PATENT DOCUMENT

Publication Number: US-9409383-B2
Application Number: US-40863609-A
Country: US
Kind Code: B2

Title: Layer-specific energy distribution delamination

Abstract:
Delamination of a laminated multilayer stack is provided by generating a layer-specific energy distribution in the stack during delamination. A localized energy transferrer can generate localized heating, cooling heating, cooling, or other form of energy absorption or transmission, in a bonding layer of a multilayer stack. Localized energy transfer can include thermal energy transfer, such as heating and/or cooling, acoustic energy transfer, such as applying ultrasonic energy, electromagnetic energy transfer, such as applying laser light, directed microwaves, etc. Localized energy transfer can generate a layer-specific energy distribution that can weaken the bonding layer while reducing damage to other layers of the stack.

Claims:
What is claimed is: 
     
       1. A method of delaminating a multilayer laminated stack of overlapping layers, the method comprising:
 obtaining the multilayer laminated stack including a first layer having a first surface that extends substantially over the first layer, a second layer having a second surface that extends substantially over the second layer, and a bonding layer that bonds the first layer to the second layer, wherein the multilayer laminated stack is formed by laminating the first layer to the second layer using the bonding layer, wherein the first layer comprises a touch sensor layer and the second layer comprises a display layer; 
 applying energy to a first portion of the bonding layer such that a concentration of the energy is greater in the bonding layer than a concentration of energy in the first and second layers, the bonding layer extending substantially throughout the area of overlap of the first and second surfaces, wherein the energy weakens the bonding layer at the first portion, the first portion being disposed between respective portions of the first and second surfaces; 
 applying a heat sink to the multilayer laminated stack to remove thermal energy from one or more of the first layer or the second layer; and 
 breaking the weakened bonding layer at the first portion between the respective portions of the first and second surfaces. 
 
     
     
       2. The method of  claim 1 , wherein the first portion includes an exposed surface of the bonding layer, and applying the energy to the first portion includes applying a directed transmission of energy to the exposed surface of the bonding layer, while restricting the transmission of the energy to the first and second layers. 
     
     
       3. The method of  claim 2 , wherein applying the directed transmission of energy includes applying thermal energy to the exposed surface of the bonding layer. 
     
     
       4. The method of  claim 3 , wherein applying thermal energy includes applying a heated mechanical separation mechanism to the exposed surface. 
     
     
       5. The method of  claim 1 , wherein the first portion includes an exposed surface of the bonding layer, and applying energy to the first portion includes generating a directed transmission of energy from the exposed surface of the bonding layer, while restricting the transmission of the energy from the first and second layers. 
     
     
       6. The method of  claim 5 , wherein generating the directed transmission of energy includes removing thermal energy from the bonding layer through the exposed surface of the bonding layer. 
     
     
       7. The method of  claim 6 , wherein removing thermal energy includes applying a cooling mechanical separation mechanism to the exposed surface. 
     
     
       8. The method of  claim 2 , wherein applying the directed transmission of energy includes applying electromagnetic energy to the exposed surface of the bonding layer, while restricting exposure of the first and second layers to the electromagnetic energy. 
     
     
       9. The method of  claim 8 , wherein applying electromagnetic energy includes irradiating the exposed surface with one of (i) laser light, (ii) microwaves, and (iii) infrared radiation. 
     
     
       10. The method of  claim 1 , wherein the first portion includes an internal portion of the bonding layer, and applying the transmission of energy to the first portion includes focusing the energy transmission through the multilayer laminated stack, such that the energy transmission is less concentrated in each of the first and second layers than in the internal portion of the bonding layer. 
     
     
       11. The method of  claim 2 , wherein applying the directed transmission of energy includes transmitting the energy from a mechanical separator that breaks the weakened bond at the first portion of the bonding layer. 
     
     
       12. The method of  claim 10 , wherein focusing the energy transmission includes focusing a single beam of electromagnetic energy such that a focus of the beam is in the internal portion of the bonding layer. 
     
     
       13. The method of  claim 10 , wherein focusing the energy transmission includes aiming a plurality of beams of electromagnetic energy such that the beams converge in the internal portion of the bonding layer. 
     
     
       14. The method of  claim 1 , wherein the first layer comprises a cover glass layer. 
     
     
       15. The method of  claim 1 , wherein the second layer comprises a liquid crystal module (LCM) layer. 
     
     
       16. The method of  claim 1 , wherein the first layer comprises a cover glass layer and the second layer comprises a liquid crystal module (LCM) layer. 
     
     
       17. A method of removing a touch sensor layer from a laminated display stack of a portable mobile device, the method comprising:
 obtaining the laminated display stack including the touch sensor layer having a first surface that extends substantially over the touch sensor layer, a display layer having a second surface that extends substantially over the display layer, and a bonding layer that bonds the touch sensor layer to the display layer and extends substantially throughout the area of overlap of the first and second surfaces; 
 applying energy to a first portion of the bonding layer to weaken the bonding layer at the first portion; 
 applying a heat sink to the laminated display stack to remove thermal energy from one or more of the touch sensor layer or the display layer; and 
 breaking the weakened bonding layer at the first portion. 
 
     
     
       18. The method of  claim 17 , wherein the heat sink is attached to the display layer. 
     
     
       19. The method of  claim 17 , wherein
 applying energy to the first portion includes applying thermal energy to exceed a threshold temperature that weakens the bonding layer; and 
 applying the heat sink maintains a temperature of the display layer below the threshold temperature. 
 
     
     
       20. The method of  claim 17 , wherein
 applying energy to the bonding layer includes: 
 varying an intensity of the energy applied to the first portion over time. 
 
     
     
       21. The method of  claim 17 , wherein:
 the applying energy to the first portion includes applying thermal energy to the bonding layer; and 
 applying the heat sink maintains the temperature of the display layer below a temperature that will damage the display layer. 
 
     
     
       22. A method of delaminating a laminated display stack, the method comprising:
 obtaining the laminated display stack including a touch sensor layer having a first surface that extends substantially over the touch sensor layer, a display layer having a second surface that extends substantially over the display layer, and a bonding layer that bonds the touch sensor layer to the display layer and extends substantially throughout the area of overlap of the first and second surfaces; 
 periodically applying energy to a first portion of the bonding layer to weaken the bonding layer by switching between an on and off cycle, wherein applying the energy results in the display layer remaining below a temperature that will damage the display layer; and 
 breaking the weakened bonding layer at the first portion. 
 
     
     
       23. The method of  claim 22 , further comprising:
 coupling a heat sink to the laminated display stack to remove thermal energy from one or more of: the display layer or the touch sensor layer. 
 
     
     
       24. The method of  claim 22 , further wherein the energy is periodically applied using a heated cutting wire. 
     
     
       25. The method of  claim 24 , wherein breaking the bonding layer is performed using the heated cutting wire. 
     
     
       26. The method of  claim 22 , wherein:
 periodically applying energy to the bonding layer raises a temperature of the bonding layer above a threshold temperature that weakens the bonding layer. 
 
     
     
       27. A method of delaminating a laminated display stack, the method comprising:
 obtaining the laminated display stack including the touch sensor layer having a first surface that extends substantially over the touch sensor layer, a display layer having a second surface that extends substantially over the display layer, and a bonding layer that bonds the touch sensor layer to the display layer and extends substantially throughout the area of overlap of the first and second surfaces; 
 applying energy to a first portion of the bonding layer to weaken the bonding layer by focusing an energy transmission through the laminated display stack such that the energy transmission is less concentrated in each of the touch sensor and display layers than in the bonding layer; and
 breaking the weakened bonding layer at the first portion. 
 
 
     
     
       28. The method of  claim 27 , wherein focusing the energy transmission includes focusing a single beam of electromagnetic energy such that a focus of the beam is within the bonding layer. 
     
     
       29. The method of  claim 27 , wherein focusing the energy transmission includes aiming a plurality of beams of electromagnetic energy such that the beams converge in the bonding layer.

Description:
This application claims the benefit of U.S. Provisional Application No. 61/140,072, filed Dec. 22, 2008, the contents of which are incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     This relates generally to delaminating a laminated multilayer stack, and in particular, to weakening a bonding layer of a laminated multilayer stack by generating a layer-specific energy distribution in the stack during delamination. 
     BACKGROUND OF THE INVENTION 
     Multilayer laminates have found use in a wide variety of applications, from exploratory space vehicles to consumer products. Many of these applications rely on the exceptional strength and structural integrity that multilayer laminates can provide. 
     Because of the strength and structural integrity of multilayer laminates, conventional delamination processes typically result in the destruction or degradation of one or more layers of a laminate. One conventional delamination process, for example, is directed to multilayer laminates in which layers are bonded together with an adhesive layer. In this delamination process, the multilayer laminate structure is heated in an oven until the adhesive layer softens. Once the adhesive has been sufficiently heated, the adhesive becomes soft enough for the surrounding layers to be separated by mechanical means. 
     In some applications, the temperature increase during the delamination process does not significantly degrade the layers surrounding the adhesive. However, in other applications the temperature increase may cause enough damage to the surrounding layers to render the layers partially or completely unusable. Delamination by heating a multilayer laminate stack used in a typical LCD touch screen application, for example, is likely to destroy the touch screen&#39;s LCD functionality, although the resulting delaminated layers might still be usable in some types of failure analysis. 
     SUMMARY OF THE INVENTION 
     This relates to delaminating a laminated multilayer stack, and in particular, to weakening a bonding layer of a laminated multilayer stack by generating a layer-specific energy distribution in the stack during delamination. A layer-specific energy distribution can result from localized heating, cooling, or other form of energy absorption or transmission, in a bonding layer of a multilayer stack. A localized heating, for example, of a bonding layer can result in an increase of the temperature of the bonding layer to exceed a threshold temperature at which the bonding layer is weakened. Weakening the bonding layer can allow a faster and more efficient delamination process to separate layers held together by the bonding layer. Limiting the temperature increase, in this example, to the bonding layer can reduce or eliminate damage to other layers of the stack. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an example touch screen  100  that may be processed according to embodiments of the invention. 
         FIGS. 2A and 2B  illustrate an example delamination apparatus and process according to embodiments of the invention. 
         FIGS. 3A and 3B  show another example delamination apparatus and process according to embodiments of the invention. 
         FIG. 4  illustrates another example delamination apparatus and process according to embodiments of the invention. 
         FIG. 5  shows another example embodiment using a pulley bandsaw to generate a layer-specific energy distribution in a multilayer laminate. 
         FIG. 6  illustrates another example delamination apparatus and process according to embodiments of the invention. 
         FIG. 7  illustrates another example delamination apparatus and process according to embodiments of the invention. 
         FIG. 8  illustrates another example delamination apparatus and process according to embodiments of the invention. 
         FIG. 9  is a graph showing an example simulation of the temperature of the cutting surface of a pressure sensitive adhesive (PSA) that is cooled with a pulsed coolant flow. 
         FIG. 10  illustrates another example delamination apparatus and process according to embodiments of the invention. 
         FIG. 11  illustrates an example embedded layer conductive layer in an adhesive stack that can be used in a delamination process according to embodiments of the invention. 
         FIG. 12  illustrates an example multilayer laminated stack with extended adhesive tabs according to embodiments of the invention. 
         FIG. 13  illustrates another example delamination process according to embodiments of the invention. 
         FIGS. 14A, 14B, and 14C  illustrate an example mobile telephone, an example digital media player, and an example personal computer that can include a multilayer laminated stack designed to be delaminated according to embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific example embodiments in which the invention can be practiced. It is to be understood that other embodiments can be used and structural changes can be made without departing from the scope of the invention. 
     This relates to delaminating a laminated multilayer stack, and in particular, to weakening a bonding layer of a laminated multilayer stack by generating a layer-specific energy distribution in the stack during delamination. A layer-specific energy distribution can result from localized heating, cooling, or other form of energy absorption or transmission, in a bonding layer of a multilayer stack. A localized heating, for example, of a bonding layer can result in an increase of the temperature of the bonding layer to exceed a threshold temperature at which the bonding layer is weakened. Weakening the bonding layer can allow a faster and more efficient delamination process to separate layers held together by the bonding layer. Limiting the temperature increase, in this example, to the bonding layer can reduce or eliminate damage to other layers of the stack. 
     Although embodiments of the invention may be described and illustrated herein in terms of laminated multilayer stacks for capacitive touch screens, it should be understood that embodiments of this invention are not so limited, but are applicable to other laminated stacks in which a suitable energy distribution can be generated to weaken a bonding layer. 
       FIG. 1  illustrates an example touch screen  100  that may be processed according to embodiments of the invention.  FIG. 1  includes an enlarged view of a portion of touch screen  100  showing details of a laminated multilayer stack  103  of the touch screen. Stack  103  includes a liquid crystal module (LCM) layer  105 , a pressure sensitive adhesive layer (PSA)  107 , a touch sensor (TS) layer  109 , a PSA layer  111 , and a cover glass (CG) layer  113 . Although laminated multilayer stack  103  is shown as a 5-layer stack, one skilled in the art will understand that embodiments of the invention would apply to stacks having more or fewer layers. 
       FIGS. 2A and 2B  illustrate an example delamination apparatus and process according to embodiments of the invention.  FIG. 2A  shows a side view of multilayer stack  103 . In the delamination process, a cutting wire  201  is heated and pressed into an exposed surface of PSA layer  107 . The thermal energy of cutting wire  201  heats the portion of PSA layer  107  near the contact area and softens the PSA material, making it easier for the cutting wire to cut through the PSA layer. The arrowed line in  FIG. 2  shows the cutting direction that cutting wire  201  is drawn through PSA layer  107  as it concurrently softens and cuts the PSA material. Thus, the heated cutting wire  201  is a localized energy transferrer, and in particular, a localized thermal energy transferrer because the application of thermal energy is localized to a portion of PSA layer  107 . In this way, for example, temperature increases of the other layers of stack  103  (such as LCM layer  105 , TS layer  109 , etc.) may be restricted. The application of heated cutting wire  201  generates a layer-specific distribution of thermal energy among the layers of multilayer stack  103 . The particular distribution of thermal energy generated in stack  103  can be modified by adjusting design parameters such as the dimensions and material properties (e.g., thermal conductivities) of the layers, the temperature and shape of the mechanical cutting element (e.g., wire, straight-edge blade, triangular blade), the speed of the cutting movement, the ambient temperature, etc. 
     Additional heating/cooling can be provided to further shape the energy distribution. For example, heat sinks or other cooling mechanisms could be attached to the outer surfaces of the multilayer stack to help draw heat from the outer layers of the stack more quickly, creating a steeper gradient of thermal energy between the inner and outer layers. The temperature of the cutting element can be varied as a function of time to further affect the energy distribution. For example, the heating source of the cutting element can be switched on and off periodically, allowing built-up heat in the layers to dissipate in between the “on” cycles. 
     The design parameters can be adjusted so that the distribution of thermal energy generated in the layers of the multilayer laminate stack cause the temperature of a bonding layer to exceed a threshold temperature at which the bonding layer weakens, while maintaining the other layers below temperatures at which damage would occur. 
       FIG. 2B  shows a perspective view of the example embodiment, including touch screen  100 , heated cutting wire  201 , and a controller  203 . Controller  203  controls the temperature of wire  201  and the cutting motion of cutting wire  201  (shown by the arrowed lines). Controller  203  includes a heating mechanism to heat cutting wire  201 . In this example, the heating mechanism is an electrical current source  205  that supplies an electrical current to cutting wire  201 . The electrical current is controlled to heat cutting wire  201  to the desired temperature for the particular delamination process. Other heating mechanisms could be used, for example, a heater that supplies thermal energy to cutting wire  201 . Controller  203  also includes a motor  206  that operates to move cutting wire  201  in a cutting motion (as shown by the arrowed lines) through PSA layer  107 . 
     Controller  203  can control motor  206  to provide a cutting motion that works efficiently in conjunction with the heating provided by current source  205 . For example, at the start of the delamination process, motor  206  positions cutting wire  201  at a starting surface of PSA layer  107 , and current source  205  begins supplying an electrical current to the cutting wire. After allowing a predetermined time period for the current to heat cutting wire  201 , and the heated cutting wire to heat PSA layer  107  to above the threshold temperature, motor  206  begins the cutting motion through PSA layer. The rate of motion is controlled to be slow enough to allow sufficient heating of the PSA material near cutting wire so that the PSA material is softened prior to being cut by the wire, and the motion of the wire is fast enough to reduce or minimize temperature increases in the surrounding layers. The motion may be, for example, continuous, stepped, at a constant rate, at a variable rate, etc. In some embodiments, controller  203  can take into account various system parameters, such as the material properties of the PSA layer, the characteristics of the heated cutting wire, e.g., the wire&#39;s thermal properties, size and shape of the wire, the operating temperature of the wire, etc. In this way, controller  203  may control the cutting motion to provide more efficient cutting. In some embodiments, cutting wire  201  may be moved through PSA layer  107  using other mechanisms. For example, touch screen  100  may be fixed to a movable chuck, and cutting wire  201  may remain stationary while the movable chuck moves the touch screen such that PSA layer  107  is heated and cut by the cutting wire. 
     One potential advantage of generating localized heating of PSA layer  107  is highlighted by the PSA layer&#39;s proximity to LCM layer  105 , as shown in  FIG. 2A . Specifically, the liquid crystal contained in liquid crystal modules such as LCM layer  105  typically begins to degrade at a temperature of approximately 100° C. However, a temperature greater than 100° C. is required to soften many PSA materials. In this example, the delamination process of the present embodiment can potentially allow a much greater variety of PSA materials to be used for PSA layer  105  while still allowing heating to be used in a nondestructive delamination process of touch screen  100 . 
       FIGS. 3A and 3B  show another example delamination apparatus and process according to embodiments of the invention. The example embodiment shown in these figures is similar to the embodiment shown in  FIGS. 2A and 2B , with the exception that cooling (instead of heating) is applied to the PSA material in order to weaken the material during delamination. In this regard,  FIGS. 3A and 3B  include a PSA layer  307  that weakens below a threshold temperature. A controller  303  includes a coolant, in this case a liquid nitrogen supply  305 , which provides a cooling mechanism to cool cutting wire  201  to a temperature below the threshold temperature of the PSA material. More specifically, liquid nitrogen supply  305  supplies two flows of liquid nitrogen to portions of cutting wire  201  close to the wire&#39;s cutting surface. Other cooling mechanisms could be used, for example, a condenser-type refrigeration unit. Like embodiments in which cutting wire  201  is heated, the cooled cutting wire  201  is a localized energy transferrer because the application of thermal energy, in this case transferring thermal energy out of PSA layer  107 , is localized to a portion of the PSA layer. 
     Controller  303  includes a motor  306  to move cutting wire  201  and a cutting motion through PSA layer  307 , similar to motor  206  described above. The exact cutting motion provided by motor  306  may be different than the cutting motion of motor  206  due to, for example, the differences in the material properties of the PSA layers, the different effects of heating and cooling, etc. 
       FIG. 4  illustrates another example delamination apparatus and process according to embodiments of the invention.  FIG. 4  shows a localized energy transferrer that is a pulley bandsaw  401 , including pulleys  403  and  405 , and a cutting wire  407 . A motor (not shown) turns pulleys  403  and  405  to draw cutting wire  407  across a cutting surface of a PSA layer  409  during the delamination process to separate an upper layer  411  and a lower layer  413 . As pulleys  403  and  405  are turned, the pulleys are moved in a cutting motion toward PSA layer  409 , such that cutting wire  407  cuts through the PSA layer. During the delamination process, cutting wire  407  is cooled below a threshold temperature at which PSA layer  409  is weakened. The cooling mechanism can include, for example, a nozzle  415  applies a coolant  417  to cool pulley  403 , which in turn cools cutting wire  407 . The cooling mechanism could also include additional nozzles to apply coolant to pulley  405  and/or to cutting wire  407 . Other cooling mechanisms could be used, for example, a condenser-type refrigeration unit. 
     In other embodiments, cutting wire  407  can be heated, for example, by heating one or more of pulleys  403  and  405 . As in the example embodiments of  FIGS. 2A-B  and  3 A-B, the choice of heating or cooling cutting wire  407  can depend on the PSA material to be cut during the delamination process. Similarly, the type of cutting motion can vary depending on factors such as the type of mechanical separating mechanism used (e.g., wire, blade, etc.), the material properties of the layers, etc. 
       FIG. 5  shows another example embodiment using a pulley bandsaw to generate a layer-specific energy distribution in a multilayer laminate. In this embodiment, energy distribution is localized in a bonding layer in part because the bonding layer selectively absorbs the particular energy transmitted by the cutting wire of the pulley bandsaw. Different types of energy may be transmitted by the cutting wire, for example, acoustic energy (e.g., ultrasound, mechanical vibrations, etc.) and electromagnetic (EM) energy (e.g., radio waves, microwaves, etc.).  FIG. 5  shows a pulley bandsaw  501  including pulleys  503  and  505 , and a cutting wire  507 . As in the previous embodiment, pulleys  501  and  503  rotate to draw cutting wire  507  across a cutting surface of a bonding layer of a multilayer stack during the delamination process. In one example embodiment, each of pulleys  503  of  505  also comprises an ultrasonic transducer (not shown). In other embodiments, only one of the pulleys may comprise an ultrasonic transducer. The ultrasonic transducers transmit ultrasonic energy to cutting wire  507  as the cutting wire is driven by the spinning pulleys during the delamination process. Bandsaw pulley  501  is moved toward multilayer stack  500  and cutting wire  507  is brought into contact with a PSA layer  509  of a multilayer laminated stack  500 . In addition to the mechanical cutting of spinning cutting wire  507 , the cutting wire also transfers the ultrasonic energy from the ultrasonic transducers to PSA layer  509 . In this way, pulley bandsaw  501  can be a localized acoustic energy transferrer because the application of ultrasonic energy may be localized in PSA layer  509 , so that the PSA layer may be weakened while reducing or minimizing damage to other layers in stack  500 , such as an upper layer  511  and a lower layer  513 . In other words, the delamination process generates a layer-specific distribution of ultrasonic energy among the layers of stack  500 , such that the bonding layer can be weakened due to the higher concentration of energy in the bonding layer. 
     In other embodiments, the cutting wire can be used as a localized EM energy transferrer by transmitting EM energy, such as radio waves, microwaves, etc., into the bonding layer. Referring again to  FIG. 5 , pulleys  503  and  505  can comprise EM transmitters (not shown), that use cutting wire  507  as an antennae to transmit EM energy into PSA layer  509 . 
     In some embodiments, the material used for the bonding layer can be specifically chosen or formulated to enhance the effect of the type of energy imparted to the bonding layer during delamination. A specially formulated PSA material, for example, that chemically degrades or releases under the influence of the particular type of energy might be used. 
       FIG. 6  illustrates another example delamination apparatus and process according to embodiments of the invention.  FIG. 6  shows a multilayer laminated stack  600  including a lower layer  601 , a PSA layer  603 , and an upper layer  605 . A laser  607  is a localized EM energy transferrer that supplies a localized application of energy to generate a layer-specific energy distribution among the layers of stack  600 . Laser  607  has a wavelength that is at least partially absorbed by PSA layer  603 . The light from laser  607  is directed to an exposed surface of PSA layer  603  to heat the PSA layer locally at the exposed surface during a delamination process. Laser  607  can be controlled by a controller (not shown) to apply the laser light in a variety of ways, for example, irradiating a single point on the surface of PSA layer  603  (point scanning), scanning the laser along a line on the surface (line scanning), scanning the laser along an arc around the PSA layer, etc., to locally heat the PSA layer. 
     In the example embodiment shown in  FIG. 6 , PSA layer  603  is removed through ablation and/or evaporation caused by the laser light itself. In other words, the laser light serves both as an energy delivery mechanism and as a mechanical separator. In other embodiments, the laser light can be used in conjunction with a mechanical separator, such as a wire, blade, etc. (not shown), for the delamination process. In these embodiments, the laser light serves a heat source only, while the mechanical separator operates to separate layers (delaminate) by cutting, breaking, removing, etc., a bonding layer between the two layers to be separated. 
       FIG. 7  illustrates another example delamination apparatus and process according to embodiments of the invention. In particular,  FIG. 7  shows a modification of the example embodiment of  FIG. 6 , in which obstacles blocking access to a bonding layer may be circumvented by scanning the laser (not shown) around the obstacles and/or using multiple lasers to avoid the obstacles.  FIG. 7  shows a side view of an example multilayer laminated stack  700  that includes a CG layer  701 , a PSA layer  703 , a TS layer  705 , a PSA layer  707 , and an LCM layer  709 . Stack  700  also includes mounting tabs  711  that obstruct a cutting surface of PSA layer  707 . In order to help circumvent mounting tabs  711  and to heat PSA layer  707  sufficiently,  FIG. 7  shows two laser beams  713  and  715  striking the cutting surface of the PSA layer at angles near an obstacle  711 . In some embodiments, a single laser can be used to form laser beams  713  and  715 . In this case, laser beams  713  and  715  in  FIG. 7  represent two laser beams applied at different times from the single laser. For example, the single laser (not shown) could apply laser beam  713  at a first time, the laser could be moved to a different vantage point, and could apply laser beam  715  from the different vantage point (at a time later than the first time). In another example embodiment, the single laser could apply laser beam  713  through a first beam path of an optical system (not shown) at a first time, the optical system could be adjusted for a second beam path, and the laser could apply laser beam  715  through the second path (at a time later than the first time). 
     In other embodiments, two or more lasers may be used to apply laser beams  713  and  715 . Using multiple lasers may provide some benefits. For example, it might be possible to eliminate the requirement for an optics system and/or a system to move the laser, or to reduce the complexity and cost of such systems. Another potential benefit is that multiple laser beams could be applied simultaneously, which could allow PSA layer  707  to be heated and ablated, cut, etc., in less time. Reducing the time required to heat PSA layer  707  might also help to reduce the total heat transferred to other layers, which could further help prevent damage to the other layers. 
       FIG. 8  illustrates another example delamination apparatus and process according to embodiments of the invention, in which a coolant delivery mechanism sprays a liquid coolant onto a cutting surface of a bonding layer in advance of a mechanical separator that cuts, breaks, etc., the cooled portion of the bonding layer.  FIG. 8  shows a multilayer laminated stack  800  including a lower layer  801 , a PSA layer  803 , and an upper layer  805 . A nozzle  807  pulses liquid nitrogen  809  onto a cutting surface of PSA layer  803 . When the cutting surface is sufficiently cooled by the pulses of liquid nitrogen  809 , a cutting wire (not shown) is advanced through the cooled portion of PSA layer  803 . Thus, the system including the cutting wire and nozzle  807  can be a localized energy transferrer. 
     In the example embodiment of  FIG. 8 , nozzle  807  pulses liquid nitrogen  809 , that is, the nozzle ejects a flow of liquid nitrogen for a (usually brief) period of time, stops the flow for a period of time, and repeats the cycle. Pulsing the flow of liquid nitrogen can allow the temperature of the layers of stack  800  to increase during the periods when no liquid nitrogen is being sprayed. This may help generate a layer-specific energy distribution that can reduce the temperature of PSA layer  803  below the threshold temperature to weaken the layer, while preventing the temperatures of layers  801  and  805  from dropping below damaging levels. 
       FIG. 9  is a graph showing an example simulation of the temperature of the cutting surface of a PSA that is cooled with a pulsed coolant flow. The y-axis of  FIG. 9  shows the temperature (in arbitrary units) of the cutting surface, and the x-axis shows the time (in arbitrary units). The first pulse of coolant is applied during time  0  to  100 , no coolant is applied during time  101  to  200 , and the cycle is repeated. The threshold temperature of the PSA, below which the PSA begins to weaken, is 0.5. As shown in  FIG. 9 , the surface temperature of the PSA falls below the threshold temperature of 0.5 only a portion of the time at the end of the cooling pulses and the beginning of the no coolant periods. 
       FIG. 9  also shows a horizontal line at a temperature of approximately 0.69, which is the average temperature of the localized cooling graph shown in  FIG. 9 . Because of the distance between the other layers and the localized cooling shown in  FIG. 9 , the temperatures of the other layers will tend to be close to the average temperature of 0.69 with little fluctuation. Thus, the temperature of the PSA layer in this example can be decreased below the PSA&#39;s threshold temperature (for a period of time, as discussed above) while the other layers can be maintained at a significantly higher temperature. In other words, the example delamination process can generate a layer-specific energy distribution that results in a weakening of the bonding layer while reducing damage to other layers. 
     During the time periods that the temperature of the cutting surface of the PSA is below the threshold, the PSA is weakened, and the system advances the cutting wire through the weakened PSA. When the temperature of the PSA increases above the threshold temperature, the cutting wire is stopped. Thus, pulsing the application of coolant can provide a way to limit temperature decreases in other layers, while still weakening the bonding layer, albeit for a limited period of time. Incremental cutting, breaking, removing, etc. can be used to take advantage of the limited durations that the bonding layer is in a weakened state. 
     Pulsed application of energy can potential yield another benefit. Specifically, forcing the temperature of the bonding layer to increase and decrease rapidly with the pulsed application of coolant may cause additional strain and/or stress in the bonding layer, which may further weaken the layer. 
       FIG. 10  illustrates another example delamination apparatus and process according to embodiments of the invention, in which energy absorption in a bonding layer is increased by increasing an energy density of the applied energy.  FIG. 10  shows a multilayer laminate stack  1000  including a lower layer  1001 , a PSA layer  1003 , and an upper layer  1005 .  FIG. 10  also shows two approaches using a localized energy transferrer to increase energy density in PSA layer  1003 . In a first approach, a beam of light  1007  having a wavelength absorbed by PSA layer  1003  is focused by a lens  1011  before being transmitted through the multiple layers of stack  1000 . As a result, the portions of light beam  1007  travelling through lower layer  100  and upper layer  1005  are relatively diffuse. Thus, temperature increases in the lower and upper layers can be reduced. On the other hand, the portion of light beam  1007  traveling through PSA layer  1003  is tightly focused, resulting in a greater increase in temperature of the PSA layer. 
     A second approach shown in  FIG. 10  includes three laser beams  1009  (generated by lasers  1013 ). Laser beams  1009  are aimed by an aiming mechanism (not shown) such that the laser beams penetrate upper layer  1005  and converge in PSA layer  1003 . The convergence of laser beams  1009  in PSA layer  1003  increases the energy density in the PSA layer compared to the separate laser beams transmitted though the lower layer  1001  and upper layer  1005 . 
       FIG. 11  illustrates an example embedded layer conductive layer in an adhesive stack that can be used in a delamination process according to embodiments of the invention. An embedded-conductor stack  1100  includes an upper adhesive layer  1101  and a lower adhesive layer  1103 . A localized energy transferrer can be a conductive layer  1105  including conductive traces is embedded between upper layer  1101  and lower layer  1105 . Two conductive pads  1109  remain exposed after conductive layer  1105  is embedded. Embedded-conductor stack  1100  can be formed as a bonding layer in a multilayer laminate stack, where the embedded-conductor stack can then be used for generating a layer-specific energy distribution in delamination processes according to embodiments of the invention, some examples of which will now be described. 
     In one example embodiment, conductive layer  1105  is formed of an electrically conductive material, and one or both of adhesive layers  1103  and  1107  are formed of an adhesive material that weakens above a threshold temperature. If conductive layer  1105  is formed of a transparent conductor, such as indium tin oxide (ITO), embedded-conductor stack  1100  could be formed in the place of one or both of PSA layers  107  and  111  of the laminated stack of touch screen  100 , for example. During a delamination process of such a laminated stack, an electrical current is applied to conductive pads  1109 . The electrical current causes the conductive traces of conductive layer  1105  to heat up. The current can be controlled to provide localized heating of the adhesive material of embedded-conductor stack  1100  to above the threshold temperature, while limiting the temperature increase of other layers of the laminated stack. A mechanical separation mechanism, such as a cutting wire, blade, etc. can be used to separate the layers by, for example, cutting, breaking, pulling apart, etc., the weakened adhesive. 
     In another example embodiment, conductive layer  1105  is formed of a thermally conductive material. Like the foregoing example embodiment, a stack  1100  embedded with a thermally conductive layer  1105  may be formed in place of a PSA layer or other adhesive layer in many multilayer laminated stack applications. During a delamination process, conductive pads  1109  can be connected to a heating mechanism, and the conductive traces of conductive layer  1105  can be heated to provide localized heating of the adhesive material of embedded-conductor stack  1100 , while limiting the temperature increase of other layers of the laminated stack. In this case, one or both of adhesive layers  1103  and  1107  is formed of an adhesive material that weakens above a threshold temperature. A mechanical separation mechanism, such as a cutting wire, blade, etc. can be used to separate the layers by, for example, cutting, breaking, pulling apart, etc., the weakened adhesive. 
     In another example embodiment, an embedded-conductor stack  1100  is formed with a thermally conductive layer  1105  as in the foregoing example embodiment. However, in the present embodiment, one or both of adhesive layers  1103  and  1107  is formed of an adhesive that weakens below a threshold temperature. During a delamination process of a multilayer laminated stack including an embedded-conductor stack  1100  of the present embodiment, a cooling mechanism can be applied to conductive pads  1109 , and the conductive traces can be cooled to provide localized cooling of the adhesive material of stack  1100 , while limiting the temperature increase of other layers of the laminated stack. As in the foregoing embodiments, a mechanical separation mechanism can be used to separate layers at the weakened adhesive. 
       FIG. 12  illustrates an example multilayer laminated stack with extended adhesive tabs according to embodiments of the invention.  FIG. 12  shows a multilayer laminated stack  1200  including a lower layer  1201 , an adhesive layer  1203 , and an upper layer  1205 . Adhesive layer  1203  is formed of an adhesive material, and portions of the adhesive material extend beyond the ends of lower layer  1201  and upper layer  1205  to form extended tabs  1207  of adhesive material. During a delamination process of stack  1200 , extended tabs  1207  can provide additional surface area of adhesive layer  1203  for the application of heating or cooling of the adhesive layer, which can increase the efficiency of the heating or cooling process. 
       FIG. 13  illustrates another example delamination process according to embodiments of the invention, in which an energy distribution is generated in layers of a multilayer laminated stack through selective absorption of an applied energy.  FIG. 13  shows a touch screen  1300  including a multilayer laminated stack  1301  (as shown in the enlarged detail in  FIG. 13 ). Multilayer stack  1301  includes a lower layer  1303 , an adhesive layer  1305 , and an upper layer  1307 . During a delamination process of stack  1301 , the stack is exposed to a directed energy  1309  from a localized energy transferrer. Directed energy can be, for example, EM radiation (e.g., laser light, microwaves, infrared), acoustic (e.g., ultrasonic), or other forms of energy delivered by corresponding localized energy transferrers, such as a laser, a directed microwave transmitter, an ultrasonic transducer, etc., that transmit energy absorbed primarily by a bonding layer that is desired to be weakened. For example, upper layer  1307  is designed to transmit substantially all of directed energy  1309 , and adhesive layer  1305  is designed to absorb substantially all of the directed energy. The transmittance and absorbance of the layers can be highly dependent on the wavelength of the directed energy, and the design of the layers may exploit the wavelength dependence in choosing suitable combinations of layers and directed energy. The absorbed directed energy is converted to thermal energy in adhesive layer  1305 . The directed energy absorbed in adhesive layer  1305  is converted to heat, resulting in a localized heating of the adhesive layer, while limiting the temperature increase of other layers in stack  1301 . 
     In other embodiments, adhesive layer  1305  may be formulated to degrade or release under the influence of directed energy  1309 . 
       FIG. 14A  illustrates example mobile telephone  1436  that can include touch sensor panel  1424  and display device  1430 , the touch sensor panel including a multilayer laminated stack designed to be delaminated according to embodiments of the invention. 
       FIG. 14B  illustrates example digital media player  1440  that can include touch sensor panel  1424  and display device  1430 , the touch sensor panel including a multilayer laminated stack designed to be delaminated according to embodiments of the invention. 
       FIG. 14C  illustrates example personal computer  1444  that can include touch sensor panel (trackpad)  1424  and display  1430 , the touch sensor panel and/or display of the personal computer (in embodiments where the display is part of a touch screen) including a multilayer laminated stack designed to be delaminated according to embodiments of the invention. The mobile telephone, media player and personal computer of  FIGS. 14A, 14B and 14C  can allow a non-destructive delamination process to be performed according to embodiments of the invention. 
     One skilled in the art would recognize, after reading the present disclosure, that many of aspects of the invention described in individual example embodiments may be applied in the other example embodiments. For example, pulsed application of energy, which is described above in relation to the example embodiment of  FIGS. 8 and 9 , may be applied in other embodiments of the invention. For example, energy sources such as lasers, current sources, thermal energy sources, etc., which can be used in various embodiments of the invention, can be applied in a periodic manner, such as by pulsing the output. 
     Although embodiments of this invention have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of embodiments of this invention as defined by the appended claims.

Metadata:
Filing Date: 20090320
Publication Date: 20160809
Grant Date: 20160809
Priority Date: 20081222
Inventors: FEINSTEIN CASEY J.
GRESPAN SILVIO
SUNG KUO-HUA
ZHONG JOHN Z.
YOUNGS LYNN
Assignee: APPLE INC
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Family ID: 42264350