PATENT DOCUMENT

Publication Number: US-8608896-B2
Application Number: US-201113231818-A
Country: US
Kind Code: B2

Title: Liquid adhesive lamination for precision adhesive control

Abstract:
Methods for liquid adhesive lamination for precision adhesive control are provided. Precision liquid adhesive control can be obtained by first patterning liquid adhesive in a thin pre-coat layer on a substrate. A second adhesive layer can then be patterned on top of the pre-coat layer. When the second substrate is pressed onto the first substrate, the second substrate first comes into contact with the second adhesive layer. The adhesive can then be spread uniformly across the two substrates without forming voids. Alternatively, a single liquid adhesive layer can be formed in a three dimensional gradient pattern.

Claims:
What is claimed is: 
     
       1. A method comprising:
 forming an adhesive layer on a first substrate; 
 aligning a second substrate to the first substrate; and 
 applying a pressure to bond the first substrate to the second substrate, wherein the adhesive layer is formed in a three dimensional gradient pattern, wherein the three dimensional gradient pattern has at least one planar surface that extends above a surface of the first substrate, and wherein the three dimensional gradient pattern is a gradient pyramid pattern, wherein the first substrate is associated with an electronic device. 
 
     
     
       2. The method of  claim 1 , wherein first opposing sides of the gradient pyramid pattern are closer to first opposing edges of the first substrate than second opposing sides of the gradient pyramid pattern are to second opposing edges of the first substrate. 
     
     
       3. The method of  claim 1 , wherein the adhesive layer is thicker in a first region of the first substrate than in a second region of the first substrate. 
     
     
       4. The method of  claim 3 , wherein applying pressure to bond the first substrate to the second substrate includes forming an initial wetting pattern between the second substrate and the portion of the adhesive layer in the first region of the first substrate as the substrates are being pushed together. 
     
     
       5. The method of  claim 3 , wherein forming the adhesive layer on the first substrate comprises:
 dispensing adhesive on the first substrate; and 
 applying an electrical field to the adhesive, wherein an attraction force of the electrical field is stronger in the first region of the first substrate than in the second region of the first substrate. 
 
     
     
       6. The method of  claim 3 , wherein aligning the second substrate to the first substrate includes aligning the second substrate at an angle to the first substrate, and wherein applying pressure to bond the first substrate to the second substrate includes moving the second substrate such that the angle between the second substrate and the first substrate is decreased. 
     
     
       7. the method of  claim 6 , wherein applying pressure to bond the first substrate to the second substrate includes pushing excess adhesive from the first region to the second region. 
     
     
       8. The method of  claim 6 , wherein at least one of the first and second substrates is a flexible substrate. 
     
     
       9. the method of  claim 8 , wherein at least one of the first and second substrates is moved on a conveyor across a roller, thereby decreasing the angle between the second substrate and the first substrate. 
     
     
       10. The method of  claim 1 , wherein the gradient pyramid pattern comprises a protruding portion of the adhesive layer. 
     
     
       11. A method comprising:
 forming an adhesive layer on a first substrate by forming the adhesive layer in a three dimensional gradient pattern that includes a first portion and a protruding second portion on the first portion; 
 aligning a second substrate to the first substrate; and 
 applying pressure to bond the first substrate to the second substrate, wherein at least one of the first and second substrates comprises a touch sensor substrate. 
 
     
     
       12. The method defined in  claim 11  wherein the first portion is formed in contact with the first substrate. 
     
     
       13. The method defined in  claim 12  wherein the first portion comprises a center, and wherein the protruding second portion is a pyramid patterned portion that is located at the center of the first portion. 
     
     
       14. The method defined in  claim 13  wherein the pyramid patterned portion comprises a tip and wherein applying pressure to bond the first substrate to the second substrate comprises moving the second substrate into contact with the tip of the pyramid patterned portion. 
     
     
       15. A method comprising:
 forming a patterned adhesive layer on a substrate that is associated with an electronic device display, wherein the patterned adhesive layer is formed in a three dimensional gradient pattern; 
 aligning an additional substrate to the substrate that is associated with the electronic device display; and 
 adhering the substrate that is associated with the electronic device display to the second substrate using the patterned adhesive layer, wherein forming the patterned adhesive layer comprises forming a pyramid shaped patterned adhesive layer. 
 
     
     
       16. the method defined in  claim 15 , wherein the substrate that is associated with the electronic device display comprises a portion of a liquid crystal display. 
     
     
       17. The method defined in  claim 15 , wherein the additional substrate comprises a touch sensor panel situated on the substrate. 
     
     
       18. The method defined in  claim 17 , wherein forming the patterned adhesive layer comprises:
 forming a first patterned adhesive layer; and 
 forming a protrusion on the first patterned adhesive layer. 
 
     
     
       19. The method defined in  claim 18 , wherein forming the protrusion on the first patterned adhesive layer comprises forming a pyramid pattern on the first patterned adhesive layer.

Description:
FIELD OF THE DISCLOSURE 
     This relates generally to substrates and, more particularly, to placement of a liquid adhesive on a substrate. 
     BACKGROUND OF THE DISCLOSURE 
     Electronic devices can generally include at least one substrate with another substrate and/or electrical components adhered thereto. Fabrication of substrates can involve applying an adhesive to a surface of a substrate and using the applied adhesive to adhere another substrate and/or electrical component to the substrate surface. A liquid adhesive is preferred because of its flowability and compliance, which allows the adhesive to easily cover many different substrate configurations and topologies. However, the adhesive&#39;s flowability can also be problematic because of the difficulty in preventing air pockets from forming during the spreading process, causing bubbles or voids in the adhesive as it solidifies, and such voids in the adhesive can interfere with the performance of the substrate device. Additionally, the use of liquid adhesives can result in non-uniform thickness and spread over the substrate, and the adhesive can fail to cover the entire target adhesive area or overflow past the boundaries of the target adhesive area. 
     SUMMARY 
     This relates to patterning liquid adhesive on a substrate in a pattern designed to minimize the formation of voids in the adhesive and to provide uniform adhesive coverage and thickness as the substrate is adhered to another substrate and/or electrical components. Liquid adhesive can be patterned on a substrate, and a second substrate can then be pressed onto the first. During this process the dispensed adhesive pattern can spread out into the final coverage area. 
     Precision liquid adhesive control can be obtained by first patterning liquid adhesive in a thin pre-coat layer on a substrate. The pre-coat layer can allow the adhesive to spread faster over the target adhesive area. A second adhesive layer can then be patterned on top of the pre-coat layer. This second adhesive layer can provide an initial wetting pattern (i.e., the points of first contact between the adhesive and the second substrate). Additionally, the second adhesive layer can be provided in a pattern that will spread in such a way so as to avoid the formation of voids. Accordingly, when the second substrate is pressed onto the first substrate, the second substrate first comes into contact with the second adhesive layer. The adhesive can then be spread uniformly across the two substrates without forming voids. 
     Alternatively, a single liquid adhesive layer can be formed in a three dimensional gradient pattern. Liquid adhesive can be patterned with varying thickness across the first substrate. For example, the adhesive can be layered in a gradient pyramid pattern. The tip of the pyramid can provide an initial wetting point of first contact between the adhesive and the second substrate. As the two substrates are pushed together, the second substrate comes into contact first with the tip of the pyramid, and then with the sides of the pyramid all the way down to the edges. The adhesive can then be spread uniformly across the two substrates without forming voids. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an exemplary pre-coat layer deposition process according to embodiments of the disclosure. 
         FIG. 1B  illustrates an exemplary adhesive patterning process according to embodiments of the disclosure. 
         FIG. 1C  illustrates an exemplary substrate alignment process according to embodiments of the disclosure. 
         FIG. 1D  illustrates an exemplary adhesion process according to embodiments of the disclosure. 
         FIG. 2A  illustrates an exemplary star adhesive pattern according to embodiments of the disclosure. 
         FIG. 2B  illustrates an exemplary butterfly adhesive pattern according to embodiments of the disclosure. 
         FIG. 2C  illustrates an exemplary spot adhesive pattern according to embodiments of the disclosure. 
         FIG. 2D  illustrates an exemplary fishbone pattern according to embodiments of the disclosure. 
         FIG. 2E  illustrates an additional exemplary double-Y pattern according to embodiments of the disclosure. 
         FIG. 2F  illustrates an additional exemplary star pattern according to embodiments of the disclosure. 
         FIG. 2G  illustrates an exemplary stinger pattern according to embodiments of the disclosure. 
         FIG. 2H  illustrates an additional exemplary butterfly pattern according to embodiments of the disclosure. 
         FIG. 2I  illustrates an additional exemplary fishbone pattern according to embodiments of the disclosure. 
         FIG. 2J  illustrates an exemplary one drop fill pattern according to embodiments of the disclosure. 
         FIG. 3A  illustrates an exemplary fishbone pattern according to embodiments of the disclosure. 
         FIG. 3B  illustrates an exemplary fishbone pattern during the spreading process according to embodiments of the disclosure. 
         FIG. 3C  illustrates an exemplary fishbone pattern during the spreading process according to embodiments of the disclosure. 
         FIG. 3D  illustrates an exemplary fishbone pattern during the spreading process according to embodiments of the disclosure. 
         FIG. 3E  illustrates an exemplary fishbone pattern after the spreading process according to embodiments of the disclosure. 
         FIG. 4A  illustrates an exemplary double-Y pattern with a pyramid pattern at its center according to embodiments of the disclosure. 
         FIG. 4B  illustrates an exemplary double-Y pattern with a pyramid pattern at its center according to embodiments of the disclosure. 
         FIG. 5A  illustrates an exemplary double-Y pattern deposited directly on a substrate without a pre-coat layer according to embodiments of the disclosure. 
         FIG. 5B  illustrates an exemplary accelerated double-Y pattern deposited directly on a substrate without a pre-coat layer according to embodiments of the disclosure. 
         FIG. 6  is a high-level flow diagram illustrating an exemplary method of adhering two substrates according to embodiments of the disclosure. 
         FIG. 7A  illustrates an exemplary gradient pyramid pattern formed on a first substrate according to embodiments of the disclosure. 
         FIG. 7B  illustrates an exemplary gradient pyramid pattern formed on a first substrate according to embodiments of the disclosure. 
         FIG. 8  illustrates a modified gradient pyramid pattern according to embodiments of the disclosure. 
         FIG. 9  illustrates an exemplary needle gap process according to embodiments of the disclosure. 
         FIG. 10A  illustrates an exemplary bird-beak process according to embodiments of the disclosure. 
         FIG. 10B  illustrates an additional exemplary bird-beak process according to embodiments of the disclosure. 
         FIG. 11  illustrates an exemplary bird-beak process with a flexible substrate according to embodiments of the disclosure. 
         FIG. 12  illustrates an exemplary computing system including a touch sensor panel situated on a substrate that has been adhered to another substrate and/or electrical components according to embodiments of the disclosure. 
         FIG. 13A  illustrates an exemplary mobile telephone having a touch sensor panel situated on a substrate that has been adhered to another substrate and/or electrical components according to embodiments of the disclosure. 
         FIG. 13B  illustrates an exemplary digital media player having a touch sensor panel situated on a substrate that has been adhered to another substrate and/or electrical components according to embodiments of the disclosure. 
         FIG. 13C  illustrates an exemplary personal computer having a touch sensor panel (trackpad) and/or display situated on a substrate that has been adhered to another substrate and/or electrical components according to embodiments of the disclosure. 
         FIG. 14  illustrates an exemplary adhesive dispenser according to embodiments of the disclosure. 
         FIG. 15  illustrates an additional exemplary adhesive dispenser according to embodiments of the disclosure. 
         FIG. 16  illustrates an equivalent functional drawing of adhesive flow through an adhesive dispenser according to embodiments of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of embodiments, reference is made to the accompanying drawings which form a part hereof, and in which it is shown by way of illustration specific embodiments which 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 disclosed embodiments. 
     Various embodiments relate to patterning liquid adhesive on a substrate in a pattern designed to minimize the formation of voids in the adhesive and to provide uniform adhesive coverage and thickness as the substrate is adhered to another substrate and/or electrical components. Liquid adhesive can be patterned on a substrate, and a second substrate can then be pressed onto the first. During this process the dispensed adhesive pattern can spread out into the final coverage area. 
     Precision liquid adhesive control can be obtained by first patterning liquid adhesive in a thin pre-coat layer on a substrate. The pre-coat layer can allow the adhesive to spread faster over the target adhesive area. A second adhesive layer can then be patterned on top of the pre-coat layer. This second adhesive layer can provide an initial wetting pattern (i.e., the points of first contact between the adhesive and the second substrate). Additionally, the second adhesive layer can be provided in a pattern that will spread in such a way so as to avoid the formation of voids. Accordingly, when the second substrate is pressed onto the first substrate, the second substrate first comes into contact with the second adhesive layer. The adhesive can then be spread uniformly across the two substrates without forming voids. 
     Alternatively, a single liquid adhesive layer can be formed in a three dimensional gradient pattern. Liquid adhesive can be patterned with varying thickness across the first substrate. For example, the adhesive can be layered in a gradient pyramid pattern. The tip of the pyramid can provide an initial wetting point of first contact between the adhesive and the second substrate. As the two substrates are pushed together, the second substrate comes into contact first with the tip of the pyramid, and then with the sides of the pyramid all the way down to the edges. The adhesive can then be spread uniformly across the two substrates without forming voids. 
     Although embodiments may be described and illustrated herein in terms of touch sensor panels, it should be understood that embodiments are not so limited, but are additionally applicable to any substrate with another substrate and/or electrical components adhered thereto. Furthermore, although embodiments may be described and illustrated herein in terms of liquid optically clear adhesive (LOCA), it should be understood that the embodiments are also applicable to other adhesives, including optically translucent and opaque adhesives. Furthermore, although embodiments may be described and illustrate herein in terms of two-substrate lamination, it should be understood that the embodiments are also applicable to multi-layer lamination of any number of substrates, including lamination of a first substrate to a second substrate followed by lamination of a third substrate to the second substrate. 
       FIGS. 1A-1D  illustrate an exemplary method of adhering two substrates according to embodiments of the disclosure. Each figure in the sequence depicts a portion of the described method. 
       FIG. 1A  illustrates an exemplary pre-coat layer deposition process according to embodiments of the disclosure. Initially, a first substrate  100  is adapted to receive liquid adhesive in one or more regions on its surfaces in order to hold another substrate or material on the first substrate. In some embodiments, the substrate can be glass, plastic, and the like. The substrate can be flat, curved, flexible, rigid, and the like. 
     A pre-coat layer  102  of liquid adhesive can be dispensed onto a surface of the first substrate  100 . In some embodiments the liquid adhesive can be water- or oil-based, conductive or dielectric, and so on, depending on placement needs. In some embodiments, the pre-coat layer can be formed in a rectangular shape (e.g., as depicted by pre-coat layer  102 ). However, the pre-coat layer may be formed using any pattern or geometry according to embodiments. The shape of the pre-coat layer may be defined by the shapes of the first substrate and its surfaces as well as the shape of the second substrate or other material to be adhered to the first substrate. A pre-coat layer that thinly covers a target region of a first substrate can reduce the time it takes for any additional layers of adhesive to spread over the target region when a second substrate is pressed onto the first substrate. 
       FIG. 1B  illustrates an exemplary adhesive patterning process according to embodiments of the disclosure. A liquid adhesive pattern  104  can be dispensed on the first substrate  100  on top of the pre-coat layer  102 . In some embodiments, the liquid adhesive pattern can form a double-Y pattern (e.g., as depicted by liquid adhesive pattern  104 ). However, the liquid adhesive pattern may be formed using any pattern or geometry according to various embodiments. The liquid adhesive pattern  104  can be patterned to avoid the formation of voids during the spreading phase. For example, the double-Y pattern of the liquid adhesive pattern  104  can spread outward in such a way so as to avoid the formation of voids. Additionally, the liquid adhesive pattern  104  can be patterned to provide boundary control and uniform spread and thickness over the target adhesive area. Additional liquid adhesive patterns are described with reference to  FIGS. 2A-2D . 
       FIG. 1C  illustrates an exemplary substrate alignment process according to embodiments of the disclosure. The first substrate  100  can be aligned with a second substrate  106  with the adhesive layers  102  and  104  facing the second substrate. The two substrates  100  and  106  can be aligned so that, when pressed together, the second substrate will first contact the liquid adhesive pattern  104  before contacting either the pre-coat layer  102  or the first substrate  100 . In this way, the liquid adhesive pattern  104  can provide the initial wetting pattern for the adhering process. This can help to ensure that the liquid adhesive pattern  104  will largely determine the spread of the adhesive in such a way so as to avoid the formation of voids or bubbles in the adhesive. 
       FIG. 1D  illustrates an exemplary adhesion process according to embodiments of the disclosure. After alignment, the second substrate  106  can be pressed onto the first substrate  100  until the distance between the two substrates is no less than a target final gap distance. During the adhesion process, the liquid adhesive pattern  104  can spread out over the pre-coat layer  104  to form a single uniform adhesive layer  108  that bonds the first substrate  100  to the second substrate  106 . The liquid adhesive pattern  104  can be patterned to avoid the formation of voids in the adhesive layer  108 . Additionally, the liquid adhesive pattern  104  can be patterned to provide boundary control and uniform spread and thickness over the target adhesive area. 
       FIGS. 2A-2J  illustrate liquid adhesive patterns according to various embodiments. Each pattern can be dispensed on top of a pre-coat layer according to the method illustrated in  FIGS. 1A-1D . Alternatively, each pattern can be dispensed directly on a substrate without a pre-coat layer. The patterns can be designed to provide uniform adhesive coverage and to prevent the formation of voids during the spreading process. 
       FIG. 2A  illustrates an exemplary star adhesive pattern  200  according to embodiments of the disclosure. Although  FIG. 2A  depicts the star pattern  200  with eight arms, any number of arms can be formed according to various embodiments. Furthermore, according to various embodiments, the length and width of each arm can vary according to the shape and size of the substrate and the target region of the adhesive pattern. 
       FIG. 2B  illustrates an exemplary butterfly adhesive pattern  202  according to embodiments of the disclosure. The butterfly adhesive pattern  202  can be formed as a double-Y pattern modified with additional arms such as arm  204 . Although  FIG. 2B  depicts the butterfly pattern  202  as a double-Y pattern modified with four additional arms, any number of additional arms can be formed in a butterfly pattern according to various embodiments. 
       FIG. 2C  illustrates an exemplary spot adhesive pattern  206  according to embodiments of the disclosure. The spot pattern  206  can form an initial wetting pattern and can be any size according to various embodiments. 
       FIG. 2D  illustrates an exemplary fishbone pattern  208  according to embodiments of the disclosure. The fishbone pattern  208  can be formed as a narrow double-Y pattern modified with ribs such as rib  210 . Although  FIG. 2D  depicts the fishbone pattern  208  as a narrow double-Y pattern modified with six ribs, any number of ribs can be formed in a fishbone pattern according to various embodiments. 
       FIG. 2E  illustrates an additional exemplary double-Y pattern  212  according to embodiments of the disclosure. 
       FIG. 2F  illustrates an additional exemplary star pattern  214  according to embodiments of the disclosure. 
       FIG. 2G  illustrates an exemplary stinger pattern  216  according to embodiments of the disclosure. 
       FIG. 2H  illustrates an additional exemplary butterfly pattern  218  according to embodiments of the disclosure. 
       FIG. 2I  illustrates an additional exemplary fishbone pattern  220  according to embodiments of the disclosure. 
       FIG. 2J  illustrates an exemplary one drop fill pattern  222  according to embodiments of the disclosure. The one drop fill pattern  222  can be formed as a plurality of adhesive spots across a substrate surface. Each spot can vary in size and thickness. Additionally, a one drop fill pattern can be formed with any number of spots. According to some embodiments, spots near the center of a substrate can be larger and thicker than spots around the perimeter of the substrate. The one drop fill pattern  222  can be formed to provide uniform thickness and boundary control after the spreading process. 
       FIGS. 3A-3E  illustrate an exemplary spreading process according to embodiments of the disclosure. Each figure in the sequence depicts a time-lapse snapshot of the described process. 
       FIG. 3A  illustrates an exemplary fishbone pattern  300  according to embodiments of the disclosure. The fishbone  300  has been patterned on a pre-coat layer  302 . 
       FIG. 3B  illustrates an exemplary fishbone pattern  300  during the spreading process according to embodiments of the disclosure. At an early point in the spreading process after a second substrate has been pressed onto a first substrate, the fishbone pattern  300  may begin to spread out over the pre-coat layer  302 , and the arms and ribs of the pattern may begin to broaden. 
       FIG. 3C  illustrates an exemplary fishbone pattern  300  during the spreading process according to embodiments of the disclosure. As the spreading continues, the arms and the ribs may begin to flow into one another. 
       FIG. 3D  illustrates an exemplary fishbone pattern  300  during the spreading process according to embodiments of the disclosure. As the spreading is nearly complete, the arms and the ribs may flow into a uniform layer over the pre-coat layer  302 . The initial configuration of the arms and ribs can prevent voids from forming as the pattern spreads. 
       FIG. 3E  illustrates an exemplary fishbone pattern after the spreading process according to embodiments of the disclosure. After the spreading process is complete, the fishbone pattern  300  and the pre-coat layer  302  can flow into a single uniform adhesive layer  304 . 
     In some embodiments, an electrical field can be applied to the liquid adhesive pattern to create an initial wetting pattern that can be smaller in area than the liquid adhesive pattern itself  FIGS. 4A and 4B  illustrate an exemplary double-Y pattern  400  with a pyramid pattern  402  at its center according to embodiments of the disclosure. After the liquid adhesive pattern  400  has been deposited, an electrical field  404  can be applied to the liquid adhesive pattern to create an initial wetting pattern in the form of a pyramid pattern  402 . The electrical field can create an electrical attraction at a target location, causing the liquid adhesive at that location to form a pyramid pattern, such as pyramid pattern  402 . Although  FIGS. 4A and 4B  depict the liquid adhesive pattern  400  as a double-Y pattern, an electrical field can be applied to any liquid adhesive pattern to create an initial wetting pattern according to various embodiments. Additionally, although  FIGS. 4A and 4B  depict the initial wetting pattern  402  as a pyramid pattern, an electrical field can be applied to create other initial wetting patterns according to various embodiments. 
       FIG. 5A  illustrates an exemplary double-Y pattern  500  deposited directly on a substrate without a pre-coat layer according to embodiments of the disclosure. Any liquid adhesive pattern can be deposited directly on a first substrate without a pre-coat layer, according to various embodiments. However, the spreading process can take more time without a pre-coat layer. 
       FIG. 5B  illustrates an exemplary accelerated double-Y pattern  502  deposited directly on a substrate without a pre-coat layer according to embodiments of the disclosure. An accelerated double-Y pattern can mimic the shape of a normal double-Y pattern after it has partially spread. Accordingly, the spreading process for the accelerated double-Y pattern  502  can take less time than the spreading process for the double-Y pattern  500 . In various embodiments, any liquid adhesive pattern can be deposited as an accelerated pattern, mimicking the shape of the liquid adhesive pattern after it has partially spread. 
       FIG. 6  is a high-level flow diagram illustrating an exemplary method of adhering two substrates according to embodiments of the disclosure. At block  600 , a first adhesive layer can be formed on a first substrate. The first adhesive layer can be a pre-coat layer formed over an entire target adhesive region of the substrate. 
     At block  602 , a second adhesive layer can be formed on the first substrate. The second adhesive layer can be thicker than the first adhesive layer, and it can form a liquid adhesive pattern. The liquid adhesive pattern can be a star pattern, a butterfly pattern, a spot pattern, a fishbone pattern, or the like. 
     At block  604 , the first and second substrates can be aligned. The first and second substrates can be aligned so that, when pressed together, the second substrate will first contact the liquid adhesive pattern before contacting either the pre-coat layer or the first substrate. In this way, the liquid adhesive pattern can provide the initial wetting pattern for the adhering process. 
     At block  606 , pressure can be applied to bond the first and second substrates. The second substrate can be pressed onto the first substrate until the distance between the two substrates is no less than a target final gap distance. During the adhesion process, the liquid adhesive pattern can spread out over the pre-coat layer to form a single adhesive layer that bonds the first substrate to the second substrate. 
       FIGS. 7A and 7B  illustrate an exemplary gradient pyramid pattern formed on a first substrate according to embodiments of the disclosure. A three dimensional gradient pattern  702  can be formed on a first substrate  700 . In a three dimensional gradient pattern, the thickness of the adhesive layer can vary across the surface of the first substrate. For example, in the gradient pyramid pattern  702 , at the apex of the pattern  704  the adhesive layer can be thicker than at the edges of the pattern  706 . Additionally, the thickness of the adhesive layer can vary between the edges  706  and the apex  704 . Accordingly, the adhesive layer can be thicker in the center region of the first substrate than in the edge region of the first substrate. In alternate embodiments, the adhesive layer can be thicker in the edge region than in the center region. 
     According to various embodiments, the thickest portions of the adhesive layer in a three dimensional gradient pattern can form an initial wetting pattern between the adhesive and a second substrate as the first and second substrates are pushed together. For example, the apex  704  of the gradient pyramid pattern  702  can form an initial wetting pattern. 
     Although  FIGS. 7A and 7B  depict a gradient pyramid pattern  702 , a three dimensional gradient pattern can be formed as any pattern with varying adhesive layer thickness across the surface of a substrate.  FIG. 8  illustrates a modified gradient pyramid pattern according to embodiments of the disclosure. A three dimensional gradient pattern may be configured to control uniform adhesive spreading. For example, modified gradient pyramid pattern  802  can be formed on a first substrate  800 . First pyramid sides  804  can be formed closer to the edges of the first substrate  800  than second pyramid sides  806 . As a result, there can be less adhesive at sides  806  than at sides  804 . Such a configuration can control adhesive flow during the spreading process so that liquid adhesive does not flow outside a target adhesive area. Furthermore, such a configuration can ensure that after the spreading process the liquid adhesive uniformly covers the target adhesive area. 
     A three dimensional gradient pattern of liquid adhesive can be formed by any of several methods according to various embodiments. For example, an adhesive dispenser can vary its dispensing rate as it moves across a substrate. A region subject to a dispensing rate higher than in other regions can accumulate more adhesive, resulting in a thicker adhesive layer in such a region. By this process, the thickness of the adhesive layer can be varied across the surface of the substrate. In some embodiments, the same result can be achieved by varying the movement speed of the dispenser as the dispenser moves across a substrate and dispenses at a constant rate. 
     In some embodiments, liquid adhesive can be applied through a stencil or mesh that varies the area of each opening. A region beneath an opening larger than other openings in the stencil or mesh can accumulate more adhesive, resulting in a thicker adhesive layer in such a region. By this process, the thickness of the adhesive layer can be varied across the surface of the substrate. 
     In some embodiments, a three dimensional gradient pattern can be formed by applying a differential electrical field to an adhesive layer according to some embodiments. A region subject to an electrical attraction stronger than in other regions can accumulate more adhesive, resulting in a thicker adhesive layer in such a region. By this process, the thickness of the adhesive layer can be varied across the surface of the substrate. 
     Additionally, a three dimensional gradient pattern can be formed by combinations of various dispensing methods. For example, a three dimensional gradient pattern can be formed by first dispensing adhesive at a varying dispense rate across the surface of a substrate and then applying a differential electrical field to the adhesive. 
       FIG. 14  illustrates an exemplary adhesive dispenser  1400  according to embodiments of the disclosure. Liquid adhesive flows from an inlet  1402 , through a cavity  1404 , and out a slot  1406 . According to various embodiments, an inlet can have horizontal, vertical, or diagonal portions. Additionally, an inlet can have any width to accommodate adhesive flow. 
       FIG. 15  illustrates an additional exemplary adhesive dispenser  1500  according to embodiments of the disclosure. Both a cavity  1504  and a slot  1506  can extend along the length of the adhesive dispenser  1500 . Accordingly, the slot  1506  can dispense adhesive across the length of a substrate and then cover the entire target adhesive area as the dispenser moves across the width of the substrate. Additionally, the movement speed of the dispenser can be varied to vary the thickness of the dispensed adhesive layer. 
     The slot width can be varied along the length of the adhesive dispenser to vary the adhesive dispense rate along the length of the dispenser. For example, if a first portion of the slot  1506  is wider than a second portion of the slot, liquid adhesive can be dispensed at a higher rate out of the first portion than out of the second portion. Alternatively, the width of the cavity  1504  can be tapered along the length of the dispenser to achieve a similar effect. Accordingly, the adhesive dispenser  1500  can be used to form a three dimensional gradient pattern on a substrate by dispensing an adhesive layer that varies in thickness across the surface of a substrate. 
       FIG. 16  illustrates an equivalent functional drawing of adhesive flow through an adhesive dispenser according to embodiments of the disclosure. The resistance at the inlet  1602  can determine the rate at which adhesive is accepted into the dispenser. The resistance of the cavity  1604  can increase along the length of dispenser as the cavity tapers to a more narrow width. Accordingly, adhesive flow can vary at each portion of the cavity  1604 , depending on the distance from the inlet and the width of the cavity. Finally, the resistance of the slot  1606  can vary as the slot width is varied along the length of the dispenser, and thus adhesive flow can vary at each portion of the slot according to the width of slot. 
     In some embodiments, a dispenser can have multiple inlets, each with separate cavities and slots. Alternatively, each cavity can all flow to the same slot. Each cavity can be a different size, which can affect the dispense rate out of each slot. For example, if a first cavity is larger than a second cavity, then liquid adhesive can flow faster through the first cavity than through the second cavity. Accordingly, an adhesive dispenser can be used to form a three dimensional gradient pattern on a substrate by dispensing an adhesive layer that varies in thickness across the surface of a substrate. 
     According to embodiments of the disclosure, an initial wetting pattern can be formed in several other ways.  FIG. 9  illustrates an exemplary needle gap process according to embodiments of the disclosure. A pre-coat layer  904  can be formed on a first substrate  900 . The first substrate can be aligned to a second substrate  902 . Liquid adhesive  906  can then be dispensed by a needle dispenser  908 . The liquid adhesive  906  can be dispensed, and an initial wetting pattern can be created as the liquid adhesive contacts both the second substrate  902  and the pre-coat layer  904 . The needle dispenser  908  can be removed, and the second substrate  902  can be pressed onto the first substrate  900  until the distance between the two substrates is no less than a target final gap distance. 
       FIGS. 10A and 10B  illustrate an exemplary bird-beak process according to embodiments of the disclosure. A pre-coat layer  1002  can be formed on a first substrate  1000 . A second substrate  1004  can then be aligned at an angle to the first substrate  1000  such that an initial wetting pattern  1006  can be formed between the second substrate and the pre-coat layer  1002 . The second substrate  1004  can then be moved such that the angle between the second substrate and the first substrate  1000  is decreased and the pre-coat layer  1002  can bond with the target adhesive region of the second substrate. 
     In some embodiments the pre-coat layer  1002  can be a three dimensional gradient pattern, as illustrated in  FIG. 10B . The layer can be thickest in the region of the initial wetting pattern  1006 . In such an embodiment, excess adhesive can be pushed from the region of the initial wetting pattern  1006  to other regions of the first substrate as the two substrates are pushed together. 
     A bird-beak process can also be accomplished with a flexible substrate on a roller.  FIG. 11  illustrates an exemplary bird-beak process with a flexible substrate according to embodiments of the disclosure. A pre-coat layer  1100  can be formed on a flexible first substrate  1102 . The flexible first substrate  1102  can be moved on a first conveyor  1104  across a roller  1106 . Additionally, a second substrate  1108  can be moved on a second conveyor  1110 . The movement of the first conveyor  1104  and the second conveyor  1110  can cause the second substrate  1108  to contact the pre-coat layer  1100  at an initial wetting pattern  1112 . As the two conveyors move, the pre-coat layer  1002  can bond with the target adhesive region of the second substrate. In some embodiments, at least one of the first and second substrates can be flexible. 
       FIG. 12  illustrates exemplary computing system  1200  that can include a touch sensor panel  1224  situated on a substrate that has been adhered to another substrate and/or electrical components by one or more of the embodiments described above. Computing system  1200  can include one or more panel processors  1202  and peripherals  1204 , and panel subsystem  1206 . Peripherals  1204  can include, but are not limited to, random access memory (RAM) or other types of memory or storage, watchdog timers and the like. Panel subsystem  1206  can include, but is not limited to, one or more sense channels  1208 , channel scan logic  1210  and driver logic  1214 . Channel scan logic  1210  can access RAM  412 , autonomously read data from the sense channels and provide control for the sense channels. In addition, channel scan logic  1210  can control driver logic  1214  to generate stimulation signals  1216  at various frequencies and phases that can be selectively applied to drive lines of touch sensor panel  1224 . In some embodiments, panel subsystem  1206 , panel processor  1202  and peripherals  1204  can be integrated into a single application specific integrated circuit (ASIC). 
     Touch sensor panel  1224  can include a capacitive sensing medium having a plurality of drive lines and a plurality of sense lines, although other sensing media can also be used. Each intersection of drive and sense lines can represent a capacitive sensing node and can be viewed as picture element (pixel)  1226 , which can be particularly useful when touch sensor panel  1224  is viewed as capturing an “image” of touch. (In other words, after panel subsystem  1206  has determined whether a touch event has been detected at each touch sensor in the touch sensor panel, the pattern of touch sensors in the multi-touch panel at which a touch event occurred can be viewed as an “image” of touch (e.g. a pattern of fingers touching the panel).) Each sense line of touch sensor panel  1224  can drive sense channel  1208  (also referred to herein as an event detection and demodulation circuit) in panel subsystem  1206 . 
     Computing system  1200  can also include host processor  1228  for receiving outputs from panel processor  1202  and performing actions based on the outputs that can include, but are not limited to, moving an object such as a cursor or pointer, scrolling or panning, adjusting control settings, opening a file or document, viewing a menu, making a selection, executing instructions, operating a peripheral device coupled to the host device, answering a telephone call, placing a telephone call, terminating a telephone call, changing the volume or audio settings, storing information related to telephone communications such as addresses, frequently dialed numbers, received calls, missed calls, logging onto a computer or a computer network, permitting authorized individuals access to restricted areas of the computer or computer network, loading a user profile associated with a user&#39;s preferred arrangement of the computer desktop, permitting access to web content, launching a particular program, encrypting or decoding a message, and/or the like. Host processor  1228  can also perform additional functions that may not be related to panel processing, and can be coupled to program storage  1232  and display device  1230  such as an LCD display for providing a UI to a user of the device. Display device  1230  together with touch sensor panel  1224 , when located partially or entirely under the touch sensor panel, can form touch screen  1218 . Display device  1230  can be adhered to touch sensor panel  1224  by one or more of the embodiments described above. 
       FIG. 13A  illustrates exemplary mobile telephone  1336  that can include touch sensor panel  1324  and display device  1330 , the touch sensor panel situated on a substrate that has been adhered to another substrate and/or electrical components by one or more of the embodiments described above. 
       FIG. 13B  illustrates exemplary digital media player  1340  that can include touch sensor panel  1324  and display device  1330 , the touch sensor panel situated on a substrate that has been adhered to another substrate and/or electrical components by one or more of the embodiments described above. 
       FIG. 13C  illustrates exemplary personal computer  1344  that can include touch sensor panel (trackpad)  1324  and display  1330 , the touch sensor panel and/or display of the personal computer (in embodiments where the display is part of a touch screen) including a substrate that has been adhered to another substrate and/or electrical components by one or more of the embodiments described above. The mobile telephone, media player and personal computer of  FIGS. 13A ,  13 B and  13 C can achieve improved overall durability by utilizing the substrate adhesive layer formed according to various embodiments. 
     Although the disclosed embodiments 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 the disclosed embodiments as defined by the appended claims.

Metadata:
Filing Date: 20110913
Publication Date: 20131217
Grant Date: 20131217
Priority Date: 20110913
Inventors: HORSTKEMPER RALF
FEINSTEIN CASEY J.
SUNG KUO-HUA
Assignee: APPLE INC
CPC Classifications: [{"code": "B29C65/5064", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/3452", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/342", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/524", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/524", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C66/45", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/45", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/4855", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J2301/208", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/5021", "inventive": true, "first": true, "tree": "[]"}, {"code": "B29C65/5021", "inventive": true, "first": true, "tree": "[]"}, {"code": "C09J5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/4855", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/3452", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C66/342", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/5057", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J2301/208", "inventive": false, "first": false, "tree": "[]"}, {"code": "B29C65/5057", "inventive": false, "first": false, "tree": "[]"}, {"code": "C09J5/00", "inventive": true, "first": false, "tree": "[]"}, {"code": "B29C65/5064", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 47828763