Coordinate input device having high transmittance

Details Coordinate input device having high transmittance Coordinate input device having high transmittance

1999-08-02

2001-10-23

Zimmerman, Mark (Department: 2674)

Telegraphy

Systems

Position coordinate determination for writing

C178S018030, C345S156000, C345S173000, C345S179000

Reexamination Certificate

active

06307166

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coordinate input device in which data are inputted by operating an operating area with an input device such as a pen.
2. Description of the Related Art
FIG. 4A
is a sectional view of the main portion of a conventional coordinate input device, and
FIG. 4B
is a sectional view taken along the line
4
B—
4
B of FIG.
4
A.
As shown in
FIGS. 4A and 4B
, in the conventional coordinate input device, a transparent lower electrode
22
composed of an ITO film (a resistive film formed of indium oxide) is provided over the entire upper surface of a substrate
21
composed of transparent rectangular sheet glass, and a plural spacers
23
composed of a transparent insulating material are provided on the upper surface of the lower electrode
22
, spaced at intervals.
A transparent upper electrode
25
composed of an ITO film is provided over the entire lower surface of a film
24
composed of a transparent plastic such as polyethylene terephthalate. The upper electrode
25
is opposed to the lower electrode
22
and is placed on the spacers
23
. Thus, the lower electrode
22
and the upper electrode
25
are combined, being isolated from each other.
When such a coordinate input device is used, it is, for example, placed on a liquid crystal display device or the like. The information displayed on the liquid crystal display device is visually perceived by the operator through the coordinate input device. In response to this, an input device (not shown in the drawing), such as an input pen, is pressed against the film
24
to cause deformation, and the upper electrode
25
is brought into contact with or separated from the lower electrode
22
, and thus a desired coordinate is inputted.
However, although the conventional coordinate input device is composed of transparent materials, since materials having different refractive indices are deposited, the light passing through the coordinate input device may be attenuated or reflected, and thus the transmittance therethrough cannot be 100%. When the coordinate input device is combined with a liquid crystal display device or the like, the displayed content may be attenuated, resulting in reduced visibility in comparison to the liquid crystal display device alone. Therefore, a method for increasing transmittance through a coordinate input device is desired.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a coordinate input device having high transmittance therethrough.
In accordance with the present invention, a coordinate input device includes an upper electrode composed of a transparent resistive layer formed on the lower surface of a flexible transparent film, a lower electrode composed of a transparent resistive layer formed on the upper surface of a substrate composed of transparent glass, a thin film composed of a transparent insulating material having a lower refractive index than that of the lower electrode, the thin film being provided with a plurality of holes, and spacers composed of an insulating material provided on the thin film. The upper electrode and the lower electrode are opposed to each other with the spacers therebetween so that the upper electrode and the lower electrode both conduct when they are brought into contact with each other through the holes. Thus, the reflectance of transmitted light is decreased and the transmittance is increased while maintaining the input performance in the coordinate input device.
In a coordinate input device of the present invention, the holes are preferably formed at a distance in a grid pattern. Thus, uniform input load is obtained over the entire coordinate input device when coordinates are inputted, and the transmittance is improved.
In a coordinate input device of the present invention, preferably, the lower electrode is composed of indium oxide, and the thin film is composed of a material selected from the group consisting of an acrylic resin, an epoxy resin, a silicone resin, a fluororesin, magnesium fluoride, and silicon dioxide.
In a coordinate input device of the present invention, preferably, the thin film has a thickness of 50 nm to 1,000 nm, the holes have a diameter of 30 &mgr;m to 200 &mgr;m, and the holes are spaced at a distance of 30 &mgr;m to 200 &mgr;m.


REFERENCES:
patent: 4628408 (1986-12-01), Kimura
patent: 4990900 (1991-02-01), Kikuchi
patent: 5555163 (1996-09-01), Pisani

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