Keyboard cover with electrostatic discharge dissipation

Abstract

A plastic keypad having data input elements (14, 16, 18, 20) and at least one display element (12) is protected from electrostatic discharge by an assembly (19) having a cover substrate (32) with an electrically conductive arrangement (34, 36, 38, 40, 46, 48) disposed thereon. The cover substrate (32) has a top side and a back side and has precisely located vias (60) formed therethrough. The top surface of the top side is an electrically conductive polymer layer (40). The back side is printed with at least one layer of colored ink (44) that depicts a plurality of alphanumeric and graphic elements (14, 16, 18, 20) of a keypad (70). The electrically conductive arrangement (34, 36, 38, 40, 46, 48) is disposed on the cover substrate (32) for collecting electrostatic charges on the top side, transferring the electrostatic charges through the plurality of vias (60) to the back side, and discharging the transferred electrostatic charges to ground.

Description

Technical Field

[0001] This invention relates to a cover for a data input and display keyboard for an electronic device, the cover being suitable for dissipating static charge that may occur during keyboard use. While it can be used in any environment, the cover incorporating this invention provides an electronic device with a keyboard that meets or exceeds standardized testing, enabling it to be used in environments where a sudden flow of electrons through a gap could ignite a flammable mixture and thus cause a fire or explosive flame front. Background Technology

[0002] All equipment designed for operation in hazardous environments must be designed to withstand ignition sparks that could ignite a flame, or, if the flame can propagate, cause an explosion. Almost every industry has hazardous environments that must be considered. Explosions of oil and gas are known to occur in coal mines and grain haulage elevators. Vapors of substances such as gasoline, surgical anesthetics, and ethanol are also known to explode in the event of electrostatic discharge (“ESD”), where a flow of electrons suddenly passes through a gap. The fire on the Apollo 1 spacecraft was caused by a spark igniting the 100% oxygen environment inside the capsule while it was on the launch pad. Most people associate ESD with lightning, but even a discharge of only a few centimeters can generate enough current to ignite an explosion in a hazardous environment. Furthermore, electronic components such as hard drives and integrated circuits are highly susceptible to ESD.

[0003] In known technologies, plastic insulating materials are commonly used to manufacture keyboard / monitor covers that are attached to the exterior of a metal device housing. Due to their chemical properties, plastic covers can collect and retain high-energy static charges, which can then be suddenly discharged, generating potentially dangerous ignition sparks unless protective measures are taken to release or dissipate the static charge as it appears.

[0004] In some existing solutions, an indium tin oxide (ITO) layer has been applied to keyboard components to prevent electromagnetic interference (EMI) in some solutions to this problem.

[0005] One objective that has not yet been achieved in the prior art is to provide a multi-layer keyboard assembly in which charge is discharged into the conductive inner layer of the keyboard assembly, and from the conductive inner layer to the metal housing of a device connected to the keyboard assembly. The charge is then grounded from the metal housing. Summary of the Invention

[0006] The aforementioned and other objectives of the prior art can be achieved by a component for protecting a plastic keyboard from electrostatic discharge. Such a component, used to protect a plastic keyboard having data input elements and at least one display element, includes a cover substrate having a top side and a back side. The cover substrate also includes a plurality of precisely positioned through-holes formed therethrough. The top side has a top surface coated with a conductive polymer layer, and the back side has a back surface printed with at least one layer of colored ink depicting a plurality of alphanumeric and graphic elements of the keyboard. A conductive arrangement structure is disposed on the cover substrate for collecting static charge on the top side, transferring the static charge to the back side through the plurality of through-holes, and discharging the transferred static charge to ground.

[0007] In some embodiments, the conductive arrangement structure includes: at least one first conductive grid printed on a top surface of a cover substrate beneath a conductive polymer layer, the at least one first conductive grid dividing the top surface into a plurality of enclosing regions, each enclosing region being equal to or smaller than a predetermined size, each first conductive grid including a plurality of nodes, each node being located on top of and extending into a corresponding of a plurality of precisely positioned vias; at least one second conductive grid printed on a back surface of a cover substrate beneath the at least one colored ink layer, such that the size and shape of each second conductive grid corresponds to one of the first conductive grids, each second conductive grid including a plurality of nodes, each node being located below and extending into a corresponding of a plurality of precisely positioned vias; and at least one metal sheet connecting each second conductive grid to ground.

[0008] In some embodiments, each of the first conductive grid and the second conductive grid includes a segment of conductive paste printed on the cover substrate.

[0009] In some embodiments, a layer of colored ink is applied on top of a conductive paste segment in each first conductive grid.

[0010] In some embodiments, each node of the first conductive grid includes: a plug of conductive polymer applied from the top side of the cover substrate into each precisely positioned via, the plug having a body portion extending into the via and a flange portion having a diameter larger than the diameter of the via, and the flange portion extending on the top surface of the cover substrate. A conductive paste segment is applied on top of the plug, and a colored ink segment is applied on top of the conductive paste segment.

[0011] In several embodiments of these examples, each node of the second conductive grid includes a portion of conductive paste extending from the underside of the cover substrate into a via that associates it with a corresponding node of the first conductive grid capable of electrical contact.

[0012] In several of these embodiments, the cover matrix comprises a non-conductive polymer.

[0013] In some embodiments, the non-conductive polymer is polyethylene terephthalate (“PET”) sheet.

[0014] In several of these embodiments, the electrostatic dissipative coating is transparent.

[0015] In some embodiments, the electrostatic dissipative coating has a transparency Y of up to 90% at d = 100 nm.

[0016] In some embodiments, the electrostatic dissipative coating is a composite of substituted polythiophene and anions, with an electrical conductivity in the range of 1000 Siemens per centimeter (S / cm).

[0017] In some embodiments, one of the plurality of first conductive meshes is a conductive mesh having vias located around the periphery of the cover substrate.

[0018] In some embodiments, the area corresponding to each data input element of the keyboard is surrounded by at least one of the first conductive grids.

[0019] Other aspects of the inventive concept are realized by an electronic device for data input and display, the electronic device comprising: a housing, and a keyboard for data input and display mounted on the housing. The electronic device also includes a cover as described above, the cover being disposed on top of the keyboard and fixed in position by the housing, the cover being suitable for dissipating static charge generated during keyboard use.

[0020] In some embodiments, the housing is metallic, and static charge dissipated by the covering is discharged into the housing. Attached Figure Description

[0021] The inventive concept will be better understood by referring to the accompanying drawings, in which the same parts are identified by the same reference numerals:

[0022] Figure 1 This is a top plan view of an assembled keyboard assembly including the keyboard cover of the present invention;

[0023] Figure 2 It is along Figure 1 The side sectional view of the keyboard assembly including the cover, taken by line 2-2 in the figure;

[0024] Figure 3 yes Figure 2 An enlarged view of a portion of the image shows the operational features of the keyboard with a keyboard cover.

[0025] Figure 4This is a top plan view of the substrate, showing the location of the vias in the substrate;

[0026] Figure 5 This is a bottom plan view of the conductive paste layer deposited on the bottom surface of the covering substrate;

[0027] Figure 6 It is an enlarged side cross-sectional view of the cover showing the perforations and all printed layers; and

[0028] Figure 7 This is a top plan view of the back adhesive layer of the keyboard cover. Detailed Implementation

[0029] Figure 1 An embodiment of a keyboard assembly 10 is shown in a top plan view, the keyboard assembly 10 comprising a keyboard with a cover for dissipating static charge. The keyboard shown here is merely an example of a cover for implementing the invention; due to its transparent nature, the cover is not easily noticed by the user, but as the cover approaches the end of its service life, some features become apparent to the user, showing visual signs that it needs replacement. Although the described embodiment of the keyboard assembly 10 shows a typical selection and arrangement of keyboard elements, it should be readily understood that other possible selections and arrangements of keyboard elements remain effective embodiments of the inventive concept, as the cover itself plays a very passive but effective role in the operation of the keyboard assembly 10. To illustrate the inventive concept, the minimum set of elements includes: at least one display element 12, which is described herein as a screen, and a plurality of data input elements, such as an on / off button 14, a numeric keypad 16 with buttons for the numbers 0 to 9, a set 18 of four directional arrows with an "input" button arranged in the center, and a plurality of function buttons 20. In the remaining figures, especially in Figure 2 As can be seen, the keyboard's functional parts are located below the cover itself, which is indicated by reference numeral 30 in the figure.

[0030] Next, turn to Figure 2 The covering 30 is based on and forms the structural basis of the covering substrate 32, which is generally flat and has a top side and a back side. Figure 2 In the diagram, the top side of the substrate 32 is its right side, and the back side is its left side. Multiple ink layers and coatings are applied to the top and back sides. To clearly show these inks and coatings, Figure 2Not drawn to scale. However, the cover substrate 32 is the thickest part of the cover 30. It is formed of a transparent polymer material, preferably polyethylene terephthalate. An exemplary cover substrate 32 is a textured hard-coated polyester film commercially sold by MacDermid Autotype Inc. under the trademark AUTOTEX. Essential to the function of the cover 30 are the plurality of vias 60 formed in the cover substrate 32. Some of these vias 60 are as follows: Figure 2 As shown. Based on the predetermined layout of the display elements and data input elements of the specific keyboard on which the cover 30 is installed, each via 60 is precisely sized and arranged on the base 32. These vias 60 will be referred to below. Figures 4 to 6 Let's discuss this.

[0031] After the via 60 is formed, a conductive ink pad 34 is applied to the top side of the cover substrate 32 to allow ink to flow into the via from the top side, at least partially filling the via. A suitable pad may be CLEVIOS F DX 2 / XL 2K, which is commercially available from Heraeus Deutschland GmbH & Co.

[0032] The pattern 36 of conductive silver paste is selectively applied on top of the conductive ink 36. Figures 4 to 6 This will provide a better understanding of the details of the selective pattern 36, but it is important to note now that the silver paste is arranged on top of the vias, typically in interconnected lines. Conductive silver paste is known in the industry, with ACHESON 8208 being a typical example.

[0033] A pattern 38 of colored ink is applied on top of a pattern 36 of conductive silver paste to reduce the visibility of the pattern 36 when viewed from the top of the keyboard assembly. Figure 1 In this design, pattern 38 includes interconnected linear elements that define boundaries around display element 12 and various data input elements 14, 16, 18, and 20. Like the conductive silver paste, colored inks are also commonly used in the industry and are well-known to those skilled in the art. One example is the JUJO 900 series inks.

[0034] The next layer from the top side of the substrate 32 outwards is a coating 40 of conductive polymer material. This coating provides the main surface touched by the user, and therefore is an electrostatic dissipative material. The material suitable for this coating 40 is a protective CLEVIOS hard coating, commercially available from Heraeus Deutschland GmbH & Co. KG, where CLEVIOS is a registered trademark for its conductive polymer chemistry. According to Heraeus' website, CLEVIOS PEDOT / PSS is a composite of substituted polythiophene and anions with a conductivity in the range of 1000 Siemens per centimeter (S / cm). It can be used for extremely thin conductive coatings. The coating has good chemical stability and a transparency of up to 90% Y at d = 100 nm. The material has good thermal and UV stability. The website claims that CLEVIOS is an antistatic coating that can be used to protect integrated circuit packaging trays from ESD damage to sensitive electronic components. The website indicates that many plastics, including polycarbonate, polyethylene, polyethylene terephthalate, polyamide, and polypropylene, can be coated with CLEVIOS.

[0035] The final layer on the top side of the substrate 32 is a thin insulating layer formed of optical ink 42. Preferably, it is applied only to the area of ​​the display element 12 projected onto the electrostatic dissipative coating 40. Although the optical ink 42 is applied to clean the display window, it does pose a risk of charge buildup again. To mitigate charge buildup in this area, a suitable approach is to minimize the surface area of ​​the insulating layer or introduce an interlaced mesh of apertures to promote low-energy flashover discharge, preventing it from accumulating to levels that could cause ignition. An exemplary material for this layer is WINDOTEX material, available from MacDermid Autotype Inc.

[0036] Continue reading Figure 2 Next, the back side of the cover substrate 32 will be described. Preferably, at least one layer of colored ink 44 is coated on the surface of the back side to provide a background color for the cover substrate, and the back side is marked with multiple contrasting colored symbols to provide numbers for the numeric keypad, etc. Obviously, no colored ink is applied to the area of ​​the display element. It is preferable to apply this layer 44 before the vias are formed in the substrate, because the colored ink layer can be used as an alignment tool for the vias.

[0037] After applying the colored ink layer 44 and forming the vias, a conductive silver paste pattern 46 is selectively applied to the back side, outside the colored ink layer. This selective pattern 46 effectively mirrors the conductive silver paste pattern 36. Figure 5 and 6Further details will be provided in the description. Like pattern 36, the conductive silver paste 46 can be a material sold by ACHESON 8208. As will be shown below, the static charge appearing on the top side of the cover substrate 32 will migrate to the conductive silver paste 36, be discharged through the via 60 to the bottom side of the cover substrate, and be collected by the conductive silver paste 46. The interconnectivity of the silver paste 46 will cause the charge to move to a grounding plate.

[0038] Extending outward from the back side of the cover substrate 32, an adhesive layer 48 is provided, allowing the cover 30 and its individual layers to be adhered to the keyboard 70, which will now be described. Since the cover 30 is consumed during use, it is designed to be easily replaceable. The adhesive is preferably a double-sided pressure-sensitive adhesive on a polymer film. It should be noted that no adhesive is applied to the area containing the display area.

[0039] Below adhesive layer 48 is the mechanical embodiment of keyboard 70, which provides display and data input elements. Below that is another adhesive layer 72, used to adhere keyboard assembly 10 to a metal device housing (not shown) containing the electronic components of the device. Most features of the keyboard are... Figure 3 It is shown in a magnified manner, while Figure 2 A transparent keyboard spacer 74 is shown, through which the display element 12 can be seen. Polymer sheets, especially polycarbonate materials, are commonly used as the keyboard spacer 74.

[0040] Next to Figure 3 , it is Figure 2 A partial enlarged view shows the operational features of a keyboard using a keyboard cover. As shown from right to left in the figure, the upper layer 76 of the keyboard is a polymer layer, typically polyethylene terephthalate, such as LUMIRROR T60 polyester sold by Toray Industries Ltd. It is noteworthy that this upper layer 76 is selectively cut to facilitate the physical movement of a metal dome 78, which is located beneath a single data input element. The metal dome 78, along with an adhesive-containing interlayer 80, is arranged between the upper layer 76 and a circuit layer 82, which typically has the same composition as the upper layer 76. A further adhesive layer 84 adheres the circuit layer 82 to the circuit spacer layer 86.

[0041] Figure 4 This is a top plan view of the covering substrate 32, showing the location of the through-holes 60 formed in the covering substrate. In this figure, structures such as the display element 12, the on / off button 14, the numeric keypad 16, the directional arrow set 18, and the function button set 20 are capable of... Figure 1The diagram shows the boundaries of the surface area of ​​the cover substrate 32, divided into enclosed regions by multiple dashed lines. Due to the coating on top of the cover substrate 32, the "area" is actually a "volume," although the depth is small relative to the width and breadth. Therefore, it is actually an "enclosed volume" rather than an enclosed area or region. Vias 60 are indicated by dots along the dashed lines. One of the dashed lines surrounds the perimeter of the cover substrate 32. Three types of enclosed volumes are shown in the diagram. The largest is type I volume 90. There is one volume of this type that surrounds the volume occupied by the display element 12. Several smaller volumes are type II enclosed volumes 92, which surround the volumes touched by the user but without data input elements 14, 16, 18, 20 below. Several rectangular volumes are type III volumes 94. Each type III volume 94 has a data input element below it. These type III enclosed volumes 94 are considered to be areas with the highest risk of static charge.

[0042] Figure 4 The series of dashed lines in the image clearly depicts the layout. Figure 2 The pattern of the conductive silver paste layer 36 observed in the side cross-sectional view, and the pattern for covering the conductive silver paste layer with the colored ink layer 38.

[0043] In this invention, it is preferable to divide the surface area of ​​the covering substrate 32, especially the type III region 94, so that its surface area is less than 500 mm². 2 According to IEC 60079-0:2017, the maximum unprotected area of ​​insulating material is 500 mm². 2 The colored ink layer 38 covering the conductive silver paste layer 36 provides a watermark feature, which allows the user to visually detect when the conductive polymer coating 40 has been damaged or worn to the point where the cover needs to be replaced. By using conductive silver paste to frame the Type III area 94, the damaged area will not exceed the standard requirement of 500 mm². 2 The preferred colored ink 38 is the 9000 series PET ink, commercially available from Jujo Chemical Co., Ltd. in Japan. This ink is suitable for high-speed printing and exhibits excellent adhesion to PET.

[0044] Vias 60 are precisely sized and arranged on the cover substrate 32. Each via 60 is cut into the substrate 32, preferably by laser cutting, to provide a precisely positioned and sized channel between the top and bottom sides of the substrate for the transfer of static charge. When the via 60 is filled with conductive ink, it provides a grounding scheme, as described below, to discharge charge from the top side to an internal conductive collector surface on the bottom side of the substrate. Thus, a conductive sheet connects the internal conductive collector surface to the metal housing of the device. Wires connect the housing to ground, thereby preventing charge buildup on the outer surface of the plastic cover. The vias 60 are small and inconspicuous, therefore not impairing the appearance of the cover.

[0045] Figure 5 A bottom plan view of the bottom surface of the cover substrate 32 is shown. Note that, viewed from the bottom side, display area 12 is now located on the right side of the keyboard arrangement. This figure illustrates several points. One point concerns how the conductive silver paste layer 46 on the bottom side mirrors the pattern of the conductive silver paste 36 on the top side, and how the via 60 connects and interconnects these conductive layers. A second point concerns how the pattern of the silver paste layer 46 has at least one widened portion 96 for connecting the silver paste layer 46 to a grounding pad or wire. A second widened portion 97 is also shown.

[0046] Figure 6 This is an enlarged side cross-sectional view of the cover 30 focusing on a single via 60 formed in the non-conductive cover substrate 32. As described above, arranging the conductive ink 34 on the top side of the cover substrate 32 allows the conductive ink 34 to flow into the via, at least partially filling it. Since the colored ink layer 44 is applied to the bottom side of the cover substrate 32 before the via 60 is formed, it does not flow into the via, but when the conductive ink layer 46 is applied to the bottom side, it completely fills the via 60, thereby establishing electrical communication between the conductive paste layers 36 and 46. The shape and position of the interface between the conductive paste layers 36 and 46 can vary, and the interface shown is merely exemplary. The colored ink layer 38 covers the conductive paste layer 36 such that it is only visible if the colored ink layer is damaged or worn. The electrostatic dissipative conductive layer 40 is connected to the conductive paste layer 36 via the conductive ink 34. Charges appearing in any of regions 90, 92, and 94 can thus flow freely from the top side of the covering substrate 32 to the bottom side of the conductive paste layer 46. Consequently, these charges flow through their potential difference to the conductive paste layer 46. Figure 5 The grounding connection structure provided by the widened portion 96 shown.

[0047] Figure 7This is a top plan view of the back adhesive layer 48 of the cover assembly 30. Pressure-sensitive adhesive is distributed across the entire top surface of the back adhesive layer 48, except for cutouts 98, 100, and 102; the material is typically 3M product 9672LE. Cutout 98 corresponds to the display area, and cutouts 100 and 102 correspond to the widened portions 96 and 97.

[0048] List of reference numerals in the attached diagram:

[0049] 10 Keyboard Components

[0050] 12 display elements

[0051] 14. On / Off Button

[0052] 16-key numeric keypad

[0053] A set of 18 directional arrows

[0054] A collection of 20 function buttons

[0055] 30 Coverings

[0056] 32 Covering substrate

[0057] 34 Conductive Ink

[0058] 36 Conductive Silver Paste

[0059] 38 Color Inks

[0060] 40 Conductive polymer coating

[0061] 42 Insulating Optical Ink

[0062] 44 Colored Ink

[0063] 46 Conductive Silver Paste

[0064] 48 Adhesive layer

[0065] 60 via

[0066] 70 Keyboards

[0067] 72 Another adhesive layer

[0068] 74 Keyboard spacers

[0069] 76 Upper level

[0070] 78 Metal Dome

[0071] 80 mezzanine

[0072] 82 Circuit Layer

[0073] 84 Another adhesive layer

[0074] 86 Circuit spacer layer

[0075] 90 Type I closed volume

[0076] 92 Type II enclosed volume

[0077] 94 Type III enclosed volume

[0078] 96 Widened grounding connection structure

[0079] 97 Second widened grounding connection structure

Claims

1. A component for protecting a plastic keyboard having data input elements and at least one display element from electrostatic discharge, the component comprising: A cover substrate having a top side and a back side, the cover substrate also having a plurality of precisely positioned through-holes formed therethrough, the top side having a top surface coated with a conductive polymer layer, and the back side having a back surface printed with at least one colored ink layer, the at least one colored ink layer depicting a plurality of alphanumeric elements and graphic elements of a keyboard. as well as A conductive arrangement structure, disposed on a cover substrate, is used to collect static charge on the top side, transfer the static charge to the back side through the plurality of vias, and discharge the transferred static charge to ground. The conductive arrangement structure includes: At least one first conductive mesh is printed on the top surface of a cover substrate beneath a conductive polymer layer, the at least one first conductive mesh dividing the top surface into a plurality of enclosing regions, each enclosing region being equal to or smaller than a predetermined size, each first conductive mesh including a plurality of nodes, each node being located on top of and extending into a corresponding via among the precisely positioned plurality of vias; and At least one second conductive grid is printed on the back surface of the cover substrate beneath the at least one colored ink layer, such that the size and shape of each second conductive grid corresponds to one of the first conductive grids, and each second conductive grid includes a plurality of nodes, each node being located below and extending into a corresponding through-hole of the precisely positioned plurality of through-holes; and At least one metal sheet connects each second conductive grid to ground.

2. The component according to claim 1, wherein, Each of the first and second conductive grids includes a segment of conductive paste printed on the substrate of the cover.

3. The component according to claim 2, wherein, A layer of colored ink is applied on top of the conductive paste segment in each first conductive grid.

4. The component according to claim 3, wherein, Each node of the first conductive grid includes: A conductive polymer plug is applied from the top side of a cover substrate to each precisely positioned through-hole. The plug has a body portion extending into the through-hole and a flange portion, the diameter of which is larger than the diameter of the through-hole, and the flange portion extends on the top surface of the cover substrate. A section of conductive paste applied to the top of the plug; and Colored ink segments applied on top of conductive paste segments.

5. The component according to any one of claims 2 to 4, wherein, Each node of the second conductive grid includes a portion of conductive paste extending from the underside of the cover substrate into a via that enables it to make electrical contact with a corresponding node of the first conductive grid.

6. The component according to any one of claims 1 to 4, wherein, The coating matrix includes non-conductive polymers.

7. The component according to claim 6, wherein, The non-conductive polymer is polyethylene terephthalate sheet.

8. The component according to any one of claims 1 to 4, 7, wherein, The electrostatic dissipative coating is transparent.

9. The component according to claim 8, wherein, The electrostatic dissipative coating has a transparency of up to 90% Y at d=100nm.

10. The component of claim 8, wherein, The electrostatic dissipative coating is a composite of substituted polythiophene and anions, with an electrical conductivity in the range of 1000 Siemens per centimeter.

11. The component according to any one of claims 1 to 4, 7, 9, and 10, wherein, One of the multiple first conductive grids is a conductive grid with vias located around the periphery of the cover substrate.

12. The component according to any one of claims 1 to 4, 7, 9, and 10, wherein, The area corresponding to each data input element of the keyboard is surrounded by at least one of the first conductive grids.

13. An electronic device for data input and display, the electronic device comprising: shell; A keyboard suitable for data input and display, mounted on the housing; as well as The cover according to any one of claims 1 to 12, which is disposed on top of the keyboard and fixed in position by the housing, is suitable for dissipating static charge that occurs during keyboard use.

14. The electronic device according to claim 13, wherein: The outer casing is metal; and The static charge dissipated by the covering is discharged into the outer shell.

Images