Keypad assembly for electronic device

A keypad assembly includes a pressing surface layer, a pattern layer, an elastic layer, a light guiding layer, and a pressing bottom layer. The pattern layer is under the pressing surface layer. The elastic layer is located between and interlocks the pattern layer and the light guiding layer by adhesive. The pressing bottom layer adheres to the light guiding layer. The keypad assembly has an ideal appearance by lights collection of the light guiding layer. User can feel comfortable when pressing the keypad assembly because of the elastic layer's buffering effect.

BACKGROUND

1. Field of the Invention

The present invention generally relates to keypad assemblies, specifically to a keypad assembly for an electronic device, such as a mobile phone.

2. Description of Related Art

A typical keypad assembly for a given electronic device includes an upper shell and a keypad. The upper shell defines a plurality of holes therethrough. The keypad has a plurality of keys formed on a top surface thereof and a plurality of switch points on a bottom surface thereof. Each switch point corresponds to a key of the keypad. The keypad is mounted under the upper shell and each key is exposed through a corresponding hole of the upper shell. However, the keys of the keypad are typically made of stiff material and the switch points are made of metal. When a user presses the key, a finger of the user may feel uncomfortable due to the hardness of the keys and switch points.

Currently, a thin keypad assembly for an electronic device may include a pressing surface layer and a pressing bottom layer. The pressing surface layer is made of transparent elastic rubber and the pressing bottom layer is made of hard polycarbonate. The pressing surface layer and the pressing bottom layer are made integral by adhesive or hot press molding. Patterns on the keypad assembly are formed on the pressing bottom layer by printing before adhesive or hot press molding. However, the thickness of the keypad assembly may be so thin that the user may feel uncomfortable when pressing the keypad assembly. Also, because collecting the light rays under the pressing bottom layer can be difficult in the area of the patterns, it is difficult to achieve ideal vision effect. Also, if the thin keypad assembly cannot eliminate static electricity, the static electricity may generate undesirable influence for the electronic device.

Therefore, there is room for improvement within the art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present keypad assembly is suitable for electronic devices, such as mobile phones, personal digital assistants (PDAs), and etc.

Referring toFIGS. 1 and 2, a keypad assembly100includes a pressing surface layer10, a pattern layer20, a first adhesive layer30, an elastic layer40, a second adhesive layer50, a light guiding layer60, a third adhesive layer70and a pressing bottom layer80.

The pressing surface layer10can be made of transparent and elastic thermoplastic macromolecule materials such as rubber, thermoplastic polyurethane or a combination thereof. A thickness of the pressing surface layer10is in the range of about 0.1-about 0.2 mm (millimeter) and is preferably about 0.2 mm. The pressing surface layer10has a top surface12and an opposite bottom surface14. The top surface12has a plurality of key profiles122formed thereon. The profiles122may protrude from the top surface12or may be recessed in top surface12. In the exemplary embodiment, the profiles122protrude from the top surface12. Each profile122can be substantially ring-shaped. A thickness of the profile122is in the range of about 0.2-about 0.3 mm and is preferably about 0.2 mm. The profiles122can be formed by hot press molding. The location of the profiles122on the pressing surface layer10identify the locations of keys formed on the keypad assembly100.

The pattern layer20includes a hard layer22, and a printing ink layer24formed on one surface of the hard layer22. The hard layer22is a transparent and can be made of thermoplastic macromolecule material such as polycarbonate, polyethylene terephthalate or a combination thereof. The printing ink layer24has a plurality of icons26formed thereon. In this exemplary embodiment, the printing ink layer24has a background color printed or applied thereon and the icons26are printed on or applied thereto in a contrasting color. Each icon26corresponds to a profile122. The hard layer22contacts the bottom surface14of the pressing surface layer10after the pattern layer20is assembled to the pressing surface layer10. A thickness of the pattern layer20is in the range of about 0.1-about 0.2 mm and is preferably about 0.125 mm.

The first adhesive layer30is transparent double-face adhesive layer and substantially rectangular. The first adhesive layer30has a thickness in the range of about 0.1-about 0.2 mm and is preferably about 0.1 mm. The shape of the first adhesive30is similar with the shape of the pattern layer20, and the size of the first adhesive layer30is smaller than the size the pattern layer20. The first adhesive layer30adheres the pattern layer20to the elastic layer40.

The elastic layer40can be made of transparent and elastic thermoplastic macromolecule materials such as rubber, thermoplastic polyurethane or a combination thereof. The surface size of the elastic layer40is same as the surface size of the first adhesive layer30. A thickness of the elastic layer40is in the range of about 0.1-about 0.2 mm and is preferably about 0.2 mm. A bottom surface of the elastic layer40has a plurality of columns42formed thereon. The thickness of a column42is in the range of about 0.2-about 0.3 mm and is preferably about 0.25 mm. Each column42can be formed by hot press molding the elastic layer40. Each column42corresponds to an icon26after the elastic layer40is affixed to the pattern layer20by the first adhesive layer30.

The second adhesive layer50is a transparent double-face adhesive layer and is a substantially hollow rectangular frame. The shape of the second adhesive layer50corresponds to a peripheral edge of the pattern layer20. The thickness of the second adhesive layer50is in the range of about 0.1-about 0.2 mm and is preferably about 0.1 mm. The second adhesive layer50interconnects the pattern layer20and a housing (not shown) of an electronic device together.

The light guiding layer60is made of transparent and plastic macromolecule material such as polyimide. A surface size of the light guiding layer60is the same as the surface size of the elastic layer40. A thickness of the light guiding layer60is in the range of about 0.1-about 0.2 mm and is preferably about 0.125 mm. The light guiding layer60is associated with a light source (not shown) contained within the electronic device and has a plurality of focusing areas62formed thereon. Each focusing area62corresponds to an icon26of the pattern layer20and is formed by printing. In this exemplary embodiment, the focusing areas62are in circular shapes and printed on the light guiding layer60by white printing ink. Light rays from the light source (neither shown) inside of electronic device will be collected in the focusing areas62and directed towards the icons26, thereby increasing the brightness of the icon26.

The third adhesive layer70is a transparent double-faced adhesive layer. The third adhesive layer70includes glue pieces72. A thickness of the glue piece72is in the range of about 0.1-about 0.2 mm and is preferably about 0.1 mm. The third adhesive layer70interconnects the pressing bottom layer80and the light guiding layer60together.

The pressing bottom layer80can be made of a transparent and thermoplastic macromolecule material such as polycarbonate, polyethylene terephthalate or a combination thereof. The pressing bottom layer80has a plurality of protrusions82formed on a first surface thereof and a plurality of concaves84formed on opposite second surface thereof corresponding to the protrusions82. The protrusions82and the concaves84can be formed by hot press molding. The first surface of the pressing bottom layer80has a metal mesh83printed thereon. A wire86formed at a side of the pressing bottom layer80is electronically connected at one end to the metal mesh83and the other end is connected to the grounded circuit (not shown) of the electronic device. The wire86can remove the static electricity formed in the keypad assembly100. The second surface of the pressing bottom layer80has a plurality metal domes88mounted in the concaves84. The metal domes88protrude from the concave84. The metal domes88are used for resisting the switches (not shown) formed on a circuit board of the electronic device.

In assembly, the pressing surface layer10and the pattern layer20are connected and stacked together by hot pressing molding, each profile122of the pressing surface layer10corresponds to an icon26. The pattern layer20is adhered to the elastic layer40by the first adhesive layer30, with the peripheral edge of the pattern layer20exposed from the elastic layer40and each icon26corresponding to a column42. The second adhesive layer50is adhered to the peripheral edge of the pattern layer20and the housing of electronic device. The guiding layer60is adhered to the first surface of the pressing bottom layer80by the glue pieces72, each focusing area62corresponds to a protrusion82. The guiding layer60together with the pressing bottom layer80are clamped between the elastic layer40and the circuit board of the electronic device. Each column42corresponds to a focusing area62, the metal domes88of the pressing bottom layer80contacts the switches of the circuit board.

When using the keypad assembly100, a desired profile122is pressed to further press the columns42of the elastic layer40such that the columns42resist the protrusions82. Because the column42is elastic, the column42has a buffering effect when pressed. Accordingly, the user will not feel the obvious resisting force, so the user can feel more comfortable when pressing. The light guiding layer60has a plurality of focusing areas62, the focusing areas62can collect light rays under the pressing bottom layer80to make the appearance of the icons26brighter. The wire86connects the metal mesh83and the grounded circuit of the electronic device to effectively eliminate static electricity.

It should be understood that the icons26may be formed on the bottom surface14of the pressing surface layer10.