Technical Field

[1] The preset invention relates to a film type switch, and in particular to a film type switch in which three sheets of thin films are stacked, and a switch circuit and a contract point are printed at an inner side of upper and lower films. With the above constructions, the present invention is well adapted to a cellular phone and various electronic products. Background Art

[2] Figure 1 is a view illustrating a construction of a conventional cellular phone keypad. The keypad of Figure 1 comprises plastic material keys 1 formed at the upper most side, a silicon rubber plate 2 on which a plurality of keys are arranged and attached, a metal dome 3 formed below the rubber plate 2, a sheet 4 to which a plurality of metal domes are attached, and a PCB or film type FPCB 5 with a key matrix switch circuit below the same.

[3] In the above conventional art, when a key 1 is pressed, the metal dome 3 moves down as shown in Figure 2 and contacts with a copper thin switch circuit pattern of an upper surface of the PCB or film type FPCB 5, so that a switching signal is transmitted to an I/O port (I/O ports of micro controller) of MSM.

[4] The conventional keypad is fabricated with a silicon rubber. The silicon rubber is expensive and is soft, not hard, so that a user cannot directly feel a contacting state of the key. In particular, since the material is soft and heavy, it is impossible to obtain a certain movement of keys.

[5] So as to overcome the above problems, the Korean utility model laid-open No.

20-0168397 (laid-open date: November 10, 1999) of film insertion type key pad is developed. According to the above invention, the injection materials of keys are substantially light and hard, so that the user can correctly feel the contacts between the k eys and contact points. There is provided a keypad with a film capable of arranging and fixing each key so as to support the keys and prevent any movement of the same.

[6] Figure 3 is a view of the above conventional art. Here, the key 2 includes a plurality of key tops 4 which are protruded upwards and correspond to a plurality of holes formed at a front housing of a telephone, and a pair of protrusions 6 which are integrally formed with the key tops at the center portion of the low surface. The protrusions 6 are opposite from each other and each have an inclination surface 8 of which an outer surface is connected with a lower surface of the key top 4. A film 10 defines a lower surface of the key top 4 and supports the key top in a horizontal

direction extended from the lower surface of the same for thereby stably supporting the position of the key top 4.

[7] An inclination surface 11 is formed at one side of the film 10 and has a certain angle corresponding to the inclination surface 8 formed at the key top 4. The inclination surface 11 closely contacts with the inclination surface 8 formed at the protrusion for thereby stably fixing the position of each key. The film 10 positioned at the lower surface of the key top 4 supports the key top 4. The film 10 provided at the lower surface of the key top 4 supports the key top 4. The film 10 is made of a transparent material. An ink 12 is coated on the film 10. A certain character 13 is printed using a laser beam. As shown in Figure 3, in the keypad 2, an elastic member 14 contacting with the protrusion 6 is supported by the PCB substrate 16 below a portion in which the protrusion 16 formed at the lower surface of the key top 4 is positioned. The elastic member 14 is formed in a dome shape and receives a pressure of the protrusion 6 and allows a contact with the contact point. Here, the elastic member is preferably made of a certain metal material having an elastic force and a recovery force. The PCB substrate 16 has a contact point 18 contacting with the elastic member 14. The LED lamps 20 are opposite to each other, with light being emitted when the elastic member 14 contacts with the contact point 18. A reflection member 22 is disposed at a portion near the LED lamp 20 for reflecting light of the LED lamp 20.

[8] The injection material of the key is made of a synthetic resin which feels soft and hard, so that user can directly feel a contact with the contact point for thereby generating an accurate signal. The inclination surface of the film attached to the lower surface of the key top contacts with the inclination surface of the protrusion, so that the movement of the key is prevented.

[9] However, in the above conventional keypad, it is impossible to obtain a two-step switching operation with different forces. Namely, the conventional keypad performs a simple function that the electric signals or currents are connected or disconnected by simply pressing the keys. In addition, since it is used together with an expensive FPCB, the fabrication cost increases.

[10]

Disclosure of Invention Technical Problem

[11] Accordingly, it is an object of the present invention to overcome the problems encountered in the conventional art.

[12] It is another object of the present invention to provide a film type switch in which a first key switch is turned on at the same position with a substantially slight press force

(about 2Og ~ 8Og) which corresponds a force needed when a certain finger is softly placed on the same key, and a second switch is turned on when a strong force (over about 150g) is applied as strong as a metal dome is transformed. When not pressed, it recovers based on a tensional force and elastic force of the film. With the above construction, the keys can be very conveniently used when a game is played or a multimedia-related edit and operation are performed, and a cursor is moved.

[13]

Technical Solution

[14] To achieve the above objects, in a keypad switch which includes plastic material keys provided on the upper most side, a silicon rubber plate for arranging a plurality of keys thereon, a metal dome disposed below the same, a sheet to which a plurality of metal domes are attached, and a PCB (Printed Circuit Board) in which a key matrix switch circuit is printed, there is provided a film type switch characterized in that the three thin films are stacked in a sequence of an upper film, a space film, and a lower film, and a switch circuit and contact points are printed on the inner surfaces of the upper film and the lower film, and center contact points are formed between the upper film and the lower film and are positioned at the center of the metal dome, and the contact points are formed at the edges of the metal dome, with the edges being attached to the upper film, and the space film is arranged between the upper film and the lower film, and with the above construction, when the space film is pressed with a slight force, the contact points are contacted, and when the space film is pressed with a strong force, the center contact points and the contact points are concurrently contacted, so that the current is turned on, and when the pressed space film is released, it is recovered with a tensional force and elastic force of the film, so that the contact points between the upper and lower films are disconnected, and the current is turned off.

[15] When the space film is pressed, the center contact points and the contact points are not concurrently contacted. A contact point structure for forming the center contact points and the contact points between the upper film and the lower film is provided with the same structure at multiple portions of one keypad.

[16] In addition, the upper film, space film and lower film are made of plastic materials including a heat resistance reinforced PET, polyester, a PVC, a polyurethane, and an epoxy. The thickness of the upper film, the space film and the lower film are 0.1 through 0.01mm.

[17] The space film is a double side adhesive tape. Here, the space films has the functions that the upper and lower intervals can be maintained, and the upper and lower films are stable fixed by balancing the same, and foreign substances or moistures

are prevented from being inputted into both ends of the film since the upper and lower films are sealingly attached with an adhering force of the double side adhesive tape. [18] The common check key is connected with keys Kl through K7 of the key matrix circuit keypad, and the key sense P port is connected with the common check key in parallel for thereby defining a circuit, and when a certain key is first pressed with a slight force, the contact points contact, and the key sense switch is turned on, and the keypad is connected, so that the signals are transferred, and when the key is second pressed with a strong force, the center contact points are additionally contacted, and so that the switch of the common check key is turned on, and the key sense P port, the keypad port and the key sense port are all connected, so that the generated signals are recognized by a MSM or a key recognition (KEY SENSING) system of a micro controller.

Advantageous Effects

[19] In the present invention, the use is convenient with a softer touch of keypad like using a mouse as compared to a cellular phone which adapts a conventional keypad. In addition, an expensive FPCB or PCB is not used as a material of film or is partially used, so that a fabrication cost decreases.

[20] It is possible to recognize through a LCD on whether a key corresponds to a certain function or a certain character or a number when a user softly places his fingers on the keys when using a keypad. A sub-menu can be conveniently recognized when using a menu.

[21] In particular, when the present invention is adapted to a key matrix circuit of a cellular phone, a menu search function or a data search function can be activated with a slight cursor movement using a slight pressing force before a metal tome is clicked by pressing a corresponding key in a user environment mode. In addition, a user can input characters or numbers with a previous check through the LCD.

[22]

Brief Description of the Drawings

[23] Figure 1 is a view illustrating a construction of a conventional cellular phone keypad.

[24] Figure 2 is a cross sectional view when a keypad of Figure 1 operates.

[25] Figure 3 is a cross sectional view illustrating a conventional film insertion type keypad.

[26] Figure 4 is a cross sectional view illustrating a film type switch according to the present invention.

[27] Figure 5 is a disassembled perspective view illustrating a film type switch according to the present invention.

[28] Figure 6 is a cross sectional view of Figure 4 when a key is pressed with a slight force.

[29] Figure 7 is a cross sectional view of Figure 4 when a key is pressed with a strong force.

[30] Figure 8 is a circuit diagram of a key matrix of a conventional cellular phone keypad.

[31] Figure 9 is a circuit diagram of a key matrix when the present invention is adapted to a cellular phone keypad.

[32]

Best Mode for Carrying Out the Invention

[33] The preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[34] Figure 4 is a cross sectional view illustrating a film type switch according to the present invention. Figure 5 is a disassembled perspective view illustrating a film type switch according to the present invention. Figure 6 is a cross sectional view of Figure 4 when a key is pressed with a slight force. Figure 7 is a cross sectional view of Figure 4 when a key is pressed with a strong force. Figure 8 is a circuit diagram of a key matrix of a conventional cellular phone keypad. Figure 9 is a circuit diagram of a key matrix when the present invention is adapted to a cellular phone keypad.

[35] In the description of the present invention, the term "film type

[36] switch" represents a switch in which at least two sheets of thin films are stacked at certain intervals, and a switch circuit and contact point are printed on one surface of the upper and lower films, so that a current is turned on/off using a tensional force and elastic force of a film.

[37] As shown in Figure 4, three thin films 21, 32 and 33 are sequentially stacked, and a space film 33 is disposed between the two thin films 31 and 32. Namely, the films are stacked in a sequence of an upper film 31, a space film 33 and a lower film 32. A plurality of metal domes 34 are attached on an upper side of the upper film 31 by the number needed. The metal domes 34 and the upper film 31 are engaged by covering the upper sides of the metal domes 34 using an adhesive film 45.

[38] A switch circuit and contact points 37, 38, 39, 40, 41 and 42 based on a key matrix are printed on the inner surfaces of the upper film 31 and the lower film 32. Here, the printing materials are formed of a certain electrically conductive ink including a carbon component, a silver component or other components. Figure 5 is a perspective view illustrating the construction of Figure 4. The arrangement is performed in a sequence of the upper film 31, the space film 33 and the lower film 32. A switch circuit and contact points 37, 38 and 39, 40 and 41, 42 are printed on the inner surfaces of the upper film

31 and the lower film 32. The contact points are three. The center contact points 39 and 40 and contact points 37, 38, 41 and 42 are arranged at certain intervals. With this construction, when a user softly presses the metal dome 34 with a force of about 2Og through 80g, the force is applied to the edges 36 and 36' of the metal dome 34. The contact points 37, 38, 41 and 42 are attached as shown in Figure 6, and the current is supplied. When a user strongly presses the metal dome 34 with a force of about 150g, the center contact points 39 and 40 are attached, so that the current concurrently flows at three points as shown in Figure 7.

[39] When a finger keeps away from the metal dome 34 (namely, force is not applied), the metal dome 34 is recovered as shown in Figure 4 based on a tensional force and elastic force of the upper or upper and lower films, and then the upper film 31 is recovered.

[40] The space film 33 is disposed between the upper film 31 and the lower film 32 and performs an on/off switching operation.

[41] The space film 33 may be formed of a double side adhesive tape. As shown in

Figure 4, the film of the contact point 37 and the contact point 39 are designed not to concurrently contact with the lower contact points when they are pressed.

[42] In addition, there may be further provided a lead part 6 of Figure 1 so that a key matrix contact point signal is transferred to a main circuit or a main PCB in the film type switch according to the present invention. If necessary, the FPCB may be partially connected with the same layer as the film type switch sheet.

[43] The preferred embodiments of the present invention will be described with reference to Figures 6 and 7.

[44] When a finger very slightly presses a certain key with a force of about 20~30g, the metal dome 34 is pressed. As shown in Figure 6, the edges 36 and 36' of the metal dome 34 press the contact point 37 of the upper film 31. The contact point 37 printed with an conductive ink on the inner surface of the pressed upper film 31 contacts with the contact point 38 printed with a conductive ink on the inner surface of the lower film 32, so that the current or electrical signal is first transferred to a key sense I/O port (or I/O port of micro controller) of a cellular phone (or electronic product).

[45] In addition, as shown in Figure 7, when a finger strongly presses at the same position of Figure 7 with a force of above 150g as strong as the metal dome is transformed, the metal dome 34 is transformed, and the upper film 31 presses the lower film 32, and the center contact points 39 and 40 of the metal dome are contacted with each other.

[46] When the center contact points 39 and 40 are pressed, the contact point 39 printed with a conductive ink at an inner surface of the pressed upper film 31 contacts with the contact point 40 printed with a conductive ink at the inner upper surface of the lower

film 32, so that the current or electric signal is second transmitted to the key sense I/O port (or I/O port of micro controller) of the MSM of the cellular phone (or electronic product).

[47] When a corresponding key is strongly pressed with a finger, the center contact points 39 and 40 contact with the contact points 37, 38, 41 and 42, so that the electric signal is transmitted to the VO port of the keypad such as a cellular phone or a computer. When the finger gets distanced from the key, they are recovered to their original states with a tensional force and elastic force of the film, so that the electric signal is disconnected. Namely, the center contact points 39 and 40 are first contacted based on the magnitude of the pressure applied to the metal dome 34. The center contact points 39 and 40 and the contact points 37, 38, 41 and 42 are second contacted concurrently. If the pressure is not applied to the metal dome 34, the film returns to its original state, and the contact points are disconnected for thereby performing an on/off switching operation.

[48] Figure 8 is a view illustrating a conventional key matrix circuit of an ordinary cellular phone. As shown in Figure 6, when the metal dome 34 is slightly pressed, the contact points 37, 38, 41 and 42 of Figure 6 are contacted. In this case, as shown in Figure 8, if it is assumed that a key Fl is pressed, the Fl switch is turned on, and the port of the keypad Kl connected with the above key Fl is connected with the port A of the key sense, so that the signal is transferred. Namely, when the key Fl is pressed, KlA is connected, when the key F7 is pressed, KlB is connected, and when the key F21 is pressed, K7C is connected. In this manner, the keypad ports and key sense ports are connected. With the above operational principles, 21 key signals are generated and transferred.

[49] Figure 9 is a view illustrating a key matrix circuit adapted to a film type switch according to the present invention. When the user strongly presses the metal dome as shown in Figure 7, the center contact points 39 and 40 are additionally contacted. In this case, as shown in the matrix circuit of Figure 9, in a state that the key Fl is pressed, the switch Hl is concurrently pressed, so that the key sense P port is connected on the circuit. Namely, the keypad Kl port and the key sense A port and the key sense P port are connected, so that the signals (combined signal of KlAP is inputted into and recognized by the key recognition system of the MSM or the micro controller. Here, the Fl switch and the Hl switch are arranged at one key position as shown in Figures 6 and 7. In Figure 9, reference numeral 50 represents a common check key. When any certain common check key is pressed, the key sense P port is connected. In the case that any key of a cellular phone is pressed, the signal is inputted into the common check key 50. While searching a desired menu by pressing the key with a finger and the wishing to select the menu, a corresponding key is strongly

pressed, so that three signals "Kl, A, and P" are inputted into the circuit.

[50] Namely, the common check key 50 is connected with the known key matrix circuit keypad keys Kl through K7, and the key sense P port is connected with the common check key 50 in parallel for thereby constructing the circuit. When a certain key is slightly pressed first, the contact points 37 and 38 are contacted, and the key sense switch is turned on and is connected with the keypad port, so that the signals are transferred.

[51] When a certain key is second strongly pressed, the center contact points 39 and 40 are further contacted, so that the switch of the common check key 50 is turned on, and the key sense P port, the key pad Kl port, and the key sense A port are all connected, so that the signal generated in the circuit is inputted into the MSM or the key recognition (KEYSENSING) system of the micro controller. In the preferred embodiment of the present invention, any key is clicked, the sense P signals is automatically clicked.

[52] In the film type switch according to the present invention, while the user softly touches the keypad like using a mouse, the user presses a certain key on the menu, so that a desired operation can be directly performed for thereby enhancing the use of the system.

[53] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims. Industrial Applicability

[54] In the film type switch according to the present invention, while the user softly touches the keypad like using a mouse, the user presses a certain key on the menu, so that a desired operation can be directly performed for thereby enhancing the use of the system.

[55] As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described examples are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.