This invention relates to an illuminator for illuminating a display member, a display device provided with a display member illuminator, and an appliance provided with a display device.
In recent years, a wide variety of functions are given to highly sophisticated appliances, for example, office automation appliances such as copying machine, printer, and desk-upper computer, optical appliances such as camera, audio appliances, video appliances, television sets, video game machines, and the like. In these appliances, an LCD (liquid crystal display) member has been generally used to display an operative state of the appliance in letters and figures. Also, there has been recently proposed use of PLZT (lead lanthanum zirconate titanate) as a display member for such appliances.
However, such display members do not emit light themselves. Accordingly, when a display device provided with such display member is used in dark, e.g., at night, a display image cannot be visually recognized. For this reason, there is usually provided a display member illuminator for illuminating the front or rear surface of a display member such as LCD member.
FIG. 9 shows a conventional display device. This display device includes an LCD member 30 and an LCD illuminator for illuminating the LCD member. The LCD illuminator includes an electroluminesent member 80 provided at a back of the LCD member 30 to supply light to the LCD member 30 and a drive circuit 90 for supplying a high voltage to the electroluininesent member 80. The electroluminesent member 80 emits light to illuminate the LCD member 30 uniformly. A specified image appears and disappears on the surface of the LCD member 30 in accordance with application of a drive voltage to transparent electrodes of the LCD member.
However, the electroluminesent member 80 requires an alternating current having a high voltage to emit light, inevitably making the size of the drive circuit 90 undesirably large. Thus, it has been very difficult to mount the LCD display device provided with such electroluminesecent illuminator on highly sophisticated appliances, such as a camera, which need a compact construction.
FIG. 10 shows another conventional display device. In this display device, an LCD member 30 is placed over a light guiding member 40 made of glass having substantially the same size as the LCD member 30. A light emitting member 50 including an LED (light emitting diode) is provided on one side end of the light guiding member 40. Light from the light emitting member 50 incident on the light guiding member 40 is diffused in the member 40, and is supplied to the LCD member 30 through the top surface of the member 40. Accordingly, the LCD member 30 is uniformly illuminated by the light having passed through the member 40. Since the LED can emit light upon a very small electric power, it is not necessary to provide a large drive circuit as in the above-mentioned LCD illuminator. Japanese Unexamined Utility Model Publication Nos. 56-52788, 4-40269, and 6-25802 disclose a display device provided with such LCD illuminator.
However, the light from the light emitting member 50 is incident only on the light guiding member 40 through its end surface, and is supplied to the LCD member 30 after being diffused in the light guiding member 40. Accordingly, in order to obtain a large amount of illuminating light, the light guiding member 40 needs to have a large thickness. This makes the combined size of the LCD illuminator and the display device larger. Accordingly, it has been very difficult to mount the display device provided with such LCD illuminator on compact highly sophisticated appliances.
FIG. 11 shows still another conventional display device. In this display device, there is provided an illuminator including a frame 60 for supporting an LCD member 30 and a plurality of LEDs 51 arranged in an illumination chamber 60a of the frame 60 beneath the LCD. The inner wall surfaces 60b of the illumination chamber 60a that tapers toward the lower act as a reflector. The light emitted from the LEDs is gathered and diffused upon being reflected by the reflector 60b, and then is incident on the LCD member 30. A display device of this type is disclosed in Japanese Unexamined Utility Model Publication No. 60-150585 and Japanese Unexamined Patent Publication No. 2-53040.
However, the illumination chamber 60a formed with the reflector 60b is provided below the LCD member 30. This makes the entire size of the LCD illuminator larger. Thus, similar to the above-mentioned conventional display devices of FIGS. 9 and 10, it has been difficult to mount the display device provided with such illuminator on compact highly sophisticated appliances.
Further, Japanese Unexamined Patent Publication No. 2-47630 discloses a display device provided in a viewfinder of a camera. In this device, an LCD member includes an LC (liquid crystal) cell and upper and lower plates sandwiching the cell. A light emitting member is attached on one side end of the LCD member. Illuminating light is introduced from the light emitting member into the upper and lower plates to illuminate the LC cell.
This display device is used in the viewfinder of a camera that has a small viewing area. The viewing area is not larger than 1 cm.sup.2, which thus does not require a large amount of illuminating light. Accordingly, such LCD illuminator cannot be used for a display device having a large viewing area which requires a large amount of light.