JP2019181708A - Screen printing method and screen printing device - Google Patents

Abstract

To realize a screen printing method for largely reducing and stabilizing a variation in a snap-off angle and a clearance in a printing surface when moving a squeegee.SOLUTION: In a screen printing method, when a squeegee presses-moves a screen printing plate, a clearance between a printed matter and the screen printing plate just under the squeegee is maintained always constant, and a state of positioning the press-movement starting side edge of the squeegee of the screen printing plate higher than the press-movement finish side edge of the squeegee of the screen printing plate is maintained, and both the press-movement stating side edge of the squeegee of the screen printing plate and the press-movement finish side edge of the squeegee of the screen printing plate are interlocked with the press-movement of the squeegee, and are moved upward.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a screen printing method and a screen printing apparatus in which fluctuations in the plate separation angle and clearance are greatly reduced and stabilized.

  The screen printing method (also referred to as thick film printing method) is a screen plate or metal mask (hereinafter referred to as a screen plate) in which an arbitrary pattern is formed with a photosensitive resin or the like on a base made of a mesh sheet of metal or polymer compound fiber. Generically). After mounting ink or paste on the screen plate, a workpiece (printed material) placed on the lower side of the screen plate using a blade squeegee (also simply referred to as squeegee) formed of rubber, plastic, metal or the like On the other hand, an arbitrary pattern or the like formed as described above is pressed and transferred.

  Since such a screen printing method can realize pattern formation in a large area at a relatively low cost, its application has further expanded. However, when the distance (clearance) between the screen plate and the printing material is uniform within the printing surface and the plate size is large, one end of the screen plate (pressing start position of the squeegee stroke) and the other end (squeegee) The so-called “plate separation angle” changes to a level that cannot be ignored. Further, in connection with this, it is known that the delay in separation of the printing plate increases with the progress of the squeegee stroke.

  A single high-quality printed material is required to be able to be printed in the same conditions under the same conditions from the beginning to the end, and if the squeegee pressing start position and the pressing end position are different, the same in-plane printed material The printing conditions are different at the beginning and end of the. That is, when the squeegee moves while printing a pattern on the screen plate, the angle formed by the part of the screen plate after printing is separated from the printing material (plate separation angle) gradually decreases as the squeegee moves. Occurs.

  Furthermore, when the viscosity of the ink or paste to be used is large, a phenomenon in which the separation between the printing medium and the screen plate worsens, that is, the plate separation delay occurs, particularly near the squeegee stroke end position where the plate separation angle is small. It is known. Due to such a delay in plate separation, unevenness in film thickness, unevenness in line width, unevenness in printing pressure, and the like occur, and this has been a problem particularly in high quality, high accuracy, and large area printing.

  According to the following Patent Document 1, according to the conventional method for improving the plate separation property, the clearance increases as the plate is separated from the work even though the clearance at the start of printing can be reduced. In addition to being completely unavoidable, the squeegee stroke start position and end position have a large difference in the clearance, which causes a new problem of non-uniform pattern distortion during printing. It is described.

  And in order to solve such a new problem, in the following patent document 1, in the thick film printing method, the squeegee start is performed in conjunction with the squeegee stroke in accordance with the interval between the workpiece during movement of the squeegee and the screen plate. By independently changing the two sides of the screen plate side on the side and the screen plate side on the squeegee end side, the change in elongation due to the squeegee of the screen plate can be sufficiently changed without deteriorating the plate separation during printing. It has been proposed that printing can be performed with a small size, pattern deformation and expansion / contraction during printing can be reduced, the yield can be improved, and the life of the screen plate can be extended.

JP 11-129446 A

  However, conventionally, if the focus is on the plate separation angle and control is made to keep it constant during the squeegee movement, the clearance will change, and conversely, the clearance will be focused and made constant during the squeegee movement. If the control is performed in such a manner, the plate separation angle changes, and there is no known printing method that satisfies the balance between the two so as to obtain a high quality. If the clearance is set large (typically increasing the plate separation angle) with the intention of improving the plate separation, it is inevitable that the screen plate is stretched and the tension load on the screen plate becomes excessively large. The consumption of the screen plate becomes severe, which greatly affects its useful life.

  For this reason, in order to realize screen printing with higher quality and longer service life, it is preferable to keep the clearance constant within the printing surface during the movement of the squeegee, and also to suppress fluctuations in the plate separation angle. And a stable screen printing method is preferred. It can be expected that the printing separation delay is improved by such printing.

  The present invention has been made in view of the above-described problems, and realizes a stable screen printing method in which fluctuations in the plate separation angle and clearance are greatly reduced in the printing surface during movement of the squeegee. The purpose is to do. It is still another object of the present invention to realize a high-quality screen printing method and screen printing apparatus that are stabilized by keeping the clearance constant and further suppressing an increase in the delay of plate separation.

  According to the screen printing method of the present invention, while the squeegee presses and moves the screen plate, the clearance between the printing material directly under the squeegee and the screen plate is always kept constant, and the squeegee press movement start side of the screen squeegee Maintain a state where the side is positioned higher than the side of the squeegee pressing movement of the screen squeegee, and the side of the squeegee pressing movement start of the screen squeegee and the side of the squeegee pressing movement end of the screen squeegee Both are characterized by being moved upward in conjunction with the pressing movement of the squeegee.

  In the screen printing method of the present invention, preferably, at the start of the squeegee pressing movement, the side of the squeegee pressing movement start side of the screen plate is arranged at a height higher than the side of the squeegee pressing movement end, more preferably the squeegee. The straight line in the side view connecting the pressing movement end side and the squeegee pressing movement start side is linked to the squeegee pressing movement with one point on the line extending outside the linear pressing movement end side as a fulcrum. And rotating upward.

  In the printing surface during the movement of the squeegee, it is possible to realize a stabilized screen printing method in which fluctuations in the plate separation angle and the clearance are greatly reduced. More preferably, it is possible to realize a high-quality screen printing method and screen printing apparatus that can stabilize the clearance while reducing the plate separation delay and further suppressing the increase.

It is a conceptual diagram illustrating and explaining a typical screen printing method as one of the preferred embodiments of the present invention. (A) is a figure which shows the change of the plate separation angle (arctan) (right vertical axis) and the constant amount of clearance (left vertical axis) with respect to the movement amount (horizontal axis) of the squeegee in the conventional screen printing method. Yes, (b) shows the change in the plate separation angle (arctan) (right vertical axis) and the constancy of the clearance amount (left vertical axis) with respect to the movement amount (horizontal axis) of the squeegee in the screen printing method of this embodiment. FIG. (A) The horizontal axis is the stroke amount of the squeegee, the vertical axis is the plate separation angle θ (arctan), CL (the height of the fulcrum from the plane of the substrate) and PO (A position by the inclination of the screen plate from the fulcrum) (B) is a table for explaining the magnitude of the release delay for each of the 6 conditions in (a). (A) is a figure explaining three types of screen printers, (b) is a figure explaining the typical four parameters of a flat head type screen printer. FIG. 10 is a drawing-substituting photograph for explaining an image as a result of a comparative experiment of the degree of plate separation delay between the screen printing method shown in the present embodiment and a conventional printing method. FIG. 10 is a drawing-substituting photograph for explaining an image as a result of a comparative experiment of the degree of plate separation delay between the screen printing method shown in the present embodiment and a conventional printing method. FIG. 10 is a drawing-substituting photograph for explaining an image as a result of a comparative experiment of the degree of plate separation delay between the screen printing method shown in the present embodiment and a conventional printing method. (A) is a conceptual schematic diagram explaining the outline of the mechanism of plate separation in screen printing, and (b) shows a mode in which a conventional constant clearance amount Cl is set, the screen plate is pushed down with a squeegee and stroked for printing. It is a conceptual schematic diagram to explain. (A) is a diagram showing the arctan of the plate separation angle θ in the conventional printing method at each position, where B, C, D, E, F, and G are positions advanced every 75 mm from the squeegee stroke start position A; b) In synchronism with the stroke of the squeegee, the side squeezing start side 1000s of the screen plate is raised with the fulcrum 4000 as a fulcrum, and the clearance amount at the squeegee contact position is controlled to be constant at each position. Is a table showing the arctan of the plate separation angle θ, and (c) is a clearance amount of 2.8 mm, 2.6 mm, 2.4 mm, 2.2 mm, and 2.0 mm according to this embodiment, and a squeegee speed of 50 mm / This is shown together with the amount of delay (cm) in the separation of the plate at the center of the pattern and the end of printing when printed in seconds. Represents the change in the clearance between the plate separation angle (θ) and the squeegee stroke position, and (a) is due to a general peel-off (plate separation) device that is generally used. It is a diagram of changes in the actual clearance amount and plate separation angle when the screen frame one side is lifted up by 3.0 mm at a constant speed in synchronization with the squeegee movement, and (b) is the clearance of 3.0 mm. (C) is a diagram in the case where the clearance is maintained at 3.0 mm in the present embodiment, and (d) is a clearance amount of 4. in the present embodiment. It is a figure when 5 mm is maintained. When the tension of the screen plate is low, it is necessary to set the clearance amount larger than the standard in order to obtain a predetermined repulsive force. It illustrates. These are the figures explaining the change degree of plate separation angle ((theta)) when the fulcrum is displaced with respect to the position of embodiment horizontally in the screen printing method of this embodiment.

  In the screen printing method described in the present embodiment, the print quality is uniform by printing with the clearance amount being always substantially constant over the entire printing surface and the plate separation angle being maintained at an angle arctan of 0.008 or more. It is possible to improve the property. In screen printing on a flat bed in which a clearance (clearance) is set between the screen plate and the substrate to be printed (printed material), in order to make the repulsive force of the screen plate constant during printing, the size of the screen frame is 60 mm. % Printing is considered desirable.

  However, in actual screen printing, it is known that a phenomenon in which a delay in plate separation increases from the middle to the second half of the squeegee stroke often impairs printing uniformity. This has been considered to be the greatest principal disadvantage inherent in screen printing. As a countermeasure on the printing apparatus side, there is a case in which plate separation promotion control is performed in which one side of the screen frame is lifted up in synchronization with the pressing movement of the squeegee, but the actual clearance amount is increased. As a result, the amount of extension of the screen plate increases, so that damage and wear to the screen plate increase, causing problems of dimensional stability and plate tension reduction, which is not a fundamental solution.

  It can be considered that the plate separation delay in screen printing is greatly influenced not only by the repulsive force of the screen plate but also by the “plate separation angle” behind the squeegee contact position. As shown in FIG. 2A, the “plate separation angle” when printing with standard plate tension and clearance amount in normal flat-bed screen printing is 0.20. The center portion is 0.07 and the end portion of the printing is very small, 0.004. This can be considered to be a major cause of the increase phenomenon of the separation of printing plates in the latter half of printing. FIG. 2A shows the change in the plate separation angle (arctan) (right vertical axis) and the variability of the clearance amount (left vertical axis) with respect to the movement amount (horizontal axis) of the squeegee in the conventional screen printing method. FIG.

  In the screen printing method shown in the present embodiment, the screen separation angle arctan can be maintained at 0.008 or more over the entire printing portion from the start of printing to the end of printing without changing the substantial clearance amount. It is. In FIG. 2 (b) showing an example using this method, the plate separation angle (arctan) is 0.023 at the start of printing, 0.011 at the center of printing, and 0.010 at the minimum of the second half. is there. FIG. 2B shows the change in the plate separation angle (arctan) (right vertical axis) and the constancy of the clearance amount (left vertical axis) with respect to the movement amount (horizontal axis) of the squeegee in the screen printing method of the present embodiment. FIG. Note that “MS mode clearance 3 mm maintenance” described below the graph of FIG. 2B indicates a mode in which the screen printing method according to the present embodiment is performed with a clearance amount of 3 mm.

  In an actual screen printing test, when the clearance amount during normal printing is reduced by about 35% (that is, in the case of the printing method of the present embodiment in which the clearance amount is reduced to 65% of the conventional case), the center portion The delay in the release of the plate has become the same as before. In other words, in the case where the degree of plate separation delay is the same as that of the prior art, the printing method of the present embodiment in which the clearance amount is reduced to about 65% of the conventional one can be achieved. Accordingly, since the extension amount of the screen plate is reduced in response to the reduction of the clearance amount, the damage and consumption can be suppressed, and the reduction of cost, the ease of maintenance, and the improvement of the throughput can be expected.

  Further, in the screen printing method of the present embodiment, the degree of delay of actual stencil separation is substantially constant from the center to the end of printing, and does not increase with the amount of movement of the squeegee, thereby improving printing uniformity. It becomes. In other words, by adopting the screen printing method described in this embodiment, it is possible to realize a plate separation amount equivalent to 1.5 times the clearance amount in normal screen printing without damaging the screen plate (that is, the plate). In addition, the printing uniformity can be improved by avoiding an increase in the delay of the plate separation in the second half of printing. In addition, this method can eliminate the fundamental disadvantage of screen printing, which is a so-called off-contact method, in which a clearance is set between the screen plate and the substrate.

  FIG. 1 is a conceptual diagram illustrating and explaining a typical screen printing method as one of preferred embodiments of the present invention. As shown in FIG. 1, in the screen printing method of a typical example of the present embodiment, a case where the squeegee 2000 starts to press and slide at the position A is shown as a squeegee 2000A. Further, a case where the squeegee 2000 finishes pressing and sliding at the position G is shown as a squeegee 2000G.

  As shown in FIG. 1, the squeegee 2000 slides and moves from the position A to B, C, D, E, and F sequentially from right to left on the paper surface while pressing the screen plate 1000 against the printing material 3000. The movement ends at the position of. When the squeegee 2000 starts to press and move at the position A, the screen plate 1000 is arranged at the position of the screen plate 1000A (including not only the three-dimensional arrangement but also the orientation and inclination), and the clearance 5000 is maintained at the interval T. Be drunk. The clearance 5000 is an interval T between the screen plate 1000 and the printing material 3000 at the pressed portion of the squeegee 2000.

  The screen plate 1000 is arranged at the position of the screen plate 1000G when the squeegee 2000 finishes pressing and moving at the position G, and the clearance 5000 is maintained at the interval T. Then, while the squeegee 2000 moves from the position A to B, C, D, E, F, and G, the screen plate 1000 is always maintained so that the clearance 5000 is maintained at the interval T. Is position controlled.

  Further, in the screen printing method shown in FIG. 1, during the printing in which the squeegee 2000 is pressed and moved, the pressing movement start side 1000s shown at the right edge of the screen plate 1000 is always pressed and moved at the left edge of the screen plate 1000. The position is controlled so as to maintain a position higher than the start side 1000e. Further, such position control of the screen plate 1000 is non-constant speed control. That is, the pressing movement start side 1000s is controlled to move upward during printing at non-constant speed, and the pressing movement end side 1000e is also controlled to move upward during printing at non-constant speed. .

In addition to the control factors described above, the squeegee 2000 is controlled so that the plate separation angle θ is always a certain value or more during printing, and preferably the plate separation angle θ is set to arctan 0.008 or more. The position is controlled as follows. That is, the plate separation angle θ _A of the screen plate 1000A shown in FIG. 1 is arctan 0.008 or more, and the plate separation angle θ _G of the screen plate 1000G is also arctan 0.008 or more, and the squeegee 2000 moves from A to G. In the meantime, the position is always controlled so that the plate separation angle θ becomes arctan 0.008 or more. The squeegee 2000 is assumed to be controlled at a constant speed, for example, within a range of 50 to 600 mm / sec, as in general screen printing as common technical common sense.

  Further, in a preferred embodiment of the screen printing method shown in FIG. 1, a stretched straight line extending from the pressing movement start side 1000s to the pressing movement end side 1000e of the screen plate 1000 is a plane on which the printing material 3000 is placed. With the intersection intersecting with the fulcrum 4000, the entire screen plate 1000 can be moved upward so as to satisfy the above-mentioned conditions by non-constant speed control. That is, in this case, the fulcrum 4000, the pressing movement start side 1000s and the pressing movement end side 1000e of the screen plate 1000 are always kept in a straight line, and the clearance 5000 at the squeegee 2000 pressing point is always kept constant.

  As a result, the clearance 5000 is always maintained at a constant interval T (typically, an arbitrary value of 3 mm or more in the case of an internal dimension of the screen plate frame of 900 mm), and the plate separation angle θ is arctan 0.008. Therefore, it is possible to achieve high-quality and uniform printing while reducing the wear of the screen plate 1000 and avoiding the delay of plate separation. Therefore, you may comprise as a screen printer provided with the control apparatus and control part for performing the above-mentioned control.

  The fulcrum distance 6000, which is the distance between the fulcrum 4000 and the pressing movement end side 1000e of the screen plate 1000, is the left-right dimension length of the screen plate 1000 in FIG. 1 (the pressing movement start side 1000s and the pressing movement end side 1000e). For example, when the distance is 100 cm, the distance can be 20 cm, for example. This ratio of 100: 20 can be applied even when the size of the screen plate 1000 is changed.

  Further, in FIG. 1, the fulcrum 4000 is located on the plane of the substrate 3000, but it may be raised above the plane. In this case, the clearance 5000 is the sum of an amount corresponding to the height in the height direction along the screen plate 1000 from the fulcrum 4000 and the height corresponding to the raised arrangement. The screen plate 1000 can use a metal mesh (for example, a stainless mesh plate), a chemical fiber mask (for example, a polyester mesh plate), or a metal mask.

(About the plate separation angle θ is arctan 0.008 or more)
As described in the present embodiment, by increasing the position of the fulcrum 4000 by 0, that is, by 0.5 mm from the same plane as the printing material 3000, printing is performed without changing the actual clearance amount as shown in FIG. The degree of change in the stencil separation angle can be changed. FIG. 3 (a) shows CL (height of the fulcrum 4000 from the plane of the substrate 3000) and PO (the screen from the fulcrum 4000) with the horizontal axis as the stroke amount of the squeegee 2000 and the vertical axis as the plate separation angle θ (arctan). FIG. 3B is a graph for explaining the case where the height of the plate 1000A up to the position A is changed in six ways, and FIG. 3B is a diagram for each of the six conditions in FIG. 3A. It is a table | surface explaining the amount of separation delay (cm).

  As described above, CL in FIG. 3 is the height of the fulcrum 4000 with respect to the surface of the substrate 3000, and the value obtained by adding the number of PO, which is the height of the screen plate 1000A at the beginning of printing, is the actual clearance amount. In other words, FIG. 3 shows the experimental results in the state shown in FIG. 1 where the screen plate 1000 is raised relative to the substrate 3000 by the amount corresponding to the value of CL. As the screen plate 1000, a screen plate having a length of 600 mm from the position A to the position G in FIG. 1 was used. The outer dimension of the screen plate 1000 is 1000 mm.

  As the six conditions shown in FIG. 3, the first condition CL = 0, PO = 3, the second condition CL = 0.5, PO = 2.5, the third condition CL = 1, PO = 2, and the fourth condition. There are six conditions: CL = 1.5, PO = 1.5, fifth condition CL = 2, PO = 1, sixth condition, CL = 2.5, PO = 0.5. Under either condition, the sum of CL and PO is 3 mm, so it can be understood that the actual clearance amount is the same at 3 mm.

  In this case, the plate separation angle θ (arctan) at the position F (squeegee stroke 500 mm) further advanced 200 mm from the position D (squeegee stroke 300 mm) at the center of the screen plate 1000 is shown by a black frame in FIG. Furthermore, it changes from 0.011 to 0.006.

  Further, in order to verify the influence of the plate separation angle θ in each case shown in FIG. 3, the size of the plate separation delay when UV ink having a viscosity of 17 Pa.S is printed at a squeegee speed of 50 mm / second is 6. The streets were compared. Using a screen frame with an inner dimension of 900 mm, the polyester mesh was 250 mesh and the printing pattern was a rectangle with a width of 250 mm and a length of 450 mm.

  The plate separation delay at the end of printing is as shown in the table. When the plate separation angle was 0.007 or less, a plate separation delay occurred, and the plate separation delay could be confirmed visually. In addition, at 0.008 or more, no delay in plate separation by visual observation was recognized. From this, it can be said that it is appropriate to set the plate separation angle to arctan 0.008 or more. It should be noted that the plate separation angle arctan is desirably 0.010 or more so as not to cause delay in plate separation even when the viscosity of the ink is higher or when it is desired to increase the squeegee speed.

  FIG. 4A is a diagram for explaining three types of screen printers, and FIG. 4B is a diagram for explaining four typical parameters of a flat head type screen printer. As shown in FIG. 4 (a), the flat bed (flat table) method, which is one of screen printing, presses and slides a flat screen plate against a substrate to be printed placed on a flat table with a squeegee. It is a method of printing.

  Further, as shown in FIG. 4B, the cylinder (curved surface) method prints by pressing the screen plate on the flat plate with a squeegee while rotating the cylinder against the cylindrical side surface of the cylindrical substrate. Is the method. In this method, the screen plate moves back and forth in the horizontal direction, the squeegee does not move, but only presses in place, and the cylindrical substrate is made into a cylindrical shape and is synchronized with the horizontal movement of the screen plate. The print position moves.

  Further, the rotary screen method is a printing method in which the cylindrical screen plate is rotated by pressing in place with a squeegee so that the cylindrical screen plate comes into contact with the printed material while moving the printed material on the flat table. In the present embodiment, a flat bed system in which a squeegee slides and moves is typically used.

  Further, as shown in FIG. 4B, it is known that the flat-bed type screen printing method generally has four main parameters that greatly influence the printing uniformity and quality. The A clearance described in FIG. 4B is the distance between the printing material and the screen plate at the printing location, and is the pressing distance until the squeegee presses the screen plate and comes into contact with the printing material. As illustrated in FIG. 4B, in the state where the screen plate is arranged in parallel with the substrate, the clearance is always constant during the printing operation regardless of the movement and position of the squeegee.

  Further, the B squeegee printing pressure described in FIG. 4B is about the strength of the force with which the squeegee presses the screen plate, and a larger pressing force is required if the tension of the screen plate is large. If it is too large, the burden on the screen plate increases, so that its consumption increases and greatly affects the useful life of the screen plate.

  Similarly, if the clearance is large, the distance to the substrate is increased. Therefore, since the squeegee needs to press and pull down the screen plate for a longer distance, the burden on the screen plate increases. In addition, the squeegee printing pressure has a great influence on the thickness of the ink printed on the substrate (the thickness of the printed ink) and is closely related to the print quality. It is possible to adjust appropriately according to the ink characteristics.

  Further, the C squeegee angle described in FIG. 4B is also known to have a great influence on the film thickness and print resolution of ink or the like printed on the printing material. Furthermore, as for the D squeegee speed shown in FIG. 4B, when this is slow, problems such as ink bleeding and line thickening are likely to occur, and when this is fast, low viscosity ink or It is known that the paste and the high-definition pattern can be relatively handled, and any parameter can be appropriately adjusted according to the printing characteristics.

  FIG. 5 to FIG. 7 are photographs instead of drawings for explaining images as a result of a comparative experiment of the degree of plate separation delay between the screen printing method shown in this embodiment and the conventional printing method. In FIG. 5 to FIG. 7, a line substantially parallel to the squeegee indicated by a black dotted broken line with white background is an explicit line that has been added to clearly show the position of the detachment delay that is slightly blurred.

  FIG. 5A is a diagram for explaining the degree of plate separation delay in the conventional screen printing in which the clearance amount is 3 mm and the squeegee speed is 50 mm / second. The upper photograph shows the vicinity of the center of the squeegee stroke, and the lower photograph. FIG. 6 is a view showing the vicinity of the end of the squeegee stroke. In the conventional printing method shown in FIG. 5A, the squeegee is pressed and slid in a state in which the screen plate is kept 3 mm away from the printing material and always kept horizontal. Therefore, the plate separation delay gradually increases from 5 cm to 12 cm as the plate separation angle θ gradually decreases from the vicinity of the center of the stroke of all 600 mm to the end of the squeegee position.

  In FIG. 5B, the initial clearance amount is 2 mm, and only the side of the pressing movement start side is raised by a total of 3 mm during the full stroke 600 mm movement at 50 mm / sec (normal peel-off control peel-off). FIG. 6 is a diagram for explaining a delay in plate separation in the conventional printing method, in which the upper photograph shows the vicinity of the center of the squeegee stroke (about 300 mm position), and the lower photograph shows the vicinity of the end of the squeegee stroke (position of about 600 mm). . The conventional printing method shown in FIG. 5 (b) gradually increases only the side of the pressing movement start side at a constant speed while pressing and sliding the squeegee in a state where the screen plate is initially kept at a horizontal distance of 2 mm from the substrate. (Usually peel off). For this reason, the clearance amount during printing varies, and the maximum value is about 3 mm. Even when the position of the squeegee was near the center of the stroke of all 600 mm to the end, the plate separation delay was approximately 6 cm, and was almost constant and no increase was observed.

  FIG. 6A is a view for explaining the plate separation delay by the screen printing method (MS mode) described in FIG. 1 as the present embodiment. The clearance is maintained at 3 mm and the squeegee speed is 50 mm / This is the result of a trial experiment in seconds. As shown in FIG. 6 (a), no detachment delay was observed regardless of whether the squeegee position was near the center or near the end. Here, since the screen plate of this embodiment is always inclined during the printing process and is not horizontal, the squeegee presses the inclined screen plate vertically to the horizontal substrate. . Further, FIG. 6B shows the result of trial printing in a state where only the substantial clearance is reduced to 2 mm from the printing conditions of FIG. 6A. In this case as well, although the clearance is as small as 2 mm, the plate separation delay is about 5 cm near the center of the squeegee stroke, and does not increase even at the end of the squeegee stroke.

  FIG. 7 is a diagram for explaining the results of trials performed by increasing only the squeegee speed to 100 mm / second from the printing conditions shown in FIG. In general, it is known that a conventionally known printing method causes a noticeable release delay when the squeegee speed is doubled. However, in the screen printing method shown in the present embodiment, as shown in FIG. 7, the plate separation delay is about 1 cm both near the center and near the end of the squeegee stroke, which is a small value. No increase was observed near the end.

  As described above, the screen of the present embodiment shown in FIGS. 6 and 7 is more suitable than the conventional screen normal printing method shown in FIG. 5 and the printing method in the normal plate separation suppression control (peel off) shown in FIG. It can be understood that the printing method is greatly improved in the state of delayed release.

(Verification and optimization of the effect of improving the separation of the separation angle)
(Overview)
Plate separation in screen printing is the most important mechanism to be optimized first as a prerequisite for optimizing the printing process. In particular, screen printing with high-viscosity ink, etc., a phenomenon in which the plate separation is delayed from the center to the second half of the printing pattern is observed, and in particular, the delay in plate separation increases at the end of printing, causing print quality problems. It is known.

  Plate separation is an ink transfer mechanism to the base material due to the repulsive force of the screen plate, and has been considered to be greatly influenced only by the conditions of plate tension and clearance (interval between the screen plate and the substrate).

  However, since the repulsive force of the screen plate when the clearance is set can be considered to be almost constant within 50% of the screen frame size, the increase phenomenon of the plate separation delay at the end of printing is repulsive. No explanation can be given by the difference in power alone.

  The present inventors considered that the cause of the increase in the plate separation delay was a decrease in the “plate separation angle” at the squeegee stroke position, and quantitatively verified this. Furthermore, an optimization method in the plate separation angle maintaining mode that minimizes the change in the “plate separation angle” without changing the actual clearance amount in screen printing is proposed.

(1. Introduction)
As shown in FIG. 8 (a), the plate separation in screen printing refers to the ink that adheres to the substrate by the repulsive force of the screen plate that has pushed down the clearance amount after the squeegee sliding on the surface of the screen plate has passed. It is to peel off. FIG. 8A is a conceptual schematic diagram for explaining an outline of the mechanism of plate separation in screen printing.

  In order to evenly peel off the ink of the thick screen plate, time (t) and delay (d) required for proper plate separation are required. Appropriately, the delay in releasing the plate is within a few millimeters and cannot be visually recognized with the naked eye. In general, this state is a state of “no delay in separation” and is considered appropriate. Note that if the plate separation time is extremely shortened, the ink will not be peeled off from the screen plate evenly, and the ink may tear off in the middle, causing so-called “chips” or “missing” problems. It is.

  In the actual printing process, if the printing pattern is large and the viscosity of the ink is high, the time required for separating the plate tends to be long, and a state where the plate separation is delayed tends to occur. There are methods to reduce the ink viscosity, reduce the squeegee speed, reduce the print pattern size, etc. in order to achieve the “no detachment delay” state. It is not realistic because it adversely affects image quality and productivity.

  A method of using a high-strength screen mesh and setting a large clearance amount to improve the plate separation property is effective, but this leads to an increase in screen plate cost. The phenomenon of “delaying of the plate separation” increases from the center of the print pattern to the end of printing, but the cause has not been clearly clarified so far.

  The present inventors consider that the plate separation is affected not only by the repulsive force of the screen plate, but also by the “plate separation angle” at which the screen plate separates from the substrate (substrate) behind the squeegee. An attempt was made to measure quantitatively. At the same time, we invented a control method of “plate separation angle” that minimizes “delaying delay” without increasing the damage to the screen plate, and verified the improvement effect of plate separation.

(2. Plate separation angle and plate separation delay in conventional printing)
The plate separation characteristics in screen printing were compared and examined by measuring the amount of visible “delay delay” (delay length). In the ordinary screen printing, as shown in FIG. 8B, the screen plate and the printing material are arranged in parallel to set a certain clearance amount Cl, and the screen plate is pushed down with a squeegee to perform printing.

  If the inner dimension of the screen frame is Fi (for example, 900 mm), the clearance amount Cl (for example, 3 mm), the print pattern size Pa (for example, 450 mm), and the sliding distance from the pattern edge of the squeegee is X, the plate separation angle θ at that time arctan

It becomes.

  Assuming that the positions advanced every 75 mm from the squeegee stroke start position A are B, C, D, E, F, and G, the arctan of the plate separation angle θ is as shown in the table of FIG. FIG. 9A is a diagram showing the arctan of the plate separation angle θ in the conventional printing method at each position where B, C, D, E, F, and G are positions advanced every 75 mm from the squeegee stroke start position A. is there. From the printing start position A to the center position D of the squeegee stroke, the plate separation angle is about ½, 0.007, and at the printing end position G, about ３, 0.004.

  Actual printing is performed in order to quantitatively measure the plate separation delay under these conditions, and the “plate separation delay” video is photographed and observed, and the plate separation delay at the plate center D position and the printing end G position The amount was compared. The printing conditions in that case are shown below. That is, the screen plate was made of polyester 250 mesh, tension 1.3 mm (tension gauge STG75B), and the pattern size was 450 mm in the stroke direction × 250 mm in width. The clearance amount was 3.0 mm. The ink has a viscosity of 17 Pa.s. S oriental ink type UV ink was used, the squeegee was Mino Group hardness of 80 to 85 degrees, the printing pressure was 1.5 mm in indentation, and the squeegee speed was 50 mm / sec.

  As a result, the plate separation started to delay immediately after the start of printing, about 5 cm at the center D position and about 12 cm at the end position G of printing, and the plate separation delay increased with the progress of the squeegee stroke. When the squeegee speed was increased to 100 mm / sec and 150 mm / sec, the delay in separating the plates further increased to 8 cm to 15 cm and 10 cm to 20 cm. It can be presumed that the increase in the detachment delay is caused by a rapid decrease in the detachment angle in the latter half of the printing unit.

(3. Plate frame lift-up operation in the printing method of this embodiment)
In order to examine the influence of the “plate separation angle” on the plate separation characteristics, it is necessary to verify the repulsive force of the screen plate at the time of printing. In order to make the repulsive force of the screen plate constant, it is necessary to keep the actual clearance amount at the time of printing constant.

  For this reason, as shown in FIG. 1, the lift-up operation of one end of the screen plate frame was performed in order to maintain the plate separation angle as small as possible without changing the actual clearance amount. First, with the fulcrum portion (fulcrum 4000 in FIG. 1) located 200 mm outside the screen frame, the clearance amount is set to “0”, the opposite end is lifted up and the screen plate is set in an inclined state as shown in FIG. In this case, the actual clearance amount at the position A at the start of printing was set to 3 mm. However, in this method, the other end of the screen plate frame (the end close to the fulcrum 4000) is naturally lifted slightly as the screen plate frame one end (the opposite end, the end far from the fulcrum 4000) is lifted. It becomes.

  In the printing experiment, in synchronization with the stroke of the squeegee, one side of the screen plate (press movement start side 1000s in FIG. 1) is raised with the fulcrum 4000 as a fulcrum, so that the clearance amount at the squeegee contact position is always constant. Controlled. In this case, the arctan of the plate separation angle θ at each position is as shown in FIG. FIG. 9B shows a case in which the screen plate pressing movement start side 1000s is raised with the fulcrum 4000 as a fulcrum in synchronization with the stroke of the squeegee, and the clearance amount at the squeegee contact position is controlled to be always constant. 4 is a table showing arctan of plate separation angle θ at each position.

  It can be understood that from the beginning of printing to the end of printing, a large plate separation angle of 0.010 or more is maintained, and in particular, from the center position D to the end of printing G is almost constant. By printing under these conditions, observing / evaluating the delay of plate separation, and comparing with normal printing, the influence of the plate separation angle can be quantitatively verified.

(4. Improvement of plate separation delay in the printing method of this embodiment)
Printing was performed at a squeegee speed of 50 mm / sec, with the actual clearance amount being 3.0 mm, the same as in normal printing. There was no delay in releasing the plate, and it was not visible at all. Even when the squeegee speed is 100 / sec, the plate separation delay is “0”. When printing at 150 mm / sec, the plate separation delay is 2 cm at the center of the pattern, 2 cm at the end of printing, and the center of the pattern and the end of printing. It was the same amount of delay.

  When the clearance amount is 2.8 mm, 2.6 mm, 2.4 mm, 2.2 mm, and 2.0 mm, the amount of delay between the center of the pattern and the end of printing when printing is performed at a squeegee speed of 50 mm / sec (cm 9 (c) is shown together with FIG.

  In the printing method according to the present embodiment, the amount of delay in plate separation at the center of the pattern with a substantial clearance of 2.0 mm is the same as that in normal printing with a clearance amount of 3.0 mm. It can be said that the effect is equivalent to 1.5 times in terms of clearance. Further, it is proved that “the plate separation angle” has a great influence on the plate separation property even if there is no difference in the plate separation delay between the central portion of the printing pattern and the end portion of the printing.

(5. Summary)
In screen printing in which the gap between the screen plate and the substrate is set for printing, it has been found that the “plate separation angle” has a great influence on the plate separation property. In normal printing, the reason why the plate separation is delayed from the center portion of the print pattern to the latter half portion is considered to be because the “plate separation angle” becomes small.

  In printing by the printing method of the present embodiment that can maintain the “separation angle” as large as possible, it is possible to obtain a plate separation effect equivalent to plate separation at 1.5 times the clearance amount in the conventional normal printing method. It was. Further, it has been found that the stencil separation property at the central portion of the printing pattern and at the end of printing can be made uniform.

  Further, in the printing by the printing method of the present embodiment, since the substantial clearance amount during the printing is kept constant, the optimum method that can realize uniform plate separation without risk of damage to the screen plate even with high viscosity ink. It is thought that. In addition, as described above, in the printing by the printing method of the present embodiment, the plate separation angle is maintained at a certain level or more, so that a good plate separation characteristic is obtained.

(1. Plate separation angle)
FIG. 10A shows the actual clearance amount and the plate separation angle in the case of the plate separation control in the normal plate separation control with the initial clearance of 2.0 mm and the constant speed lift-up of 3.0 mm. FIG. 10B shows the clearance amount and plate separation angle in normal screen printing. FIG. 10C shows the substantial clearance amount and the plate separation angle when the substantial clearance amount is maintained at 3.0 mm in the printing method according to the present embodiment. FIG. 10D shows the actual clearance amount and the plate separation angle when the actual clearance amount is maintained at 4.5 mm in the printing method according to the present embodiment. Therefore, it can be understood from the above results that the printing method according to the present embodiment can maintain a substantial clearance amount and a large plate separation angle while maintaining a constant clearance amount.

(2. Effects and effects of fulcrum shifting)
FIG. 11 illustrates the degree of change in the plate separation angle (θ) when the fulcrum 4000 is displaced in the horizontal direction on the surface to be printed 3000 without changing its height in the screen printing method of the present embodiment. It is a figure to do. In the graph of FIG. 11, the fulcrum distance is 0 mm, the fulcrum distance is 200 mm, the fulcrum distance is 300 mm, the fulcrum distance is 400 mm, and the fulcrum distance is 1200 mm. As can be understood from this result, it can be understood that it is more preferable to arrange the fulcrum positions so that the fulcrum distance 6000 is in the range of 200 mm to 400 mm from the viewpoint of the uniformity of the plate separation angle in the latter half of the printing. .

  The screen printing method described in the above embodiment is not limited to the individual description in the embodiment, and its configuration, material, operation, and method can be freely changed within the scope of the present invention and obvious scope. However, it can be realized by combination application.

  The present invention is particularly suitable for flat bed printing in a screen printing method.

  1000 ··· screen plate, 2000 ··· squeegee, 3000 · · substrate, 4000 · · fulcrum, 5000 · · clearance, 6000 ··· fulcrum distance.

Claims (13)

While the squeegee presses and moves the screen plate,
Maintaining a constant clearance between the printing medium directly under the squeegee and the screen plate, and
Maintaining the state where the squeegee press movement start side of the screen plate is positioned higher than the squeegee press movement end side of the screen plate, and
The pressing movement start side of the squeegee of the screen plate and the pressing movement end side of the squeegee of the screen plate are both moved upward in conjunction with the pressing movement of the squeegee. Screen printing method. The screen printing method according to claim 1,
The screen printing method according to claim 1, wherein when the squeegee starts to move, the side where the squeegee starts moving is positioned higher than the side where the squeegee ends when the squeegee moves. In the screen printing method of Claim 1 or Claim 2,
In a side view, the straight line connecting the side of the pressing movement start side of the squeegee to the side of the pressing movement end side of the squeegee is a fulcrum at one point on the straight line extending outside the side of the pressing movement end of the straight line. As described above, the screen printing method is characterized in that it rotates upward in conjunction with the pressing movement of the squeegee. The screen printing method according to claim 3.
The screen printing method, wherein the fulcrum is located above a plane on which the substrate is arranged. The screen printing method according to claim 3.
The screen printing method, wherein the fulcrum is located on a plane on which the substrate is placed. In the screen printing method according to any one of claims 1 to 5,
While the squeegee presses and moves the screen plate,
Further, the screen printing method is characterized in that the plate separation angle is always maintained at a predetermined angle or more. The screen printing method according to claim 6.
The said predetermined angle is arctan0.008. The screen printing method characterized by the above-mentioned. The screen printing method according to any one of claims 3 to 5,
The ratio of the fulcrum distance, which is the distance between the fulcrum and the side of the press movement end of the screen plate, and the length of the screen plate is 20 to 40: 100. . The screen printing method according to any one of claims 1 to 8,
The screen printing method, wherein the screen plate is a metal mask formed of stainless mesh, polyester mesh, metal, or resin. The screen printing method according to any one of claims 1 to 9,
The screen printing method, wherein a speed at which the squeegee is pressed and moved is a constant speed in a range of 50 mm / second to 600 mm / second. In the screen printing method according to any one of claims 1 to 10,
The screen printing method, wherein the upward movement of the screen plate in conjunction with the pressing movement of the squeegee is non-constant movement. The screen printing method according to claim 6.
The said predetermined angle is arctan0.010. The screen printing method characterized by the above-mentioned. 13. The press movement start side and the press movement end side are controlled in conjunction with the press movement of the squeegee so as to execute the screen printing method according to any one of claims 1 to 12. A screen printing apparatus comprising a screen plate control unit.