WO2006073263A1

WO2006073263A1 - El metal dome sheet for backlight of keypad

Info

Publication number: WO2006073263A1
Application number: PCT/KR2006/000024
Authority: WO
Inventors: Dae Yong Kim
Original assignee: Matrix Co., Ltd
Priority date: 2005-01-05
Filing date: 2006-01-04
Publication date: 2006-07-13
Also published as: KR20060080530A; KR100649647B1

Abstract

An EL sheet using a multi-layer thin sheet and a metal dome sheet using the same are provided. An ITO layer is formed on a primary film, and a base film is fused to the primary film at a bottom thereof to form a multi-layer transparent conductive layer. On the latter, an EL layer is formed in sequence with a bus-bar, fluorescent layer, dielectric layer, bottom electrode layer, and metal lead line. Such an EL has a protective layer covering it that absorbs external shocks and pressure. By using the thin film, the thickness of the keypad can be minimized, and the button feel is more precise with an improved feel. When inks of different characteristics are repetitively printed and heat treated, curling can be prevented by using two layers, and an ESD shield layer prevents damage from static electricity.

Description

Description EL METAL DOME SHEET FOR BACKLIGHT OF KEYPAD

Technical Field

[1] The present invention relates to a keypad backlight unit for a mobile communication terminal or other electronic device, and more particularly, to an EL metal dome sheet capable of providing precise switching operation and having an improved keypad button feel and durability thereof, and an EL metal dome sheet using the same.

[2]

Background Art

[3] A keypad is a switching device for generating signals in mobile communication terminals, remote controllers, and other electronic hardware. The keypad has a separate backlight unit for allowing discernment of letters and numbers on keys at night or in dark conditions.

[4] In the related art, a keypad backlight unit for a mobile communication terminal included a chip light emitting diode (LED) installed on a printed circuit board (PCB) and a reflective film installed on a metal dome sheet to diffuse light from a front surface. In this manner, a keypad backlight is provided for a mobile communication terminal or other electronic device. Such an LED is a point light source, and a light from the LED is reflected by the reflective film and diffused for illumination from the tops of keys. Thus, letters or numbers printed on the surfaces of the keys can be discerned, but light is unevenly illuminated so that visibility of the key tops is degraded, and power consumption is high. To overcome these problems, an electroluminescent (EL) sheet for use as a backlight unit for a mobile communication terminal instead of an LED is being developed.

[5] FIG. 1 is a schematic sectional view of a conventional mobile communication terminal keypad using an EL sheet, and FIG. 2 is a schematic sectional view of the structure of the conventional EL sheet.

[6] Referring to FIG. 1, a keypad includes a front housing 11 and a base 12 coupled to the front housing 11 and having a key top on which numbers, letters, or symbols are printed and a protrusion below the key top for pressing a dome switch. An EL sheet 13 for illuminating a device and a printed circuit board 14 having a metal dome and a separate fixed contact terminal are disposed below the base 12. This type of structure for a conventional keypad has silicon applied to both sides of the EL sheet 13, which is formed integrally with the keypad 12. In this configuration, when the keypad is pressed, the pressure on the metal dome switch plate increases. Also, upon operation, a precise movement of keys is impossible and a feel of the keys is degraded. [7] Referring to FIG. 2, the EL sheet 13 includes a fluorescent layer 23, a dielectric layer 24, a silver electrode 25, and a protective layer 26, which are deposited in sequence on a single ITO-PET film substrate having a PET film 21 and an ITO 22 deposited on the PET film 21. As shown in FIG. 2, the thick ITO-PET film 21 and 22 is used in the EL sheet so that the entire EL sheet 13 becomes thicker, resulting in an overall reduction in a "click" sensitivity. The innate noise and electrostatic discharge (ESD) of the EL sheet 13 cannot be prevented, leading to damage of the unit.

[8]

Disclosure of Invention Technical Problem

[9] An object of the present invention is to provide an EL sheet using a multi-layer thin film and precise movement of keys during operation that provides an improved keypad button feel, and a metal dome sheet using the EL sheet.

[10] Another object of the present invention is to provide an EL sheet and an EL metal dome sheet using the same, capable of preventing curling due to a heat treatment and providing an ESD preventing layer formed so that it is not affected by static electricity.

[H]

Technical Solution

[12] To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided an EL sheet including: a transparent conductive film of a multi-layered structure including a primary film having an ITO layer thereon and a base film fused at a bottom thereof, an EL layer formed to include a bus-bar, a fluorescent layer, a dielectric layer, a bottom electrode layer, and a metal lead line that are sequentially stacked on the transparent conductive film; and a protective layer formed around the EL layer for protecting the EL layer from external shocks and forces.

[13] According to another aspect of the present invention, there is provided an EL sheet including: a multi-layered transparent conductive film formed of PEN (polyethlylene naphthalate) or PET (polyethylene terephthalate) between 5-75 μm thick and including an ITO layer stacked thereon, an ESD (electrostatic discharge) shield layer of an Ag (silver) electrode formed on the bottom surface of the transparent conductive film for ESD shielding; an EL layer formed to include a bus-bar, a fluorescent layer, a dielectric layer, a bottom electrode layer, and a metal lead line that are sequentially stacked on the transparent conductive film; and a protective layer formed around the EL layer for protecting the EL layer from external shocks and forces.

[14] According to a further aspect of the present invention, there is provided an EL metal dome sheet including: the EL sheet constructed as above; a metal dome sheet fused integrally to the EL sheet at a bottom surface thereof and forming holes corresponding to locations of key button portions, a semi- spherical metal dome positioned in the holes and attached to the bottom surface of the EL sheet; an adhesive sheet applied on the bottom surface of the EL sheet so as to fuse the EL sheet and the metal dome sheet; a top tape for fusing the EL sheet and the metal dome sheet; and a release film attached to the bottom surface of the metal dome sheet to protect the metal dome sheet. [15]

Advantageous Effects

[16] The present invention integrally fuses a self-luminous EL sheet with a metal dome sheet and positions a metal dome on a cut metal dome sheet. Thus, an evenly-lit and brighter keypad can be obtained in comparison to a conventional LED. Furthermore, the overall thickness of the keypad is minimized, and the operation of the keys is more precise, with a smoother feel of the keys when they are pressed.

[17] Specifically, a click feel is much improved by apply the adhesive for adhering the

EL sheet and the metal dome sheet on a portion except the position where the metal dome is placed.

[18] Also, a two-layer thin film of PEN, PET, or TPU is formed to create a transparent conductive film, for an improved cushion and click feel and absorbing of external shocks. During te forming of the EL sheet, a second base film, that acts as a supporting layer, prevents curling due to heat deformation and shrinking of film caused by repetitive printing and heat treating using inks of different properties.

[19]

Brief Description of the Drawings

[20] FIG. 1 is a schematic sectional view of a conventional mobile communication terminal keypad using an EL sheet;

[21] FIG. 2 is a schematic sectional view of the structure of a conventional EL sheet;

[22] FIG. 3 is sectional view of the structure of an EL sheet according to the present invention;

[23] FIG. 4 is a flowchart showing the a manufacturing sequence of an EL metal dome sheet according to the present invention;

[24] FIG. 5 is a flowchart showing a manufacturing process of an EL sheet according to an embodiment of the present invention;

[25] FIGs. 6 through 12 and 14 are sectional views showing the structures of EL sheets according to the first through seventh embodiments of the present invention;

[26] FIG. 13 is a flowchart showing a manufacturing process of an EL metal dome sheet according to the seventh embodiment of the present invention; and

[27] FIG. 15 is a sectional view showing a manufacturing process of an EL metal dome sheet according to another embodiment of the present invention. [28]

Best Mode for Carrying Out the Invention

[29] Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

[30] FIG. 3 is sectional view of the structure of an EL sheet according to the present invention, FIG. 4 is a flowchart showing the a manufacturing sequence of an EL metal dome sheet according to the present invention, and FIG. 5 is a flowchart showing a manufacturing process of an EL sheet according to an embodiment of the present invention.

[31] As shown in FIG. 3a, an EL metal dome sheet 1 of the present invention includes an

EL sheet 10, a metal dome sheet 20, a metal dome 30, and a release film 40. The EL sheet 10 and the metal dome sheet 20 are attached together by an adhesive sheet 60 and a top tape 30.

[32] As shown in FIG. 3b, the EL sheet 10 has a structure in which an ITO 120 is deposited on a polyethylene naphthalate (PEN), polyethylene terephthalate (PET), or thermoplastic polyurethane (TPU) film 110, or a structure in which an EL layer 200 having a bus-bar 210, a fluorescent layer 220, a dielectric layer 230, a lower electrode layer 240, and a metal lead layer 250 stacked on a paste -printed transparent conductive film 100 is sealed by a protective layer 260.

[33] An EL sheet uses a transparent conductive film with an ITO layer formed on a PET film. However, compared with the PET film, the present invention uses a transparent conductive film with an ITO layer on a PEN film that is thinner has higher durability and more favorable film characteristics.

[34] The metal dome sheet 20 includes a hole 50 formed for inserting a semi-spherical metal dome 30 acting as a switch and a release film 40 fused at the bottom of the metal dome sheet 20 for protecting the same. Here, the metal dome sheet 20 is a thin, white plate-type insulating sheet for scattered reflection, and is coated at the top with an elastic plastic layer. The metal dome 30 is generally stainless steel and semi-spherical. The release film 40 is a protective film for protecting the adhering surface of the metal dome sheet 20.

[35] Likewise, the EL metal dome sheet 1 of the present invention has the metal dome sheet 20 stacked on the release film 40 and the EL sheet 10 fused on the metal dome sheet 20.

[36] The manufacturing method of this type of EL metal dome sheet 1, as shown in FIG. 4, includes an operation SI l of forming the EL sheet 10, an operation S 12 of forming the metal dome sheet 20 having a hole and being primarily cut together with the EL sheet 10, and operations S 13 to S 16 of fusing the EL sheet and the metal dome sheet, positioning the metal dome, and forming the EL metal dome sheet 1.

[37] Referring to FIG. 4, the operation of forming the EL sheet 10 includes: forming a transparent conductive film; forming an EL layer by stacking a bus-bar, a fluorescent layer, a dielectric layer, a lower electrode layer, and a metal lead line on the transparent conductive film; completely sealing them using urethane ink for protecting the formed EL layer from moisture and outer shocks; and applying adhesive. A detailed description of the manufacturing process of this EL sheet 10 will be given in the next embodiment.

[38] In order to form the EL metal dome sheet using the above-described EL sheet 10, the EL sheet 10 and the primarily-cut metal dome sheet 20 are prepared in operations SI l and S 12. By the primary cutting operation, a hole is formed in the metal dome sheet 20 for attachment of the metal dome 30.

[39] Next, the EL sheet 10 and the metal dome sheet 20 are fused using the adhesive sheet 60 and the top tape 70, the metal dome 30 is placed in the hole 50 of the metal dome sheet 20 fused to the EL sheet 10, and the metal dome 30 is adhered and fixed to the bottom of the EL sheet 10 by means of the top tape 70 in operations S 13 and S 14.

[40] After the release film 40 is attached to the bottom surface of the metal dome sheet

20 in operation S 15, the EL metal dome sheet 1 is cut using a diagram of the mobile communication terminal or other electronic device that it is intended for in operation S16.

[41] The finished EL metal dome sheet 1 can be installed on printed circuit boards of various mobile communication terminals and electronic devices to be used as their keypad backlight.

[42] As shown in FIG. 5, the EL sheet formed integrally with the metal dome sheet of the present invention may be formed on the conductive film according to the process of FIG. 5.

[43] Referring to FIG. 5, a thin transparent conductive film is formed by depositing an

ITO on a multi-layer thin film or printing and drying an ITO paste, and then an EL layer is formed on the transparent conductive film.

[44] The film used in the present invention may be a PEN or PET film; however, because a PEN film is thinner, more durable, and has more favorable film characteristics over a PET film, the PEN film is more favored.

[45] In further detail, the ITO layer is deposited on the PEN film to form a conductive film. For preventing damage from a high resistance, a bus-bar is formed by printing and drying conductive paste on the conductive film in operations S21 and S22. [46] After forming the bus-bar, fluorescent ink (that is made of a fluorescent material and a binder mixed in a weight ratio of about 55:70) is silkscreen printed and then hot air dried between 60 - 150⁰C for 5-10 minutes in operation S23. Here, the color of the radiated light depends on the color of the fluorescent mix, and the thickness is regulated to be around 30 50 μm during the drying process.

[47] Next, a dielectric layer is formed on the fluorescent layer in operation S24. BaTiO is mixed with a binder at an approximate ratio of between 50 70wt% to form a dielectric ink, and the dielectric ink is silkscreen printed and dried for 5-10 minutes at a temperature of 60 - 15O⁰C, so that a dielectric layer having a thickness of about 15-30 μm. Here, the drying process may be a UV drying process, depending on the ink type.

[48] A bottom electrode layer is formed using a carbon paste on the dielectric layer in operation S25. The bottom electrode layer uses a silver (Ag) layer to form a metal lead line for conducting electricity in operation S26. Here, after performing the screen- printing process, drying is implemented.

[49] While not shown in the drawings, according to requirements, an insulating layer may be added on the bottom electrode layer and an EMI shield layer may be formed, then another insulating layer may be formed and an EMI shield layer may be formed between the two insulating layers.

[50] Thus, in order to form the EL layer formed with the sequential fluorescent layer, dielectric layer, bottom electrode layer, and metal lead line, the ink layers are formed; and when the ink layers are completely dried, a PVC sol, UV urethane ink, or urethane acrylate/acrylate monomer ink is applied on the EL layer to completely cover it and create a protective layer in operation S27. Here, during the forming of the protective layer, after silkscreen printing is performed, hot air drying at 90-150⁰C over 5-10 minutes or UV drying may be performed. Here, holes are left open for creating terminals.

[51] Finally, after forming an adhesive layer in operation S28, terminals and guide holes are formed in operation S29. The El sheet formed in the above process is fused with a metal dome sheet 20, to form an EL metal dome sheet 1 , according to the process shown in FIG. 4.

[52] Although the transparent conductive film may be a single layer film configuration for forming the EL sheet, the present invention uses a multi-layer film configuration for the sake of increasing button feel. For this purpose, PEN film, having a reduced thickness, increased durability, and more favorable film characteristics, is used for the multi-layer film configuration of the present invention.

[53] That is, for installation on a mobile phone keypad, operating durability, click feel, thickness, etc., are important factors. Therefore, a thin PEN film is used in a multilayer configuration to prevent the occurrence of curling associated with thin film. Ad- ditionally, an ESD shield layer is formed for minimizing the effects of outer static electricity on a single layer thin film.

[54] In the following first through seventh Embodiments, a more detailed description of the present invention will be given.

[55] First Embodiment

[56] The first embodiment of the present invention relates to a two-layer structured film, which has an EL layer formed on an ITO-PEN or ITO-PET film to form an EL sheet (a sectional view shown in FIG. 6).

[57] Referring to FIG. 6, the conductive film 100 used in the first embodiment of the present invention forms a two-layer structure with a PEN film 110 or PET film 130 having a thickness of 5-75 μm and a removable adhesive or an adhesive 141 having a thickness of 5-75 μm attached thereon, then forms an ITO layer 120 by applying or paste printing an ITO on top of the base film 110 at the upper portion, and forms an EL sheet 10 through forming an EL layer 200 according to the process in FIG. 5.

[58] Here, the removable adhesive, when broadly categorized, falls into the category of adhesives, but has distinctly different characteristics to those of other adhesives. That is, when a normal adhesive passes a certain phase, it goes from a liquid state where it pulls an object to be adhered, and then solidifies. In comparison, a removable adhesive is always in a liquid state.

[59] The EL layer 200 includes a bus-bar 210 formed by a conductive paste that is printed and dried on a base film 110 and an ITO layer 120, a fluorescent layer 220 formed by fluorescent ink that is silkscreen printed and dried, a dielectric layer 230 formed by dielectric ink that is silkscreen printed and dried to a thickness of around 15-30 μm, a bottom electrode layer 240 formed using carbon paste, and a metal lead line 250 formed using a silver (Ag) paste on the bottom electrode layer 240. In order to protect the EL layer 200 formed with the fluorescent layer 220, dielectric layer 230, bottom electrode layer 240, and metal lead line 250, a PVC sol, UV urethane ink, or urethane acrylate/acrylate monomer ink is applied to form a protective layer 260 that completely covers the EL layer 200.

[60] As in the structure of the first embodiment shown in FIG. 6, a first base film 130 with a thickness of 5-75 μm, a removable adhesive or adhesive 141 layer with a thickness of 5-75 μm, a transparent conductive film 100 formed by depositing an ITO layer 120 on a base film 110 with a thickness of 5-75 μm, a silver electrode 210 and fluorescent layer 220 on the transparent conductive film 100, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 are sequentially stacked to form an EL layer 200, which is coated on the outside by a protective layer 260.

[61] Such a two-layer type conductive film 100 with a base film and a first base film has an EL layer 200 formed thereon. When an EL sheet and an EL metal dome sheet are manufactured, the removable adhesive or adhesive 141 between the films functions as a shock absorber to provide an improved cushioned and click feel and absorb external shocks for superb operating durability.

[62] Second Embodiment

[63] In the second embodiment of the present invention, the transparent conductive film is formed in a two-layered structure to prevent heat deformation or shrinking of the EL sheet, and the two-layered EL sheet forming an EL layer on an ITO-PEN or an ITO- PET film according to the second embodiment is shown in FIG. 7.

[64] Referring to FIG. 7, the conductive film 100 used in the second embodiment of the present invention is a two-layer film with a film 110 of 5-75 μm fused with a film 160 of 10-125 μm. A base film 110 coated with a release material 150 such as silicon is formed on the bottom surface of a 5-75 μm thick PEN or PET film, and a 10-125 μm thick second base film 160 having an applied acrylic removable adhesive 142 that is 10-50 μm thick is fused to the removable adhesive- treated base film 110, and an ITO is deposited or paste printed on the base film 110 to form an ITO layer 120.

[65] The EL layer 200 is formed in the same way as the previous embodiment, and includes (as shown in FIG. 7) a second base film 160 10-125 μm thick, an acrylic removable adhesive 142 10-50 μm thick, an ITO layer 120 deposited on a 5-75 μm thick base film 110 coated with a silicon release material 150 forming a transparent conductive film 100, a silver electrode 210 and a fluorescent layer 220 on the transparent conductive film 100, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 stacked sequentially to form an EL layer 200. A protective layer 260 is formed on the outside of the EL layer 200.

[66] Such a two-layer type conductive film 100 has an EL layer 200. When an EL sheet is manufactured, when inks having different characteristics are repeatedly printed and heat treated on a conventional single layer ITO-PEN or ITO-PET film, curling caused by heat deformation and shrinkage of film can occur, which the second base film 160 (as a supporting layer) functions to prevent.

[67] Third Embodiment

[68] The third embodiment of the present invention includes a transparent conductive film attached to a bottom surface of a two-layered ITO-PEN or an ITO-PET film that is fused with release adhesive and acrylic removable adhesive on its bottom surface, for an improved cushioned and click feel. When an EL layer is manufactured, a three- layer structure functions to support, reinforce, and prevent heat deformation and shrinking of the EL sheet. The surface structure of the EL sheet forming the EL layer of the ITO-PEN or ITO-PET film of the three-layer structure is shown in FIG. 8.

[69] Referring to FIG. 8, the conductive film 100 used in the third embodiment of the present invention has a two-layer film formed with base film 110 and a first base film 130 from a PEN or a PET film 110 or 130 that is 5-25 μm thick attached to a removable adhesive or an adhesive 141 that is 5-75 μm thick; then coats the rear of the first base film 130 with silicon release material 150; and applies a 10-50 μm thick acrylic removable adhesive 142 to the first base film 130, and fuses the second base film 160 that is 10-125 μm thick; and deposits or paste prints an ITO over the base film 110 to form an ITO layer 120.

[70] The EL layer 200 is formed in the same manner as described in the previous embodiment, and in the third embodiment (as shown in FIG. 8), a 10-125 μm thick second base film 160, a 10-50 μm thick acrylic removable adhesive 142, a 5-25 μm thick first base film 130 coated with a silicon release material 150, a 5-75 μm thick removable adhesive or adhesive layer 141, and a 5-25 μm thick base film 110 have an ITO layer 120 stacked on top to form a transparent conductive film 100; on the transparent conductive film 100 are a silver electrode 210 and fluorescent layer 220, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 that are sequentially stacked forming an EL layer 200; and a protective layer 260 formed around the EL layer 200.

[71] When manufacturing an EL sheet by forming an EL layer 200 on a three-layer conductive film 100, the heat deformation and curling of the conventional single layer ITO-PEN or ITO-PET film structure caused by repeated printing and heat treating of ink having different characteristics is prevented by the second film 130 that acts as a reinforcing layer. By forming the EL layer 200 on the three-layer type conductive film 100 and forming the EL sheet and the EL metal dome sheet, the removable adhesive or adhesive 140 between the films acts as a shock absorber to enhance the cushion and click feel and absorb external shocks to improved operational reliability.

[72] Fourth Embodiment

[73] The fourth embodiment uses a silicon removable adhesive for fusing the base film with the second base film to remove the release film treated on the base film, and is a simple structure for manufacturing a two-layer type transparent conductive film. An EL sheet sectional structure is shown in FIG. 9.

[74] Referring to FIG. 9, the conductive film 100 used in the fourth embodiment of the present invention is a two-layer structure with a 5-75 μm thick film 110 fused to a 10-125 μm thick film 160. A second base film 160 of 10-125 μm thick is fused to a 5-75 μm thick base film 110 with a 5-100 μm thick silicon removable adhesive 143, and an ITO layer 120 is formed by depositing or paste printing an ITO on the base film 110.

[75] The EL layer 200 is formed in the same manner as the previous embodiments, and in the fourth embodiment as shown in FIG. 9, an ITO layer 120 is staked on a 10-125 μm thick first base film 160, a 5-100 μm silicon removable adhesive 143, and a 5-75 μm thick base film 110, to form a transparent conductive film 100; and on the transparent conductive film 100, a silver electrode 210 and fluorescent layer 220, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 are sequentially stacked to form an EL layer 200; and a protective layer 260 is formed around the EL layer 200.

[76] When the EL layer 200 is formed on the two-layer thin conductive film 100 to form the EL sheet, the structure and the manufacturing process are simple, and curling of film caused by heat deformation and shrinking thereof due to repeated printing and heat treating of ink having different characteristics is prevented by the second base film 160 that acts as a supporting and reinforcing layer.

[77] Fifth Embodiment

[78] The fifth embodiment of the present invention uses a silicon removable adhesive to fuse the first base film to the second base film and removes the release layer treated on the first base film for a simplified three-layer structured transparent conductive film. FIG. 10 shows a sectional structure of the EL sheet according to the fifth embodiment.

[79] Referring to FIG. 10, the conductive film 100 used in the fifth embodiment of the present invention includes a 5-25 μm thick PEN or PET film 110 or 130 attached with a 5-75 μm thick removable adhesive or adhesive 141 to form a two-layer base film 110 and first base film 130. A 5-100 μm thick silicon removable adhesive 143 is applied to the bottom surface of the first base film 130, to which a 10-125 μm thick second base film 160 is fused. An ITO is deposited or paste printed on the base film 110 to form an ITO layer 120.

[80] The EL layer 200 in the fifth embodiment (as shown in FIG. 10) is formed in the same manner as in the previous embodiments, and includes a 10-125 μm thick second base film 160, a 5-100 μm thick silicon removable adhesive 143, a 5-25 μm thick first base film 130, a 5-75 μm thick removable adhesive or adhesive 141, and a 5-25 μm thick base film 110, on which an ITO layer 120 is stacked forming a transparent conductive film 100. A silver electrode 210 and a fluorescent layer 220, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 are sequentially stacked on the transparent conductive film 100 to form an EL layer 200. A protective layer 260 is formed around the EL layer 200.

[81] When manufacturing an EL sheet by forming an EL layer 200 on a three-layer conductive film 100, the structure and manufacturing process are simplified, and curling due to heat deformation and shrinking caused by repeated printing and heat treating of ink having different characteristics is prevented by the second film 130 that acts as a reinforcing layer. By forming the EL layer 200 on the three-layer type conductive film 100 and forming the EL sheet and the EL metal dome sheet, the removable adhesive 140 layer between the films acts as a shock absorber to enhance the cushion and click feel and absorb external shocks to improved operational reliability.

[82] Sixth Embodiment

[83] The two-layer transparent conductive film of the sixth embodiment of the present invention adds an ITO-PEN or ITO-PET FILM to a thermoplastic urethane (TPU) film with a removable adhesive to act as a support and reinforcement and prevent heat deformation and shrinking of the EL sheet and improve click feel (due to the flexibility of the TPU film) and shock absorbing ability of external shocks. The two-layer transparent conductive film using the TPU film of the sixth embodiment has an EL layer formed thereon to form an EL sheet. A sectional view of the EL sheet is shown in FIG. 11.

[84] Referring to FIG. 11, the conductive film 100 used in the sixth embodiment of the present invention is a two-layer structure with a 5-100 μm thick TPU film 170 fused to a 10-125 μm thick PEN or PET film. The base film 170 coated with a silicon release material 150 is formed on the bottom surface of the 5-100 μm thick TPU film, and a second base film 160 having a thickness of approx. 10-125 μm and having an acrylic removable adhesive 142 is fused with the base film 170 treated with the release material. An ITO layer 120 is formed by depositing or paste printing an ITO on the base film 170.

[85] The EL layer 200 is formed in the same manner as the previous embodiments, and in the sixth embodiment as shown in FIG. 11, an ITO layer 120 is stacked on a 10-125 μm thick second base film 160 of PEN or PET, a 10-50 μm acrylic removable adhesive 142, and a base film of a TPU film with a thickness of about 5-100 μm coated with a silicon release material 150, to form a transparent conductive film 100; and on the transparent conductive film 100, a silver electrode 210 and fluorescent layer 220, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 are sequentially stacked to form an EL layer 200; and a protective layer 260 is formed around the EL layer 200.

[86] When the EL layer 200 is formed on the two-layer thin conductive film 100 to form the EL sheet, and curling of film in a conventional single ITO-PEN or ITO-PET film caused by heat deformation and shrinking thereof due to repeated printing and heat treating of ink having different characteristics is prevented by the second base film 160 that acts as a supporting and reinforcing layer. Also, the TPU film has a high flexibility, enabling an improved click feel and absorption of external shocks for better operational reliability.

[87] Seventh Embodiment

[88] The seventh embodiment uses the two layers of the fourth embodiment to form a transparent conductive film and an EL layer, then removes a second base film treated with removable adhesive and fused to a base film, and forms an ESD shield layer on a bottom surface thereof for providing static electricity shielding. A sectional structure of the EL sheet according to the seventh embodiment is shown in FIG. 12.

[89] Referring to FIG. 12, the seventh embodiment of the present invention uses a silver

(Ag) electrode ESD shield layer 300 formed on a base film 110 of a PEN or PET film having a thickness of 5-75 μm. That is, a silver electrode ESD shield layer 300 is formed on the bottom surface of the base film 110, and an ITO layer 120 is stacked on top of the base film 110 to form a transparent conductive film 100. On top of the transparent conductive film 100 a silver electrode 210 and a fluorescent layer 220, a dielectric layer 230, a bottom electrode layer 240, and a metal lead line 250 are sequentially stacked to form an EL layer 200. A protective layer 260 covers the outer portion of the EL layer 200.

[90] FIG. 13 is a flowchart showing a manufacturing process of an EL metal dome sheet according to the seventh embodiment of the present invention.

[91] Referring to FIG. 13, in order to form a transparent conductive film, the EL sheet

10 according to the seventh embodiment first prepares a thin PEN or PET film as a base film and a second base film that has or has not been heat treated. Then, a 5-100 μm thick silicon removable adhesive is applied to the end surface of the second base film to removable adhesive-treat the second base film. Next, a two-layer film is formed in operations S31 and S33 by adjusting the tension and line speed of the base film and the removable adhesive-treated second base film.

[92] In operation S34, an ITO is coated or paste printed on the base film of the transparent conductive film fused with the base film and the second base film to form a two-layer transparent conductive film. An EL layer is formed on the transparent conductive film having the ITO layer according to the process shown in FIG. 5 to form an EL sheet in operation S35.

[93] The metal dome sheet is fused to the EL sheet and the metal dome is positioned according to the process shown in FIG. 4, and the removable adhesive-treated second base film is removed from the two-layer film in operations S36-S38. A silver electrode for ESD shielding is printed in operation S39 on the base film with the second base film removed. Here, the second base film is removed, and the silver electrode for ESD shielding is printed in operations S38 and S39. Then, the metal dome sheet is fused and the metal dome may be positioned in operations S36 and S37.

[94] After forming the ESD shielding layer, a release film for protecting a metal dome sheet is fused to the back surface of the metal dome sheet, and the metal dome sheet is cut and finished according to the blueprint of the mobile communication terminal or other electronic device that the sheet will be used in operations S40 and S41.

[95] That is, as shown in FIG. 12, the EL sheet of the EL metal dome sheet according to the above forming process is formed of a structure including a 5-75 μm thick thin base film 110 on which a transparent conductive film 100 with an ITO layer 120 is formed, and an EL layer 200 formed on the transparent conductive film 100, and an ESD shield layer 130 is formed on a back surface of the base film 110 for ESD shielding.

[96] The EL sheet formed with the ESD shield layer of the seventh embodiment shares a similar structure with those shown in FIGs. 4 and 5, where the second base film that is fused to the first base film is removed, and the ESD layer may be formed on the back of the first base film.

[97] Using the three-layer structure in the fifth embodiment, a transparent conductive film and an EL layer are formed. Then, the second base film that is silicon removable adhesive-treated and fused to the first base film is removed, and the ESD shield layer is formed on the back of the first base film for ESD shielding. This structure of a transparent conductive film is shown in FIG. 14.

[98] Referring to FIG. 14, the structure of the seventh embodiment using three layers and forming an ESD shield layer includes a thin base film 110 of 5-25 μm thick, on which an ITO layer 120 is formed. At the back surface of the base film 110, a 5-25 μm thick first base film 130 is attached with removable adhesive or adhesive 141, and an ESD shield layer 300 with a silver electrode printed thereon is formed on the back of the first base film 130 (that has the silicon removable adhesive-treated second base film removed therefrom).

[99] The seventh embodiment uses a two- or three-layer thin film to form a conductive film on which an EL layer is formed. When this is then used to form an EL sheet and an EL metal dome sheet, curling of film in a conventional single ITO-PET film caused by heat deformation and shrinking thereof due to repeated printing and heat treating of ink having different characteristics is prevented by the second base film that acts as a supporting and reinforcing layer. Also, the forming of the transparent conductive film is simplified due to the base film of the thin film not being release material treated. By forming an ESD shield layer on the base film with the second base film removed, the device can be protected from static electricity, to allow production of a thinner EL sheet and EL metal dome sheet.

[100] FIG. 15 is an exploded sectional view showing a structure of an EL metal dome sheet according to an embodiment of the present invention.

[101] Referring to FIG. 15, the EL metal dome sheet includes an EL sheet 10, a metal dome sheet 20, a metal dome 30, and a release film 40. The EL sheet 10 and the metal dome sheet 20 are fused by means of an adhesive sheet 60 and a top tape 70.

[102] The adhesive sheet 60 is formed by applying an adhesive on a protective layer 260 of the EL sheet 10. As shown, in order to place the metal dome 30, a space 61 is formed at the same position such that it is matched with a hole 50 defined on the metal dome sheet 20. That is, in the process of manufacturing the EL sheet and applying an adhesive, the adhesive is applied on a portion except the hole 50 where the metal dome is placed. In this manner, the space 61 identical to the hole 50 of the metal dome sheet is defined.

[103] By forming the space 61 in the adhesive sheet 60, a click feel is improved when manipulating the keypad. Also, by increasing the thickness of the metal dome sheet 20, a click feel is much improved. The metal dome sheet may be formed to a thickness of 0.06 mm to 0.2 mm.

[104] Additionally, a multi-layer is used to form an EL sheet, after which the supporting second base film is removed, and a silver electrode ESD shield layer is formed to prevent static electricity-induced damage to the device.

[105] It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.

[106]

Claims

[ 1 ] An EL sheet comprising: a transparent conductive film of a multi-layered structure including a primary film having an ITO layer thereon and a base film fused at a bottom thereof, an EL layer formed to include a bus-bar, a fluorescent layer, a dielectric layer, a bottom electrode layer, and a metal lead line that are sequentially stacked on the transparent conductive film; and a protective layer formed around the EL layer for protecting the EL layer from external shocks and forces.

[2] The EL sheet of claim 1 , wherein the primary film and the base film are respectively a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 5-75 μm thick, and the base film has a removable adhesive or an adhesive layer between 5-75 μm thick formed on a bottom thereof.

[3] The EL sheet of claim 1, wherein the primary film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 5-75 μm thick and has a silicon release coating treatment applied to a bottom surface thereof, and the base film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 10-125 μm thick having an acrylic removable adhesive between 10-40 μm thick applied to a bottom surface thereof.

[4] The EL sheet of claim 1 , wherein the primary film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 5-75 μm thick and has a silicon removable adhesive between 5-100 μm thick applied to a bottom surface thereof, and the base film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 10-125 μm thick.

[5] The EL sheet of claim 1, wherein the primary film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 5-25 μm thick and has a removable adhesive or adhesive between 5-75 μm thick applied to a bottom surface thereof, and the transparent conductive film further includes: a first base film formed of PEN (polyethlylene naphthalate) or a PET

(polyethylene terephthalate) between 5-25 μm thick and having a silicon release coating applied to a bottom surface thereof; an acrylic removable adhesive between 10-50 μm thick and stacked below the silicon release coating of the first base film; and a second base film formed of PEN (polyethlylene naphthalate) or a PET

(polyethylene terephthalate) between 10- 125 μm thick fused to the first base film.

[6] The EL sheet of claim 1 , wherein the primary film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 5-25 μm thick and has a removable adhesive or adhesive between 5-75 μm thick applied to a bottom surface thereof, and the transparent conductive film further includes: a first base film formed of PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) between 5-25 μm thick and having a silicon removable adhesive applied to a bottom surface thereof; and a second base film formed of PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) between 10-125 μm thick fused to the first base film.

[7] The EL sheet of claim 1, wherein the primary film is a TPU (thermoplastic urethane) film between 5-75 μm thick and has a silicon release coating applied to a bottom surface thereof, and the base film is a PEN (polyethlylene naphthalate) or a PET (polyethylene terephthalate) film between 10-125 μm thick, the base film having a 10-50 μm thick acrylic removable adhesive applied thereon.

[8] An EL sheet comprising: a multi-layered transparent conductive film formed of PEN (polyethlylene naphthalate) or PET (polyethylene terephthalate) between 5-75 μm thick and including an ITO layer stacked thereon, an ESD (electrostatic discharge) shield layer of an Ag (silver) electrode formed on the bottom surface of the transparent conductive film for ESD shielding; an EL layer formed to include a bus-bar, a fluorescent layer, a dielectric layer, a bottom electrode layer, and a metal lead line that are sequentially stacked on the transparent conductive film; and a protective layer formed around the EL layer for protecting the EL layer from external shocks and forces.

[9] An EL sheet comprising: a transparent conductive film of a multi-layered structure including a primary film between 5-25 μm thick having an ITO layer stacked thereon, a removable adhesive or an adhesive between 5-75 μm thick formed on a bottom surface of the primary film, and a first base film of PEN (polyethlylene naphthalate) or PET (polyethylene terephthalate) between 5-25 μm thick attached to the primary film; an ESD (electrostatic discharge) shield layer of an Ag (silver) electrode formed on the bottom surface of the transparent conductive film for ESD shielding; an EL layer formed to include a bus-bar, a fluorescent layer, a dielectric layer, a bottom electrode layer, and a metal lead line that are sequentially stacked on the transparent conductive film; and a protective layer formed around the EL layer for protecting the EL layer from external shocks and forces. [10] An EL metal dome sheet comprising: the EL sheet of any one of claims 1 through 9; a metal dome sheet fused integrally to the EL sheet at a bottom surface thereof and forming holes corresponding to locations of key button portions, a semi-spherical metal dome positioned in the holes and attached to the bottom surface of the EL sheet; an adhesive sheet applied on the bottom surface of the EL sheet so as to fuse the

EL sheet and the metal dome sheet; a top tape for fusing the EL sheet and the metal dome sheet; and a release film attached to the bottom surface of the metal dome sheet to protect the metal dome sheet. [11] The EL metal dome sheet of claim 10, wherein the adhesive sheet forms a space at a position matched with the hole formed in the metal dome sheet. [12] The EL metal dome sheet of claim 11, wherein the metal dome sheet has a thickness of 0.06 mm to 0.2 mm.