The present invention relates generally to a liquid crystal display device, and more specifically to a liquid crystal display device using a hologram diffuse plate. The present invention is also concerned with a hologram scatter plate used for liquid crystal display devices, etc., and process of replicating a such a diffuse reflection type hologram.
Referring here to a direct-view type of liquid crystal display device, a scatter plate 12 is generally located on the side of a liquid crystal display element 20 opposite to a backlight 11 to diffuse light emanating therefrom, as shown in FIG. 18, thereby widening a range capable of viewing an image displayed thereon (a visual field range).
A problem with this system is, however, that the efficiency of utilization of light is not high due to the use of a general scatter plate formed of frosted glass, and the angle of field is limited as well. The angle of field may be made wide by use of a plurality of scatter plates, but this offers a problem or gives rise to some considerable luminance drop.
A self-luminous type backlight consumes very large power, and brings about some considerable battery driving time reduction when used with laptop type computers, etc.
In view of such problems associated with the prior art, an object of the present invention is to provide a liquid crystal display device which has a wide visual field range and reduced luminance drops, so that bright displayed images can be presented.
Another object of the present invention is to provide a liquid crystal display device which uses a diffuse reflection type hologram for backlighting so that bright displays can be presented in the light without recourse to any self-luminous backlight. Yet another object of the present invention is to provide a liquid crystal display device which can be used in combination with a self-luminous type backlight, so that battery life can be extended by turning off the self-luminous type backlight or using the self-luminous type backlight at a reduced luminance.
A further object of the present invention is to provide a hologram scatter plate enabling bright displayed images to be presented over a wide range of wavelengths and viewing angle hardly achievable with conventional hologram systems.
A still further object of the present invention is to provide a process of fabricating, by replication, a large diffuse reflection type hologram without joints or recorded joints, which is compatible with increased size and improved quality in connection with backlights, projector screens, combiners, etc. for liquid crystal display devices.
To accomplish the aforesaid objects, the present invention provides a liquid crystal display device using a hologram, characterized in that a liquid crystal display element is provided on a display surface side thereof with a diffuse transmission type hologram capable of diffusing and transmitting light incident from a specific direction only in a direction defined as a viewing region.
In this case, a scatter plate may be located between the liquid crystal display element and a backlight.
The present invention also provides a liquid crystal display device using a hologram, characterized in that between a liquid crystal display element and a backlight there is located a diffuse transmission type hologram capable of diffusing and transmitting light incident from a specific direction only in a direction defined as a viewing region.
In these cases, it is desired that the diffuse transmission type hologram has a property of diffusing and transmitting light only in a direction defined as a viewing region within a plurality of wavelength regions of different colors.
Further, the present invention provides a liquid crystal display device using a hologram, characterized in that a liquid crystal display element is provided on a back surface side thereof opposite to a display surface side thereof with a diffuse reflection type hologram capable of diffusing and reflecting light incident from a specific direction only in a direction defined as a viewing region.
In this case, a diffuse reflection plate or a reflector plate may be located on the back surface side of the diffuse reflection type hologram.
When a TN liquid crystal cell is used as the liquid crystal display element, the diffuse reflection type hologram enables diffuse reflection to occur within a range wherein the contrast of the liquid crystal cell is at least 2. When an STN liquid crystal cell is used as the liquid crystal display element, the diffuse reflection type hologram enables diffuse reflection to occur within a range wherein the contrast of the liquid crystal cell is at least 2.
More illustratively, when a TN liquid crystal cell is used as the liquid crystal display element, it is desired that the diffuse reflection type hologram enable light incident thereon from above and at an angle of about 20xc2x0 with respect to a normal line thereof to be diffused and reflected within a range defined by an upward angle about 10xc2x0, a downward angle of about 40xc2x0, and breadth-wise angles of about 60xc2x0. When an STN liquid crystal cell is used as the liquid crystal display element, it is desired that the-diffuse reflection type hologram enable light incident thereon from above and at an angle of about 20xc2x0 with respect to a normal line thereof to be diffused and reflected within a range defined by an upward-angle about 20xc2x0, a downward angle of about 30xc2x0, and breadth-wise angles of about 30xc2x0.
A self-luminous type backlight unit may be located on the back surface side of the diffuse reflection type hologram.
To accomplish the aforesaid objects, the present invention provides a hologram scatter plate which reflects incident light in a direction different from a direct reflection direction thereof, characterized in that a transmission type hologram layer and a back side layer are stacked together in the described order as viewed from an incident side thereof.
In accordance with this aspect, there are three cases where the transmission type hologram layer has both a diffusion function and a diffraction function while the back side layer is a mirror reflection layer; the transmission type hologram layer has diffraction function while the back side layer has a diffuse reflection function; and the transmission type hologram layer has both a diffusion function and diffraction function while the back side layer has diffuse reflection function.
The transmission type hologram layer used may have a diffraction function, or a diffusion function and diffraction function, with respect to a plurality of different wavelengths.
The present invention also includes a liquid crystal display device having any one of the aforesaid hologram scatter plates located on a back surface side of a liquid crystal display element.
To accomplish the aforesaid objects, the present invention further provides a diffuse reflection type hologram replication process, characterized in that while a photosensitive material film is slid on a fixed diffuse reflection type hologram plate in contact relation thereto, the hologram plate is irradiated from the photosensitive material film with a light beam of linear shape in section that becomes wide in a widthwise direction of the film, so that a diffuse reflection type hologram can be continuously recorded in the photosensitive material film by interference of the incident light beam with a light beam reflected and diffracted by the diffuse reflection type hologram plate.
In this case, it is preferable that the diffuse reflection type hologram plate is fixed on the surface of a transparent rod-like member rounded at least both edges thereof. Such a transparent rod-like member may be exemplified by a semicylindrical member.
It is also desired that a combined index matching and lubricating liquid be contained between the diffuse reflection type hologram plate and the photosensitive material film.
The light beam of linear shape in section used may be exemplified by a light beam that diverges in its linear direction alone.
According to one inventive liquid crystal display device using a hologram wherein on a display surface side of a liquid crystal display element or between a liquid crystal display element and a backlight there is provided a diffuse transmission type hologram capable of diffusing and transmitting light incident from a specific direction only in a direction defined as a viewing region, it is possible to make wide a visual field region where displayed images can be observed and reduce luminance drops, so that bright displayed images can be presented.
According to another inventive liquid crystal display device using a hologram wherein on a back surface side of a liquid crystal display element opposite to a display surface side thereof there is provided a diffuse reflection type hologram capable of diffusing and reflecting light incident from a specific direction only in a direction defined as a viewing region as mentioned above, it is possible to present bright displays in the light without recourse to any self-luminous type backlight.
According to the inventive hologram scatter plate wherein a transmission type hologram layer and a back side layer are stacked together in the described order, it is possible to limit the direction of diffraction and scattering by means of the transmission hologram and increase reflectance over a wide wavelength region by means of the back side layer, so that diffused light having high luminance can be obtained over a wide wavelength and viewing angle range, making bright displays, etc. possible.
According to the inventive diffuse reflection type hologram replication process wherein while a photosensitive material film is slid on a fixed diffuse reflection type hologram plate in contact relation thereto, the hologram plate is irradiated from the photosensitive material film with a light beam of linear shape in section that becomes wide in a widthwise direction of the film, so that a diffuse reflection type hologram can be continuously recorded in the photosensitive material film by interference of the incident light beam with a light beam reflected and diffracted by the diffuse reflection type hologram plate, it is possible to easily fabricate, with no need of using any large hologram plate, a large yet continuous film form of diffuse reflection type hologram without joints or recorded joints, which has high reflectance and quality, and so is best suited for use with backlights, projector screens, combiners, etc. for liquid crystal display devices.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims.