The back electrode 108 a is covered with a back insulating layer 109. The insulating layer 109 is a transparent inorganic layer such as a silicon oxide film and a silicon nitride film. A transparent organic layer may be used as the insulating layer 109.

  On the insulating layer 109, the second back electrode 108b is arranged corresponding to the first back electrode 108a. These back electrodes 108b are insulated from the back electrode 108a, and at least partially cover the source electrode 105b. As a material of the back electrode 108b, for example, ITO can be used.

  The back electrode 108b includes a plurality of first portions that are electrically connected to each other. Each of these first portions has a shape extending in the first direction, and is arranged in a second direction intersecting the first direction. The first and second directions are directions perpendicular to the Z direction. Here, as an example, the back electrode 108b is a comb-shaped electrode that includes a plurality of comb-tooth portions each having a shape extending in the X direction and arranged in the Y direction.

  The dimension L1 in the first direction of the first portion is, for example, in the range of 5 μm to 1000 μm, and typically in the range of 20 μm to 600 μm. The dimension W1 of the first portion in the second direction is, for example, in the range of 0.3 μm to 20 μm, and typically in the range of 1 μm to 5 μm. The ratio L1 / W1 between the dimension L1 and the dimension W1 is, for example, in the range of 10 to 300, and typically in the range of 30 to 100. The center line distance P1 of the first portion is, for example, in the range of 0.6 μm to 50 μm, and typically in the range of 1.5 μm to 20 μm.

  A first region sandwiched between adjacent first portions faces the back electrode 108a. That is, the orthogonal projection of the first region and the back electrode 108a on the main surface of the substrate 100 at least partially overlaps. The first portion itself may or may not face the back electrode 108a. That is, the back electrode 108a may be a continuous film extending without a gap, or may be a film provided with a slit corresponding to the first portion. In this case, if the back electrodes 108a and 108b can be electrically insulated from each other, the insulating layer 109 can be omitted.

  The front substrate 20 faces the main surface of the back substrate 10 on the back electrode 108b side. The front substrate 20 is separated from the rear substrate 10 at the positions of the first portion and the first region.

  The front substrate 20 includes a light transmissive substrate 200. The substrate 200 is, for example, a glass substrate or a plastic substrate.

  On the substrate 200, scanning lines 201a and auxiliary capacitance lines 201b are arranged corresponding to the scanning lines 101a and auxiliary capacitance lines 101b, respectively. The scanning lines 201a and the auxiliary capacitance lines 201b each extend in the X direction, and are alternately arranged in the Y direction that intersects the X direction.

  Each of the scanning lines 201a includes a protruding portion protruding in the Y direction. These protrusions are used as gate electrodes of thin film transistors described later.

  Each of the storage capacitor lines 201b includes a protruding portion protruding in the Y direction. These protrusions are used as electrodes of a capacitor to be described later.

  The scanning line 201a and the auxiliary capacitance line 201b can be formed in the same process. Moreover, as these materials, a metal or an alloy can be used, for example.

  The scanning line 201 a and the auxiliary capacitance line 201 b are covered with an insulating film 202. As the insulating film 202, for example, a silicon oxide film can be used.

  On the insulating film 202, the semiconductor layer 203 is arranged corresponding to the gate electrode. Each of these semiconductor layers 203 intersects with the gate electrode. The semiconductor layer 203 is made of amorphous silicon, for example.

  A portion of the gate electrode, the semiconductor layer 203, and the insulating film 202 located between the gate electrode and the semiconductor layer 203, that is, the gate insulating film forms a thin film transistor. These thin film transistors are used as the switch 204.

  Note that in this embodiment, the switch 204 is an n-channel thin film transistor. A channel protective layer and an ohmic layer (not shown) are formed on each semiconductor layer 203.

  The switch 204 may be a p-channel thin film transistor. Alternatively, the switch 204 may be another switching element such as a diode.

  On the insulating film 202, a signal line 205a, a source electrode 205b, and a power supply line 205c are further arranged.

  Each of the signal lines 205a extends in the Y direction, and is arranged in the X direction corresponding to the column formed by the switch 204. The signal line 205 a covers the drain of the semiconductor layer 203 included in the switch 204. That is, part of the signal line 205 a is a drain electrode connected to the switch 204.

  The source electrode 205b is arranged corresponding to the switch 204. The source electrode 205 b covers the source of the switch 204.

  The source electrode 205b is arranged corresponding to the switch 204. The source electrode 205b covers the source of the switch 204 and faces the storage capacitor line 201b. The source electrode 205b, the auxiliary capacitance line 201b, and the insulating film 202 interposed therebetween form a capacitor 206.

  Each of the feeder lines 205c extends in the Y direction and is arranged in the X direction. Each of the power supply lines 205c may extend in the X direction and may be arranged in the Y direction.

  On the insulating film 202, first front electrodes 208 a are further arranged corresponding to the switches 204. Each of these front electrodes 208a at least partially covers the feeder line 205c. As a material of the front electrode 208a, for example, ITO can be used. As shown in FIG. 5, when the front electrodes 208a adjacent in the Y direction are joined to each other, the power supply line 205c may be omitted.

  The front electrode 208a is covered with a front insulating layer 209. The insulating layer 209 is a transparent inorganic layer such as a silicon oxide film and a silicon nitride film, for example. A transparent organic layer may be used as the insulating layer 209.

  On the insulating layer 209, the second front electrode 208b is arranged corresponding to the first front electrode 208a. These front electrodes 208b are insulated from the front electrodes 208a, and at least partially cover the source electrodes 205b. As a material of the front electrode 208b, for example, ITO can be used.

  The front electrode 208b includes a plurality of second portions that are electrically connected to each other. Each of these second portions has a shape extending in the first direction, and is arranged in the second direction. Here, as an example, the front electrode 208b is a comb-shaped electrode that includes a plurality of comb-tooth portions each having a shape extending in the X direction and arranged in the Y direction.

  The dimension L2 in the first direction of the second part is, for example, in the range described above for the dimension L1. The dimension W2 in the second direction of the second portion is, for example, in the range described above for the dimension W1. The ratio L2 / W2 between the dimension L2 and the dimension W2 is, for example, in the range described above for the ratio L1 / W1. The distance P2 between the center lines of the second portion is set, for example, within the range described above for the distance P1 between the center lines.

  The dimension L2 may be equal to or different from the dimension L1. The dimension W2 may be equal to or different from the dimension W1. The ratio L2 / W2 may be equal to or different from the ratio L1 / W1. The centerline distance P2 may be equal to or different from the centerline distance P1. Here, as an example, it is assumed that the dimension L2 is equal to the dimension L1, the dimension W2 is equal to the dimension W1, the ratio L2 / W2 is equal to the ratio L1 / W1, and the centerline distance P2 is equal to the centerline distance P1.

  The second region sandwiched between the adjacent second portions faces the front electrode 208a. That is, the orthogonal projection of the second region and the front electrode 208a on the main surface of the substrate 200 at least partially overlaps. The second part itself may or may not face the front electrode 208a. That is, the front electrode 208a may be a continuous film spreading without a gap, or may be a film provided with a slit corresponding to the second portion.

  One or more of the second portions are at least partially facing a first region sandwiched between two adjacent ones of the first portion. Alternatively, one or more of the first portions are at least partially facing a second region sandwiched between two adjacent portions of the second portion. That is, the orthogonal projection of the second portion and the first region on the main surface of the substrate 100 or 200 at least partially overlaps, or the first portion and the second region on the main surface of the substrate 100 or 200 The orthogonal projections of at least partially overlap. Here, as an example, each of the orthogonal projections of the second portion onto the main surface of the substrate 100 or 200 is interposed between two adjacent projections of the first portion onto the main surface, or Each of the orthogonal projections of the first portion onto the main surface of the substrate 100 or 200 is interposed between two adjacent projections of the second portion onto the main surface. It is assumed that the orthographic projection of the first part and the orthographic projection of the second part on the surface are separated from each other.

  The electrodes 108a and 208a facing each other, the electrodes 108b and 208b interposed therebetween, the capacitors 106 and 206 connected thereto, and the switches 104 and 204 constitute a pixel circuit. Between the substrates 100 and 200, these pixel circuits are two-dimensionally arranged, for example, in the X direction and the Y direction. The pixel circuit may not include one or both of the capacitors 106a and 206.

  At least one of the substrates 10 and 20 may further include a black matrix. The black matrix is, for example, a light shielding layer that is interposed between the substrates 100 and 200 and has openings corresponding to the first and second portions and the first and second regions. The black matrix is, for example, a lattice or stripe pattern layer. As the black matrix material, for example, a metal such as chromium or an alloy can be used.

  Further, at least one of the substrates 10 and 20 may further include a color filter. For example, the color filter is interposed between the substrates 100 and 200 and includes a red colored layer, a green colored layer, and a blue colored layer. These colored layers form, for example, a stripe arrangement corresponding to the columns formed by the pixel circuits. These colored layers may form other arrangements such as a delta arrangement and a square arrangement.

  The back substrate 10 and the front substrate 20 are arranged so that the main surface of the back substrate 10 on the back electrode 108b side faces the main surface of the front substrate 20 on the front electrode 208b side. A frame-shaped seal layer (not shown) is interposed between the back substrate 10 and the front substrate 20. The sealing layer bonds the back substrate 10 and the front substrate 20 together. An adhesive can be used as the material for the sealing layer.

  A granular spacer is interposed between the back substrate 10 and the front substrate 20, or the back substrate 10 and / or the front substrate 20 further includes a columnar spacer. These spacers form a gap having a substantially constant thickness between the back substrate 10 and the front substrate 20 at positions corresponding to the first and second portions and the first and second regions.

  A space surrounded by the back substrate 10, the front substrate 20, and the adhesive layer is filled with a liquid crystal material. This liquid crystal material forms the liquid crystal layer 30.

  The liquid crystal layer 30 exhibits a Kerr effect. That is, the liquid crystal material exhibits a liquid crystal phase exhibiting a Kerr effect such as a cholesteric blue phase, a smectic blue phase, and a pseudo isotropic phase. When the liquid crystal material has a cholesteric blue phase, the liquid crystal layer 30 exhibits selective reflection in addition to exhibiting the Kerr effect.

  The liquid crystal material exhibiting a cholesteric blue phase is typically a mixture of a liquid crystal compound and a chiral agent. This mixture may further contain other materials. For example, when a liquid crystal compound, specifically, a polymer material having a molecular weight much higher than that of a low molecular liquid crystal compound is added to this mixture, the temperature range showing a blue phase can be widened.

  Here, as an example, it is assumed that the liquid crystal layer 30 exhibits a behavior similar to that of an optically isotropic layer when no voltage is applied, that is, when a black image is displayed. Furthermore, for simplification, the liquid crystal layer 30 plays a role as a half-wave plate for all wavelengths in the visible region when displaying a white image.

The Kerr constant of the liquid crystal material is, for example, in the range of 1 × 10 ⁻¹¹ mV ^{−2 to} 1 × 10 ⁻⁸ mV ⁻² . When the Kerr constant of the liquid crystal material is small, it is difficult to achieve a high contrast ratio.

  In the liquid crystal display panel 1, each pixel PX includes the pixel circuit described above and a portion of the liquid crystal layer 30 interposed between the electrodes 108a and 208a of the pixel circuit. The back substrate 10 and the front substrate 20 and the liquid crystal layer 30 and the sealing layer interposed therebetween form a liquid crystal cell.

  The linear polarizer 50R is, for example, an absorption linear polarizer. Here, as an example, it is assumed that the transmission axis of the linear polarizer 50R forms an angle of 45 ° clockwise with respect to the Y direction when the liquid crystal display panel 1 is viewed from the back side.

  The linear polarizer 50F is, for example, an absorption linear polarizer. Here, as an example, it is assumed that the transmission axis of the linear polarizer 50F is perpendicular to the transmission axis of the linear polarizer 50R.

  Scan lines 101 a and 201 a are connected to the scan line driving circuit 2. The scanning line driving circuit 2 sequentially supplies a first scanning voltage for closing the switches 104 and 204 to the scanning lines 101a and 201a, respectively. The scanning line driving circuit 2 supplies the second scanning voltage that opens the switches 104 and 204 to the scanning lines 101a and 201a to which the first scanning voltage is not supplied.

  The signal line driving circuit 3 is connected with signal lines 105a and 205a and power supply lines 105c and 205c. The signal line driving circuit 3 supplies a signal voltage having a magnitude corresponding to the video signal to the signal lines 105a and 205a. Further, the signal line driving circuit 3 supplies a display voltage, which is typically a constant voltage, to the power supply lines 105c and 205c. Here, the signal line driving circuit 3 includes a voltage source for supplying a display voltage to the power supply lines 105c and 205c. However, the display line is supplied to the power supply lines 105c and 205c. The voltage source may be provided separately from the signal line driver circuit 3.

  Auxiliary capacitance lines 101b and 201b are connected to the auxiliary capacitance line drive circuit 4. When the polarity of the signal voltage output from the signal line driving circuit 3 to the signal line 105a is inverted from positive to negative, the auxiliary capacitance line driving circuit 4 is a pixel to which the signal voltage is supplied in synchronization with the polarity inversion. The potential of the auxiliary capacitance line 101b connected to PX is changed from the first potential to the second potential. When the signal line driving circuit 3 inverts the polarity of the signal voltage output to the signal line 105a from negative to positive, the auxiliary circuit to which the pixel PX to which the signal voltage is to be supplied is connected in synchronization with the polarity inversion. The potential of the capacitor line 101b is changed from the second potential to the first potential. Further, when the polarity of the signal voltage output from the signal line drive circuit 3 to the signal line 205a is inverted from positive to negative, the auxiliary capacitance line drive circuit 4 supplies these signal voltages in synchronization with the polarity inversion. The potential of the auxiliary capacitance line 201b to which the power pixel PX is connected is changed from the first potential to the second potential. When the signal line driving circuit 3 inverts the polarity of the signal voltage output to the signal line 205a from negative to positive, the auxiliary to which the pixel PX to which the signal voltage is to be supplied is connected in synchronization with the polarity inversion. The potential of the capacitor line 201b is changed from the second potential to the first potential. Here, “the polarity of the signal voltage” means the polarity of the difference between the signal voltage and the display voltage.

  The drive circuits 2 to 4 may be mounted on a COG (chip on glass). Alternatively, the drive circuits 2 to 4 may be mounted by TCP (tape carrier package).

  The controller 5 is connected to the drive circuits 2 to 4. The controller 5 controls the operation of the drive circuits 2 to 4.

  A backlight (not shown) illuminates the liquid crystal display panel 1 from the back substrate 10 side. Typically, the backlight emits white light.

  Here, the term “liquid crystal display device” is used to mean an assembly including the liquid crystal display panel 1, the drive circuits 2 to 4, the controller 5, and the backlight. "Includes the assembly in which one or more of the linear polarizers 50R and 50F, the drive circuits 2 to 4, the controller 5 and the backlight are omitted.

  As described above, this liquid crystal display device uses the Kerr effect. Therefore, this liquid crystal display device achieves a high response speed.

  In this liquid crystal display device, the back substrate 10 includes back electrodes 108a and 108b, and the front substrate 20 includes front electrodes 208a and 208b. The rear electrodes 108a and 108b and the front electrodes 208a and 208b are arranged as described above. Therefore, as will be described below, this liquid crystal display device achieves a high contrast ratio.

  FIG. 6 is a simplified cross-sectional view of a liquid crystal display panel according to a comparative example. FIG. 7 is a cross-sectional view schematically illustrating the liquid crystal display panel 1 described with reference to FIGS. 1 to 5.

  The liquid crystal display panel 1 shown in FIG. 6 is the same as the liquid crystal display panel 1 shown in FIG. 7 except that the front substrate 20 is composed only of the light transmissive substrate 200. 6 and 7, broken lines indicate examples of electric lines of force of the electric field generated in the liquid crystal layer 30 by the liquid crystal display panel 1.

  FIG. 8 is a graph showing an example of the luminance distribution in the case where the liquid crystal display panel 1 shown in FIG. 6 is illuminated from the back side and a white image is displayed thereon. FIG. 9 is a graph showing an example of the luminance distribution in the case where the liquid crystal display panel 1 shown in FIG. 7 is illuminated from the back side and a white image is displayed thereon. In FIG. 8, the positions A to F on the horizontal axis correspond to the positions A to F shown in FIG. 6, respectively, and the vertical axis represents the luminance. Further, in FIG. 9, the positions A to F on the horizontal axis correspond to the positions A to F shown in FIG. 7, respectively, and the vertical axis represents the luminance.

  When the liquid crystal display panel 1 shown in FIG. 6 is illuminated from the back side, linearly polarized light whose electric field vector oscillation direction is parallel to the transmission axis of the linear polarizer 50R is incident on the liquid crystal layer 30. This linearly polarized light can be regarded as a pair of linearly polarized light having the same amplitude and phase and whose electric field vector oscillation directions are perpendicular to each other.

  When no voltage is applied between the electrodes 108a and 108b, assuming that the retardation applied to the linearly polarized light is zero, the linear polarizer 50F has the vibration direction of the electric field vector on the transmission axis of the linear polarizer 50R. Parallel linearly polarized light is incident thereon.

  The vibration direction of the electric field vector of the linearly polarized light is perpendicular to the transmission axis of the linear polarizer 50F. Therefore, when no voltage is applied between the electrodes 108a and 108b, the light transmitted through the liquid crystal layer 30 is absorbed by the linear polarizer 50F. That is, the light transmitted through the liquid crystal layer 30 is not perceived by the observer. The liquid crystal display panel 1 displays a black image in this way.

  When a voltage is applied between the electrodes 108a and 108b, as shown in FIG. 6, in the vicinity of the edge along the X direction in the first part of the electrode 108b (hereinafter referred to as “the edge of the first part”), A transverse electric field in which the electric lines of force are perpendicular to the Z direction, here, an electric field line is perpendicular to the Z direction and parallel to the Y direction is generated. When this lateral electric field is generated, birefringence occurs in the Y direction in the vicinity of the edge of the first portion. As a result, the retardation is increased in the vicinity of the edge of the first portion. For example, in the vicinity of the edge of the first portion, the liquid crystal layer 30 exhibits a function as a half-wave plate whose slow axis is parallel to the Y direction.

  Therefore, in the vicinity of the edge of the first portion, the linearly polarized light transmitted by the linear polarizer 50R is transmitted through the liquid crystal layer 30, whereby the oscillation direction of the electric field vector is rotated by 90 °. That is, in the vicinity of the edge of the first portion, the liquid crystal layer 30 emits linearly polarized light in which the vibration direction of the electric field vector is parallel to the transmission axis of the linear polarizer 50F toward the linear polarizer 50F. Since this linearly polarized light can be transmitted through the linear polarizer 50F, it can be perceived by an observer. The liquid crystal display panel 1 displays a white image in this way.

  As described above, when displaying a white image, a horizontal electric field is generated in the liquid crystal layer 30. Thereby, for example, in the vicinity of the edge of the first portion, the function as a half-wave plate whose slow axis is parallel to the Y direction is exhibited.

  However, in this case, the electric field generated at a position away from the edge of the first portion is such that the lines of electric force are not parallel to the Y direction or have low strength. Therefore, the function as a half-wave plate whose slow axis is parallel to the Y direction cannot be exhibited except in the vicinity of the edge of the first portion. Accordingly, as shown in FIG. 8, the liquid crystal display panel 1 shown in FIG. 6 achieves high luminance at positions B and E in the vicinity of the edge of the first part, but positions C and D far from the edge of the first part. Then, high brightness cannot be achieved. For this reason, the liquid crystal display device including the liquid crystal display panel 1 shown in FIG. 6 cannot achieve a high contrast ratio.

  The liquid crystal display panel 1 shown in FIG. 7 can display a black image on the same principle as described for the liquid crystal display panel 1 shown in FIG. When displaying a white image on the liquid crystal display panel 1 shown in FIG. 7, in addition to applying a voltage between the back electrodes 108a and 108b, a voltage can also be applied between the front electrodes 208a and 208b. In this way, a lateral electric field can be generated in the vicinity of the edge of the first portion, and in addition, an edge along the X direction of the second portion of the electrode 208b (hereinafter referred to as “the edge of the second portion”). A horizontal electric field can also be generated in the vicinity of. Therefore, as shown in FIG. 9, the liquid crystal display panel 1 shown in FIG. 7 achieves high luminance at positions B and E in the vicinity of the edge of the first portion, and in addition, near the edge of the second portion. High brightness is also achieved at positions C and D. Therefore, the liquid crystal display device including the liquid crystal display panel 1 shown in FIG. 7 achieves a high contrast ratio.

  The liquid crystal display panel 1 described with reference to FIGS. 1 to 5 can be variously modified as described below.

  10 and 11 are cross-sectional views schematically showing modifications of the liquid crystal display panel 1 shown in FIGS.

  In the liquid crystal display panel 1 shown in FIG. 10, one of the edges of each first portion faces the second portion, and the other faces the second region. One of the edges of each second part faces the first part, and the other faces the first region. Except this, the liquid crystal display panel 1 shown in FIG. 10 is the same as the liquid crystal display panel 1 described with reference to FIGS.

  When this configuration is adopted, the same effect as described for the liquid crystal display panel 1 described with reference to FIGS. 1 to 5 can be obtained. In addition, when this configuration is adopted, it is easy to reduce the pitch of the arrangement formed by the edges of the first part and the edges of the second part in the Y direction.

  In the liquid crystal display panel 1 shown in FIG. 11, the dimension of the first part in the Y direction is different from the dimension of the second part in the Y direction. The two edges of each first part face the second region, and the two edges of each second part face the first part. Except this, the liquid crystal display panel 1 shown in FIG. 11 is the same as the liquid crystal display panel 1 described with reference to FIGS. Even when this configuration is adopted, the same effect as described for the liquid crystal display panel 1 described with reference to FIGS. 1 to 5 can be obtained.

  Next, a 2nd aspect is demonstrated. The second mode is the same as the first mode except that the following configuration is adopted for the liquid crystal display panel 1.

  That is, in the liquid crystal display device according to the second aspect, each second portion of the second front electrode 208b has a shape extending in a direction intersecting the length direction of the first portion of the second back electrode 108b. Yes. These second portions are arranged in a direction intersecting with the direction in which the first portions of the second back electrode 108b are arranged.

  In the example shown in FIGS. 12 and 13, each of the second portions of the second front electrode 208b has a shape extending in the Y direction, and is arranged in the X direction. That is, the first part and the second part are arranged so that their length directions are orthogonal to each other.

  When this configuration is adopted, the orthogonal projection of the edge of the first portion onto the main surface of the substrate 100 or 200 and the orthogonal projection of the edge of the second portion onto the main surface intersect each other. At positions corresponding to these intersections, high luminance cannot be achieved when displaying a white image.

  However, with the exception of the positions corresponding to these intersections, high brightness can be achieved when displaying a white image at positions corresponding to the edges of the first part and the second part. Accordingly, when the first part and the second part are arranged so that their length directions intersect each other, the first part and the second part are arranged so that their length directions are parallel to each other. A high contrast ratio can be achieved, although not as much as in the case of the arrangement.

  Further, when the first portion and the second portion are arranged so that their length directions intersect with each other, the first portion and the second portion are arranged so that their length directions are parallel to each other. As in the case of the arrangement, the position alignment of the substrates 10 and 20 is not required to be highly accurate. That is, the former is easier to manufacture the liquid crystal display panel 1 than the latter.

  Next, a 3rd aspect is demonstrated. The third aspect is the same as the first or second aspect, except that the following configuration is adopted.

  That is, the liquid crystal display device according to the third aspect further includes a retardation layer 60 interposed between the second back electrode 108b and the second front electrode 208b, as shown in FIG. The retardation layer 60 is separated from the back substrate 10 at the position of the back electrode 108b, and is separated from the front substrate 20 at the position of the front electrode 208b. The retardation layer 60 serves as a half-wave plate, for example, with respect to light having a specific wavelength λ.

  The liquid crystal layer 30 is partitioned into a first liquid crystal layer 30R and a second liquid crystal layer 30F by a retardation layer 60. The liquid crystal layer 30R is interposed between the back electrode 108b and the retardation layer 60, exhibits the Kerr effect, and selectively reflects right or left circularly polarized light. The liquid crystal layer 30F is interposed between the front electrode 208b and the retardation layer 60, exhibits the Kerr effect, the circularly polarized light selectively reflected by the liquid crystal layer 30R and the rotation direction of the electric field vector, and the wavelength is the same. Selectively reflects equal circularly polarized light. The wavelength of light selectively reflected by the liquid crystal layers 30R and 30F is substantially equal to the wavelength λ. Here, as an example, the liquid crystal layers 30R and 30F selectively reflect right circularly polarized light having the wavelength λ.

  The liquid crystal display device does not include the linear polarizers 50R and 50F and the backlight. Instead, the liquid crystal display device further includes a black layer 70 facing the back substrate 10.

  This liquid crystal display device is a reflective liquid crystal display device using selective reflection. As will be described below, this liquid crystal display device displays a bright image when no voltage is applied, and displays a dark image when a voltage is applied.

  When this liquid crystal display device is illuminated with white light from the front side with no voltage applied between the electrodes 108a and 108b and no voltage applied between the electrodes 208a and 208b, of the light incident on the liquid crystal layer 30F. The right circularly polarized light having the wavelength λ is selectively reflected by the liquid crystal layer 30F, and the left circularly polarized light having the wavelength λ and light having other wavelengths are transmitted through the liquid crystal layer 30F.

  Of the light transmitted through the liquid crystal layer 30 </ b> F, the left circularly polarized light having the wavelength λ is converted into right circularly polarized light by transmitting through the retardation layer 60. The right circularly polarized light is selectively reflected by the liquid crystal layer 30R, is converted to left circularly polarized light by passing through the retardation layer 60, and then passes through the liquid crystal layer 30F.

  On the other hand, the remaining light transmitted through the liquid crystal layer 30F passes through the retardation layer 60, the liquid crystal layer 30R, and the back substrate 10 in this order, and is absorbed by the black layer 70.

  That is, this liquid crystal display device selectively reflects right circularly polarized light and left circularly polarized light having a wavelength λ, and absorbs light having other wavelengths. The liquid crystal display device thus displays a bright image.

  When the liquid crystal display device is illuminated with white light from the front side with a voltage applied between the electrodes 108a and 108b and a voltage applied between the electrodes 208a and 208b, the light incident on the liquid crystal layer 30F is And 30R, the liquid crystal layer 30F, the retardation layer 60, the liquid crystal layer 30R, and the back substrate 10 are transmitted in this order and absorbed by the black layer 70. That is, this liquid crystal display device absorbs almost all light. In this way, the liquid crystal display device displays a dark image.

  As described above, this liquid crystal display device selectively reflects both right circularly polarized light and left circularly polarized light having a wavelength λ during bright display. Therefore, this liquid crystal display device achieves a higher contrast ratio compared to a similar liquid crystal display device, except that the front substrate 20 is composed only of the light transmissive substrate 200 and does not include the retardation layer 60.

  The technique described with reference to FIGS. 1 to 5, 7, and 9 to 13 can be applied to devices other than the transmissive liquid crystal display device. For example, these techniques may be applied to a reflective liquid crystal display device or a transflective liquid crystal display device.

  These liquid crystal display devices described with reference to FIGS. 1 to 5, 7 and 9 to 14 employ an active matrix driving method. Instead, other driving methods such as a passive matrix driving method and a segment driving method may be adopted.

  Examples of the present invention will be described below.

<Example 1>
In this example, the liquid crystal display device described with reference to FIGS. 1 to 5 was manufactured by the following method.

  In manufacturing the back substrate 10, first, the scanning lines 101 a and the auxiliary capacitance lines 101 b were formed on the glass substrate 100. Chromium was used as a material for the scanning line 101a and the auxiliary capacitance line 101b.

  Next, the scanning line 101a, the auxiliary capacitance line 101b, and the glass substrate 100 were covered with an insulating film 102 made of silicon oxide. An amorphous silicon layer was formed on the insulating film 102 and patterned to obtain a semiconductor layer 103. Thereafter, a channel protective layer (not shown) made of silicon nitride was formed on part of each semiconductor layer 103, and an ohmic layer (not shown) was formed on the semiconductor layer 103 and the channel protective layer.

  Next, the signal line 105 a, the source electrode 105 b, and the power supply line 105 c were formed over the insulating film 102. On the insulating film 102, a back electrode 108a made of ITO was formed so as to at least partially cover the power supply line 105c. The back electrode 108a was formed by patterning using a photolithography technique.

  Thereafter, an insulating layer 109 made of silicon nitride was deposited on the signal line 105a, the source electrode 105b, the feeder line 105c, and the back electrode 108a. A contact hole is provided in the insulating layer 109 at a position corresponding to the source electrode 105b.

  Next, a back electrode 108b made of ITO was formed on the insulating layer 109 so that they filled the previous contact hole. The back electrode 108b was formed by forming an ITO layer as a continuous film on the insulating layer 109 and patterning the ITO layer using a photolithography technique. The distance between the back electrode 108b and the back electrode 108a was 0.6 μm. Further, the dimension W1 in the Y direction of the first portion of the back electrode 108b was 1 μm, and the center-to-center distance P1 of these first portions was 2 μm.

  The front substrate 20 was formed by substantially the same method as described for the back substrate 10 except that a black matrix, a color filter, and columnar spacers (all not shown) were provided.

  That is, the black matrix was obtained by forming a chromium film on the glass substrate 200 and patterning it.

  The color filter was formed using photolithography using a photosensitive acrylic resin mixed with a pigment after forming the signal line 205a, the source electrode 205b, and the power supply line 205c and before forming the electrode 208a. . As the color filter, a stripe arrangement composed of a red colored layer, a green colored layer, and a blue colored layer was formed.

  The columnar spacers were formed on the color filters and at the positions of the signal lines 205a using photolithography. The height of the columnar spacer was 5 μm, and the size of the bottom surface was 5 μm × 10 μm.

  After cleaning the electrodes 108b and 208b, an epoxy adhesive, which is a material for the seal layer, was applied to the main surface of the front substrate 20 in a frame shape using a dispenser. Note that the frame formed by the adhesive layer was provided with an opening to be used as an injection port later. Subsequently, the back substrate 10 and the front substrate 20 were arranged so that the back electrode 108b and the front electrode 208b face each other. After alignment, the back substrate 10 and the front substrate 20 were bonded together, and further the adhesive was cured by heating to 160 ° C. in a pressurized state.

  Next, the empty cell thus obtained was carried into a vacuum chamber, and the inside of the cell was evacuated. Thereafter, a liquid crystal material was injected from the inlet into the cell. As liquid crystal materials, nematic liquid crystal JC1041 manufactured by Chisso Corporation, nematic liquid crystal 5CB manufactured by Aldrich Corporation, and chiral agent ZLI-4572 manufactured by Merck Co., Ltd. were used in proportions of 48.2 mol%, 47.4 mol% and 4.4 mol%, respectively. The contained composition was used.

  Thereafter, the inlet was sealed with an epoxy adhesive. A liquid crystal cell was obtained as described above. The liquid crystal cell had a cell gap of about 5 μm.

  Next, the linearly polarizing plate 50 </ b> R was attached to the outer surface of the back substrate 10. In addition, a linear polarizing plate 50 </ b> F was attached to the outer surface of the front substrate 20. Specifically, the linear polarizer 50R is attached to the back substrate 10 so that the transmission axis forms an angle of 45 ° clockwise with respect to the Y direction when the liquid crystal display panel 1 is viewed from the back side. . The linear polarizer 50F was attached to the front substrate 20 so that the transmission axis was orthogonal to the transmission axis of the linear polarizer 50F when the liquid crystal display panel 1 was viewed from the back side.

  Thereafter, the drive circuits 2 to 4 and the like were connected to the display panel 1, and the drive circuits 2 to 4 were connected to the controller 5. Further, the display panel 1 and the backlight were combined. The liquid crystal display device was completed as described above.

  Next, the liquid crystal display device was driven and its performance was examined. Specifically, each of the first voltage applied between the back electrode 108b and the back electrode 108a of each pixel PX and the second voltage applied between the front electrode 208b and the front electrode 208a is performed 30 times per second. The response time was measured. Each of the first and second voltages was varied between three values of -15V, 0V and + 15V. The first voltage and the second voltage were controlled so as to always have the same magnitude. The contrast ratio was determined from the brightness when each applied voltage was −15 V, the brightness when each applied voltage was 0 V, and the brightness when each applied voltage was +15 V. As a result, a response time of 1 millisecond and a contrast ratio of 500: 1 could be achieved.

<Example 2>
In this example, a liquid crystal display device was manufactured by the same method as described in Example 1 except that the front substrate 20 was composed of only the glass substrate 200, the black matrix, the color filter, and the columnar spacers.

  Next, this display device was driven in the same manner as described in Example 1, and the performance was examined. As a result, the contrast ratio was 200: 1.

<Example 3>
In this example, the liquid crystal display device described with reference to FIG. 14 was manufactured by the following method.

  The back substrate 10 was manufactured in the same manner as that manufactured in Example 1 except that it further includes a columnar spacer. The columnar spacer was formed on the insulating layer 109 at the position of the signal line 105a using photolithography. The height of the columnar spacer was 5 μm, and the size of the bottom surface was 10 μm × 10 μm.

  The front substrate 20 was the same as that manufactured in Example 1 except that it did not include a color filter, the columnar spacer had a height of 5 μm, and the bottom surface was 10 μm × 10 μm. .

  A half-wave plate was used as the retardation layer 60. The retardation layer 60 was provided with a plurality of through holes. These through holes were formed such that when the substrates 10 and 20 were bonded together with the retardation layer 60 interposed therebetween, each through hole was separated from the columnar spacer and positioned on the signal line 105a or 205a.

  After cleaning the electrode 108b, an epoxy adhesive, which is a material for the seal layer, was applied to the main surface of the retardation layer 60 in a frame shape using a dispenser. Note that the frame formed by the adhesive layer was provided with an opening to be used as an injection port later. Next, the back substrate 10 and the retardation layer 60 are arranged so that the back electrode 108b faces the retardation layer 60, and each through hole provided in the retardation layer 60 is separated from the columnar spacer and on the signal line 105a. Arranged to be located. After alignment, the back substrate 10 and the retardation layer 60 were bonded together, and further the adhesive was cured by heating to 160 ° C. in a pressurized state.

  Subsequently, the electrode 208b was cleaned, and an epoxy adhesive, which is a material for the seal layer, was applied to the main surface of the front substrate 20 in a frame shape using a dispenser. The frame formed by this adhesive layer was also provided with an opening that will be used later as an injection port. Next, the back substrate 10 and the retardation layer 60 bonded to each other and the front substrate 20 are arranged so that the back electrode 108b and the front electrode 208b face each other with the retardation layer 60 interposed therebetween, and the retardation layer 60 The respective through holes provided were arranged so as to be separated from the columnar spacers of the front substrate 20 and located on the signal line 205a. After alignment, the back substrate 10 and the front substrate 20 were bonded together with the retardation layer 60 interposed therebetween, and further the adhesive was cured by heating to 160 ° C. in a pressurized state.

  Next, a liquid crystal material was injected into the empty cell thus obtained by the same method as in Example 1, and the injection port was sealed with an epoxy adhesive. A liquid crystal cell was obtained as described above.

  Next, the black layer 70 was attached to the outer surface of the back substrate 10. Further, the drive circuits 2 to 4 are connected to the display panel 1, and the drive circuits 2 to 4 are connected to the controller 5. The liquid crystal display device was completed as described above.

  The liquid crystal display device was illuminated from the front side with natural light having a wavelength equal to the circularly polarized light selectively reflected by the liquid crystal layers 30a and 30b, and the reflectance was measured. As a result, the reflectance when no voltage was applied was 60%.

<Example 4>
In this example, a liquid crystal display device is manufactured by the same method as that described in Example 3, except that the front substrate 20 is composed only of the glass substrate 200, the black matrix, and the columnar spacers, and the retardation layer 60 is omitted. did.

  Next, the reflectance of the liquid crystal display device was measured by the same method as described in Example 3. The reflectance when no voltage was applied was 40%.

  DESCRIPTION OF SYMBOLS 1 ... Liquid crystal display panel, 2 ... Scanning line drive circuit, 3 ... Signal line drive circuit, 4 ... Auxiliary capacitance line drive circuit, 5 ... Controller, 10 ... Back substrate, 20 ... Front substrate, 30 ... Liquid crystal layer, 30F ... Liquid crystal Layer: 30R: Liquid crystal layer, 50F: Linear polarizer, 50R: Linear polarizer, 60: Phase difference layer, 70: Black layer, 100: Light transmissive substrate, 101a: Scan line, 101b: Auxiliary capacitance line, 102: Insulating film 103 ... Semiconductor layer 104 ... Switch 105a ... Signal line 105b ... Source electrode 105c ... Feed line 106 ... Capacitor 108a ... Back electrode 108b ... Back electrode 109 ... Back insulating layer 200 ... Light Transmission substrate, 201a ... scanning line, 201b ... auxiliary capacitance line, 202 ... insulating film, 203 ... semiconductor layer, 204 ... switch, 205a ... signal line, 205b ... source electrode, 205c ... Wire, 206 ... capacitor, 208a ... front electrode, 208b ... front electrode, 209 ... front side insulating layer, PX ... pixel.

Claims (5)

A liquid crystal layer exhibiting the Kerr effect;
A first back electrode facing one main surface of the liquid crystal layer;
A second back electrode facing the one main surface of the liquid crystal layer and electrically insulated from the first back electrode, comprising a plurality of first portions electrically connected to each other; The first portion has a shape extending in the first direction, each having a second back electrode arranged in a second direction intersecting the first direction;
A second front electrode facing the other main surface of the liquid crystal layer;
A second front electrode facing the other main surface of the liquid crystal layer and electrically insulated from the first front electrode, comprising a plurality of second portions electrically connected to each other; Each of the second portions has a shape extending in a third direction intersecting with the first direction, and includes a second front electrode arranged in a fourth direction intersecting with the third direction. A liquid crystal layer exhibiting the Kerr effect;
A first back electrode facing one main surface of the liquid crystal layer;
A second back electrode facing the one main surface of the liquid crystal layer and electrically insulated from the first back electrode, comprising a plurality of first portions electrically connected to each other; The first portion has a shape extending in the first direction, each having a second back electrode arranged in a second direction intersecting the first direction;
A first front electrode facing the other main surface of the liquid crystal layer;
A second front electrode facing the other main surface of the liquid crystal layer and electrically insulated from the first front electrode, comprising a plurality of second portions electrically connected to each other; Each of the second portions has a shape extending in the first direction, and one or more of the plurality of second portions are sandwiched between two adjacent ones of the plurality of first portions; The first portion so as to face at least partly, or so that one or more of the plurality of first portions face at least partly a second region sandwiched between two adjacent parts of the plurality of second portions. A liquid crystal display device comprising a second front electrode arranged in two directions.   3. The liquid crystal display device according to claim 2, wherein one of a pair of edges along the first direction of each of the plurality of second portions faces the first portion and the other faces the first region.   A back insulating layer interposed between the first back electrode and the liquid crystal layer; and a front insulating layer interposed between the first front electrode and the liquid crystal layer. 3. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is interposed between the back insulating layer and the liquid crystal layer, and the second front electrode is interposed between the front insulating layer and the liquid crystal layer.   The liquid crystal layer further includes a retardation layer interposed between the second back electrode and the second front electrode, and the liquid crystal layer is interposed between the second back electrode and the retardation layer, thereby providing a Kerr effect. A first liquid crystal layer that selectively reflects right or left circularly polarized light, and a circularly polarized light that is interposed between the second front electrode and the retardation layer, exhibits the Kerr effect, and is selectively reflected by the first liquid crystal layer The liquid crystal display device according to claim 1, further comprising: a second liquid crystal layer that selectively reflects circularly polarized light having the same rotation direction of the electric field vector and the same wavelength.

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