JP2005241804A - Liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wide viewing angle, high luminance and high contrast transflective liquid crystal display device. <P>SOLUTION: The transflective liquid crystal display device is equipped with a light source side polarizing plate 170 and an observer side polarizing plate 100, a liquid crystal layer 143 disposed between the light source side polarizing plate 170 and the observer side polarizing plate 100, a light source 180 disposed on the rear side of the light source side polarizing plate 170, a transflective layer 150 disposed between the light source side polarizing plate 170 and the liquid crystal layer 143, an optical retardation plate 120 disposed between the observer side polarizing plate 100 and the transflective layer 150 and phase modulating light reflected on the transflective layer 150 so as to be emitted from the observer side polarizing plate 100, and a variable optical retardation layer 110 disposed between the observer side polarizing plate 100 and the transflective layer 150 and phase modulating light transmitted by the transflective layer 150 and passed through the liquid crystal layer 143 and the optical retardation plate 120 so as to be emitted from the observer side polarizing plate 100 in the transmissive display mode, and on the other hand, diffusing light reflected on the transflective layer 150 in the reflective display mode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a transflective liquid crystal display device.

  In recent years, with the spread of mobile phones and the like, the demand for transflective liquid crystal display devices with good color reproducibility and low power consumption is increasing.

  FIG. 7 is a cross-sectional view of a conventional transflective liquid crystal display device 2.

  The transflective liquid crystal display device 2 includes an observer side polarizing plate 200 and a light source side polarizing plate 280.

  A light source 290 is provided behind the light source side polarizing plate 280. The light source 290 is configured by, for example, a direct backlight, an edge light backlight, or the like, and uniformly displays the entire STN liquid crystal layer 240 when the transflective liquid crystal display device 2 displays an image in the transmissive display mode. It has a function of supplying light.

  An STN liquid crystal layer 240 for displaying an image is provided between the observer side polarizing plate 200 and the light source side polarizing plate 280.

  Between the observer side polarizing plate 200 and the STN liquid crystal layer 240, an observer side phase difference plate 220 and a substrate 230 are provided.

  The observer-side retardation plate 220 has a function of performing phase modulation so that light reflected by the semi-transmissive reflective layer 250 and passed through the STN liquid crystal layer 240 is emitted from the observer-side polarizing plate 200.

  A transflective layer 250 is provided between the STN liquid crystal layer 240 and the light source side polarizing plate 280. The transflective layer 250 is, for example, a metal total reflection layer made of aluminum, silver, or the like provided with a light transmission opening that penetrates the metal total reflection layer in the thickness direction, or a metal thin film such as aluminum or silver. It is formed by a half mirror or the like. Therefore, the semi-transmissive reflective layer 250 reflects the light incident from the observer side polarizing plate 200 and passing through the STN liquid crystal layer 240, while transmitting the light emitted from the light source 280 and transmitted through the light source side polarizing plate 270. It has a function.

  Between the semi-transmissive reflective film 250 and the light source side polarizing plate 280, a substrate 260 and a light source side retardation plate 270 are provided. The light source side retardation plate 270 is emitted from the observer side polarizing plate 200 and is emitted from the light source 290, transmitted through the semi-transmissive reflective layer 250, and transmitted through the STN liquid crystal layer 240 and the observer side retardation plate 220. So that the phase is modulated.

  When the transflective liquid crystal display device 2 displays an image in the reflective display mode, light incident from the observer side polarizing plate 200 is transmitted through the observer side retardation plate 220 and the STN liquid crystal layer 240. Then, the light is reflected by the transflective layer 250, passes through the STN liquid crystal layer 240 and the viewer-side retardation plate 220 again, and is emitted from the viewer-side polarizing plate 200.

  When the transflective liquid crystal display device 2 displays an image in the transmissive display mode, the light emitted from the light source 290 passes through the light source side retardation plate 270, the transflective layer 250, and the STN liquid crystal layer 240. After being transmitted, the light further passes through the observer-side retardation layer 220 and is emitted from the observer-side polarizing plate 200. That is, when the transflective liquid crystal display device 2 displays an image in the transmissive display mode, the light emitted from the light source 290 is emitted from the light source side retardation plate 270 and the observer side retardation layer 220. The light passes through the retardation plate and is emitted from the observer polarizing plate 200.

  Thus, since the optical path of light is different between the transmissive display mode and the reflective display mode (for example, light passes through the STN liquid crystal layer 240 only once in the transmissive display mode, whereas in the reflective display mode, the light is STN. The optical system design suitable for the transmissive display mode cannot obtain the optimum reflective display quality, and the optical system design suitable for the reflective display mode cannot achieve the optimum transmissive display quality. I can't get it. Therefore, the phase difference plates 220 and 270 are arranged in order to ensure appropriate display quality (brightness, contrast, etc.) in each display mode. Two phase difference plates may be laminated at the phase difference plates 220 and 270.

  Therefore, when the transflective liquid crystal display device 2 displays an image in the transmissive display mode, the light emitted from the light source 290 passes through many retardation plates and is emitted from the observer-side polarizing plate. The image display in the transmissive display mode of the transflective liquid crystal display device 2 has a problem that the luminance is low and the contrast is small.

  In view of such a problem, a transflective liquid crystal display device 3 having a multi-gap structure has been proposed (for example, Patent Document 1).

  FIG. 8 is a partial cross-sectional view of a transflective liquid crystal display device 3 having a conventional multi-gap structure.

  The transflective liquid crystal display device 3 includes a transmissive region 3 a that transmits light emitted from the light source 390 and a reflective region 3 b that reflects light incident from the observer-side polarizing plate 300.

  The transflective liquid crystal display device 3 includes an observer side polarizing plate 300 and a light source side polarizing plate 380.

  A light source 390 is provided behind the light source side polarizing plate 380. The light source 390 is constituted by, for example, a direct type backlight, an edge light type backlight, or the like, and is uniform over the entire STN liquid crystal cell 340 when the transflective liquid crystal display device 3 displays an image in the transmissive display mode. It has a function of supplying light.

  A phase difference plate 320 and an STN liquid crystal cell 340 are provided between the observer side polarizing plate 300 and the light source side polarizing plate 380.

  The phase difference plate 320 is provided closer to the observer than the reflection plate 350, and the light reflected by the reflection plate 350 and passed through the STN liquid crystal layer 343 having the layer thickness h2 provided in the reflection region 3b is on the observer side. It has a function of phase modulation so as to be emitted from the polarizing plate 300.

  The STN liquid crystal cell 340 includes a substrate 330, a transparent electrode 341, an STN liquid crystal layer 343 interposed between the transparent electrode 341 and the transparent electrode 345, and an alignment provided so as to sandwich the STN liquid crystal layer 343. A film 342, an alignment film 344, an overcoat layer 346 provided on the light source 390 side of the transparent electrode 345, a color filter 347, an insulating layer 361 provided in the reflective region 3b, and a substrate 362 are included.

  The reflective plate 350 is provided in the reflective region 3b portion under the STN liquid crystal layer 343. Further, the reflecting plate 350 has a fine uneven shape formed on the surface on the viewer side, and has a function of diffusing and reflecting light. Therefore, the light incident from the viewer side polarizing plate 300 is transmitted through the STN liquid crystal layer 343 and diffusely reflected to the viewer side by the reflecting plate 350 provided in the reflective region 3b. Therefore, the light reflected by the reflector 350 and emitted from the observer-side polarizing plate 300 does not exhibit directivity, and the transflective liquid crystal display device 3 has a reflective display mode with a wide viewing angle and good visibility. It can be realized.

  The STN liquid crystal layer 343 has different layer thicknesses in the transparent region 3a and the reflective region 3b. The layer thickness h1 of the STN liquid crystal layer 343 in the transmissive region 3a is such that the light emitted from the light source 390 passes through the light source side polarizing plate 380, the STN liquid crystal cell 340 provided in the transmissive region 3a, and the retardation plate 320. Are set to be emitted from the observer-side polarizing plate 300.

  Therefore, when the transflective liquid crystal display device 3 displays an image in the transmissive display mode, the light emitted from the light source 390 is emitted from the light source side polarizing plate 380 and the STN having the layer thickness h1 provided in the transparent region 3a. The light passes through the STN liquid crystal cell 340 having the liquid crystal layer 343 and the phase difference plate 320 and is emitted from the observer side polarizing plate 300 to the observer side.

As described above, in the transflective liquid crystal display device 3, the transmissive region 3a of the STN liquid crystal layer 343 emitted from the light source 390 is emitted by the retardation layer 320 and the layer thickness h1 of the STN liquid crystal layer 343 in the transmissive region 3a. And the phase difference between the light reflected by the reflector 350 and transmitted through the reflective region 3b of the STN liquid crystal layer 343 are compensated. For this reason, it is described that the transflective liquid crystal display device 3 can be configured with a smaller number of retardation plates, so that a transmissive display mode with high luminance and high contrast can be realized.
Japanese Patent Laid-Open No. 11-242226

  However, since the transflective liquid crystal display device 3 compensates for the phase difference between the transmissive display mode and the reflective display mode by the STN liquid crystal layer 343 having the multi-gap structure, the layer thicknesses h1 and h2 are high. Dimensional accuracy is required.

  Further, in order to realize a wide viewing angle, it is necessary to form a fine concavo-convex shape on the surface of the reflector 350 on the viewer side and to give the reflector 350 a function of diffusing and reflecting light.

  Thus, the transflective liquid crystal display device 3 requires a complicated and precise structure. Therefore, the transflective liquid crystal display device 3 has a problem that it requires many steps for manufacturing and is difficult to manufacture.

  The present invention has been made in view of such points, and the object of the present invention is to provide a reflective display mode that can be easily manufactured, has a wide viewing angle, and has good visibility, and has high brightness and contrast. An object is to provide a transflective semi-reflective liquid crystal display device capable of displaying an image in a large transmissive display mode.

A transflective liquid crystal display device according to the present invention is a liquid crystal display device that displays an image by switching between a reflective display mode and a transmissive display mode,
A light source side polarizing plate and an observer side polarizing plate;
A liquid crystal layer provided between the light source side polarizing plate and the observer side polarizing plate;
A light source provided behind the light source side polarizing plate;
Provided between the light source side polarizing plate and the liquid crystal layer, and reflects light that has entered from the observer side polarizing plate and passed through the liquid crystal layer, while exiting from the light source and illuminating the light source side polarizing plate. A transflective layer that transmits the transmitted light; and
Phase modulation is provided between the observer-side polarizing plate and the transflective layer so that light reflected by the transflective layer and passed through the liquid crystal layer is emitted from the observer-side polarizing plate. A phase difference plate,
Provided between the observer-side polarizing plate and the transflective layer, and in the transmissive display mode, the light transmitted through the transflective layer and transmitted through the liquid crystal layer and the retardation plate is observed. A variable phase difference layer that diffuses light reflected by the transflective layer in the reflective display mode while phase-modulating the light so as to be emitted from the user-side polarizing plate;
It is characterized by having.

  The transflective liquid crystal display device according to the present invention transmits the transflective layer between the observer-side polarizing plate and the transflective layer in the transmissive display mode, and transmits the liquid crystal layer and the retardation plate. A variable phase difference layer is provided that diffuses the light reflected by the transflective layer in the reflective display mode, while phase-modulating the light that has passed through the observer-side polarizing plate.

  Therefore, when an image is displayed in the transmissive display mode in the transflective liquid crystal display device according to the present invention, the light emitted from the light source is emitted from the light source side polarizing plate, the transflective layer, the liquid crystal layer, and the position. After passing through the phase difference plate, the light enters the variable phase difference layer. The light incident on the variable phase difference layer is phase-modulated by the variable phase difference layer so as to be emitted from the observer side polarizing plate, and is emitted from the observer side polarizing plate. Therefore, the number of retardation plates can be minimized by the phase modulation function of the variable retardation layer. Accordingly, it is possible to realize a transflective liquid crystal display device capable of transmissive display with high brightness and high contrast.

  In the case of displaying an image in the reflective display mode in the transflective liquid crystal display device according to the present invention, the light incident from the observer side polarizing plate is diffused by the variable retardation layer, And transmitted through the liquid crystal layer and reflected by the transflective layer. The light reflected by the transflective layer is transmitted through the liquid crystal layer and the phase difference plate, is further diffused by the variable phase difference layer, and is emitted from the observer-side polarizing plate. Therefore, it is possible to realize a transflective liquid crystal display device capable of performing reflective display with a wide viewing angle and good visibility without directivity of light emitted from the observer-side polarizing plate.

  As described above, a transflective liquid crystal display device according to the present invention provides a high-brightness, high-contrast transmissive display and a reflective display with a wide viewing angle and good visibility, as well as an observation with a transflective layer. This is realized by a variable retardation layer provided between the user-side polarizing plate.

  Therefore, in the transflective liquid crystal display device according to the present invention, it is not necessary to form an uneven shape on the surface on the viewer side of the transflective film, and it is also necessary to form a liquid crystal cell having a multi-gap structure. Absent.

  Therefore, the transflective liquid crystal display device according to the present invention has few manufacturing steps and is easy to manufacture.

  In the present invention, the variable retardation layer may be composed of a polymer dispersed liquid crystal layer.

  According to this configuration, switching between the transmissive display mode and the reflective display mode can be easily performed by controlling the voltage applied to the polymer-dispersed liquid crystal layer. Therefore, it is possible to realize a transflective liquid crystal display device that does not require a complicated mechanism for controlling the variable retardation layer, is easy to manufacture, and has good operability.

  In the present invention, when the polymer dispersion type liquid crystal layer which is a variable retardation layer is in a transmissive display mode, the light transmitted through the semi-transmissive reflection layer and passed through the liquid crystal layer and the retardation plate is While modulating the phase so as to be emitted from the observer-side polarizing plate, a predetermined voltage is applied to the variable retardation layer so as to diffuse the light reflected by the transflective layer in the reflective display mode. It is preferable to have a drive circuit for controlling the alignment direction of the liquid crystal molecules contained in the variable retardation layer.

  According to this configuration, the drive circuit for controlling the alignment direction of the liquid crystal molecules included in the variable retardation layer is provided independently of the circuit used for driving the display liquid crystal.

  Therefore, regardless of the display state of the display liquid crystal, the polymer-dispersed liquid crystal layer can be arbitrarily controlled independently of driving the display liquid crystal.

  Moreover, in this invention, you may be comprised so that the orientation direction of the liquid crystal molecule contained in the polymer dispersion-type liquid crystal layer which is a variable phase difference layer can be controlled continuously.

  According to this configuration, the degree of light diffusion in the polymer dispersed liquid crystal layer can be continuously adjusted by continuously controlling the alignment direction of the liquid crystal molecules contained in the polymer dispersed liquid crystal layer.

  As the alignment direction of the liquid crystal molecules contained in the polymer-dispersed liquid crystal layer becomes disordered, the degree of diffusion of light reflected from the transflective layer and emitted from the observer-side polarizing plate increases. Therefore, the transflective liquid crystal display device has a wide viewing angle and a low front luminance. On the other hand, as the liquid crystal molecules contained in the polymer-dispersed liquid crystal layer are aligned, the degree of diffusion of light reflected by the transflective layer and emitted from the observer-side polarizing plate becomes weaker. Therefore, the viewing angle of the transflective liquid crystal display device is narrow and the front luminance is increased.

  Therefore, according to this configuration, it is possible to realize a transflective liquid crystal display device capable of arbitrarily adjusting the viewing angle and the front luminance.

  Further, according to this configuration, the phase difference of the polymer dispersed liquid crystal layer can be continuously adjusted by continuously controlling the alignment direction of the liquid crystal molecules contained in the polymer dispersed liquid crystal layer.

The polymer of the polymer dispersion type liquid crystal layer has anisotropy. That is, it has a birefringence.
When the liquid crystal molecules contained in the polymer dispersed liquid crystal layer are perfectly aligned in the electrode direction, the polymer dispersed liquid crystal layer has a phase difference.

  When the applied voltage is reduced from that state, a deviation angle is generated between the alignment direction of the liquid crystal molecules contained in the polymer-dispersed liquid crystal layer and the electrode direction.

  As the misalignment angle between the alignment direction of the liquid crystal molecules and the electrode direction increases, the difference in the refractive index generated between the liquid crystal molecules contained in the polymer dispersion type liquid crystal layer and the polymer increases. Increases the birefringence. Therefore, the retardation of the polymer dispersion type liquid crystal layer becomes small.

  Thus, the color tone of the display image of the transflective liquid crystal display device can be adjusted by adjusting the voltage applied to the polymer dispersed liquid crystal layer and adjusting the phase difference of the polymer dispersed liquid crystal layer.

  Therefore, according to this configuration, it is possible to realize a transflective liquid crystal display device capable of arbitrarily adjusting the color tone.

  As described above, according to the present invention, when the image is displayed in the reflective display mode, the light reflected by the transflective film is diffused. On the other hand, when the image is displayed in the transmissive display mode, the light emitted from the light source is diffused. Since it has a variable phase difference layer having a function of adjusting the phase so that the light is emitted from the observer side polarizing plate, it is easy to manufacture, has a wide viewing angle and good visibility, and has a high luminance, Images can be displayed in a transmissive display mode with a high contrast.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a cross-sectional view of a transflective liquid crystal display device 1 according to an embodiment of the present invention.

  FIG. 2 is a cross-sectional view showing an optical path of light incident from the observer-side polarizing plate 100 when the transflective liquid crystal display device 1 displays an image in the reflective display mode.

  FIG. 3 is a cross-sectional view showing an optical path of light emitted from the light source 180 when the transflective liquid crystal display device 1 displays an image in the transmissive display mode.

  The transflective liquid crystal display device 1 includes an observer side polarizing plate 100 and a light source side polarizing plate 170. The observer side polarizing plate 100 and the light source side polarizing plate 170 have a function of transmitting only a specific polarization component with respect to incident light.

  An STN liquid crystal layer 140 for displaying an image is provided between the observer side polarizing plate 100 and the light source side polarizing plate 170. The STN liquid crystal cell 140 includes a substrate 130, a transparent electrode 141, an alignment film 142, an STN liquid crystal layer 143, an alignment film 144, a transparent electrode 145, an overcoat layer 146, a color filter 147, and a transflective layer 150. , And a substrate 160.

  The transparent electrode 141 and the transparent electrode 145 are provided so as to sandwich the STN liquid crystal layer 143 sandwiched between the alignment film 142 and the alignment film 144. The transparent electrode 141 and the transparent electrode 145 are made of, for example, indium tin oxide (hereinafter sometimes abbreviated as “ITO”) in which 1 to 5 weight percent of tin oxide is added to indium oxide, and the STN liquid crystal. The layer 143 has a function of applying a voltage.

  The alignment film 142 and the alignment film 144 are provided so as to sandwich the STN liquid crystal layer 143. The alignment film 142 and the alignment film 144 are made of, for example, a thin film such as polyimide that is rubbed by rubbing in a certain direction with a cloth or the like, and has a function of aligning rod-like liquid crystal molecules in the rubbing direction.

  In the STN liquid crystal cell 140, the alignment film 142 and the alignment film 144 are configured to have a rubbing direction twisted by about 180 to 270 °. Accordingly, the liquid crystal molecules dispersed in the STN liquid crystal layer 143 have a twist structure of about 180 to 270 °.

The overcoat layer 146 is made of, for example, an acrylic resin, and has an effect of flattening the unevenness present on the surface of the color filter 147 and making the rising of the liquid crystal display uniform.
The transflective layer 150 is, for example, a metal total reflection layer made of aluminum, silver, or the like provided with a light transmission opening that penetrates the metal total reflection layer in the thickness direction, or a metal thin film such as aluminum or silver It is formed by a half mirror or the like.

  Therefore, the semi-transmissive reflective layer 150 reflects the light incident from the observer side polarizing plate 100 and passing through the STN liquid crystal layer 143, while transmitting the light emitted from the light source 180 and transmitted through the light source side polarizing plate 170. .

  Therefore, by using the transflective layer 150, it is possible to realize the transflective liquid crystal display device 1 that can display an image by switching between the transmissive display mode and the reflective display mode.

  A light source 180 is provided behind the light source side polarizing plate 170. The light source 180 is constituted by, for example, a direct type backlight, an edge light type backlight, or the like, and is uniform over the entire STN liquid crystal cell 140 when the transflective liquid crystal display device 1 displays an image in the transmissive display mode. It has a function of supplying light.

  Between the observer-side polarizing plate 100 and the STN liquid crystal cell 140, a polymer dispersion type liquid crystal cell 110 that is a variable retardation layer and a retardation plate 120 are provided.

  The phase difference plate 120 has a function of performing phase modulation so that the light reflected by the transflective layer 150 and transmitted through the STN liquid crystal layer 143 is emitted from the observer-side polarizing plate 100.

  The polymer dispersion type liquid crystal cell 110 has a function as a variable retardation layer, and includes a substrate 111, a substrate 115, a polymer dispersion type liquid crystal layer 113 provided between the substrate 111 and the substrate 115, and a polymer dispersion type. A transparent electrode 112 and a transparent electrode 114 are provided so as to sandwich the liquid crystal layer 113.

  The substrate 111, the substrate 115, and the above-described substrate 130 and substrate 160 are made of a light-transmitting substrate such as a glass substrate or a resin substrate, for example. When a resin substrate is used, a thin and flexible transflective liquid crystal display device 1 can be realized.

  The polymer-dispersed liquid crystal layer 113 is a layer in which liquid crystal molecules 116 are dispersed in a uniaxial polymer 117.

  The liquid crystal molecules 116 are formed so as to have the same refractive index as that of the polymer 117 when aligned in the electrode direction, and to have a refractive index different from that of the polymer 117 when not aligned in the electrode direction.

  When no voltage is applied, since the liquid crystal molecules 116 are present in the polymer 117 in a random orientation, a difference in refractive index occurs between the polymer 117 and the liquid crystal molecules 116. Therefore, the light incident on the polymer dispersed liquid crystal layer 113 is diffused.

  On the other hand, in a state where a predetermined voltage is applied, the deviation angle between the alignment direction of the liquid crystal molecules 116 and the electrode direction is small, so that the difference between the refractive index of the polymer 117 and the refractive index of the liquid crystal molecules 116 is small. Therefore, the polymer-dispersed liquid crystal layer 113 does not have a diffusing function, and has a function of phase-modulating light transmitted through the polymer-dispersed liquid crystal layer 113.

  Accordingly, when the polymer dispersion type liquid crystal cell 110 is in the reflective display mode, as shown in FIG. 2, by applying no voltage to the polymer dispersion type liquid crystal cell 110, the light reflected by the transflective layer 150 is diffused. On the other hand, in the transmissive display mode, a predetermined voltage is applied to the polymer dispersion type liquid crystal cell 110 to transmit the STN liquid crystal cell 140 and the phase difference plate 120 as shown in FIG. The light has a function of phase-modulating so as to be emitted from the observer-side polarizing plate 100 without diffusing the emitted light.

  Therefore, by using the polymer-dispersed liquid crystal cell 110, an image can be displayed in a reflective display mode with a wide viewing angle and good visibility and a transmissive display mode with high brightness and high contrast. The display device 1 can be provided.

  As described above, the polymer-dispersed liquid crystal cell 110 can easily switch between the reflective display mode and the transmissive display mode of the transflective liquid crystal display device 1 by controlling the applied voltage. A complicated mechanism for switching between the mode and the transmissive display mode is not required.

  Further, since the light reflected by the semi-transmissive reflective layer 150 is diffused by the polymer dispersion type liquid crystal cell 110, it is not necessary to form an uneven shape on the surface of the semi-transmissive reflective layer 150 on the viewer side.

  Further, since the phase difference between the reflective display mode and the transmissive display mode can be compensated by the polymer dispersion type liquid crystal cell 110, it is not necessary to form a liquid crystal cell having a multi-gap structure which is difficult to manufacture.

  Accordingly, by using the polymer dispersion type liquid crystal cell 110 as the variable retardation layer, the transflective liquid crystal display device 1 that can be easily manufactured and can be easily switched between the reflective display mode and the transmissive display mode. Can be realized.

  The polymer dispersion type liquid crystal cell 110 is provided with a drive circuit 101 independent of the drive circuit 102 of the STN liquid crystal cell 140 which is a display liquid crystal.

  Therefore, the polymer dispersion type liquid crystal cell 110 can be controlled separately from the STN liquid crystal cell 140. Therefore, the transflective liquid crystal display device 1 that can arbitrarily switch between the reflective display mode and the transmissive display mode regardless of the display state of the STN liquid crystal cell 140 can be realized.

  The drive circuit 101 is configured to be able to continuously control the voltage applied to the polymer dispersion type liquid crystal cell 110, and the transflective liquid crystal display device 1 is a polymer dispersion type liquid crystal that is a variable retardation layer. The alignment direction of the liquid crystal molecules 116 contained in the cell 110 is configured to be continuously controllable.

  By continuously controlling the alignment direction of the liquid crystal molecules 116, it is possible to adjust the degree of light diffusion or phase difference by the polymer dispersed liquid crystal cell 110, and continuously adjust the viewing angle, front luminance, and color tone. Thus, a transflective liquid crystal display device 1 that can be realized can be realized.

  Hereinafter, the viewing angle and front luminance of the transflective liquid crystal display device 1 are controlled by continuously controlling the voltage applied to the polymer dispersed liquid crystal cell 110 and continuously controlling the orientation direction of the liquid crystal molecules 116. The principle that the color tone can be arbitrarily adjusted will be described.

  FIG. 4 is a cross-sectional view of the polymer dispersed liquid crystal cell 110 in a state where no voltage is applied to the drive circuit 101.

  FIG. 5 is a cross-sectional view of the polymer-dispersed liquid crystal cell 110 in a state where the voltage V1 is applied to the drive circuit 101. FIG.

  FIG. 6 is a cross-sectional view of the polymer dispersed liquid crystal cell 110 in a state where the voltage V0 is applied to the drive circuit 101. As shown in FIG.

  In a state where no voltage is applied to the polymer dispersion type liquid crystal cell 110, the liquid crystal molecules 116 in the polymer dispersion type liquid crystal layer 113 are randomly distributed as shown in FIG. For this reason, a difference in refractive index occurs between the liquid crystal molecules 116 and the polymer 117. Therefore, light incident on the polymer dispersion type liquid crystal cell 110 is diffused by the polymer dispersion type liquid crystal layer 113. Therefore, the transflective liquid crystal display device 1 when no voltage is applied has a wide viewing angle.

  When the voltage applied to the polymer dispersion type liquid crystal cell 110 is gradually increased, the difference between the alignment direction of the liquid crystal molecules 116 and the electrode direction is gradually reduced. For this reason, the refractive index difference between the liquid crystal molecules 116 and the polymer 117 is smaller than when no voltage is applied.

  Therefore, as the voltage applied to the polymer dispersion type liquid crystal cell 110 is gradually increased, the degree of diffusion of light incident on the polymer dispersion type liquid crystal cell 110 decreases. Accordingly, the viewing angle of the transflective liquid crystal display device 1 becomes smaller than when no voltage is applied, and the front luminance becomes larger than when no voltage is applied.

  For example, as shown in FIG. 5, the viewing angle θb when a voltage V1 (the voltage V1 is smaller than the voltage V0 sufficient for aligning the liquid crystal molecules 116) is applied to the polymer dispersion type liquid crystal cell 110 is As shown in FIG. 4, it is smaller than the viewing angle θa when no voltage is applied.

  Thus, by continuously controlling the voltage applied to the polymer dispersion type liquid crystal cell 110 and continuously controlling the alignment state of the liquid crystal molecules 116, the viewing angle and the front luminance can be arbitrarily controlled. A transmissive semi-reflective liquid crystal display device 1 can be realized.

  When the voltage applied to the polymer-dispersed liquid crystal cell 110 is increased to a voltage V2 near the voltage V0 sufficient for the alignment of the liquid crystal molecules 116 (the voltage V2 is smaller than the voltage V0), the alignment direction of the liquid crystal molecules 116 And the electrode direction are approximately similar. Therefore, the refractive index of the liquid crystal molecules 116 and the refractive index of the polymer 117 are approximately approximate values. Therefore, the polymer dispersed liquid crystal layer 113 does not scatter light incident on the polymer dispersed liquid crystal cell 110, while the polymer dispersed liquid crystal layer 113 has a birefringence. Therefore, the polymer dispersed liquid crystal cell 110 has a phase difference.

  When the applied voltage to the polymer dispersion type liquid crystal layer 110 is made closer to V0 from V2, the deviation angle between the alignment direction of the liquid crystal molecules 116 and the electrode direction is further reduced, so that the birefringence of the polymer dispersion type liquid crystal layer 113 is reduced. Will grow. Accordingly, the phase difference of the polymer dispersion type liquid crystal cell 110 is increased. On the other hand, when the voltage applied to the polymer dispersion type liquid crystal cell 110 is decreased from V2, the deviation angle between the alignment direction of the liquid crystal molecules and the electrode direction is increased. Since it becomes large, the birefringence of the polymer dispersion type liquid crystal layer 113 becomes small. Therefore, the phase difference of the polymer dispersion type liquid crystal cell 110 becomes small.

  Therefore, the phase difference of the polymer dispersion type liquid crystal cell 110 can be adjusted by finely adjusting the voltage applied to the polymer dispersion type liquid crystal cell 110 in the vicinity of the voltage V0 sufficient to align the liquid crystal molecules 116. Therefore, the transflective liquid crystal display device 1 capable of arbitrarily adjusting the color tone can be realized.

  Below, the manufacturing method of the transflective liquid crystal display device 1 is demonstrated.

  First, the transflective layer 150 is formed by forming a metal thin film made of, for example, aluminum or silver on a light-transmitting substrate 160 made of, for example, glass or resin by a film forming method such as sputtering. .

  Next, a color filter layer 147 is formed on the substrate 160 on which the transflective layer 150 is formed by, for example, an electrodeposition method or the like, and then an overcoat layer 146 made of, for example, an acrylic resin or the like is formed.

  Next, a transparent conductive film made of, for example, ITO (indium tin oxide) or the like is formed on the overcoat layer 146 by a film forming method such as a sputtering method, and pattern processing is performed by a photolithography technique or the like. An electrode 145 is formed.

  Next, an alignment film 144 is formed on the transparent electrode 145 by, for example, a roll coater method, and a rubbing process is performed.

  Next, for example, the transparent electrode 141 and the alignment film 142 are sequentially formed on the light-transmitting substrate 130 made of glass, resin, or the like, like the substrate 160, and then a rubbing process is performed.

  Next, the substrate 130 and the substrate 160 that constitute a transparent electrode or the like are bonded to face each other, and STN liquid crystal is vacuum injected between the alignment film 142 and the alignment film 144 to form the STN liquid crystal cell 140. .

  Next, a manufacturing method of the polymer dispersion type liquid crystal cell 110 will be described.

  First, for example, a transparent conductive film such as ITO (indium tin oxide) is formed on a substrate 111 made of glass or resin by a film forming method such as sputtering, and pattern processing is performed by a photolithography technique or the like. Thus, the transparent electrode 112 is formed.

  Next, the transparent electrode 114 made of ITO (indium tin oxide) or the like is formed on the substrate 115 made of glass or resin by the same method, for example.

  Next, the substrate 111 and the substrate 115 on which the transparent electrode is formed are bonded to face each other, and a polymer-dispersed liquid crystal solution composed of the ultraviolet curable polymer 117 and the liquid crystal molecules 116 is interposed between the transparent electrode 112 and the transparent electrode 114. Then, the polymer dispersed liquid crystal cell 110 having a uniaxial polymer is formed by irradiating ultraviolet rays (for example, polarized ultraviolet rays) to form the polymer dispersed liquid crystal layer 113.

  A laminate comprising the polymer dispersion type liquid crystal cell 110 and the STN liquid crystal cell 140 prepared as described above, an observer side polarizing plate 100, a light source side polarizing plate 170, a retardation plate 120, a light source 180, Are laminated in the order shown in FIG. 1 to produce a transflective liquid crystal display device 1.

  In the present embodiment, the variable retardation layer is configured by the polymer dispersion type liquid crystal cell 110. However, the variable retardation layer diffuses the light reflected by the transflective layer 150 in the reflective display mode. In the transmissive display mode, there is no limitation as long as the light can be emitted from the observer-side polarizing plate 100 by being transmitted through the semi-transmissive reflective layer 150 and phase-modulating light.

  In the present embodiment, the retardation plate 120 is provided between the polymer dispersion type liquid crystal cell 110 and the STN liquid crystal cell 140. However, the configuration is not limited to this configuration, and the retardation plate 120 is disposed on the viewer side. You may provide between the polarizing plate 100 and the polymer dispersion-type liquid crystal cell 110. FIG.

  In that case, the substrate 115 and the substrate 130 may be shared to form a single substrate. Thereby, the effect of parallax due to the substrate thickness can be suppressed, and a transflective liquid crystal display device capable of displaying a clearer image can be realized.

  In this embodiment, the polymer dispersion type liquid crystal cell 110 is provided between the observer-side polarizing plate 100 and the retardation plate 120. However, the present invention is not limited to this configuration. May be interposed anywhere between the transflective layer 150 and the observer-side polarizing plate 100, for example, of course, may be interposed between the substrate 130 and the transparent electrode 141.

  The present embodiment relates to the color transflective liquid crystal display device 1 having the STN liquid crystal cell 140 as a display liquid crystal layer. However, the present invention is not limited to this, and the present invention is not limited to a monochrome STN. The present invention can also be applied to a transflective liquid crystal display device having a liquid crystal layer, a transflective liquid crystal display device having an active matrix drive type liquid crystal layer using a switching element such as TFT or MIM, and the like. .

1 is a cross-sectional view of a transflective liquid crystal display device 1 according to an embodiment of the present invention. It is sectional drawing which shows the optical path of the light which injects from the observer side polarizing plate 100 in the case of displaying an image in the transflective liquid crystal display device 1 in the reflective display mode. It is sectional drawing which shows the optical path of the light radiate | emitted from the light source 180 in the case of displaying an image by the transflective liquid crystal display device 1 in a transmissive display mode. 2 is a cross-sectional view of a polymer dispersed liquid crystal cell 110 in a state where no voltage is applied to a drive circuit 101. FIG. 2 is a cross-sectional view of a polymer dispersed liquid crystal cell 110 in a state where a voltage V1 is applied to a drive circuit 101. FIG. 2 is a cross-sectional view of a polymer dispersed liquid crystal cell 110 in a state where a voltage V0 is applied to a drive circuit 101. FIG. It is sectional drawing of the conventional transflective liquid crystal display device 2. FIG. It is a fragmentary sectional view of the transflective liquid crystal display device 3 having a conventional multi-gap structure.

Explanation of symbols

1, 2, 3 transflective liquid crystal display device 3 a transmissive region 3 b reflective region 100, 200, 300 observer side polarizing plate 101, 102 drive circuit 110 polymer dispersed liquid crystal cell 111, 115, 130, 160, 230, 260, 330, 362 Substrate 112, 114, 141, 145, 341, 345 Transparent electrode 113 Polymer dispersed liquid crystal layer 116 Liquid crystal molecule 117 Polymer 120, 320 Phase difference plate 140, 340 STN liquid crystal cell 142, 144, 342, 344 Alignment Films 143, 240, 343 STN liquid crystal layer 146, 346 Overcoat layer 147, 347 Color filter layer 150, 250 Transflective layer 170, 280, 380 Light source side polarizing plate 180, 290, 390 Light source 220 Viewer side retardation plate 270 Light source side retardation plate 350 Plate 361 insulating layer

Claims (4)

A liquid crystal display device that displays an image by switching between a reflective display mode and a transmissive display mode,
A light source side polarizing plate and an observer side polarizing plate;
A liquid crystal layer provided between the light source side polarizing plate and the observer side polarizing plate;
A light source provided behind the light source side polarizing plate;
Provided between the light source side polarizing plate and the liquid crystal layer, and reflects light that has entered from the observer side polarizing plate and passed through the liquid crystal layer, while exiting from the light source and illuminating the light source side polarizing plate. A transflective layer that transmits the transmitted light; and
Provided between the observer-side polarizing plate and the semi-transmissive reflective layer, the light reflected by the semi-transmissive reflective layer and passed through the liquid crystal layer is phased so as to be emitted from the observer-side polarizing plate. A phase difference plate to modulate;
Provided between the observer-side polarizing plate and the transflective layer, and in the transmissive display mode, the light transmitted through the transflective layer and transmitted through the liquid crystal layer and the retardation plate is observed. A variable phase difference layer that diffuses light reflected by the transflective layer in the reflective display mode while phase-modulating the light so as to be emitted from the user-side polarizing plate;
A liquid crystal display device. The liquid crystal display device according to claim 1,
A liquid crystal display device, wherein the variable retardation layer is composed of a polymer-dispersed liquid crystal layer. The liquid crystal display device according to claim 2,
When the polymer-dispersed liquid crystal layer, which is the variable retardation layer, is in the transmissive display mode, the light transmitted through the transflective layer and the liquid crystal layer and the retardation plate is transmitted from the observer-side polarizing plate. In the reflective display mode, a predetermined voltage is applied to the variable retardation layer so as to diffuse the light reflected by the transflective layer in the reflective display mode, and the variable phase difference is applied. A liquid crystal display device having a drive circuit for controlling the alignment direction of liquid crystal molecules contained in a layer. The liquid crystal display device according to claim 2,
A liquid crystal display device configured to be capable of continuously controlling the alignment direction of liquid crystal molecules contained in the polymer-dispersed liquid crystal layer which is the variable retardation layer.

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