Patent Application
20140055731
When cholesteric liquid crystal is combined with a polymer solution, in very specific ratios, and is placed between two sheets of polyethylene terephthalate (PET) a surface is created having a reflectivity modulated by pressure. When enough localized pressure is applied, an energy state of the liquid crystal is raised to a level such that a state of the liquid crystal changes and becomes reflective. For the abovementioned state change to occur in a localized manner, the PET sheets have a stiff smooth backing plate. Otherwise, pressure provided to the PET sheets spreads as a lower PET sheet deforms, thereby causing a stroke of a writing implement to appear much broader than it actually is.
Products currently being sold include an acrylonitrile butadiene styrene (ABS) backplate behind a bottom PET sheet and adhere a polyimide digitizer sheet beneath the backplate resulting in a stackup that is thick, unnecessarily complicated and expensive.
This Summary is provided to introduce a selection of concepts in a simplified form that is further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
In an embodiment consistent with the subject matter of this disclosure, a cholesteric liquid crystal display and digitizer assembly, which is thinner than a conventional cholesteric liquid crystal display and digitizer assembly, is provided. The liquid crystal display may include a conductive material laminated to a first insulating layer and forming a conductive trace. The first insulating layer may include FR-4 glass epoxy, ABS, or other insulating material. The conductive material may include, but not be limited to, copper. Components may be soldered to portions of the conductive trace to form a digitizer printed circuit board integrated with the first insulating layer, a liquid crystal display drive printed circuit board integrated with the first insulating layer, or both of the digitizer printed circuit board and the liquid crystal display drive printed circuit board integrated with the first insulating layer. A second insulating layer may be laminated over a surface of the soldered components, the conductive trace and the first insulating layer to form the second insulating layer with a smooth surface. A pressure-sensitive cholesteric liquid crystal display layer may be laminated onto the smooth surface of the second insulating layer. The first insulating layer forms a force backplate and is substantially thick, such that an application of pressure, with an implement, to an area of a surface of the pressure-sensitive cholesteric liquid crystal display layer and dragging of the implement across the surface changes a state of liquid crystal of the cholesteric pressure-sensitive liquid crystal display layer to a reflective state, thereby causing a line to appear across the surface of the pressure-sensitive cholesteric liquid crystal display layer. A thickness of the line is a representative of a size of a portion of the implement that comes into pressured contact with the pressure-sensitive cholesteric liquid crystal display layer.
In a second embodiment consistent with the subject matter of this disclosure, a method for making a cholesteric liquid crystal display is provided. A conductive material may be laminated to a first insulating layer. The conductive material may include, but not be limited to, copper. The first insulating layer may include, but not be limited to, FR-4 glass epoxy or ABS. The conductive material may be etched to form a conductive trace on the first insulating layer. Components may be soldered to portions of the conductive trace to form at least one of a digitizer printed circuit board or a liquid crystal display drive printed circuit board integrated with the first insulating layer. A second insulating layer may be laminated over the soldered components, the conductive trace and the first insulating layer to form a smooth surface of the second insulating layer. A pressure sensitive cholesteric liquid crystal display layer may be laminated over the smooth surface of the second insulating layer. The first insulating layer has a thickness, such that when pressure is applied with an implement to a surface of the pressure-sensitive cholesteric liquid crystal display layer and the implement is dragged across the surface, a state of liquid crystal of the pressure-sensitive cholesteric liquid crystal display layer changes to a reflective state, thereby causing a line to appear across the surface of the pressure-sensitive cholesteric liquid crystal display layer. The line has a thickness representative of a size of a portion of the implement that has come into pressured contact with the pressure-sensitive cholesteric liquid crystal display layer.
In order to describe the manner in which the above-recited and other advantages and features can be obtained, a more particular description is described below and will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings. Understand that these drawings depict only typical embodiments and are not therefore to be considered to be limiting of its scope. Implementations will be described and explained with additional specificity and detail through the use of the accompanying drawings.
Embodiments consistent with the subject matter of this disclosure provide a force localizer backplate for a cholesteric liquid crystal display (LCD) integrated with either a digitizer, an LCD drive, or both the digitizer and the LCD drive. In some embodiments, the digitizer may be made from FR-4, which is a grade designation assigned to glass-reinforced epoxy laminate sheets, tubes, rods and printed circuit boards (PCBs). FR-4 is a composite material composed of woven fiberglass cloth with a flame resistant epoxy resin binder. FR-4 is commonly used as an electrical insulator having considerable mechanical strength.
Various embodiments consistent with the subject matter of this disclosure may integrate a force backplate, an electromagnetic digitizer, and/or control and display drive electronics into a single part. The digitizer may be fabricated via a conventional printed circuit board fabrication process. A number of layers of different types of insulating material, including, but not limited to, FR-4 may be laminated together to form a stiff force backplate, which may be integrated with the digitizer or the control and display drive electronics, or both the digitizer and the control and display drive electronics.
In some embodiments, the layers of different types of insulating material may include different types of FR-4 resulting in a cheaper and thinner integrated force backplate as compared with a non-integrated force backplate, digitizer, and control and display drive electronics fabricated via a relatively expensive polyimide process.
Cholesteric LCD display area 102 may be mounted in a frame 104 having an open area through which cholesteric LCD display area 102 can be observed. Cholesteric liquid crystal display (LCD) area 102 may be electrically switched between one of two stable states; a reflective state or a transmissive state. In some embodiments, a button 106 may be placed on a portion of frame 104, such that when button 106 is activated or pressed, cholesteric LCD display area 102 is electronically switched to the transmissive state, thereby erasing lines drawn on cholesteric LCD display area 102.
In
Further,
LCD layer 202 may include reflective bistable polymer-dispersed cholesteric liquid crystal laminated between two conductive polymer coated polyethylene terephthalate (PET) substrates. At least a portion of LCD layer 202 is adhered to a stiff, smooth force backplate 204 made of injection molded acrylonitrile butadiene styrene (ABS). Polyimide digitizer sheet 206 is adhered to an underside of force backplate 204. Digitizer PCB 208 is adhered to polyimide digitizer sheet 206. At least a portion of LCD drive PCB 210 may be adhered to LCD layer 202.
In some embodiments, force backplate 302 may be made of FR-4 instead of more expensive ABS. A relatively thin layer of ultra-smooth FR-4 304 may be laminated on a top surface of force backplate 302 integrated with the digitizer PCB and/or the LCD drive PCB. Integrated circuits for driving cholesteric LCD display 300, driving to or sensing from a digitizer and communicating with a host, may reside on a same PCB resulting in a thinner, cheaper cholesteric LCD in comparison with a conventional cholesteric LCD.
Next, the conductive material laminated to the force backplate may be etched to form a conductive trace (act 404). The conductive material may be etched using any conventional etching process. Next, various components may be soldered to portions of the conductive trace on the force backplate (act 406) and may form electrical connections between the components and the conductive trace. This may be followed by laminating an ultra-smooth second insulating layer over the soldered components, the conductive trace, and the first insulating layer. In some embodiments, the second insulating layer may be made of FR-4 (act 408). A pressure-sensitive cholesteric LCD layer may then be laminated onto the ultra-smooth second insulating layer.
Embodiments consistent with the subject matter of this disclosure are related to a cholesteric liquid crystal display, which is thinner than conventional cholesteric liquid displays. In some embodiments, insulating layers of the cholesteric liquid crystal display may include FR-4 glass epoxy, which is less expensive than ABS used in conventional cholesteric liquid crystal displays.
Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms for implementing the claims. Further, in other embodiments, an order of acts performed may vary. For example, in other embodiments, an order of the acts included in the flowchart of
Accordingly, the appended claims and their legal equivalents define embodiments, rather than any specific examples given.
