JP2010044145A - Liquid crystal device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal device reducing degradation of contrast and coloring. <P>SOLUTION: The liquid crystal device 10 is equipped with: a liquid crystal panel 12 having a liquid crystal layer interposed between transparent substrates 2 and 3; a polarizing plate 1 disposed on the viewing side of the liquid crystal panel 12; and a polarizing plate 11 disposed on the rear side of the liquid crystal panel 12. The polarizing plate 11 is equipped with: a reflection type polarizing plate 5 reflecting a polarization component parallel to a reflection axis and transmitting a polarization component parallel to a transmission axis; and a first absorption type polarizing plate 4 on the viewing side of a second absorption type polarizing plate 6. A retardation plate is further provided between the polarizing plate 1 and the second absorption type polarizing plate 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a liquid crystal device having polarizing means on the front and back sides of a liquid crystal panel.

  As a reflective polarizing plate, an optical film that reflects a polarized component parallel to the reflection axis and transmits a polarized component parallel to the transmission axis has been put into practical use. The most widespread use of this reflective polarizing plate is to increase the light utilization efficiency (extraction efficiency of linearly polarized light) of the back lighting device based on the idea of recycling the reflected light (see, for example, Patent Document 1). ). For example, in a liquid crystal display device of a mobile phone, a light reflection efficiency is often improved by inserting a reflective polarizing plate between a liquid crystal cell having two polarizing plates and a backlight device. In order to further improve the light utilization efficiency, a retardation plate may be inserted between the backlight device and the reflective polarizing plate (see, for example, Patent Document 2).

  As another usage of the reflective polarizing plate, a liquid crystal display device that displays a colored character or figure on a silver (or mirror) background is known (for example, see Patent Document 3). In addition, there is a liquid crystal device in which characters and figures can be displayed on a background with a metallic color by adding some ideas (for example, see Patent Document 4). In this liquid crystal device, a reflective polarizing plate, a color polarizing plate, a liquid crystal cell, and an absorbing polarizing plate are laminated on a light absorption layer. This color polarizing plate absorbs components other than a specific wavelength among linearly polarized light having a vibration surface in the absorption axis direction (a specific wavelength component is transmitted), and a straight line having a vibration surface in a direction parallel to the transmission (easy) axis. Transmits polarized light. At this time, the absorption axis of the color polarizing plate and the reflection axis of the reflective polarizing plate are set in parallel. That is, in a laminate including a reflective polarizing plate and a color polarizing plate on a light absorption layer, a region where polarized light parallel to the absorption axis of the color polarizing plate is incident is colored metallic, and polarized light in a direction perpendicular to the absorption axis. The incident area is black. Note that the polarization region is controlled by liquid crystal.

  Therefore, the present inventors replaced the light absorption layer in the liquid crystal device of Patent Document 4 with an absorptive polarizing plate, and reflected the liquid crystal device in a reflection mode for displaying characters and figures on a colored metallic gloss display surface. A liquid crystal device having a transmission mode in which an object on the opposite side can be seen has been developed. The reflection mode and the transmission mode mean whether the light source (including light emitted from the object) is on the viewing side or the back side. This liquid crystal device will be described with reference to FIGS. FIG. 10 is a sectional view showing a member laminated structure including a display / shutter portion of a liquid crystal cell included in the liquid crystal device (hereinafter, the sectional view includes a display / shutter portion). FIG. 11 is an exploded perspective view of the laminated member in the display / shutter portion of the liquid crystal device shown in FIG. 10, and also shows the optical axis of each polarizing plate (arrow in the figure). 10 and 11, the same members are denoted by the same reference numerals, and redundant description is omitted.

In the liquid crystal device 100 shown in FIG. 10, a reflective polarizing plate 85 and a color polarizing plate 84 are laminated on an absorption polarizing plate 86 disposed on the opposite side to the viewing side, and these are polarized on the back side. Functions as a board. A second transparent substrate 83, a first transparent substrate 82, and a viewing-side absorption polarizing plate 81 are laminated on the back side polarizing plate. Between the first transparent substrate 82 and the second transparent substrate 83, a twisted nematic liquid crystal layer (not shown; hereinafter referred to as a TN liquid crystal layer) having a liquid crystal molecular alignment twisted by 90 ° is sandwiched. Electrodes are formed on the surfaces of the first and second transparent substrates 82 and 83 on the TN liquid crystal layer side (not shown). A voltage is applied to the TN liquid crystal layer by this electrode, and characters and figures are displayed. Note that light (polarized light) incident on a planar region to which no voltage is applied (hereinafter referred to as an OFF region) is rotated by 90 ° in the liquid crystal layer. On the other hand, light (polarized light) incident on a planar region to which a voltage is applied (hereinafter referred to as an ON region) does not rotate in the liquid crystal layer. The major axis direction of the liquid crystal molecules in contact with the transparent substrate 82 and the transmission axis direction of the absorption-type polarizing plate 81 on the viewing side coincide with each other so that birefringence does not occur.

  Next, the optical axes of the polarizing plates 81, 84, 85, and 86 will be described with reference to FIG. The transmission axis 92 and the absorption axis 91 of the absorption-type polarizing plate 81 on the viewing side are orthogonal to each other. Similarly, the transmission axis 94 and the absorption axis 93 of the color polarizing plate 84, the transmission axis 96 and the reflection axis 95 of the reflection type polarizing plate 85, and the transmission axis 98 and the absorption axis 97 of the absorption type polarizing plate 86 are also orthogonal to each other. All the transmission axes 92, 94, 96, 98 are parallel.

  Next, the reflection mode will be described. The light incident on the OFF region (background portion) from the viewing side is polarized in the direction of the transmission axis 92 when passing through the absorption-type polarizing plate 81 on the viewing side. This polarized light is rotated 90 ° in the liquid crystal layer and reaches the color polarizing plate 84. At this time, since the polarization direction is parallel to the absorption axis 93, only a specific wavelength component passes through the color polarizing plate 84 and reaches the reflective polarizing plate 85. The polarized light colored by the color polarizing plate 84 is reflected by the reflective polarizing plate 85 because the polarization direction is parallel to the reflection axis 95, and returns to the viewing side following the reverse course. On the other hand, light that has entered the ON region (character or graphic display) from the viewing side is transmitted through the viewing-side absorption polarizing plate 81 and polarized in the direction of the transmission axis 92, but is not rotated in the liquid crystal layer. The light is emitted from the first absorption type polarizing plate 86 to the back surface side. That is, in the reflection mode, the OFF region is a mirror surface (a metallic gloss surface), and the ON region is black.

  Next, the transmission mode will be described. The light incident on the ON region from the back side is polarized in the direction of the transmission axis 98 after passing through the absorption polarizing plate 86. This polarized light is transmitted through the reflective polarizing plate 85 and the color polarizing plate 84, and also passes through the first polarizing plate 81 because the same polarization direction is maintained in the liquid crystal layer. That is, the polarized light in the transmission axis direction that has entered the ON region exits through the liquid crystal device as it is. The background portion of the liquid crystal device prototyped by the inventors of the present application is provided with electrodes, and this region can also be controlled on / off. Therefore, if both the background part and the display part are in the ON region, the back side can be seen through from the viewing side in the transmission mode. Further, by turning off the entire surface (or part) of the liquid crystal device, light incident from the back surface can be blocked.

In fact, if the reflective polarizing plate 85 has ideal characteristics, the above-described function can be satisfied without the absorption polarizing plate 86. However, in reality, since the polarization separation ability of the reflective polarizing plate 85 is low, coloring of the light shielding region in the transmission mode occurs without the second absorption polarizing plate 86. Therefore, the second absorption type polarizing plate 86 is added to prevent deterioration of the light shielding characteristics.
Japanese National Patent Publication No. 11-509331 JP 2007-4174 A JP 11-2111864 A JP 2000-314879 A

  However, in the above-described conventional liquid crystal device, there is a problem that transmitted light is colored in the transmission mode despite the addition of the absorption-type polarizing plate 86. In addition, there is a problem in that the contrast reduction cannot be sufficiently suppressed in the transmission mode.

  An object of the present invention is to provide a liquid crystal device capable of reducing contrast reduction and coloring.

The present invention relates to a liquid crystal panel having a liquid crystal layer sandwiched between two transparent substrates, a first polarizing means disposed on the viewing side of the liquid crystal panel, and a second polarization disposed on the back side of the liquid crystal panel. The second polarizing means includes a reflective polarizing plate that reflects a polarization component parallel to the reflection axis and transmits a polarization component parallel to the transmission axis, and a first absorption polarizing plate. On the viewing side of the second absorption type polarizing plate, and further comprising a retardation plate between the first polarizing means and the second absorption type polarizing plate. is there.

  The retardation plate may be provided between the first absorption polarizing plate and the second absorption polarizing plate. Further, the reflective polarizing plate may be disposed between the first absorbing polarizing plate and the second absorbing polarizing plate, and the retardation plate may be provided between the reflective polarizing plate and the second absorbing polarizing plate. Good.

  In this case, it is preferable that the transmission axis of the first absorption polarizing plate and the slow axis of the retardation plate are parallel.

  The retardation plate is provided between the first polarizing means and the first absorption polarizing plate, and the slow axis of the retardation plate and the transmission axis of the first absorption polarizing plate are parallel. It may be.

  The retardation plate may be a λ / 4 retardation plate.

  Further, a display unit having a display function may be further provided on the side opposite to the viewing side, and the second absorption polarizing plate may function as an absorption polarizing layer of the display unit.

  Further, the first absorptive polarizing plate transmits only light having a specific wavelength out of polarized light in a direction orthogonal to the transmission axis, absorbs light having a wavelength other than the specific wavelength, and transmits polarized light in a direction parallel to the transmission axis. It may be a color polarizing plate.

  Furthermore, the transparent substrate may be a plastic substrate.

  According to the present invention, in a liquid crystal device provided with polarizing means on the viewing side and the back side of the liquid crystal panel, the polarizing means disposed on the back side reflects polarized light components parallel to the reflection axis and polarized light parallel to the transmission axis. A reflection type polarizing plate that transmits the component and a first absorption type polarizing plate are provided on the viewing side of the second absorption type polarizing plate, and further, a polarizing means and a second absorption type arranged on the viewing side. Since the retardation plate is inserted between the polarizing plates, the contrast is improved in the transmission mode, and coloring can be reduced.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of the drawings, the same or corresponding elements are denoted by the same reference numerals, and redundant description is omitted.
(First embodiment)

  Hereinafter, a first embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a cross-sectional view of the liquid crystal device according to the first embodiment. FIG. 2 is an exploded perspective view of the liquid crystal device according to the first embodiment. FIG. 3 is an explanatory diagram for explaining a light path and a polarization state. FIG. 4 is a diagram showing experimental results of the liquid crystal device of the first embodiment.

First, the laminated structure of the liquid crystal device 10 according to the first embodiment of the present invention will be described with reference to FIG. On the back lighting device 8, a second absorption polarizing plate 6, a retardation plate 7, a reflection polarizing plate 5, a color polarizing plate 4 (first absorption polarizing plate), and a liquid crystal layer between the transparent substrates 2 and 3. And a liquid crystal panel 12 having an absorption type, and an absorption type polarizing plate 1 (first polarizing means) disposed on the viewing side. The transparent substrates 2 and 3 constitute a liquid crystal panel by sandwiching a TN liquid crystal layer (not shown) in which the liquid crystal molecular alignment is twisted by 90 ° in the gap. Electrodes (not shown) for driving the liquid crystal layer are formed on the surfaces of the transparent substrates 2 and 3 on the TN liquid crystal layer side. In addition, the laminated body which consists of the 2nd absorption type polarizing plate 6, the phase difference plate 7, the reflection type polarizing plate 5, and the color polarizing plate 4 functions as the polarizing plate 11 (2nd polarizing means) of the back side.

  Next, the optical axes of the respective polarizing plates 1, 4, 5 and 6 and the phase difference plate 7 will be described with reference to FIG. 2. In the polarizing plate 1 arranged on the viewing side, the transmission axis 22 and the absorption axis 21 are orthogonal. Similarly, the transmission axis 24 and the absorption axis 23 of the color polarizing plate 4, the transmission axis 26 and the reflection axis 25 of the reflective polarizing plate 5, the slow axis 30 and the fast axis 29 of the retardation film 7, and the second absorption type. The transmission axis 28 and the absorption axis 27 of the polarizing plate 6 are orthogonal to each other. Further, the transmission axes 22, 24, 26, 28 of all the polarizing plates 1, 4, 5, 6 and the slow axis 30 of the retardation plate 7 are parallel.

  Next, the light beam L1 incident on the OFF region of the reflection mode will be described with reference to FIG. In the figure, it is assumed that the transmission axes 22, 24, 26, and 28 of the polarizing plates 1, 4, 5, and 6 and the slow axis 30 of the phase difference plate 7 are oriented in a direction parallel to the paper surface (the same applies hereinafter). ). When the light beam L1 passes through the absorption-type polarizing plate 1 arranged on the viewing side, only the linearly polarized light component in the direction indicated by the arrow 31 (parallel to the paper surface) remains. This light beam L1 is rotated by 90 ° in the TN liquid crystal layer sandwiched between the transparent substrates 2 and 3, and the polarization direction is the direction indicated by the circle 34 (perpendicular to the paper surface). Since this light ray L1 is parallel to the absorption axis 23 of the color polarizing plate 4, when the light passes through the color polarizing plate 4, components other than a specific wavelength component are absorbed. That is, the light beam L1 is colored. This state is indicated by a broken line in the figure. When the light beam L 1 reaches the reflective polarizing plate 5, the light is reflected by the reflective polarizing plate 5 because the polarization direction is parallel to the reflection axis 25 of the reflective polarizing plate 5. The reflected light beam L1 follows the reverse path and is emitted from the polarizing plate 1 in a colored manner. That is, the OFF region in the reflection mode is a colored mirror surface (metal gloss surface).

  Next, the light ray L2 incident on the reflection mode ON region will be described. When the light beam L2 passes through the polarizing plate 1, only the linearly polarized light component in the direction indicated by the arrow 31 (parallel to the paper surface) remains. Even if the light beam L2 passes through the TN liquid crystal layer, the polarization direction does not change. That is, the polarization direction remains parallel to the paper surface as indicated by the arrow 35. Since the polarization direction of the light beam L2 is parallel to the transmission axis 24 of the color polarizing plate 4, it passes through the color polarizing plate 4 as it is. Similarly, the reflection-type polarizing plate 5 and the second absorption-type polarizing plate 6 also transmit. Then, the light is reflected by the back lighting device 8 and returns to the viewing side along the reverse path. However, the intensity of the light beam L2 is attenuated by passing through many optical films twice or being reflected by the backlight device 8 having a low reflectance. This is indicated by a dotted line in the figure. That is, the reflection mode ON region looks dark.

  Next, the light beam L3 incident on the transmission mode ON region will be described. When the light beam L3 enters the second absorption polarizing plate 6, only the linearly polarized light component in the direction indicated by the arrow 37 (parallel to the paper surface) remains. The light beam L 3 passes through the retardation plate 7, the reflective polarizing plate 5, and the color polarizing plate 4 as it is, and reaches the back surface of the transparent substrate 3. That is, the light beam L3 is polarized in the direction of the arrow 36 while being colorless on the back surface of the transparent substrate 3. Even if the light beam L3 passes through the TN liquid crystal layer, the polarization direction is directed in the direction of the arrow 32, and therefore passes through the absorption-type polarizing plate 1 on the viewing side. That is, the ON region of the transmission mode is a light transmission region.

  Finally, the light beam L4 incident on the OFF region of the transmission mode will be described. When the light beam L4 enters the second absorption polarizing plate 6, only the linearly polarized light component in the direction indicated by the arrow 37 (parallel to the paper surface) remains. The light beam L 4 passes through the retardation plate 7, the reflective polarizing plate 5, and the color polarizing plate 4 as it is, and reaches the back surface of the transparent substrate 3. At this time, the light beam L4 is polarized in the direction of the arrow 36. The light beam L4 is rotated 90 ° in the TN liquid crystal layer, and the polarization direction is directed to the direction of the circle 33 (perpendicular to the paper surface). For this reason, the light ray L4 is absorbed by the polarizing plate 1 on the viewing side. That is, the OFF region in the transmission mode is a light-shielded region.

Here, a liquid crystal device with a liquid crystal panel having a liquid crystal layer whose polarization direction is completely rotated by 90 ° is sandwiched between polarizing plates having ideal characteristics, and can transmit and block complete light (linearly polarized light). Should be. However, if the polarizing plate (second polarizing means) in which the reflective polarizing plate 5 and the color polarizing plate 4 (first polarizing means) are stacked on the second absorption polarizing plate 6 is simply attached to the back surface of the liquid crystal panel. Decrease in contrast or coloration occurs in the transmission mode.

  The inventors have improved the contrast and reduced the coloration in the transmission mode by inserting the retardation plate 7 between the polarizing plate 1 (first polarizing means) and the second absorption polarizing plate 6. I found. Furthermore, it has also been found that reduction in contrast and coloring can be most improved by making the transmission axis of the second absorption polarizing plate 6 parallel to the slow axis of the retardation plate.

  When a retardation plate is provided between the reflective polarizing plate and the second absorption polarizing plate, only the transmission mode is improved and the reflective mode is not affected, so that the display characteristics of the reflective mode are good. It is effective in such cases.

  In the description of FIG. 3, it is assumed that the polarizing plates 1, 4, 5, 6 and the liquid crystal layer have ideal polarization characteristics, and that the retardation plate 7 has no effect (loss due to transmission). except). In other words, since the polarization directions of the light beams L3 and L4 coincide with the direction of the slow axis 30 (the direction of the arrow 37, parallel to the paper surface), abnormal light (or ordinary light) should not be generated even when entering the phase difference plate 7. It is. That is, birefringence does not occur. However, as described above, without the retardation plate 7, coloring and contrast reduction occurred. On the other hand, it was visually observed that when the retardation plate 7 was inserted, coloring and contrast reduction were improved. An example in which the degree of improvement is measured will be described with reference to FIG.

  FIG. 4 shows transmittance 1 when there is no retardation plate and transmittance 2 when there is a retardation plate for the liquid crystal devices (device numbers 1, 2, and 3). Although the contrast values vary, each liquid crystal device has a higher contrast when the retardation plate is present than when there is no retardation plate. Here, the improvement in contrast is mainly due to a decrease in the black level.

  This experimental condition is shown. The absorption-type polarizing plate 1 and the second absorption-type polarizing plate 6 arranged on the viewing side are made of a triacetyl cellulose (hereinafter referred to as TAC) substrate and have a thickness of 110 μm. The transparent substrates 2 and 3 are made of polycarbonate and have a thickness of 120 μm. The first absorption polarizing plate 4 is made of a TAC substrate and has a thickness of 215 μm. In this experiment, a normal absorption type polarizing plate was used as the first absorption type polarizing plate 4 instead of a color polarizing plate. As the reflective polarizing plate 5, DBEF (registered trademark) manufactured by Sumitomo 3M Co. was used. The phase difference plate 7 is a λ / 4 plate made of polycarbonate and having a thickness of 40 μm.

In the experiment of FIG. 4, the transmission axis 24 of the first absorption type polarizing plate 4 and the slow axis 30 of the phase difference plate 7 are made parallel. In parallel with this experiment, the transmission axis 24 and the slow axis 30 were shifted from parallel, and the coloring situation was visually observed. As a result, the coloring was the least when the transmission axis and the slow axis were parallel. Similar results were obtained when the transparent substrates 2 and 3 were made of glass.
(Second Embodiment)

Hereinafter, a liquid crystal device according to a second embodiment of the present invention will be described with reference to FIG. FIG. 5 is a cross-sectional view showing the liquid crystal device of the second embodiment. The liquid crystal device 110 according to the present embodiment is different from the liquid crystal device 10 according to the first embodiment in that the retardation film 7 is disposed on the reflective polarizing plate 5. Also in the present embodiment, it is possible to improve contrast reduction and coloring in the transmission mode.
(Third embodiment)

Next, a liquid crystal device according to a third embodiment of the present invention will be described with reference to FIG.
FIG. 6 is a cross-sectional view of the liquid crystal device of the third embodiment. The liquid crystal device 120 according to the present embodiment is different from the liquid crystal device 10 according to the first embodiment in that the retardation film 7 is disposed below the absorption-type polarizing plate 1 on the viewing side. Also in the present embodiment, it is possible to improve contrast reduction and coloring in the transmission mode. At this time, the slow axis 30 of the phase difference plate 7 and the transmission axis of the first absorption polarizing plate 4 are parallel. This optical axis relationship is different from that of a display device having a retardation plate and a polarizing plate and utilizing birefringence. The retardation plate may be on the first absorption type polarizing plate 4.
(Fourth embodiment)

  Hereinafter, a liquid crystal device according to a fourth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a cross-sectional view of the liquid crystal device of the fourth embodiment. In the liquid crystal device 130 according to the present embodiment, the stacked portion from the viewing-side absorption polarizing plate 1 to the second absorption polarizing plate 6 corresponds to the liquid crystal device 10 of the first embodiment in FIG. The laminated portion 65 in which the transparent substrates 62 and 61 and the second absorption-type polarizing plate 6 are laminated on the fourth polarizing plate 63 is a TFT liquid crystal cell provided with a TFT (thin film transistor) as a switching element for each pixel. is there. That is, the liquid crystal device 130 shown in FIG. 7 has a configuration in which the liquid crystal device 10 of the first embodiment is stacked on a TFT liquid crystal cell (display unit 65) and the second absorption polarizing plate 6 is shared.

When the liquid crystal device of this embodiment is used in the reflection mode, the TFT liquid crystal cell (display unit 65) and the backlight 8 are stopped. As a result, the same operation as in the reflection mode of the first embodiment is performed, and black characters and figures are displayed on the background made of a colored metallic glossy surface. On the other hand, when the liquid crystal device of this embodiment is used in the transmission mode, the TFT liquid crystal cell (display unit 65) and the backlight 8 are operated after the liquid crystal device 10 is set in the transmission state. As a result, a high-quality image displayed on the TFT liquid crystal cell (display unit 65) can be viewed with little color shift (coloring). If necessary, the liquid crystal device 10 may be entirely or partially light-shielded.
(Fifth embodiment)

  Hereinafter, a liquid crystal device according to a fifth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a cross-sectional view of the liquid crystal device of the fifth embodiment. In the liquid crystal device 140 according to the present embodiment, the laminated portion from the first absorption polarizing plate 1 to the second absorption polarizing plate 6 corresponds to the liquid crystal device 10 of the first embodiment in FIG. In the laminated portion 68 in which the λ / 4 phase plate 66 and the second absorption polarizing plate 6 are laminated on the organic EL (electroluminescence) panel main body 67, the external light incident on the organic EL panel main body 67 is the second polarizing plate. 6 and an organic EL cell that is prevented from returning to the viewing side by the λ / 4 phase plate 66. That is, the liquid crystal device 140 shown in FIG. 8 has a configuration in which the liquid crystal device 10 of the first embodiment is stacked on an organic EL cell (display unit 68) and the second absorption polarizing plate 6 is shared.

When the liquid crystal device 140 of the present embodiment is used in the reflection mode, the organic EL cell (display unit 68) is stopped. As a result, the same operation as in the reflection mode of the first embodiment is performed, and black characters and figures are displayed on the background made of a colored metallic glossy surface. On the other hand, when the liquid crystal device 10 of the present embodiment is used in the transmission mode, the organic EL cell (display unit 68) is operated after setting the liquid crystal device 10 to the transmission state. As a result, a high-quality image displayed on the organic EL cell (display unit 68) can be viewed with little color shift (coloring). If necessary, the liquid crystal device 10 may be entirely or partially light-shielded.
(Sixth embodiment)

  In the first to fifth embodiments, the first absorption polarizing plate is the color polarizing plate 4. FIG. 9 shows an example in which the first absorption polarizing plate is a normal absorption polarizing plate as the liquid crystal device of the sixth embodiment.

  FIG. 9 is a sectional view showing a liquid crystal device 150 according to the sixth embodiment. In FIG. 9, the laminated portion 77 including the first absorption polarizing plate 71, the transparent substrates 2 and 3, and the polarizing plate 1 on the reflective polarizing plate 5 functions as a liquid crystal cell. This liquid crystal cell has a keyboard area 75 and a display area 76. In the keyboard region 75, an EL illumination sheet 72 is disposed on the back surface of the liquid crystal cell. Further, there is a pressure-sensitive key sheet 73 under the EL lighting sheet 72. Here, the key sheet 73 is an electronic component in which a plurality of switches are arranged on the sheet. In order to transmit the pressure applied from the surface of the liquid crystal cell to the key sheet 73, the transparent substrates 2 and 3 are plastic sheets (plastic substrates). In the display unit 76, a TFT liquid crystal cell (display unit 65) is disposed on the back surface of the liquid crystal cell via the phase difference plate 7, and a back lighting device 8 is disposed below the TFT liquid crystal cell (display unit 65). Yes.

  Next, the reflective polarizing plate 5 will be described. The reflective polarizing plate 5 in the keyboard portion 75 is a light enhancement film for the EL illumination sheet 72. On the other hand, the reflective polarizing plate in the display unit 76 functions as a device that uniformizes the device surface color during standby. In other words, the liquid crystal cell is configured so that the surface of the device becomes black during standby. However, since the transparent substrates 2 and 3 are plastic sheets, the contrast of the liquid crystal cell is lowered even though the absorption type polarizing plate 71 having good polarization separation characteristics is provided. Therefore, the reflective polarizing plate 5 is attached over the entire back surface of the liquid crystal cell to achieve a uniform surface color during standby.

  When the transparent substrate is made into a plastic for reducing the thickness and weight of the device, contrast often decreases and coloring occurs. If a polarizing plate in which a reflective polarizing plate and a first absorbing polarizing plate are laminated on a second absorbing polarizing plate is adopted as the polarizing plate (polarizing means) on the back surface side, contrast reduction and coloring are further deteriorated. To do. Therefore, by inserting the above-described retardation plate into the liquid crystal device of the present embodiment, the degree of contrast reduction and coloring improvement can be made greater than those of the glass substrate.

  The laminated structure of the display unit 76 is obtained by replacing the color polarizing plate 4 in the fourth embodiment of FIG. As a result, the retardation plate 7 is inserted between the second absorption-type polarizing plate 6 and the reflective-type polarizing plate 5 as in the fourth embodiment, so that it is displayed in the TFT liquid crystal cell 65 in the display area 76. It is possible to see the image without coloring.

  When the display unit is arranged on the back side of the liquid crystal panel as in the above-described liquid crystal device, the display screen of the display unit can be seen in the transmission mode of the liquid crystal panel. Since the reduction of the contrast and the coloring can be suppressed by inserting the retardation plate as described above, loss (deterioration in image quality) caused by stacking the liquid crystal panel on the display unit can be reduced. When the display unit includes a polarizing plate on the viewing side and emits linearly polarized light, it is most efficient if the polarization direction of the emitted light matches the transmission axis direction of the second absorption polarizing plate. At this time, by making the second absorption polarizing plate function as an absorption polarizing layer on the viewing side of the display unit, the liquid crystal device can be thinned while realizing the maximum light utilization efficiency.

1 is a cross-sectional view showing a liquid crystal device according to a first embodiment of the present invention. 1 is an exploded perspective view showing a liquid crystal device according to a first embodiment of the present invention. It is explanatory drawing of the light ray of the liquid crystal device which concerns on the 1st Embodiment of this invention. It is a figure which shows the experimental result of the liquid crystal device which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the liquid crystal device which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the liquid crystal device which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the liquid crystal device which concerns on the 4th Embodiment of this invention. It is sectional drawing which shows the liquid crystal device which concerns on the 5th Embodiment of this invention. It is sectional drawing which shows the liquid crystal device which concerns on the 6th Embodiment of this invention. It is sectional drawing which shows the conventional liquid crystal device. It is a disassembled perspective view which shows the conventional liquid crystal device.

Explanation of symbols

1, 81 ... Polarizing plate (first polarizing means)
2, 3, 82, 83 ... Transparent substrate 4, 84 ... Color polarizing plate (first absorption polarizing plate)
5, 85 ... reflective polarizing plates 6, 86 ... second absorption polarizing plate 7 ... phase difference plate 8 ... back illumination device 11 ... polarizing plate (second polarizing means)
12 ... Liquid crystal panels 21, 23, 27, 91, 93, 97 ... Absorption axes 22, 24, 26, 28, 92, 94, 98 ... Transmission axes 25, 95 ... Reflection axes 29 ... Fast axis 30 ... Slow axis 31 to 37: Polarization directions L1, L2, L3, L4 ... Light 65: TFT liquid crystal cell (display unit)
68 ... Organic EL cell (display unit)
71 ... 1st absorption type polarizing plate 72 ... EL illumination sheet 73 ... Key sheet 75 ... Keyboard region 76 ... Display region 77 ... Liquid crystal cell 110, 120, 130, 140, 150 ... Liquid crystal device

Claims (9)

A liquid crystal panel having a liquid crystal layer sandwiched between two transparent substrates, a first polarizing means arranged on the viewing side of the liquid crystal panel, and a second polarizing means arranged on the back side of the liquid crystal panel In the liquid crystal device provided,
The second polarizing means includes a reflective polarizing plate that reflects a polarization component parallel to the reflection axis and transmits a polarization component parallel to the transmission axis, and a first absorption polarizing plate as a second absorption polarizing plate. Configured for the viewing side of
The liquid crystal device further comprises a retardation plate between the first polarizing means and the second absorption polarizing plate.   The liquid crystal device according to claim 1, wherein the retardation plate is provided between the first absorption polarizing plate and the second absorption polarizing plate.   The reflective polarizing plate is disposed between the first absorbing polarizing plate and the second absorbing polarizing plate, and the retardation plate is provided between the reflective polarizing plate and the second absorbing polarizing plate. The liquid crystal device according to claim 1, wherein the liquid crystal device is provided.   4. The liquid crystal device according to claim 2, wherein a transmission axis of the first absorption-type polarizing plate and a slow axis of the retardation plate are parallel. 5.   The retardation plate is provided between the first polarizing means and the first absorption polarizing plate, and a slow axis of the retardation plate and a transmission axis of the first absorption polarizing plate. The liquid crystal device according to claim 1, wherein and are parallel to each other.   The liquid crystal device according to claim 1, wherein the retardation plate is a λ / 4 retardation plate.   A display unit having a display function is further provided on the side opposite to the viewing side, and the second absorption polarizing plate functions as an absorption polarizing layer of the display unit. The liquid crystal device according to item.   The first absorption-type polarizing plate transmits only light having a specific wavelength out of polarized light in a direction orthogonal to the transmission axis, absorbs light having a wavelength other than the specific wavelength, and transmits polarized light in a direction parallel to the transmission axis. The liquid crystal device according to claim 1, wherein the liquid crystal device is a color polarizing plate.   The liquid crystal device according to claim 1, wherein the transparent substrate is a plastic substrate.

Images