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Mobile Phone Patent Abstract
A keypad for a mobile phone includes a circuit board having a fixed
contact point; a dome switch disposed on the circuit board; a base
pad member having a projection for pressing the dome switch to generate
signal; an upper pad member having a key top, the upper pad member
being integrally formed with the base pad member, and an EL element
disposed surface-contacting between the base pad member and the
upper pad member.
Mobile Phone Patent Claims
What is claimed is:
1. A keypad for a mobile phone, comprising: a circuit board having
a fixed contact point; a dome switch disposed on the circuit board;
a base pad member having a projection for pressing the dome switch
to generate a signal; an upper pad member having a key top, the
upper pad member being integrally formed with the base pad member;
and an EL element disposed between the base pad member and the upper
pad member, the EL element being above the projection of the base
pad member and a surface contacting both the base pad member and
the upper pad member.
2. A keypad of claim 1, further comprising a diffusing layer, wherein
the diffusing layer is separately formed on the EL element.
3. A keypad of claim 2 wherein the El element emits a backlight
to the upper pad member, the back light allowing the upper pad member
to be seen in a dark place.
4. A keypad of claim 1, further comprising a printed film, wherein
the printed film is located on the EL element and covered by the
upper pad member.
5. A keypad of claim 1 wherein the EL element is integrally formed
with the base pad member, and the key top is attached on the EL
element.
6. A keypad of claim 1 wherein the base pad member and the key
top are formed of a material selected from at least one of silicon
rubber and synthetic resin.
7. A keypad of claim 1, wherein the EL element is integrated with
the base pad member in a first mold and wherein the EL element is
placed in the first mold before a first material forming the base
pad member is placed in the first mold.
8. A keypad of claim 1 wherein the EL element is a sheet-type luminous
element for minimizing a space occupied.
9. A keypad of claim 1 wherein the base pad member has an upper
surface and the upper pad member had a bottom surface and wherein
the EL element is in tight surface-contact with both the upper surface
of the base pad member and the bottom surface of the upper pad member.
Mobile Phone Patent Description
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of Korean Patent Application No.
2001-27898, filed on May 22, 2001.
BACKGROUND OF THE INVENTION
(a) Field of the Invention
The present invention relates to a keypad for a mobile phone and,
more particularly, to a keypad that has a sheet-type luminous element
(an EL element) formed in a thin sheet and integrated therein, thereby
minimizing noise and vibration generated by the EL element.
(b) Description of the Related Art
Generally, a keypad for a mobile phone is an input device consisting
of a separate grid of numerical and function keys arranged for efficient
data entry. The keys are fitted into holes formed on a front housing
of the mobile phones and jutted out so that users can conveniently
input the data.
Light source formed of a luminous element is installed on the bottoms
of the key so that the user can identify the numerical numbers and
letters printed on the keys in a dark place. When the light source
is turned on, the light is emitted to the letters and numerical
numbers printed on the keys by the backlight effect, thereby making
the users identify them.
FIG. 7 shows one of keys constituting a conventional keypad for
a mobile phone.
A key 50 generally comprises a base 52, a key top 54 elevated from
the base 52, and a projection 56 formed on a bottom center of the
key top 54.
The base 52 and the key top 54 are integrally formed by a connecting
portion 58. The connecting portion 58 is designed to be thinner
than the base 52 for the effective operation of the key 50. A printing
layer 60 of letters and numerical numbers is formed on a top surface
of the key top 54 through a silkscreen printing or a laser marking.
The base 52 is provided at its bottom surface with a groove 62
in which a light source formed of an LED lamp is installed.
A dome switch 68 is located under the projection 56, and a fixed
contact point 70 formed on a printed circuit board 64 is located
under the dome switch 68.
When using the mobile phone, the light source 66 is applied with
electric power to provide backlight to the keypad, making it possible
to see the printing layer 60 with the letters and numerical numbers
formed on the key top 54 even in the dark place.
When pushing the key 50, the projection 56 formed on the bottom
of the key 50 overcomes the elastic formed of the dome switch 68
and pushes the dome switch 68 so that the dome switch 68 contacts
the fixed contact point 70, thereby generating a signal.
When releasing the pushing force applied to the key 50, the key
50 is returned to its initial position by the self-elastic force
of the connecting portion 58 and the dome switch.
However, in the conventional keypad, since a groove is formed on
the bottom surface of the base 52 and the light source formed of
the LED lamp is installed in the groove, the thickness of the keypad
is increased as many as the thickness of the light source.
Furthermore, since the key 50, the dome switch 68, and the printed
circuit board 64 are disposed in the front housing of the mobile
phone, and a part of the key 50 is exposed out of the front housing,
it is time consuming to assemble all of the members, thereby deteriorating
the productivity.
To solve the above-described problem, a keypad for a communication
device, which is provided with a sheet-type luminous element (an
EL element) that is designed such that a spacer having opposite
adhesive surfaces is attached on a circuit board and a backlight
is provided on the spacer, has been proposed. However, a special
assembling process for attaching the spacer is required, and the
thickness of the keypad is increased as many as the thickness of
the spacer.
Furthermore, a dome switch, a moving contact point, and a fixed
contact point that are constituting the luminous element are not
sealed, this causes the mobile phone's life to be reduce and also
causes a shielding process for preventing the noise and vibration
caused by current applied to the luminous element to be required.
SUMMARY OF THE INVENTION
The present invention has been made in an effort to solve the above-described
problems of the conventional art.
It is an objective of the present invention to provide a keypad
that is designed to be produced with less expense and to minimize
the thickness thereof by integrating a thin film EL element thereinto.
It is another objective of the present invention to provide a keypad
that can enhance the reliability and increase its life by preventing
the noise and vibration generated by an EL element.
To achieve the above objectives, the present invention provides
a keypad for a mobile phone, comprising a circuit board having a
fixed contact point; a dome switch disposed on the circuit board;
a base pad member having a projection for pressing the dome switch
to generate signal; an upper pad member having a key top, the upper
pad member being integrally formed with the base pad member; and
an EL element disposed surface-contacting between the base pad member
and the upper pad member.
According to a preferred embodiment of the present invention, a
diffusing layer is formed on the EL element and a printed film is
located on the EL element.
According to another preferred embodiment, the EL element is integrally
formed with the base pad member, and the key top is attached on
the EL element.
Preferably, the base pad member and the key top are formed of a
material selected from at least one of silicon rubber and synthetic
resin.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view of a keypad for a mobile phone according
to a first embodiment of the present invention;
FIG. 2 is a sectional view for illustrating a diffusing layer printed
on a keypad of FIG. 1;
FIG. 3 is a sectional view for illustrating a printing film installed
in a keypad of FIG. 1;
FIG. 4 is a sectional view of a keypad for a mobile phone according
to a second embodiment of the present invention;
FIG. 5 is a sectional view for illustrating a light guide layer
printed on a keypad of FIG. 4;
FIG. 6 is a sectional view of a keypad for a mobile phone according
to a third embodiment of the present invention; and
FIG. 7 is a sectional view of a conventional keypad for a mobile
phone.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Preferred embodiments of the present invention will be described
more in detail hereinafter in conjunction with the accompanying
drawings.
FIGS. 1 and 2 show a keypad according to a first embodiment of
the present invention. A keypad of this embodiment may be formed
of silicon rubber.
A keypad of this embodiment comprises an upper pad member 2 having
plural key tops 8 pressed or touched by a user and a base pad member
6 disposed opposing the upper pad member 2, and an EL element 14
integrally disposed between the upper and base pad members 2 and
6.
The key tops 8 of the upper pad member 2 are arranged to maintain
their space at a predetermined distance and elevated upward passing
over a front cover and spaced away from each other at a predetermined
distance. The base pad member 6 is provided with plural projections
4 corresponding to the key tops 8.
The projections 4 are located such that they can press corresponding
dome switch S provided on a circuit board P by the user pressing
the key tops 8.
The base pad member 6 is further provided with groove portions
10 for providing the elastic force and the restitutive force to
the key top 8.
A printed layer 12 with numerical numbers or letters is formed
on the key tops 8. The printed layer 12 is formed by a spray printing
method, a laser marking method, or a silk screen-printing method.
A thin film EL element 14 for the backlighting is disposed between
the upper and base pad members 2 and 6.
When electric field is applied to the EL element 14, the electrons
and electron holes are coupled to emit light from the surface. Since
the EL element 14 is capable of being driven even by low voltage
as well as providing the wide view angle, it can be widely applied.
Furthermore, since the EL element 14 is formed of a thin sheet,
the occupying space in the mobile phone can be minimized when compared
with the conventionally used LED lamp, thereby making it possible
to make the phone compact.
Describing the method for inserting the EL element 14 to integrate
with the keypad, the base pad member 6 is first formed using a low
mold (not shown), and then the EL element 14 that is shorter than
the pad member 6 is disposed on the pad member 6. Next, silicon
rubber liquid is poured on the EL element 14 and pressed by a mold
in the shape of the base pad member 6, thereby forming the base
pad member 6.
Next the silicon rubber liquid is pressed by a mold in the shape
of the key top, thereby forming the key top and attaching the base
pad member 6 to the upper pad member 2. As a result, the EL element
14 makes tight surface contacts between the base pad member 6 and
the upper pad member 2.
The EL element is an alternating current planar light source driven
by a predetermined driving voltage and frequency, inevitably generating
the noise and vibration. However, in the present invention, the
EL element 14 is disposed between and tightly contacting the base
pad member 6 and the upper pad member 2, thereby alleviating the
noise and the vibration.
In addition, as shown in FIG. 2, a diffusing layer 16 may be formed
on the EL element to allow the light emitted from the EL element
14 to be diffused, thereby enhancing the backlighting effect.
In the first embodiment, the printing layer 12 is printed on the
key tops 8. However, as shown in FIG. 3, a printing film 18 with
letters and numerical numbers may be integrated on the EL element
14.
By integrating the printing film 18 on the EL element 14, the letters
and numerical numbers can be more clearly shown.
FIGS. 4 and 5 show a second embodiment of the present invention.
The keypad of the second embodiment is identical to that of the
first embodiment except that the key tops are formed of a different
material from that of the pad members.
That is, the key pad of this second embodiment comprises a base
pad member 6a formed of silicon rubber, an upper pad member 6b integrally
formed with the base pad member 6a, and key tops 20 formed of synthetic
resin, the key tops 20 being attached on the upper pad member 6b
by adhesive 22.
In this embodiment, the EL element 14 is also surface-contacted
with the pad members.
FIG. 6 shows a keypad according to a third embodiment of the present
invention.
In third embodiment, the EL element 14 having a length identical
to that of a base pad member 6 formed of silicon rubber is integrally
surface-contacted with the EL element 14. A key tops 20 formed of
synthetic resin is attached on the EL element by adhesive 22.
As described above, as the thin EL element is integrally inserted
into the keypad, the thickness of the keypad can be minimized while
simplifying the assembling and manufacturing process, thereby improving
the productivity.
In addition, since the EL element is tightly disposed contacting
between the base and upper pad members, the noise and vibration
caused by the EL element can be suppressed, thereby improving the
reliability and endurance of the element. |