Patent Application
20090033643
The present invention generally relates to displays, and more particularly relates to constructing highly integrated display modules which incorporate supplemental electronics into the display panel's design using polysilicon devices, or an alternate technology which enables complex electronic functions to be constructed as part of the display.
Flat panel displays such as liquid crystal displays and organic light emitting diode (AM-OLED) displays employ circuit cards with integrated circuits to provide display functionality, and to interface with the display's host hardware configuration. The circuit cards provide display operating voltages, video data and timing control signals, and display calibration voltages and currents which maximize display performance for the intended application.
Flat panel displays utilize a variety of electronic control circuits to drive an image, such as scan drivers, data drivers, backlight controllers, and the like. The scan and data drivers are highly integrated silicon devices which combine analog and digital functional blocks to drive the display panel. The LCD drivers are typically mounted on a flexible polyamide or polyester film which connects to the display substrate on one side and the system interface circuit cards on the other side. The system interface electronic circuits have traditionally been located on a separate circuit board which is located apart from the display substrate. Such a configuration may necessitate third party electronic components, supplemental circuit cards, and expensive system interconnects, which may add to the display's overall cost.
Accordingly, it is desirable to provide an apparatus and method for integrating display control electronics and display dimming control circuitry into the display's design. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
Various exemplary embodiments demonstrate how integrated electronics may be incorporated into the display design, such as on thin-film transistor (TFT) substrate.
In one embodiment, by way of example only, the present invention is a display device, including a substrate. A plurality of pixel circuits is at least partially disposed over or integrated into a first surface of the substrate and arranged in a display matrix. A control device is disposed over or integrated into a second surface of the substrate. The integrated electronic components are integrated into or disposed over the substrate so as to not interfere with a pixel aperture of the display. In the case of a liquid crystal display with a backlight, light passes from the backlight through the display substrate via the pixel aperture. In the case of a transflective liquid crystal display, the pixel aperture can pass light from the backlight, or it can reflect light from the incident light source. In these two cases, supplemental electronic components may be placed in the display periphery, or under the light blocking layer that occludes the row and column lines in the display substrate. In the case of a self-emissive display, such as an Organic Light Emitting Diode (OLED) display, light originates from the pixel aperture. Supplemental electronic components may be placed under the light blocking layer, or they may be placed on the display's back surface, where self-emitted light does not pass.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Various aspects of the exemplary embodiments may be described herein in terms of functional and/or logical block components and various processing steps. It should be appreciated that such block components may be realized by any number of hardware, software, and/or firmware components configured to perform the specified functions. For example, an embodiment of the invention may employ various integrated circuit components, e.g., radio-frequency (RF) devices, memory elements, digital signal processing elements, logic elements and/or the like, which may carry out a variety of functions under the control of one or more microprocessors or other control devices. In addition, the present invention may be practiced in conjunction with any number of data transmission protocols and that the system described herein is merely one exemplary application for the invention.
For the sake of brevity, conventional techniques related to signal processing, data transmission, signaling, network control, the IEEE 802.11 family of specifications, and other functional aspects of the system (and the individual operating components of the system) may not be described in detail herein. Furthermore, the connecting lines shown in the various figures contained herein are intended to represent example functional relationships and/or physical couplings between the various elements. It should be noted that many alternative or additional functional relationships or physical connections may be present in a practical embodiment.
The present invention substantially improves upon the prior art, and provides reduced display system complexity, reduces system changes that result from third party device obsolescence over the display product's life cycle, and reduces display system cost. The present invention integrates supplemental display system electronics into the display's design, thereby eliminating the need for specific third party electronic components, supplemental circuit cards, and expensive system interconnects.
Prior art flat panel display configurations exist in abundance. Prior art includes many commonly available liquid crystal displays which employ color filters arranged in three to four color dot groups to produce a single display picture element (pixel). Furthermore, said pixels are arranged in an XY grid to produce a display. The prior art employs backlights to project light through a liquid crystal display, or self-emissive media in the case of AM-OLED displays.
A rigid or flexible substrate is generally employed to support components of the display which are formed over, or fabricated over, the substrate. For example, a substrate is employed to support an active matrix switch array, also known in some embodiments as a thin-film-transistor (TFT) array. The substrate can be glass, plastic, stainless steel, or some other suitable material which is compatible with TFT array processing. For this discussion, a glass substrate will be assumed. However, this assumption does not limit the scope or applicability of the invention to glass, as the concepts presented herein apply equally well to other substrate materials, such as stainless steel and plastic.
The present invention integrates electronic control circuitry typically removed from the display onto or into the display itself, as will be further described. The circuitry can be located on a rear surface of the substrate, where it can be adhered to the substrate or disposed over the substrate using typical semiconductor processing technologies. In addition, the circuitry can be integrated into the display matrix, by placement alongside resident electronics (e.g., thin film transistors) already incorporated into the display. Such an implementation is strategically designed so as not to obstruct the pixel structures of the display. Finally, the circuitry can be integrated into the display along a peripheral edge of the display matrix, again placed so as not to obstruct the pixel. Such circuitry may be disposed over the substrate, or fabricated over the substrate, to suit a particular application.
Integration of such control circuitry as will be further described may be applied to a host of display technologies, includes liquid crystal displays (LCD) device, light emitting displays (LED) such as an organic light emitting diode (OLED) device, field emission displays (FED), and plasma display panel (PDP) devices. Additionally, the discussion has applications to several variations of the described technologies, such as so-called “super-twist” displays.
Turning to
The array of rows and columns is constructed on a light-blocking layer, also called a light shield, which possesses the shape of the row and column matrix. The light blocking layer is omitted from the pixel area 240, where light must be emitted, or where light must pass from the backlight to the display observer. The light blocking layer prevents light from impinging on the thin film transistors (TFTs) 230, which are photosensitive. Furthermore, where rows and columns intersect a TFT switch is placed. An insulating pad 250 is place at the points where gate lines cross over source lines, to prevent gate-to-source shorts. The gate, or enable signal of the TFT is connected to the proximate row bus 210, and the source, or programming terminal of the TFT is connected to the proximate column bus 220.
The TFT drain connection is tied to the pixel 240, which can be programmed to a fixed number of brightness states, depending on the programming current or voltage applied through the TFT. The display rows are connected to row driver electronic components, and the display columns are connected to column driver electronic components. For the purpose of this discussion, the terms gate driver and row driver may be synonymously applied, and likewise, column driver or source driver may also be synonymously applied. Source and gate drivers are generally constructed on a silicon substrate which is further attached to a flexible foil, which can then be attached to the display assembly on one side, and the electrical circuit card on the other side. The gate and source drivers provide highly integrated functionality in a very small mechanical footprint.
The TFT array for an active matrix OLED display is similar, though more complex, than the active matrix array for the LCD. LCDs only need 1 TFT per pixel. OLED displays typically have from 2 to 5 TFTs in the pixel. This stems from the fact that OLEDs must be programmed with a current that continuously flows when the display pixel is operating. An LCD uses a time varying voltage to change the liquid crystal material properties; no steady current flows in the LCD. The extra TFTs in an OLED are needed to stabilize the TFT's performance, and provide a programmed current to set the OLED display's brightness.
The following description is unique in its application to a variety of flat panel displays, in that normally unused areas of the display can house integrated electronics, thereby reducing or eliminating the need for supplemental electronic components to operate the display. Using these areas can reduce system complexity and cost, and eliminate some part obsolescence issues. Depending on the technology of any particular flat panel display, the back side of the TFT substrate, the TFT substrate's peripheral area, or the area under the light shield may be used for integrated electronics that would otherwise be placed on auxiliary circuit cards.
Bearing the previous discussion in mind,
Electrical connectivity to the front surface 320 of the display is maintained through interconnects 330. In one embodiment, the interconnect 330 can include structures such as flexible interconnect foil. The display 300 is coupled to a system controller 340 via an interconnect 350, although, in other embodiments, the controller 340 may also be integrated in or over the rear surface 310.
As one skilled in the art will appreciate, the various electronic control components and circuitry can vary according to the particular type of display. For example, the control components may include a scan driver for applying a gate voltage to select pixel circuits integrated in the display matrix. The control components may include a source driver for applying a data voltage to the pixel circuits. For non-self emissive displays, the control components may include a backlight controller for applying a backlight control signal. Finally, the control components may include a timing controller for applying a control signal. Similar electronics and associated circuitry may also be included.
As will be further described, such electronic control components and circuitry may be disposed over or integrated into the rear surface 310 of the substrate using traditional techniques known in the semiconductor industry, such as masking, etching, photolithography, material deposition such as chemical vapor deposition (CVD), and the like. In other embodiments, the circuitry and components may be formed and adhered to the substrate using an adhesive material, such as a die attach (DA) adhesive. In further embodiments, the control circuitry and components may be integrated into the front surface of the display matrix along with existing circuitry and components. Finally, the control circuitry may be integrated along peripheral edges of the front surface of the substrate. In both of the latter embodiments, placement of such electronics can occur so as not to obstruct the flow of light through the display aperture, or to impede light emitted from a self-emissive display.
In the depicted exemplary embodiment shown in
Moving to the back surface of the substrate 402, a series of electronic components 418 are seen disposed over the substrate using an adhesive 420. Again, alternatively, the components are formed over the substrate directly or integrated into the substrate using a series of the manufacturing steps mentioned previously. A portion of lead 422 is shown connecting the electronic components 418. Lead 422 may be part of a larger conductive device, such as a flexible foil interconnect, or may consist of lead wires which can be fixed to such structures as bond pads. Lead 422 can be a portion of the interconnect which provides electrical connectivity between the TFTs 404 and related electronics on the front surface of the display and the control components on the rear surface.
Electronic components 418 can include discrete components such as transistors, diodes, resistors, capacitors, and the like, and integrated circuits. As will be described further, the electronic components may be connected using a variety of means known in the art, such as wire bonding or through the use of conductive layers formed in or over the substrate itself.
Turning to
Components 434, 436, 438, and others are strategically placed under the light blocking portion so as not to obstruct the pixel portion 240. The components 434, 436 and 438 are positioned in combination with existing TFTs 404 and related circuitry and components. The components 434, 436, and 438 may be integrated with the existing circuitry as part of a single or multiple conductive layers, for example. Here again, components 434, 436, 438 and others may include discrete components such as resistors, diodes, capacitors, and the like, as well as integrated components such as integrated circuits or even dies.
Turning to
It should be appreciated that the example embodiments described herein are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing the described embodiment or embodiments. It should be understood that various changes can be made in the function and arrangement of elements without departing from the scope of the invention as set forth in the appended claims and the legal equivalents thereof.
