JP4016491B2 - Squeegee and squeegee mechanism and screen printing method using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a squeegee used for screen printing, a squeegee mechanism, and a screen printing method using the squeegee, and in particular, an ordinary squeegee requires precise printing in which squeegee wear and screen plate wear are problematic. The present invention relates to a squeegee for screen printing used for manufacturing electronic components, a squeegee mechanism, and a screen printing method using the squeegee.
[0002]
[Prior art]
Squeegees used for screen printing are roughly classified into two types: rubber-based ones and flexible metal plates such as steel. The former is used when the mesh is normal polyester, amide, or stainless steel, and is also used in the case of a metal plate. The latter is used when the screen mesh is stainless steel and metal plates. This limitation is due to the wear of the mesh by the squeegee.
Examples of the shape of a squeegee used in the past are shown in FIGS. 6A to 6H. The most important shape of the squeegee is the portion in contact with the screen plate and the shape in the vicinity thereof. In this part, the action of pushing ink or paste toward the plate occurs. The physical properties required for the squeegee are rubber elasticity and repulsive force as they are closely related to the printing pattern and ink characteristics, and also require solvent resistance to the ink solvent.
In an actual screen printing machine, the type of squeegee and the angle to the printed product can be changed by a squeegee holder that supports the squeegee. The moving speed and pressure of the squeegee are set by the entire mechanism of the printing press.
[0003]
This conventional squeegee and squeegee mechanism have the following problems. In other words, it is desirable to select the optimal squeegee material and shape according to the target pattern, and to select the optimal squeegeeing conditions, but the squeegee that can be used as described above is greatly limited by the type of mesh. is there. For example, when a metal squeegee is used for a normal polyamide or polyester mesh, the mesh is damaged, resulting in a defective version.
[0004]
On the other hand, a rubber-based squeegee will not damage any normal plate, but as printing is repeated, the squeegee gradually wears due to friction with the mesh, and the squeegee action changes, resulting in good printing. Can not continue. If good printing is no longer possible, grind again. A polishing apparatus (squeegee polishing machine) for this purpose is commercially available, and anyone can polish it. However, as the number of precise screen printing works increases in recent years, it is necessary to strictly maintain printing conditions, so that the allowable range of the squeegee shape is narrowed, and it is necessary to polish frequently. At the time of polishing, it is necessary to accurately reproduce the previous shape. For this reason, a precise polishing apparatus is required, and the time spent for regenerating polishing is increased.
[0005]
Therefore, one of the objects of the present invention is to prevent squeegee wear. In other words, the direct cause of wear is friction with the mesh, but swelling of the squeegee due to the ink solvent is also a factor. In recent years, as the types of inks increase, the types of ink solvents increase, and the squeegee swells with solvents. In this case, in response to the faster wear, it may be possible to increase the frequency of polishing, but there is a case where it is impossible to cope with it and it is necessary to search for another squeegee material. For example, silicone rubber squeegees are being used instead of urethane rubbers. As a countermeasure, a squeegee whose surface is coated with a solvent-resistant material as shown in FIG. 6 (h) may be used, but the disadvantage of this type of squeegee is that it is polished and regenerated when worn. I can't.
[0006]
Yet another problem is that squeegee wear does not occur uniformly over the entire area, but the reaction force of the screen plate on the squeegee during printing varies from place to place (see Figure 7), so how to reduce the squeegee also depends on the place. It will vary depending on. Therefore, there has been a problem that unevenness of the squeegee location also occurs sequentially in the printing result.
[0007]
As described above, one of the characteristics required for a squeegee is wear resistance, but moderate elasticity is also important. That is, since hard ink has little sagging after printing, it is often used when a precise pattern is required. Therefore, a highly elastic metal squeegee is suitable. However, in the case of a metal squeegee, only a stainless mesh or a metal mask can be used. However, it is necessary to use a polyester or polyamide mesh plate for reasons such as pattern shape and cost. In this case, even a rubber squeegee is required to have an extremely high hardness of 90 to 100. However, if the hardness is increased, the flexibility of the squeegee portion is lost and skimming tends to occur.
[0008]
For this reason, for example, it is conceivable that two types of materials are bonded together to meet the demand, and some of them are commercialized (see FIG. 6E). That is, the surface of the squeezing portion (printing direction) is made of a hard and highly wear-resistant material, and the back surface is made of a material having appropriate elasticity. However, even with this structure, the progress is slow, but wear occurs, the printing conditions change, and the printing results also change.
At present, screen printing for high-definition printing requires a squeegee that has a moderate repulsive force, a moderate flexibility, and a very strong wear resistance, but still satisfies it. There is no.
[0009]
Furthermore, as a fundamental problem, the conventional method of squeezing cannot sufficiently cope with various precision pattern printings mainly required for manufacturing electric / electronic parts. That is, even if the conditions are changed variously, it is impossible to satisfy the required specifications, particularly the specifications of the ink coating thickness and its uniformity.
[0010]
[Problems to be solved by the invention]
In other words, the squeezed part is reduced by wear during printing and the printing state changes, but the problem is to stabilize the squeezed part in a good state for a long time and to improve the printing stability. is there.
It is another object of the present invention to provide a squeegee that satisfies the conflicting conditions of flexibility and hardness and has wear resistance, and that is less dependent on the solvent of the ink.
In addition, the conventional squeegeeing method is expanded to provide a device that can meet recent demands.
[0011]
[Means for Solving the Problems]
  The present invention has been made to solve the above-described problems, and a squeegee structure for screen printing is a film material that covers the surface of a core material and at least a portion where squeegee is performed.And an intermediate layer between the core material and the film materialConsists ofThe film material is movable relative to the core material,The position where the film material is in contact with the plate is movable during printing and stopping, and the core material is made of an organic material having rubber elasticity and a metal plate having flexibility, or a composite material in combination thereof. further,A coating for reducing friction is applied to the surface of the intermediate layer in contact with the film material.
[0012]
The film material may be any one of polyester, polycarbonate, polyamide, polyimide, or a composite thereof having a pencil scratch strength of 5H or more.
[0013]
Further, the cross-sectional shape of the squeegee portion of the core material is an arc shape.
[0014]
The screen printing squeegee is characterized in that the structure of the squeegee comprises a core material and a film material covering at least the surface of the squeegee portion, and the film material is movable relative to the core material. The moving mechanism of the film comprises at least a film roll holder, a film feeding section, a film winding section, and a tension adjusting section, and a plurality of core members are provided on the rotating shaft, and the rotating shaft is rotated. Therefore, the squeezing mechanism can be changed to a desired core material.
[0015]
Further, the squeezing mechanism is characterized in that the film is configured in an endless shape so that the material is different in the moving direction.
[0016]
Furthermore, when screen printing is performed using the squeegee and squeegee mechanism, the core material is changed or the film is moved while the squeegee is stopped.
[0017]
In addition, when screen printing is performed using the squeegee and squeegee mechanism, the surface film moves during squeezing.
[0018]
Furthermore, when screen printing is performed using the squeegee and squeegee mechanism, the ink ejection amount is controlled by changing the moving speed of the surface film.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments will be described with reference to the drawings.
First, as shown in FIGS. 1A, 1B and 1C, the squeegee structure of the present invention uses at least a two-layer structure. That is, it has a two-layer structure in which at least the core material 11 and its surface are covered with the film 12. The film 12 is in contact with the plate and performs a squeegee action, and the film material performing the squeezing action can move in a direction along the core surface and in a direction to update the linear squeegee portion. The structure is characterized by the above.
[0020]
Further, when the core material 11 has a two-layer structure having elasticity and flexibility, it is made of an organic material having rubber elasticity or flexibility, and the surface film material 12 is a polyester-based material having wear resistance and solvent resistance. It was made of polycarbonate, polyamide.
In the case of a three-layer structure, the core material 11 has elasticity and the intermediate layer has flexibility, and the surface film has wear resistance and solvent resistance as in the case of the two-layer structure. did.
Furthermore, the cross-sectional shape of the squeegee portion is an arc shape. The arc shape in this case includes not only the literal shape but also an elliptical shape or a more complicated curved shape.
[0021]
In addition, the film moving mechanism is composed of at least a film roll holder, a film feeding section, a film winding section, and a tension adjusting section (FIG. 1 (c), FIG. 2, FIG. 3). That is, FIG. 1 (c) shows the mechanism part provided in the squeegee portion, FIG. 2 shows the mechanism part provided in the squeegee holder part 20, and FIG. The structure provided with these mechanism sections.
[0022]
Further, as the core material 11 of the squeegee can be easily changed, a plurality of different core materials 11a, 11b, 11c, and 11d are provided on the rotary shaft 16, and the desired core material is rotated by rotating the rotary shaft. A structure (see FIGS. 4 and 5) that can be changed to 11 is provided.
[0023]
When screen printing is performed using these squeegee and squeegee holder mechanisms, the surface film can be moved during squeezing, and the film materials 12a, 12b, 12c, and 12d have a plurality of different materials with respect to the moving direction. Provided is a screen printing method characterized by an endless film.
[0024]
That is, when screen printing is performed using the above-described squeegee, squeegee mechanism, and further the screen printing machine on which the squeegee is installed, the core material 11 is changed or the film 12 is moved while the squeegee is stopped. Provided is a printing method that is characterized, and further a screen printing method that controls the printing film thickness by controlling the moving speed of the surface film.
[0025]
In general, it is said that the tip of the squeegee, that is, the part where the squeegee and the screen plate come into contact with each other, should be made as sharp as possible. . However, the degree to which the tip is rounded may vary depending on the viscoelasticity of the ink and the roughness and tension of the screen mesh, and it has hardly been elucidated and has been determined by feeling and experience.
The present inventors examined this point, and firstly, it was confirmed that the amount of ink passing through the mesh decreases as the tip of the squeegee becomes sharper, and the amount increases when the squeegee becomes round. In this case, the ink on the plate is not scraped off and remains on the mesh in the form of a film. However, this relationship does not hold if the release remains so bad. As a result of experiments, it was found that if the pressure of the squeegee is increased, ink can be removed even with a squeegee having a rounded tip, and ink passing through the mesh can be raised.
Further, it was confirmed that the ink on the plate could be scraped even with a squeegee having a tip curvature of about 1 cm, and that the amount of ink passing through the mesh increased. Furthermore, the amount of ink passing through the mesh increased as the so-called attack angle of the squeegee was reduced. Both of the basic reasons are that the action of the squeegee pushing the ink downward (plate side) becomes stronger as the angle becomes lower. Based on such knowledge, the present invention has been achieved.
[0026]
The action / effect and material of the film covering the core material, which is the first feature of the present invention, will be described below.
The squeegee effect is reduced as the thickness of the same film increases, but the edges become rounder and lower. That is, the time and labor for changing the position of the film can be reduced. The opposite is true for a thin film. Usually, a thickness of 10 to 100 μm is used. When a polyester film having a thickness of 30 μm is used, when the mesh is polyester, the number of times that printing can be performed before the position is changed is approximately 500 times depending on the printing pressure. When the mesh is stainless steel, it is about 300 times. In the case of a metal mask, it is about 100 times, but the edge of the metal mask is not scraped by a steel doctor, and the life of the metal mask becomes almost infinite. However, the front side of the metal mask, that is, the edge on the squeegee side needs to be slightly obtuse by a method such as etching.
[0027]
In the case of a three-layer structure, the elastic layer that is an intermediate layer usually has a thickness of 5 to 10 mm. The surface is often formed with a layer of silicone resin or fluororesin in order to improve sliding with the film. Further, it is preferable to apply a friction-reducing coat such as a silicone resin lubricity coat on the inner surface of the film, that is, the surface in contact with the elastic layer.
[0028]
The shape of the tip portion of the squeegee may be the same as the conventional shape (see FIG. 6). Particularly effective in the present invention is that the cross-sectional shape of the tip in FIG. However, the arc may be a part of an ellipse, or may be a shape in which the arc is distorted. In the present invention, a shape having no curvature radius of 2 mm or less is called an arc shape. In this case, the number of times of printing until the position of the film needs to be moved is more than several times that of a right angle. Even in the case of an arcuate tip, the printed state changes considerably when worn, but in the case of the present invention, it is constant. Further, the squeegee having this shape has an advantage that even if the attack angle of the squeegee (the angle between the mesh in the portion in contact with the screen mesh and the squeegee) changes significantly, the aspect of squeezing does not change much.
[0029]
In any case, according to the present invention, after the shape of the tip is optimized, the shape does not change due to wear, so the printing situation is stable over a long period of time. Until now, measures have been taken without clearing whether the change in printing state is due to ink viscosity change (due to solvent evaporation), squeegee wear, or other causes. However, according to the present invention, the cause can be specified somewhat easily, and stable printing can be performed considerably.
[0030]
Further, as a novel screen printing method, there is a printing method in which the surface film is moved when the squeegee of the present invention is moving during printing. There are two types of movement directions, the reverse direction to the printing direction, and the effects are different.
When the ink is moved in the forward direction, the ink is sent to the tip of the squeegee, so that the amount of ink that passes through the mesh, that is, the amount of ink to be printed (the amount of printing) increases. When the moving speed of the film becomes faster than the moving speed of the squeegee, the ink deposit amount further increases. In such a case, it is also effective to make the film 12 an endless type.
On the other hand, if the film feed direction is opposite to the squeegee advance direction, the ink supply amount decreases and the fill amount decreases, which is effective when it is desired to reduce the ink fill amount.
[0031]
This new screen printing method can finely adjust the ink volume. In the past, screen printing has been adjusted by adjusting the squeegee speed, changing the emulsion thickness, changing the ink viscosity, changing the printing pressure (squeegee pressure), There were a method of changing the attack angle and a method of changing the gap between the screen plate and the substrate. Of these methods, the speed that can be adjusted during printing is the moving speed of the squeegee. However, only adjusting the moving speed of the squeegee has a narrow adjustment range of the height, and other measures have to be used in combination. This problem has been considerably improved by the method of the present invention.
[0032]
In particular, even if it is desired to increase the moving speed of the squeegee in order to increase the amount of ink, it is effective when the mechanical limitations are limited. On the other hand, when it is desired to reduce the amount of ink, if the moving speed of the squeegee is lowered, the printing speed is lowered, so that the throughput is lowered. However, if the method of the present invention is used, the amount of ink deposited can be reduced without reducing the throughput.
[0033]
【Example】
Hereinafter, the present invention will be described in detail by way of specific examples.
[0034]
<Example 1>
A case where a silver paste for wiring is printed with a width of 70 μm will be described.
A normal urethane squeegee (thickness 10 mm, tip angle 90 degrees, rubber hardness 70) was tightly covered with a 15 μm thick polyester film, and the tension was 50 g / cm. The mesh was a stainless steel 325 mesh printed with a conductive paste. Printing was performed at an attack angle of 70 degrees, a printing pressure of 500 g / cm, and a squeegee speed of 10 mm / sec. The polyester film has only to be moved about 5 mm every 500 printings, and the printing results were very stable.
[0035]
<Example 2>
A case will be described in which a paste that has to be squeezed at a high squeegee pressure because of its slight rubber elasticity is printed. Although it is necessary to use a silicone rubber squeegee due to the solvent, there is no silicone rubber squeegee with high hardness and high wear resistance capable of applying a high squeegee pressure. Therefore, the core material structure is a three-layer structure. The core part was a steel plate with a thickness of 3 mm, the middle part was urethane rubber (rubber hardness 95) with a thickness of 10 mm, and the film was a polyester film with a thickness of 30 μm. Printing was performed at an attack angle of 75 degrees, a printing pressure of 1500 g / cm, and a squeegee speed of 5 mm / sec. It was possible to print continuously except that the film was moved every 300 times. The printing finish was very stable and no defective products were generated.
[0036]
<Example 3>
An example of a squeegee mechanism (see FIGS. 4 and 5) that comprehensively uses the present invention and a printing method using the mechanism will be described.
First, the structure and function will be described. The overall structure is such that a predetermined squeegee pressure can be applied by moving up and down with an air cylinder 45 installed on a column connected to the main body of the printing press. As the portions, four types of core members 11 (a) to (d) of the squeegee 11 are attached to a rotating shaft 16 that can be rotated and fixed. The film 12 serving as the upper squeegee surface is endless, and goes around along the squeegee core and the upper rotating roll 41. The film 12 is formed by joining four kinds of materials, and the upper rotating roll 41 is capable of forward and reverse rotation and stationary at a predetermined number of rotations by a servo motor drive. The tension of the endless film is set to a predetermined value by the tension control mechanism 42. In addition, a position adjustment bar 46 for adjusting the angle at which the film of the squeegee acting part overlaps the squeegee core is provided on the squeegee traveling direction side. The rib on the back substrate of the plasma display was printed as follows with a screen printing machine in which this apparatus was set.
The ribs are striped, the width is 70 μm, the height is 200 μm, the length is about 700 mm, and about 3000 lines are arranged at a pitch of about 260 μm. Since the height is as high as 200 μm, the repeated printing is usually performed about 10 to 20 times. In the first printing, printing with less paste sagging and high positional accuracy is performed, and the next several times are performed to increase the height (thickness). In the last few times, printing is performed with less unevenness on the upper end surface. In this case, a paste that is baked to become black is often used. The squeegee of the present invention was used for printing, and a squeegee core material having a rubber hardness of 50 degrees polished at an acute angle (70 degrees) was set at approximately 90 degrees. The film used was a 15 μm thick polyester film, and was fixed during printing. The angle between the film and the ridge was 75 degrees, and the tension was 50 g / cm. Instead of a small paste discharge amount, a print pattern with little paste sagging and high positional accuracy was formed.
[0037]
After the paste is dried, the squeegee core is made of urethane with a cylindrical hardness (radius 1 cm) and a rubber hardness of 80 degrees and a thickness of 2 cm. Also, those having a convex of 1 mm were used. This shape is such that the reaction force of the screen plate is uniformly applied over the entire surface, and as a result, it is effective for making the discharge amount of the paste the same over the entire surface. This was set at an attack angle of about 70 degrees. The film used was a 30 μm thick polyester film part, the angle between the film and the mesh was 50 degrees, and the tension was 100 g / cm. During printing, the film was moved in the direction opposite to the moving direction of the squeegee portion at a speed about half the moving speed of the squeegee portion. That is, the relative speed between the mesh and the film is about half the squeegee speed. However, in response to the viscosity of the paste gradually increasing and the discharge amount decreasing, the film feed rate was increased by up to about 20% to make the coating thickness constant. In normal printing, the paste is 20 μm at most, but by printing under these conditions, the deposit in one printing is 40 μm and the thickness accuracy over the entire surface can be suppressed to <± 5 μm. It was. However, the print surface had a print quality with a clear mesh shape. The polyester film did not wrinkle during printing. Printing under these conditions was repeated four times while drying each time.
[0038]
Next, as printing for improving the smoothness of the surface, urethane rubber having a thickness of 5 mm and a hardness of 40 degrees was used as the core material of the squeegee. A polyamide film having a thickness of 20 μm was used as the film, and moved at a rate of 1/3 in the same direction as the traveling direction during printing, and the paste was stirred to lower the viscosity. The angle between the film and the mesh was 45 degrees, and the tension was 20 g / cm. The printing pressure was 30 g / cm. The unevenness of the surface of the paste after printing was within ± 5 μm. Also in this case, the moving speed of the film was changed by about ± 20% in order to adjust the printing thickness. In these series of printings, the printing pressure, the printing gap, and the printing speed related to the printing position accuracy were constant within ± 20%. For this reason, the printing position accuracy could be maintained. In addition, in the case of squeegee polishing with a urethane or silicone material having low hardness, the printing result has changed too much unless it is polished with 2000 printings, but when this squeegee structure is used, 50000 printings are performed. However, the printing results did not change in practice. For this reason, the operating rate of the printing press improved.
[0039]
<Comparative example>
In the normal method where the polyester film is not covered, printing was performed under almost the same conditions. First, since printing was unstable immediately after polishing, the speed, pressure, etc. of the squeegee were discarded after about 300 times of printing. The printing conditions were reset, and the main printing was started. Further, the squeegee must be polished every time printing is performed about 3000 times. After polishing, the printing conditions were always readjusted.
[0040]
【The invention's effect】
The present invention has the following effects.
1) There is no need to replace and polish the squeegee. (The squeegee must be polished only once.)
2) It becomes practically possible to use a squeegee having a complicated shape.
3) Printing is stable over a long period of time.
4) The amount of ink can be controlled during printing.
5) When performing another printing, it is not necessary to remove the squeegee and replace it.
6) It can cope with the need for different squeegees (shapes) in overprinting.
7) Long-term continuous operation becomes possible, and the operating rate of the printing press increases.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a squeegee in an embodiment of the present invention.
FIG. 2 is a schematic view showing a squeegee and a squeegee holder in an embodiment of the present invention.
FIG. 3 is a schematic view in which a printing machine according to an embodiment of the present invention is provided with a film supply and winding mechanism.
FIG. 4 is a side view showing a squeegee structure in which the squeegee core material and four types of films in the embodiment of the present invention can be exchanged.
FIG. 5 is a front view of the above figure.
FIG. 6 is an explanatory view showing a conventional squeegee shape.
FIG. 7 is an explanatory view showing a state of a conventional squeegee core material pressure.
[Explanation of symbols]
10 ... Squeegee
11 (11a, 11b, 11c, 11d) ... core material
12 (12a, 12b, 12c, 12d) ... film
16 ... Rotation axis
20 ... Squeegee holder
41 ... Rotating roller
42 ... tension control bar
44, 45 ... Air cylinder
46 ... Position adjustment bar
50: Printing machine
51 ... Frame
52 ... Mesh

Claims (10)

Structure of the squeegee for screen printing is a film material covering a surface of the part for performing at least squeegee the core material, made from an intermediate layer between the film material and the core material, said film material and the core material A screen printing squeegee characterized in that the relative position of the film material can be moved so that the position where the film material is in contact with the plate can be moved during printing and stopping.   2. The squeegee for screen printing according to claim 1, wherein the core material is an organic material having rubber elasticity and a metal plate having flexibility, or a combination thereof.   2. The squeegee for screen printing according to claim 1, wherein the film material is any one of polyester, polycarbonate, polyamide and polyimide having a pencil scratch strength of 5H or more, or a composite thereof. 2. The screen printing squeegee according to claim 1, wherein a coating for reducing friction is applied to a surface of the intermediate layer that contacts the film material.   The squeegee for screen printing according to claim 1, wherein a cross-sectional shape of the squeegee portion of the core material is an arc shape.   The screen printing squeegee structure comprises a core material and a film material covering at least the surface of the squeegee portion, and the film material is movable relative to the core material. A squeegee for squeegee, wherein the film moving mechanism comprises at least a film roll holder, a film feeding section, a film winding section, and a tension adjusting section, and a plurality of core members are provided on a rotating shaft, and the rotating shaft is rotated. A squeezing mechanism characterized in that it can be changed to a desired core material.   7. The squeezing mechanism according to claim 6, wherein the film is formed in an endless shape so that the material is different in the moving direction.   A screen printing method comprising: changing a core material or moving a film while the squeegee is stopped when screen printing is performed using the squeegee and squeegee mechanism according to claim 1.   9. The screen printing method according to claim 8, wherein when screen printing is performed using the squeegee and squeegee mechanism, the surface film moves during squeezing. 10. The screen printing method according to claim 9, wherein when screen printing is performed using the squeegee and squeezing mechanism, the ink discharge amount is controlled by changing the moving speed of the film on the surface.

Images