Electric lamp and discharge devices – With luminescent solid or liquid material – Solid-state type
Reexamination Certificate
2002-03-08
2003-12-30
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Solid-state type
C313S506000, C313S512000, C200S513000
Reexamination Certificate
active
06670750
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an EL sheet employed as a back light in an operating section of various electronic apparatuses, and to a switch employing the EL sheet.
BACKGROUND ART
Electronic apparatuses, as being diversified recently, includes a switch-key to be identified and operable even in a dark place. The switch-key includes a back light disposed at a rear part of an operating section. Many of the back lights employ EL sheets. A switch including the conventional EL sheet discussed above will be described hereinafter with reference to
FIG. 7
, in which dimensions in a thickness direction are enlarged for better understanding.
FIG. 7
shows a lateral sectional view of the switch employing an EL sheet. Light-transmissible insulating film
1
made of, e.g., polyethylene terephtalate has domed diaphragm
2
, which swells upward, formed at a given place. Beneath the entire lower face of film
1
, light-transmissible electrode layer
3
A, made of tin indium oxide, is formed by a spattering or an electron beam method.
Luminous layer
3
B, dielectric layer
3
C, back electrode layer
3
D, and insulating layer
3
E are laid one after another beneath layer
3
A by printing beneath layer
3
A except bent section
2
A around the root of diaphragm
2
, so that EL element layer
3
, as a whole, may be constructed. Luminance layer
3
B includes high dielectric resin, made of fluoro rubber or cyano-system resin in which zinc sulfide, which is a base material for light emission, is dispersed. Dielectric layer
3
C includes high dielectric resin in which barium titante is dispersed. Back electrode layer
3
D is made of silver or carbon resin system. Insulating layer
3
E is made of epoxy resin or polyester resin.
Beneath EL element layer
3
, formed on the lower face of diaphragm
2
, a movable contact
4
is printed, so that EL sheet
5
, as a whole, may be constructed. Movable contact
4
is made of epoxy resin or polyester resin in which conductive particles such as silver or carbon are dispersed.
Circuit board
6
made of an insulating film such as polyethylene terephtalate is disposed under EL sheet
5
, and a pair of fixed contacts
6
A—facing movable contact
4
with a given clearance—are disposed on the upper face of board
6
. Plural wiring patterns (not shown) are coupled to fixed contacts
6
, so that a switch as a whole may be constructed.
Beneath insulating film
1
, having an entire lower face covered with light-transmissible electrode layer
3
A, EL element layer
3
, which includes luminous layer
3
B, dielectric layer
3
C, back electrode layer
3
D and insulating layer
3
E, is printed. Movable contact
4
is also printed on the top of that. Then diaphragm
2
is formed using a mold, so that EL sheet
5
may be completed. EL sheet
5
is bonded to circuit board
6
with adhesive or by thermal bonding so that the switch may be completed.
The switch is mounted to an operating section of an electronic apparatus, and an alternating current (AC) voltage from a circuit of the apparatus is applied between light-transmissible electrode layer
3
A and back electrode layer
3
D of EL sheet
5
, so that luminous layer
3
B may emit light. The light illuminates the operating section of the apparatus from the back of the operating section, and thus a user can identify and operate the operating section easily even in a dark place.
Diaphragm
2
is depressed from above the diaphragm through, e.g., a key-button, then diaphragm
2
is bowed on a fulcrum, i.e., bent section
2
A or its vicinity with a click feel, and thereby, movable contact
4
moves downward to contact with fixed contacts
6
A. Movable contact
4
thus contacts electrically with fixed contacts
6
A. When the depression is released, diaphragm
2
is restored to the status shown in
FIG. 7
by resilient restoring force of the diaphragm.
The conventional EL sheet in the switch includes light-transmissible electrode layer
3
A made of metallic hard film formed beneath the entire face of insulating film
1
. This structure degrades the click feel and the flexibility of diaphragm
2
during operation. Thus, light-transmissible electrode layer
3
A may crack when diaphragm
2
is formed or depressed repeatedly. Further, the depressing force through diaphragm
2
tends to change.
SUMMARY OF THE INVENTION
An EL sheet generates a stable click feel during an operation and is easy to be processed. A switch employs the EL sheet. The EL sheet includes the following elements:
(a) a light-transmissible insulating film having a domed diaphragm swelling upward;
(b) an EL element layer including a light-transmissible electrode layer, a luminous layer, a dielectric layer, and a back electrode layer laminated beneath the insulating film in this order except at a bent section and its vicinity around the root of the diaphragm;
(c) a first conductive pattern coupled to the light-transmissible electrode layer and formed beneath the insulating film; and
(d) a second conductive pattern being coupled to the back electrode layer and formed beneath the insulating film.
The switch includes the EL sheet and contacts being disposed under the diaphragm to resiliently and electrically contact each other.
REFERENCES:
patent: 5871088 (1999-02-01), Tanabe
patent: 5901834 (1999-05-01), Inubushi et al.
patent: 5950808 (1999-09-01), Tanabe et al.
patent: 0 818 793 (1998-01-01), None
patent: 0 847 066 (1998-06-01), None
patent: 11-39983 (1999-02-01), None
Hanahara Tetsuro
Ishikawa Takayuki
Okuma Shinji
Santo Koichi
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