JP2008310179A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display which provides excellent display quality both in a transmissive region and in a reflective region, and allows the manufacturing process of the display to be facilitated. <P>SOLUTION: The liquid crystal display 50 includes a liquid crystal interposed between a pair of substrates 110, 210, the transmissive region 62 and the reflective region 64. The one substrate 110 out of the pair of substrates 110, 210 is equipped with a pixel electrode 182 for transmissive display and a common electrode 178 for transmissive display arranged on the transmissive region 62, and a pixel electrode 190 for reflective display arranged on the reflective region 64. The other substrate 210 out of the pair of substrates 110, 210 is equipped with a common electrode 222 for reflective display arranged on the reflective region 64. The pair of substrates 110, 210 are equipped respectively with polarizing layers 106, 206 and one or more retardation layers 108, 208 on the outside of the substrates. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device, and more particularly to a transflective liquid crystal display device having a retardation layer.

  Conventionally, as a transflective liquid crystal display device, an electrode is provided on each of a pair of substrates sandwiching liquid crystal, and a method of driving liquid crystal by an electric field between the electrodes, that is, a so-called vertical electric field driving method is generally used. It was. When the cell gap (the thickness of the liquid crystal layer) is the same in the transmissive region and the reflective region, the optical path in the liquid crystal layer is twice that in the transmissive region in the reflective region. In this case, for example, it is necessary to use 1/2 wavelength (1/2 wavelength) light modulation in the transmission region and 1/4 wavelength (1/4 wavelength) light modulation in the reflection region. This is achieved by making the cell gap different between regions.

  By the way, a transflective liquid crystal display device of so-called lateral electric field drive system such as FFS (Fringe Field Switching) and IPS (In-Plane Switching) known for transmissive display with a high viewing angle, high contrast, and high-speed response has been put into practical use. If so, it is possible to expect a better display quality than in the past. In the horizontal electric field method, a pixel electrode and a common electrode are provided on the same substrate, and the alignment state is controlled by rotating liquid crystal molecules by an electric field generated between both electrodes.

  When the above-described configuration for adjusting the cell gap is applied to the lateral electric field driving method, the transmission region is normally black, and the reflection region is normally white. For this reason, a phase difference of ½ wavelength is given to the transmission region and the reflection region.

  For example, Patent Document 1 describes that in a transflective liquid crystal display device of a horizontal electric field drive system, a half-wave plate is provided on the entire surface between a lower substrate and a polarizing plate on the lower substrate. Yes. In this case, since the reflection plate is located above the half-wave plate in the reflection region, the half-wave plate acts only on the transmission region.

  Further, in Patent Document 2, in the transflective IPS system, as it is, when the reflective area is brightly displayed, the transmissive area is darkly displayed or vice versa, and the reflective area and the transmissive area are applied differently. It has been pointed out that it becomes voltage dependent. In order to solve this problem, it is described that a built-in retardation plate having a retardation amount of ½ wavelength is formed in the reflection region, and the retardation amount by the liquid crystal layer in the reflection region is set to ¼ wavelength. Yes.

  Patent Document 2 describes a method of forming a built-in retardation plate. According to this, an alignment film that determines the slow axis direction of the built-in retardation plate is prepared, and an organic solvent containing a liquid crystal having a photoreactive acrylic group at the molecular end and a reaction initiator is applied thereon. Heat to remove organic solvent. Thereby, the photoreactive liquid crystal is aligned according to the alignment treatment direction of the alignment film. In this way, a built-in retardation plate is formed. Patent Document 2 describes that the built-in retardation plate is patterned and formed only on the reflective display portion.

JP 2003-344837 A JP 2005-338256 A

  As described above, the transflective liquid crystal display device of the horizontal electric field drive system has insufficient contrast in the reflection area, and the display area has a transmission area that is normally black and the reflection area is normally white. There's a problem.

  Further, when a phase difference is given to the transmission region and the reflection region, the built-in retardation plate or the external retardation plate can be used as described above. However, the built-in retardation plate formation process has an insufficient aspect for practical use.

  For example, when the built-in retardation plate is patterned only in the reflection region by the above-described forming method, the controllability of the end shape (end surface shape) of the retardation plate is not so good. For this reason, in one phase difference plate, an optical characteristic differs in an edge part and a center part, and it may become a problem on display quality. Further, there may be a problem in relation to the patterning accuracy of other elements of the liquid crystal display device. For example, when a positional shift occurs between the built-in retardation plate and the light shielding film and the edge of the retardation plate protrudes from the light shielding film, a region having a transmittance different from that of the periphery is formed at the end portion.

  An object of the present invention is to provide a liquid crystal display device which can obtain a good display quality in both the transmissive region and the reflective region and can facilitate the manufacturing process.

  The liquid crystal display device according to the present invention is a liquid crystal display device in which liquid crystal is sandwiched between a pair of substrates and has a transmission region and a reflection region, and one of the pair of substrates is provided in the transmission region. A transmissive display pixel electrode and a transmissive display common electrode, and a reflective display pixel electrode provided in the reflective region, wherein the other of the pair of substrates is provided in the reflective region. A reflective display common electrode is provided, and each of the pair of substrates includes a polarizing layer and one or more retardation layers on the outside.

  According to the above configuration, for example, compared to a configuration in which the pixel electrode and the common electrode are provided on the same substrate for both the transmissive region and the reflective region, the contrast and the like in both the transmissive region and the reflective region, that is, good display quality Is obtained. Further, since the retardation layer is provided outside the substrate and is provided in both the transmission region and the reflection region, it is easy to form the retardation layer.

  The one or more retardation layers of the one substrate include a retardation layer whose slow axis is substantially orthogonal to any one of the one or more retardation layers of the other substrate, and the slow axes are substantially orthogonal to each other. The retardation layer preferably has substantially the same amount of retardation.

  According to the above configuration, since the display light in the transmissive region passes through both of the retardation layers whose slow axes are substantially orthogonal to each other, the actions of the two retardation layers are compensated for each other in the transmissive region. In addition, since the display light in the reflection region passes through only one of the retardation layers having the slow axes substantially orthogonal to each other, the one retardation layer is substantially designed according to the characteristics of the reflection region. It will be good. Therefore, the retardation layer can be easily designed and formed.

  The one or more retardation layers of the one substrate include a retardation layer having a slow axis substantially perpendicular to a rubbing direction defining an alignment direction of the liquid crystal, and a slow axis substantially perpendicular to the rubbing direction. It is preferable that the retardation layer having the above and the liquid crystal layer in the transmission region have substantially the same amount of retardation.

  According to the above configuration, the retardation generated in the liquid crystal layer in the transmissive region is compensated by the retardation layer having the slow axis substantially orthogonal to the rubbing direction. For this reason, a favorable dark display (black display) can be obtained in the transmissive region.

  The one or more retardation layers of the one substrate include a first retardation layer, and the one or more retardation layers of the other substrate are substantially the same as a rubbing direction in which a slow axis defines the alignment direction of the liquid crystal. The first retardation layer has a slow axis substantially perpendicular to the slow axis of the second retardation layer and the rubbing direction, and the amount of retardation is the second retardation layer. It is preferable that the phase difference amount of the layer is substantially equal to the sum of the phase difference amount of the liquid crystal layer in the transmission region.

  According to the above configuration, both the retardation due to the second retardation layer and the retardation due to the transmission region of the liquid crystal layer can be compensated for by one retardation layer (first retardation layer). For this reason, a structure can be simplified and formation becomes easy.

  It is preferable that the polarizing layer of the one substrate and the polarizing layer of the other substrate are provided so that absorption axes are substantially orthogonal to each other.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a schematic diagram illustrating a liquid crystal display device 50 according to an embodiment. The liquid crystal display device 50 includes, for example, an element substrate 100, a counter substrate 200 disposed to face the element substrate 100, a liquid crystal layer 300 sandwiched between the substrates 100 and 200, a backlight device 72, and a drive circuit 74. It is comprised including. The liquid crystal display device 50 is a transflective type, and can transmit the transmissive display light 92 using the light emitted from the backlight device 72 (backlight light) and also reflects the external light to form the reflective display light 94. Is possible. In FIG. 1, both display lights 92 and 94 are schematically shown.

  FIG. 1 illustrates a configuration in which the backlight device 72 is disposed on the element substrate 100 side and the display lights 92 and 94 are extracted from the substrate 200 side. In FIG. 1, the backlight device 72 and the element substrate 100 are illustrated as being separated from each other, but they can be brought into close contact with each other.

  The drive circuit 74 schematically illustrates circuits that supply signals, potentials, and the like to various elements in the substrates 100 and 200. The drive circuit 74 is connected to the element substrate 100 in the example of FIG. 1, but can also be connected to the counter substrate 200 or both the substrates 100 and 200. A part of the driving circuit 74 can be provided on one or both of the substrates 100 and 200.

  2 and 3 are a cross-sectional view and a plan view for explaining the pixel 60, respectively. FIG. 3 shows only some elements.

  The liquid crystal display device 50 includes a plurality of pixels 60. The plurality of pixels 60 can be variously arranged such as a delta arrangement or a matrix arrangement. Each pixel 60 has a transmissive region 62 that forms transmissive display light 92 and a reflective region 64 that forms reflective display light 94. Here, a case where the transmission region 62 is configured by the FFS method and the reflection region 64 is configured by the ECB (Electrically Controlled Birefringence) method is illustrated.

  As illustrated in FIG. 2, the liquid crystal display device 50 includes a pair of substrates 110 and 210 arranged to face each other, and a liquid crystal layer 300 is sandwiched between the pair of substrates 110 and 210. The substrates 110 and 210 can be formed of a transparent substrate such as a glass plate. The substrate 110 and the substrate 210 are provided with various elements exemplified below to constitute the element substrate 100 and the counter substrate 200, respectively.

  The thickness of the liquid crystal layer 300, in other words, the distance between the substrates 100 and 200 corresponds to the cell gap. The cell gap can be adjusted by the size of the spacer 302 between the substrates 100 and 200.

  The liquid crystal display device 50 includes a buffer layer 112 on the liquid crystal layer 300 side of the substrate 110. The liquid crystal display device 50 includes semiconductor layers 114 and 116, an insulating film 118, gate electrodes 120, 122, 124 and 126, and a gate wiring 140 on the liquid crystal layer 300 side of the buffer layer 112.

  The semiconductor layers 114 and 116 are both disposed on the buffer layer 112. Here, the semiconductor layer 114 is provided in the transmissive region 62, and the semiconductor layer 116 is provided in the reflective region 64. The insulating film 118 is disposed on the buffer layer 112 so as to cover the semiconductor layers 114 and 116. The gate electrodes 120, 122, 124, 126 are disposed on the insulating film 118.

  The gate electrodes 120 and 122 are opposed to the semiconductor layer 114 with the insulating film 118 interposed therebetween. Thus, a TFT (Thin Film Transistor) 128 is formed including a stacked structure of the semiconductor layer 114, the insulating film 118, and the gate electrode 120, and includes a stacked structure of the semiconductor layer 114, the insulating film 118, and the gate electrode 122. A TFT 130 is configured. In this case, the insulating film 118 forms a gate insulating film in the TFTs 128 and 130. The TFTs 128 and 130 are electrically connected in series. Similarly, the TFT 134 includes a stacked structure of the semiconductor layer 116, the insulating film 118, and the gate electrode 124, and the TFT 136 includes a stacked structure of the semiconductor layer 116, the insulating film 118, and the gate electrode 126. The TFTs 134 and 136 are electrically connected in series.

  The TFTs 128, 130, 134, and 136 are generally called pixel transistors. Note that the expression “source” is used for an element electrically connected to pixel electrodes 182 and 190 described later, but the expression “drain” may be used for the element.

  The gate wiring 140 is disposed on the insulating film 118. The gate electrodes 120, 122, 124, and 126 are connected to the gate wiring 140 at positions not shown.

  Here, when the TFTs 128 and 130 are collectively referred to as a transmissive display switching element 132, and the TFTs 134 and 136 are collectively referred to as a reflective display switching element 138, the gate electrodes 120 and 122 are the control electrodes of the transmissive display switching element 132. The gate electrodes 124 and 126 can be called control electrodes of the reflective display switching element 138.

  Each of the switching elements 132 and 138 may be formed of other configurations, for example, one or three or more TFT elements, one or more MIM (Metal Insulator Metal) elements, and the like. In addition, the switching elements 132 and 138 can be configured differently.

  The liquid crystal display device 50 includes a storage capacitor line 142, a common electrode line 146, and an interlayer insulating film 148 on the insulating film 118. The storage capacitor line 142 is disposed in the reflective region 64 so as to face a part of the semiconductor layer 116 with the insulating film 118 interposed therebetween. A storage capacitor element 144 for display is configured. In this case, the insulating film 118 forms a capacitor element insulating film in the storage capacitor element 144, and the part of the semiconductor layer 116 forms a counter electrode of the storage capacitor element 144. The interlayer insulating film 148 covers the gate electrodes 120, 122, 124, 126, the gate wiring 140, the storage capacitor wiring 142, and the common electrode wiring 146.

  The liquid crystal display device 50 includes a drain wiring 160, source electrodes 162 and 164, a common electrode relay electrode 166, a passivation film 168, and an insulating layer 170 on the liquid crystal layer 300 side of the substrate 110.

  FIG. 2 illustrates a case where the drain wiring 160 and the electrodes 162, 164, and 166 are configured in a three-layer structure. In the example of FIG. 2, the drain wiring 160 is disposed on the interlayer insulating film 148 and is electrically connected to the drain regions of the TFTs 128 and 134 through the contact holes 150 and 154.

  The source electrodes 162 and 164 and the relay electrode 166 are all disposed on the interlayer insulating film 148 in the illustration of FIG. Further, the source electrode 162 is electrically connected to the source region of the TFT 130 through the contact hole 152, the source electrode 164 is electrically connected to the source region of the TFT 136 through the contact hole 156, and the relay electrode 166 is connected to the contact hole. It is electrically connected to the common electrode wiring 146 through 158.

  In the illustration of FIG. 2, the passivation film 168 is disposed on the interlayer insulating film 148 so as to cover the wiring 160 and the electrodes 162, 164, 166. The insulating layer 170 is stacked on the passivation film 168 in the illustration of FIG. The surface of the insulating layer 170 on the liquid crystal layer 300 side is formed flat in the transmissive region 62 and uneven in the reflective region 64.

  The liquid crystal display device 50 includes a transmissive display common electrode 178, an insulating layer 180, a transmissive display pixel electrode 182, a reflective layer 188, and a reflective display pixel electrode 190 on the liquid crystal layer 300 side of the substrate 110. Yes.

  The transmissive display common electrode 178 can be made of a transparent conductive material such as ITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide). The common electrode 178 is provided in each transmission region 62. The common electrode 178 can be provided for each transmission region 62 (that is, for each pixel 60). For example, the common electrode 178 of the transmission region 62 adjacent in the row direction can be connected.

  As illustrated in FIG. 2, the common electrode 178 is disposed on the flat surface of the insulating layer 170 and is electrically connected to the relay electrode 166 through the contact hole 172. As a result, a potential is applied from the common electrode wiring 146 to the common electrode 178 via the relay electrode 166.

  The insulating layer 180 is disposed on the insulating layer 170 so as to cover the transmissive display common electrode 178, and is also disposed on the unevenness of the insulating layer 170 in the reflective region 64. The insulating layer 180 on the unevenness has an uneven shape following the unevenness of the base.

  The transmissive display pixel electrode 182 is provided in each transmissive region 62, is stacked on the transmissive display common electrode 178 via the insulating layer 180, and is electrically connected to the source electrode 162 via the contact hole 174. ing. As a result, a potential is applied from the drain wiring 160 to the pixel electrode 182 through the switching element 132 and the source electrode 162. The pixel electrode 182 can be made of a transparent conductive material such as ITO or IZO.

  A plurality of slits (or grooves) 184 are provided in the pixel electrode 182. Here, as shown in FIG. 3, each slit 184 is inclined about 5 ° to 10 ° with respect to the row direction and extends to the right, and these slits 184 are arranged in the column direction. In this case, a rubbing direction R of an alignment film (not shown) described later is set to be substantially parallel to the row direction, that is, the longitudinal direction of the slit 184 (in other words, the long side direction). For example, the rubbing direction R forms an angle of about 5 ° to 10 °.

  The setting of the slit 184 in the longitudinal direction is not limited to the above example. In addition, here, the shape in which the end of the slit 184 does not reach the outer edge of the pixel electrode 182 is illustrated, but the end of the slit 184 reaches the outer edge of the pixel electrode 182 so that the pixel electrode 182 has a comb shape. May be.

  As described above, the transmissive display pixel electrode 182 is stacked on the transmissive display common electrode 178 via the insulating layer 180. Therefore, a storage capacitor element 186 for transmissive display is configured by a stacked structure of the pixel electrode 182, the insulating layer 180, and the common electrode 178.

  The reflective layer 188 is provided in the reflective region 64 and is disposed on the unevenness of the insulating layer 180. The reflective layer 188 has an uneven shape following the unevenness of the insulating layers 180 and 170. The reflective layer 188 reflects external light. At this time, the external light can be scattered by the uneven shape. The reflective layer 188 can be made of a material that can reflect external light (here, visible light), such as an aluminum-neodymium alloy, silver, or the like.

  The reflective display pixel electrode 190 is provided in each reflective region 64 and is disposed on the unevenness of the reflective layer 188. Here, the pixel electrode 190 has a concavo-convex shape following the concavo-convex shape of the reflective layer 188 and the like. The pixel electrode 190 is electrically connected to the source electrode 164 through the contact hole 176, whereby a potential is applied from the drain wiring 160 to the pixel electrode 190 through the switching element 138 and the source electrode 164. The pixel electrode 190 can be made of a transparent conductive material such as ITO or IZO.

  The liquid crystal display device 50 includes a light shielding film 212, a transmissive display color filter 214, a reflective display color filter 216, an overcoat layer 218, a topcoat layer 220, and a reflective display on the liquid crystal layer 300 side of the substrate 210. Common electrode 222 for use.

  In the illustration of FIG. 2, the light shielding film 212 is disposed on the substrate 210, and openings are provided in the transmission region 62 and the reflection region 64. The light shielding film 212 can be made of a black resin.

  The transmissive display color filter 214 is provided in the opening of the transmissive region 62 of the light shielding film 212, and the reflective display color filter 216 is provided in the opening of the reflective region 64 of the light shielding film 212. The display lights 92 and 94 are colored by the color filters 214 and 216, respectively. The color (hue) of the color filters 214 and 216 is selected according to the display color (hue) of the pixel 60. In the example of FIG. 2, the color filters 214 and 216 are disposed on the substrate 210. For example, the display lights 92 and 94 can be configured to be monochrome display by omitting the color filters 214 and 216.

  In the illustration of FIG. 2, the overcoat layer 218 is provided in both the transmission region 62 and the reflection region 64, and is disposed on the light shielding film 212 and the color filters 214 and 216. The topcoat layer 220 is provided in the reflective region 64 and is a layer thickness adjusting film (in other words, a cell gap adjusting film) that adjusts the layer thickness of the liquid crystal layer 300 in the reflective region 64, that is, the cell gap. For example, the thickness of the topcoat layer 220 is set so that the cell gap of the reflective region 64 is half that of the transmissive region 62. The top coat layer 220 is disposed on the overcoat layer 218 in the illustration of FIG.

  The reflective display common electrode 222 is provided in each reflective region 64, and is disposed on the topcoat layer 220 in the illustration of FIG. 2. The common electrode 222 may be provided for each reflective region 64 or may be provided across adjacent reflective regions 64. The common electrode 222 can be made of a transparent conductive material such as ITO or IZO. For example, the common electrode 222 is electrically connected to a wiring (not shown) of the element substrate 100 via conductive particles or the like in a region outside the display region, and thereby a potential is applied from the element substrate 100 side to the common electrode 222. Can be applied.

  The liquid crystal display device 50 includes an alignment film (not shown) on the liquid crystal layer 300 side of each of the substrates 110 and 210.

  The alignment film provided on the substrate 110 is disposed so as to cover the pixel electrodes 182, 190, the insulating layer 180, the common electrode 178, and the reflective layer 188, and the alignment film provided on the substrate 210 includes the common electrode 222 and the topcoat layer. 220 and the overcoat layer 218 are disposed. Both alignment films are provided in both the transmission region 62 and the reflection region 64. Here, the alignment film of the substrate 110 is rubbed in the same direction in both the regions 62, 64, and the rubbing direction R is substantially parallel to the row direction, specifically about 5 ° to 10 ° with respect to the longitudinal direction of the slit 184. The angle is set at an angle (see FIG. 3). Further, the alignment film of the substrate 210 is rubbed in the opposite direction to the rubbing direction R of the substrate 110 in both regions 62 and 64. In this case, the liquid crystal molecules (here, the dielectric anisotropy is positive) are arranged along the rubbing direction R in the vicinity of the alignment films in both the regions 62 and 64 and the same in the thickness direction of the liquid crystal layer 300. Arrange in the direction. The rubbing direction R of the substrate 110 and the substrate 210 may be rubbed in the same direction.

  In the transmissive region 62 configured by the FFS method, the rotation of liquid crystal molecules is controlled in a plane substantially parallel to the substrate 110 by controlling the electric field between the electrodes 178 and 182 formed through the slits 184. . On the other hand, in the reflective region 64 configured by the ECB method, liquid crystal molecules are aligned in a plane substantially perpendicular to the substrates 110 and 210 by an electric field between the reflective display common electrode 222 and the reflective display pixel electrode 190. The rotation is controlled. The light quantity of the transmissive display light 92 and the reflective display light 94 is controlled by such alignment control of liquid crystal molecules and the action of the polarizing layers 106 and 206 and the retardation layers 108 and 208 described below.

  In the liquid crystal display device 50, the retardation layer 108 and the polarizing layer 106 are laminated in this order on the substrate 110 on the side opposite to the liquid crystal layer 300 (that is, outside the substrate), and on the substrate 210 on the opposite side of the liquid crystal layer 300. The phase difference layer 208 and the polarizing layer 206 are laminated in this order. The retardation layers 108 and 208 and the polarizing layers 106 and 206 are provided in both the transmission region 62 and the reflection region 64.

  Due to various settings described later of the polarizing layers 106 and 206 and the retardation layers 108 and 208, the FFS transmission region 62 is normally black, that is, the display having the lowest transmittance when the voltage between the electrodes 178 and 182 is an off voltage. The ECB reflection region 64 is normally white, that is, a display having the highest transmittance when the voltage between the electrodes 190 and 222 is an off voltage (referred to as a bright display). ). The polarizing layers 106 and 206 and the retardation layers 108 and 208 will be further described later.

  As described above, the FFS transmission region 62 is normally black, and the ECB reflection region 64 is normally white. Therefore, when the entire pixel 60 is darkly displayed, an off voltage is applied between the transmissive display pixel electrode 182 and the transmissive display common electrode 178, and the reflective display pixel electrode 190 and the reflective display common electrode are applied. An ON voltage is applied between the first and second electrodes. Conversely, when the entire pixel 60 is to be brightly displayed, an on-voltage is applied between the transmissive display electrodes 182 and 178 and an off-voltage is applied between the reflective display electrodes 190 and 222. In the case of the above configuration example of the liquid crystal display device 50, the potential of the opposite phase between the transmissive display common electrode 178 and the reflective display common electrode 222, that is, the pixel electrodes 182 and 190 of both the dark display and the bright display. Potentials having opposite polarities with respect to the potential are applied. The halftone display between the bright display and the dark display is similarly driven. Thereby, the transmittance | permeability of both area | regions 62 and 64 is set appropriately, and favorable display quality is obtained.

  In the liquid crystal display device 50, the transmissive region 62 is configured by the FFS method which can obtain a high contrast at a wide viewing angle in the transmissive display, and the reflective region 64 is configured by an ECB method which can obtain a high contrast in the reflective display. For this reason, according to the liquid crystal display device 50, compared with the case where both the regions 62 and 64 are configured by the FFS method, for example, both the regions 62 and 64 have good contrast and the like, and good display quality is obtained.

  FIG. 4 shows a schematic cross-sectional view of the entire liquid crystal display device 50. As shown in FIG. 4, the retardation layers 108 and 208 and the polarizing layers 106 and 206 extend over the entire substrates 110 and 210. In FIG. 4, in order to make the drawing easy to understand, the retardation layers 108 and 208 and the polarizing layers 106 and 206 are separated from each other and from the substrates 110 and 210, and various elements provided on the substrates 110 and 210 are illustrated. Is not shown.

  In the illustration of FIG. 4, the retardation layer 108 is configured by stacking three retardation layers 108a, 108b, and 108c, and the retardation layer 208 is configured by stacking two retardation layers 208a and 208b. Each of the retardation layers 108a, 108b, 108c, 208a, 208b can be constituted by, for example, a film-like retardation plate, and the retardation layers 108, 208 can be formed by bonding them with an adhesive or the like.

  In order to make the explanation easier to understand, the first retardation layers 108a and 208a, the second retardation layers 108b and 208b, and the third retardation are provided from the side closer to the substrates 110 and 210 as necessary. This will be referred to as layer 108c.

  FIG. 5 is a diagram summarizing an example of characteristics of the retardation layers 108a, 108b, 108c, 208a, 208b and the polarizing layers 106, 206. Each direction of the absorption axis of the polarizing plate and the slow axis of the retardation layer is described with reference to the rubbing direction R (see FIG. 3).

  First, the polarizing layers 106 and 206 will be described. The absorption axis of the polarizing layer 106 is set substantially parallel to the rubbing direction R, and the absorption axes of the polarizing layers 106 and 206 are substantially orthogonal to each other. In the example of FIG. 5, the absorption axis of the polarizing layer 106 is set to a direction inclined about 7 ° with respect to the rubbing direction R, and the absorption axis of the polarizing layer 206 is set to a direction inclined about 97 ° with respect to the rubbing direction R. Has been. These are set so that contrast, brightness, and hue are optimal in reflective display.

  Next, the retardation layer 208 will be described. The first retardation layer 208a has a slow axis set in a direction substantially parallel to the rubbing direction R (about 0 ° in the illustration of FIG. 5), a retardation amount Δnd of about 100 nm, and a quarter wavelength. It corresponds to a board. The second retardation layer 208b is set so that the slow axis is inclined by about 116 ° with respect to the rubbing direction R, the phase difference Δnd is about 270 nm, and corresponds to a half-wave plate. At this time, the retardation layer 208 having a two-layer structure corresponds to a quarter-wave plate.

  The retardation layer 208 can also be composed of a single quarter-wave plate. However, in general, since the optical characteristics of the retardation plate have wavelength dependency, it is difficult to obtain a 1/4 wavelength retardation amount in the entire wavelength region with a single-layer retardation plate. On the other hand, by laminating a plurality of retardation layers 208a and 208b like the retardation layer 208, the above-described wavelength dependency is improved, and a phase difference amount of ¼ wavelength can be obtained in a wider band. it can.

  Of the retardation layer 108, the second and third retardation layers 108 b and 108 c are provided corresponding to the retardation layers 208 a and 208 b of the substrate 210. That is, the slow axis of the second retardation layer 108b is set in a direction substantially orthogonal to the slow axis of the retardation layer 208a, and the retardation amount Δnd of both retardation layers 108b and 208a is set to be approximately equal. ing. Similarly, the retardation layers 108c and 208b have slow axes that are substantially orthogonal to each other and have the same phase difference amount Δnd.

  The retardation layers 108b and 108c correspond to a half-wave plate and a quarter-wave plate, respectively, and the laminated structure including the retardation layers 108b and 108c corresponds to a quarter-wave plate. In the laminated structure, the slow axis is substantially orthogonal to the slow axis of the retardation layer 208, and the retardation amount Δnd is substantially equal to the retardation amount Δnd of the retardation layer 208. Although the retardation layers 108b and 108c can be formed of a single quarter-wave plate, the configuration of the plurality of retardation layers 108b and 108c is similar to the above description of the retardation layer 208. Is more preferable.

  Among the retardation layers 108, the first retardation layer 108 a is provided corresponding to the transmission region 62 of the liquid crystal layer 300. That is, the slow axis of the phase difference layer 108a is set in a direction substantially orthogonal to the rubbing direction R, and the phase difference amount Δnd of the phase difference layer 108a is a phase difference generated in the liquid crystal layer 300 in the transmission region 62 when an off voltage is applied. It is set to be approximately equal to the amount Δnd (about 350 nm in the example of FIG. 5). In the liquid crystal layer 300, the phase difference amount Δnd of the reflective region 64 is approximately ½ of the phase difference amount Δnd of the transmissive region 62 (about 165 nm in the illustration of FIG. 5).

The Nz coefficient of the first retardation layer 108a is 0 (zero), which compensates for the viewing angle dependency of the liquid crystal layer 300 and improves the display quality. Incidentally, Nz coefficient of the principal refractive index of the liquid crystal molecules as _{n x, n y, n z} , Nz = calculated by _{{(n x -n z) /} (n x -n y)}, n x = n z In this case, Nz = 0.

  According to the above configuration, in the transmission region 62, the backlight light incident from the polarizing layer 106 side passes through the retardation layers 108c, 108b, 208a, and 208b, but these retardation layers 108c, 108b, 208a, and 208b. With the above characteristic setting, the phase difference generated in the phase difference layer 108c is compensated (or canceled) by the phase difference layer 208b, and the phase difference in the phase difference layer 108b is compensated by the phase difference layer 208a.

  That is, the transmission region 62 is substantially equivalent to a configuration that does not include the retardation layers 108c, 108b, 208a, and 208b.

  The retardation layers 108a, 108b, and 108c are provided in both the transmission region 62 and the reflection region 64, but the reflected display light 94 does not pass through the retardation layers 108a, 108b, and 108c. That is, only the retardation layers 208a and 208b are effective in the reflective region 64.

  Therefore, for the four retardation layers 108c, 108b, 208a, and 208b, the slow axis, the retardation amount Δnd, and the like are substantially set to the desired characteristics of the reflection region 64 only for the retardation layers 208a and 208b. It may be set accordingly. Therefore, the design and formation of the retardation layers 108 and 208 are easy.

  Here, in the transmissive region 62, the backlight light passes through the retardation layer 108a and the liquid crystal layer 300. However, the backlight layer passes through the liquid crystal layer 300 before the liquid crystal layer 300 passes through the liquid crystal layer when an off voltage is applied. A phase difference that can compensate for the phase difference that occurs at 300 is provided. For this reason, since the linearly polarized light that has passed through the polarizing layer 106 does not generate a polarization component orthogonal to the linearly polarized light even after passing through the liquid crystal layer 300, almost all of the linearly polarized light is absorbed by the polarizing layer 206. Therefore, good dark display (black display) can be obtained in the transmissive region 62.

  Further, since the retardation layer 108a is effective only for the transmission region 62 as described above, the slow axis, the phase difference amount Δnd, the Nz coefficient, etc. of the retardation layer 108a have the desired characteristics of the transmission region 62. It may be set accordingly. Therefore, the design and formation of the retardation layers 108 and 208 are easy.

  FIG. 6 shows a schematic cross-sectional view of another entire liquid crystal display device 50B according to the embodiment. The liquid crystal display device 50B has the same configuration as the liquid crystal display device 50 (see FIG. 4) except for the configuration of the retardation layer. In the illustration of FIG. 6, the retardation layer 108 of the liquid crystal display device 50B is configured by laminating two retardation layers 108d and 108c.

  FIG. 7 shows a diagram summarizing an example of characteristics of the retardation layers 108d, 108c, 208a, 208b and the polarizing layers 106, 206 in the liquid crystal display device 50B. Referring to FIG. 5 above, the retardation layers 108a and 108b have the same slow axis direction. In view of this point, in the liquid crystal display device 50B, the two retardation layers 108a and 108b are formed by one retardation layer 108d. At this time, the phase difference amount Δnd of the phase difference layer 108d is set substantially equal to the sum of the phase difference amounts Δnd of the phase difference layers 108a and 108b. Further, the Nz coefficient of the retardation layer 108d is set to 0 (zero) as in the retardation layer 108a.

  Here, the characteristics of the retardation layer (first retardation layer) 108d are the same as the liquid crystal of the retardation layer (second retardation layer) 208a corresponding to the retardation layer 108b and the transmission region 62 corresponding to the retardation layer 108a. The description with respect to the layer 300 is as follows. That is, the slow axis of the retardation layer 108d is substantially orthogonal to the slow axis of the retardation layer 208a and the rubbing direction R. The retardation amount Δnd of the retardation layer 108 d is substantially equal to the sum of the retardation amount Δnd of the retardation layer 208 a and the retardation amount Δnd of the transmission region 62 of the liquid crystal layer 300. As described above, the slow axis of the retardation layer 208a is substantially parallel to the rubbing direction R.

  According to the liquid crystal display device 50B, both retardations due to the retardation layer 208a and the liquid crystal layer 300 can be compensated by the single retardation layer 108d. For this reason, as compared with the liquid crystal display device 50 described above, the structure is simplified and the formation is facilitated.

  According to the liquid crystal devices 50 and 50B, the retardation layers 108a, 108b, 108c, 108d, 208a, and 208b are provided outside the substrate. These retardation layers 108a, 108b, 108c, 108d, 208a, and 208b are provided in both the transmissive region 62 and the reflective region 64 without being patterned, and extend over the entire substrates 110 and 210. Therefore, the retardation layers 108a, 108b, 108c, 108d, 208a, 208b are easy to form. This also applies to the polarizing layers 106 and 206.

  Note that the number of stacked layers of the retardation layers 108 and 208 is not limited to the above example. In addition, the polarizing layers 106 and 206 can be configured by a laminated structure of a plurality of layers.

  In the above description, the pixel electrode 182 is disposed on the liquid crystal layer 300 side in the transmissive region 62, but the common electrode 178 may be disposed on the liquid crystal layer 300 side. In addition, the transmissive region 62 can be configured by the IPS system, and in this case, a good contrast can be obtained as in the FFS system. In the case of the IPS method, the common electrode 178 and the pixel electrode 182 are disposed on the same layer, for example, the insulating layer 170. Further, instead of the ECB method, another method in which the pixel electrode 190 and the common electrode 222 face each other through the liquid crystal layer 300 may be applied to the reflective region 64.

  In the above, the configuration in which the switching elements 132 and 138 are connected to the same gate wiring 140 is illustrated. However, it is also possible to provide the gate wiring 140 for each of the switching elements 132 and 138, that is, for transmissive display and reflective display, respectively. It is. In this case, even if the switching elements 132 and 138 are connected to the same drain wiring 160 as described above, the pixel electrodes 182 and 190 are different by shifting the on-state timing of the switching elements 132 and 138. A potential can be applied. For this reason, the transmittances of both the regions 62 and 64 are set to the above by applying the opposite phase potentials to the pixel electrodes 182 and 190, that is, the potentials having the opposite polarities with respect to the potentials of the common electrodes 178 and 222. It can be set appropriately as well.

  Further, although the configuration in which the switching elements 132 and 138 are connected to the same drain wiring 160 is illustrated, the drain wiring 160 may be provided in each of the switching elements 132 and 138, that is, for transmissive display and reflective display, respectively. It is. Also in this case, since different potentials can be applied to the pixel electrodes 182 and 190, the transmittance of both the regions 62 and 64 can be appropriately set by applying a reverse-phase potential to the pixel electrodes 182 and 190. it can.

  Further, according to the liquid crystal display device 50 illustrated in FIG. 2, the configuration is simple as compared with the case where the gate wiring 140 and / or the drain wiring 160 are provided for transmissive display and reflective display, respectively.

  Although the case where the transmissive region 62 and the reflective region 64 are provided in the same pixel 60 has been described above, the pixel 60 may be configured by the transmissive region 62 and the reflective region 64, respectively. That is, the configuration of the transmissive region 62 may be applied to configure the transmissive pixel 60, and the configuration of the reflective region 64 may be applied to configure the reflective pixel 60. Such a liquid crystal display device also exhibits the above various effects.

It is a schematic diagram explaining the liquid crystal display device which concerns on embodiment. 1 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment. It is a top view explaining the liquid crystal display device which concerns on embodiment. 1 is a cross-sectional view illustrating a liquid crystal display device according to an embodiment. It is a figure explaining an example of the characteristic of the phase difference layer which concerns on embodiment, and a polarizing layer. It is sectional drawing explaining the other liquid crystal display device optical layer which concerns on embodiment. It is a figure explaining another example of the characteristic of the phase difference layer which concerns on embodiment, and a polarizing layer.

Explanation of symbols

  50, 50B liquid crystal display device, 62 transmission region, 64 reflection region, 106, 206 polarizing layer, 108, 108a to 108d, 208, 208a, 208b retardation layer, 110, 210 substrate, 178 common electrode for transmissive display, 182 transmission Display pixel electrode, 190 reflective display pixel electrode, 222 reflective display common electrode, 300 liquid crystal layer, R rubbing direction.

Claims (5)

A liquid crystal display device in which liquid crystal is sandwiched between a pair of substrates and has a transmission region and a reflection region,
One of the pair of substrates is
A transmissive display pixel electrode and a transmissive display common electrode provided in the transmissive region;
A reflective display pixel electrode provided in the reflective region;
With
The other substrate of the pair of substrates is
A common electrode for reflection display provided in the reflection region;
Each of the pair of substrates is
A liquid crystal display device comprising a polarizing layer and one or more retardation layers on the outside. The liquid crystal display device according to claim 1,
The one or more retardation layers of the one substrate include a retardation layer whose slow axis is substantially orthogonal to any one of the one or more retardation layers of the other substrate,
The liquid crystal display device according to claim 1, wherein the retardation layers having slow axes substantially orthogonal to each other have substantially the same amount of retardation. The liquid crystal display device according to claim 1 or 2,
The one or more retardation layers of the one substrate include a retardation layer having a slow axis substantially perpendicular to a rubbing direction that defines an alignment direction of the liquid crystal,
The liquid crystal display device, wherein the retardation layer having a slow axis substantially orthogonal to the rubbing direction and the liquid crystal layer in the transmission region have substantially the same amount of retardation. The liquid crystal display device according to claim 1,
The one or more retardation layers of the one substrate include a first retardation layer;
The one or more retardation layers of the other substrate include a second retardation layer having a slow axis substantially parallel to a rubbing direction defining an alignment direction of the liquid crystal;
The first retardation layer includes
The slow axis is substantially perpendicular to the slow axis of the second retardation layer and the rubbing direction,
A liquid crystal display device, wherein a retardation amount is substantially equal to a sum of a retardation amount of the second retardation layer and a retardation amount of the liquid crystal layer in the transmission region. The liquid crystal display device according to any one of claims 1 to 4,
The polarizing layer of the one substrate and the polarizing layer of the other substrate are provided with absorption axes substantially orthogonal to each other.

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