JP2006133810A - Display device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device capable of performing bright display, without accompanying steep increase in power consumption, by effectively using light as a display capable of displaying on both the front and the rear surfaces. <P>SOLUTION: The liquid crystal display 100 is equipped with two liquid crystal cells 10 and 20, a backlight 40 which is formed between the liquid crystal cells 10 and 20 and can irradiate the liquid crystal cells 10 and 20 with light, and two reflecting and polarizing plates 31 and 32, which are formed between the back light 40 and respective liquid crystal cells 10 and 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

    The present invention relates to a display device and an electronic apparatus, and more particularly to a display device that enables display from both front and back surfaces.

  2. Description of the Related Art Conventionally, a display device in which a light source serving as a backlight is sandwiched between two liquid crystal panels and display on both front and back sides is known. For example, Patent Document 1 or Patent Document 2 describes this type of display device.

JP-A-10-90678 Japanese Patent Laid-Open No. 2001-290445

In the display device as described above, a polarizing plate is arranged between the liquid crystal panel and the light source so that only polarized light in a predetermined direction is incident on the liquid crystal panel. In this case, the polarizing axis (transmission axis) of the polarizing plate is used. ) Is not absorbed by the polarizing plate, the amount of light that can be used for display is significantly reduced, and the display may be darkened. Therefore, in order to obtain a bright display, a brighter light source is required, and as a result, the problem of high power consumption may occur.
Further, when observed from the side of one liquid crystal panel, the display quality deteriorated due to the shadow of the other liquid crystal panel being observed.

  The present invention has been made to solve the above-described problem, and is a display device capable of displaying both front and back surfaces, which effectively uses backlight light and is bright without increasing power consumption. A display device capable of display and capable of preventing deterioration of display quality caused by observing the shadow of the other liquid crystal panel when observed from the one liquid crystal panel side, and an electronic apparatus including the display device The purpose is to provide.

  In order to achieve the above object, a display device of the present invention is a display device comprising first transmission polarization axis varying means and second transmission polarization axis varying means, wherein the second transmission polarization axis is provided. The size of the display area of the axis variable means is made smaller than the size of the display area of the first transmission polarization axis variable means, and the first transmission polarization axis variable means and the second transmission polarization axis variable means An illuminating means disposed between the illuminating means and the second transmissive polarization axis variable means, and disposed between the illuminating means and the second transmissive polarization axis variable means. A reflection-type polarization selection means, wherein the illumination means is capable of transmitting the reflected light from the reflection-type polarization selection means, and light absorption is performed between the second transmission polarization axis varying means and the illumination means. A light-shielding layer made of a body is provided, and the light-shielding layer has the second transmission polarization axis. So as to correspond to the size of the display area of the variable means, wherein the light-transmissive region is provided.

According to such a display device, only the transmitted light (referred to as the first polarized light) transmitted and selected by the reflective polarization selection means among the illumination light emitted by the illumination means is used as the second transmission polarization axis variable means. On the other hand, the reflected light having a predetermined polarization direction (reflected as the second polarized light) reflected and selected by the reflection-type polarization selection means is changed to the first transmission polarization axis on the opposite side via the illumination means. It will enter the means. Since the first transmission polarization axis variable means can selectively emit to the outside, the illumination light emitted by the illumination means can be used for display without waste. Therefore, in a display device capable of displaying both front and back surfaces, light can be used effectively and bright display can be achieved without increasing power consumption.
Further, a light shielding layer made of a light absorber is disposed between the second transmission polarization axis varying means and the illumination means, and the light shielding layer is provided in the display area of the second transmission polarization axis varying means. Since the light transmission region is provided so as to correspond to the size, it is caused by observing the shadow of one transmission polarization axis variable unit when observed from the second transmission polarization axis variable unit side. Deterioration of display quality can be prevented.
In addition, as a reflection type polarization | polarized-light selection means, the laminated body which laminated | stacked multiple types of mutually different birefringent polymer films, or the thing using the circular dichroism of a cholesteric liquid crystal etc. can be used, for example. Examples of the reflection-type polarized light selecting means include DBEF (trade name) provided by 3M Company and optical films such as NIPOCS provided by Nitto Denko Corporation.

  Another embodiment of the display device of the present invention is a display device comprising a first transmission polarization axis variable means and a second transmission polarization axis variable means, wherein the second transmission polarization axis variable means displays. The size of the area is made smaller than the size of the display area of the first transmission polarization axis variable means, and is disposed between the first transmission polarization axis variable means and the second transmission polarization axis variable means. Illuminating means capable of irradiating light to the first and second transmission polarization axis variable means, and a reflection type polarization selection means disposed between the illumination means and the first transmission polarization axis variable means. The illuminating means is capable of transmitting the reflected light from the reflective polarization selection means, and a light-blocking light comprising an optical absorber is provided between the second transmission polarization axis varying means and the illuminating means. A light-shielding layer is provided on the display area of the second transmission polarization axis varying means. So as to correspond to the size, characterized in that the light-transmissive region is provided.

According to another aspect of the present invention, there is provided a display device including a first transmission polarization axis variable unit and a second transmission polarization axis variable unit, wherein the second transmission polarization axis variable unit includes: The size of the display area is made smaller than the size of the display area of the first transmission polarization axis variable means, and is arranged between the first transmission polarization axis variable means and the second transmission polarization axis variable means. And illumination means capable of irradiating light to the first and second transmission polarization axis variable means, and a first reflection disposed between the illumination means and the first transmission polarization axis variable means. Type polarization selection means, and second reflection type polarization selection means disposed between the illumination means and the second transmission polarization axis varying means, wherein the illumination means is the first reflection type polarization. The reflected light from the selection means and the reflected light from the second reflective polarization selection means can be transmitted. A light-shielding layer made of a light absorber is disposed between the second second transmission polarization axis varying unit and the illumination unit, and the light-shielding layer is displayed on the second transmission polarization axis varying unit. A light transmission region is provided so as to correspond to the size of the region.
Here, the reflection type polarization selection means reflects linear polarization in a predetermined direction and transmits linear polarization in a direction crossing the reflection direction. The two reflection type polarization selection means reflect each other. It can be set in the direction in which the polarization axes intersect. When the reflection type polarization selection unit that selects reflection or transmission based on the polarization axis direction is used as described above, the reflection polarization axes of the reflection type polarization selection units are crossed (preferably orthogonal) to each other. As described above, the reflected light reflected by one of the reflection type polarization selection means can be efficiently transmitted by the other reflection type polarization selection means.

  Furthermore, when the reflection type polarization selection means for selecting the polarization based on the difference in the polarization axis direction is applied, a polarization axis (in a predetermined direction) is provided between the reflection type polarization selection means and the transmission polarization axis variable means. Forming absorption-type polarization selection means that transmits polarized light having a polarization axis in a direction intersecting with the polarization axis (hereinafter also referred to as transmission polarization axis), The reflection polarization axis of the reflection type polarization selection means and the transmission polarization axis of the absorption type polarization selection means can be set in a direction crossing each other. That is, by selecting again the polarization selected by the reflection type polarization selection unit using the absorption type polarization selection unit, the polarization selectivity incident on the transmission polarization axis variable unit is further increased, and the transmission polarization axis is variable. The display characteristics emitted from the means are further improved. In particular, since the absorption polarization selection means generally has higher polarization selectivity than the reflection polarization selection means, the absorption polarization selection means is provided between the reflection polarization selection means and the transmission polarization axis variable means. As a result, the polarization selectivity of the light incident on the transmission polarization axis varying means is further increased.

  On the other hand, the reflection type polarization selecting means is constituted by a cholesteric liquid crystal using circular polarization dichroism, and reflects circular polarization in a predetermined rotation direction, while transmitting circular polarization in the opposite rotation direction. Polarization selection means can be used. In this case, it is preferable that the two reflection-type polarization selection means (reflection-type circular polarization selection means) set the rotation directions of the circularly polarized light to be reflected in the same direction.

  The reflection-type circularly polarized light selecting means using cholesteric liquid crystal selectively reflects circularly polarized light incident in a predetermined rotational direction (first rotational direction) as seen from the light traveling direction side, with conversion of the rotational direction. On the other hand, circularly polarized light that is incident in the rotation direction (second rotation direction) in the other direction is selected for transmission. In the case of the present invention, the direction in which the light comes is used as a reference for determining the rotation direction.

Therefore, as described above, if the rotation directions of the circularly polarized light to be reflected are set to the same direction for the two reflective circularly polarized light selecting means (for example, the first rotational direction is set to be reflected), the first rotation is performed. The circularly polarized light having the direction is reflected by one of the reflective circularly polarized light selecting means to be in the second rotational direction, transmitted through the other reflective circularly polarized light selecting means, and output to the transmissive polarization axis variable means. It becomes possible.
That is, when the reflective circularly polarized light selecting means is used, the reflected light reflected by one of the reflective polarized light selecting means as described above is changed to the same direction by setting the rotation direction of the circularly polarized light to be reflected to the same direction. It is possible to transmit with the reflection type polarization selection means.

In the case of using the reflection type circularly polarized light selecting means, a λ / 4 phase difference plate is provided between the reflective type circularly polarized light selecting means and the transmission polarization axis varying means to transmit the reflective type circularly polarized light selecting means. The circularly polarized light having a predetermined rotation direction is converted into linearly polarized light in a direction parallel to the transmitted polarization axis of the transmission polarization axis variable means, and the linearly polarized light is selectively converted with polarization axis conversion in the transmission polarization axis variable means. It will be emitted.
By disposing a scattering member between the reflection-type polarization selection unit and the absorption-type polarization selection unit, surface reflection of the reflection-polarization selection unit can be suppressed and reflection can be prevented.

  The illumination means includes a light source and a light guide plate that guides light from the light source, the birefringence amount of the light plate is λ / 2, the slow axis of the light guide plate, and the reflection of each reflection type polarization selection means The angle formed with the polarization axis can be set to about 45 °. In this case, since the angle formed between the slow axis of the light guide plate and the reflection polarization axis of the reflection type polarization selection means is set to about 45 °, the illumination light emitted from the light guide plate is reflected in the reflection type polarization selection means. By shifting the phase of the linearly polarized light reflected and returned by λ / 2, the direction of the linearly polarized light is changed by 90 °. In this case, even if the reflective polarization axes of the two reflective polarizers are arranged in parallel, the reflected light is reflected. The light is surely transmitted through the other reflective polarization selection means.

  Next, an electronic apparatus according to the present invention includes the display device. Such an electronic device can display both front and back surfaces with low power consumption and a simple configuration, and can provide bright display on both surfaces.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings shown in the present embodiment, the film thicknesses and ratios of dimensions of the respective components are appropriately changed in order to make the drawings easy to see.

[First Embodiment]
FIG. 1 is a cross-sectional view showing a schematic configuration of a liquid crystal display device according to a first embodiment of the display device of the present invention. FIG. 2 is a diagram for explaining the display principle. It is a figure which shows only a required component.

  As shown in FIG. 1, the liquid crystal display device 100 of the present embodiment includes a pair of liquid crystal cells 10 and 20 and a backlight (illumination device) 40 common to the liquid crystal cells 10 and 20. Transmitted light from the backlight 40 is emitted to the display surfaces 1 and 2 through the liquid crystal cells 10 and 20 to perform display on both the front and back surfaces. In the liquid crystal cell 10 (20), an upper substrate 13 (24) and a lower substrate 14 (23) are arranged to face each other, and a liquid crystal is placed in a space sandwiched between the upper substrate 13 (24) and the lower substrate 14 (23). Is enclosed to form the liquid crystal layer 15 (25). Note that the liquid crystal layer 15 (25) of the liquid crystal cells 10 and 20 functions as a transmission polarization axis varying unit, and TN liquid crystal having a 90 ° twist angle is used as the liquid crystal. In the present embodiment, the backlight 40 side of the liquid crystal cells 10 and 20 is the back side (rear side), and the opposite side is the observation side (front side).

  The backlight 40 is disposed on the back side of the liquid crystal cells 10 and 20 as illumination means. The backlight 40 includes a light source 42 and a light guide plate 41 made of a cold cathode tube, an LED, and the like, and each of the liquid crystal cells 10, 20 from the longitudinal side surface of the light guide plate 41 (surface viewed from the liquid crystal cells 10, 20). 20 can be irradiated with light. As the backlight 40, it is possible to obtain a structure that emits light on both sides using, for example, an organic EL as a light source. In this case, since the organic EL light is a surface-emitting light source, complicated design and processing for uniformly emitting light from the side surface to the front and back surfaces of the light guide plate are not required. Also, moire due to interference with the pattern of the light guide plate is less likely to occur. Furthermore, it is preferable that the light guide plate 41 is made of a material with little birefringence, such as an acrylic resin, a PC resin, a polyolefin resin, or the like so that the polarization state of the reflected polarized light hardly changes.

  Between each of the liquid crystal cells 10 and 20 and the backlight 40, reflective polarizing plates 31 and 32 are disposed as reflective polarization selection means, respectively. The reflective polarizing plates 31 and 32 reflect linearly polarized light in a predetermined direction while transmitting linearly polarized light in a direction intersecting with the linearly polarized light. In the present embodiment, the reflective polarizing plates 31 and 32 are each It is set in the direction in which the reflection polarization axes intersect.

  The absorption polarizing plate 11 (22) is arranged on the observation side of the liquid crystal cell 10 (20), and the absorption polarizing plate 12 (21) is also arranged on the backlight 40 side (back side) of the liquid crystal cell 10 (20). Has been. In this case, the transmission polarization axis of the absorbing polarizing plate 12 (21) is set in substantially the same direction as the transmission polarization axes of the reflection polarizing plates 31 and 32.

  In the liquid crystal cell 10 (20), a pixel electrode (not shown) made of a transparent conductive film such as ITO (Indium Tin Oxide) is provided on the inner surface side of the lower substrate 14 (23) made of a translucent material such as glass or plastic. An alignment film (not shown) made of polyimide or the like is laminated so as to cover the pixel electrode. In the case of the present embodiment, the lower substrate 14 (23) is composed of a pixel switching element such as a TFT, an element substrate on which a data line, a scanning line, etc. are formed. Illustration of scanning lines and the like is omitted.

  On the other hand, on the inner surface side of the upper substrate 13 (24) made of a translucent material such as glass or plastic, a common electrode (not shown) made of a transparent conductive film such as ITO, an alignment film made of polyimide or the like (not shown). Are sequentially stacked.

  Both the alignment films on the upper substrate 13 (24) side and the lower substrate 14 (23) side are subjected to a horizontal alignment process such as a rubbing process, and the alignment directions of the alignment films on the upper substrate side and the lower substrate side are: The liquid crystal set in the direction intersecting each other and sandwiched between both substrates was twisted by 90 °. The liquid crystal molecules of the liquid crystal layer 15 are aligned in a direction perpendicular to the substrate surface between the upper substrate 13 (24) and the lower substrate 14 (23) when a selection voltage is applied (voltage on). In this embodiment, the 90 ° twisted TN liquid crystal is exemplified. However, the liquid crystal mode is not limited to this mode, and needless to say, it can be applied to other liquid crystal modes.

  Further, the back-side absorption polarizing plate 12 (21) and the observation-side absorption polarizing plate 11 (22) are set so that the transmission axis directions intersect like the alignment directions of the alignment films. That is, as shown in FIG. 2, the transmission polarization axis of the back-side absorption polarizing plate 12 (21) is substantially parallel to the alignment direction of the alignment film formed on the inner surface of the lower substrate 14 (23) and is reflective. It is set substantially parallel to the transmission polarization axis of the polarizing plate 31 (32), and the transmission polarization axis of the absorption polarizing plate 11 (22) on the observation side intersects the transmission polarization axis of the absorption polarizing plate 12 (21) on the back side ( It is set to be preferably orthogonal.

  Hereinafter, the display principle of the liquid crystal display device 100 of the present embodiment will be described with reference to FIG. First, as shown on the left side of FIG. 2, the light emitted from the light guide plate 41 to the first liquid crystal cell 10 (front side liquid crystal cell 10) side is subjected to polarization selection by the front side reflective polarizing plate 31. . That is, polarized light (first polarized light) having a polarization axis parallel to the transmission polarization axis (direction parallel to the paper surface) of the reflective polarizing plate 31 is transmitted through the reflective polarizing plate 31, while Polarized light (second polarized light) having a polarization axis parallel to the reflective polarization axis (direction perpendicular to the paper surface) is reflected by the reflective polarizing plate 31.

  The first polarized light transmitted through the reflective polarizing plate 31 is transmitted through the absorption polarizing plate 12 on the back side of the liquid crystal cell 10 (the direction in which the transmission polarization axis is parallel to the paper surface) and is incident on the liquid crystal layer 15. At 15, the polarization axis is converted based on the application state of the selection voltage. When the selection voltage is not applied (voltage off), the liquid crystal layer 15 is transmitted along with the conversion of the polarization axis, and further, the absorption polarizing plate 11 on the observation side (the direction of the transmission polarization axis is perpendicular to the paper surface) is transmitted. The display side (first display surface) on the front side is bright (white). On the contrary, in the selection voltage application state (voltage on), although it passes through the liquid crystal layer 15 without conversion of the polarization axis, it is absorbed by the absorption polarizing plate 11 on the observation side and becomes dark (black) display.

  On the other hand, the second polarized light reflected by the reflective polarizing plate 31 passes through the light guide plate 41 and enters the reflective polarizing plate 32 on the back side. In this case, since the light guide plate 41 is formed of a material having low birefringence (preferably substantially zero) as described above, the polarization axis is not converted when passing through the light guide plate 41.

  Since the reflective polarizing axis 32 of the back side is set so that the reflective polarizing axis thereof intersects the reflective polarizing axis of the reflective polarizing plate 31 of the front side, the second polarized light incident on the reflective polarizing plate 32 of the back side is The light passes through the reflective polarizing plate 32, passes through the absorption polarizing plate 21 (the direction in which the transmission polarization axis is perpendicular to the paper surface) on the back side of the second liquid crystal cell 20 (back side liquid crystal cell), and enters the liquid crystal layer 25. Then, the polarization axis is converted in the liquid crystal layer 25 based on the application state of the selection voltage. In the non-selection voltage application state (voltage off), the liquid crystal layer 25 is transmitted with the conversion of the polarization axis, and further, the absorption polarizing plate 22 on the observation side (the direction in which the transmission polarization axis is parallel to the paper surface) is transmitted, The display surface (second display surface) on the back side is bright (white). On the other hand, in the selection voltage application state (voltage on), the light is transmitted through the liquid crystal layer 25 without conversion of the polarization axis, but is absorbed by the absorption polarizing plate 22 on the observation side and becomes dark (black) display.

  On the other hand, as shown on the right side of FIG. 2, the light emitted from the light guide plate 41 to the liquid crystal cell 20 on the back side is also selected for polarization by the reflective polarizing plate 31 on the back side as described above, and the third While the polarized light is transmitted through the reflective polarizing plate 32, the fourth polarized light is reflected by the reflective polarizing plate 32, and the transmitted third polarized light is transmitted through the liquid crystal cell 20 to the rear display surface (second display surface). ) Can be emitted. The reflected fourth polarized light can be emitted to the front display surface (first display surface) via the front-side reflective polarizing plate 31 and the liquid crystal cell 10, thereby enabling display on both the front and back surfaces. It is said.

  As described above, in this embodiment, the polarized light reflected by one reflective polarizing plate (for example, the reflective polarizing plate 31) can be transmitted through the other reflective polarizing plate (for example, the reflective polarizing plate 32). Use efficiency increases, and the brightness of the front and back panels increases. In addition, since one light guide plate can also serve as illumination for two liquid crystal panels, the thickness can be reduced and the number of components can be reduced.

[Second Embodiment]
In this embodiment, the birefringence amount of the light guide plate 41 is set to approximately zero. However, for example, the birefringence amount of the light guide plate 41 is set to λ / 2, and the slow axis of the light guide plate 41 and the reflection polarizing plates 31 and 32 are The angle formed with the reflection polarization axis can be set to about 45 °, and the reflection polarization axes of the reflection polarizing plates 31 and 32 can be made parallel. As described above, when the angle formed between the slow axis of the light guide plate 41 and the reflective polarization axes of the reflective polarizing plates 31 and 32 is set to about 45 °, the reflective polarizing plate out of the illumination light emitted from the light guide plate 41. Since the linearly polarized light reflected and returned by the light passes through the light guide plate 41 and the phase of the reflected light is shifted by λ / 2, the direction of the linearly polarized light is rotated by 90 °. Since the reflection polarizing axes of the reflection polarizing plates 31 and 32 are parallel, the linearly polarized light reflected by one reflection polarizing plate is rotated by 90 ° by the light guide plate and is perpendicular to the reflection axis of the other reflection polarizing plate ( Therefore, the reflected light is surely transmitted through the other reflective polarizing plate. Thus, the angle of the reflection polarization axis of each reflective polarizing plate can be changed by 90 ° by controlling the birefringence amount and the axial direction of the light guide plate. In addition, the clear viewing direction of the liquid crystal display device can be changed.

[Third Embodiment]
FIG. 3 is a cross-sectional view showing a schematic configuration of the liquid crystal display device of the second embodiment, and FIG. 4 is a diagram for explaining the display principle, and shows only the components necessary for explaining the display principle. FIG. Note that components having the same reference numerals as those of the liquid crystal display device 100 of the first embodiment shown in FIG. 1 have the same configuration unless otherwise specified.

  As shown in FIG. 3, the liquid crystal display device 200 includes two liquid crystal cells 10 and 20 and a backlight (illumination device) 40 common to the liquid crystal cells 10 and 20, as in the first embodiment of FIG. The transmitted light from the backlight 40 is emitted to the display surfaces 1 and 2 through the liquid crystal cells 10 and 20 to display on both the front and back surfaces.

  Between each of the liquid crystal cells 10 and 20 and the backlight 40, reflective polarizing plates 35 and 36 are disposed as reflective polarization selection means, respectively. The reflective polarizing plates 35 and 36 are made of cholesteric liquid crystal and reflect circularly polarized light in a predetermined rotational direction, while transmitting circularly polarized light in the opposite rotational direction. In the present embodiment, each reflective polarized light is reflected. In the plates 35 and 36, the rotational directions of the circularly polarized light reflected are set in the same direction. That is, the circularly polarized light reflected by one reflective polarizing plate 35 can be transmitted through the other reflective polarizing plate 36.

  A λ / 4 retardation plate 16 (26) is disposed on the back side of the liquid crystal cell 10 (20), that is, on the back side of the absorbing polarizing plate 12 (21). In this case, the phase difference axis of the λ / 4 retardation plate 16 (26) is a straight line that can be transmitted through the absorption polarizing plate 12 (21) after the circularly polarized light is transmitted through the λ / 4 retardation plate 16 (26). It is set to be polarized light.

  Hereinafter, the display principle of the liquid crystal display device 200 of the present embodiment will be described with reference to FIG. In addition, the rotation direction of the circularly polarized light shown below shall show the rotation direction seen from the light traveling direction opposite side.

  First, as shown on the left side of FIG. 4, the light emitted from the light guide plate 41 toward the first liquid crystal cell 10 (front side liquid crystal cell 10) is subjected to polarization selection by the front side reflective polarizing plate 35. . That is, in the reflective polarizing plate 35, the circularly polarized light whose rotation direction is counterclockwise (first polarized light) is transmitted through the reflective polarizing plate 35, while the circularly polarized light whose rotation direction is clockwise (second polarized light) is Reflected by the reflective polarizing plate 35. The reflected circularly polarized light becomes counterclockwise circularly polarized light (third polarized light).

  The first polarized light transmitted through the reflective polarizing plate 35 passes through the λ / 4 retardation plate 16 formed on the back side of the liquid crystal cell 10 and becomes linearly polarized light having a polarization axis in a direction parallel to the paper surface. The linearly polarized light passes through the absorption polarizing plate 12 (the direction of the transmission polarization axis is parallel to the paper surface) and enters the liquid crystal layer 15, and the polarization axis is converted by the liquid crystal layer 15 based on the selection voltage application state. Done. When the selection voltage is not applied (voltage off), the liquid crystal layer 15 is transmitted along with the conversion of the polarization axis, and further, the absorption polarizing plate 11 on the observation side (the direction of the transmission polarization axis is perpendicular to the paper surface) is transmitted. The display side (first display surface) on the front side is bright (white). On the contrary, in the selection voltage application state (voltage on), although it passes through the liquid crystal layer 15 without conversion of the polarization axis, it is absorbed by the absorption polarizing plate 11 on the observation side and becomes dark (black) display.

  On the other hand, the second polarized light reflected by the reflective polarizing plate 35 passes through the light guide plate 41 and enters the reflective polarizing plate 36 on the back side. In this case, since the light guide plate 41 is formed of a material having low birefringence (preferably substantially zero) as described above, the rotation direction of the circularly polarized light is converted when passing through the light guide plate 41. Not accompanied.

  Since the reflection rotation direction of the back side reflection polarizing plate 36 is set so as to intersect the reflection rotation direction of the front side reflection polarizing plate 35, the second polarized light incident on the back side reflection polarizing plate 36 is The light passes through the reflective polarizing plate 36, passes through the λ / 4 retardation plate 26 formed on the back side of the second liquid crystal cell 20 (back side liquid crystal cell), and has a polarization axis in a direction parallel to the paper surface. It becomes linearly polarized light, and further, the linearly polarized light is transmitted through the absorption polarizing plate 21 (the direction of the transmission polarization axis is parallel to the paper surface) and enters the liquid crystal layer 25, and the liquid crystal layer 25 is based on the application state of the selection voltage. Conversion of the polarization axis is performed.

  When the selection voltage is not applied (voltage off), the liquid crystal layer 25 is transmitted along with the conversion of the polarization axis, and further, the absorption polarizing plate 22 on the observation side (the transmission polarization axis is perpendicular to the paper surface) is transmitted. The display surface (second display surface) on the back side is bright (white). On the other hand, in the selection voltage application state (voltage on), the light is transmitted through the liquid crystal layer 25 without conversion of the polarization axis, but is absorbed by the absorption polarizing plate 22 on the observation side and becomes dark (black) display.

  On the other hand, as shown on the right side of FIG. 2, the light emitted from the light guide plate 41 to the back side liquid crystal cell 20 is also selected by the back side reflective polarizing plate 36 in the same manner as described above, and is counterclockwise. While circularly polarized light (third polarized light) is transmitted through the reflective polarizing plate 36, clockwise circularly polarized light (fourth polarized light) is reflected by the reflective polarizing plate 36, and the reflected light is counterclockwise circularly polarized light. (First polarization).

  The third polarized light transmitted through the reflective polarizing plate 36 can be emitted to the rear display surface (second display surface) via the liquid crystal cell 20. Also, the reflected first polarized light can be emitted to the front display surface (first display surface) via the front reflective polarizing plate 35 and the liquid crystal cell 10, thereby enabling display on both the front and back surfaces. It is said.

  As described above, also in the present embodiment, the reflective polarizing plate is configured by a cholesteric liquid crystal using circular dichroism, and polarization selection is performed based on the rotation direction of circularly polarized light. Since the polarized light reflected by the reflective polarizing plate (for example, the reflective polarizing plate 35) can be transmitted through the other reflective polarizing plate (for example, the reflective polarizing plate 36), the light utilization efficiency is increased. Brightness increases. In addition, since one light guide plate can also serve as illumination for two liquid crystal panels, the thickness can be reduced and the number of components can be reduced.

[Fourth Embodiment]
FIG. 5 is a cross-sectional view showing a schematic configuration of the liquid crystal display device of the third embodiment. The liquid crystal display device has a configuration in which scattering layers 51 and 52 made of films whose surfaces are roughened are disposed between the liquid crystal cells 10 and 20 and the reflective polarizers 35 and 36, respectively. Except for the above, the configuration is the same as that of the first embodiment shown in FIG. With the above-described configuration, it is possible to prevent specular reflection of the reflective polarizing plate. Moreover, since the surface is roughened, the generation of Newton rings can be suppressed.
In this embodiment, a film material whose surfaces are roughened is used as the scattering layers 51 and 52. However, the liquid crystal cell 10 is formed using a scattering adhesive layer in which beads are mixed in the adhesive layer and a scattering function is added. , 20 may be configured such that reflective polarizing plates 35, 35 are attached to the respective plates. With the above-described configuration, it is possible to further reduce the thickness in addition to the above-described effects. In addition, it is possible to prevent positional deviation due to vibration and impact and contamination of foreign matters.

[Fifth Embodiment]
FIG. 6 is a sectional view showing a schematic configuration of the liquid crystal display device of the fourth embodiment. As shown in FIG. 6, the size of the display area of the liquid crystal cells 10 and 20 is different, and the size of the display area of the liquid crystal cell 20 is smaller than the size of the display area of the liquid crystal cell 10. A light shielding layer 61 made of a light absorber is disposed between the liquid crystal cell 20 and the reflective polarizing plate 32. Other configurations are the same as those in the first embodiment shown in FIG.
By adopting the above-described configuration, it is possible to reduce deterioration in display quality caused by observing the shadow of the liquid crystal cell 20 when observed from the liquid crystal cell 10 side.

[Sixth Embodiment]
Next, with reference to FIG.7 and FIG.8, the electronic device of 6th Embodiment which concerns on this invention is demonstrated. A mobile phone 1000 according to an embodiment of the electronic apparatus of the present invention is a foldable mobile phone having a folded state shown in FIG. 7 and a use state shown in FIG. 1002.

  The liquid crystal display device is arranged inside the display body portion 1002, and the display body portion 1002 is configured so that the display screen can be viewed on the front side display surface 1003 and the back side display surface 1004. According to such a mobile phone 1000, a bright display screen is visually recognized on the front display surface 1003 and / or the back display surface 1004 according to various operations and various situations, in particular, depending on the state change between the folded state and the use state. Will be able to.

  The embodiments of the liquid crystal display device according to the display device of the present invention and the mobile phone according to the electronic device of the present invention have been described above, but the present invention is not limited to this, and departs from the gist of the present invention. Various modifications can be made within the range not to be performed.

1 is a cross-sectional view showing a schematic configuration of a liquid crystal display device according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram illustrating a display principle of the liquid crystal display device of FIG. 1. Sectional drawing which shows schematic structure of the liquid crystal display device of 3rd Embodiment of this invention. FIG. 4 is an explanatory diagram illustrating a display principle of the liquid crystal display device of FIG. 3. Sectional drawing which shows schematic structure of the liquid crystal display device of 4th Embodiment of this invention. Sectional drawing which shows schematic structure of the liquid crystal display device of 5th Embodiment of this invention. The perspective view which shows the folding state of the electronic device of 6th Embodiment of this invention. FIG. 8 is a perspective view illustrating a usage state of the electronic device of FIG. 7.

Explanation of symbols

100, 200 Liquid crystal display device, 10, 20 Liquid crystal cell (transmission polarization axis variable means), 11, 12, 21, 22, Absorption polarizing plate (absorption polarization selection means), 31, 32, 35, 36 Reflection polarizing plate (reflection) Type polarization selection means), 15, 25 liquid crystal layer (transmission polarization axis variable means), 40 backlight, 41 light guide plate, 42 light source, 51, 52 scattering layer, 61 light shielding layer

Claims (10)

A display device comprising first transmission polarization axis varying means and second transmission polarization axis varying means,
The size of the display area of the second transmission polarization axis variable means is made smaller than the size of the display area of the first transmission polarization axis variable means,
An illuminating unit disposed between the first transmission polarization axis variable unit and the second transmission polarization axis variable unit, and capable of irradiating the first and second transmission polarization axis variable units with light;
A reflection-type polarization selection unit disposed between the illumination unit and the second transmission polarization axis variable unit;
The illumination means is capable of transmitting the reflected light from the reflective polarization selection means;
A light-shielding layer made of a light absorber is disposed between the second transmission polarization axis varying unit and the illumination unit,
The display device, wherein the light shielding layer is provided with a light transmission region so as to correspond to a size of the display region of the second transmission polarization axis varying unit. A display device comprising first transmission polarization axis varying means and second transmission polarization axis varying means,
The size of the display area of the second transmission polarization axis variable means is made smaller than the size of the display area of the first transmission polarization axis variable means,
An illuminating unit disposed between the first transmission polarization axis variable unit and the second transmission polarization axis variable unit, and capable of irradiating the first and second transmission polarization axis variable units with light;
A reflection-type polarization selection unit disposed between the illumination unit and the first transmission polarization axis varying unit;
The illumination means is capable of transmitting the reflected light from the reflective polarization selection means;
A light-shielding layer made of a light absorber is disposed between the second transmission polarization axis varying unit and the illumination unit,
The display device, wherein the light shielding layer is provided with a light transmission region so as to correspond to a size of the display region of the second transmission polarization axis varying unit. A display device comprising first transmission polarization axis varying means and second transmission polarization axis varying means,
The size of the display area of the second transmission polarization axis variable means is made smaller than the size of the display area of the first transmission polarization axis variable means,
An illuminating unit disposed between the first transmission polarization axis variable unit and the second transmission polarization axis variable unit, and capable of irradiating the first and second transmission polarization axis variable units with light;
A first reflection-type polarization selection unit disposed between the illumination unit and the first transmission polarization axis variable unit; and a unit between the illumination unit and the second transmission polarization axis variable unit. Second reflected polarization selection means,
The illumination means is capable of transmitting reflected light from the first reflective polarization selection means and reflected light from the second reflective polarization selection means;
A light-shielding layer made of a light absorber is disposed between the second transmission polarization axis varying unit and the illumination unit,
The display device, wherein the light shielding layer is provided with a light transmission region so as to correspond to a size of the display region of the second transmission polarization axis varying unit. The two reflective polarization selection means reflect linearly polarized light in a predetermined direction while transmitting linearly polarized light in a direction intersecting the predetermined direction,
The display device according to claim 3, wherein the two reflection-type polarization selection units are set in directions in which the reflection polarization axes intersect each other. Between the first reflective polarization selection means and the first transmission polarization axis variable means or between the second reflection polarization selection means and the second transmission polarization axis variable means in a predetermined direction. Absorptive polarization selection means that absorbs linearly polarized light while transmitting linearly polarized light in a direction intersecting the linearly polarized light is formed.
The reflection polarization axis of the first reflection type polarization selection unit or the reflection polarization axis of the second reflection type polarization selection unit and the transmission polarization axis of the absorption type polarization selection unit are set to intersect each other. The display device according to claim 1, wherein the display device is a display device.   The reflection type polarization selection means is composed of cholesteric liquid crystal and reflects circular polarization in a predetermined rotation direction while transmitting circular polarization in the opposite rotation direction. The two reflection type polarization selection means 4. The display device according to claim 1, wherein the rotation directions of the circularly polarized light respectively reflected are set in the same direction. 5.   Λ / 4 position between the first reflective polarization selection means and the first transmission polarization axis variable means or between the second reflection polarization selection means and the second transmission polarization axis variable means The display device according to claim 6, further comprising a phase difference plate.   8. The display device according to claim 5, wherein a scattering member is disposed between the reflection-type polarization selection unit and the absorption-type polarization selection unit. 9.   The illumination unit includes a light source and a light guide plate that guides light from the light source, and the birefringence amount of the light guide plate is λ / 2, the slow axis of the light guide plate, and the reflective polarization selection unit 9. The display device according to claim 1, wherein an angle formed by the reflection polarization axis is set to about 45 °.   An electronic apparatus comprising the display device according to claim 1.

Images