Touch panel including a layered structure with first and second mesh terminal layers directly overlaid on each other and touch panel production method

Abstract

A touch panel comprises, a substrate, a layered structure formed in a sensing region defined on one side of the substrate, the layered structure including at least a first conductor layer made of a first hardened conductive ink, a second conductor layer made of a second hardened conductive ink and an insulating layer disposed therebetween, and an external connection terminal formed outside the sensing region on the one side of the substrate, wherein the external connection terminal comprises a first terminal layer made of the first hardened conductive ink and a second terminal layer made of the second hardened conductive ink, such that the first terminal layer and the second terminal layer are directly overlaid on each other.

Claims

1. A touch panel comprising: a substrate; a layered structure formed in a sensing region defined on one side of the substrate, the layered structure including at least a first conductor layer made of a first hardened conductive ink, a second conductor layer made of a second hardened conductive ink and an insulating layer disposed therebetween; and an external connection terminal formed outside the sensing region on the one side of the substrate; wherein the external connection terminal comprises a first terminal layer made of the first hardened conductive ink and a second terminal layer made of the second hardened conductive ink, such that the first terminal layer and the second terminal layer are directly overlaid on each other at a most terminal end of a conductive path of the touch panel; wherein the first terminal layer forms a first mesh of fine lines and the second terminal layer forms a second mesh of fine lines; wherein each of the first mesh of fine lines and the second mesh of fine lines has a grid pattern having a pair of periodicity directions and a pair of grid periods corresponding thereto, such that the first mesh of fine lines and the second mesh of fine lines are identical to each other in terms of the pair of periodicity directions and the pair of grid periods; and the first mesh of fine lines and the second mesh of fine lines are overlaid on each other in such a way that the first mesh of fine lines and the second mesh of fine lines are deviated from each other in both of the pair of periodicity directions, respectively by from ¼ to ¾, inclusive, of the grid period corresponding to the periodicity direction.

2. The touch panel according to claim 1, further comprising an anisotropic conductive film connected to the external connection terminal; wherein the pair of grid periods are equal to each other; and the anisotropic conductive film contains a plurality of conductive particles each having a diameter greater than or equal to ½ of the grid period; whereby the external connection terminal may be connected to an electrode of an external circuit through the anisotropic conductive film.

3. The touch panel according to claim 1, wherein each of the first conductor layer and the second conductor layer forms a mesh of fine lines.

4. The touch panel according to claim 2, wherein each of the first conductor layer and the second conductor layer forms a mesh of fine lines.

5. A touch panel production method for producing the touch panel according to claim 1, the method comprising: simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using a first conductive ink; printing the insulating layer by using an insulating ink; and simultaneously printing the second conductor layer and the second terminal layer by using a second conductive ink.

6. A touch panel production method for producing the touch panel according to claim 2, the method comprising: simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using a first conductive ink; printing the insulating layer by using an insulating ink; and simultaneously printing the second conductor layer and the second terminal layer by using a second conductive ink.

7. A touch panel production method for producing the touch panel according to claim 3, the method comprising: simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using a first conductive ink; printing the insulating layer by using an insulating ink; and simultaneously printing the second conductor layer and the second terminal layer by using a second conductive ink.

8. A touch panel production method for producing the touch panel according to claim 4, the method comprising: simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using a first conductive ink; printing the insulating layer by using an insulating ink; and simultaneously printing the second conductor layer and the second terminal layer by using a second conductive ink.

9. The touch panel production method according to claim 5, wherein the simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using the first conductive ink is a gravure offset printing process using a first blanket; and the simultaneously printing the second conductor layer and the second terminal layer by using the second conductive ink is a gravure offset printing process using a second blanket.

10. The touch panel production method according to claim 6, wherein the simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using the first conductive ink is a gravure offset printing process using a first blanket; and the simultaneously printing the second conductor layer and the second terminal layer by using the second conductive ink is a gravure offset printing process using a second blanket.

11. The touch panel production method according to claim 7, wherein the simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using the first conductive ink is a gravure offset printing process using a first blanket; and the simultaneously printing the second conductor layer and the second terminal layer by using the second conductive ink is a gravure offset process printing using a second blanket.

12. The touch panel production method according to claim 8, wherein the simultaneously printing the first conductor layer and the first terminal layer on the one side of the substrate by using the first conductive ink is a gravure offset printing process using a first blanket; and the simultaneously printing the second conductor layer and the second terminal layer by using the second conductive ink is a gravure offset printing process using a second blanket.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a diagram illustrating an example of a conventional configuration of a touch panel;

(2) FIG. 2A is a partial enlarged view illustrating a first conductor layer of the touch panel illustrated in FIG. 1;

(3) FIG. 2B is a partial enlarged view illustrating a second conductor layer of the touch panel illustrated in FIG. 1;

(4) FIG. 3 is a diagram illustrating another example of a conventional configuration of a touch panel;

(5) FIG. 4A is a partial enlarged view illustrating a first terminal layer in one example embodiment of a touch panel according to the present invention;

(6) FIG. 4B is a partial enlarged view illustrating a second terminal layer in one example embodiment of the touch panel according to the present invention;

(7) FIG. 5 is a partial enlarged view illustrating the first terminal layer illustrated in FIG. 4A and the second terminal layer illustrated in FIG. 4B which are overlaid on one another;

(8) FIG. 6 is a diagram illustrating the touch panel connected with an FPC, which is an external circuit;

(9) FIG. 7 is a partial enlarged view illustrating a first conductor layer of a sensing region in one example embodiment of the touch panel according to the present invention;

(10) FIG. 8 is a partial enlarged view illustrating a second conductor layer of a sensing region in one example embodiment of the touch panel according to the present invention; and

(11) FIG. 9 is a partial enlarged view illustrating the first conductor layer illustrated in FIG. 7 and the second conductor layer illustrated in FIG. 8 which are overlaid on one another.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(12) Example embodiments of the present invention will be described below.

(13) FIGS. 4A, 4B and 5 illustrate details of external connection terminals of one example embodiment of a touch panel according to the present invention and FIG. 6 illustrates the example embodiment of the touch panel according to the present invention with an FPC, which is an external circuit, connected with the external connection terminals.

(14) The touch panel in this example differs from the example conventional touch panel illustrated in FIG. 1 in the configuration of external connection terminals formed in an array in the center portion of one of the long sides of the substrate 10 and the configuration in the sensing region 20. The other configurations are basically the same as the configurations illustrated in FIG. 1. Note that details of the configuration in the sensing region 20 are omitted from FIG. 6.

(15) The touch panel has a layered structure in which a first conductor layer made of a first hardened conductive ink, an insulating layer, a second conductor layer made of a second hardened conductive ink, and a protective coating are formed in this order in the sensing region 20 defined on one side of the transparent substrate 10. The insulating layer and the protective coating are made of transparent materials.

(16) External connection terminals 60 located outside the sensing region 20 comprise a first terminal layer 61 made of the first hardened conductive ink and a second terminal layer 62 made of the second hardened conductive ink which are directly overlaid on one another. The first terminal layer 61 forms a first mesh of fine lines as illustrated in FIG. 4A and the second terminal layer 62 forms a second mesh of fine lines as illustrated in FIG. 4B.

(17) Each of the first mesh of fine lines of the first terminal layer 61 and the second mesh of fine lines of the second terminal layer 62 has a grid pattern having a pair of periodicity directions and a pair of grid periods corresponding thereto. The grid pattern of the first mesh of fine lines and the grid pattern of the second mesh of fine lines are identical to each other in terms of the pair of periodicity directions and the pair of grid periods. In this example, each of the grid pattern of the first mesh of fine lines and the grid pattern of the second mesh of fine lines has square unit cells with a side length of 20 μm and the grid periods in the pair of periodicity directions are 20 μm. The width of each fine line of the meshes is 7 μm.

(18) The width and length of the first terminal layer 61 formed of the mesh of fine lines described above are denoted by W1 and L1, respectively, as indicated in FIG. 4A and the width and length of the second terminal layer 62 formed of the mesh of fine lines described above are denoted by W2 and L2, respectively, as indicted in FIG. 4B, where
L1=L2,W1>W2
in this example. That is, the width W2 of the second terminal layer 62 is smaller than the width W1 of the first terminal layer 61.

(19) The second terminal layer 62 is directly overlaid on the first terminal layer 61 to produce a configuration of the external connection terminals 60 as illustrated in FIG. 5. In this example, the first terminal layer 61 and the second terminal layer 62 are overlaid on each other in such a way that they are deviated from each other in both of the pair of periodicity directions, respectively by ½ of the grid period, thereby producing a dense mesh with a grid period of 10 μm as illustrated in FIG. 5. It should be noted that making the width W2 of the second terminal layer 62 smaller than the width W1 of the first terminal layer 61 as described above prevents problems such as contact and short circuit of the second terminal layer 62 with an adjacent portion of the first terminal layer 61 due to misalignment during printing of the second terminal layer 62, for example.

(20) The external connection terminals 60 having the configuration described above are connected to electrodes of an FPC 66, which is an external circuit, through an anisotropic conductive film (ACF) 65 in this example as illustrated in FIG. 6. Note that the electrodes of the FPC 66 are omitted from FIG. 6.

(21) The anisotropic conductive film 65 used for connection between the external connection terminals 60 and the electrodes of the FPC 66 contains conductive particles which are resin particles plated with Au, for example. The anisotropic conductive film 65 in this example contains conductive particles each having a diameter of 10 μm or greater.

(22) The configuration of the external connection terminals 60 of one example embodiment of the touch panel according to the present invention and connection between the external connection terminals 60 and the FPC 66 have been described above. In this example, the external connection terminals 60 comprise two layers, i.e. the first terminal layer 61 formed by a first conductor layer and the second terminal layer 62 formed by a second conductor layer which are overprinted without an insulating layer between them, instead of a single, first conductor layer alone as with conventional external connection terminals. Further, the first and second terminal layers 61, 62 formed of meshes of fine lines have the same grid pattern, which are overlaid on each other in such a way that they are deviated from each other in both of the pair of periodicity directions, respectively by ½ of the grid period.

(23) Since this makes the mesh that forms the external connection terminals 60 in this example denser to increase the wiring density and increase the area of contact with the conductive particles in the anisotropic conductive film 65, the contact resistance can be reduced and the electrical contact quality can be improved over conventional external connection terminals. It should be noted that using the anisotropic conductive film 65 containing conductive particles each having a diameter of 10 μm or greater for connection with the external connection terminals 60 in the form of a mesh with a grid period of 10 μm as described above can significantly increase the probability of contact of the conductive particles with the fine lines of the mesh and therefore can further reduce the contact resistance.

(24) While the mesh of fine lines of the first terminal layer 61 in the form of the grid pattern and the mesh of fine lines of the second terminal layer 62 in the form of the grid pattern are overlaid on each other in such a way that they are deviated from each other in both of the pair of periodicity directions, respectively by ½ of the grid period corresponding to the periodicity direction in the example described above, the deviation between the grid patterns overlaid on each other does not necessarily need to be ½ of the grid period. For example, the deviation between the grid patterns overlaid on each other may be from ¼ to ¾, inclusive, of the grid period in both of the pair of periodicity directions. Note that the grid pattern of the first terminal layer 61 and the grid pattern of the second terminal layer 62 may be overlaid on each other without deviation from each other and even if the grid patterns are overlaid on each other without deviation, the cross-sectional area of each fine line is doubled and therefore the advantageous effect of reducing the electrical resistance by half and the advantageous effect of enhancing the mechanical strength can be achieved.

(25) Further, the unit cell of the grid pattern formed by the first terminal layer 61 and the second terminal layer 62 is not limited to a square shape but may be any other shapes such as a rhombus shape.

(26) A configuration of the sensing region 20 will be described next with reference to FIGS. 7 to 9. FIGS. 7 to 9 illustrate details of the upper left part of FIG. 6.

(27) FIG. 7 illustrates details of the printed wirings of the first conductor layer. A first sensor electrode 70 and a first dummy wiring 80 are formed in the sensing region 20. The first sensor electrode 70 comprises a plurality of electrode rows 73 parallelly arranged in the Y direction, where each of the electrode rows 73 is made up of a plurality of island-like electrodes 71 arranged in the X direction and linked with one another through linkage parts 72. The first dummy wiring 80 is provided in regions in the sensing region 20 other than regions in which the first sensor electrode 70 is provided and are insulated from the first sensor electrode 70.

(28) Each of the first sensor electrode 70 and the first dummy wiring 80 is formed of a mesh of fine lines and shares a first mesh pattern 90 which is a single continuous periodic mesh pattern while gaps 91 where fine lines are broken are formed and disposed at the boundary between the first sensor electrode 70 and the first dummy wiring 80. A unit cell of the first mesh pattern 90 in this example is in the shape of a rhombus with a side length of 400 μm and the width of each of the fine lines making up the mesh is 7 μm. The gaps 91 that insulate between the first sensor electrode 70 and the first dummy wiring 80 are approximately 20 μm. The gaps 91 are depicted relatively enlarged in FIG. 7.

(29) FIG. 8, on the other hand, illustrates details of printed wirings of the second conductor layer. A second sensor electrode 100 and a second dummy wiring 110 are formed in the sensing region 20. The second sensor electrode 100 comprises a plurality of electrode rows 103 parallelly arranged in the X direction, where each of the electrode rows 103 is made up of a plurality of island-like electrodes 101 arranged in the Y direction and linked with one another through linkage parts 102. The second dummy wiring 110 is provided in regions in the sensing region 20 other than regions in which the second sensor electrode 100 is provided and are insulated from the second sensor electrode 100.

(30) Each of the second sensor electrode 100 and the second dummy wiring 110 is formed of a mesh of fine lines and shares a second mesh pattern 120 which is a single continuous periodic mesh pattern while gaps 121 where fine lines are broken are formed and disposed at the boundary between the second sensor electrode 100 and the second dummy wiring 110. The second mesh pattern 120 in this example is identical to the first mesh pattern 90 and the angle which each of the fine lines making up the mesh forms with the long side 21 of the sensing region 20 is also identical to that in the first mesh pattern 90. Note that the gaps 121 are depicted relatively enlarged as in FIG. 7.

(31) FIG. 9 illustrates the printed wirings of the first conductor layer illustrated in FIG. 7 and the printed wirings of the second conductor layer illustrated in FIG. 8 which are stacked with the insulating layer between them. The first mesh pattern 90 of the first conductor layer and the second mesh pattern 120 of the second conductor layer are overlaid on each other in such a way that they intersect at the midpoint that divides each side of the rhombus shape of each unit cell into two 200 μm segments. Consequently, rhombus-shaped cells with a side length of 200 μm are highly uniformly formed in the entire sensing region 20 as illustrated in FIG. 9. It should be noted that the electrode rows 73 of the first sensor electrode 70 and the electrode rows 103 of the second sensor electrode 100 intersect, with the linkage parts 72 and 102 being positioned in locations that coincide with each other.

(32) In this way, in the present example, the first mesh pattern 90 uniformly exists in the sensing region 20 of the first conductor layer in which the first sensor electrode 70 is formed, and the second mesh pattern 120 uniformly exists in the sensing region 20 of the second conductor layer in which the second sensor electrode 100 is formed. Accordingly, visual contrast due to the presence and absence of the meshes of fine lines does not occur in any of the first conductor layer and the second conductor layer and naturally visual contrast does not occur when the first conductor layer and the second conductor layer are overlaid on each other, whereby contrast in the sensing region 20 can be completely eliminated.

(33) A method for producing the touch panel described above will be described below.

(34) 1) First Printing Step

(35) The first conductor layer (first mesh pattern 90) of the sensing region 20 and the first terminal layer 61 are simultaneously printed on one side of the substrate 10 by using a first conductive ink. At the same time, the leads 51, 52 and ground wiring 54 are also simultaneously printed.

(36) 2) Second Printing Step

(37) The insulating layer is printed on the first conductor layer of the sensing region 20 by using an insulating ink.

(38) 3) Third Printing Step

(39) The second conductor layer (second mesh pattern 120) of the sensing region 20 and the second terminal layer 62 are simultaneously printed by using a second conductive ink.

(40) 4) Fourth Printing Step

(41) The protective coating is printed on the entire area of the one side of the substrate 10 using an insulating ink, excluding the regions in which the external connection terminals 60 made up of the first and second terminal layers 61, 62 are formed in an array.

(42) The touch panel is produced by these steps. Note that the first conductive ink used in the first printing step and the second conductive ink used in the third printing step are the same ink containing conductive particles such as silver particles and gravure offset printing is used as the printing method in this example. Different blankets are used in the gravure offset printing process in the first printing step and the gravure offset printing process in the third printing step and the two blankets are alternately used. The reasons are as follows.

(43) If the external connection terminals 60, which are dense meshes as illustrated in FIG. 5, are formed by printing at a time, the problem of rapid swelling of the blanket can occur due to printing of the material of the highly dense wiring. To address this problem, different blankets are used in the first printing step and the third printing step and the two blankets are alternately used. By alternately using the two blankets to print the external connection terminals 60, swelling of the blankets can be slowed down sufficiently (approximately by a factor of 2) compared to using a single blanket to print external connection terminals with the same wiring density. This can increase the mass productivity of the touch panel.

(44) A touch panel and a touch panel production method according to the present invention have been described above. External connection terminals may be printed in three ink layers in the case where production of a touch panel involves three printing steps using a conductive ink, namely the step of printing the first sensor electrode, the step of printing the second sensor electrode and the step of printing leads (frame wirings), for example.