Liquid crystal cells – elements and systems – Liquid crystal system – Liquid crystal writing tablet
Reexamination Certificate
2000-09-11
2003-05-06
Dudek, James (Department: 2871)
Liquid crystal cells, elements and systems
Liquid crystal system
Liquid crystal writing tablet
Reexamination Certificate
active
06559902
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a touch panel placed on a screen of display devices such as LCDs (liquid crystal displays), CRTs (cathode ray tubes), or the like with which position input is obtained by being depressed from above by a finger or pen in accordance with instructions on the seen-through screen.
BACKGROUND ART
Conventionally, as shown in
FIG. 4
, a transparent touch panel of a resistance film system is so constructed that a pair of an upper electrode sheet
101
and a lower electrode sheet
102
having transparent electrodes of ITO or the like on transparent films respectively are arranged opposite to each other via spacers
103
of an insulating substance between the electrodes, and a transparent hold plate
105
of a resin totally is bonded to a lower face of the lower electrode sheet
102
via a transparent adhesive layer
104
(referring to FIG.
5
).
For the transparent films of the upper electrode sheet
101
and the lower electrode sheet
102
, a polyethylene terephthalate-film of a thickness of 100-200 &mgr;m superior in flexibility to pressing at the input time is used, which is generally biaxially stretched. For the transparent hold plate
105
, a polycarbonate plate of a thickness of 0.5-3.0 mm with a superior rigidity for protecting a screen of an LCD or the like from pressing at the input time is used, which is generally unstretched.
The polyethylene terephthalate film used for the transparent film of the lower electrode sheet
102
and the polycarbonate plate used for the transparent hold plate
105
are different in thermal expansion coefficient, and moreover the former is stretched whereas the latter is unstretched. The transparent film of the lower electrode sheet
102
is bonded totally, that is, over the entire face to the transparent hold plate
105
. As such, the transparent hold plate
105
changes differently in size between the side of the lower electrode sheet and the opposite side when the touch panel is exposed to a severe temperature environment or humidity environment. The touch panel sometimes warps to project upward at its central part (with reference to FIG.
5
). This warp produces an air layer between the touch panel and the screen under the touch panel, whereby a sense of touch in operation is dulled because of an unnecessary deflection applied to the whole of the touch panel at the input time.
The warp could be forcibly corrected to make the touch panel flat in setting the touch panel on the screen of the LCD, CRT, or the like. This, however, leads to waving the transparent film of the upper electrode sheet
101
and worsening an appearance or look of the touch panel and a visibility of the screen. The waving of the transparent film of the upper electrode sheet
101
changes a gap between electrodes irregularly, consequently varying the sense of touch depending on spots of the touch panel. An insulation failure may also be brought about through mutual touch of the electrodes if the waving of a large size takes place.
An object of the present invention is therefore to provide a touch panel superior in flexibility for a pressing operation at the input time and rigidity for protecting a screen of a display device such as an LCD, CRT, or the like from the pressing operation, which hardly warps even exposed to a severe temperature environment or humidity environment, with solving the above-described issues.
DISCLOSURE OF INVENTION
In order to accomplish the above object, the present invention is so constructed as follows.
According to a first aspect of the present invention, there is provided a touch panel in which an upper electrode sheet having an upper transparent electrode formed on a transparent film of polyethylene terephthalate and a lower electrode sheet having a lower transparent electrode formed on a transparent film of polycarbonate are arranged opposite to each other via a plurality of spacers of an insulating substance between the upper and lower electrodes, while a transparent hold plate of a polycarbonate plate is bonded over an entire face to a lower face of the lower electrode sheet via a transparent adhesion layer.
According to a second aspect of the present invention, there is provided the touch panel according to the first aspect which uses a polycarbonate film of a thickness of 50-300 &mgr;m for the transparent film of the lower electrode sheet.
According to a third aspect of the present invention, there is provided the touch panel according to the first or second aspect the transparent hold plate of which is a polycarbonate plate of a thickness of 0.5-3.0 mm having a rigidity for protecting a screen of a display apparatus from pressing at the input time.
According to a fourth aspect of the present invention, there is provided the touch panel according to any one of the first through third aspects in which the transparent adhesion layer is a transparent acrylic adhesive approximate in refractive index to the transparent film of the lower electrode sheet and the transparent hold plate.
According to a fifth aspect of the present invention, there is provided the touch panel in any one of the first through fourth aspects which uses a polycarbonate film of a thickness of 50-300 &mgr;m for the film of the lower electrode sheet, with the transparent adhesion layer being adapted to keep an elastic modulus of 5×10
5
-5×10
7
dynes/cm
2
at ordinary temperatures.
According to a sixth aspect of the present invention, there is provided the touch panel according to any one of the first through fifth aspects which is arranged on a screen of a display apparatus to enable position input when pressed from above by a finger or pen in accordance with instructions on the seen-through screen.
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patent: 4527862 (1985-07-01), Arakawa
patent: 5541370 (1996-07-01), Matsuda et al.
patent: 5844175 (1998-12-01), Nakanishi et al.
patent: 6016134 (2000-01-01), Ota
patent: 6118889 (2000-09-01), Izuno et al.
patent: 6310614 (2001-10-01), Maeda et al.
patent: 6329044 (2001-12-01), Inoue et al.
patent: 5-338086 (1993-12-01), None
patent: 6-275132 (1994-09-01), None
patent: 6-309101 (1994-11-01), None
patent: 6-309990 (1994-11-01), None
patent: 11-297160 (1999-10-01), None
Hashimoto Takao
Kusuda Yasuji
Shimizu Jun
Yamada Shin-ya
Dudek James
Nissha Printing Co. Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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