JP4289583B2 - Reflective and transmissive liquid crystal display - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reflective / transmissive liquid crystal display device, and more particularly to a reflective / transmissive liquid crystal display device capable of bright display in a bright place or a dark place.
[0002]
[Prior art]
A light guide plate is used for a front light and a backlight of a liquid crystal display device. The light guide plate for backlight can improve uniformity by a scattering plate or the like, but in the case of the light guide plate for front light, it is necessary to be transparent in order to observe the display surface through the light guide plate.
[0003]
In Japanese Patent Application Laid-Open No. 11-109338, the present applicant provides a reflection or transmission hologram on one surface of a light guide plate that propagates light while repeating total reflection as a front light guide plate of a reflective liquid crystal display device. A light guide plate with a hologram for emitting propagating light as illumination light to the outside has been proposed.
[0004]
The use of such a light guide plate as a light guide plate for a backlight of a transmissive liquid crystal display device has also been proposed in Japanese Patent Application No. 2000-319260.
[0005]
[Problems to be solved by the invention]
However, the light guide plate as described above is used as a light guide plate for backlight, and as a reflection type liquid crystal display device using outside light in a place where the surroundings are bright, illumination by the backlight light guide plate is used in a place where the surroundings are dark. A device that functions as a conventional transmissive liquid crystal display device has not been known.
[0006]
The present invention has been made in view of such problems in the prior art, and the purpose of the present invention is to use a light guide plate with a hologram as a light guide plate for backlight, so that a bright display can be obtained in a bright place or a dark place. It is an object of the present invention to provide a possible reflective / transmissive liquid crystal display device.
[0007]
[Means for Solving the Problems]
The reflective and transmissive liquid crystal display device of the present invention that achieves the above object is a liquid crystal comprising a liquid crystal layer that is sandwiched between a pixel electrode and a common electrode divided for each pixel and the transmittance can be controlled for each pixel. In a liquid crystal display device provided with a display element,
A light guide plate with a deflecting element is disposed on the back side of the liquid crystal display element via a gap or a low refractive index layer, and a directional reflection layer is disposed on the back side of the liquid crystal display element via a gap or a low refractive index layer. And
The light guide plate with a deflection element comprises a light guide plate with a hologram, and the light guide plate with a hologram includes a transparent plate-like body, a hologram is provided on one surface thereof, and a light source disposed in the vicinity of one end of the plate-like body. The introduced light is propagated while being repeatedly totally reflected in the plate-like body, and a part of the propagated light is configured to be diffracted by the hologram to the back side of the transparent plate-like body,
Light that is introduced from the light source and is diffracted to the back side by the hologram and incident on the directional reflection layer, and incident on the liquid crystal display device from the same direction as the diffracted light, and the liquid crystal display element and the light guide plate with hologram The external light that has passed through is reflected and diffracted toward the liquid crystal display element by the directional reflective layer.
[0009]
In this case, the hologram may be a transmission hologram or a reflection hologram.
[0010]
In the present invention, a light guide plate with a deflecting element is disposed on the back side of the liquid crystal display element via a gap or a low refractive index layer, and further, a directional reflection is provided on the back side thereof via a gap or a low refractive index layer. The light guide plate with a deflection element is provided with a transparent plate-like body, the deflection element is provided on one surface thereof, and light introduced from a light source arranged in the vicinity of one end of the plate-like body. Since it is propagated while being repeatedly totally reflected in the plate-like body, and a part of the propagated light is deflected to the back side of the transparent plate-like body by the deflecting element, it has a simple configuration. In a bright place, it can be operated as a bright reflective liquid crystal display device that uses external light without using a light source. In a dark place, the light source is turned on as a bright transmissive liquid crystal display device. It can be operated.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a reflective / transmissive liquid crystal display device according to the present invention will be described based on examples.
[0012]
FIG. 1 is a cross-sectional view showing a configuration of a reflective / transmissive liquid crystal display device according to one embodiment, and FIG. 2 is a conceptual diagram of the reflective / transmissive liquid crystal display device. As the liquid crystal display element 10 of this reflective / transmissive liquid crystal display device, for example, a liquid crystal layer 11 such as twisted nematic is sandwiched between a transparent glass substrate 12 on the observation side and a transparent glass substrate 13 on the opposite side. A uniform transparent counter electrode 14 made of a black matrix (not shown) and ITO or the like is provided on the inner surface of the transparent glass substrate 12 on the observation side, and on the inner surface of the transparent glass substrate 13 on the opposite side to the observation side. Are provided with a color filter 16 composed of three colors of RGB and a transparent pixel electrode 15 provided independently for each pixel and provided with a TFT. Further, an alignment layer (not shown) is provided on the liquid crystal layer 1 side of the electrodes 14 and 15. Then, polarizing plates 17 and 18 are respectively attached to the outer surfaces of the transparent glass substrates 12 and 13, and for example, their transmission axes are arranged so as to be orthogonal to each other.
[0013]
And based on this invention, the light guide plate 1 with a hologram is arrange | positioned through the very thin space | gap or the low refractive index layer in the back side of the liquid crystal display element 10. FIG. The hologram light guide plate 1 includes a transparent plate-like body 2 made of plastic or the like, and a transmission hologram 3 is disposed in close contact with or adhered to the back side thereof. Similar to the transmission hologram disclosed in Japanese Patent Application Laid-Open No. 11-109338, the transmission hologram 3 guides light that is guided in the transparent plate 2 and is incident on the transmission hologram 3 at a predetermined angle greater than the critical angle. The diffracted light 6 is diffracted as a diffracted light 6 at an oblique emission angle that forms an angle θ with respect to the normal line of the transmission hologram 3 to the outside of the back surface of the shaped body 2. The diffraction efficiency of the transmission hologram 3 is set lower as it gets closer to the light source 4 on average, and is set higher as the distance from the light source 4 increases. For details, see JP-A-11-109338. In any case, the diffraction efficiency of the transmission hologram 3 is smaller than 100%.
[0014]
On the back side of the hologram light guide plate 1, a directional reflection layer 19 is disposed via a very thin gap or a low refractive index layer. One such directional reflective layer 19 is a reflection hologram that reflects and diffracts obliquely incident diffracted light 6 as diffusive reflected light 6 ′ in a substantially front direction. Such reflection type holograms are known, for example, in JP-A-11-125707 and JP-A-11-352329. Instead, a reflection type computer generated hologram having similar characteristics (Japanese Patent Application Laid-Open Nos. 11-183716, 11-296054, Japanese Patent Application No. 2000-159914) or a white diffuser (Japanese Patent Application No. 2000-309334). May be used. In addition, the same action can be achieved by using a reflecting mirror 19 'having a sawtooth cross section as shown in FIG.
[0015]
Since it is such a structure, when the light source 4 arranged facing one end of the transparent plate-like body 2 is turned on, the illumination light 5 is introduced into the transparent plate-like body 2, and the surface of the transparent plate-like body 2 The light is guided toward the other end of the transparent plate-like body 2 while repeating total reflection between the air of the transmission type hologram 3 that is in close contact with or adhered to the rear surface or the interface with the low refractive index layer. Since the transmission hologram 3 has the above-described configuration, an angle component satisfying the diffraction condition of the transmission hologram 3 in the illumination light 5 is diffracted by the transmission hologram 3 during the light guide, and the oblique diffraction light 6 Is diffracted to the back side. The diffracted light 6 is reflected and diffracted as reflected light 6 ′ directed substantially in the front direction by the directional reflection layer 19 disposed close to the transmissive hologram 3, and the reflected light 6 ′ is diffracted by the transmissive hologram 3 this time. Without passing through the light guide plate 1 with hologram, the liquid crystal display element 10 is illuminated uniformly from the back side. The light is spatially modulated by each pixel of the liquid crystal display element 10 to become display light 6 ″ and reaches the observer's eye E, and a bright display is possible by a combination of modulation states of each pixel.
[0016]
On the other hand, when there is external light 7 incident in the same direction as the diffracted light 6 in a bright environment, the external light 7 undergoes spatial modulation by each pixel of the liquid crystal display element 10 toward the light guide plate 1 with hologram. The light passes through the transparent plate-like body 2 and partly passes through the light guide plate with hologram 1 without being diffracted by the transmission hologram 3, and the transmitted light is reflected by the directional reflection layer 19 in a substantially front direction. Reflected and diffracted as light 7 ', the reflected light 7' is transmitted through the light guide plate 1 with hologram without being diffracted by the transmission hologram 3, and uniformly illuminates the liquid crystal display element 10 from the back side. Each pixel of the liquid crystal display element 10 is subjected to spatial modulation and becomes display light 7 ″ to reach the observer's eye E, and a bright display is possible by a combination of the modulation states of each pixel.
[0017]
As described above, the reflection / transmission type liquid crystal display device of the present invention has a simple configuration in which only a light guide plate with a hologram is added, and bright reflection using outside light without using a light source in a bright place. In a place where the surroundings are dark, the light source can be lit to operate as a bright transmissive liquid crystal display device.
[0018]
The reflective / transmissive liquid crystal display device of the present invention has been described based on the embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made. Further, as the light guide plate 1 with a hologram, instead of the transmission hologram 3 being adhered or adhered to the back surface of the transparent plate-like body 2, a reflection hologram is adhered or adhered to the front surface thereof, The light 5 guided while repeating total reflection may be diffracted by a reflection hologram during that time and emitted to the back side of the transparent plate 2 to be used as illumination light. For details, see JP-A-11-109338. Furthermore, instead of the transmission hologram 3, a relief type or volume type diffraction grating may be used, and further, a microprism array may be used.
[0019]
【The invention's effect】
As is clear from the above description, according to the reflective / transmissive liquid crystal display device of the present invention, the light guide plate with a deflecting element is disposed on the back side of the liquid crystal display element via a gap or a low refractive index layer, Further, a directional reflection layer is disposed on the back side through a gap or a low refractive index layer, the light guide plate with a deflection element includes a transparent plate-like body, and a deflection element is provided on one surface thereof. Light introduced from a light source arranged in the vicinity of one end of the plate-like body is propagated while being repeatedly totally reflected in the plate-like body, and a part of the propagated light is transmitted to the transparent plate-like body by the deflector element. Since it is configured to be deflected to the back side, it can be operated as a bright reflective liquid crystal display device using outside light without using a light source in a simple configuration and in a place where the surroundings are bright, In a dark place, turn on the light source. It can be operated as a light transmissive type liquid crystal display device.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a configuration of a reflective / transmissive liquid crystal display device according to an embodiment of the present invention.
FIG. 2 is a conceptual diagram of the reflective / transmissive liquid crystal display device of FIG.
FIG. 3 is a cross-sectional view showing a configuration of a cross-sectional sawtooth reflector that can be used as a directional reflective layer.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Light guide plate 2 with a hologram ... Transparent plate-shaped body 3 ... Transmission hologram 4 ... Light source 5 ... Illumination light 6 ... Diffracted light 6 '... Reflected light 6 "... Display light 7 ... External light 7' ... Reflected light 7" ... Display light 10 ... Liquid crystal display element 11 ... Liquid crystal layers 12, 13 ... Transparent glass substrate 14 ... Transparent counter electrode 15 ... Transparent pixel electrode 16 ... Color filters 17, 18 ... Polarizing plate 19 ... Directional reflective layer

Claims (3)

In a liquid crystal display device including a liquid crystal display element including a liquid crystal layer sandwiched between a pixel electrode and a common electrode divided for each pixel and capable of controlling the transmittance for each pixel,
A light guide plate with a deflecting element is disposed on the back side of the liquid crystal display element via a gap or a low refractive index layer, and a directional reflection layer is disposed on the back side of the liquid crystal display element via a gap or a low refractive index layer. And
The light guide plate with a deflection element comprises a light guide plate with a hologram, and the light guide plate with a hologram includes a transparent plate-like body, a hologram is provided on one surface thereof, and a light source disposed in the vicinity of one end of the plate-like body. The introduced light is propagated while being repeatedly totally reflected in the plate-like body, and a part of the propagated light is configured to be diffracted by the hologram to the back side of the transparent plate-like body ,
Light that is introduced from the light source and is diffracted to the back side by the hologram and incident on the directional reflection layer, and incident on the liquid crystal display device from the same direction as the diffracted light, and the liquid crystal display element and the light guide plate with hologram A reflection-type and transmission-type liquid crystal display device, wherein external light that has passed through is reflected and diffracted toward the liquid crystal display element by the directional reflection layer. Reflective and transmissive type liquid crystal display device according to claim 1, wherein said hologram comprises a transmission type hologram. Reflective and transmissive type liquid crystal display device according to claim 1, wherein the hologram is characterized by comprising the reflection-type hologram.

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