JP2004038204A - Liquid crystal display and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a transflective liquid crystal display whose visibility is improved by improving lightness of display in a transmission mode as a transflective liquid crystal display having a reflection mode and a transmission mode and electronic equipment equipped with the same. <P>SOLUTION: This liquid crystal display is a transflective liquid crystal display which has a liquid crystal 4 sandwiched between a top substrate 3 and a bottom substrate 2 facing each other and is provided with an upper polarizing plate 13 and a lower reflecting and polarizing layer 6 on the top side and reverse side of the liquid crystal 4 and provided with a back light (lighting device) 5 on the external surface side of the bottom substrate 2 to make display by switching the transmission mode and reflection mode; and the lower reflecting and polarizing layer 6 is a transflective polarizing layer which has a transmission axis and a reflection axis crossing the transmission axis at right angles to reflect a portion of a component of incident light parallel to the reflection axis and transmits a portion and a lower polarizing layer 20 is provided below the lower reflecting and polarizing layer 6. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to a liquid crystal display device and an electronic apparatus, and more particularly to a configuration of a transflective liquid crystal display device capable of displaying sufficient brightness even in a transmission mode.

Reflection type liquid crystal display devices have low power consumption because they do not have a light source such as a backlight, and have been widely used in various portable electronic devices and display units attached to devices.
However, since display is performed using external light such as natural light or illumination light, there is a problem that it is difficult to visually recognize the display in a dark place. Therefore, there has been proposed a liquid crystal display device in which external light is used in a bright place as in a normal reflective liquid crystal display device, but in a dark place, the display can be visually recognized by an internal light source. In other words, this liquid crystal display device employs a display method having both a reflective type and a transmissive type, and reduces power consumption by switching to a reflective mode or a transmissive mode according to the surrounding brightness. In addition, even when the surroundings are dark, clear display can be performed. Hereinafter, in this specification, this type of liquid crystal display device is referred to as a “semi-transmissive reflective liquid crystal display device”.

(4) As a form of the transflective liquid crystal display device, there has been proposed a liquid crystal display device having a reflective film in which a slit for transmitting light is formed in a metal film such as aluminum on the inner surface of a lower substrate. This is because by providing a metal film on the inner surface side of the lower substrate, the influence of parallax due to the thickness of the lower substrate is prevented, and particularly in a structure using a color filter, color mixing is prevented. FIG. 9 is a partial sectional view showing an example of a transflective liquid crystal display device of a passive matrix system. In this liquid crystal display device 100, a liquid crystal 103 is sandwiched between a pair of a transparent upper substrate 102 and a lower substrate 101, a reflective film 104 and an insulating film 106 are laminated on the lower substrate 101, and indium tin oxide is formed thereon. A striped scanning electrode 108 made of a transparent conductive film such as a material (Indium Tin Oxide, hereinafter abbreviated as ITO) is formed, and an alignment film 107 is formed so as to cover the scanning electrode 108. On the other hand, a color filter 109 is formed on the upper substrate 102, a flattening film 111 is laminated thereon, and a signal electrode 112 made of a transparent conductive film such as ITO is formed on the flattening film 111 with the scanning electrode 108. It is formed in a stripe shape in a direction perpendicular to the direction, and an alignment film 113 is formed so as to cover the signal electrode 112. The reflection film 104 is formed of a metal film such as aluminum, and a slit 110 for light transmission is formed in each pixel of the reflection film 104. The reflection film 104 functions as a semi-transmissive reflection film by transmitting light incident from the lower substrate 101 side through the slit 110. Further, a forward scattering plate 118, a retardation plate 119, and an upper polarizing plate 114 are arranged outside the upper substrate 102 in this order from the upper substrate 102 side, and a に は wavelength plate 115 and a lower polarizing plate 115 are disposed outside the lower substrate 101. 116 are provided. Further, a backlight 117 is arranged on the lower surface side of the lower substrate 101.

When the liquid crystal display device 100 having the above configuration is used in a reflective mode in a bright place, external light incident from above the upper substrate 102 passes through the liquid crystal 103 and is reflected on the surface of the reflective film 104, and then the liquid crystal 103 again. And is emitted to the upper substrate 102 side. When used in a transmissive mode in a dark place, light emitted from a backlight 117 installed below the lower substrate 101 passes through the reflective film 104 at the slit 110, then passes through the liquid crystal 103 and passes through the upper substrate. The light is emitted to the side 102. These lights contribute to the display in each mode.

According to the liquid crystal display device 100, although the display can be visually recognized regardless of the presence or absence of external light, there is a problem that the brightness in the transmission mode is less than that in the reflection mode. This is because the amount of light that can mainly contribute to display in the transmission mode is only the amount of light that has passed through the slit 110 provided in the reflection film 104, and the １ ／ wavelength plate provided on the outer surface side of the lower substrate 101 This is due to the loss of light due to 115 and the polarizing plate 116.

In the case of performing display in the transmission mode in the liquid crystal display device 100 shown in FIG. 9, light emitted from the backlight 117 enters the liquid crystal display unit from outside the lower substrate 101, and the slit 110 Is light that contributes to display. Here, in order to perform dark display in the liquid crystal display device 100, light traveling from the slit 110 to the upper substrate 102 needs to be circularly polarized light. Accordingly, since the light emitted from the backlight 117 and passing through the slit 110 needs to be circularly polarized light, the light transmitted through the lower polarizing plate 116 and converted into linearly polarized light is converted into circularly polarized light. A quarter-wave plate 115 is required.

Next, when attention is paid to light that does not pass through the slit 110 among the light emitted from the backlight 117, the light is emitted from the backlight 117, passes through the lower polarizing plate 116, and is converted into linearly polarized light parallel to the paper surface. The light passes through the 波長 wavelength plate 115 to become circularly polarized light, and reaches the reflection film 104. When this light is not incident on the slit 110 but is reflected on the surface on the lower substrate 101 side of the reflective film 104, the light becomes circularly polarized light in the opposite direction to the circularly polarized light incident on the reflective film 104, and this light is again １ ／ wavelength After passing through the plate 115, it is converted into linearly polarized light perpendicular to the plane of the paper. Therefore, this light is absorbed by the lower polarizing plate 116 having a transmission axis parallel to the paper surface. In other words, of the light emitted from the backlight 117, the light reflected on the back surface side of the reflection film 104 without passing through the slit 110 is almost entirely absorbed by the lower polarizing plate 116 of the lower substrate 101. .

Further, focusing on the case where bright display in the transmission mode is performed in the liquid crystal display device shown in FIG. 9, light incident on the liquid crystal 103 through the slit 110 is reflected on the upper substrate 102 without being affected by the liquid crystal 103. Although the light passes through the plate 114 and is emitted above the liquid crystal display device, the light traveling from the slit 110 to the upper substrate 102 is circularly polarized by the quarter-wave plate 115, and thus has a transmission axis parallel to the paper. About half of the light passes through the upper polarizing plate 114 and is absorbed by the upper polarizing plate 114.

For the above reasons, in the liquid crystal display device 100, the display in the transmission mode could not be brightened. In order to solve the above-described problem, a liquid crystal display device having a configuration shown in FIG. 10 has been proposed. In a liquid crystal display device 200 shown in FIG. 10, a liquid crystal 203 is sandwiched between a pair of a transparent lower substrate 201 and an upper substrate 202. On the lower substrate 201, a reflective polarizing layer 204 and an insulating layer 206 are stacked. A scanning electrode 208 formed of a transparent conductive film such as ITO is formed in a stripe shape, and an alignment film 207 is formed so as to cover the scanning electrode 208. On the other hand, a color filter 209 is formed on the inner surface side of the upper substrate 202, a flattening film 211 is laminated thereon, and a signal electrode 212 made of a transparent conductive film such as ITO is formed on the flattening film 211. It is formed in a stripe shape in a direction orthogonal to 208, and an alignment film 213 is formed so as to cover the signal electrode 212. The reflective polarizing layer 204 is formed by forming a fine opening having a width of about 50 nm in a slit shape at a pitch of 150 nm to 400 nm in a metal film such as aluminum. The light incident on the reflective polarizing layer 204 is such that polarized light parallel to the slit-shaped opening is reflected, and polarized light perpendicular to the opening is transmitted. Further, on the outer side of the upper substrate 202, a forward scattering plate 218, a phase difference plate 219, and an upper polarizing plate 214 are arranged in this order from the upper substrate 202 side. Further, a backlight 217 is arranged on the lower surface side of the lower substrate 201.

In the liquid crystal display device 200 having the above configuration, unlike the liquid crystal display device 100 shown in FIG. 9 in the transmission mode, the light incident on the upper polarizing plate 214 is not circularly polarized light but linearly polarized light. It is possible to make the display in the transmissive mode brighter than in the case of. The light reflected without passing through the reflective polarizing layer 204 is returned to the backlight 217, and while the light is repeatedly reflected between the reflective polarizing layer 204 and the backlight 217, its polarization state changes and the reflected polarized light changes. Since the light can pass through the layer 204, the light of the backlight 217 can be used more effectively than the liquid crystal display device 100.

However, when the liquid crystal display device 200 having the above configuration is used in the transmission mode, when external light is incident on the liquid crystal display device 200, the contrast of the liquid crystal display device 200 is significantly reduced. May not be visible. The present inventors have conducted a detailed study on this problem, and have completed the present invention. The details of this verification will be described later in detail (means for solving the problem).

Accordingly, an object of the present invention is to provide a transflective liquid crystal display device having a reflective mode and a transmissive mode, in which the display brightness in the transmissive mode is improved and the transflective liquid crystal display with excellent visibility is provided. It is to provide a device.
Another object of the present invention is to provide an electronic device provided with a transflective liquid crystal display device having excellent visibility as described above.

In order to achieve the above object, in the liquid crystal display device of the present invention, a liquid crystal is sandwiched between an upper substrate and a lower substrate facing each other, an upper polarizing layer above and below the liquid crystal, and a lower reflective polarizing layer. A transflective liquid crystal display device, comprising: a liquid crystal panel provided with an illuminating device provided on an outer surface side of the liquid crystal panel, and performing display by switching between a transmission mode and a reflection mode, wherein the lower reflective polarizing layer Is a transflective reflective polarizing layer that has a transmission axis and a reflection axis orthogonal to the transmission axis, reflects a part of a component of incident light parallel to the reflection axis, and transmits a part. A lower polarizing layer is provided below the lower reflective polarizing layer.

According to the configuration of the present invention, the brightness of the display in the transmission mode can be remarkably improved, and the problem of the liquid crystal display device 200 shown in FIG. 10 can also be solved. Even so, the contrast can be prevented from lowering. These effects will be described in detail below with reference to FIGS.

FIG. 3 is an explanatory view for explaining the operation principle of the liquid crystal display device of the present invention. FIG. 3 (a) shows a transmission mode light path, and FIG. 3 (b) shows a reflection mode light path. In these drawings, among the components of the liquid crystal display device of the present invention, only the components necessary for the description are shown. An upper polarizing plate 54 and a lower reflective polarizing layer 51 are provided above and below the liquid crystal 53. The lower substrate 50 is disposed outside the lower reflective polarizing layer 51, and the lower polarizing layer 55 is formed on the outer surface side of the lower substrate 50. An illumination device 58 is provided outside the lower polarizing layer 55 (the lower surface side in the figure), and a reflection plate 59 is provided on the outer surface side of the illumination device 58.

The upper polarizing plate 54 has a transmission axis in a direction perpendicular to the paper surface, and the lower polarizing layer 55 has a transmission axis parallel to the paper surface. The lower reflective polarizing layer 51 is a transflective reflective polarizing layer, and has a transmission axis in a direction perpendicular to the paper surface and a reflection axis orthogonal to the transmission axis. Then, almost all the light parallel to the transmission axis is transmitted, but a part of the light parallel to the reflection axis is reflected and a part is transmitted. That is, the lower reflective polarizing layer 51 is of a semi-transmissive reflective type for light parallel to its reflection axis.

Hereinafter, a case where display is performed in the transmission mode shown in FIG. 3A will be described.
In the liquid crystal display device of the present invention, transmission mode display is performed using light emitted from the illumination device 58. The light emitted from the illumination device 58 is converted into polarized light parallel to the paper surface by the lower polarizing layer 55 having a transmission axis parallel to the paper surface, and then passes through the lower substrate 50 and enters the lower reflective polarizing layer 51. The lower reflective polarizing layer 51 has a transmission axis perpendicular to the paper surface as described above, and a part of the light polarized in parallel to the paper surface by the lower polarizing layer 55 is reflected to the illumination device 58 side. The reflected light 61 is returned, and a part thereof is transmitted light 60 which is transmitted and enters the liquid crystal 53.

Next, when the transmitted light 60 incident on the liquid crystal 53 is in a state where a voltage is applied to the liquid crystal 53 (on state), the light incident on the liquid crystal 53 is hardly affected by the liquid crystal 53 and the upper polarizing plate 54 And the light is absorbed by the upper polarizing plate 54 having a transmission axis perpendicular to the plane of the paper, and the pixel is displayed in a dark state. On the other hand, when no voltage is applied to the liquid crystal 53 (off state), the transmitted light 60 incident on the liquid crystal 53 is converted into polarized light perpendicular to the paper by the optical rotation of the liquid crystal 53, and is transmitted to the upper polarizing plate 54. To reach. Then, this light, which is polarized light parallel to the transmission axis of the upper polarizing plate 54, passes through the upper polarizing plate 54 so that pixels are displayed brightly.

Here, focusing on the reflected light 60 reflected on the back surface side (the lower substrate 50 side) of the lower reflective polarizing layer 51, the reflected light 60 transmits through the lower substrate 50 and the lower polarizing layer 55 to the illumination device 58. Then, the light is reflected by the reflection plate 59 on the outer surface side of the illumination device 58 and is reused as light traveling toward the lower polarizing layer 55 again. Then, this light reaches the lower reflective polarizing layer 51 again, a part of the light is transmitted and enters the liquid crystal 53, and a part of the light is reflected and returned to the lighting device 58 side. The light reflected by the lower reflective polarizing layer 51 as described above is transmitted through the lower reflective polarizing layer 51 while being repeatedly reflected between the lower reflective polarizing layer 51 and the reflector 59, and is used as light contributing to display. . Therefore, in the liquid crystal display device of the present invention, of the light emitted from the illumination device 58, the light transmitted through the lower polarizing layer 55 can be used to the maximum, and a bright display can be obtained.

Next, a case where display is performed in the reflection mode shown in FIG. 3B will be described.
As shown in FIG. 3B, light incident from above the upper polarizing plate 54 is first converted into polarized light perpendicular to the paper surface by the upper polarizing plate 54 having a transmission axis perpendicular to the paper surface, and is incident on the liquid crystal 53. I do. Next, when the liquid crystal is in the ON state, the incident light reaches the lower reflective polarizing layer 51 with little effect from the liquid crystal 53. Since the lower reflective polarization layer 51 has a transmission axis perpendicular to the paper surface and a reflection axis parallel to the paper surface, light reaching the lower reflection polarization layer 51 is transmitted through the lower reflection polarization layer 51. Thereafter, the light passes through the lower substrate 50 and is absorbed by the lower polarizing layer 55 having a transmission axis parallel to the paper surface, and the pixels are darkly displayed.

On the other hand, when the liquid crystal 53 is in the off state, the light incident on the liquid crystal 53 is converted into polarized light parallel to the paper by the optical rotation of the liquid crystal 53, and reaches the lower reflective polarizing layer 51. Then, a part of the light is reflected by the lower reflective polarizing layer 51 having a reflection axis parallel to the paper surface to be reflected light 63, and a part thereof is transmitted to be transmitted light 62. The reflected light 63 is again converted into polarized light perpendicular to the paper surface by the optical rotation of the liquid crystal 53 and transmitted through the upper polarizing plate 54, so that the pixel is displayed brightly. The transmitted light 62 transmitted through the lower reflective polarizing layer 51 is transmitted through the lower substrate 50 and the lower polarizing layer 55 and emitted to the illumination device 58. Since the illumination device 58 is provided with the reflection plate 59, a part of the transmitted light 62 is reflected by the reflection plate 59 and returns to the lower substrate 50 side. The brightened pixel becomes brighter.

As described above, in the liquid crystal display device of the present invention, as in the liquid crystal display device 100 shown in FIG. 9, display can be performed without providing the quarter-wave plate 115 outside the lower substrate 101. Accordingly, since there is no conversion from linearly polarized light to circularly polarized light or from circularly polarized light to linearly polarized light, there is no light loss accompanying these conversions. As a result, a bright display can be obtained, and particularly the brightness in the transmission mode can be significantly improved.

Next, the operation of the conventional liquid crystal display device 200 shown in FIG. 10 will be described with reference to FIG.
FIG. 4 is an explanatory diagram for explaining the operation of the liquid crystal display device 200, and shows only components necessary for the description among the components shown in FIG. That is, only the liquid crystal 203, the upper polarizing plate 214 and the reflective polarizing layer 204 disposed above and below the liquid crystal 203, the lower substrate 201, and the backlight 217 disposed on the outer surface side of the lower substrate 201 are illustrated.

First, the transmission mode shown in FIG.
In the liquid crystal display device 200, light emitted from the backlight (illumination device) 217 passes through the lower substrate 201 and reaches the reflective polarizing layer 204. Since the reflective polarizing layer 204 has a transmission axis perpendicular to the plane of the paper and a reflective axis parallel to the plane of the paper, part of the light reaching the reflective polarizing layer 204 is converted into polarized light perpendicular to the plane of the paper, and Incident. When the liquid crystal 203 is in the ON state, the liquid crystal 203 reaches the upper polarizing plate 214 with little effect from the liquid crystal 203 and transmits through the upper polarizing plate 214 having a transmission axis perpendicular to the plane of the drawing. In this way, the pixels are brightly displayed. On the other hand, when the liquid crystal 203 is in the off state, the light incident on the liquid crystal 203 is converted into polarized light parallel to the paper by the optical rotation of the liquid crystal 203, reaches the upper polarizing plate 54, and has a transmission axis perpendicular to the paper. The light is absorbed by the polarizing plate 54. In this way, the pixels are darkly displayed.

Next, the reflection mode shown in FIG. 4B will be described.
As shown in FIG. 4B, light incident from above the upper polarizing plate 214 is converted into polarized light perpendicular to the paper surface by the upper polarizing plate 214 having a transmission axis perpendicular to the paper surface, and is incident on the liquid crystal 203. When the liquid crystal 203 is in the ON state, the incident light reaches the reflective polarizing plate 204 as it is, passes through the reflective polarizing plate 204 having a transmission axis perpendicular to the plane of the paper, and then passes through the substrate 201 to form a backlight. 217 is emitted. In this way, the pixels are darkly displayed. On the other hand, when the liquid crystal 203 is in the off state, the light incident on the liquid crystal 203 is converted into polarized light parallel to the paper by the optical rotation of the liquid crystal 203, and reaches the reflective polarizing plate 204. Here, since the reflection polarizing plate 204 has a reflection axis parallel to the paper surface, this light is reflected and enters the liquid crystal 203 again. Then, the light is converted into polarized light perpendicular to the paper surface by the optical rotation of the liquid crystal 203, and is transmitted through the upper polarizing plate 214. In this way, the pixels are brightly displayed.

In the liquid crystal display device 200, the problem that the contrast is greatly reduced when external light enters the liquid crystal display device 200 in the transmission mode is that the liquid crystal 203 corresponding to the bright display and the dark display is turned on in the transmission mode and the reflection mode. / Off states are different. That is, when the pixels are displayed in a dark state, the liquid crystal is off in the transmission mode, but is on in the reflection mode. For this reason, for example, when external light is incident on the liquid crystal display device 200 in a state where the liquid crystal display device 200 is used in the transmission mode, the external light incident on a pixel for dark display (a pixel to which no voltage is applied to the liquid crystal) is reflected. The light is reflected by the upper surface of the liquid crystal display 204, passes through the upper substrate 201, and is emitted above the liquid crystal display device 200. For this reason, pixels that should be displayed darkly become brightly displayed, and as a result, the contrast is reduced, and in some cases, the display cannot be visually recognized.

On the other hand, in the liquid crystal display device of the present invention, as shown in FIGS. 3A and 3B, the liquid crystal 53 is turned off in both the bright display in the transmission mode and the bright display in the reflection mode. On the contrary, in the dark display, the liquid crystal 53 is turned on in both modes. Therefore, when the device is used in the transmissive mode, even if external light is incident, the liquid crystal 53 is turned on in the dark display pixel, so that it is incident on the liquid crystal 53 as shown in FIG. The external light thus absorbed is absorbed by the lower polarizing layer 55 on the outer surface side of the lower substrate 50 and does not return to the upper polarizing plate 54 side. Therefore, the contrast does not decrease as in the liquid crystal display device 200 described above, and good visibility can be obtained.

Further, in the liquid crystal display device of the present invention, since the lower polarizing layer 55 is provided on the outer surface side of the lower substrate 50 as shown in FIG. 3, the contrast can be increased more than the liquid crystal display device 200 shown in FIG. Can be. This is because, in the liquid crystal display device 200 shown in FIG. 4B, external light passes through the upper polarizing plate 214, the liquid crystal 203, and the reflective polarizing layer 203, and then is emitted toward the backlight 217. On the other hand, in the liquid crystal display device of the present invention, the external light incident on the pixels for dark display passes through the upper polarizing plate 54, the liquid crystal 53, and the lower reflective polarizing layer 51, and is then absorbed by the lower polarizing layer 55. It is. That is, in the liquid crystal display device 200 shown in FIG. 4B, the light emitted to the backlight 217 side is reflected by a reflector (not shown) provided on the outer surface side of the backlight 217, and In some cases, the light may be directed toward the liquid crystal, and the dark display may become bright and the contrast may decrease. However, in the liquid crystal display device of the present invention, the light is absorbed by the lower polarizing plate 55 and returns to the liquid crystal 53 side again. Because there is no.

As described above, according to the liquid crystal display device of the present invention, the light emitted from the illumination device can be used more effectively as compared with the conventional transflective liquid crystal display device. Can be remarkably improved. Further, since the on / off state of the liquid crystal corresponding to the light and dark display is the same in the transmission mode and the reflection mode, even if external light enters in the transmission mode, the contrast does not decrease and a clear display is obtained. Can be Further, in the dark display in the reflection mode, by adopting a structure in which the light transmitted through the liquid crystal is absorbed by the lower polarizing layer, the dark display can be made darker, so that the contrast in the reflection mode can be improved.

Next, in the liquid crystal display device of the present invention, it is preferable that the transmittance of light parallel to the reflection axis of the lower reflective polarizing layer is 20% or more and 70% or less. More preferably, the transmittance of light parallel to the reflection axis is 30% or more and 50% or less.

By setting the reflectance of the lower reflective polarizing layer within the above range, a bright display can be obtained in both the transmission mode and the reflection mode, and a liquid crystal display device with excellent visibility can be obtained.
If the transmittance is less than 20%, the amount of light incident on the liquid crystal from the lighting device is too small, so that the display brightness in the transmission mode is insufficient. If it exceeds 70%, the lower reflective polarizing layer is in the reflection mode. And the amount of light used for display is insufficient. Further, by setting the transmittance in the range of 30% or more and 50% or less, the balance between the brightness in the transmission mode and the brightness in the reflection mode can be improved, and a liquid crystal display device with more excellent visibility can be obtained.

Next, in the liquid crystal display device of the present invention, it is preferable that the angle formed by the transmission axis of the lower reflective polarizing layer and the transmission axis of the lower polarizing layer is not less than 60 degrees and not more than 120 degrees.

In the reflection mode shown in FIG. 3B, when dark display is performed, external light incident on the liquid crystal display device is finally absorbed by the lower polarizing layer 55. Of the light transmitted through the layer 51, a component parallel to the transmission axis of the lower polarizing layer 55 passes through the lower polarizing layer 55 and is emitted to the illumination device 58 side. When this light is reflected by the reflection plate 59 and returns to the liquid crystal 53 side, the dark display becomes bright and the contrast decreases. Therefore, it is most desirable that the angle formed by the transmission axis of the lower polarizing layer 55 and the transmission axis of the lower reflective polarizing layer 51 be 90 ° (both are orthogonal). If the angle formed is within ± 30 °, it can be used practically. When the angle formed by both transmission axes exceeds the above range, the amount of light transmitted through the lower polarizing layer 55 increases, and the contrast of the liquid crystal display device decreases.

Next, the liquid crystal display device of the present invention may have a configuration in which a reflective polarizing plate is provided on the outer surface side of the lower polarizing layer. With such a configuration, light emitted from the lighting device can be more efficiently used for display, and display in the transmission mode can be made brighter. This configuration will be described in detail below with reference to FIG.

FIG. 5 is an explanatory view showing a main part of the liquid crystal display device according to the present invention employing the above configuration. The liquid crystal display device shown in this figure differs from the liquid crystal display device shown in FIG. 3 only in that a reflective polarizer is provided on the outer surface side of the lower substrate. Therefore, only the operation of the reflective polarizing plate 57 shown in FIG. 5 will be described in detail below. Also, among the components shown in FIG. 5, the same components as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof will be omitted.

反射 The reflective polarizing plate 57 shown in FIG. 5 is a reflective polarizing plate having a transmission axis parallel to the paper and a reflection axis perpendicular to the paper. The display principle of this liquid crystal display device is almost the same as the transmission mode of the liquid crystal display device shown in FIG. 3A, and the light emitted from the illumination device 58 is reflected by a reflective polarizing plate 57 having a transmission axis parallel to the plane of the drawing. As a result, only the polarized light component parallel to the plane of the drawing is transmitted, and transmitted through the lower polarizing layer 55 and the lower substrate 50. Then, a part of this light passes through the lower reflective polarizing layer and enters the liquid crystal 53. Here, when the liquid crystal 53 is in the ON state, the incident light reaches the upper polarizing plate 54 as it is, and is absorbed by the upper polarizing plate having a transmission axis perpendicular to the paper surface, so that the pixel is displayed in a dark state. I have. Alternatively, when the liquid crystal 53 is in the off state, the incident light is converted into polarized light perpendicular to the paper by the optical rotation of the liquid crystal 53 and transmitted through the upper polarizing plate 54. In this way, the pixels are brightly displayed.

The liquid crystal display device shown in FIG. 5 can provide a brighter display than the liquid crystal display device shown in FIG. This is because in the liquid crystal display device shown in FIG. 3, about half of the light emitted from the illumination device 58 is absorbed by the lower polarizing layer 55, whereas in the liquid crystal display device having the configuration shown in FIG. This is because light absorption by the layer 55 does not occur.

In other words, the provision of the reflective polarizing layer 57 allows the light emitted from the illumination device 58 to be reflected by the reflective polarizing plate 57 except for components parallel to the transmission axis (parallel to the paper) of the reflective polarizing plate 57. To the lighting device 58. Since this light is reflected by the reflector 59 provided on the outer surface side of the illumination device 58, the light is reflected between the reflective polarizer 57 and the reflector 59. As this reflection is repeated, the polarization state of the light changes, and a part of the light is transmitted through the reflective polarizing plate 57. When the light transmitted through the reflective polarizing plate 57 is transmitted through the lower reflective polarizing layer 51, it becomes light that contributes to display.
Further, of the light transmitted through the reflective polarizing plate 57, the light reflected on the lower surface side of the lower reflective polarizing layer 51 is also reflected between the reflective plates 59 and returns to the lower reflective polarizing layer 51, so that it is used for display. be able to. As described above, the amount of light transmitted through the lower reflective polarizing layer 51 and incident on the liquid crystal 53 increases, and the brightness of display in the transmission mode can be improved.

Here, it is preferable that an angle formed by the transmission axis of the lower polarizing layer and the transmission axis of the reflective polarizing plate is in a range of −30 ° to 30 °. In the liquid crystal display device shown in FIG. 5, of the light emitted from the illumination device 58 and transmitted through the reflective polarizing plate 57, components other than the component parallel to the transmission axis of the lower polarizing layer 55 are absorbed by the lower polarizing layer 55. The angle formed by the transmission axis of the lower polarizing layer 55 and the transmission axis of the reflection polarizing plate 57 is most preferably 0 ° (both are parallel). Is within ± 30 °, it can be used practically. If the angle formed by the two transmission axes exceeds the above range, the amount of light absorbed by the lower polarizing layer 55 will increase, and the light use efficiency will decrease, and the display brightness will decrease.

Next, in the liquid crystal display device of the present invention, the lower reflective polarizing layer may have a structure in which a dielectric interference film having a prism shape is laminated.

The lower reflective polarizing layer according to the liquid crystal display device of the present invention will be described below with reference to FIG. FIG. 6 is a perspective view showing an example of a reflective polarization layer formed by laminating a dielectric interference film having a prism shape.
Reflective polarizing layer shown in FIG. 6, on the substrate 60 formed with periodic grooves on the surface, a layer 61 made of Si, a layer 61 comprising a layer 62 _or, SiO ₂ made of SiO _2, TiO _2, Ta _This is a so-called three-dimensional photonic crystal layer formed by alternately laminating a plurality of layers 62 made of ₂ O ₅ or the like. As described above, the photonic crystal having the configuration in which the layers forming the prism shape are stacked has anisotropy in light propagation characteristics, and when light is incident from the upper side in the drawing, the incident light The component in the direction perpendicular to the groove of the substrate 60 is transmitted through the photonic crystal, and the component parallel to the groove is reflected. That is, the light Et transmitted through the reflective polarizing layer shown in FIG. 6 becomes polarized light perpendicular to the groove of the substrate 60, and the reflected light Er becomes polarized light parallel to the groove. The lamination pitch D of the layers 61 and 62 is about 0.5 μm, and the pitch P of the grooves formed on the substrate 60 is about 0.5 μm. In the liquid crystal display device shown in FIG. 3, the lower reflective polarizing layer having the above configuration is arranged so that the transmission axis is perpendicular to the plane of FIG. That is, the grooves of the substrate 60 shown in FIG. 6 are arranged so as to be parallel to the paper surface of FIG.

光 Further, the light transmittance of the reflective polarizing layer shown in FIG. 6 can be controlled by the number of stacked dielectric interference films. That is, as the number of stacked dielectric interference films increases, the light transmittance of the reflective polarizing layer decreases, and the reflectance increases. Therefore, by controlling the number of layers, a reflective polarizing layer having an arbitrary light transmittance can be obtained. Although the specific relationship between the transmittance and the number of layers is not particularly limited, when the number of layers is 8 to 12, the light transmittance is 30% (reflectance 70%).

Next, in the liquid crystal display device of the present invention, the lower reflective polarizing layer may have a configuration in which a plurality of fine slit-shaped openings are provided in the metal reflective film. This configuration will be described in detail below with reference to FIG. FIG. 7 is a perspective view illustrating an example of a reflective polarizing layer in which a plurality of fine slits are provided in a metal reflective film.
The reflective polarizing layer shown in FIG. 7 has a structure in which a plurality of slits 72 are formed at a predetermined pitch on a metal reflective film 71 of high reflectivity such as aluminum or silver formed on a substrate 70. The plurality of slits 72 are parallel to each other, and the slit width Ps is substantially the same for each slit 72. Although the size of each part is not particularly limited, the thickness d of the metal reflection film 71 is set to about 2 to 400 nm, the width Ps of the slit 72 is set to 30 nm to 300 nm, and one metal reflection film 71 is formed. The width Pm of the film 71 is set to 30 nm to 300 nm.
The reflective polarizing layer having such a configuration is configured such that when light is incident from the upper surface side, a component parallel to the length direction of the slit 72 is reflected, and a component perpendicular to the length direction of the slit 72 is transmitted. Has become. That is, the light Et transmitted through the reflective polarizing layer shown in FIG. 7 becomes polarized light perpendicular to the slit 72, and the light Er reflected by the reflective polarizing layer becomes polarized light parallel to the slit 72.

(3) In the liquid crystal display device shown in FIG. 3, the lower reflective polarizing layer having the above configuration is arranged such that the transmission axis is perpendicular to the plane of FIG. That is, the slits 72 shown in FIG. 7 are arranged such that the length direction is parallel to the paper surface of FIG. In addition, an opening for transmitting light of the lighting device is provided in a part of the reflective polarizing layer.

光 Further, the light transmittance of the reflective polarizing layer shown in FIG. 7 can be controlled by the thickness of the metal reflective film. That is, as the thickness of the metal reflection film increases, the light transmittance of the reflective polarizing layer decreases, and the reflectance increases. Therefore, by controlling this film thickness, a reflective polarizing layer having an arbitrary light transmittance can be obtained. The specific relationship between the transmittance and the film thickness is not particularly limited, but when the film thickness is 2 to 4 nm, the light transmittance is 30% (reflectance 70%).

Next, an electronic apparatus according to the present invention includes the above-described liquid crystal display device according to the present invention. According to this configuration, it is possible to realize an electronic device including an excellent display unit capable of obtaining a much brighter display in the transmission mode.

As described above in detail, the liquid crystal display device of the present invention is a transflective liquid crystal display device used while switching between the transmission mode and the reflection mode, in which a lower reflective polarizing layer is provided on the inner surface side of the lower substrate, Since the lower polarizing layer is provided below the lower reflective polarizing layer, in the transmission mode, the utilization efficiency of light emitted from the illumination device is improved, and a bright display can be realized. In, the contrast can be improved by making the dark display darker.

Next, the electronic device of the present invention includes the above-described liquid crystal display device of the present invention, so that an extremely bright display can be obtained in the transmission mode, and an electronic device having a display unit with excellent contrast is realized. can do.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a partial cross-sectional structure of the liquid crystal display device of the present embodiment. The present embodiment is an example of a passive matrix type transflective color liquid crystal display device. Note that, in the following drawings, the film thickness, the ratio of dimensions, and the like of each component are appropriately changed in order to make the drawings easy to see.

As shown in FIG. 1, a liquid crystal display device 1 according to the present embodiment has a lower substrate 2 and an upper substrate 3 opposed to each other, and a STN (Super Twisted Nematic) liquid crystal is provided in a space between the upper and lower substrates 2 and 3. And a backlight (illumination device) 5 disposed on the rear side (outer side of the lower substrate 2) of the liquid crystal panel 1. ing.

A lower reflective polarizing layer 6 having the same configuration as that shown in FIG. 6 is formed on the inner surface side of the lower substrate 2 made of glass, resin, or the like, and a transparent conductive film such as ITO is formed on the lower reflective polarizing layer 6. A stripe-shaped electrode 8 extends in the horizontal direction in the figure, and an alignment film 9 made of polyimide or the like is laminated so as to cover the electrode 8. On the outer surface of the lower substrate 2, a lower polarizing plate (lower polarizing layer) 20 and a reflective polarizing plate 21 are provided in this order. The transmission axis of the lower polarizer 20 and the transmission axis of the reflective polarizer 21 are arranged to be substantially parallel.

On the other hand, on the inner surface side of the upper substrate 3 made of glass, resin, or the like, red, green, and blue color filters 11 extend in the direction perpendicular to the paper of the drawing so as to be orthogonal to the electrodes 8 of the lower substrate 2. The flattening film 12 for flattening the unevenness formed by the color filter 11 is laminated thereon. A stripe-shaped electrode 14 made of a transparent conductive film such as ITO extends on the flattening film 12 in a direction perpendicular to the plane of the paper, and an alignment film 15 made of polyimide or the like is formed on the electrode 14 by lamination. . On the outer surface side of the upper substrate 3, a forward scattering plate 16, a phase difference plate 17, and an upper polarizing plate 13 are provided in that order on the upper substrate 3.
On the lower surface side of the backlight 5 (the side opposite to the liquid crystal panel 1), a reflection plate 18 is provided.

As shown in FIG. 6, the lower reflective polarizing layer 6 has a configuration in which a dielectric interference film having a prism shape is laminated, and the direction of the groove 60 shown in FIG. It is almost parallel. That is, the transmission axis of the lower reflective polarizing layer 6 and the transmission axis of the lower polarizing plate 20 are arranged so as to be substantially orthogonal to each other. Thereby, the light transmitted through the lower reflective polarizing layer 6 in the reflection mode can be efficiently absorbed by the lower polarizing plate 20, so that the dark display in the reflection mode is made darker and the contrast of the liquid crystal display device is improved. be able to.

The balance between the brightness in the transmission mode and the brightness in the reflection mode can be arbitrarily set by adjusting the number of layers of the lower reflective polarizing layer 6. For example, if importance is placed on the brightness in the transmission mode, the lower reflective polarizing layer 6 may be formed with a reduced number of layers, and the transmittance of the lower reflective polarizing layer 6 may be increased.

The liquid crystal display device of the present embodiment having the above-described basic configuration is configured such that the lower reflective polarizing layer 6 is formed inside the lower substrate 2, and it is essential to provide the lower reflective polarizing layer 6 on the outer surface side of the lower substrate 1 in the past. The 波長 wavelength plate is omitted. With such a configuration, the liquid crystal display device of the present embodiment can perform display with excellent visibility in both the reflection mode and the transmission mode. In particular, in the transmission mode, since no quarter-wave plate is provided on the outer surface side of the lower substrate 2, the light emitted from the backlight 5 is reflected on the back surface side of the lower reflective polarizing layer 6, and The light returning to the liquid crystal panel 1 can be reflected by the reflector 18 and returned to the liquid crystal panel 1 again. With this structure, the light of the backlight 5 can be effectively used for display, so that the brightness of the display can be remarkably improved as compared with the related art.

Further, according to the configuration of the liquid crystal display device of the present embodiment, since the reflective polarizing plate 21 is provided on the outer surface side of the lower polarizing plate 20, the reflective polarizing plate 21 out of the light emitted from the backlight 5 is provided. The component not parallel to the transmission axis is reflected by the reflective polarizer 21 and returned to the backlight 5 side, and while repeating reflection with the reflective plate 18, its polarization state changes and the reflective polarizer 21 The light can be transmitted and becomes light that can be used for display. Therefore, in the liquid crystal display device of the present embodiment, since the lower polarizing plate 20 hardly absorbs light, the light of the backlight 5 can be more efficiently used for display, and the display brightness in the transmission mode can be improved. The liquid crystal display is excellent in quality.

(Second embodiment)
In the present embodiment, the overall configuration of the liquid crystal display device is the same as that of the first embodiment shown in FIG. The difference between the liquid crystal display device of the present embodiment and the liquid crystal display device of the first embodiment is that a color filter 11 is formed immediately above the lower reflective polarizing layer 6. The point that a flattening film 12 for flattening the unevenness of the color filter 11 is provided, and only this portion will be described with reference to FIG. FIG. 2 is a diagram showing a partial cross-sectional structure of the liquid crystal display device of the present embodiment. In FIG. 2, the same components as those in FIG. 1 are denoted by the same reference numerals.

In the liquid crystal display device of the present embodiment shown in FIG. 2, since the color filter 11 is provided on the lower reflective polarizing layer 6, color shift and parallax in the reflection mode can be reduced. This is because the color filter 11 is provided immediately above the lower reflective polarizing layer 6, and after being transmitted through one dye layer (for example, R pixel), reflected by the lower reflective polarizing layer 6, the same dye layer is again formed. This is for transmission.

(Electronics)
An example of an electronic device including the liquid crystal display device of each of the above embodiments will be described.

FIG. 8A is a perspective view illustrating an example of a mobile phone. In this figure, reference numeral 1000 denotes a mobile phone main body, and reference numeral 1001 denotes a liquid crystal display unit using the above-described liquid crystal display device.

FIG. 8B is a perspective view showing an example of a wristwatch-type electronic device. In this figure, reference numeral 1100 indicates a watch body, and reference numeral 1101 indicates a liquid crystal display unit using the above-described liquid crystal display device.

FIG. 8C is a perspective view showing an example of a portable information processing device such as a word processor or a personal computer. 8C, reference numeral 1200 denotes an information processing device, reference numeral 1202 denotes an input unit such as a keyboard, reference numeral 1204 denotes an information processing device main body, and reference numeral 1206 denotes a liquid crystal display unit using the above-described liquid crystal display device.

Since the electronic devices shown in FIGS. 8A to 8C include the liquid crystal display portion using the liquid crystal display device of the above embodiment, the electronic device having the display portion capable of obtaining a bright display in the transmission mode is provided. Equipment can be realized.

Hereinafter, the effects of the present invention will be clarified by examples, but the present invention is not limited to the following examples.
(Example 1)
As Example 1, a liquid crystal display device having a configuration shown in FIG. 2 was manufactured. Each of the liquid crystal display devices was a passive matrix transflective color liquid crystal display device having a dot count of 160 dots × 120 dots and a dot pitch of 0.24 mm.
In the liquid crystal display device of Example 1, the lower reflective polarizing layer 6 was formed by laminating a dielectric interference film having the configuration shown in FIG. The number of laminated dielectric interference films of the lower reflective polarizing layer 6 was 12 (thickness: about 6 μm), and the pitch of the prism-shaped grooves was 3 μm. The transmittance of the lower reflective polarizing layer for polarized light parallel to the reflection axis was 24%.

(Example 2)
Next, as Example 2, a transflective color liquid crystal display device was manufactured in the same manner as in Example 1 except that the number of stacked dielectric interference films of the lower reflective polarizing layer 6 was changed to five. The transmittance of the lower reflective polarizing layer for polarized light parallel to the reflection axis was 65%.

(Comparative Example 1)
Next, as Comparative Example 1, a liquid crystal display device having a conventional configuration shown in FIG. 9 was manufactured. This liquid crystal display was a passive matrix type transflective color liquid crystal display having a dot count of 160 dots × 120 dots and a dot pitch of 0.24 mm similarly to the liquid crystal display of Example 1 described above.

(Evaluation)
With respect to the liquid crystal display devices of Examples 1 and 2 and Comparative Example 1, the transmittance and the reflectance corresponding to the display brightness in the transmission mode and the reflection mode were measured. Further, the contrast in each of the transmission mode and the reflection mode was also measured. Table 1 shows the measurement results.
As shown in Table 1, it was confirmed that the transmittance of the liquid crystal display device of Example 1, which is the configuration of the present invention, was improved about three times as compared with the liquid crystal display device of Comparative Example 1. . Also, the contrast at the time of transmission was 1.6 times, and it was confirmed that the contrast was greatly improved. This is because the liquid crystal display device of the first embodiment can efficiently use the light of the backlight 5 for display. Further, in the liquid crystal display device of Example 2 manufactured by reducing the number of laminated layers of the lower reflective polarizing layer 6, the transmittance is 15%, which is a remarkable improvement of twice or more as compared with the liquid crystal display device of Example 1. confirmed.

On the other hand, in the reflection mode, the reflectance of the liquid crystal display device of Example 1 was 30%, which was equivalent to that of the liquid crystal display device of Comparative Example 1, but it was confirmed that the contrast of the reflection mode was improved. Was. This improvement in contrast is due to the fact that the brightness of the bright display is the same, but the dark display is darker. Further, in the liquid crystal display device of Example 2, since the design was made with emphasis on the brightness in the transmission mode, the reflectance and the contrast in the reflection mode were slightly lower than those of the liquid crystal display device of Example 1.

FIG. 1 is a partial cross-sectional view of the liquid crystal display device according to the first embodiment of the present invention. FIG. 2 is a partial cross-sectional view of the liquid crystal display device according to the second embodiment of the present invention. 3A and 3B are explanatory diagrams for explaining the operation principle of the liquid crystal display device of the present invention. FIG. 3A shows a state in a transmission mode, and FIG. 3B shows a state in a reflection mode. 4A and 4B are explanatory diagrams for explaining the operation principle of the liquid crystal display device having the configuration shown in FIG. 10, in which FIG. 4A shows a state in a transmission mode, and FIG. 4B shows a state in a reflection mode. FIG. 5 is an explanatory diagram for explaining the operation principle of another configuration of the present invention. FIG. 6 is a perspective view showing an example of the lower reflective polarizing layer of the liquid crystal display device of the present invention. FIG. 7 is a perspective view showing an example of the lower reflective polarizing layer of the liquid crystal display device of the present invention. FIGS. 8A to 8C are perspective views showing an example of the electronic apparatus of the present invention. FIG. 9 is a partial sectional view showing an example of a liquid crystal display device having a conventional configuration. FIG. 10 is a partial cross-sectional view showing another example of the liquid crystal display device having the conventional configuration.

Explanation of reference numerals

Reference Signs List 1 liquid crystal display device 2 lower substrate 3 upper substrate 4 liquid crystal 5 backlight (illumination device)
6 Lower reflective polarizing layer 11 Color filter 13 Upper polarizing plate (upper polarizing layer)
20 Lower polarizing plate (Lower polarizing layer)
21 Reflective polarizing plate

Claims (10)

A liquid crystal is sandwiched between an upper substrate and a lower substrate facing each other, a liquid crystal panel including an upper polarizing layer and a lower reflective polarizing layer above and below the liquid crystal, and an illumination provided on an outer surface side of the liquid crystal panel. A transflective liquid crystal display device comprising a device and performing display by switching between a transmission mode and a reflection mode,
The lower reflective polarizing layer has a transmission axis and a reflection axis orthogonal to the transmission axis, reflects a part of a component parallel to the reflection axis of incident light, and is a transflective type that transmits part. A reflective polarizing layer,
A liquid crystal display device, wherein a lower polarizing layer is provided below the lower reflective polarizing layer. The liquid crystal display device according to claim 1, wherein the transmittance of the lower reflective polarizing layer for light parallel to the reflection axis is 20% or more and 70% or less. (3) The liquid crystal display device according to (2), wherein the lower reflective polarizing layer has a transmittance of light parallel to the reflection axis of 30% or more and 50% or less. 4. The liquid crystal according to claim 1, wherein an angle formed between a transmission axis of the lower reflective polarizing layer and a transmission axis of the lower polarizing layer is not less than 60 degrees and not more than 120 degrees. 5. Display device. The liquid crystal display device according to any one of claims 1 to 4, wherein a reflective polarizing plate is provided outside the lower polarizing layer. 6. The liquid crystal display device according to claim 1, wherein the lower reflection polarizing layer has a structure in which a dielectric interference film having a prism shape is laminated. 7. The liquid crystal display device according to claim 6, wherein the light transmittance of the lower reflective polarizing layer can be controlled by the number of stacked dielectric interference films. 6. The liquid crystal display device according to claim 1, wherein the lower reflective polarizing layer has a configuration in which a fine slit-shaped opening is provided in a metal reflective film. 7. 9. The liquid crystal display device according to claim 8, wherein the light transmittance of the lower reflective polarizing layer can be controlled by the thickness of the metal reflective film. An electronic apparatus comprising the liquid crystal display device according to claim 1.

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