JP2002198185A - Luminescence element and liquid crystal display using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a luminescence element that will not reflect incidence light at the time of putting out light having a luminescence layer which consists of an organic material. SOLUTION: A transparent light-emitting side electrode 3 and a backside electrode 5a, which consists of an optical permeability conducting film 6, which is made from metal material, having small work function of electron injection to the above luminescence layer 2, and an optical absorption layer 7 laminated on the conductive film 6, are prepared by sandwiching the luminescence layer 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device and a liquid crystal display using the same.

[0002]

2. Description of the Related Art For example, as a light emitting element used as an illumination light source of a liquid crystal display device, there is a light emitting element provided with a transparent emission side electrode and a rear side electrode with a light emitting layer made of an organic material interposed therebetween. The element is called an organic EL (electroluminescence) element.

In this light emitting element, the emission side electrode is used as an anode and the rear side electrode is used as a cathode, and is driven by applying a voltage between these electrodes. The emission side electrode is made of ITO or the like. Formed of a transparent conductive material,
The rear electrode is formed of a metal material such as an Mg (magnesium) alloy having a small work function of injecting electrons into the light emitting layer.

[0004]

However, in the conventional light emitting device, the light emitting layer made of an organic material has a light transmitting property, and the rear electrode is a glossy high reflectance electrode. At the time of turning off the light without applying the driving voltage, the light incident from the emission side is reflected by the rear electrode. Therefore, the conventional light-emitting element has low contrast between lighting and extinguishing in a bright environment where light enters from the emission side.

It is an object of the present invention to provide a light emitting element which does not reflect incident light when the light is turned off, and to provide a liquid crystal display device using the light emitting element.

[0006]

A light emitting device according to the present invention comprises:
A transparent emission-side electrode and a light-absorbing rear electrode are provided with a light-emitting layer made of an organic material interposed therebetween.

In this light-emitting element, since the rear electrode has a light absorbing property, external light incident from the emission side can be absorbed by the rear electrode, and therefore, when the light is turned off, the incident light is reflected. Nothing.

Further, in the liquid crystal display device of the present invention, electrodes are provided on inner surfaces of a front substrate which is a display observation side and a rear substrate facing the front substrate, respectively, and a liquid crystal layer is provided between these substrates. And a polarizing element disposed in front of the liquid crystal element and absorbing one of the two orthogonal polarization components of the incident light and transmitting the other polarization component. A reflection polarizing plate that is disposed on the rear side of the liquid crystal element and reflects light of one polarization component of the two polarization components of the incident light that are orthogonal to each other and transmits light of the other polarization component; An output surface is disposed on the rear side of the reflective polarizing plate so as to face the rear surface of the reflective polarizing plate,
A light-emitting element comprising a transparent emission-side electrode and a light-absorbing rear electrode with a light-emitting layer made of an organic material interposed therebetween is provided.

This liquid crystal display device can be used in a bright environment.
The reflection display using external light that is the light of the environment is performed. In the case of the reflection display, the light of one polarization component of the external light incident from the front side of the liquid crystal display device is the absorption polarizer. And the light of the other polarization component is transmitted through the absorbing polarizer, becomes linearly polarized light, and enters the liquid crystal element. Then, the light incident on the liquid crystal element is incident on the reflective polarizer due to the birefringence effect of the liquid crystal layer in the process of transmitting through the liquid crystal element. The light reflected by the polarizing plate is emitted to the front side, and the light of the other polarized light component is transmitted through the reflective polarizing plate, enters the light emitting element, and is then absorbed by the side electrode.

That is, in the case of the reflective display, the display in the area where the light incident from the front side and transmitted through the absorbing polarizer and the liquid crystal element is reflected by the reflective polarizer and emitted to the front side becomes a bright display. The display of the region where the incident light is transmitted through the reflective polarizing plate and absorbed by the rear electrode of the light emitting element is a dark display.

The liquid crystal display device utilizes the light emitted from the light emitting element by turning on the light emitting element in a dark environment where the display is hardly visible in the reflective display using external light. The transmissive display is performed, and in the transmissive display, of the light emitted from the light emitting element, light of one polarization component is reflected to the rear side by the reflective polarizing plate, and light of the other polarization component is reflected. The light passes through the reflective polarizing plate, becomes linearly polarized light, and enters the liquid crystal element. The light incident on the liquid crystal element is subjected to birefringence by the liquid crystal layer in the process of passing through the liquid crystal element, and is incident on the absorbing polarizer. The light of the other polarization component absorbed by the polarizing plate is transmitted through the absorbing polarizing plate and emitted to the front side.

That is, in the case of this transmissive display, the display of the region where the incident light emitted from the light emitting element and transmitted through the reflective polarizer and the liquid crystal element is transmitted through the absorbing polarizer and emitted to the front side is displayed. The display becomes bright, and the display of the region where the incident light is absorbed by the absorbing polarizer becomes a dark display.

Since the transmissive display is performed in a dark environment, external light is incident from the front side, and of the light, the light reflected by the reflective polarizer is emitted to the front side. There is almost no uplift.

Therefore, according to this liquid crystal display device,
In both reflective display using external light and transmissive display using light emitted from the light emitting element, a bright display is sufficiently bright, and a dark display is sufficiently dark, and a display with good contrast is obtained. be able to.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, the light emitting device of the present invention comprises a transparent emission side electrode and a light absorbing rear electrode sandwiching a light emitting layer made of an organic material. When the light is turned off, the incident light is not reflected.

In this light emitting device, the rear electrode is
Desirably, the electrodes are black. Further, it is preferable that the rear electrode is formed of a light-transmitting conductive film made of a metal material having a small work function of injecting electrons into the light-emitting layer, and a light-absorbing layer laminated on the rear surface.

Further, as described above, in the liquid crystal display device of the present invention, the absorbing polarizer is disposed on the front side of the liquid crystal element, and the reflective polarizer is disposed on the rear side of the liquid crystal element. On the rear side, the light-emitting element in which a transparent emission-side electrode and a light-absorbing rear electrode are provided with a light-emitting layer made of an organic material interposed therebetween, the emission surface of which faces the rear surface of the reflective polarizing plate. By arranging them, even in the case of reflective display using external light, even in the case of transmissive display using light emitted by the light emitting element, bright display is sufficiently bright, and dark display is sufficiently dark. It is intended to obtain a display with good contrast.

In this liquid crystal display device, at least one of the liquid crystal element and the reflective polarizer, the liquid crystal element and the absorbing polarizer, and the reflective polarizer and the light emitting element. It is desirable to arrange a means for diffusing the transmitted light at each location.

[0019]

FIG. 1 is a partial sectional view showing a first embodiment of the light emitting device of the present invention.

This light emitting element 1a has a transparent emission side electrode 3 and a light absorbing rear electrode 5a sandwiching a light emitting layer 2 made of an organic material. Is provided on the rear surface of the emission side transparent substrate 4 made of glass or the like.
It is formed of a transparent conductive material such as ITO.

Although the light emitting layer 2 is shown as a single layer in FIG. 1, the light emitting layer 2 is made of a conductive polymer made of a conductive polymer having a fixed length of a π-electron conjugated system in accordance with the emission wavelength band. -N
It comprises a polymer layer having a bonding structure, an electron transport layer laminated on the surface on the emission side of the polymer layer, and a hole transport layer laminated on the other surface of the polymer layer.

The polymer layer is made of, for example, polypyrrole (P) having a fixed length of a π-electron conjugated system according to the emission wavelength band.
It consists of a block copolymer in which polymer blocks composed of oligomers or polymers of Py) are chemically bonded via spacers such as methylene chains. The electron transport layer is made of, for example, dodecylbenzenesulfonic acid derivative (DBS), and the hole transport layer is made of, for example, a tetramethylammonium derivative (TMA).

Further, the rear electrode 5a having the light absorbing property
Is a black electrode, and the rear electrode 5a is formed of a Mg-based alloy (for example, an Mg-In alloy or Mg-based alloy) having a small work function of injecting electrons into the light emitting layer 2 formed on the surface in contact with the light emitting layer 2. -Ag alloy) and a light-transmitting conductive film 6 formed to be extremely thin enough to transmit light, and a black light-absorbing layer 7 laminated on the rear surface of the light-transmitting conductive film 6. I have.

The light-transmitting conductive film 6 has a thickness of 0.01 to minimize reflection of light by the conductive film 6.
The light absorbing layer 7 is formed to a thickness of about μm to 0.1 μm, and preferably further thinner.
In order to compensate for an increase in the electric resistance of the rear electrode 5a due to the reduction in the film thickness of the rear electrode 5, the rear electrode 5a is formed of a black conductive material such as graphite.

The light emitting element 1a is driven to be lit by applying a voltage between the electrodes 3 and 5a using the emission side electrode 3 as an anode and the rear side electrode 5a as a cathode. 2 emits light (light in the emission wavelength band of the light-emitting layer 2) through the transparent emission-side electrode 3 and the transparent substrate 4.

In the light emitting element 1a, since the rear electrode 5a has a light absorbing property, external light incident from the emission side can be absorbed by the rear electrode 5a. Even below, it does not reflect incident light from the exit side.

That is, in this embodiment, since the rear electrode 5a is formed by the light transmitting conductive film 6 and the light absorbing layer 7 laminated on the rear surface, the light emitting element 1a has its light emitting surface. Can be transmitted through the light transmitting conductive film 6 and absorbed by the light absorbing layer 7.

In this embodiment, the rear electrode 5
a is a black electrode having a black light-absorbing layer 7, so that when viewed from the emission surface side when the light is turned off, the rear electrode 5
The color a is black.

In this embodiment, the rear electrode 5
Since the light-transmitting conductive film 6a is formed of a metal material having a small work function for electron injection into the light emitting layer 2, the work function for electron injection from the rear electrode 5a to the light emitting layer 2 is suppressed to a small value. , A good light emitting function can be secured.

Further, in this embodiment, the light absorbing layer 7
Is formed of a conductive material such as graphite, the electrical resistance of the rear electrode 5a can be reduced even if the film thickness of the conductive film 6 is small, and therefore, the light emitting element 1a
Can be driven with low power.

The output side electrode 3 and the rear side electrode 5a
Is a single-film electrode facing the entire area of the light-emitting layer 2,
Therefore, at the time of lighting (when a voltage is applied between the electrodes 3 and 5a), light is emitted from the region corresponding to the entire area of the light emitting layer 2, and at the time of extinguishing, the area corresponding to the entire area of the light emitting layer 2 is provided. Looks black.

FIG. 2 is a partial sectional view showing a second embodiment of the light emitting device according to the present invention.
b, a rear electrode 5b is formed on a light-transmitting conductive film 6 made of a metal material such as an Mg-based alloy having a small work function of injecting electrons into the light-emitting layer 2 and a rear surface of the light-transmitting conductive film 6. A transparent conductive film 8 made of ITO or the like;
And a black light-absorbing layer 9 made of a resin material to which a black pigment is added, laminated on the rear surface.

The light emitting element 1b of this embodiment is different from the light emitting element 1a of the first embodiment in the structure of the rear electrode 5b except for the structure of the rear electrode 5b. Are given the same reference numerals and are omitted.

Also in the light emitting element 1b of this embodiment, since the rear electrode 5b is a black electrode, the color of the rear electrode 5a that can be seen from the emission surface side when the light is turned off is black.

In this embodiment, the rear electrode 5
b is a light-transmitting conductive film 6 made of a metal material having a small work function of injecting electrons into the light-emitting layer 2, and a light-transmitting conductive film 6 formed on the rear surface of the light-transmitting conductive film 6. Is formed by a transparent conductive film 8 having a sufficiently large thickness and a black light absorbing layer 9 made of a resin material to which a black pigment is added, which is laminated on the rear surface of the transparent conductive film 8. ,
The work function of injecting electrons from the rear electrode 5b into the light emitting layer 2 is reduced, a good light emitting function is ensured, and the electric resistance of the rear electrode 5a is formed on the rear surface of the light transmitting conductive film 6. The light emitting element 1b can be lighted and driven with low power by reducing the size of the transparent conductive film 8 formed.

In the light emitting device 1b of this embodiment, as shown in FIG. 2, the transparent conductive film 8 of the rear electrode 5b has the thickness of the light transmitting conductive film 6 (0.01 μm to 0.2 μm).
(Approximately 1 μm), so that the electrical resistance of the rear electrode 5a can be further reduced.

The light-emitting elements 1a and 1b of the first and second embodiments have the light-absorbing layers 7, 9 of the rear electrodes 5a, 5b formed of a black material. 7 and 9 are formed of a coloring material that reflects light of an arbitrary wavelength band different from the light emission wavelength band of the light emitting layer 2 and absorbs light of other wavelength bands, or
The light-emitting layer 2 may transmit light of an arbitrary wavelength band different from the emission wavelength band, and may have a configuration in which a reflective film is formed on a rear surface of a coloring layer made of a coloring material that absorbs wavelength light of another wavelength band. By doing so, when the light is turned off,
A colored surface different from the emission color of the light emitting layer 2 can be seen.

Further, the light emitting device 1a of the first embodiment
In the light emitting device 1b of the second embodiment, the rear electrodes 5a and 5b have a two-layer structure including a light transmitting conductive film 6 and a light absorbing layer 7. Transparent conductive film 6
And a transparent conductive film 8 and a light absorbing layer 9 in a three-layer structure. The rear electrode has a small work function of injecting electrons into the light emitting layer 2 and has a black or any other color. A single-layer electrode made of a light-absorbing conductive material having

Next, an embodiment of the liquid crystal display device of the present invention will be described.

FIG. 3 is an exploded perspective view of the liquid crystal display device of this embodiment. This liquid crystal display device has a liquid crystal element 10, an absorption polarizer 18 disposed in front of the liquid crystal element 10, and
Reflective polarizing plate 19 disposed behind liquid crystal element 10
A diffusion plate 20 disposed as a means for diffusing transmitted light between the liquid crystal element 10 and the reflective polarizing plate 19; and a light emitting element 1a disposed on the rear side of the reflective polarizing plate 11. .

FIG. 4 is an enlarged sectional view of a part of the liquid crystal element 10. The liquid crystal element 10 includes a front transparent substrate 11 which is a display observation side, and a rear transparent substrate opposed to the front substrate 11. And a liquid crystal layer 17 for controlling the polarization state of the transmitted light according to the electric field applied between the transparent electrodes 13 and 14 provided on the inner surfaces of the substrates 11 and 12, respectively. It has become.

The liquid crystal element 10 is, for example, of an active matrix type. One of a pair of front and rear substrates 11 and 12, for example, an electrode 14 provided on the inner surface of a rear substrate 12 is provided. A plurality of pixel electrodes arranged in a matrix in the row direction and the column direction, and an electrode 13 provided on the inner surface of the front substrate 11, which is the other substrate, is a single film-shaped counter electrode facing the plurality of pixel electrodes 14. Electrodes.

Although not shown in FIG. 4, a pair of front and rear substrates 11, 12, a plurality of TFTs (each connected to the plurality of pixel electrodes 14) are provided on the inner surfaces of the rear substrate 12. Thin-film transistors), a plurality of gate lines for supplying gate signals to the TFTs in each row,
A plurality of data lines for supplying data signals to the TFTs in each column are provided.

The pair of substrates 11 and 12 are joined at their peripheral edges via a frame-shaped sealing material (not shown), and a region surrounded by the sealing material between the substrates 11 and 12 is provided. A liquid crystal layer 17 is provided.

The liquid crystal molecules of the liquid crystal layer 17 are separated from the substrates 11 and 12 by the alignment films 13 and 14 provided on the inner surfaces of the pair of substrates 11 and 12 so as to cover the electrodes 13 and 14.
The orientation direction in the vicinity of is restricted, and a pair of substrates 11 and
It is oriented in a predetermined initial orientation state between the twelve.

The absorption polarizer 18 has a transmission axis 18a and an absorption axis (not shown) in directions perpendicular to each other, and of the two orthogonal polarization components of the incident light, along the absorption axis. Absorb the light of the other polarization component,
The light of the other polarization component along the transmission axis 18a is transmitted.

On the other hand, the reflection polarizing plate 19 has a transmission axis 19p and a reflection axis 19s in directions orthogonal to each other, and one of two orthogonal polarization components of incident light along the reflection axis 19s. Reflects polarized light,
The light of the other polarization component along the transmission axis 10p is transmitted.

The liquid crystal display device of this embodiment has a TN
The liquid crystal molecules of the liquid crystal layer 17 of the liquid crystal element 10 are of a (twisted nematic) type.
It is twist-oriented at a twist angle of about 90 ° between 1 and 12.

That is, in FIG. 3, arrows 11a, 1
2a is an alignment direction of the liquid crystal molecules in the vicinity of the front substrate 11 and the rear substrate 12 of the liquid crystal element 10 (the alignment film 1).
5 and 16), and the liquid crystal layer 1
The liquid crystal molecules of No. 7 are oriented in directions near each other in the vicinity of the front substrate 11 and in the vicinity of the rear substrate 12 by approximately 90 °. Twist orientation at a twist angle of °.

As shown in FIG. 1, the absorption polarizing plate 18 on the front side of the liquid crystal element 10 has its transmission axis 18a substantially parallel to the liquid crystal molecule alignment direction 11a near the front substrate 11 of the liquid crystal element 10. The reflection polarizing plate 19 on the rear side of the liquid crystal element 10 has its transmission axis 19p substantially parallel to the transmission axis 18a of the absorption polarizing plate 18, and the reflection axis 19s. It is arranged substantially orthogonal to the transmission axis 18a of the absorbing polarizer 18.

The light emitting element 1a is the same as the light emitting element of the first embodiment shown in FIG. 1 and has an area corresponding to the entire display area of the liquid crystal element 10. The light exiting surface is disposed on the rear side of the reflective polarizing plate 19 with the exit surface facing the rear surface of the reflective polarizing plate 19.

In a bright environment, this liquid crystal display device
Perform reflective display using external light that is the light of the environment,
In a dark environment where the display is hardly visible in the reflective display using external light, the light-emitting element 1a is turned on to perform transmissive display using the light emitted from the light-emitting element 1a.

First, a description will be given of a reflection display using external light. In the case of this reflection display, one of the external light components along the absorption axis of the absorbing polarizer 18 of the external light incident from the front side of the liquid crystal display device. Is absorbed by the absorption polarizer 18, and the light of the other polarization component along the transmission axis 18 a of the absorption polarizer 18 is transmitted through the absorption polarizer 18 and becomes linearly polarized light. Incident.

The light incident on the liquid crystal element 10 is subjected to a birefringence effect by the liquid crystal layer 17 in the process of passing through the liquid crystal element 10, is diffused by the diffusion plate 20 and is incident on the reflective polarizing plate 19. Of the light, the reflection polarizing plate 1
The light of one polarization component along the reflection axis 19s of No. 9 is reflected by the reflection polarizing plate 19, is again diffused by the diffusion plate 20, and passes through the liquid crystal element 10 and the absorption polarizing plate 18 to be on the front side. Out.

Further, of the light transmitted through the liquid crystal element 10 and diffused by the diffuser 20 and incident on the reflective polarizer 19, the light of one polarized component along the transmission axis 19 p of the reflective polarizer 19 is used. Is transmitted through the reflective polarizing plate 19, enters the light emitting element 1a, and is absorbed by the rear electrode 5a (see FIG. 1).

That is, in the case of the reflective display, the display in the area where the light incident from the front side and transmitted through the absorption polarizer 18 and the liquid crystal element 10 is reflected by the reflective polarizer 19 and emitted to the front side is a bright display. The display in the region where the incident light is transmitted through the reflective polarizing plate 19 and absorbed by the rear electrode 5a of the light emitting element 1a becomes a dark display.

In the case of this reflective display, light enters from the front side,
Of the light transmitted through the absorption polarizer 18 and the liquid crystal element 10 and incident on the reflective polarizer 19, the light of the polarization component along the reflection axis 19 s of the reflective polarizer 19 is reflected by the reflective polarizer 19. Since the light is emitted to the front side, the brightness of the bright display by the emitted light is sufficient.
Since the light of the polarization component along the transmission axis 19p passes through the reflective polarizing plate 19 and enters the light emitting element 1a and is absorbed by the rear electrode 5a of the light emitting element 1a, the darkness of the dark display is also sufficient. It is.

The bright display at the time of the reflection display is a display of the same color as the external light incident from the front side, and in an ordinary environment, the external light incident is white light. It is white. Further, the dark display is a display of the color of the rear electrode 5a of the light emitting element 1a, and is a display of the light emitting element 1a shown in FIG.
Since the rear electrode 5a is a black electrode, the dark display color is black.

Next, a description will be given of a transmissive display using the light emitted from the light emitting element 1a. In the transmissive display, of the light emitted from the light emitting element 1a, along the reflection axis 19s of the reflective polarizing plate 19. The light of one polarization component is reflected rearward by the reflection polarizing plate 19, and the light of the other polarization component along the reflection axis 19s of the reflection polarization plate 19 is
The light passes through the reflective polarizing plate 19 to become linearly polarized light, and the light is diffused by the diffusion plate 20 and enters the liquid crystal element 10.

The light incident on the liquid crystal element 10 is subjected to the birefringence effect of the liquid crystal layer 17 in the process of transmitting through the liquid crystal element 10 and is incident on the absorbing polarizing plate 18. Light of one polarized component along the absorption axis of the plate 18 is absorbed by the absorbing polarizer 18, and light of the other polarized component along the transmission axis 18 a of the absorbing polarizer 18 is transmitted through the absorbing polarizer 18. And is emitted to the front side.

That is, in the case of the transmissive display, the light emitting element 1
a, the display of the area where the incident light transmitted through the reflective polarizer 19 and the liquid crystal element 10 is transmitted through the absorbing polarizer 18 and emitted to the front side becomes a bright display, and the incident light is reflected by the absorbing polarizer 18. The display of the absorbed area becomes a dark display.

In this transmissive display, of the light emitted from the light emitting element 1a, transmitted through the reflective polarizing plate 19 and the liquid crystal display element 10 and incident on the absorbing polarizer 18, the transmission axis of the absorbing polarizer 18 is used. Since the light of the polarization component along 18a passes through the absorbing polarizer 18 and is emitted to the front side, the brightness of the bright display by the emitted light is sufficient, and along the absorption axis of the absorbing polarizer 18 Since the light of the polarized component is absorbed by the reflective polarizing plate 18, the darkness of the dark display is sufficient.

The bright display in the transmissive display has the same color as the emission color of the light emitting element 1a, and the dark display is black.

Further, as described above, this transparent display is
In reflective display using external light, the display is performed in a dark environment where the display can hardly be visually recognized. Therefore, external light incident on the liquid crystal display device at the time of transmissive display is extremely small or almost nonexistent. Therefore, there is almost no rise in the darkness of the dark display due to the light reflected by the reflective polarizing plate 19 out of the external light incident from the front side being emitted to the front side.

Therefore, according to this liquid crystal display device,
In both the reflective display using external light and the transmissive display using the light emitted from the light emitting element 1a, a bright display is sufficiently bright, and a dark display is sufficiently dark. Obtainable.

Further, in the liquid crystal display device of this embodiment, since the diffusion plate 20 is disposed between the liquid crystal element 10 and the reflection polarizing plate disposed on the rear side, the transmission display is also performed in the reflection display. Also at this time, the light diffused by the diffusion plate 20 is emitted to the front side, and the viewing angle at which a display can be observed with good contrast can be widened.

The diffusion plate 20 is not limited to the space between the liquid crystal element 10 and the reflective polarizer 19, but may be between the liquid crystal element 10 and the absorption polarizer 18 or between the reflective polarizer 19 and the light emitting element 1a. And may be arranged at a plurality of positions among the three.

Further, the liquid crystal display device of the above embodiment is similar to that of FIG.
The light-emitting element 1a shown in FIG. 2 may be used, but the light-emitting element disposed on the rear side of the reflective polarizing plate 19 may be the light-emitting element 1a shown in FIG.

Further, the light emitting element is not limited to the one in which the rear electrode is a black electrode, and the rear electrode reflects light of an arbitrary wavelength band different from the emission wavelength band of the light emitting layer. In such a case, the dark display in the reflective display may be the colored display of the color of the rear electrode.

Further, the liquid crystal display device of the above embodiment has a TF
An active matrix type liquid crystal element 10 having T as an active element is provided.
An active matrix type using a two-terminal non-linear resistance element such as IM as an active element, or a simple matrix type may be used.

Further, the present invention is not limited to the TN type liquid crystal display device, but the liquid crystal molecules can be set at 180 to 270 degrees (usually 23 degrees).
STN (super twisted nematic) type using a liquid crystal element twist-aligned at a twist angle of 0 to 250 degrees), and a homogeneous alignment type liquid crystal display using a liquid crystal element having liquid crystal molecules aligned homogeneously along one direction. The present invention can be applied to a device and a liquid crystal display device using a ferroelectric liquid crystal or an antiferroelectric liquid crystal element.

Further, the light emitting device of the present invention can be widely used not only for a liquid crystal display device but also for other uses.

[0073]

According to the light emitting device of the present invention, a transparent emission side electrode and a light absorbing rear electrode are provided with a light emitting layer made of an organic material interposed therebetween. Is not reflected.

In this light emitting device, the rear electrode is
It is desirable that the electrode be a black electrode. By doing so, it is possible to make the color seen from the emission surface side when the light is turned off black.

In this light-emitting device, the rear electrode includes a light-transmitting conductive film made of a metal material having a small work function for injecting electrons into the light-emitting layer, and a light-absorbing layer laminated on the rear surface. It is preferable to form it. By doing so, the work function of injecting electrons from the rear electrode into the light emitting layer can be reduced, and a good light emitting function can be secured.

Further, in the liquid crystal display device of the present invention, an absorbing polarizer is disposed in front of the liquid crystal element, a reflective polarizer is disposed behind the liquid crystal element, and an organic polarizer is disposed behind the reflective polarizer. The light-emitting element in which a transparent emission-side electrode and a light-absorbing rear electrode are provided with a light-emitting layer made of a material interposed therebetween, wherein the light-emitting element is arranged with its emission surface facing the rear surface of the reflective polarizing plate. Therefore, both in the reflective display using external light and in the transmissive display using the light emitted from the light emitting element, the bright display is sufficiently bright, and the dark display is sufficiently dark. Can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial sectional view showing a first embodiment of a light emitting device of the present invention.

FIG. 2 is a partial sectional view showing a second embodiment of the light emitting device of the present invention.

FIG. 3 is an exploded perspective view showing one embodiment of the liquid crystal display device of the present invention.

FIG. 4 is an enlarged sectional view of a part of a liquid crystal element used in the liquid crystal display device.

[Explanation of symbols]

 1a, 1b: light-emitting element 2: light-emitting layer 3: emission side electrode 4: substrate 5a: rear electrode 6: light-transmitting conductive film 7: light-absorbing layer 5b: rear electrode 8: transparent conductive film 9: light-absorbing layer DESCRIPTION OF SYMBOLS 10 ... Liquid crystal element 11, 12 ... Substrate 11a ... Liquid crystal molecule orientation direction near a front substrate 12a ... Liquid crystal molecule orientation direction near a rear substrate 13, 14 ... Electrode 17 ... Liquid crystal layer 18 ... Absorption polarizing plate 18a ... Transmission axis 19: reflection polarizing plate 19s: reflection axis 19p: transmission axis

Claims (4)

[Claims] 1. A light-emitting element comprising a transparent light-emitting side electrode and a light-absorbing rear electrode sandwiching a light-emitting layer made of an organic material. 2. The light emitting device according to claim 1, wherein the rear electrode is a black electrode. 3. A light-transmitting conductive film made of a metal material having a small work function for injecting electrons into a light-emitting layer, and a light-absorbing layer laminated on a rear surface of the rear electrode. The light emitting device according to claim 1, wherein 4. A liquid crystal element comprising electrodes provided on inner surfaces of a front substrate on a display observation side and a rear substrate opposed to the front substrate, and a liquid crystal layer provided between these substrates. An absorption polarizer that is arranged on the front side of the liquid crystal element and absorbs one polarized light component and transmits the other polarized light component among two polarized light components of the incident light that are orthogonal to each other,
A reflective polarizing plate disposed on the rear side of the liquid crystal element, for reflecting light of one of the two polarized components of the incident light orthogonal to each other and transmitting light of the other polarized component; On the rear side of the plate, an emission surface is arranged to face the rear surface of the reflective polarizing plate, and a transparent emission side electrode and a light-absorbing rear electrode are provided with a light emitting layer made of an organic material interposed therebetween. A liquid crystal display device comprising a light emitting element.