JP2004163583A - Electrooptical device and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrooptical device with which high contrast of light emitted from a liquid crystal layer is obtained and of which the thickness can be reduced. <P>SOLUTION: The electrooptical device 10 is provided with the liquid crystal layer 13 containing liquid crystal molecules whose alignment directions are under control. Also, the electrooptical device 10 is provided with a polarizing plate 15 disposed on one side of the liquid crystal layer 13, an organic EL device 20 as a light source disposed on the side opposite to the polarizing plate 15 with respect to the liquid crystal layer 13 and a planar polarization beam splitter 17 disposed between the liquid crystal layer 13 and the light source 20, which separates incident light into transmitted light and reflected light via polarization. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an electro-optical device having a liquid crystal layer, and an electronic apparatus having the electro-optical device, and more particularly to a technique for increasing the contrast of light emitted from a liquid crystal layer.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in an electro-optical device having a liquid crystal layer, there is a technique in which a light source is disposed on the back side of a liquid crystal layer and light from this light source is used as necessary in order to increase the contrast of light emitted from the liquid crystal layer. (For example, see Patent Document 1).
[0003]
[Patent Document 1]
JP-A-8-292413
[0004]
[Problems to be solved by the invention]
However, in the related art, a light-absorbing polarizing plate is disposed between the liquid crystal layer and the light source in order to enable control of light emission through the liquid crystal layer. Therefore, part of the light from the light source is absorbed by the polarizing plate, and the light use efficiency is low.
[0005]
In addition, the above-described technique has a problem that it is difficult to reduce the thickness of a component that guides light from a light source to a liquid crystal layer.
[0006]
The present invention has been made in view of the above-described circumstances, and provides an electro-optical device in which the contrast of light emitted from a liquid crystal layer is high and the thickness is reduced, and an electronic apparatus including the electro-optical device. Aim.
[0007]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, an electro-optical device according to the present invention is directed to an electro-optical device according to the present invention, wherein a liquid crystal including liquid crystal molecules is disposed between a polarizing plate, a light source, and the polarizing plate and the light source. A liquid crystal layer containing molecules; and a planar polarization beam splitter disposed between the liquid crystal layer and the light source and separating incident light into transmitted light and reflected light.
In this electro-optical device, a polarizing plate is disposed on one side of the liquid crystal layer, and a planar polarization beam splitter is disposed on the opposite side. Since the light from the light source is polarized through the plane-type polarizing beam splitter, it is possible to control the emission of light through the liquid crystal layer without placing a light-absorbing polarizer between the liquid crystal layer and the light source It becomes. In this case, among the light from the light source, components other than the light transmitted through the planar polarization beam splitter are reflected, and the light is reused, thereby increasing the light use efficiency. Thereby, the contrast of light emitted from the liquid crystal layer can be increased.
[0008]
For example, by disposing a wavelength correction plate that gives a phase difference to light between the flat beam splitter and the light source, the light reflected by the flat polarizing beam splitter is transmitted to the flat polarizing beam splitter. Becomes possible. By reusing such light, the use efficiency of light from the light source is reliably increased. As the wavelength correction plate, for example, a circularly polarizing plate or a λ / 4 plate is used.
[0009]
In the above electro-optical device, the light source may include an organic EL device.
Since the organic EL device emits light with high luminance and is suitable for thinning, the light source including the organic EL device can reduce the thickness of the electro-optical device.
[0010]
In this case, the organic EL device may include a plurality of types of organic EL elements having different emission colors.
This makes it possible to change the color of light emitted from the liquid crystal layer.
[0011]
Further, in the above electro-optical device, light incident through the polarizing plate and the liquid crystal layer is reflected by the planar polarization beam splitter, and a reflection mode extracted through the liquid crystal layer, and from the light source. And a transmission mode in which the light is transmitted through the planar polarization beam splitter and is extracted through the liquid crystal layer.
This allows the display to be performed by reflecting light incident from the front of the liquid crystal layer by using external light such as natural light or indoor illumination light, and also by using light from the light source on the back side of the liquid crystal layer in a dark place. It is possible to perform a so-called transflective display in which display is performed by making the light incident on the layer. In this case, by switching between the reflection mode and the transmission mode according to the surrounding brightness, clear display can be performed even when the surroundings are dark while reducing power consumption.
[0012]
In this case, the electric field may not be applied to the liquid crystal layer in the reflection mode, or the electric field may be applied to the liquid crystal layer in the reflection mode.
In the former configuration, a so-called normally white area is displayed, in which an area in an electric field non-application state is displayed brightly and an area in an electric field applied state is displayed dark. In the latter configuration, the reverse is true, that is, normally black where the region in the no electric field application state is displayed dark and the region in the electric field application state is displayed bright.
[0013]
Here, in the former configuration, in the transmission mode, the liquid crystal layer is in an electric field applied state, so that light from the light source that has passed through the planar polarization beam splitter is extracted through the liquid crystal layer. , Normally black. Further, in the latter configuration, in the transmission mode, the liquid crystal layer is in a state where no electric field is applied, so that light from the light source that has passed through the planar polarization beam splitter is extracted through the liquid crystal layer. , Normally white. That is, in each of the above-described configurations, the brightness is normally reversed (the contrast is reversed) between the reflection mode and the transmission mode.
[0014]
In this case, for example, by changing the voltage applied to the liquid crystal layer between the reflection mode and the transmission mode, it is possible to maintain the same light and dark display state between the reflection mode and the transmission mode. Become.
[0015]
Further, in the above-described electro-optical device, it is preferable that a diffusion plate that diffuses light reflected by the planar polarization beam splitter is disposed between the liquid crystal layer and the planar polarization beam splitter.
The arrangement of the diffuser plate improves the characteristics of light reflected by the planar polarization beam splitter.
[0016]
An electronic apparatus according to another aspect of the invention includes the above-described electro-optical device as a display unit.
In this electronic device, the display contrast of the display means is improved.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail.
FIG. 1 schematically shows a configuration example of an electro-optical device according to the present invention. The electro-optical device 10 includes a liquid crystal layer 13 disposed between a pair of transparent substrates 11 and 12, and performs display via the liquid crystal layer 13.
[0018]
On each of the substrates 11 and 12, a TFT as an active element (not shown), a transparent electrode (ITO or the like), and an alignment film are formed, and their formation surfaces face each other with the liquid crystal layer 13 interposed therebetween. Are arranged. The alignment direction of the liquid crystal molecules included in the liquid crystal layer 13 is controlled according to the state of application of the electric field between the transparent substrates 11 and 12. In the example of FIG. 1, the twist (twist angle) of the arrangement of the liquid crystal molecules in a state where no electric field is applied is about 90 °. In addition, a liquid crystal cell 14 is configured to include the substrates 11, 12 and the liquid crystal layer 13. The twist angle of the liquid crystal may be 90 degrees when driving using an active element such as a TFT, but in the case of simple matrix driving without using an active element, the STN mode in which the liquid crystal is twisted to about 270 degrees is used. become. The present invention can be applied to STN.
[0019]
A light-absorbing polarizing plate 15 is disposed on the front side of the liquid crystal cell 14 and on the outer surface of the substrate 11. The polarizing plate 15 is formed by stretching and orienting a dichroic material such as iodine or an organic dye, and has absorption dichroism. That is, it absorbs the polarized light component in the same direction as the dichroic arrangement and transmits the other polarized light component.
[0020]
On the other side of the liquid crystal cell 14 and outside the substrate 11, a light source 20 as a backlight for emitting light to the liquid crystal cell 14 is arranged. Further, between the light source 20 and the liquid crystal cell 14, a diffusion plate 16, a planar polarization beam splitter 17, and a wavelength correction plate 18 are arranged in this order from the liquid crystal cell 14 side.
[0021]
The planar polarization beam splitter 17 separates incident light into transmitted light and reflected light by polarization using an optical phenomenon such as reflection or birefringence. For example, a transparent thin film having a different refractive index is used. Are laminated. In this example, the planar polarization beam splitter 17 is configured to reflect a polarized component in one direction of the incident light and transmit a polarized component orthogonal thereto. This characteristic functions for light incident from either the upper or lower side of the planar polarization beam splitter 17 in FIG.
[0022]
The diffusion plate 16 is disposed between the liquid crystal cell 14 and the planar polarization beam splitter 17, and has a function of diffusing incident light. Since the surface of the planar polarization beam splitter 17 is in a mirror state, the diffusion plate 16 is disposed adjacent to the plane polarization beam splitter 17 so that an external image is reflected on the plane polarization beam splitter 17. Is suppressed, and the optical quality is improved. Although the diffusion plate 16 is arranged adjacent to the plane-type polarization beam splitter 17, it may be arranged on the light extraction side with respect to the plane-type polarization beam splitter 17. It may be placed on top. With this configuration, reflection of external light on the surface of the display device can be prevented. In this case, the reflection can be further reduced by coating the surface of the diffusion plate with an anti-reflection coating. When the polarizing plate 15 is disposed on the most front side, an anti-reflection coating (anti-reflection treatment) may be applied to the surface of the polarizing plate 15.
[0023]
The wavelength correction plate 18 is disposed between the planar polarization beam splitter 17 and the light source 20, and has a function of giving a phase difference to incident light. In this example, a λ / 4 plate that gives a phase difference of １ ／ wavelength of visible light to incident light is used as the wavelength correction plate 18. The wavelength correction plate (λ / 4 plate) 18 is arranged in accordance with the direction of the polarization axis of the plane polarization beam splitter 17 so that the intensity of the light from the light source 20 transmitted through the plane polarization beam splitter 17 is maximized. Is done. Specifically, they are arranged so that the direction of the stretching axis of the wavelength correction plate (λ / 4 plate) 18 and the direction of the polarization axis of the planar polarization beam splitter 17 (the polarization axis for transmitted light) match. In the present invention, the wavelength correction plate 18 is only required to be able to change the polarization state of the incident light, and is not limited to a λ / 4 plate.
[0024]
In this example, the light source 20 is formed of an organic EL device having a configuration in which a light-emitting layer containing a light-emitting substance is sandwiched between anode and cathode electrode layers. In the organic EL device, holes injected from the anode side and electrons injected from the cathode side are recombined in the light emitting layer having a light emitting ability, and emit light when the excited state is lost.
[0025]
In this example, the organic EL device 20 includes a pixel electrode (anode) 22, a hole injection layer (hole transport layer) 23, a light emitting layer 24, and an electron transport layer on a transparent substrate 21 on which circuit elements such as TFTs are formed. It has a structure in which a layer 25, a counter electrode (cathode) 26, a sealing portion (not shown) and the like are sequentially laminated. The pixel electrode 22 is made of a transparent electrode such as ITO, and the counter electrode 26 is made of a reflective film such as a metal film. In the organic EL device 20, the light emitting layer 24 sandwiched between the pixel electrode 22 and the counter electrode 26 emits light by the drive control of the circuit element portion, and the light passes through the substrate 21 and is emitted toward the liquid crystal cell 14. You. Light emitted from the light emitting layer 24 toward the counter electrode 26 is reflected by the counter electrode 26, passes through the substrate 21, and is emitted toward the liquid crystal cell 14. The light-emitting layer 24 may be a light-emitting layer made of a white light-emitting material that emits white light, and includes a plurality of types of light-emitting layers corresponding to a plurality of colors such as R (red), G (green), and B (blue). May be.
[0026]
Here, in the organic EL device 20 of this example, the light emitted from the light emitting layer 24 is emitted from the pixel electrode 22 side, but the light emitted from the light emitting layer 24 may be emitted from the counter electrode 26 side. In this case, the counter electrode 26 is disposed so as to face the liquid crystal cell 14, and a transparent material is used as a material for forming the counter electrode 26. Further, a reflective film is used as the pixel electrode 22 or a reflective film is formed on the pixel electrode 22. In the present invention, the configuration of the organic EL device is not limited to the above. For example, the electron transport layer may be omitted.
[0027]
FIG. 2 is a diagram for explaining the display principle of the electro-optical device 10 described above.
The electro-optical device 10 according to the present embodiment includes a reflection mode in which display is performed by reflecting light incident from the front surface of the liquid crystal layer using external light such as natural light or indoor illumination light, and a back surface of the liquid crystal layer in a dark place. And a transmissive mode in which light from the light source on the side (in this example, the organic EL device) is incident on the liquid crystal layer to perform display, and so-called transflective display is performed. Therefore, by switching between the reflection mode and the transmission mode according to the brightness of the surroundings, it is possible to reduce the power consumption and perform a clear display even when the surroundings are dark.
[0028]
In the example of FIG. 2, the twist angle of the liquid crystal layer 13 is 90 ° as described above. Further, the axis direction of the polarization axis of the polarizing plate 15 and the axis direction of the polarization axis of the planar polarization beam splitter 17 (the polarization axis for transmitted light) are arranged in the same direction.
[0029]
In the reflection mode shown in FIG. 2, the polarization component of the external light is incident on the liquid crystal layer 13 via the polarizing plate 15. When the liquid crystal layer 13 is set in a state where no electric field is applied, the incident polarized light is twisted by 90 ° along the twist of the liquid crystal molecules, and is incident on the plane polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of the light is orthogonal to the axis of the polarization axis of the plane polarization beam splitter 17, the light is reflected by the plane polarization beam splitter 17, and passes through the liquid crystal layer 13 and the polarizing plate 15 again to be emitted.
[0030]
When the liquid crystal layer 13 is set to an electric field application state, the incident polarized light travels straight along liquid crystal molecules aligned in the direction of the electric field, and enters the plane polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of this light is the same as the direction of the polarization axis of the plane polarization beam splitter 17, it passes through the plane polarization beam splitter 17 and is attenuated by the wavelength correction plate 18 and the like.
[0031]
As described above, in the reflection mode shown in FIG. 2, when the liquid crystal layer 13 is in a state where no electric field is applied, light reflected by the planar polarization beam splitter 17 is extracted through the liquid crystal layer 13. In other words, in this case, a so-called normally white area is displayed in which the area in the state where no electric field is applied is brightly displayed and the area in the state where the electric field is applied is dark.
[0032]
On the other hand, in the transmission mode shown in FIG. 2, light is emitted from the organic EL device 20 as a light source toward the liquid crystal cell 14. Then, the light is incident on the planar polarization beam splitter 17 via the wavelength correction plate 18, and is separated into transmitted light and reflected light by polarized light. The light reflected by the planar polarization beam splitter 17 passes through the wavelength correction plate 18, is reflected by the counter electrode 26 (see FIG. 1) of the organic EL device 20, passes through the wavelength correction plate 18 again, and passes through the planar polarization beam. The light enters the splitter 17. This light passes through the wavelength correction plate 18 a plurality of times, and is repeatedly given a phase difference. As a result, the polarization component becomes the same as the direction of the polarization axis of the planar polarization beam splitter 17 and transmits through the planar polarization beam splitter 17. That is, almost all of the light emitted from the organic EL device 20 finally passes through the plane polarization beam splitter 17 and enters the liquid crystal cell 14 as polarized light.
[0033]
Subsequently, when the liquid crystal layer 13 is set in a state where no electric field is applied, the polarized light that has entered the liquid crystal layer 13 is twisted by 90 ° along the twist of the liquid crystal molecules, and enters the polarizing plate 15. This light is absorbed by the polarizing plate 15 because the polarization direction is orthogonal to the direction of the polarization axis of the polarizing plate 15. When the liquid crystal layer 13 is set to an electric field applied state, polarized light incident on the liquid crystal layer 13 travels straight along liquid crystal molecules aligned in the direction of the electric field, and is incident on the polarizing plate 15. This light passes through the polarizing plate 15 and exits because the polarization direction is the same as the direction of the polarization axis of the polarizing plate 15.
[0034]
That is, in the transmission mode shown in FIG. 2, light emitted from the organic EL device 20 is extracted through the liquid crystal layer 13 when the liquid crystal layer 13 is in an electric field applied state. In other words, in this case, a so-called normally black state is obtained, in which the region in the state where no electric field is applied is displayed dark and the region in the state where the electric field is applied is brightly displayed.
[0035]
In the electro-optical device 10 of this example, light from the light source (organic EL device 20) is polarized via the plane-type polarizing beam splitter 17, so that a light-absorbing polarizing plate is provided between the liquid crystal layer 13 and the light source. Even without the arrangement, the emission control of the light through the liquid crystal layer 13 can be performed. Further, since the light reflected by the planar polarization beam splitter 17 is reused and almost all light from the light source is used, the light use efficiency is high. Therefore, the contrast (display contrast) of the light emitted from the liquid crystal layer 13 is high.
[0036]
FIG. 3 shows a display state of the electro-optical device.
As described above, in the electro-optical device of the present example, in the reflection mode, the region in the state where no electric field is applied to the liquid crystal layer is displayed bright, the region in the state where the electric field is applied is displayed dark (normally white), and the transmission is performed. In the mode, the region in the state where no electric field is applied is displayed dark, and the region in the state where the electric field is applied is displayed bright (normally black). That is, the lightness and darkness are reversed (the contrast is reversed) between the reflection mode and the transmission mode.
[0037]
In this case, by changing the voltage applied to the liquid crystal layer between the reflection mode and the transmission mode and inverting the electric field control, it is possible to maintain the same light and dark display (contrast) between the reflection mode and the transmission mode. It becomes possible. That is, a region in which no electric field is applied in the reflection mode is set to an electric field application state in the transmission mode, and conversely, a region in which the electric field is applied in the reflection mode is set to an electric field non-application state in the transmission mode. Thus, the area displayed bright in the reflection mode is displayed bright even in the transmission mode, and the area displayed dark in the reflection mode is displayed dark also in the transmission mode.
[0038]
Further, in the electro-optical device of this example, an organic EL device is used as a light source (backlight) that emits light to the liquid crystal layer. Since the organic EL device emits light with high luminance and is suitable for thinning, the use of the organic EL device as a light source can reduce the thickness of the electro-optical device. Furthermore, since the organic EL device includes a plurality of types of light emitting layers each corresponding to a predetermined color, it is possible to change the color of light emitted from the liquid crystal layer.
[0039]
FIG. 4 is a diagram illustrating a configuration example of a light emitting layer of the organic EL device.
In FIG. 4, the light-emitting layer 24 includes three types of light-emitting layers 24a that emit R (red) light, light-emitting layers 24b that emit G (green) light, and light-emitting layers 24c that emit B (blue) light. , Which are arranged repeatedly in order. In the organic EL device 20 including the light emitting layer 24, white light can be emitted by causing all three types of light emitting layers 24a, 24b, and 24c of R, G, and B to emit light. Further, by causing only one kind of light emitting layer to emit light, light of a color corresponding to the light emitting layer can be emitted. Further, the color tone can be arbitrarily adjusted by changing the relative light emission intensity of the three types of light emitting layers. As described above, in the electro-optical device including the organic EL device 20 as a backlight, the color of light emitted from the liquid crystal layer can be changed, and display performance can be improved.
[0040]
FIG. 5 shows a modification of the electro-optical device 10 shown in FIG. In the example of FIG. 5, the axis direction of the polarization axis of the polarizing plate 15 and the axis direction of the polarization axis of the planar polarization beam splitter 17 (the polarization axis for transmitted light) are arranged in directions orthogonal to each other. The other configuration is the same as that of FIG. 2, and the twist angle of the liquid crystal layer 13 is 90 °.
[0041]
In the reflection mode shown in FIG. 5, the polarization component of the external light enters the liquid crystal layer 13 via the polarizing plate 15. When the liquid crystal layer 13 is set in a state where no electric field is applied, the incident polarized light is twisted by 90 ° along the twist of the liquid crystal molecules, and is incident on the plane polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of this light is the same as the direction of the polarization axis of the plane polarization beam splitter 17, it passes through the plane polarization beam splitter 17 and is attenuated by the wavelength correction plate 18 and the like.
[0042]
When the liquid crystal layer 13 is set to an electric field applied state, the incident polarized light travels straight along the liquid crystal molecules aligned in the direction of the electric field, and enters the plane-type polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of the light is orthogonal to the axis of the polarization axis of the plane polarization beam splitter 17, the light is reflected by the plane polarization beam splitter 17, and passes through the liquid crystal layer 13 and the polarizing plate 15 again to be emitted.
[0043]
That is, in the reflection mode shown in FIG. 5, when the liquid crystal layer 13 is in an electric field application state, light reflected by the planar polarization beam splitter 17 is extracted through the liquid crystal layer 13. In other words, in this case, a so-called normally black state is obtained in which the area in the no-electric-field application state is displayed dark and the area in the electric-field application state is displayed bright.
[0044]
On the other hand, in the transmission mode shown in FIG. 5, when the liquid crystal layer 13 is in a state where no electric field is applied, the polarized light incident on the liquid crystal layer 13 is twisted 90 ° along the twist of the liquid crystal molecules and is incident on the polarizing plate 15. This light passes through the polarizing plate 15 and exits because the polarization direction is the same as the direction of the polarization axis of the polarizing plate 15. When the liquid crystal layer 13 is set to an electric field applied state, polarized light incident on the liquid crystal layer 13 travels straight along liquid crystal molecules aligned in the direction of the electric field, and is incident on the polarizing plate 15. This light is absorbed by the polarizing plate 15 because the polarization direction is orthogonal to the direction of the polarization axis of the polarizing plate 15.
[0045]
That is, in the transmission mode shown in FIG. 5, when the liquid crystal layer 13 is in an electric field applied state, light emitted from the organic EL device 20 is extracted through the liquid crystal layer 13. In other words, in this case, a so-called normally white area is displayed in which the area in the state where no electric field is applied is brightly displayed and the area in the state where the electric field is applied is dark.
[0046]
As described above, the electro-optical device shown in FIG. 5 is normally black in the reflective mode and normally white in the transmissive mode, and the brightness of the display in each mode is reversed with respect to the electro-optical device 10 shown in FIG. In the electro-optical device shown in FIG. 5 as well, by changing the voltage applied to the liquid crystal layer between the reflection mode and the transmission mode and inverting the electric field control, the light-dark display between the reflection mode and the transmission mode is performed. (Contrast) can be kept the same.
[0047]
FIG. 6 shows another modification of the electro-optical device 10 shown in FIG. 2, which is provided with an STN type liquid crystal cell using a twist angle of 90 ° or more. In the example of FIG. 6, the liquid crystal cell includes a liquid crystal layer 53 including liquid crystal molecules whose alignment (twist angle) is about 270 ° when no electric field is applied. Further, the axis direction of the polarization axis of the polarizing plate 15 and the axis direction of the polarization axis of the planar polarization beam splitter 17 (the polarization axis for transmitted light) are arranged in the same direction. Note that components having the same functions as those already described are denoted by the same reference numerals, and description thereof will be omitted or simplified.
[0048]
In the reflection mode shown in FIG. 6, the polarization component of the external light enters the liquid crystal layer 53 via the polarizing plate 15. When the liquid crystal layer 53 is set in a state where no electric field is applied, the incident polarized light is twisted by 270 ° along the twist of the liquid crystal molecules, and is incident on the plane-type polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of the light is orthogonal to the direction of the polarization axis of the plane polarization beam splitter 17, the light is reflected by the plane polarization beam splitter 17, and passes through the liquid crystal layer 53 and the polarizing plate 15 again to be emitted.
[0049]
When the liquid crystal layer 53 is in an electric field application state, the incident polarized light travels straight along liquid crystal molecules aligned in the direction of the electric field, and enters the plane-type polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of this light is the same as the direction of the polarization axis of the plane polarization beam splitter 17, it passes through the plane polarization beam splitter 17 and is attenuated by the wavelength correction plate 18 and the like.
[0050]
As described above, in the reflection mode shown in FIG. 6, when the liquid crystal layer 53 is in a state where no electric field is applied, light reflected by the planar polarization beam splitter 17 is extracted through the liquid crystal layer 53. In other words, in this case, a so-called normally white area is displayed in which the area in the state where no electric field is applied is brightly displayed and the area in the state where the electric field is applied is dark.
[0051]
On the other hand, in the transmission mode shown in FIG. 6, light is emitted from the organic EL device 20, which is the light source, toward the liquid crystal cell. Then, the light enters the planar polarization beam splitter 17 via the wavelength correction plate 18 and is separated into transmitted light and reflected light by polarized light. The light reflected by the plane-type polarization beam splitter 17 passes through the wavelength correction plate 18, is reflected by the counter electrode 26 (see FIG. 1) of the organic EL device 20, passes through the wavelength correction plate 18 again, and passes through the plane-type polarization beam. The light enters the splitter 17. This light passes through the wavelength correction plate 18 a plurality of times, and is repeatedly given a phase difference. As a result, the polarization component becomes the same as the direction of the polarization axis of the planar polarization beam splitter 17 and passes through the planar polarization beam splitter 17. That is, almost all of the light emitted from the organic EL device 20 finally passes through the planar polarization beam splitter 17 and enters the liquid crystal cell as polarized light.
[0052]
Subsequently, when the liquid crystal layer 53 is set in a state where no electric field is applied, the polarized light incident on the liquid crystal layer 53 is twisted by 270 ° along the twist of the liquid crystal molecules, and is incident on the polarizing plate 15. This light is absorbed by the polarizing plate 15 because the polarization direction is orthogonal to the direction of the polarization axis of the polarizing plate 15. When the liquid crystal layer 53 is in an electric field application state, the polarized light that has entered the liquid crystal layer 53 travels straight along liquid crystal molecules that are aligned in the direction of the electric field, and enters the polarizing plate 15. This light passes through the polarizing plate 15 and exits because the polarization direction is the same as the direction of the polarization axis of the polarizing plate 15.
[0053]
That is, in the transmission mode shown in FIG. 6, the light emitted from the organic EL device 20 is extracted through the liquid crystal layer 53 when the liquid crystal layer 53 is in an electric field applied state. In other words, in this case, a so-called normally black state is obtained in which the area in the no-electric-field application state is displayed dark and the area in the electric-field application state is displayed bright.
[0054]
As described above, in the electro-optical device shown in FIG. 6, similarly to the electro-optical device shown in FIG. 2, the reflection mode is normally white and the transmission mode is normally black. In addition, since the liquid crystal cell of the STN type having a twist angle of 270 ° is provided, high contrast can be obtained. In the electro-optical device shown in FIG. 6 as well, by changing the applied voltage to the liquid crystal layer between the reflection mode and the transmission mode and inverting the electric field control, the light and dark display between the reflection mode and the transmission mode is performed. (Contrast) can be kept the same.
[0055]
FIG. 7 shows another modification of the electro-optical device 10 shown in FIG. 2, and includes an STN liquid crystal cell as in FIG. In the example of FIG. 7, the axis direction of the polarization axis of the polarizing plate 15 and the axis direction of the polarization axis of the planar polarization beam splitter 17 (the polarization axis for transmitted light) are arranged in directions orthogonal to each other. The other configuration is the same as that of FIG. 6, and the twist angle of the liquid crystal layer 53 is 270 °. Note that components having the same functions as those already described are denoted by the same reference numerals, and description thereof will be omitted or simplified.
[0056]
In the reflection mode shown in FIG. 7, the polarization component of the external light enters the liquid crystal layer 53 via the polarizing plate 15. When the liquid crystal layer 53 is set in a state where no electric field is applied, the incident polarized light is twisted by 270 ° along the twist of the liquid crystal molecules, and is incident on the plane-type polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of this light is the same as the direction of the polarization axis of the plane polarization beam splitter 17, it passes through the plane polarization beam splitter 17 and is attenuated by the wavelength correction plate 18 and the like.
[0057]
When the liquid crystal layer 53 is set to an electric field applied state, the incident polarized light travels straight along liquid crystal molecules aligned in the direction of the electric field, and enters the plane-type polarization beam splitter 17 via the diffusion plate 16. Since the polarization direction of the light is orthogonal to the direction of the polarization axis of the plane polarization beam splitter 17, the light is reflected by the plane polarization beam splitter 17, and passes through the liquid crystal layer 53 and the polarizing plate 15 again to be emitted.
[0058]
That is, in the reflection mode shown in FIG. 7, when the liquid crystal layer 53 is in an electric field application state, light reflected by the planar polarization beam splitter 17 is extracted through the liquid crystal layer 53. In other words, in this case, a so-called normally black state is obtained in which the area in the no-electric-field application state is displayed dark and the area in the electric-field application state is displayed bright.
[0059]
On the other hand, in the transmission mode shown in FIG. 7, when the liquid crystal layer 53 is in a state where no electric field is applied, the polarized light incident on the liquid crystal layer 53 is twisted 270 ° along the twist of the liquid crystal molecules and is incident on the polarizing plate 15. This light passes through the polarizing plate 15 and exits because the polarization direction is the same as the direction of the polarization axis of the polarizing plate 15. When the liquid crystal layer 53 is in an electric field application state, the polarized light that has entered the liquid crystal layer 53 travels straight along liquid crystal molecules that are aligned in the direction of the electric field, and enters the polarizing plate 15. This light is absorbed by the polarizing plate 15 because the polarization direction is orthogonal to the direction of the polarization axis of the polarizing plate 15.
[0060]
That is, in the transmission mode shown in FIG. 7, the light emitted from the organic EL device 20 is extracted through the liquid crystal layer 53 when the liquid crystal layer 53 is in an electric field applied state. In other words, in this case, a so-called normally white area is displayed in which the area in the state where no electric field is applied is brightly displayed and the area in the state where the electric field is applied is dark.
[0061]
As described above, the electro-optical device shown in FIG. 7 is normally black in the reflection mode and normally white in the transmissive mode, and the display brightness in each mode is reversed with respect to the electro-optical device shown in FIG. Further, as in the case of FIG. 6, a high contrast can be obtained by providing an STN type liquid crystal cell having a twist angle of 270 °. Also in the electro-optical device shown in FIG. 7, by changing the voltage applied to the liquid crystal layer between the reflection mode and the transmission mode and inverting the electric field control, the light-dark display between the reflection mode and the transmission mode is performed. (Contrast) can be kept the same.
[0062]
FIGS. 8A to 8C show an embodiment of an electronic apparatus according to the present invention.
The electronic apparatus of this example includes the electro-optical device of the present invention as a display.
FIG. 8A is a perspective view illustrating an example of a mobile phone. In FIG. 8A, reference numeral 1000 denotes a mobile phone main body, and reference numeral 1001 denotes a display unit using the above-described display device.
FIG. 8B is a perspective view illustrating an example of a wristwatch-type electronic device. In FIG. 8B, reference numeral 1100 denotes a watch main body, and reference numeral 1101 denotes a display unit using the display device.
FIG. 8C is a perspective view showing an example of a portable information processing device such as a word processor or a personal computer. 8C, reference numeral 1200 denotes an information processing device, reference numeral 1202 denotes an input unit such as a keyboard, reference numeral 1204 denotes an information processing device main body, and reference numeral 1206 denotes a display unit using the display device.
Since each of the electronic devices shown in FIGS. 8A to 8C includes the display device of the present invention as a display unit, a display with high display contrast and excellent quality can be realized.
[0063]
In the above-described embodiment, the liquid crystal cell may be a so-called STN liquid crystal cell using a twist angle of 90 degrees or more (addition: a twist of 90 degrees or more, in addition to a 90-degree twist). An active matrix method may be adopted.
Further, either color display or monochrome display may be used. In the case of supporting color display, a color filter may be provided in the liquid crystal cell.
Alternatively, color display may be performed by controlling the emission color of the organic EL device in accordance with driving of the liquid crystal cell (eg, a field sequential method).
Alternatively, color display and monochrome display may be switched between the reflection mode and the transmission mode. For example, monochrome display may be used in the reflection mode, and color display may be used in the transmission mode. In this case, color display in the transmission mode can be performed by controlling the emission color of the organic EL device.
The display of the organic EL device may be full-surface light emission as a backlight or pixel light emission capable of displaying pictures and characters.
[0064]
Further, as the planar polarization beam splitter, a layer having a refractive index isotropic formed of an inorganic compound and rubbed in a predetermined direction and a layer formed of an organic compound and having a refractive index anisotropy, a plurality of layers May be used alternately. In this laminate, for example, an inorganic layer rubbed in a specific direction and an organic layer formed on the inorganic layer are alternately laminated over a plurality of layers (several tens to hundreds of layers). Formed by A plurality of organic layers are laminated so that the rubbing directions are the same. With this configuration, the incident light transmits a polarized light component corresponding to the rubbing direction and reflects the remaining half polarized light component. As the inorganic layer, for example, a material having a refractive index isotropic translucency (for example, silicon nitride; Si ₃ N ₄ And the like are used. Further, as the organic layer, a light-transmitting material having a refractive index anisotropy in a specific direction (for example, the above-described liquid crystal organic compound) is used. Here, assuming that the glass transition temperature of the material forming the inorganic layer is Tg and the temperature of the material forming the organic layer forms the liquid crystal layer is TLC, these materials are selected so that the relationship of Tg> TLC is satisfied. You.
Further, a panel in which a cholesteric liquid crystal is sealed in a cell may be used as the flat polarization beam splitter.
[0065]
Further, as the wavelength correcting plate (λ / 4 plate), a layer obtained by laminating a plurality of layers of a liquid crystalline organic compound in which a chiral component is oriented in a predetermined direction by shifting the orientation direction of the chiral component by a predetermined angle is used. Is also good. This laminate is formed, for example, by laminating a liquid crystal organic compound having a thickness of about 5 μm and adding a chiral component to the layer so that the rubbing orientation direction is shifted by 90 °, and forming a film to a predetermined thickness. And solidifies by irradiating the same with a 同等 wavelength plate that twists the polarization direction of incident light by 45 °. As the liquid crystal organic compound, a liquid crystal acrylate monomer or a liquid crystal polymer can be used.
[0066]
Further, as a material of the transparent substrate, a transparent material such as plastic such as polyolefin, polyester, polyacrylate, polycarbonate, polyethersulfone, and polyetherketone can be used in addition to glass.
[0067]
As the material of the pixel electrode (anode), in addition to ITO (Indium Tin Oxide), aluminum (Al), gold (Au), silver (Ag), magnesium (Mg), nickel (Ni), and zinc (Ni). A simple substance such as vanadium (ZnV), indium (In), tin (Sn), a compound or a mixture thereof, or a conductive adhesive containing a metal filler is used. The formation of the pixel electrode is preferably performed by sputtering, ion plating, or a vacuum deposition method. Alternatively, the pixel electrode may be formed by printing using a spin coater, a gravure coater, a knife coater, or the like, screen printing, flexographic printing, or the like.
[0068]
As a method for forming the hole injection layer (hole transport layer), for example, a carbazole polymer and a TPD: triphenyl compound are co-evaporated to a thickness of 10 to 1000 nm (preferably 100 to 700 nm). Formed. As another formation method, the composition may be formed by, for example, discharging a composition ink containing a hole injection / transport layer material onto a substrate by an inkjet method, followed by drying treatment and heat treatment. As the composition ink, for example, an ink obtained by dissolving a mixture of a polythiophene derivative such as polyethylene dioxythiophene and polystyrene sulfonic acid in a polar solvent such as water can be used.
[0069]
The light emitting layer is formed by, for example, performing a drying treatment and a heat treatment after discharging a composition ink containing a material onto a substrate by an inkjet method. Examples of the light emitting material constituting the light emitting layer include a fluorene polymer derivative, a (poly) paraphenylenevinylene derivative, a polyphenylene derivative, a polyfluorene derivative, polyvinylcarbazole, a polythiophene derivative, a perylene dye, a coumarin dye, a rhodamine dye, In addition, a low molecular organic EL material, a high molecular organic EL material, or the like that is soluble in a benzene derivative can be used.
[0070]
Further, as the electron transport layer, for example, a metal complex compound formed of a metal and an organic ligand, preferably, Alq ₃ (Tris (8-quinolinolate) aluminum complex), Znq ₂ (Bis (8-quinolinolate) zinc complex), Bebq ₂ (Bis (8-quinolinolate) beryllium complex), Zn-BTZ (2- (o-hydroxyphenyl) benzothiazole zinc), a perylene derivative, or the like so as to have a thickness of 10 to 1000 nm (preferably 100 to 700 nm). What was deposited and laminated is used.
[0071]
The counter electrode (cathode) has, for example, a laminated structure. The lower cathode layer has a work function lower than that of the upper cathode layer so that electrons can be efficiently injected into the electron transport layer or the light emitting layer. A low metal such as calcium is used. The upper cathode layer protects the lower cathode layer and preferably has a work function relatively larger than that of the lower cathode layer. For example, aluminum or the like is used. The lower cathode layer and the upper cathode layer are preferably formed by, for example, a vapor deposition method, a sputtering method, a CVD method, and the like, and particularly preferably formed by a vapor deposition method to prevent the light emitting layer from being damaged by heat, ultraviolet rays, electron beams, and plasma. It is preferable because it can be performed.
[0072]
As described above, the preferred embodiments according to the present invention have been described with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. The shapes, combinations, and the like of the constituent members shown in the above-described examples are merely examples, and can be variously changed based on design requirements and the like without departing from the gist of the present invention.
[Brief description of the drawings]
FIG. 1 is a diagram schematically illustrating a configuration example of an electro-optical device according to the invention.
FIG. 2 is a view for explaining a display principle of the electro-optical device of FIG. 1;
FIG. 3 is a view showing a display state of the electro-optical device of FIG. 1;
FIG. 4 is a diagram showing a configuration example of a light emitting layer of an organic EL device.
FIG. 5 is a diagram showing a modification of the electro-optical device of FIG.
FIG. 6 is a diagram showing a modification of the electro-optical device of FIG.
FIG. 7 is a diagram showing a modification of the electro-optical device of FIG.
8A is a diagram illustrating an example in which the electronic device of the present invention is applied to a mobile phone, FIG. 8B is a diagram illustrating an example in which the electronic device is applied to a wristwatch-type electronic device, and FIG. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Electro-optical device, 13, 53 ... Liquid crystal layer, 14 ... Liquid crystal cell, 15 ... Polarizing plate, 16 ... Diffusion plate, 17 ... Planar polarization beam splitter, 18 ... Wavelength correction plate, 20 ... Organic EL device (light source) , 24 ... light emitting layer.

Claims (10)

A polarizing plate,
A light source,
A liquid crystal layer including liquid crystal molecules including liquid crystal molecules, disposed between the polarizing plate and the light source,
An electro-optical device, comprising: a planar polarization beam splitter disposed between the liquid crystal layer and the light source and separating incident light into transmitted light and reflected light. The electro-optical device according to claim 1,
An electro-optical device, comprising: a wavelength correction plate that is disposed between the planar polarization beam splitter and the light source and that gives a phase difference to light. The electro-optical device according to claim 1 or 2,
An electro-optical device, wherein the light source includes an organic EL device. The electro-optical device according to claim 3,
The electro-optical device according to claim 1, wherein the organic EL device includes a plurality of types of organic EL elements having different emission colors. The electro-optical device according to any one of claims 1 to 4,
A reflection mode in which light incident through the polarizing plate and the liquid crystal layer is reflected by the planar polarization beam splitter and extracted through the liquid crystal layer,
An electro-optical device, comprising: a transmission mode in which light from the light source passes through the planar polarization beam splitter and is extracted through the liquid crystal layer. The electro-optical device according to claim 5,
An electro-optical device, wherein no electric field is applied to the liquid crystal layer in the reflection mode. The electro-optical device according to claim 5,
In the reflection mode, an electric field is applied to the liquid crystal layer. The electro-optical device according to claim 5,
An electro-optical device, wherein a voltage applied to the liquid crystal layer is changed between the reflection mode and the transmission mode. The electro-optical electro-optical device according to any one of claims 1 to 8,
An electro-optical device, comprising: a diffusing plate disposed between the liquid crystal layer and the planar polarization beam splitter to diffuse light reflected by the planar polarization beam splitter. An electronic apparatus comprising the electro-optical device according to claim 1 as a display unit.

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