Production method for wiring board and wiring board

Abstract

To prevent printing blur of a fine line.SOLUTION: A wiring board includes a fine line pattern formed on a board surface and consisting of a cured conductive ink. When orthogonal two directions on the board surface are defined as an X direction and a Y direction, with respect to one intersection where three or more fine lines included in the fine line pattern are collected at one point, the wiring board also comprises the other fine line included in a fine line pattern which passes the other point on the board surface at a different position in the X direction and the same position in the Y direction and does not form the other intersection where three or more fine lines are collected at the other point. The other fine line is connected to further other two fine lines included in the fine line pattern on extensions on both sides in an extension direction passing the other point. The further other two fine lines have a mutually identical line width. Between two connection points connected to the further other two fine lines, the line width of the other fine line is 1.5 times or more as large as a minimal value of line widths of the fine lines included in the fine line pattern.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a wiring board including a fine line pattern made of cured conductive ink and a method for producing the wiring board. [Background technology]

[0002] 3 and 4 show the configuration of a capacitive touch panel described in Patent Document 1 as an example of a wiring substrate including a fine-line pattern made of cured conductive ink. This touch panel has a configuration in which a first conductor layer, an insulating layer, a second conductor layer, and a protective film are laminated in this order on a transparent substrate 10. In Fig. 3, the area surrounded by a rectangular frame is a sensor area 20 where the sensor electrodes are located, and detailed illustration of the sensor electrodes is omitted in Fig. 3.

[0003] The sensor electrodes are made up of a first sensor electrode and a second sensor electrode, the first sensor electrode being formed by a first conductor layer, and the second sensor electrode being formed by a second conductor layer.

[0004] As shown in FIG. 4A, the first sensor electrode 30 is configured by a plurality of electrode arrays 33, each of which is formed by connecting portions 32 to a plurality of island-shaped electrodes 31 arranged in the X direction parallel to the long side 21 of the sensor area 20, and which are arranged in parallel in the Y direction parallel to the short side 22 of the sensor area 20.

[0005] As shown in FIG. 4B, the second sensor electrode 40 is configured by arranging multiple electrode rows 43 in parallel in the X direction, each row being made up of multiple island-shaped electrodes 41 arranged in the Y direction and connected by connecting portions 42.

[0006] The first sensor electrode 30 and the second sensor electrode 40 are each formed of a mesh of fine wires, and the electrode rows 33 and 43 are crossed while being insulated from each other, and the connecting portions 32 and 42 are positioned so as to overlap each other.

[0007] Lead wires 51 are drawn out from both ends in the X direction of each electrode row 33 of the first sensor electrode 30, and lead wires 52 are drawn out from one end in the Y direction of each electrode row 43 of the second sensor electrode 40. Of the lead wires 51 and 52 that are arranged in plurality and drawn out from the sensor area 20, only those located at both ends of the array are shown in Figure 3.

[0008] Terminal portions 53 are arranged in the center of one long side of the rectangular transparent substrate 10, and the lead wires 51 and 52 extend to the terminal portions 53 and are connected to the terminal portions 53. A ground wire 54 is formed on the periphery of the transparent substrate 10 so as to surround the sensor region 20 and the lead wires 51 and 52, and is also connected to the terminal portions 53.

[0009] The lead wires 51 and 52 and the terminal portion 53 are formed from the first conductor layer, and the ground wire 54 is formed from both the first and second conductor layers.

[0010] 5 is a diagram showing details of the connection portion between the second sensor electrode 40 and the lead-out wiring 52 described in Patent Document 1, in which a connection portion 52a made of a fine mesh of thin wires is formed at the tip of the lead-out wiring 52. Meanwhile, an extension portion 44 is formed at the edge of the second sensor electrode 40. The extension portion 44 is made up of a large mesh portion 44a formed by extending the mesh that makes up the second sensor electrode 40, and a small mesh portion 44b formed by further extending from the large mesh portion 44a. The small mesh portion 44b is made of a fine mesh of thin wires, and this small mesh portion 44b and the connection portion 52a of the lead-out wiring 52 have the same mesh structure with a square unit cell.

[0011] 5, reference numeral 61 denotes a through hole formed in the insulating layer 60, and the connection portion 52a of the lead wiring 52 and the extension portion 44 of the second sensor electrode 40 are located in this through hole 61 and are connected and conductive to each other, thereby connecting the second sensor electrode 40 formed by the second conductor layer and the lead wiring 52 formed by the first conductor layer. In addition, in FIG. 5, the dashed line denotes the dummy wiring 35 formed on the first conductor layer.

[0012] The first and second conductor layers having the above-described configuration are formed by printing using a conductive ink containing conductive particles such as silver in this example, by gravure offset printing. [Prior art documents] [Patent documents]

[0013] [Patent Document 1] Japanese Patent Application Laid-Open No. 2019-75069 Summary of the Invention [Problem to be solved by the invention]

[0014] As described above, the touch panels shown in Figures 3 to 5 have first and second conductor layers including a mesh pattern of fine lines printed by gravure offset printing using conductive ink. However, it has been found that when forming a fine line pattern by gravure printing or gravure offset printing in this manner, blurred printing occurs on certain fine lines.

[0015] Figure 6 is a photograph showing fading of printing on fine lines in a touch panel having essentially the same layer structure and fine line pattern as the touch panel described above. This photograph shows the portion where the second sensor electrode, consisting of a mesh of fine lines, is connected to the lead-out wiring, and corresponds to part of the diagram showing the connection portion shown in Figure 5 described above. Note that the unit lattice of the mesh of the second sensor electrode is diamond-shaped, as in Figure 5, but in Figure 6 the orientation of the two long and short diagonals of the diamond is 90° different from the orientation of the two long and short diagonals of the diamond of the unit lattice in Figure 5. In Figure 6, arrow S indicates the squeegeeing direction of the doctor blade when this fine line pattern is printed and formed by gravure offset printing, and the dashed dotted line indicates the extension direction of the doctor blade.

[0016] The object of the present invention is to provide a method for producing a wiring board that prevents the occurrence of smeared print on thin lines as shown in FIG. 6, thereby preventing an increase in resistance value and breakage of thin lines due to smeared print, and further to provide a wiring board that has excellent print quality and is free of smeared print. [Means for solving the problem]

[0017] The method for producing a wiring board of the present invention is a method for producing a wiring board including a fine line pattern formed by gravure printing using a conductive ink, and when two orthogonal directions on the surface of the gravure plate on which the recesses of the fine line pattern are formed are the X direction and the Y direction, the gravure plate has recesses of other fine lines included in the fine line pattern that pass through another point on the plate surface that is different in position in the X direction but the same in position in the Y direction with respect to one intersection where the recesses of three or more fine lines included in the fine line pattern converge, and at that other point, do not form another intersection where the recesses of three or more fine lines converge. the recesses of the other thin lines are connected to recesses of two other thin lines included in the thin line pattern on both sides of the extension direction passing through the other point, the recesses of the other two thin lines have the same line width, and the line width of the recesses of the other thin lines is 1.5 times or more the smallest line width of the recesses of the thin lines included in the thin line pattern between the two connection points connecting to the recesses of the other two thin lines, and the method includes a step of filling the recesses of the thin line pattern with conductive ink by squeegeeing, which moves a doctor blade aligned in the X direction on the plate surface in the Y direction. The wiring board of the present invention is a wiring board including a fine line pattern formed on the surface of the board and made of cured conductive ink, wherein the fine line pattern includes fine lines having a line width of 10 μm or less, or the conductive ink includes conductor particles having a particle size of 0.5 μm or more. When two orthogonal directions on the board surface are the X direction and the Y direction, the wiring board includes a fine line pattern that passes through a point on the board surface that is different in position in the X direction but the same in position in the Y direction, at which three or more fine lines included in the fine line pattern converge at one intersection, and does not form another intersection at which three or more fine lines converge at the other point. The other fine line is connected to two other fine lines included in the fine line pattern on both sides of the extension direction that passes through the other point, and the two other fine lines have the same line width. The line width of the other fine line, between the two connection points that connect to the two other fine lines, is at least 1.5 times the smallest line width of the fine line included in the fine line pattern. [Effects of the Invention]

[0018] According to the wiring board production method of the present invention, it is possible to prevent the occurrence of smearing of the printing of the fine lines when gravure printing wiring including a fine line pattern, thereby preventing an increase in the resistance value of the fine lines or breakage due to smearing of the printing.

[0019] Furthermore, with the wiring board according to the present invention, by forming a fine line pattern by gravure printing in which squeegeeing is performed in a specific direction on the wiring board, it is possible to obtain a wiring board with excellent print quality in which the fine lines are free of faint printing. [Brief explanation of the drawings]

[0020] [Figure 1] 1A and 1B are diagrams for explaining an embodiment of a wiring board according to the present invention; [Figure 2] FIG. 2 is a diagram for explaining a modification of the embodiment shown in FIG. [Figure 3] FIG. 1 is a diagram showing an outline of the configuration of a touch panel as an example of a conventional configuration of a wiring board. [Figure 4]4A is a partially enlarged view showing a first sensor electrode of the touch panel shown in FIG. 3, and FIG. 4B is a partially enlarged view showing a second sensor electrode of the touch panel shown in FIG. [Figure 5] 4 is a partial enlarged view of a portion where a second sensor electrode and a lead-out wiring are connected in the touch panel shown in FIG. 3. [Figure 6] A photograph showing blurred printing on fine lines. [Figure 7] A is a diagram to explain the blurring that occurs in printing on thin lines, and B is an enlarged view of A. DETAILED DESCRIPTION OF THE INVENTION

[0021] First, we will explain the blurring of printing that occurs in fine lines when a fine line pattern is printed and formed by gravure printing or gravure offset printing.

[0022] FIG. 7A shows the second sensor electrode 70 in the photograph shown in FIG. 6 and the thin line pattern formed by the extension 71 formed on the edge of the second sensor electrode 70 in its original state (without blurring), and FIG. 7B shows an enlarged portion of FIG. 7A.

[0023] The line width W1 of the fine lines 72 constituting the fine line pattern is also shown in Figure 6, and is all 7 µm. Also, as shown in Figure 6, the length L1 of one side of the diamond-shaped unit cell of the mesh of the second sensor electrode 70 is 400 µm. Note that, as shown in Figure 7A, the squeegeeing direction of the doctor blade (arrow S) is defined as the Y direction, and the extension direction of the doctor blade is defined as the X direction, defining two orthogonal directions.

[0024] In Figure 7A, the areas marked with circles (◯) are areas where noticeable print blurring has occurred, which are circled in dotted lines in Figure 6. Intersection point a1 is the intersection point indicated by the arrow in Figure 6, and dashed dotted line d1 is a line that passes through intersection point a1 and is drawn parallel to the X direction.

[0025] From the intersection point a1, the dotted line d1, and the circled locations where the print smear has occurred, it can be seen that the print smear has occurred on a thin line that passes through a point located in the direction (X direction) that coincides with the extension direction of the doctor blade during squeegeeing when viewed from the intersection point a1, and does not form an intersection at that point.

[0026] This type of print blur occurs when the intersection of the gravure plate corresponding to intersection a1 is a1', and when the doctor blade passes through intersection a1' during the squeegeeing process, the doctor blade slightly sinks into the recess at intersection a1'.As the doctor blade passes through intersection a1', i.e., when this slight sinking occurs, the doctor blade penetrates deeper than usual into the recesses of other nearby thin wires that it passes at the same time, causing the conductive ink that should be filled into the recesses of the other nearby thin wires to be scraped out of the recesses, resulting in an inability to obtain the appropriate amount of ink filling at that location.

[0027] The line width of the recess in the X direction at the intersection a1' where the recesses of the thin lines converge is larger (wider) than the line width of the recess in the X direction of a single thin line, and such wide line width areas are formed with a finite length in the Y direction. In such areas, the doctor blade collapses, but because it is wide, the amount of ink filled is large and no smearing of the print occurs. On the other hand, in recesses with a small line width that are affected by the collapse of the doctor blade, i.e., recesses of single thin lines that do not form intersections, smearing of the print occurs.

[0028] Therefore, in this invention, the line width of the recessed thin lines that cause such fading in the print is designed and formed wider than usual, thereby obtaining an ink filling amount that will not cause fading in the print even if scraped off by a doctor blade.

[0029] Based on this idea, in a method for producing a wiring board including a fine line pattern formed by gravure printing using conductive ink, when the two orthogonal directions on the surface of a gravure plate on which recesses of the fine line pattern are formed are defined as the X direction and the Y direction, the gravure plate passes through another point on the surface that is different in position in the X direction but the same in position in the Y direction from one intersection where the recesses of the fine lines included in the fine line pattern converge, and at that other point, the recesses of the fine lines do not form another intersection where the recesses of the fine lines converge, and the line width of the recesses of the fine lines included in the fine line pattern is set to be 1.5 times or more the smallest line width of the recesses of the fine lines included in the fine line pattern, and the recesses of the fine line pattern are filled with conductive ink by squeegeeing, in which a doctor blade aligned in the X direction (extending in the X direction) on the plate surface is moved in the Y direction.

[0030] In a wiring board produced in this manner and having a fine-line pattern made of cured conductive ink formed on its surface, when the two orthogonal directions on the board surface are the X and Y directions, the line width of other fine lines in the fine-line pattern that do not form another intersection where the fine lines in the fine-line pattern converge at one point but pass through another point on the board surface that is located at a different position in the X direction but the same position in the Y direction and that does not form another intersection where the fine lines converge at another point has a line width that is 1.5 times or more the smallest line width of the fine lines in the fine-line pattern. In other words, particularly when a wiring board contains fine lines with a line width of 10 μm or less or when the conductive ink contains conductive particles with a particle size of 0.5 μm or more, it is impossible to print such a wiring board without using the gravure method. However, with a wiring board configured as described above, it is possible to produce an intended product by gravure printing using a squeegeeing process in which a doctor blade aligned in the X direction is moved in the Y direction.

[0031] Here, an intersection where thin lines converge at one point is an intersection where three or more thin lines converge at one point, a Y-shaped intersection is an intersection where three thin lines converge, and an X-shaped intersection is an intersection where four thin lines converge.Furthermore, thin lines that do not form an intersection at another point include cases where two thin lines converge from different directions at another point to form a bending point.

[0032] FIG. 7B is an enlarged view of a portion of FIG. 7A, and in addition to the dash-dotted line d1, dash-dotted lines d2 to d5 are added. These dash-dotted lines d2 to d5 are lines drawn parallel to the X direction, passing through intersections a2 to a5, which correspond to the intersections where the three or more thin lines described above converge. It can be seen that single thin lines (thin lines that do not form intersections) intersect with each of these dash-dotted lines d2 to d5. Therefore, in addition to the circle (◯) on the dash-dotted line d1 in FIG. 7B, the areas marked with a circle (◯) are areas where printing may be blurred, and the line widths of thin lines 73 to 76 including these areas are widened. In other words, the line widths of the recessed portions of the thin lines on the gravure plate corresponding to thin lines 73 to 76 are widened.

[0033] Figure 1 shows a wiring pattern in which the line widths of the thin lines 73 to 76 shown in Figure 7B and the thin lines 73' to 76' positioned in a mirror image of those shown in Figure 7A are wider, and parts corresponding to those in Figure 7A are given the same symbols.

[0034] In this example, the line width W2 of the thin lines 73 to 76 and 73' to 76' is set to 15 μm, which is 1.5 times or more the minimum line width of the thin lines included in the thin line pattern (W1=7 μm in this example).

[0035] By widening the line width of the thin wires 73 to 76 and 73' to 76' in this way, it is possible to prevent the occurrence of faint printing, and to prevent the thin wires from breaking or increasing in resistance due to faint printing.

[0036] Note that this invention does not apply to cases where, for example, the extension portion 71 has a periodic structure of a mesh of fine wires, and where there are no single fine wires intersecting on a line parallel to the X direction passing through the intersection of one fine wire, and only the intersection of the fine wires exists.

[0037] To prevent blurred printing, the line width of the thickened (widened) thin line should be at least 1.5 times the smallest line width of the thin lines included in the thin line pattern, but the upper limit should be 3 times, i.e., it is preferable to make it 3 times or less. This is to prevent localized deterioration of print quality in areas where excessively thick thin lines compared to the remaining thin lines are simultaneously gravure offset printed, which can cause rapid local swelling in the area of ​​the blanket that receives the ink from the thick thin lines.

[0038] When considering the effects of doctor blade depression, if there are multiple cell depressions that pass through a point in the extension direction (X direction) of the doctor blade when viewed from an intersection where three or more thin line depressions converge on one point on a gravure plate and do not form an intersection at that point, it is not necessary to widen the line width of all thin line depressions. In other words, it is not necessary to widen the line width of thin line depressions located in a position that is not affected by the doctor blade depression at the intersection. It is sufficient to widen at least the line width of the thin line depressions located within 200 μm in the X direction from the intersection.

[0039] Preferably, when viewed from the intersection where the recesses of the thin line converge, if there are multiple recesses of the thin line that pass through a point located in the extension direction (X direction) of the doctor blade and do not form an intersection at that point, the line width of the recess of the thin line that is the shortest distance from the intersection in the X direction should be widened.

[0040] Gravure plates used in gravure printing come in flat or rolled form. In the case of rolled gravure plates, the two orthogonal directions of the X and Y directions on the plate surface mean that the Y direction, as the direction of rotation, falls within a plane in space that is orthogonal to the X direction.

[0041] Furthermore, in a wiring board having a rectangular outer shape such as the touch panel shown in FIG. 3, the doctor blade generally squeezes in a direction parallel to one of the sides of the rectangle. Therefore, the wiring board of this invention has a rectangular outer shape with two sets of parallel opposing sides parallel to the X and Y directions, respectively.

[0042] Fig. 2 shows a modified example of the embodiment of the present invention shown in Fig. 1, in which the widths of the thin wires 75, 76 and 75', 76' are not widened, and only the widths of the thin wires 73, 74 and 73', 74' are widened. The reason for adopting such a configuration is that 1) In each V-shaped region where the thin wires 73 to 76 and 73' to 76' are located, even if the thin wires 75, 76 and 75', 76' inside the V shape are smeared, the widths of the thin wires 73, 74 and 73', 74' forming the outer shape of the V shape are expanded, so sufficient electrical connection performance is ensured. 2) Avoid localized deterioration of print quality due to the progression of localized swelling of the blanket caused by the dense formation of fine lines with enlarged line widths. This is for the following reasons. Depending on the configuration and function of the thin line pattern, it may be possible to adopt a configuration in which the line width of some (internal) thin lines is not increased in this way. [Explanation of symbols]

[0043] 10 transparent substrate 20 sensor area 21 Long side 22 Short side 30 first sensor electrode 31 island electrode 32 Connection section 33 Electrode row 35 dummy wiring 40 second sensor electrode 41 Island electrode 42 Connection part 43 Electrode row 44 Extension section 44a Large mesh section 44b Small mesh section 51, 52 Lead-out wiring 52a Connection part 53 Terminal section 54 Ground wiring 60 insulating layer 61 through hole 70 second sensor electrode 71 extension 72~76,73'~76' Thin line

Claims

1. A method for producing a wiring board including a fine line pattern formed by gravure printing using a conductive ink, comprising: When two orthogonal directions on the surface of the gravure plate on which the recesses of the thin line pattern are formed are defined as the X direction and the Y direction, the gravure plate has recesses of other thin lines included in the thin line pattern that pass through another point on the plate surface that is different in position in the X direction but the same in position in the Y direction as one intersection point where recesses of three or more thin lines included in the thin line pattern converge, and that do not form another intersection point where recesses of three or more thin lines converge at the other point; the recess of the other thin line is connected to recesses of two other thin lines included in the thin line pattern on extensions on both sides of the extension direction passing through the other point, the recesses of the two other thin lines have the same line width; a line width of the recessed portion of the other thin line is set to be 1.5 times or more the minimum line width of the recessed portion of the thin line included in the thin line pattern between two connection points respectively connecting to the recessed portions of the further two thin lines; a doctor blade aligned in the X direction on the printing plate surface and moved in the Y direction to fill the conductive ink into the recesses of the fine line pattern;

2. 2. The method for producing a wiring substrate according to claim 1, a line width of the recess of the other thin line being three times or less the minimum value;

3. 3. The method for producing a wiring board according to claim 1, A method for producing a wiring substrate, wherein the distance in the X direction between the one intersection point and the other intersection point is within 200 μm.

4. 4. The method for producing a wiring board according to claim 1, the gravure plate has a plurality of recesses of specific thin lines included in the thin line pattern, which pass through a specific point on the plate surface that is different in position in the X direction but the same in position in the Y direction with respect to the one intersection point, and which do not form another intersection point at which three or more recesses of the thin lines converge at the specific point; a wiring substrate production method characterized in that the other point is the closest of the plurality of specific points according to the recess of the specific thin line from the one intersection point, and the recess of the other thin line is the one of the plurality of recesses of the specific thin line that is shortest in the X direction from the one intersection point.

5. A wiring board including a fine line pattern made of hardened conductive ink formed on a board surface, The wiring board is such that the fine line pattern includes fine lines having a line width of 10 μm or less, or the conductive ink includes conductive particles having a particle size of 0.5 μm or more, When two orthogonal directions on the board surface are defined as an X direction and a Y direction, the wiring board has other thin lines included in the thin line pattern that pass through another point on the board surface that is different in position in the X direction but the same in position in the Y direction as one intersection where three or more thin lines included in the thin line pattern converge to one point, and that do not form another intersection where three or more thin lines converge to one point at the other point, the other thin line is connected to two other thin lines included in the thin line pattern on extensions on both sides of the extension direction passing through the other point, the two other thin lines have the same line width; A wiring board characterized in that the line width of the other thin line is 1.5 times or more the minimum line width of the thin line included in the thin line pattern between two connection points that connect to the two other thin lines.

6. 6. The wiring board according to claim 5, A wiring board characterized in that the line width of the other thin lines is three times or less the minimum value.

7. 7. The wiring board according to claim 5, A wiring board characterized in that the distance in the X direction between the one intersection point and the other intersection point is within 200 μm.

8. 8. The wiring board according to claim 5, the wiring board has a plurality of specific thin lines included in the thin line pattern, the specific thin lines passing through a specific point on the board surface that is different in position in the X direction but the same in position in the Y direction with respect to the one intersection point, and not forming another intersection point at which three or more thin lines converge at the specific point; The other point is the closest of the plurality of specific points according to the specific thin line to the one intersection point, and the other thin line is the one of the plurality of specific thin lines that is shortest in the X direction from the one intersection point.

9. 9. The wiring board according to claim 5, The wiring board has a rectangular outer shape with two sets of parallel opposing sides parallel to the X and Y directions, respectively.

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