JP2000284266A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scattering type liquid crystal display device that a bright display by scattering of incident light is enough enhanced and a display with good contrast can be obtd. SOLUTION: A p-s wave separation reflector 20 is disposed on the back face side of a scattering/transmission type liquid crystal cell 10. The reflector 20 has a reflection axis and transmission axis perpendicular to each other, reflects s-wave light having the polarized light component along the reflection axis and transmits p-wave light having the polarized light component along the transmission axis. A light-absorbing member 21 is disposed on the back face side of the p-s wave separation reflector 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a scattering type liquid crystal display device for controlling and displaying light scattering.

[0002]

2. Description of the Related Art As a liquid crystal display device, there is a scattering type device which controls display of light by scattering. FIG. 8 is a cross-sectional view of a conventional scattering type liquid crystal display device. This liquid crystal display device includes a scattering / transmission type liquid crystal cell 1 and a light absorbing film 9 arranged on the back side of the liquid crystal cell 1. I have.

The scattering / transmission type liquid crystal cell 1 scatters and transmits incident light, and has a pair of transparent substrates 2 and 3 on the front side and the back side joined via a frame-shaped sealing material (not shown). And transparent electrodes 4 and 5 provided on the inner surfaces of these substrates 2 and 3, respectively,
3 and a liquid crystal layer 6 that scatters and transmits incident light according to a change in the alignment state of liquid crystal molecules due to an electric field applied between the electrodes 4 and 5.

The scattering / transmission type liquid crystal cell 1 shown in FIG.
Is a polymer dispersed type, and the liquid crystal layer 6 is a liquid crystal / polymer composite layer. This liquid crystal / polymer composite layer is obtained by dispersing a nematic liquid crystal 8 having a positive dielectric anisotropy in a transparent polymer layer 7, and polymerized to have a sponge-like cross section. The liquid crystal 8 is confined in each of the gaps 7.

The liquid crystal cell 1 is of an active matrix type, and the electrodes 5 provided on the inner surface of the rear substrate 3 are a plurality of pixel electrodes arranged in a matrix. Each of the pixel electrodes 5 is provided with a plurality of TFTs (not shown) provided on the inner surface of the rear substrate 3 so as to correspond to the respective pixel electrodes 5.
The plurality of TFTs are connected to a gate line and a data line (not shown) wired on the inner surface of the rear substrate 3.

On the other hand, the electrode 4 provided on the inner surface of the front-side substrate 2 is a single-film counter electrode facing all of the plurality of pixel electrodes 5. Regions 5 and 5 are pixel regions.

The light absorbing film 9 is of a black type that absorbs most of the incident light.
The liquid crystal cell 1 is disposed on the back side so as to face almost the entire surface of the liquid crystal cell 1. The light absorbing film 9 is shown in FIG.
Is separated from the rear surface of the liquid crystal cell 1, but the light absorbing film 9 is provided close to or in close contact with the outer surface of the rear substrate 3 of the liquid crystal cell 1.

This scattering type liquid crystal display device utilizes external light (natural light, indoor illumination light, etc.) which is light in the environment of use, and uses the scattering / transmission type liquid crystal cell (polymer dispersion type liquid crystal cell) 1 to form a liquid crystal. The display is performed by controlling the scattering of light by the layer 6. The liquid crystal layer 6 scatters incident light to obtain a bright display, and transmits the incident light through the liquid crystal layer 6 to form a light absorbing film on the back side. A dark display is obtained by absorption at 9.

That is, the molecules 8a of the liquid crystal 8 of the liquid crystal / polymer composite layer which is the liquid crystal layer 6 of the liquid crystal cell 1
In the no-electric-field state in which no voltage is applied between the five points, they are oriented in random directions as shown in FIG.

In this electric field-free state, light incident on the liquid crystal cell 1 from the front thereof is scattered by the scattering action of the liquid crystal layer 6 as shown by the solid arrow in the figure, and of the scattered light, The light directed toward the front is emitted forward, and the display in that area becomes bright. Note that, of the light scattered by the liquid crystal layer 6, the light going to the back side is the liquid crystal cell 1.
And is absorbed by the light absorbing film 9.

Further, between the electrodes 4 and 5 of the liquid crystal cell 1,
When a voltage having a predetermined value is applied, the electric field causes the liquid crystal molecules 8a of the liquid crystal layer 6 to be uniformly arranged so as to be substantially perpendicular to the surfaces of the substrates 2 and 3.

At this time, the light incident on the liquid crystal cell 1 from the front thereof is transmitted through the liquid crystal cell 1 almost without being scattered by the liquid crystal layer 6, as shown by the broken arrow in the figure. Is absorbed by the light absorbing film 9, and the display in that region becomes a dark display.

As described above, the above-mentioned scattering type liquid crystal display device has:
The scattering type liquid crystal display device does not require a polarizing plate for controlling light transmission unlike a TN (twisted nematic) type liquid crystal display device because it controls display of light scattering. A bright display can be obtained by using external light.

The scattering / transmission type liquid crystal cell 1 shown in FIG.
Is a polymer-dispersed type, but the scattering / transmission type liquid crystal cell has a liquid crystal layer composed of a cholesteric liquid crystal having a positive dielectric anisotropy or a mixed liquid crystal of a cholesteric liquid crystal and a nematic liquid crystal between a pair of transparent substrates. There is also a phase transition type (also called a phase transition type) provided.

This phase transition type liquid crystal cell scatters and transmits light by utilizing the phase transition of the liquid crystal, and is a non-electric field state in which no voltage is applied between electrodes provided on the inner surfaces of a pair of substrates. In the above, the liquid crystal exhibits a cholesteric liquid crystal phase and scatters incident light. In addition, when a predetermined voltage is applied between the electrodes, the liquid crystal transitions to a nematic liquid crystal phase in a homeotropic arrangement, and transmits incident light with almost no scattering.

A scattering type liquid crystal display device using the above-mentioned phase change type liquid crystal cell also has a structure in which a light absorbing film is disposed on the back side of the above liquid crystal cell. The light is scattered to obtain a bright display, and the incident light is transmitted through the liquid crystal cell and absorbed by the light absorbing film to obtain a dark display.

[0017]

However, in the conventional scattering type liquid crystal display device, the light is incident on the scattering / transmission type liquid crystal cell (polymer dispersion type or phase transition type liquid crystal cell) from the front surface thereof and is scattered by the liquid crystal layer. Of the scattered light, only the light directed toward the front of the liquid crystal cell is emitted forward, and the scattered light directed toward the back of the liquid crystal layer is emitted to the back of the liquid crystal cell and absorbed by the light absorbing film. Insufficient brightness and poor contrast.

An object of the present invention is to provide a scattering-type liquid crystal display device capable of sufficiently brightening a bright display by scattering of incident light and obtaining a display with good contrast.

[0019]

According to a liquid crystal display device of the present invention, electrodes are provided on inner surfaces of a pair of substrates facing each other, and liquid crystal molecules are generated between the pair of substrates by an electric field applied between the electrodes. Has a reflection axis and a transmission axis in directions orthogonal to each other on the back side of a scattering / transmission type liquid crystal cell provided with a liquid crystal layer that scatters and transmits incident light in accordance with a change in the alignment state of the liquid crystal. The s-wave light of the polarization component along the reflection axis of the light incident on the cell and emitted to the back is reflected toward the liquid crystal cell, and the p-wave light of the polarization component along the transmission axis is reflected on the back side. A p-s wave separating / reflecting plate to be transmitted is arranged, and a light absorbing member is provided on the back side of the p-s wave separating / reflecting plate.

This liquid crystal display device uses external light, which is light in the environment in which it is used, to control the scattering of light by the liquid crystal layer of the scattering / transmission type liquid crystal cell for displaying. When the liquid crystal molecules in the liquid crystal layer are in an alignment state that scatters incident light, external light incident on the liquid crystal cell from the front is scattered by the liquid crystal layer.

At this time, of the scattered light scattered by the liquid crystal layer, light heading toward the front surface of the liquid crystal cell is emitted forward, and at the same time, p light of the scattered light emitted toward the back surface of the liquid crystal cell is emitted. -The s-wave light of the polarization component along the reflection axis of the s-wave separation reflector is reflected by the p-s wave separation reflector, and the reflected light is again incident on the liquid crystal cell from the back surface, and is again reflected by the liquid crystal layer. Scattered and emitted forward,
The display of the area becomes a bright display.

Incidentally, of the scattered light emitted to the back of the liquid crystal cell, p-wave light of a polarization component along the transmission axis of the p-s wave separation / reflection plate transmits through the p-s wave separation / reflection plate. And is absorbed by the light absorbing member.

That is, in this liquid crystal display device, a bright display due to the scattering of the incident light is transmitted from the front of the scattered light scattered by the liquid crystal layer of the liquid crystal cell. The scattered light emitted to the rear side is reflected by the p-s wave separating / reflecting plate, is scattered again by the liquid crystal layer, and is emitted forward to display the image. Brightness is enough.

When the liquid crystal molecules of the liquid crystal layer of the liquid crystal cell are oriented so as to transmit the incident light, the light incident on the liquid crystal cell from the front transmits through the liquid crystal layer with almost no scattering. Out of the back side, and of the light, the p-wave light of the polarization component along the transmission axis of the p-s wave separating / reflecting plate transmits through the p-s wave separating / reflecting plate and is absorbed by the light absorbing member. And the display of the area becomes dark.

However, even during the dark display, the s-wave light of the polarization component along the reflection axis of the p-s wave separation reflector of the light emitted to the back of the liquid crystal cell is converted to the p-s wave. Since the reflected light is reflected by the separation reflection plate and the reflected light is transmitted through the liquid crystal cell again and emitted forward, the dark display is a light emitted to the back surface of the liquid crystal cell without the ps wave separation reflection plate. Is brighter than when most of the light is absorbed by the light absorbing member.

However, the display of the liquid crystal display device is usually observed from the front direction (direction near the normal to the front surface of the device), and external light is oblique to the front direction which is the display observation direction. Incident mainly from the direction inclined to.

The p-s wave separating / reflecting plate reflects most of the s-wave light of the polarization component along the reflection axis at the same reflection angle as its incident angle. The emission direction of the light reflected by the -s wave separation reflector is obliquely forward with respect to the front direction, that is, a direction that is hardly visible to a display observer, and therefore, a dark display observed from the front direction is It is dark enough.

Therefore, according to the liquid crystal display device of the present invention, bright display due to scattering of incident light is made sufficiently bright, and furthermore, a difference in brightness between the bright display and the dark display is sufficiently large and a display with good contrast is obtained. Can be obtained.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, a liquid crystal display device of the present invention has a reflection axis and a transmission axis orthogonal to each other on the back side of a scattering / transmission type liquid crystal cell, and a polarized light along the reflection axis. A p-s-wave separating / reflecting plate that reflects the s-wave light of the component and transmits the p-wave of the polarized component along the transmission axis is disposed, and a light absorbing member is provided on the back side of the p-s-wave separating / reflecting plate. Thus, bright display due to scattering of incident light is made sufficiently bright, and a display with good contrast can be obtained.

In the liquid crystal display device of the present invention, the p
The light absorbing member provided on the back side of the -s wave separation / reflection plate is preferably a black absorption film that absorbs most of the incident light, and by using this black absorption film, the p-s wave separation / reflection plate can be used. It is possible to substantially completely prevent the light transmitted through the light from being reflected and emitted forward, thereby making the dark display darker.

The light absorbing member may be a polarizing plate that absorbs light of a polarization component along an absorption axis and transmits light of a polarization component along a transmission axis. In this case, the polarizing plate may include: By arranging the transmission axis in a direction intersecting the transmission axis of the p-s wave separation / reflection plate,
The light transmitted through the -s-wave separation reflection plate can be absorbed by the polarizing plate.

As described above, when a polarizing plate is used as the light absorbing member, a light reflecting member may be provided on the back side of the polarizing plate. With such a configuration, the bright display can be made brighter. can do.

That is, since the polarization degree of the p-s wave separating / reflecting plate is not so high, the transmission axis of the polarizing plate is
-Even though the light intersects the transmission axis of the s-wave separation reflector, the light transmitted through the p-s wave separation reflector and incident on the polarizing plate (along the transmission axis of the p-s wave separation reflector) Polarization component p
Wave light) transmits to the back side of the polarizing plate, but a light reflecting member is provided on the back side of the polarizing plate, passes through the p-s wave separating / reflecting plate, and further passes through the polarizing plate. If the transmitted light is positively reflected by the light reflecting member, the light reflected by the light reflecting member is also emitted forward.

For this reason, a bright display is formed by the light emitted forward in the light scattered by the liquid crystal layer of the liquid crystal cell and the light reflected by the p-s wave separation reflector and scattered again by the liquid crystal layer to produce a bright display. , And the light reflected by the light reflecting member, scattered again by the liquid crystal layer, and emitted forward, thereby displaying the bright display more brightly.

In this case, the dark display becomes somewhat bright, but the external light mainly enters from a direction oblique to the front direction which is the display observation direction as described above. Since the light is reflected obliquely forward with respect to the front direction by the p-s wave separation reflection plate and the light reflection member, the dark display observed from the front direction is sufficiently dark. A display having a sufficiently large difference in brightness and a high contrast can be obtained.

Further, in the liquid crystal display device according to the present invention, between the liquid crystal cell and the ps-wave separation reflector or on the front side of the liquid crystal cell, a specific angle range with respect to the vertical direction is set. It is desirable to dispose an anisotropic scattering plate that emits light incident at an incident angle without scattering, and scatters and emits light incident at an incident angle larger than the incident angle. In addition to emitting more scattered light in the front direction, which is the observation direction of, the bright display is further brightened, and the glare of the dark display due to the reflection of the p-wave light by the p-s wave separating reflector during the dark display is suppressed. can do.

Further, the liquid crystal cell has a plurality of pixel regions in which electrodes provided on inner surfaces of a pair of substrates are opposed to each other, and one of the pair of substrates has:
A plurality of color filters respectively corresponding to the plurality of pixel regions may be provided. By using such a liquid crystal cell, a bright and high-contrast color image can be displayed.

[0038]

FIG. 1 is a sectional view of a part of a liquid crystal display device according to a first embodiment of the present invention. The liquid crystal display device of this embodiment includes a scattering / transmission type liquid crystal cell 10 and a liquid crystal cell 1 of the present invention.
And a p-s wave separating / reflecting plate 20 disposed on the back side of the P.S.

The scattering / transmission type liquid crystal cell 10 scatters and transmits incident light, and a pair of front and rear transparent substrates 11 and 12 joined via a frame-shaped sealing material (not shown). Transparent electrodes 1 on the inner surface of
3 and 14 are provided, and between the pair of substrates 11 and 12,
A liquid crystal layer 15 that scatters and transmits incident light according to a change in the alignment state of liquid crystal molecules due to an electric field applied between the electrodes 13 and 14 is provided.

The scattering / transmission type liquid crystal cell 10 used in this embodiment is of a polymer dispersion type, and its liquid crystal layer 1
5 is a liquid crystal / polymer composite layer. This liquid crystal / polymer composite layer is obtained by dispersing a nematic liquid crystal 17 having a positive dielectric anisotropy in a transparent polymer layer 16 and polymerized to have a sponge-like cross section. The liquid crystal 17 is confined in each of the gaps 16.

The liquid crystal cell 10 is of the active matrix type, and the electrodes 14 provided on the inner surface of the rear substrate 12 are a plurality of pixel electrodes arranged in a matrix. These pixel electrodes 14 are respectively
The TFTs are connected to a plurality of TFTs (thin film transistors) (not shown) provided on the inner surface of the rear substrate 12 so as to correspond to the respective pixel electrodes 14.
It is connected to a gate line and a data line (not shown) wired on the inner surface of the rear substrate 12.

On the other hand, the electrode 13 provided on the inner surface of the front substrate 11 is a single-film-shaped counter electrode which faces all of the plurality of pixel electrodes 14. The areas facing each other are pixel areas.

Next, the p-s wave separating / reflecting plate 20 disposed on the back side of the scattering / transmission type liquid crystal cell 10 will be described.

FIG. 2 is a perspective view of the p-s wave separation / reflection plate 20, which has a reflection axis 20s and a transmission axis 20p in directions substantially orthogonal to each other. It has a characteristic of reflecting s-wave light of a polarization component along the reflection axis 20s of light and transmitting p-wave light of a polarization component along the transmission axis 20p.

That is, as shown in FIG.
When light containing both the s-wave light S of the polarization component along the reflection axis 20s and the p-wave light P of the polarization component along the transmission axis 20p is made incident on the s-wave separating / reflecting plate 20, the incident light becomes Of the s-wave light S along the reflection axis 20s is p-s
The p-wave light P reflected by the wave separating / reflecting plate 20 and along the transmission axis 20p passes through the p-s wave separating / reflecting plate 20.

FIG. 2 shows a p-s wave separating / reflecting plate 20.
FIG. 1 shows an example in which light is incident from one surface, but the p-s wave separating / reflecting plate 20 exhibits the same characteristics with respect to incident light from the other surface.

The p-s wave separating / reflecting plate 20 is a non-colored sheet whose reflection and transmission characteristics have no wavelength dependence, and the reflected light is specular reflected light.

The p-s wave separating / reflecting plate 20 comprises:
With the reflection axis 20s and the transmission axis 20p directed in arbitrary directions, the liquid crystal cell 10
Are arranged so as to face almost the entire surface of the.

The absorption film 21 is of a black type that absorbs most of incident light.
The p-s wave separating / reflecting plate 20 is disposed on the back side of the p-s wave separating / reflecting plate 20 so as to face almost the entire surface of the p-s wave separating / reflecting plate 20.

In FIG. 1, the liquid crystal cell 10, the p-s-wave separating / reflecting plate 20, and the absorbing film 21 are separated from each other. Provided close to or in close contact with the outer surface of the side substrate 12,
The absorption film 21 is provided close to or in close contact with the rear surface of the p-s wave separation / reflection plate 20.

In this liquid crystal display device, light is scattered by the liquid crystal layer 15 of the scattering / transmission type liquid crystal cell (the polymer dispersion type liquid crystal cell in this embodiment) 10 using external light which is light of the use environment. The liquid crystal 1 of the liquid crystal / polymer composite layer, which is the liquid crystal layer 15 of the liquid crystal cell 10, is displayed.
In a no-electric-field state where no voltage is applied between the electrodes 13 and 14, the molecules 17 a of 7 are in an alignment state oriented in a random direction, that is, an alignment state in which incident light is scattered, as shown in FIG. .

As described above, when the liquid crystal molecules 17a of the liquid crystal layer 15 of the liquid crystal cell 10 are in an alignment state that scatters incident light, light incident on the liquid crystal cell 10 from the front is as shown by a solid line arrow in FIG. Is scattered by the scattering action of the liquid crystal layer 15.

At this time, of the scattered light scattered by the liquid crystal layer 15, light directed toward the front of the liquid crystal cell 10 is emitted forward, and of the scattered light emitted to the back of the liquid crystal cell 10, The p-s wave separating reflector 20
The s-wave light S of the polarization component along the reflection axis 20s of the
The reflected light is reflected by the s-wave separating / reflecting plate 20, and the reflected light is again incident on the liquid crystal cell 10 from the back thereof, is scattered again by the liquid crystal layer 15 and is emitted forward, and the display of the area becomes a bright display.

In the scattered light emitted to the back of the liquid crystal cell 10, the transmission axis 2 of the p-s wave
The p-wave light P of the polarization component along 0p is transmitted through the p-s wave separating / reflecting plate 20, and is absorbed by the absorbing film 21.

That is, in this liquid crystal display device, a bright display due to scattering of incident light is incident from the front and the liquid crystal cell 10 is illuminated.
Of the scattered light scattered by the liquid crystal layer 15 and the scattered light emitted to the back side of the liquid crystal cell 10 are reflected by the p-s wave separating / reflecting plate 20, and The display is performed by both the light scattered again by the layer 15 and the light emitted forward, so that the brightness of the bright display is sufficient.

The electrodes 13, 14 of the liquid crystal cell 10
When a voltage of a predetermined value is applied during this time, the electric field causes the liquid crystal molecules 17a of the liquid crystal layer 15 to be uniformly arranged so as to be substantially perpendicular to the surfaces of the substrates 11 and 12, and the alignment for transmitting the incident light. State.

When the liquid crystal molecules 17a of the liquid crystal layer 15 of the liquid crystal cell 10 are oriented so as to transmit the incident light, the light incident on the liquid crystal cell 10 from the front is indicated by a broken arrow in FIG. Is transmitted through the liquid crystal layer 15 with little scattering and exits to the back side of the liquid crystal cell, and of the light, the p-wave light P of the polarization component along the transmission axis 20p of the p-s wave separation / reflection plate 20 is transmitted. Is the p-s wave separation reflector 20
And is absorbed by the absorbing film 21, and the display in that region becomes a dark display.

However, even during the dark display, the s-wave light S of the polarization component along the reflection axis of the p-s-wave separating / reflecting plate 20 of the light emitted to the back of the liquid crystal cell 10 is reflected by the p-wave. Since the reflected light is reflected by the −s-wave separating reflector 20 and the reflected light is transmitted through the liquid crystal cell 10 again and emitted forward, the dark display can be performed without the p-s wave separating / reflecting plate 20. Is brighter than when the light emitted to the back surface of the light-emitting element is absorbed by the absorbing film 21.

However, the display of the liquid crystal display device is usually observed from the front direction (direction near the normal to the front surface of the device), and external light is oblique to the front direction which is the display observation direction. Incident mainly from the direction inclined to.

In other words, a display device that makes use of external light for display uses a direction inclined obliquely to the upper edge of the screen with respect to the front direction, which is the viewing direction of display, so that bright external light is obtained. Usually, the liquid crystal display device of this embodiment is used in the same manner.

The p-s wave separating / reflecting plate 20 comprises:
Since most of the s-wave light S of the polarization component along the reflection axis 22s is reflected at the same reflection angle as the incident angle, the light reflected by the p-s wave separation / reflection plate 20 during the dark display is used. The emission direction is obliquely forward with respect to the front direction,
That is, the direction is almost invisible to the display observer, so that the dark display observed from the front direction is sufficiently dark.

Further, in this embodiment, since the light absorbing member provided on the back side of the ps wave separating / reflecting plate 20 is a black absorbing film 21 for absorbing most of the incident light, the ps The light transmitted through the wave separation reflector 20 is almost completely prevented from being reflected and emitted forward, and the dark display can be made darker.

Therefore, according to this liquid crystal display device,
The bright display due to the scattering of incident light is made sufficiently bright, and
It is possible to obtain a high-contrast display with a sufficiently large difference in brightness between the bright display and the dark display.

When the display characteristics of the liquid crystal display device of the above embodiment and a comparison device in which the p-s wave separating / reflecting plate 20 is omitted from the liquid crystal display device are compared, it is found that these devices are centered on the normal line on the front surface thereof. When light is incident at an incident angle of 20 degrees with respect to the normal from the entire circumferential direction of the circumference, and the emitted light is measured from the front direction (the direction along the normal), the brightness of each device is determined. Light reflectance (ratio of outgoing light to incident light) R for display and dark display, and chromaticity x, y of outgoing light
And the contrast _CR are as follows.

The reflectance R is a value based on the reflectance of a single white reflector made of Al ₂ O ₃ (alumina), with the reflectance of the white reflector being 100%. The chromaticity of the emitted light is an x coordinate value and a y coordinate value on the CIE chromaticity diagram.

[Comparison device] Bright display Reflectance R = 5.7%, chromaticity x = 0.27, y =
0.27 Dark display Reflectivity R = 1.5%, chromaticity x = 0.28, y =
0.30 Contrast C _R = 3.9 [Example Device] Bright display Reflectivity R = 88.1%, chromaticity x = 0.32, y
= 0.33 Dark display Reflectivity R = 10.0%, chromaticity x = 0.30, y
= 0.32 Contrast C _R = 8.9 As described above, in the liquid crystal display device of the above embodiment, most of the light emitted to the rear surface of the liquid crystal cell 10 without the ps wave separation / reflection plate 20 is absorbed by the absorption film. Compared to the comparison device that absorbs light by 21, the reflectivity at the time of dark display is higher, so the dark level slightly rises, but the reflectivity at the time of bright display is much higher and higher than that of the comparison device. Contrast is obtained.

In the liquid crystal display device of the above embodiment, the chromaticity of the emitted light at the time of bright display and dark display is both CI
White (achromatic) point (x = 0.31, y on the E chromaticity diagram
= 0.32), so that a better black and white display can be obtained as compared with the comparison device.

In the first embodiment, the p-s
On the back side of the wave separating / reflecting plate 20, a black absorbing film 21 is provided as a light absorbing member. The light absorbing member absorbs light of a polarization component along the absorption axis and extends along the transmission axis. A polarizing plate that transmits the polarized light component may be used.

FIG. 3 is a cross-sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention. The liquid crystal display device of this embodiment includes a scattering / transmission type liquid crystal cell 10 and a liquid crystal cell 1 of this type. A ps-wave separating / reflecting plate 20 disposed on the back side, a polarizing plate 22 provided as a light absorbing member on the back side of the p-s-wave separating / reflecting plate 20, and a back side of the polarizing plate 22 The light reflecting member 23 is provided.

Since the scattering / transmission type liquid crystal cell 10 is of a polymer dispersion type, and the liquid crystal cell 10 and the p-s wave separating / reflecting plate 20 are the same as those of the first embodiment, Duplicate descriptions are given the same reference numerals in the drawings and are omitted.

In this embodiment, the polarizing plate 22 is
The transmission axis is set to the transmission axis 20 of the p-s wave separation reflection plate 20.
p (see FIG. 2).

The light reflecting member 23 disposed on the back side of the polarizing plate 22 is a specular reflecting film made of, for example, silver. The light reflecting member 23 is brought into close or close contact with the back surface of the polarizing plate 22. Is provided.

The liquid crystal display device of this embodiment has the p-s
The light absorbing member provided on the back side of the wave separation / reflection plate 20 is a polarizing plate 22 that absorbs light of a polarization component along an absorption axis and transmits light of a polarization component along a transmission axis.
Since the polarizing plate 22 is disposed with its transmission axis directed in a direction intersecting with the transmission axis 20p of the p-s wave separating / reflecting plate 20, the polarizing plate 22 transmits through the p-s wave separating / reflecting plate 20. Light (p-wave light of a polarization component along the transmission axis 20p of the p-s wave separation / reflection plate 20) can be absorbed by the polarizing plate 22.

The transmission axis of the polarizing plate 22 and the p-
The crossing angle of the s-wave separating / reflecting plate 20 with the transmission axis 20p may be set arbitrarily, but a preferable crossing angle is 90 degrees or an angle close thereto, and the transmission axis of the polarizing plate 22 is set to the p-s wave. By making the transmission axis 20p of the separation / reflection plate 20 substantially perpendicular to the transmission axis, the light transmitted through the ps wave separation / reflection plate 20 can be efficiently absorbed by the polarizing plate 22.

In this embodiment, the polarizing plate 22
Since the light reflecting member 23 is provided on the back side of the device, the bright display can be made brighter.

That is, since the polarization degree of the ps-wave separating / reflecting plate 20 is not so high, the transmission axis of the polarizing plate 22 intersects the transmission axis 20p of the p-s-wave separating / reflecting plate 20. However, the light transmitted through the p-s wave separation / reflection plate 20 and incident on the polarizing plate 22 (the p-s wave separation / reflection plate 2
A certain amount of light of the polarization component p-wave light P along the zero transmission axis 20p is transmitted to the back side of the polarizing plate 22 as shown by the arrow in FIG.

In this embodiment, the polarizing plate 22
The light reflecting member 23 is provided on the back side of the
The s-wave separating reflector 20 and the polarizing plate 22
Since the light transmitted through the light reflecting member 23 is positively reflected by the light reflecting member 23, the light reflected by the light reflecting member 23 is also emitted forward.

For this reason, according to this embodiment, a bright display is reflected by the light scattered by the liquid crystal layer 15 of the liquid crystal cell 10 and emitted forward, and reflected by the p-s wave separating / reflecting plate 20. The light is scattered again by the liquid crystal layer 15 and emitted forward, and the light is reflected by the light reflecting member 23 and is scattered again by the liquid crystal layer 15 and emitted forward, so that the bright display is made brighter. can do.

In this case, the dark display is also somewhat bright, but the external light mainly enters from the direction oblique to the front direction which is the display observation direction as described above. p-s wave separating reflector 20 and light reflecting member 2
Because it is reflected obliquely forward from the front direction by 3,
The dark display observed from the front direction is sufficiently dark, so that a display with high contrast in which the difference in brightness between the bright display and the dark display is sufficiently large can be obtained.

In the liquid crystal display device of this embodiment, the crossing angle between the transmission axis of the polarizing plate 22 and the transmission axis 20p of the ps-wave separation / reflection plate 20 is 90 degrees or an angle close thereto as described above. It is preferable that the light transmitted through the p-s wave separating / reflecting plate 20 be efficiently absorbed by the polarizing plate 22 so that the difference in brightness between the bright display and the dark display is set. And a display with good contrast can be obtained.

That is, a liquid crystal display device in which the polarizing plate 22 is disposed with its transmission axis parallel to the transmission axis 20p of the p-s wave separating / reflecting plate 20, and the polarizing plate 22 is positioned such that its transmission axis is the p-s Comparing the display characteristics of liquid crystal display devices arranged perpendicular to the transmission axis 20p of the s-wave separating / reflecting plate 20, these devices show the normal line from the entire circumferential direction centered on the normal line on the front surface thereof. When the light is incident at an incident angle of 20 degrees with respect to the light, and the emitted light is measured from the front direction (the direction along the normal), the reflectance of light at the time of bright display and dark display (with respect to the incident light) The ratio (R) of the emitted light, the chromaticities x and y of the emitted light, and the contrast _CR are as follows.

The reflectance R is a value based on the reflectance of a single white reflector made of Al ₂ O ₃ and the reflectance of the white reflector is set to 100%. Are the x coordinate value and the y coordinate value on the CIE chromaticity diagram.

[Parallel transmission axis of the polarizing plate and the ps wave separating reflector] Bright display Reflectance R = 146.9%, chromaticity x = 0.31,
y = 0.32 Dark display Reflectivity R = 82.3%, chromaticity x = 0.32
y = 0.34 Contrast C _R = 1.8 [Transmission axis perpendicular to polarizing plate and p-s wave separating reflector] Bright display Reflectance R = 88.4%, chromaticity x = 0.32, y
= 0.33 Dark display Reflectivity R = 11.2%, chromaticity x = 0.32, y
= 0.34 Contrast C _R = 7.9 As described above, the liquid crystal display device according to the present embodiment includes the polarizing plate 22.
When the crossing angle between the transmission axis of (1) and the transmission axis 20p of the p-s wave separating / reflecting plate 20 is 90 degrees (orthogonal), the contrast becomes highest and the crossing angle of the transmission axis is small (close to parallel). As a result, the contrast decreases.

Therefore, a desirable intersection angle between the transmission axis of the polarizing plate 22 and the transmission axis 20p of the ps-wave separating / reflecting plate 20 is 90 degrees or an angle close to 90 degrees. By setting the angle, a high contrast can be obtained.

The transmission axis of the polarizing plate 22 and the p-
The desired intersection angle of the s-wave separation / reflection plate 20 with the transmission axis 20p can be arbitrarily selected within a range of 90 degrees or less and greater than 0 degree. By selecting this intersection angle, bright display and dark display can be performed. Brightness and contrast can be set arbitrarily.

FIG. 4 is a cross-sectional view of a part of a liquid crystal display device according to a third embodiment of the present invention. The liquid crystal display device of this embodiment has a scattering / transmission type liquid crystal cell 10 and a liquid crystal cell 1 of this type. A p-s wave separating / reflecting plate 20 disposed on the back side; an anisotropic scattering plate 24 disposed between the liquid crystal cell 10 and the p-s wave separating / reflecting plate 20; It consists of a black absorbing film 21 provided as a light absorbing member on the back side of the separating reflection plate 20.

The scattering / transmission type liquid crystal cell 10 is of a polymer dispersion type, and the liquid crystal cell 10, the p-s wave separation / reflection plate 20, and the absorption film 2 provided as a light absorbing member are provided.
1 is the same as that of the above-mentioned first embodiment, and the duplicated description will be omitted by attaching the same reference numerals to the drawings.

FIG. 5 is a side view of the anisotropic scattering plate 24. The anisotropic scattering plate 24 has an incident angle within a specific angle range θ with respect to a vertical direction H indicated by a dashed line in FIG. Has a characteristic of emitting light incident without being scattered as shown by a solid line arrow in the figure, and scattering and emitting light incident at a larger incident angle as shown by a broken line arrow in the figure. . The angle range θ of light emitted without scattering by the anisotropic scattering plate 24 is, for example, 30 degrees (15 degrees with respect to the vertical direction H).

According to the liquid crystal display device of this embodiment, since the anisotropic scattering plate 24 is disposed between the liquid crystal cell 10 and the p-s wave separating / reflecting plate 20, the liquid crystal cell 10 can be viewed from the front. Out of the light scattered by the liquid crystal layer 15 and emitted to the back side of the liquid crystal cell 10, the anisotropic scattering plate 24 vertically divides the light as shown by the solid arrow in FIG. Is condensed so that the light traveling toward
The light (s-wave light) reflected by the s-wave separating / reflecting plate 20 is
Again, the light traveling in the vertical direction H can be condensed by the anisotropic scattering plate 24 so as to increase, and can be incident on the liquid crystal layer 15 from the back side thereof. A large amount of scattered light can be emitted to make the bright display even brighter.

In this liquid crystal display device, even in the dark display, light incident from the front and transmitted through the liquid crystal layer 15 of the liquid crystal cell 10 and emitted to the rear side is emitted by the anisotropic scattering plate 24 in the vertical direction. The light reflected by the p-s wave separating / reflecting plate 20 is again collected by the anisotropic scattering plate 24 so that the light traveling in the vertical direction H is increased. Since the light is emitted, the light emitted in the front direction increases, and the dark display becomes somewhat bright. On the other hand, since the emitted light is the light scattered by the anisotropic scattering plate 24, the dark display is performed. It is possible to suppress glare in dark display due to reflection of p-wave light on the p-s-wave separating / reflecting plate.

Light is incident on the liquid crystal display device at an incident angle of 20 degrees with respect to the normal line from the entire circumferential direction centered on the normal line on the front surface of the liquid crystal display device. (The direction along the line), the light reflectance (ratio of outgoing light to incident light) R, the chromaticity x, y of the outgoing light, and the contrast during bright display and dark display of the device, respectively. _CR is as follows.

The anisotropic scattering plate 24 used here is
An anisotropic scattering plate manufactured by Sumitomo Chemical Co., Ltd., which is commercially available under the trade name of “MFX1515”, and the reflectance R is Al ₂ O
The reflectance of this white reflector is set to 100% based on the reflectance of a single white reflector made of No. ₃ and the chromaticity of the emitted light is the x coordinate value on the CIE chromaticity diagram. And y coordinate values.

Bright display Reflectivity R = 92.1%, chromaticity x =
0.32, y = 0.33 Dark display, reflectance R = 25.4%, chromaticity x = 0.30, y
= 0.31 Contrast C _R = 3.6 Thus, in the liquid crystal display device of this embodiment, the contrast is reduced to some extent as compared with the liquid crystal display device of the above-described first embodiment. Since more scattered light can be emitted in a certain front direction, the display is further brightened, and glare in dark display due to reflection of p-wave light on the p-s wave separation / reflection plate 20 during dark display is suppressed. be able to.

In the third embodiment, the anisotropic scattering plate 24 is arranged between the liquid crystal cell 10 and the ps-wave separating / reflecting plate 20. Figure 6
May be arranged on the front side of the liquid crystal cell 10 as in the fourth embodiment shown in FIG. 10. Also in this embodiment, more scattered light is emitted in the front direction which is the viewing direction of the display, and the display is further performed. In addition to making the display brighter, glare of dark display due to reflection of p-wave light on the p-s wave separation / reflection plate 20 during dark display can be suppressed.

As in this embodiment, the liquid crystal display device in which the anisotropic scattering plate 24 is disposed on the front side of the liquid crystal cell 10 has a light reflectance R for bright display and dark display and a chromaticity x of the emitted light. ,
y and the contrast _CR are as follows.

Bright display Reflectivity R = 93.4%, chromaticity x =
0.32, y = 0.33 Dark display, reflectance R = 30.3%, chromaticity x = 0.30, y
= 0.30 Contrast C _R = 2.7 FIG. 7 is a cross-sectional view of a part of a liquid crystal display device according to a fifth embodiment of the present invention.
The scattering / transmission type liquid crystal cell 10 is provided with a plurality of color filters corresponding to the plurality of pixel regions, for example, red,
Green, blue color filters 18R, 18G, 18B
It is provided with.

That is, the scattering / transmission type liquid crystal cell 10 used in this embodiment has a plurality of pixel regions in which the electrodes 13 and 14 provided on the inner surfaces of the pair of substrates 11 and 12 are opposed to each other. A color filter 18R, 18G, 18B of three colors of red, green, and blue is provided on one of the pair of substrates 11 and 12, for example, on the inner surface of the front substrate 11 so as to correspond to the plurality of pixel regions, respectively. It is provided.

The scattering / transmission type liquid crystal cell 10 is of a polymer dispersion type, and this liquid crystal cell 10 has the above-described first embodiment except that it has the color filters 18R, 18G, 18B. Same as the example. Also p-
The s-wave separating and reflecting plate 20 and the absorbing film 21 provided as a light absorbing member are the same as those of the first embodiment.

According to the liquid crystal display device of this embodiment, as the scattering / transmission type liquid crystal cell 10, three color filters 18 of red, green and blue respectively corresponding to the plurality of pixel regions.
Since the one provided with R, 18G, and 18B is used, a bright and high-contrast full-color image can be displayed.

In the above embodiment, the color filters 18R, 18G, 18B are provided on the inner surface of the front substrate 11 of the liquid crystal cell 10.
Are provided, but the color filters 18R, 18G,
18B may be provided on the inner surface of the rear substrate 12, and in this way, a bright display due to light scattering is emitted forward of the scattered light scattered by the liquid crystal layer 15 of the liquid crystal cell 10. The non-colored light and the color of the color filters 18R, 18G, 18B are colored so that the liquid crystal cell 10
Of the scattered light reflected by the p-s wave separating / reflecting plate 20 and again scattered by the liquid crystal layer 15 and displayed forward, thereby displaying a brighter full-color image. Can be displayed.

Note that the color filters 18R, 18
The scattering / transmission type liquid crystal cell 10 provided with G and 18B may be used in any of the liquid crystal display devices of the above-described first to fourth embodiments.

The scattering / transmission type liquid crystal cell 10 comprises:
The liquid crystal layer is not limited to the polymer dispersion type, and may be a phase transition type in which a liquid crystal layer made of a cholesteric liquid crystal having a positive dielectric anisotropy or a mixed liquid crystal of a cholesteric liquid crystal and a nematic liquid crystal is provided between a pair of transparent substrates.

Further, the scattering / transmission type liquid crystal cell 10
Is not limited to the active matrix type, but may be a simple matrix type, and in the case of a black and white display liquid crystal display device, a segment type may be used.

[0104]

The liquid crystal display device of the present invention has a reflection axis and a transmission axis orthogonal to each other on the back side of a scattering / transmission type liquid crystal cell, and reflects s-wave light of a polarization component along the reflection axis. Since a p-s-wave separating / reflecting plate for transmitting the p-wave light of the polarization component along the transmission axis is provided, and a light absorbing member is provided on the back side of the p-s-wave separating / reflecting plate, the light is incident. Bright display due to light scattering can be made sufficiently bright, and a display with good contrast can be obtained.

In the liquid crystal display device of the present invention, the p
The light absorbing member provided on the back side of the -s wave separation / reflection plate is preferably a black absorption film that absorbs most of the incident light, and by using this black absorption film, the p-s wave separation / reflection plate can be used. It is possible to substantially completely prevent the light transmitted through the light from being reflected and emitted forward, thereby making the dark display darker.

The light absorbing member may be a polarizing plate that absorbs light of a polarization component along the absorption axis and transmits light of a polarization component along the transmission axis. By arranging the transmission axis in a direction intersecting the transmission axis of the p-s wave separation reflector,
The light transmitted through the -s-wave separation reflection plate can be absorbed by the polarizing plate.

As described above, when a polarizing plate is used as the light absorbing member, a light reflecting member may be provided on the back side of the polarizing plate. With such a configuration, the bright display can be made brighter. can do.

In this case, the dark display becomes somewhat bright, but the external light mainly enters from a direction obliquely inclined with respect to the front direction which is the viewing direction of the display.
Since the light is reflected obliquely forward with respect to the front direction by the s-wave separation reflection plate and the light reflection member, the dark display observed from the front direction is sufficiently dark, and therefore, the brightness between the bright display and the dark display is high. Display with a sufficiently large difference in contrast can be obtained.

Further, in the liquid crystal display device according to the present invention, between the liquid crystal cell and the p-s wave separating / reflecting plate or on the front side of the liquid crystal cell, an angle within a specific angle range with respect to the vertical direction. It is desirable to dispose an anisotropic scattering plate that emits light incident at an incident angle without scattering, and scatters and emits light incident at a larger incident angle. The scattered light is emitted more in the front direction, which is the observation direction of, and the display is further brightened, and the glare of the dark display due to the reflection of the p-wave light by the p-s wave separation reflector at the time of the dark display is suppressed. can do.

Further, the liquid crystal cell has a plurality of pixel regions in which electrodes provided on inner surfaces of a pair of substrates are opposed to each other, and one of the pair of substrates has
A plurality of color filters respectively corresponding to the plurality of pixel regions may be provided. By using such a liquid crystal cell, a bright and high-contrast multicolor image can be displayed.

[Brief description of the drawings]

FIG. 1 is a sectional view of a part of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a perspective view of a p-s wave separating / reflecting plate 20;

FIG. 3 is a sectional view of a part of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 4 is a sectional view of a part of a liquid crystal display device according to a third embodiment of the present invention.

FIG. 5 is a side view of the anisotropic scattering plate.

FIG. 6 is a sectional view of a part of a liquid crystal display device according to a fourth embodiment of the present invention.

FIG. 7 is a sectional view of a part of a liquid crystal display device according to a fifth embodiment of the present invention.

FIG. 8 is a cross-sectional view of a part of a conventional scattering type liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 10 scattering / transmission type liquid crystal cell (polymer dispersed liquid crystal cell) 11, 12 substrate 13 14, electrode 15 liquid crystal layer (liquid crystal / polymer composite layer) 18R, 18G, 18B color filter 20 p- s-wave separating / reflecting plate 20 21: absorbing film (light absorbing member) 22: polarizing plate (light absorbing member) 23: light reflecting member 24: anisotropic scattering plate

Claims (6)

[Claims] An electrode is provided on an inner surface of a pair of substrates opposed to each other, and incident light is scattered between the pair of substrates in accordance with a change in an alignment state of liquid crystal molecules due to an electric field applied between the electrodes. And a scattering / transmission type liquid crystal cell provided with a liquid crystal layer to be transmitted, having a reflection axis and a transmission axis in directions orthogonal to each other, and having a reflection axis and a transmission axis orthogonal to each other. A p-s wave separating / reflecting plate is disposed, which reflects the s-wave light of the polarization component along the reflection axis toward the liquid crystal cell and transmits the p-wave light of the polarization component along the transmission axis to the back side. And a light absorbing member provided on the back side of the p-s wave separating / reflecting plate. 2. The light absorbing member according to claim 1, wherein the light absorbing member is a black type absorbing film that absorbs most of incident light.
3. The liquid crystal display device according to 1. 3. The light-absorbing member is a polarizing plate that absorbs light having a polarization component along an absorption axis and transmits light having a polarization component along a transmission axis. The p
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is arranged in a direction intersecting a transmission axis of the -s-wave separation reflector. 4. The liquid crystal display device according to claim 3, wherein a light reflecting member is provided on a back side of the polarizing plate. 5. A method for scattering light incident at an incident angle within a specific angle range with respect to a vertical direction between said liquid crystal cell and said p-s wave separating reflector or on the front side of said liquid crystal cell. The liquid crystal display device according to claim 1, further comprising an anisotropic scattering plate that emits light without incident, and scatters and emits light incident at an incident angle larger than that. 6. The liquid crystal cell has a plurality of pixel regions in which the electrodes provided on inner surfaces of the pair of substrates are opposed to each other, and one of the pair of substrates is provided with the plurality of pixel regions. The liquid crystal display device according to any one of claims 1 to 5, wherein a plurality of color filters corresponding to the pixel regions are provided.