JP5690861B2 - Liquid crystal device - Google Patents

Description

  Embodiments described herein relate generally to a liquid crystal device.

Liquid crystal devices are widely used as display devices for personal computers, portable information terminals, televisions, car navigation systems, and the like by taking advantage of features such as light weight, thinness, and low power consumption.
Further, as a liquid crystal device, a liquid crystal device using a polarizing plate, such as TN (twisted nematic), STN (super twisted nematic), IPS (In-Plane Switching), VA (vertically aligned), OCB (Optically Compensated Bend) mode, etc. Has been proposed.
On the other hand, as a liquid crystal device that does not use a polarizing plate, a liquid crystal device using a scattering type liquid crystal has been proposed. A typical method of the scattering type liquid crystal is PDLC (polymer dispersed liquid crystal).

JP 2004-325907 A

  However, in a scattering type liquid crystal device, it is difficult to obtain a sufficient scattering intensity by applying a voltage of about 5 V by driving a thin film transistor (TFT), and in order to obtain a sufficient scattering intensity, the cell gap must be increased, and the driving voltage Needed to be high.

  Further, when a black light absorber is disposed on the back surface of the scattering type liquid crystal device, black at the time of transmission can be displayed well, but white at the time of scattering may be displayed darkly. In addition, when a mirror is arranged on the back side, white display at the time of scattering is relatively good, but when reflected, the mirror reflection on the back side can be seen, so that the contrast may be lowered depending on the angle. If nothing is arranged on the back side, the transparent side can be seen through at the time of transmission, so that a display giving a futuristic impression can be realized. However, there is a case where the contrast between scattering and transmission is lowered.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal device that realizes good display characteristics.

The liquid crystal device according to the embodiment is disposed on the back side of the first liquid crystal panel including a pair of substrates and a scattering type liquid crystal sandwiched between the pair of substrates, and facing the first liquid crystal panel. An active mirror, and a first polarizing plate that is disposed on the back side of the active mirror so as to face the active mirror and transmits linearly polarized light having a first polarization direction, the active mirror including the first liquid crystal A second polarizing plate disposed on the side facing the panel and absorbing linearly polarized light having a polarization direction of the first direction; a polarizing direction transmitting linearly polarized light having the first direction; and a polarization direction orthogonal to the first direction. An optical sheet that reflects linearly polarized light in the second direction, and a polarization conversion element that is disposed between the second polarizing plate and the optical sheet and that can convert the polarization direction of incident light . and the active mirror, before The first state where the polarization direction incident from the first polarizing plate side transmits the linearly polarized light in the first direction, and the polarization direction incident from the first polarizing plate side absorbs the linearly polarized light in the first direction or This is a liquid crystal device capable of switching between the second state of reflection.

It is a figure which shows one structural example at the time of the mirror mode of the liquid crystal device which concerns on 1st Embodiment. It is a figure which shows one structural example at the time of the transmissive mode of the liquid crystal device which concerns on 1st Embodiment. It is a figure which shows the example of 1 structure of the active mirror of the liquid crystal device shown in FIG. FIG. 3 is a diagram illustrating a configuration example of an active mirror of the liquid crystal device illustrated in FIG. 2. It is a figure which shows the example of 1 structure of the active mirror of the liquid crystal device which concerns on 2nd Embodiment. It is a figure which shows the example of 1 structure of the active mirror of the liquid crystal device which concerns on 2nd Embodiment.

Hereinafter, the liquid crystal device according to the first embodiment will be described with reference to the drawings.
FIG. 1 shows a configuration example of the liquid crystal device according to the first embodiment. The liquid crystal device according to the present embodiment includes a scattering-type liquid crystal panel 10, a lighting device 20, and an active mirror 30.

  The scattering type liquid crystal panel 10 is a liquid crystal panel that does not use a polarizing plate, and includes a pair of electrode substrates (first substrate 12 and second substrate 14) and a scattering type liquid crystal sandwiched between the pair of electrode substrates. ing. The scattering liquid crystal is, for example, PDLC or PNLC (Polymer network liquid crystal), and is a liquid crystal that can be switched between a scattering state and a transmission state by a voltage applied to the liquid crystal. The scattering liquid crystal has a liquid crystal dispersed in a polymer, and enters a transmission state when a voltage is applied.

  The illumination device 20 includes a light guide LG and a light source 22. The light guide LG has a substantially rectangular parallelepiped shape, and includes a light incident surface facing the light source 22 and a light emitting surface facing the scattering type liquid crystal panel 10. The light guide LG guides light emitted from the light source to the scattering liquid crystal panel 10 and transmits light incident from the back side to the scattering liquid crystal panel 10 side.

  The lighting device 20 can be omitted. When the light guide LG and the scattering type liquid crystal panel 10 are arranged to face each other, the portion in the scattering display state is displayed in white, and the portion in the transmissive display state can be transmitted. In addition, it is desirable that the light guide LG is not subjected to scattering dots or prism cuts, but places importance on transparency.

The active mirror 30 is disposed on the back side of the lighting device 20 and can switch between a transmission state (first state) and a reflection state (second state).
FIG. 1 shows a configuration example when the active mirror 30 is in a reflecting state. When the active mirror 30 is in the reflective state, the contrast of the scattering-type liquid crystal panel 10 is displayed. In this example, a liquid crystal panel 40 and a backlight 50 are further arranged on the back side of the active mirror 30.

The liquid crystal panel 40 is an active matrix liquid crystal panel including a display unit (not shown) including display pixels arranged in a matrix, for example. A polarizing plate 42 is disposed on the main surface of the liquid crystal panel 40 on the side facing the active mirror 30. The polarizing plate 42 is disposed so that the light whose polarization direction is the second direction D2 is transmitted. When the active mirror 30 is in the transmissive state, the light transmitted through the polarizing plate 42 is transmitted through the active mirror 30, and when the active mirror 30 is in the reflective state, the light transmitted through the polarizing plate 42 is reflected by the active mirror 30. The
The backlight 50 is disposed so as to illuminate the display unit of the liquid crystal panel 40.

  FIG. 3 shows a configuration example of the active mirror 30 in the reflective state. The active mirror 30 includes a polarizing plate 32 facing the lighting device 20, an optical sheet 36, and a polarization conversion element 34 disposed between the polarizing plate 32 and the optical sheet 36.

  The polarizing plate 32 is disposed so as to transmit light whose polarization direction is the first direction D1 and absorb light whose polarization direction is the second direction D2. For example, the light whose polarization direction is the first direction D1 is an S wave, and the light whose polarization direction is the second direction D2 is a P wave.

  The polarization conversion element 34 switches between a λ / 2 plate that can convert linearly polarized light into the other linearly polarized light and a state without optical modulation. The polarization conversion element 34 includes a pair of electrode substrates arranged opposite to each other and a TN mode liquid crystal layer as a light modulation layer sandwiched between the pair of electrode substrates. A voltage is applied to the TN mode liquid crystal when the active mirror 30 is in the reflective state.

In the present embodiment, the TN mode liquid crystal is uniformly applied with a voltage from a pair of electrode substrates, but the electrodes arranged on the pair of electrode substrates are divided into regions, and the voltage applied to the TN mode liquid crystal for each region. May be controlled.
The optical sheet 36 is designed to transmit light whose polarization direction is the second direction D2 and reflect light whose polarization direction is the first direction D1 to the incident side. For example, 3EF DBEF can be used. .

  Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the first direction D <b> 1 passes through the polarizing plate 32 and enters the polarization conversion element 34. The light incident on the polarization conversion element 34 is emitted with the polarization direction of the first direction D1 without changing the phase. The light emitted from the polarization conversion element 34 is returned to the polarization conversion element 34 side without passing through the optical sheet 36, is again transmitted through the polarization conversion element 34 and the polarizing plate 32, and is emitted to the scattering liquid crystal panel 10 side. .

Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the second direction D <b> 2 is absorbed by the polarizing plate 32.
The light whose polarization direction is transmitted through the polarizing plate 42 of the liquid crystal panel 40 passes through the optical sheet 36 and enters the polarization conversion element 34. The light incident on the polarization conversion element 34 is emitted with the polarization direction of the second direction D2 without changing the phase. The light emitted from the polarization conversion element 34 is absorbed by the polarizing plate 32.

  As described above, when the active mirror 30 is in the reflective state, light incident from the back side (the liquid crystal panel 40 side) of the active mirror 30 does not pass through the active mirror 30. Therefore, it is not possible to transmit what is on the back side from the scattering-type liquid crystal panel 10 side. Further, since part of the light incident on the active mirror 30 from the scattering liquid crystal panel 10 side is returned to the scattering liquid crystal panel 10 side, a reflective display device that illuminates the scattering liquid crystal panel 10 using external light. Can be used as

  FIG. 2 shows a configuration example when the active mirror 30 is in the transmissive state. When the active mirror 30 is set in the transmissive state, it is possible to produce a transparent effect in which the liquid crystal panel 40 disposed on the back side of the scattering type liquid crystal panel 10 can be seen through. When the active mirror 30 is in the transmissive state, light that passes through the polarizing plate 42 passes through the active mirror 30.

  FIG. 4 shows a configuration example of the active mirror 30 in the transmissive state. When the active mirror 30 is in the transmissive state, no voltage is applied to the TN mode liquid crystal. Accordingly, the polarization direction of the polarized light transmitted through the polarization conversion element 34 is converted into a predetermined direction.

  Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the first direction D <b> 1 passes through the polarizing plate 32 and enters the polarization conversion element 34. The light incident on the polarization conversion element 34 changes its phase, and the light whose polarization direction is the second direction D2 is emitted. The light emitted from the polarization conversion element 34 passes through the optical sheet 36 and is emitted to the back side of the active mirror 30.

  Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the second direction D <b> 2 is absorbed by the polarizing plate 32.

  The light whose polarization direction is transmitted through the polarizing plate 42 of the liquid crystal panel 40 passes through the optical sheet 36 and enters the polarization conversion element 34. The light incident on the polarization conversion element 34 has its polarization direction converted, and light whose polarization direction is the first direction D1 is emitted. The light emitted from the polarization conversion element 34 passes through the polarizing plate 32 and is emitted to the scattering type liquid crystal panel 10 side.

  When the active mirror 30 is in the transmissive state as described above, light incident from the back side (liquid crystal panel 40 side) of the active mirror 30 is transmitted through the active mirror 30, so that the scattering liquid crystal panel 10 side to the back side You can see through what is in.

  Further, the active mirror 30 has the above-described effect only with respect to linearly polarized light input. Therefore, light must enter the active mirror 30 through the polarizing plate, and the brightness becomes half or less. However, when the liquid crystal panel 40 having the polarizing plate 42 is disposed on the back side of the active mirror 30, it is not necessary to further dispose the polarizing plate 42 on the back side of the active mirror 30, and the display becomes dark. Can be suppressed.

  When the liquid crystal panel 40 is arranged on the back side of the active mirror 30, the active mirror 30 is arranged according to the polarization direction of the light emitted from the polarizing plate 42 of the liquid crystal panel 40. That is, the active mirror 30 and the liquid crystal panel 40 are aligned so that the polarization direction of the light transmitted through the optical sheet 36 matches the polarization direction of the light transmitted through the polarizing plate 42.

  As described above, according to the liquid crystal device according to the present embodiment, whether the liquid crystal panel 40 (LCD) is further disposed on the back surface of the scattering type liquid crystal panel 10 or whether the mirror is disposed on the back surface of the scattering type liquid crystal panel 10. Can be switched.

  When no voltage is applied to the polarization conversion element 34, an image displayed on the liquid crystal panel 40 can be viewed through the scattering type liquid crystal panel 10. Although the liquid crystal panel 40 is viewed through the scattering-type liquid crystal panel 10, since the transmittance of the scattering-type liquid crystal panel 10 is 80% or more, it can be used without a sense of incongruity. In addition, a cloudy display can be superimposed on the image displayed on the liquid crystal panel 40.

  Further, when a voltage is applied to the polarization conversion element 34, it is possible to perform display with good contrast of the scattering type liquid crystal panel 10 in which the active mirror 30 operates as a mirror. At this time, since the active mirror 30 absorbs light whose polarization direction is the second direction D2, the active mirror 30 absorbs about 50% and reflects the rest. That is, the situation is intermediate between the case where a black absorption band is arranged on the back side of the scattering-type liquid crystal panel 10 and the case where a mirror that reflects 100% of light is arranged.

  As described above, according to the liquid crystal device according to the present embodiment, it is possible to provide a liquid crystal device capable of realizing good display characteristics and performing multilayer display.

  Next, a liquid crystal device according to a second embodiment will be described below with reference to the drawings. In the following description, the same components as those of the liquid crystal device according to the first embodiment described above are denoted by the same reference numerals and description thereof is omitted. In the liquid crystal device according to the present embodiment, the configuration of the active mirror 30 is different from that of the first embodiment.

  FIG. 5 shows a configuration example when the active mirror 30 is in the reflecting state. In this example, a liquid crystal panel 40 and a backlight 50 are further arranged on the back side of the active mirror 30.

The liquid crystal panel 40 includes a polarizing plate 42 disposed to face the active mirror 30. The polarizing plate 42 is disposed so that the polarization direction transmits light in the second direction D2 and the polarization direction absorbs light in the first direction D1. When the active mirror 30 is in the reflecting state, the light that passes through the polarizing plate 42 is reflected by the active mirror 30.
The active mirror 30 includes an optical sheet 36 facing the illumination device 20, and a polarization conversion element 34 disposed between the optical sheet 36 and the liquid crystal panel 40.

Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the first direction D <b> 1 passes through the optical sheet 36 and enters the polarization conversion element 34. The light incident on the polarization conversion element 34 is emitted to the liquid crystal panel 40 side without changing its phase. The emitted light whose polarization direction is the first direction D1 is absorbed by the polarizing plate 42 of the liquid crystal panel 40.
Of the light that passes through the scattering liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the second direction D <b> 2 is reflected by the optical sheet 36 toward the scattering liquid crystal panel 10.

  The polarizing plate 42 of the liquid crystal panel 40 transmits the light whose polarization direction is the second direction D2 and emits it to the polarization conversion element 34 side. The light incident on the polarization conversion element 34 is emitted toward the optical sheet 36 without changing the phase. The light whose polarization direction is emitted from the polarization conversion element 34 is the second direction D2 is reflected by the optical sheet 36 toward the polarization conversion element 34 side.

  As described above, when the active mirror 30 is in the reflective state, light incident from the back side (the liquid crystal panel 40 side) of the active mirror 30 does not pass through the active mirror 30. Therefore, it is not possible to transmit what is on the back side from the scattering-type liquid crystal panel 10 side. In addition, since a part of the light incident on the active mirror 30 from the scattering liquid crystal panel 10 side is returned to the scattering liquid crystal panel 10 side, a reflective liquid crystal device that illuminates the scattering liquid crystal panel 10 using external light. Can be used as When the active mirror 30 is in the reflective state, the contrast between the scattering state and the transmission state of the scattering-type liquid crystal panel 10 is good.

  FIG. 6 shows a configuration example when the active mirror 30 is in the transmissive state. When the active mirror 30 is in the transmissive state, light that passes through the polarizing plate 42 passes through the active mirror 30.

  Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the first direction D <b> 1 passes through the optical sheet 36 and enters the polarization conversion element 34. The light incident on the polarization conversion element 34 changes its phase, and the light whose polarization direction is the second direction D2 is emitted. The light emitted from the polarization conversion element 34 is emitted to the back side of the active mirror 30.

  Of the light that passes through the scattering-type liquid crystal panel 10 and enters the active mirror 30, the light whose polarization direction is the second direction D <b> 2 is reflected by the optical sheet 36 toward the scattering-type liquid crystal panel 10.

  When light having a polarization direction of the second direction D2 transmitted through the polarizing plate 42 of the liquid crystal panel 40 enters the polarization conversion element 34, the phase is changed and light having the polarization direction of the first direction D1 is emitted. The light emitted from the polarization conversion element 34 passes through the optical sheet 36 and is emitted to the scattering type liquid crystal panel 10 side.

  When the active mirror 30 is in the transmissive state as described above, light incident from the back side (liquid crystal panel 40 side) of the active mirror 30 is transmitted through the active mirror 30, so that the scattering liquid crystal panel 10 side to the back side You can see through what is in.

  Further, the active mirror 30 has the above-described effect only with respect to linearly polarized light input. When the liquid crystal panel 40 is disposed on the back side of the active mirror 30, the active mirror 30 is disposed in accordance with the polarization direction of light emitted from the polarizing plate 42 of the liquid crystal panel 40. In the present embodiment, the active mirror 30 and the liquid crystal panel 40 are aligned so that the polarization direction of the light transmitted through the optical sheet 36 and the polarization direction of the light transmitted through the polarizing plate 42 are different (rotated by 90 degrees). To do.

  That is, according to the liquid crystal device according to the present embodiment, it is possible to provide a liquid crystal device capable of realizing a good display characteristic and performing multi-layer display.

  In this embodiment, a TN liquid crystal panel as a polarization conversion element is disposed on the back side of the optical sheet 36, and a polarizing plate 42 of the liquid crystal panel 40 is disposed on the back side. Therefore, since the number of polarizing plates is smaller than that in the first embodiment, the transmittance can be increased.

  On the other hand, when the optical sheet 36 is disposed so as to face the back side of the scattering type liquid crystal panel 10, even when the active mirror 30 is in the transmission state, a part of the light incident from the scattering type liquid crystal panel 10 side is the optical sheet 36. Reflected. Therefore, when the active mirror 30 is in the transmissive state, the reflected light may be visually recognized when viewing the image displayed on the liquid crystal panel 40 on the back side. In addition, when the active mirror 30 is in a reflective state, the display may be slightly purple.

  Therefore, it is desirable to adopt the configuration of the liquid crystal device according to the present embodiment when emphasizing brightness, and adopt the configuration of the display device according to the first embodiment when emphasizing display quality such as contrast.

The above-described embodiment is characterized by combining the scattering type liquid crystal and the active mirror, and as described above, it is not essential to stack the liquid crystal display in a multilayer type. For example, an active mirror may be combined with a scattering type liquid crystal, and a device that performs display with the scattering type liquid crystal while switching between a state where the other side of the liquid crystal panel can be seen through and a reflection state where the other side cannot be seen through may be used.
In that case, the device has only the configuration shown in FIGS. 3, 4, 5, and 6. At this time, the polarizing plate 42 is added below the active mirror 30 in FIGS.

  In the above embodiment, the TN mode liquid crystal panel is used as the polarization conversion element 34, but any means capable of converting the polarization direction may be used. For example, a liquid crystal panel of another mode may be used.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof .
Hereinafter, the invention described in the scope of claims of the present application will be appended.
[1] A first liquid crystal panel comprising a pair of substrates and a scattering type liquid crystal sandwiched between the pair of substrates;
The first liquid crystal panel is disposed on the back side of the first liquid crystal panel. A first state in which the polarization direction incident from the back side transmits linearly polarized light in the first direction, and a polarization direction incident from the back side converts linearly polarized light in the first direction. An active mirror capable of switching between a second state of absorption or reflection;
A second liquid crystal panel disposed on the back side opposite to the active mirror,
The active mirror is disposed opposite to the first liquid crystal panel and absorbs linearly polarized light in a second direction whose polarization direction is orthogonal to the first direction, and linearly polarized light in which the polarization direction is the first direction. An optical sheet that reflects and transmits linearly polarized light whose polarization direction is the second direction, and a polarization conversion element that is disposed between the polarizing plate and the optical sheet and that can convert the polarization direction of incident light. LCD device.
[2] The liquid crystal device according to [1], wherein the second liquid crystal panel includes a polarizing plate that transmits linearly polarized light whose polarization direction is the second direction.
[3] A first liquid crystal panel comprising a pair of substrates and a scattering type liquid crystal sandwiched between the pair of substrates;
The first liquid crystal panel is disposed on the back side of the first liquid crystal panel. A first state in which the polarization direction incident from the back side transmits linearly polarized light in the first direction, and a polarization direction incident from the back side converts linearly polarized light in the first direction. An active mirror capable of switching between a second state of absorption or reflection;
A second liquid crystal panel disposed on the back side opposite to the active mirror,
The active mirror is disposed between a polarization conversion element capable of converting a polarization direction of incident light, and the first liquid crystal panel and the polarization conversion element, and a polarization direction of the second direction orthogonal to the first direction. And an optical sheet that reflects linearly polarized light and transmits linearly polarized light whose polarization direction is the first direction.
[4] The liquid crystal device according to [3], wherein the second liquid crystal panel includes a polarizing plate that transmits linearly polarized light whose polarization direction is the second direction.

  LG ... light guide, 10 ... scattering liquid crystal panel (first liquid crystal panel), 20 ... illuminating device, 22 ... light source, 30 ... active mirror, 32 ... polarizing plate, 34 ... polarization conversion element, 36 ... optical sheet, 40 ... liquid crystal panel (second liquid crystal panel), 42 ... polarizing plate, 50 ... backlight.

Claims (4)

A first liquid crystal panel comprising: a pair of substrates; and a scattering-type liquid crystal sandwiched between the pair of substrates;
An active mirror disposed on the back side of the first liquid crystal panel so as to face the first liquid crystal panel;
A first polarizing plate disposed opposite to the active mirror on the back side thereof and transmitting linearly polarized light whose polarization direction is the first direction;
The active mirror is disposed on the side facing the first liquid crystal panel, and transmits a second polarizing plate that absorbs linearly polarized light whose polarization direction is the first direction, and transmits linearly polarized light whose polarization direction is the first direction. An optical sheet that reflects linearly polarized light in a second direction whose polarization direction is orthogonal to the first direction, and polarized light that is disposed between the second polarizing plate and the optical sheet and that can change the polarization direction of incident light. comprising a conversion element, a and the active mirror has a first state in which the front Symbol polarization direction incident from the first polarizer side is transmitted through the linearly polarized light of the first direction, from the first polarizer side A liquid crystal device capable of switching between a second state in which an incident polarization direction absorbs or reflects linearly polarized light in the first direction. The polarization conversion element has a pair of electrodes arranged opposite to each other,
The liquid crystal device according to claim 1, wherein the pair of electrodes is divided into a plurality of regions, and an applied voltage is controlled for each region. A first liquid crystal panel comprising: a pair of substrates; and a scattering-type liquid crystal sandwiched between the pair of substrates;
An active mirror disposed on the back side of the first liquid crystal panel so as to face the first liquid crystal panel;
A polarizing plate disposed opposite to the active mirror on the back side thereof and transmitting linearly polarized light whose polarization direction is the first direction,
The active mirror is disposed between a polarization conversion element capable of converting a polarization direction of incident light and the first liquid crystal panel and the polarization conversion element, and reflects linearly polarized light having a polarization direction of the first direction to be polarized. an optical sheet that transmits the second linearly polarized light in the direction which directions are perpendicular to the first direction, includes a, and the active mirror, a pre-Symbol linearly polarized light the polarization direction of the first direction incident from the polarizing plate side A liquid crystal device capable of switching between a first state in which light is transmitted and a second state in which a polarization direction incident from the polarizing plate side absorbs or reflects linearly polarized light in the first direction. The polarization conversion element has a pair of electrodes arranged opposite to each other,
The liquid crystal device according to claim 3, wherein the pair of electrodes is divided into a plurality of regions, and the applied voltage is controlled for each of the regions.

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