Display device with coordinate input function

Abstract: In a display device with coordinate input function according to the invention, since transparent electrodes for inputting coordinates, are disposed in an X-Y matrix form on a compensation cell provided to a liquid crystal display panel of two-layer type, the coordinate input can be performed even in the case of employing a liquid crystal display panel divided into two, upper and lower parts to drive its display screen.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a display device with coordinate input function by which man-machine interface is performed between an electronic computer and its operator. Description of the Prior Art In the prior art, a liquid crystal display device with coordinate input function is disclosed, for example, in JP-A-262835/1986 or JP-A-81521/1988. FIG. 1 is a constitution diagram of a display device with coordinate input function in an example of the prior art. Also FIG. 2 is a sectional view of a liquid crystal display cell. In FIGs. 1 and 2, reference numeral 1 designates a liquid crystal display cell where a liquid crystal 10 is sealed between two glass substrates 12, 13, numerals 2 and 3 designate transparent electrodes arranged with a definite distance on the glass substrates 12, 13, numerals 4 and 5 designate drive circuits to activate the transparent electrodes 2, 3, numeral 6 designates a control circuit, numeral 7 designates a magnetic field sensor, numeral 8 designates an amplifier to amplify output signals of the magnetic field sensor 7, numeral 11 designates a seal substance to seal the liquid crystal 10 between the glass substrates 12, 13, and numerals 14 and 15 designate polarizing plates. Next, operation will be described. The control circuit 6 supplies an AC signal as a coordinate input detection signal in time sharing with a display drive signal through the drive circuits 4, 5 in sequence to the transparent electrodes 2, 3 arranged on the glass substrates 12, 13 of the liquid crystal display cell 1. As a result, a rotating magnetic field is generated on the periphery of each of the transparent electrodes 2, 3 by the coordinate input detection signal current. If the sensor 7 with a material having electromagnetic induction effect characteristics embedded therein comes close to the field, a detection voltage corresponding to the rotating magnetic field is obtained from the sensor 7. The detection voltage is amplified by the amplifier 8 to a suitable amplitude and then compared in sequence in synchronism with timing of the coordinate input detection signal applied to the transparent electrodes 2, 3, thereby an intersection position of the transparent electrodes 2 and 3 can be detected. The display device with coordinate input function in the above-mentioned constitution is advantageous in that display of the image and the coordinate input can be realized by the same transparent electrodes 2, 3 and a special coordinate input panel is not required. Since the display device with coordinate input function in the prior art is constituted as above described and the coordinate input detection signal current flows through the transparent electrodes, basically, the transparent electrodes 2, 3 must not have a non-conductive part there along. However, liquid crystal display devices in recent years are growing higher resolution, and in order to prevent deterioration in the contrast ratio of the display image, a liquid crystal display panel having a display screen divided into two, upper and lower parts to drive separately is used. Liquid crystal display panels are being significantly advanced, and a liquid crystal display panel of two-layer type to enable the black-and-white display is put to practical use in recent years and also a color liquid crystal display panel in combination of the liquid crystal display panel of two-layer type with a color filter has been developed. FIG. 3 is a sectional view of a standard liquid crystal display panel of two-layer type in the prior art, and FIG. 4 is a constitution diagram of a liquid crystal display panel divided into two, upper and lower parts in the prior art. In FIGs. 3 and 4, reference numeral 1 designates a liquid crystal display cell, numerals 2U, 2L and 3 designate transparent electrodes, numerals 4U, 4L and 5 designate drive circuits, numeral 6 designates a control circuit, and numeral 21 designates a liquid crystal cell for phase compensation, which is constituted by sealing a liquid crystal 10 between glass substrates 32 and 33 with a seal substance 31 and compensates optical characteristics of the liquid crystal display panel 1. Since details of the principle or the like of the liquid crystal panel of two-layer type shown in FIG. 3 do not have direct relation to the invention, the description shall be omitted here. As clearly seen from FIG. 4, each of the transparent electrodes arranged in the vertical direction is divided into an upper transparent electrode 2U and a lower transparent electrode 2L corresponding to the dividing of the display screen. In this case, the bottom end of the upper transparent electrode 2U and the top end of the lower transparent electrode 2L are within the liquid crystal display cell 1 and therefore cannot be drawn as electrodes outside the liquid crystal cell 1. Accordingly, the coordinate input detection signal current cannot flow through the transparent electrodes 2U, 2L, and the display device with coordinate input function as shown in FIG. 1 cannot be constituted in the prior art. SUMMARY OF THE INVENTION In order to solve the above-mentioned problems in the prior art, an object of the invention is to provide a display device with coordinate input function even in case of a liquid crystal display panel having a display screen divided into two, upper and lower parts to drive separately, by ensuring the coordinate input detection signal current flowing, in two-layer type liquid crystal display panel. In order to attain the foregoing object, according to the invention, there is provided a display device with coordinate input function having a liquid crystal display panel for both displaying images and inputting coordinates through an electromagnetic sensor, comprising a liquid crystal display panel of two-layer type including a compensation cell, as the liquid crystal display panel, characterized by a plurality of transparent electrodes arranged on said compensation cell in an X-Y matrix form and to be activated separately from each other, for providing a coordinate input detection signal. Further advantageous embodiments of the invention are defined in the subclaims. In a display device with coordinate input function according to the invention, a liquid crystal display panel of two-layer type with a liquid crystal cell for phase compensation is used, and coordinate input electrodes are arranged in the liquid crystal cell for phase compensation and the coordinate input detection signal current flows through the coordinate input electrodes thereby inputting of the coordinates is performed. The foregoing and other objects and novel features of the invention will be more fully appear from the following detailed description when the same is read in connection with the accompanying drawings. It is to be expressly understood, however, that the drawings are for purpose of illustration only and is not intended as a definition of the limits of the invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a constitution diagram of a display device with coordinate input function in the prior art; FIG. 2 is a sectional view of a liquid crystal display panel in the prior art; FIG. 3 is a sectional view of a standard liquid crystal display panel of two-layer type in the prior art; FIG. 4 is a constitution diagram of a liquid crystal display panel divided into two, upper and lower parts in the prior art; FIG. 5 is a constitution diagram of a display device with coordinate input function according to an embodiment of the invention; and FIG. 6 is a sectional view of a liquid crystal display panel of two-layer type according to the embodiment of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the invention will now be described referring to the accompanying drawings. FIG. 5 is a constitution diagram of a display device with coordinate input function as an embodiment of the invention. In FIG. 5, reference numeral 1 designates a liquid crystal display cell, numerals 2U, 2L, 3 designate transparent electrodes for image display, which are arranged on glass substrates 12, 13 to constitute the liquid crystal display cell 1, numerals 4U, 4L, 5 designate drive circuits which activate the transparent electrodes 2U, 2L, 3 and drive the liquid crystal display cell 1, numeral 6 designates a control circuit, numeral 7 designates a magnetic field sensor, and numeral 8 designates an amplifier which amplifies output signals of the magnetic field sensor 7. Also numeral 21 designates a liquid crystal cell for phase compensation, numerals 22, 23 designate transparent electrodes for coordinate input, which are arranged on glass substrates 32, 33 to constitute the liquid crystal cell 21 for phase compensation, and numerals 24, 25 designate drive circuits which activate the transparent electrodes 22, 23 and through which the coordinate input detection signal current flows. FIG. 6 is a sectional view of the liquid crystal display panel as the embodiment of the invention. In FIG. 6, reference numeral 1 designates a liquid crystal display cell, numeral 21 designates a liquid crystal cell for phase compensation, numerals 11, 31 designate seal substances which seal a liquid crystal 10 between glass substrates 12, 13 and between glass substrates 32, 33 respectively, and numerals 14, 15 designate polarizing plates. As clearly seen from comparison with FIG. 3 showing a sectional view of the standard liquid crystal display panel of two-layer type in the prior art, in the invention, the glass substrates 32, 33 to constitute the liquid crystal cell 21 for phase compensation of the liquid crystal display panel of two-layer type, are provided with transparent electrodes 22, 23 arranged in an X-Y matrix form, and an AC signal as the coordinate input detection signal is supplied from the control circuit 6 through the drive circuits 24, 25 to the transparent electrodes 22, 23 in sequence. As a result, a rotating magnetic field is generated on the periphery of each of the transparent electrodes 22, 23 by the coordinate input detection signal current. And then, the coordinate input can be detected through similar process to the prior art. Thus even in a liquid crystal display panel having a display screen divided into two, upper and lower parts to drive separately, the coordinate input detection can be performed. The liquid crystal cell for phase compensation 21 is an example of a compensation cell to improve the optical characteristics of the liquid crystal cell for display 1, and may be constituted by a film or the like to exhibit the optical anisotropy. Although the electromagnetic coupling system is used as coordinate input detection system in the embodiment, the invention is not limited to this. According to the invention as above described, the liquid crystal cell for phase compensation of the liquid crystal display panel of two-layer type, is provided with transparent electrodes arranged thereon in an X-Y matrix form as the coordinate input detecting electrodes, thereby the display device with coordinate input function can be constituted without using a special coordinate input panel in addition to the display panel even in the case that the liquid crystal display panel is divided into two part to drive separately.

Claims: A display device with coordinate input function having a liquid crystal display panel for both displaying images and inputting coordinates through an electromagnetic sensor (7), comprising: a liquid crystal display panel of two-layer type including a compensation cell (21), as the liquid crystal display panel; characterized by a plurality of transparent electrodes (22, 23) arranged on said compensation cell (21) in an X-Y matrix form and to be activated separately from each other, for providing a coordinate input detection signal. A display device with coordinate input function as set forth in claim 1, wherein said compensation cell (21) is a liquid crystal cell for phase compensation. A display device with coordinate input function as set forth in claim 1, wherein said compensation cell is a film with optical anisotropy. A display device with coordinate input function as set forth in any one of claims 1 through 3, wherein an image display screen of the liquid crystal display panel of two-layer type is divided into plural areas to drive separately.

Inventors: YOSHIOKA KAZUO C O MITSUBISHI, YOSHIOKA, KAZUO, C/O MITSUBISHI DENKI K.K.
Applicants: MITSUBISHI ELECTRIC CORP, MITSUBISHI DENKI KABUSHIKI KAISHA
Application year: 1990
Main classification: G06F3
IPC codes: G06K11, G06F3, G09G3, H04N5