JP2018154028A - Line pattern printing method and screen printing plate for line pattern printing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a line pattern printing method capable of suppressing generation of blotting, and a screen printing plate for line pattern printing.SOLUTION: The present invention relates to a method for printing a linear line pattern on a printed board by using a screen printing plate comprising: a metal foil with which a number of holes are formed in one direction; and resins which are disposed while being spaced in a direction across the one direction on a rear face of the metal foil and form openings together with the metal foil by opening central parts of a number of holes. A squeegee is moved in the one direction on a front face of the screen printing plate, such that the screen printing plate is pressed to the printed board and paste is discharged from the openings. The linear line pattern is then printed on the printed board, such that an average angle formed from the screen printing plate at a downstream side in a movement direction of the squeegee and the printed board is kept equal to or greater than a fixed value during the printing.SELECTED DRAWING: Figure 10

Description

  The present invention relates to a line pattern printing method and a line pattern printing screen plate.

  In the field of solar cells, in order to improve the photoelectric conversion efficiency, the development of thinning technology for reducing the light-shielding area of the finger electrode by forming the finger electrode thinly has become active.

  When forming the finger electrode of a solar cell, screen printing using a screen plate is performed. At present, a screen version using a wire mesh (# 360-φ16CL) is mainly used. According to the mass production technique of such a wire mesh, the width of the finger electrode to be printed is approximately 45 to 50 μm. New wire meshes are also being manufactured with the aim of further thinning. Specifically, there are next-generation wire meshes (# 380-φ14CL, # 430-φ13CL) in which the mesh count is increased, and knotless screens. The knotless screen does not provide a bias angle (bias angle = 0 °) to the wire mesh, and the wire intersection where the wires intersect with each other is not exposed to the opening for discharging the paste.

  For example, Patent Document 1 discloses a method of printing finger electrodes of a solar cell by off-contact screen printing.

JP 2013-28112 A

  On the other hand, the inventors of the present application have developed an original screen printing mesh in which an opening is provided in a metal foil, unlike a screen plate using a wire mesh, and have advanced the development of thinning technology.

  Here, when forming the finger electrode of a solar cell, it is desirable that the line pattern printed by screen printing is thin in the width direction and the width is as uniform as possible. On the other hand, depending on screen printing conditions, a phenomenon called “bleed” in which the length of the line pattern in the width direction partially expands may occur. Development of a technique capable of suppressing the occurrence of bleeding is required, including the configuration disclosed in Patent Document 1.

  Accordingly, an object of the present invention is to provide a line pattern printing method and a line pattern printing screen plate capable of suppressing the occurrence of bleeding in order to solve the above-described problems.

  In order to achieve the above object, a line pattern printing method according to an aspect of the present invention includes a metal foil in which a large number of holes are formed along one direction and a direction crossing the one direction on the back surface of the metal foil. A method of printing a linear line pattern on a substrate to be printed using a screen plate that is arranged at intervals and has a resin that opens a central portion of the plurality of holes and forms an opening with the metal foil. The squeegee is moved along the one direction on the surface of the screen plate so that the screen plate is pressed against the substrate to be printed and the paste is discharged from the opening to form a linear shape on the substrate to be printed. In the printing, the average angle formed by the screen plate and the substrate to be printed on the downstream side in the moving direction of the squeegee is maintained at a certain value or more. Characterized in that was.

  In addition, a line pattern printing method according to another aspect of the present invention uses a screen plate having a wire mesh and a resin that is arranged on the back surface of the wire mesh at an interval and that forms an opening together with the wire mesh. A method of printing a linear line pattern on a substrate to be printed, wherein the bias angle of the wire mesh is set to a value that does not expose an intersection where wires intersect with each other in the opening. By moving the squeegee along the direction in which the opening is formed on the surface of the substrate, the screen plate is pressed against the substrate to be printed to discharge the paste from the opening, and a linear line is formed on the substrate to be printed. The screen plate and the substrate to be printed are printed on the downstream side in the moving direction of the squeegee during printing. The average angle formed, characterized in that to keep a certain value or more.

Further, the screen pattern for line pattern printing according to one aspect of the present invention includes a metal foil in which a large number of holes are formed in one direction and a space in the direction intersecting the one direction on the surface of the metal foil. A screen plate for printing a linear line pattern on a substrate to be printed. The ribs of the metal foil between the openings and the openings that meet each other have a cross-sectional area per unit length along the direction in which the openings are formed of 4000 μm ² / mm or more.

    According to the line pattern printing method and the line pattern printing screen plate of the present invention, it is possible to suppress the occurrence of bleeding.

The fragmentary top view which shows the screen plate using the metal foil which concerns on embodiment AA sectional view in FIG. BB sectional view in FIG. Schematic for explaining a method of printing a line pattern on a substrate to be printed using a screen plate Partial plane portion showing a screen plate using a conventional wire mesh Figure showing an example of screen printing results Partial plan view showing a knotless screen A diagram that schematically shows the angle between the screen plate and the substrate to be printed Schematic showing changes in screen plate when squeegee moves from upstream to downstream Schematic diagram when screen plate is fixed to metal frame with large inner diameter Schematic diagram when screen plate is fixed to metal frame with small inner diameter The figure which shows the method of calculating the downstream angle which a screen plate and a to-be-printed substrate comprise The figure which shows the example which calculated the angle of the downstream which the screen plate and the to-be-printed substrate make The figure which shows the example which calculated the angle of the downstream which the screen plate and the to-be-printed substrate make The figure which shows the conditions and the result of Example 1 The figure which shows the conditions and the result of Example 2 Partial plan view showing a screen plate using metal foil

  According to the first aspect of the present invention, the metal foil in which a large number of holes are formed along one direction and the back surface of the metal foil are arranged at intervals in a direction intersecting the one direction, A method of printing a linear line pattern on a substrate to be printed using a screen plate having a resin that forms an opening together with the metal foil by opening a central portion of a hole, the surface of the screen plate By moving the squeegee along the one direction, the screen plate is pressed against the substrate to be printed, the paste is discharged from the opening, and a linear line pattern is printed on the substrate to be printed. A line pattern printing method characterized in that an average angle formed by the screen plate and the substrate to be printed on the downstream side in the moving direction of the squeegee is maintained at a certain value or more. Subjected to. In this way, by keeping the average angle at a certain value or more, bleeding of the line pattern can be suppressed, which can contribute to thinning of the line pattern.

  According to the second aspect of the present invention, using a screen plate having a wire mesh and a resin that is arranged at an interval on the back surface of the wire mesh and that forms an opening together with the wire mesh, A method of printing a linear line pattern, wherein a bias angle of the wire mesh is set to an angle at which a crossing portion where wires cross each other is not exposed to the opening, and the opening on the surface of the screen plate By moving the squeegee along the direction in which the portion is formed, the screen plate is pressed against the substrate to be printed to discharge paste from the opening, and a linear line pattern is printed on the substrate to be printed. At the time of printing, an average angle formed by the screen plate and the substrate to be printed on the downstream side in the moving direction of the squeegee is a certain value or more. Characterized in that to keep, to provide a line pattern printing method. In this way, by keeping the average angle at a certain value or more, bleeding of the line pattern can be suppressed, which can contribute to thinning of the line pattern.

  According to a third aspect of the present invention, there is provided the line pattern printing method according to the first aspect or the second aspect, wherein the average angle is 0.7 degrees or more. In this way, by keeping the average angle at 0.7 degrees or more, it is possible to further suppress line pattern bleeding.

  According to a fourth aspect of the present invention, the screen plate is fixed on the upstream side and the downstream side in the moving direction of the squeegee, and the distance is set to 320 mm or less. A line pattern printing method according to any one of the aspects is provided. According to such a method, the downstream angle formed by the screen plate and the substrate to be printed is larger than when the distance is set to exceed 320 mm. Thereby, the average angle on the downstream side formed by the screen plate and the substrate to be printed during printing can be increased, and bleeding of the line pattern can be further suppressed.

  According to a fifth aspect of the present invention, the line according to any one of the first to fourth aspects is characterized in that an interval between the substrate to be printed and the screen plate is set to 1.6 mm or more. A pattern printing method is provided. According to such a method, the downstream angle formed by the screen plate and the substrate to be printed can be increased as compared with the case where the distance is set to be smaller than 1.6 mm. Thereby, the average angle on the downstream side formed by the screen plate and the substrate to be printed during printing can be increased, and bleeding of the line pattern can be further suppressed.

  According to a sixth aspect of the present invention, there is provided the line pattern printing method according to any one of the first to fifth aspects, wherein the line pattern is used as a finger electrode of a solar cell. According to such a method, since the finger electrode of a solar cell can be formed thinly, the conversion efficiency of the solar cell can be improved.

According to the seventh aspect of the present invention, the metal foil in which a large number of holes are formed along one direction and the back surface of the metal foil are arranged at intervals in a direction intersecting the one direction, A resin for forming an opening together with the metal foil by opening a central portion of the hole, and a screen plate for printing a linear line pattern on a substrate to be printed, the adjacent opening and the The rib of the metal foil between the openings has a cross-sectional area per unit length along the direction in which the openings are formed of 4000 μm ² / mm or more. provide. By setting the cross-sectional area per unit length of the rib of the metal foil to such a value or more, the strength of the metal foil can be improved. When printing is performed so that the average angle on the downstream side formed by the screen plate and the substrate to be printed is maintained at a certain value or more, it is easy to apply a load to the metal foil.In this way, by improving the strength of the metal foil, Breaking of the metal foil can be suppressed.

  According to an eighth aspect of the present invention, there is provided the screen pattern for line pattern printing according to the seventh aspect, wherein the line pattern is a finger electrode of a solar cell. According to such a configuration, the printing is performed such that the average angle on the downstream side formed by the screen plate and the substrate to be printed is maintained at a certain value or more, so that the finger electrode of the solar cell is thinly formed while suppressing bleeding. Therefore, the conversion efficiency of the solar cell can be improved.

  Embodiments according to the present invention will be described below in detail with reference to the drawings.

(Embodiment)
1, 2A and 2B are views showing a screen plate 2 according to the present embodiment. FIG. 1 is a plan view showing a part of the screen plate 2. 2A is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 2B is a cross-sectional view taken along the line BB in FIG.

  As shown in FIGS. 1, 2 </ b> A, and 2 </ b> B, the screen plate 2 includes a metal foil 4 and a resin 6.

  The metal foil 4 is a metal foil mesh formed of a metal such as SUS, Ni, Ni alloy. A large number of holes 8 are formed in the metal foil 4 along the X direction. A rib 4 a is formed between the adjacent holes 8 in the metal foil 4. As shown in FIGS. 2A and 2B, the rib 4a may have a tapered cross section whose width decreases from the front surface to the back surface.

  The metal foil 4 may be produced by an arbitrary method such as an electroforming method (electroforming method), an etching method, a laser processing method, or a machining method.

  The resin 6 is a resin provided on the back side of the metal foil 4. As shown in FIG. 1, the resin 6 is arranged at an interval in the Y direction that intersects the X direction. In the example of FIG. 1, the Y direction is orthogonal to the X direction, but is not limited to this. The resin 6 opens the central portion of the hole 8 of the metal foil 4 and forms the opening 10 together with the metal foil 4. Although resin is used in the present embodiment, a member of any material may be used as long as it is a member (opening forming member) that forms the opening 10 together with the metal foil 4.

  A method of forming a linear line pattern on a substrate to be printed using such a screen plate 2 will be described with reference to FIG.

  As shown in FIG. 3, the screen plate 2 is fixed in a substantially horizontal direction by a metal frame (aluminum frame) 14. The screen plate 2 is fixed to the metal frame 14 at the upstream end 22a and the downstream end 22b. A distance D from the upstream end 22 a to the downstream end 22 b is the same as the inner diameter of the metal frame 14.

  Below the screen plate 2, the substrate 12 to be printed is arranged with an interval. The printed substrate 12 is fixed so as to be substantially parallel to the screen plate 2. Although not shown, an interval adjusting mechanism is provided for adjusting the interval (clearance C) in the vertical direction between the screen plate 2 and the substrate 12 to be printed, and the clearance C can be adjusted.

  In such a configuration, the squeegee 13 is moved along the X direction on the surface of the screen plate 2. Thereby, the screen plate 2 is pressed against the substrate 12 to be printed, and the paste 16 is discharged from the opening 10 described above, so that a linear line pattern can be formed on the substrate 12 to be printed.

  The screen plate 2 of the present embodiment described above is a screen plate for printing finger electrodes of solar cells using the metal foil 4, and the inventors of the present application use the metal foil 4 used for such a screen plate 2. Have been developing. On the other hand, a screen plate 100 using a conventional wire mesh is shown in FIG. As shown in FIG. 4, the wire mesh 104 is exposed from between the resins 102 provided at intervals. In the wire mesh 104, an intersection (wire intersection, knot) 106 where the wires intersect is exposed.

  Unlike the wire mesh 104 shown in FIG. 4, the screen plate 2 using the metal foil 4 shown in FIG. 1 has one feature that the opening 10 does not have a wire intersection. By not having wire intersections, the regions of the openings 10 can be formed regularly. Thereby, there is little clogging of the paste 16 in the opening part 10, and the permeability | transmittance of the paste 16 becomes favorable. For this reason, there are few disconnections, the leveling is good (the unevenness is small), and the finger electrode can be printed.

  On the other hand, when the paste 16 is excessively discharged, the amount of paste transferred to the substrate 12 to be printed may increase. As a result, the paste 16 spreads in the width direction, and bleeding may occur. When bleeding occurs, the width of the finger electrode increases and the conversion efficiency of the solar cell decreases.

  FIG. 5 shows an example of the result of forming the finger electrode line pattern using the screen plate 2 shown in FIG. In the example shown in FIG. 5, the finger electrode line pattern L1 in which bleeding occurs is shown on the left side, and the finger electrode line pattern L2 in which bleeding hardly occurs is shown on the right side. As shown in FIG. 5, in the left line pattern L1, it is understood that “bleeding” spreading in the width direction Y1 is partially generated. On the other hand, in the line pattern L2 on the right side, it can be seen that the length in the width direction Y2 is substantially constant, and blurring hardly occurs.

  The blur generated in the line pattern L1 shown on the left side of FIG. 5 occurs regularly and at regular intervals. The inventors of the present application have confirmed that these bleedings occur at positions corresponding to the openings 10. On the other hand, bleeding is suppressed at positions corresponding to the ribs 4 a of the metal foil 4. As a result, a line pattern L1 in which the length in the width direction Y1 is thick and narrow is periodically repeated as shown on the left side of FIG. 5 is formed. On the other hand, a line pattern L2 with less bleeding as shown on the right side of FIG.

  The phenomenon shown in FIG. 5 is considered to occur on the same principle even in a knotless screen in which the wire intersection is not exposed in the opening as in the screen plate 2 in FIG. An example of a knotless screen is shown in FIG. In the knotless screen 200 shown in FIG. 6, the wire mesh 204 is exposed from between the resins 202 arranged at intervals, but the wire intersection 206 is not exposed to the opening. That is, the bias angle of the wire mesh 204 is set to an angle (for example, within ± 1.0 °) that does not expose the wire intersection 206 where the wires intersect with each other in the opening. Such a knotless screen 200 is also an object of the present invention.

  Under such circumstances, as a result of repeated printing tests under various conditions, the screen plate 2 using the metal frame 14 having a small inner diameter is more line-shaped than the screen plate 2 using the metal frame 14 having a large inner diameter. It was found that the bleeding of the pattern can be reduced. As specific dimensions of the inner diameter of the metal frame 14 here, the metal frame 14 having a larger inner diameter is 390 mm (outer diameter is 450 mm), and the metal frame 14 having a smaller inner diameter is 300 mm (outer diameter is 355 mm).

  In order to understand this phenomenon, the present inventors considered the following model.

  In FIG. 7, when the screen plate 2a is fixed to the metal frame 14a having an inner diameter of 390 mm and when the screen plate 2b is fixed to the metal frame 14b having an inner diameter of 300 mm, the screen plates 2a and 2b and the printing substrate 12 are It is a figure which represents typically the formed angle.

  As shown in FIG. 7, among the angles formed by the screen plate 2a and the substrate 12 to be printed, the upstream angle in the moving direction (X direction) of the squeegee 13 is α1, and the downstream angle is α2. Similarly, among the angles formed by the screen plate 2b and the substrate 12 to be printed, the upstream angle in the moving direction of the squeegee 13 is β1, and the downstream angle is β2.

  As shown in FIG. 7, it can be seen that α1 <β1 and α2 <β2. That is, it can be seen that the metal frame 14b having a smaller inner diameter has a larger angle between the upstream side and the downstream side of the metal frame 14b having a smaller inner diameter even at the same position on the substrate 12 to be printed. Accordingly, the phenomenon shown in FIG. 5 in which bleeding is suppressed is that the angles β1 and β2 formed by the screen plate 2b and the printing substrate 12 are larger than the angles α1 and α2 formed by the screen plate 2a and the printing substrate 12. It is thought to be caused by

  In FIG. 8, the schematic diagram showing the change of the screen plate 2 when the squeegee 13 moves from upstream to downstream is shown. In FIG. 8, the screen plate 2 at the initial position (print start point) of the squeegee 13 is indicated by a dotted line, and the screen plate 2 at the final position (print end point) of the squeegee 13 is indicated by a dashed line.

  Here, the inventors of the present application paid attention to the change in the downstream angle formed by the screen plate 2 and the substrate 12 to be printed. As the squeegee 13 moves downstream, the downstream angle formed by the screen plate 2 and the substrate 12 to be printed increases (θ1 → θ2). On the other hand, the upstream angle formed by the screen plate 2 and the substrate 12 to be printed becomes smaller as the squeegee 13 moves downstream (θ3 → θ4).

  In general, as the squeegee 13 moves downstream, the distance between the screen plate 2 on the upstream side after the squeegee 13 passes and the substrate 12 to be printed becomes smaller (the angle becomes smaller), and the separation of the plate becomes worse. . “The plate separation becomes worse” means that the screen plate 2 becomes difficult to separate from the substrate 12 to be printed. If the plate separation is deteriorated, printing unevenness and bleeding are caused. Therefore, an off-contact function for forcibly lifting the upstream side of the screen plate 2 after the squeegee 13 passes is used to promote plate separation.

  However, in the screen plate 2 using the metal foil 4 by the present inventors, as shown in FIG. 7, the angle on the downstream side of the screen plate 2 and the substrate to be printed 12 is increased (the upstream angle is reversed). The occurrence of bleeding can be suppressed.

  The inventors consider this difference as follows.

  Compared to the conventional screen plate using a wire mesh (FIG. 4), the screen plate 2 using the metal foil 4 does not expose the mesh intersection in the opening 10 as described above. high. Therefore, it is presumed that it is insufficient to suppress bleeding of the line pattern only by promoting the plate separation after the squeegee 13 passes by the off-contact function. From this, it is effective to control the angle formed between the screen plate 2 and the printed substrate 12 downstream from the stage where the paste 16 is pushed by the squeegee 13 and passes through the opening 10 of the screen plate 2. The inventors have newly found out.

  The principle that the bleeding of the line pattern can be suppressed by controlling the angle formed between the screen plate 2 and the downstream side of the printing substrate 12 will be described with reference to FIGS. The principle described below is a hypothetical model and is not bound by such a specific principle.

  9 shows a case where the screen plate 2a is fixed to the metal frame 14a having a large inner diameter shown in FIG. 7, that is, a case where the angle α2 formed between the screen plate 2a and the downstream side of the printing substrate 12 is small. On the other hand, FIG. 10 shows a case where the screen plate 2b is fixed to the metal frame 14b having a small inner diameter shown in FIG. 7, that is, a case where the angle β2 formed between the screen plate 2b and the printed substrate 12 is large.

  As shown in FIG. 9, in the screen plate 2a, since there is no mesh intersection in the opening 10a, a large amount of paste 16 pushed by the squeegee 13 tries to pass through the opening 10a (arrow R1). When the angle α2 formed between the screen plate 2a and the downstream side of the printed substrate 12 is small, the amount of the paste 16 rebounded by the rib 4a of the metal foil 4 increases (arrow R2), and the paste 16 tends to stay in the opening 10a. A situation occurs. Further, it is difficult for air to escape on the downstream side of the screen plate 2a in contact with the substrate 12 to be printed, and it is conceivable that an air pocket H is generated in the vicinity immediately below the rib 4a. For this reason, the paste 16 tends to stay between the ribs 4a even though a large amount of the paste 16 has entered from the opening 10a. It is considered to occur at a position corresponding to.

  On the other hand, as shown in FIG. 10, when the angle formed between the screen plate 2b and the downstream side of the printing substrate 12 is set large, the inclination of the rib 4a of the metal foil 4 changes. For this reason, the direction in which the paste 16 bounced back by the rib 4a is directed forward (upstream) is easier than the case shown in FIG. 9 (arrow R3). Thereby, the amount of the paste 16 staying in the opening 10b is reduced. Further, by setting a large angle between the screen plate 2b and the downstream side of the substrate 12 to be printed, an air escape path can be secured, and the air reservoir H shown in FIG. Thereby, the paste 16 that has entered the opening 10b is likely to travel forward. As a result, it is considered that the amount of the paste 16 staying between the ribs 4a can be reduced, and bleeding spreading in the width direction perpendicular to the flow direction of the paste 16 can be suppressed.

  Conventionally, it is well known to suppress bleeding by an off-contact function that promotes plate separation on the upstream side through which the squeegee 13 has passed, and screen printers having an off-contact function have been put into practical use and sold.

  On the other hand, the method conceived by the inventors of the present application is completely different from the purpose of the off-contact function of promoting plate separation after the squeegee 13 passes. Specifically, when the paste 16 is pushed into the opening 10 of the screen plate 2 by the squeegee 13, the downstream angle formed by the screen plate 2 and the substrate 12 to be printed is controlled, so that the line pattern of the finger electrode is controlled. It reduces bleeding. Thus, it is completely different from the known off-contact function.

  A method of controlling the “squeegee angle” (the angle formed by the squeegee 13 and the substrate 12 to be printed, also referred to as “attack angle”), which is the inclination angle of the squeegee 13, can be considered. However, the attack angle is an angle formed by the squeegee 13 and the substrate 12 to be printed. The inventors of the present application newly found that the “downstream angle formed by the screen plate 2 and the substrate 12 to be printed” is effective in suppressing bleeding, unlike the method of controlling the attack angle.

  Next, a specific angle control method for realizing the present invention will be described with reference to FIG.

  FIG. 11 is a schematic diagram for obtaining the downstream angle θ formed by the screen plate 2 and the substrate 12 to be printed. In the example shown in FIG. 11, the distance between the screen plate 2 and the substrate 12 to be printed is C, and the inner diameter of the metal frame 14 is D, as in FIG. Here, if the distance X from the upstream end 2a of the screen plate 2 to the position touched by the squeegee 13 and contacting the substrate 12 to be printed is determined, the angle θ can be calculated from the following equation 1.

(Formula 1)
θ = tan ⁻¹ {C / (D−X)}

  An example in which the downstream angle θ between the screen plate 2 and the printing substrate 12 is calculated using Equation 1 is shown in FIGS. 12 and 13 show the results of calculating the angle θ using Equation 1 and plotting representative points under various conditions. 12 and 13, the horizontal axis represents the position of the squeegee 13 (the downstream end of the printed substrate 12 is 0 mm), and the vertical axis represents the downstream angle formed by the screen plate 2 and the printed substrate 12. represents θ.

  FIG. 12 shows the calculation results of Condition 1 and Condition 2. Condition 1 is an example in which the clearance C is set to 1.5 mm using a metal frame 14 having an inner diameter of 300 mm (D = 300 mm). Condition 2 is an example in which the clearance C is set to 1.5 mm using a metal frame 14 having an inner diameter of 390 mm (D = 390 mm). In both condition 1 and condition 2, the length of the printed substrate 12 in the X direction is 157 mm.

  As shown in FIG. 12, it can be seen that in both conditions 1 and 2, the angle θ increases as the squeegee 13 moves from upstream to downstream. In addition, in the condition 1 using the metal frame 14 having a small inner diameter, the angle θ increases as the squeegee 13 moves from upstream to downstream than in the condition 2 using the metal frame 14 having a small inner diameter. I understand that. In condition 1, the average angle θ was 0.66 °, and in condition 2, the average angle θ was 0.48 °. From this, it can be seen that even with the same clearance C, printing can be performed with the angle θ kept large by using the metal frame 14 having a smaller inner diameter.

  FIG. 13 shows the calculation results of Condition 3 and Condition 4. Condition 3 is an example in which the clearance C is set to 1.6 mm using a metal frame 14 having an inner diameter of 300 mm (D = 300 mm). Condition 4 is an example in which a clearance C is set to 2.0 mm using a metal frame 14 having an inner diameter of 390 mm (D = 390 mm). In both conditions 3 and 4, as in conditions 1 and 2, the length of the substrate 12 to be printed in the X direction is 157 mm.

  In condition 3 shown in FIG. 13, the average angle θ was 0.71 °, and in condition 4, the average angle θ was 0.64 °.

  Of conditions 1-4 shown in FIGS. 12 and 13, the average angle θ of condition 3 is 0.7 degrees or more. As will be described later with reference to FIG. 14, the inventors of the present application keep the average angle of the downstream angle θ formed by the screen plate 2 and the substrate 12 to be printed above a certain value, particularly 0.7 ° or more. The present inventors have found that there is a remarkable effect in suppressing the bleeding of the line pattern of the finger electrode. Such knowledge about the average angle is considered to be similarly applicable to the knotless screen 200 described above.

  When the screen plate 2 is fixed using the metal frame 14 having an inner diameter of 300 mm as in the condition 3 shown in FIG. 12, when the clearance C is printed at 1.6 mm, the average angle θ during printing is 0.71. Thus, the printing conditions of the present invention can be realized. However, when the screen plate 2 is fixed using the metal frame 14 having an inner diameter of 390 mm, even if the clearance C is increased to 2.0 mm, the average angle increases only to 0.64 °. As the clearance C increases, the average angle θ can be increased, but the load on the screen plate 2 (particularly the metal foil 4) pushed by the squeegee 13 increases. For this reason, in order to suppress breakage of the metal foil 4 and the like, it is preferable to set the clearance C to 2.0 mm or less. (1) Set the clearance C to 2.0 mm or less, (2) Set the average angle of the angle θ to 0.7 ° or more, and (3) Stabilize the printing method of the present invention at the mass production site. Therefore, it is preferable to set the inner diameter of the metal frame 14 to 300 mm, particularly 320 mm or less.

  The upper limit value of the average angle θ may be set to 2.2 °, for example, in consideration of the load applied to the metal foil 4. In order to set the average angle of the angle θ to 2.2 °, for example, when the length of the substrate to be printed is 157 mm, the inner diameter D of the metal frame 14 may be 300 mm and the clearance C may be 5 mm.

  12 and 13, representative points are plotted from the result of calculating the angle θ using Equation 1, and the average angle of the angle θ is obtained. However, the present invention is not limited to such a case. For example, a value obtained by integrating Equation 1 may be obtained as the average angle of the angle θ.

  In order to control the average angle of the angle θ, the clearance C or the inner diameter D of the metal frame 14 may be adjusted as can be seen from Equation 1. The clearance C can be adjusted by, for example, the above-described interval adjusting mechanism (not shown). For example, the inner diameter D of the metal frame 14 can be adjusted by properly using the type of the metal frame 14 to be used.

Example 1
Next, FIG. 14 shows the relationship between the average angle θ and the spread width of the finger electrode for the results of screen printing under various conditions. In FIG. 14, the horizontal axis represents the average angle of the downstream angle θ formed by the screen plate 2 and the substrate 12 to be printed, and the vertical axis represents the spread width of the printed finger electrode. “Bleeding width” is (finger electrode width) − (width of opening 10) measured with an optical microscope. It can be said that the smaller the value of the bleeding width, the less the bleeding.

  FIG. 14 shows the experimental results of Condition 5, Condition 6, and Condition 7. As a condition common to condition 5 and condition 7, the metal foil 4 uses a stainless steel foil (SUS301). In conditions 5 and 6, the squeegee angle is set to 60 °, and in condition 7, the squeegee angle is set to 70 °. Condition 5 uses a metal frame 14 with an inner diameter of 300 mm and sets the clearance C to 1.4 mm. Condition 6 uses a metal frame 14 having an inner diameter of 300 mm and sets the clearance C to 1.7 mm. Condition 7 uses a metal frame 14 having an inner diameter of 390 mm and sets the clearance C to 2.0 mm.

  Regarding condition 5, the results of three patterns with different thicknesses of the screen plate 2 are represented. The condition 6 represents the results of three patterns with different widths of the opening 10, and the condition 7 represents the results of four patterns with different widths of the opening 10.

  As shown in FIG. 14, the average angle of the downstream angle θ formed by the screen plate 2 and the substrate 12 to be printed is about 0.58 ° for the condition 5 and about 0.71 ° for the condition 6. In the case of 7, it is about 0.62 °.

  As can be seen from the results of FIG. 14, when the average angle of the downstream angle θ formed by the screen plate 2 and the printing substrate 12 is less than 0.7 ° as in the conditions 5 and 7, the spread width is 16 to 35 μm. It is a large value. On the other hand, as in Condition 6, when the average angle was 0.7 ° or more, the spread width could be greatly reduced to 8 to 15 μm.

  From the results shown in FIG. 14, the finger electrode line is maintained by keeping the average angle formed by the screen plate 2 and the substrate 12 to be printed at the downstream side in the moving direction of the squeegee 13 at a certain value or more, particularly 0.7 ° or more. It can be seen that the bleeding of the pattern can be suppressed. Thereby, it can contribute to thinning of a line pattern.

(Example 2)
Next, the inventors of the present invention relate to a line pattern printing method for performing printing while keeping the average angle on the downstream side formed by the screen plate 2 and the substrate to be printed 12 at a certain value or more. In order to find out the characteristics of the metal foil 4, an experiment shown in FIG.

  FIG. 15 shows a result of whether or not the metal foil 4 is broken when the above-described line pattern printing method is performed while changing the specification of the metal foil 4. Specifically, the strength of the metal foil 4 when the screen plate 2 using the stainless steel foil (SUS301) metal foil 4 was fixed to the metal frame 14 having an inner diameter of 300 mm and screen-printed was examined.

  In FIG. 15, “mesh specification” represents the pitch a of the openings 10 / the width b of the openings 10 (FIG. 16). For example, “80/50” in the “mesh specification” column means that the pitch a of the openings 10 is 80 μm and the width b of the openings 10 is 50 μm. The “mesh thickness” represents the thickness of the metal foil 4 (the thickness of the rib 4a) (μm).

In FIG. 15, “cross-sectional area per unit length” is obtained by calculating the cross-sectional area per unit length in the X direction of the rib 4 a under each condition. The cross-sectional area is determined by cutting the metal foil 4 along the cutting plane B (FIG. 16), measuring the cross-sectional area of each rib 4a by SEM observation, and measuring the ribs per mm from the pitch a of the openings 10. The cross-sectional area of 4a was calculated (truncated to 100 μm ² units).

When the “mesh specifications” were 80/60 and 85/65 (mesh thickness: 20 μm), the metal foil 4 was broken during the printing test with the clearance C being 2 mm (evaluation was x). The “cross-sectional area per unit length” under these conditions was all less than 4000 μm ² / mm.

On the other hand, in the case of other conditions, the “cross-sectional area per unit length” was 4000 μm ² / mm or more, and the metal foil 4 did not break during the printing test with the clearance C being 2 mm (evaluation). Is ○).

From the result shown in FIG. 15, even when the above-described line pattern printing method of the present invention is performed by setting the cross-sectional area per unit length along the X direction with respect to the rib 4 a to 4000 μm ² / mm or more, the metal foil 4 No breakage occurs. That is, by setting such a cross-sectional area, the metal foil 4 and the screen plate 2 suitable for the line pattern printing method of the present invention can be obtained. In particular, when printing is performed using a metal frame 14 having an inner diameter of 300 mm and a clearance C of 2 mm or less and an average angle of 0.7 ° or more, the cross-sectional area of the rib 4a is 4,000 μm ² / mm or more. It is preferable that

  Next, the aspect ratio of the opening 10 in the screen plate 2 will be described. The aspect ratio of the opening 10 is the thickness of the screen plate 2 / the width b of the opening 10. The aspect ratio of the opening 10 may be set to 1.4 or less. By setting the aspect ratio of the opening 10 to 1.4 or less, the resistance of the paste 16 that passes through the opening 10 can be set low. Thereby, in the screen plate in which the mesh intersection is not exposed in the opening 10 as in the screen plate 2 using the metal foil 4, the discharge property of the paste 16 is stable, and the printed line pattern does not rub or break. Can be.

  Finally, the opening width of the opening 10 in the screen plate 2 will be described. The opening width c of the opening 10 is the length in the width direction of the opening 10 determined by the interval between the resins 6 as shown in FIG. The opening width c may be set to 15 μm or more and 100 μm or less. By setting the opening width c to 100 μm or less, the width of the line pattern can be reduced. As a result, it is possible to avoid a situation where the line pattern itself becomes thick and the influence of bleeding does not become a problem. On the other hand, by setting the opening width c to 15 μm or more, it is possible to suppress deterioration of the paste dischargeability due to the resistance of the inner wall surface of the resin 6. Thereby, it is possible to avoid that the problems of rubbing, leveling (level difference), and disconnection become dominant as problems other than bleeding.

  The present invention has been described with reference to the above-described embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications may be made to the above-described embodiments based on the description of the scope of claims. Good. For example, in the embodiment, the case where the finger electrode of the solar cell is formed as the line pattern has been described, but the present invention is not limited to such a case. As long as a line pattern is printed by applying a paste on an arbitrary object, it can be applied to an arbitrary line pattern printing method and a screen plate therefor.

  In the embodiment, the case where the average angle formed by the screen plate 2 and the substrate 12 to be printed is controlled to 0.7 degrees or more is described. However, the present invention is not limited to such a case. The average angle may be set to a value that can suppress bleeding of the line pattern according to various conditions.

  It is to be noted that, by appropriately combining arbitrary embodiments of the various embodiments described above, the effects possessed by them can be produced.

  Although the present disclosure has been fully described in connection with preferred embodiments with reference to the accompanying drawings, various variations and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present disclosure as set forth in the appended claims. In addition, combinations of elements and changes in the order in each embodiment can be realized without departing from the scope and spirit of the present disclosure.

  The present invention is applicable to any line pattern printing method and screen pattern printing screen plate.

2, 2a, 2b Screen plate 4 Metal foil (stainless steel foil)
4a Rib 6 Resin (opening forming member)
8 hole 10 opening 12 printed substrate 13 squeegee 14 metal frame (aluminum frame)
22a Upstream end 22b Downstream end 100 Screen plate 102 Resin 104 Wire mesh 106 Intersection (wire intersection)
200 knotless screen 202 resin 204 wire mesh 206 intersection (wire intersection)
C clearance D inner diameter a of metal frame a pitch of opening b length of opening c opening width of opening

Claims (8)

A metal foil in which a large number of holes are formed along one direction, and a back surface of the metal foil, the metal foil is disposed at intervals in a direction intersecting the one direction, and the central portion of the plurality of holes is opened to form the metal A method of printing a linear line pattern on a substrate to be printed using a screen plate having a member that forms an opening together with a foil,
By moving the squeegee along the one direction on the surface of the screen plate, the screen plate is pressed against the substrate to be printed and the paste is discharged from the opening, and a linear line pattern is formed on the substrate to be printed. Print and
A line pattern printing method, wherein an average angle formed by the screen plate and the substrate to be printed on the downstream side in the moving direction of the squeegee is maintained at a certain value or more during the printing. A method of printing a linear line pattern on a substrate to be printed, using a screen plate having a wire mesh and a member which is arranged at an interval on the back surface of the wire mesh and forms an opening together with the wire mesh. There,
The bias angle of the wire mesh is set to an angle that does not expose the intersection where the wires intersect with each other in the opening,
By moving a squeegee along the direction in which the opening is formed on the surface of the screen plate, the screen plate is pressed against the substrate to be printed to discharge the paste from the opening, and the line is applied to the substrate to be printed. Printed line pattern
A line pattern printing method, wherein an average angle formed by the screen plate and the substrate to be printed on the downstream side in the moving direction of the squeegee is maintained at a certain value or more during the printing.   The line pattern printing method according to claim 1, wherein the average angle is 0.7 degrees or more.   The line pattern printing according to any one of claims 1 to 3, wherein the screen plate is fixed on the upstream side and the downstream side in the moving direction of the squeegee and the distance is set to 320 mm or less. Method.   The line pattern printing method according to claim 1, wherein an interval between the substrate to be printed and the screen plate is set to 1.6 mm or more.   The line pattern printing method according to any one of claims 1 to 5, wherein the line pattern is used as a finger electrode of a solar cell. A metal foil in which a large number of holes are formed along one direction, and a back surface of the metal foil, the metal foil is disposed at intervals in a direction intersecting the one direction, and the central portion of the plurality of holes is opened to form the metal A member for forming an opening together with the foil, and a screen plate for printing a linear line pattern on the substrate to be printed,
The rib of the metal foil between the adjacent openings and the openings has a cross-sectional area per unit length along the direction in which the openings are formed of 4000 μm ² / mm or more, Screen version for line pattern printing.   The screen pattern for line pattern printing according to claim 7, wherein the line pattern is a finger electrode of a solar cell.

Images