JPH04364953A - Offset screen printing method - Google Patents

Abstract

PURPOSE:To provide an offset screen printing method solving the variation of absolute accuracy becoming a problem at the time of the formation of a fine pattern having a large area used in the production of various electronic parts such as a printed circuit board, a liquid crystal display device or a thermal head by printing and forming the fine pattern having a large area with absolute accuracy by printing. CONSTITUTION:The ink pattern formed on a plate 32 is transferred to the surface of an offset screen 30 formed into a screen shape and subsequently transferred to an object 39 to be printed. By this method, even when a large area is printed, the ink pattern formed on the plate 32 can be transferred and formed on the object to be printed without being distorted.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to an offset screen printing method for forming fine patterns over large areas by printing, which is mainly used when manufacturing various electronic components such as circuit boards, liquid crystal display devices, and thermal heads. be.

0002

2. Description of the Related Art Conventionally, when manufacturing electronic components such as circuit boards, liquid crystal display devices, and thermal heads, a process of forming fine conductor (or insulator) patterns has been necessary. Furthermore, in the case of other electronic components, insulators (
(or dielectric materials, magnetic materials, etc.) is required regardless of the size of the printing area. Furthermore, when producing color filters and light emitting elements, it is desired to form fine patterns over a wider area. Conventionally, processes using photoresists have been widely used for such applications. However, when using a photoresist, there are problems such as cost and the inability to handle ultra-large patterns of several tens of inches or more, and a technology for forming fine patterns over a large area at lower cost has been desired.

[0003] Production methods using printing technology are effective for this cost reduction, but below we will discuss conventional fine pattern printing methods in order, taking screen printing, intaglio offset printing, and octopus printing as examples. explain.

First, an example of fine pattern printing by screen printing will be described with reference to FIG. In FIG. 7, 1 is a screen frame, and inside the screen frame 1, a screen 2 on which a pattern 3 is formed is stretched with a constant tension. 4 is a squeegee.

In screen printing, when the ink is squeezed by the squeegee 4, it passes through the pattern 3 formed on the screen 2 and is transferred in the shape of the pattern 3 onto the surface of the printing substrate 6 fixed on the stand 5. , printing pattern 7
will be formed. Generally, in the case of screen printing, if fine patterns are to be printed, it is necessary to increase the number of meshes on the screen used. However, even if the number of screen meshes is simply increased or the diameter of the wire forming the screen mesh is made thinner, there is a limit to the printing of fine patterns or fine pitches. This means that printability is not determined solely by screen performance. In reality, no matter how good a screen is used, depending on the ink, the printed ink pattern may run on the printing material, resulting in collapse or short-circuiting. For this reason, various improvements have been recently made to the ink to prevent the fine pitch portions of the printed pattern from running or collapsing. For example, an ultraviolet-curable or electron-beam-curable resin is used as ink, and at the same time as printing is completed and an ink pattern is formed (before the ink runs, collapses, or shorts out), the ink is irradiated with ultraviolet rays or electron beams. , it has been proposed to harden the ink to obtain a sharp ink pattern that does not run or collapse.

However, even with these proposals, sufficient curing may not be achieved depending on the ink material. Moreover, in this case, the material cost of the ink itself increases, and the cost of equipment related to ink curing increases significantly, making it impractical. In addition, ink that has been cured (curable ink) is difficult to cause thermal decomposition and is further hardened by heat treatment, so it cannot be used for manufacturing ceramic-related electronic parts. Furthermore, in the case of printing on electronic components, ink is often less likely to soak into the printing material compared to paper. When paper or some raw ceramic sheets are selected as the printing material, the printed ink and the solvent in the ink are absorbed by the printing material, making it difficult for the printed pattern to flow and cause it to collapse or short out. Become. However, when glass or ceramic substrates, which are widely used in the manufacture of electronic components, are selected as the printing substrate, the fine pitch portion of the pattern is not absorbed by the printing substrate, so the fine pitch portion of the pattern It will run over the top and cause it to collapse or short out. Furthermore, in the case of screen printing, the pattern to be printed is formed by emulsion on a screen (the screen is squeezed by a squeegee each time it is printed). Therefore, the pattern to be printed can be formed with high precision because the screen is not stretched at the beginning of printing. However, when printing is repeated many times, the screen gradually becomes irregularly deformed due to the repeated distortion caused by the squeegee. For this reason, the emulsion pattern formed on the screen surface is irregularly deformed in accordance with the irregular deformation of the screen itself. For this reason, in the screen printing method,
No matter how precise a screen is, it cannot extend its lifespan. From the above points, there is a limit to the ability to print and form fine patterns by screen printing.

As an alternative printing method to the screen printing method, an intaglio offset printing technique has been proposed in Japanese Patent Publication No. 36512/1983. Intaglio offset printing will be explained below using FIG. 8. FIG. 8 is a perspective view showing an intaglio offset printing method. In FIG. 8, reference numeral 8 denotes a stand, on which the intaglio plate 9 and the printing material 11 are fixed. 13 is a blanket, which is fixed to the surface of the blanket cylinder 14. For intaglio offset printing, intaglio 9
When the blanket cylinder 14 rotates and moves above the intaglio pattern 10 filled with ink,
The ink is transferred to the surface of the blanket cylinder 14 to form an ink pattern 15. Next, as the blanket cylinder 14 rotates, the ink pattern 15 formed on the blanket 13 is retransferred onto the transfer target 11.
A printed pattern 12 will be formed.

Next, tacho printing (also known as pad printing) will be explained using FIG. 9. FIG. 9 is a perspective view showing tacho printing, which is one of the offset printing methods using an intaglio plate. In FIG. 9, 16 is a stand, an intaglio plate 17 and a printing substrate 1.
9 is fixed. 22 is a rubber-like elastic body called an octopus, which is fixed on the table 21 which is moved up and down by a cylinder 23. The rubber-like elastic body 22 is usually made of silicone rubber or the like, and has a shape similar to an octopus's head. For this reason, this printing method is generally called tacho printing. Octopus printing is also an offset printing method using an intaglio plate similar to intaglio offset printing. In the case of tacho printing, ink is transferred from the ink-filled intaglio pattern 18 onto the surface of the rubber-like elastic body 22 by the upper and lower sides of the cylinder 23, forming an ink pattern (not shown in FIG. 9). Next, this ink pattern is retransferred onto the printing material 19 by the upper and lower cylinders 23 to form a printing pattern 20.

Intaglio offset printing and tacho printing similarly transfer an ink pattern formed on an intaglio onto an object to be transferred via the surface of the transfer object. In the case of octopus printing, when the octopus is pressed onto the intaglio and printing substrate, it is greatly distorted. For this reason, although thin lines can be printed, fine patterns with excellent absolute precision cannot be printed. In fact, tacho printing is usually only used for simple printing on curved surfaces such as golf balls, where absolute precision is not required. Although to a lesser extent than in tacho printing, a similar phenomenon of change in absolute precision also occurs in intaglio offset printing. In the case of intaglio offset, when the blanket is pressed onto the intaglio and printing substrate, the blanket is distorted in the direction of rotation of the blanket cylinder (on the other hand, there is almost no distortion in the longitudinal direction of the blanket cylinder)
As a result, there was a problem in that the absolute dimensions of the ink pattern printed on the printing medium varied depending on the printing direction.

This problem will be explained in more detail using FIGS. 10 and 11. 10 and 11 are for explaining the elongation of the blanket.
, 24 is a blanket cylinder, 25 is a blanket, 26 is a printing medium, 27 is a bulge, and 28 is a compressed layer. In addition, in FIGS. 10 and 11, (a) shows the state before the blanket is pressed against the surface of the printing material;
(b) explains the state after the blanket is pressed against the surface of the printing material with a constant pressure.

When a blanket structure (generally called a solid type) as shown in FIG. 10 is used during normal offset printing, a blanket 25 called a bulge 27 is formed at the location where the blanket 25 is pressed against the printing medium 26. deformation occurs. As the blanket cylinder 24 rotates, the bulge 27 also moves. As a result, the bulge 27 reduces the absolute accuracy of the printed pattern. In particular, the size of the bulge 27 increases as the pressing pressure (generally called printing pressure) of the blanket cylinder 24 against the printing medium 26 increases.

To solve this problem, a blanket structure (generally called a compressible type) as shown in FIG. 11 has been proposed. In the case of FIG. 11, when the blanket 25 is pressed against the printing medium 26, the compressed layer 28 will be deformed instead of the blanket 25. Therefore, deformation of the blanket 25 does not occur. However, in the case of a compressible blanket, when the printing pressure is changed, the blanket 2
The area in which 5 contacts the printing medium 26 changes, and the actual pressure per unit area does not change much. For this reason, even if the printing pressure is increased in an attempt to improve the ink transferability from the plate to the blanket or from the blanket to the printing material, the ink transferability cannot be improved much. In the case of general printing on paper, etc., the printing material is an elastic body having a compressed body, and the printing material may have ink absorbing properties, making it easy to obtain stable printed materials. However, when printing on electronic parts, etc., even if a solid type or compressible type blanket is used, if the substrate to be printed is a glass or ceramic substrate, it does not have the compressibility or elasticity of paper, nor the ink absorption ability. Therefore, it is extremely difficult to print fine patterns with a certain precision. In other words, in the various methods used for conventional printing on paper, the printing substrate is replaced with a glass or ceramic substrate, and it has not been possible to obtain the absolute accuracy equivalent to a Cr mask.

[0013] Particularly in the field of electronic components, what is required for printing large-area fine patterns is the absolute precision of the pattern (absolute positional precision). This is the printing pattern,
It is absolutely necessary when replacing with a photoresist pattern. Especially for aligning multiple patterns with high precision (
(generally called alignment), absolute precision equivalent to that of a Cr mask is required even for printed patterns.

[0014]

[Problems to be Solved by the Invention] However, in the case of screen printing, in the conventional printing method described above, even if a fine pattern can be formed by emulsion on the screen plate, there are problems such as ink smearing or crushing, and furthermore, printing Each time the fine pattern of the emulsion formed on the screen plate is stretched irregularly from screen to screen, there is a limit to maintaining the absolute accuracy of the printed pattern. Also,
In the case of intaglio offset printing and octopus printing, when the blanket or rubber-like elastic body is pressed against the intaglio or printing material surface, it stretches in one or two directions. For this reason, the ink pattern formed on the printing material also extends in one or two directions, resulting in a problem that the absolute accuracy of the printed pattern is reduced.

The present invention solves the above-mentioned conventional problems, and even when printing a fine pattern on a large area,
The printed pattern formed on the surface of the printing material is not easily distorted.
In other words, it is an object of the present invention to provide an offset screen printing method that prints and forms a print pattern while maintaining a predetermined absolute size without reducing the absolute accuracy of the print pattern.

[0016]

[Means for Solving the Problem] In order to achieve this object, the offset screen printing method of the present invention transfers an ink pattern formed on a plate onto the surface of an offset screen, which is a transfer body formed in the shape of a screen. After that,
It has a configuration in which it is transferred onto a printing medium.

[0017]

[Operation] With this configuration, the ink pattern formed on the plate is transferred onto the surface of the offset screen, which is a screen-shaped transfer member, and then onto the printing medium.

[0018]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of an offset screen printing apparatus according to a first embodiment of the present invention, and is intended to explain a case where the offset screen printing apparatus is applied to a letterpress (hereinafter simply referred to as a screen letterpress). In FIG. 1, 29 is an offset screen frame, and inside the offset screen frame 29 is an offset screen 30 on which a transfer body is formed.
is held under constant tension. Hereinafter, the portion composed of the offset screen 30 and the offset screen frame 29 will be referred to as an offset screen 37. 31 is an offset squeegee. 33 is a letterpress pattern, plate 3
It is formed on the surface of 2. Reference numeral 36 denotes a stand, on which a printing medium 34 and a plate 32 having a relief pattern 33 formed on its surface are fixed.

The operation of the screen letterpress printing apparatus constructed as above will be explained. First, ink is applied onto the letterpress pattern 33 using an ink supply device such as an ink roller widely used for letterpress printing. Next, an offset screen 37 is set at a certain distance on the letterpress pattern 33 with ink adhered to its surface, and the offset screen 30 is pressed against the letterpress pattern 33 using the offset squeegee 31. At this time, the ink adhering to the letterpress pattern 33 is on the side of the letterpress pattern 33 of the offset screen 30.
Formed as an ink pattern.

Next, the offset screen 37 is set on the printing medium 34 at a certain distance, and the offset squeegee 31 is used to press the screen 30 against the printing medium 34. At this time, the ink pattern formed on the printing medium 34 side of the offset screen 30 is transferred to the surface of the printing medium 34, and the printing pattern 3
5 will be formed.

[0021] Next, it will be explained in more detail. Since sufficient precision cannot be obtained with ordinary resin letterpress or metal letterpress, the letterpress used in the present invention was created using a Cr photomask for semiconductor production. First, a pattern was formed using a photoresist on a glass blank Cr mask (about 300 mm square), and the Cr was etched to obtain a predetermined Cr pattern. Next, this Cr mask was immersed in a dilute solution of fluoro-nitric acid, and the glass portion not covered with Cr was etched to form a letterpress. In this way, the effective printing area is 250 mm.
A letterpress printing plate was prepared which included a corner portion having a pattern pitch of 30 to 50 μm over almost the entire surface. Also, the offset screen was created as follows. First, a screen was placed on a 400 mm square screen frame, and commercially available silicone rubber was formed on the surface to a certain thickness. Specifically, an offset screen was created by setting a screen stretched at a constant tension in a mold, pouring silicone rubber into it, and curing it for 24 hours.

Printing was carried out as follows. First, ink was applied to the thus prepared letterpress using a commercially available rubber roller, and then an offset screen was set at a distance of about 1 mm on top of the ink-adhered letterpress. Next, the offset screen was pressed against the letterpress using an offset squeegee, and the ink pattern formed on the letterpress was transferred onto the surface of the offset screen. Next, this offset screen was set on a printing medium (using a glass plate) at a distance of about 1 mm. Next, the offset screen was similarly pressed onto the printing material using an offset squeegee, and the ink pattern formed on the offset screen was transferred onto the printing material.

For comparison, offset letterpress (also known as dry offset) printing was compared as a conventional example. The reason for choosing offset letterpress as the conventional example is as follows. First, in the case of general letterpress printing, especially when a metal or ceramic material is used as the letterpress material, a glass substrate or a ceramic substrate cannot be selected as the printing medium. On the other hand, if resin or the like is used as the letterpress material, sufficient precision cannot be achieved.

In an offset letterpress for comparison, a portion of the offset screen 37 shown in FIG. 1 is placed around the blanket cylinder 14 shown in FIG.
I chose the one with 3 wrapped around it. The results of comparing screen letterpress printing and offset letterpress printing will be explained using (Table 1). Note that in (Table 1), the pressure is the air pressure (kg/cm2) applied to the air cylinder that drives the blanket cylinder or offset squeegee. The reason why air pressure is used as a guideline is that it is extremely difficult to measure the printing pressure per unit area in the actual nip. Furthermore, even if it is measured accurately, if the thickness of the printing medium changes (particularly the thickness of an alumina substrate varies greatly), the printing pressure per unit area in the nip will change. The pattern direction was the rolling direction of the blanket cylinder vertically, and the longitudinal direction of the cylinder horizontally. The pattern elongation is letterpress pattern 10.
Expansion/contraction of pattern length on printing material per 0 mm (μm
) was evaluated. From Table 1, it can be seen that in the offset letterpress printing, as the air pressure increases, the pattern elongation increases in the vertical direction. This is because the blanket used in conventional offset letterpress printing is distorted by the printing pressure. Traditionally, this problem has been solved by adding compressible material (
This problem has been avoided by adding a layer (such as a sponge), but it has been a problem for some time when the printing material is a glass substrate or other material that does not have compressibility or ink absorbency.

However, in the case of screen letterpress printing, the pattern hardly changes both vertically and horizontally with respect to changes in air pressure. The reason why the pattern hardly changes horizontally or vertically in response to changes in air pressure is because the transfer body is stretched with uniform tension in each direction. This is thought to be because the principle is the same as above. Furthermore, even if the dimensional accuracy of the offset screen changes over time,
This is not a problem during the short time it takes for the ink pattern to be transferred from the plate to the offset screen and from the offset screen to the substrate. These results are also clear from the fact that even in the case of ordinary screen printing, the printed pattern hardly expands or contracts depending on the magnitude of the squeegee pressure.

As described above, it can be seen that by using the offset screen of the present invention, high precision printing can be performed regardless of the pressure. It goes without saying that the offset screen used in the present invention can be either a solid type or a compressible type depending on the purpose.

[0027] In Table 1, the absolute accuracy of the printed pattern by screen letterpress is ±10μ per 100mm.
m, but in reality, it was about ±10 μm even per 250 mm square of effective printing area. In addition, the measurement value of ±10 μm is due to the accuracy of the large Cr mask length measuring machine used to measure the absolute accuracy of the pattern, and the edges of the printed pattern are vague (not sharp) compared to the photoresist pattern. ) is considered to include measurement variation.

[0028]

[Table 1]

(Embodiment 2) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows the configuration of an offset screen printing apparatus according to a second embodiment of the present invention, and is intended to explain a case where the offset screen printing apparatus is applied to intaglio printing (hereinafter simply referred to as screen intaglio printing). In FIG. 2, 39 is an intaglio pattern, which is formed on the surface of the plate 38. stand 3
Reference numeral 6 fixes a printing medium 34 and a plate 38 having an intaglio pattern 39 formed on its surface.

The operation of the screen intaglio printing apparatus constructed as above will be explained. First, the inside of the intaglio pattern 39 is filled with ink using a ceramic squeegee. Next, the offset screen 37 is set at a certain distance on the intaglio plate whose inside is filled with ink, and the offset screen 30 is pressed against the intaglio pattern 39 using the offset squeegee 31. At this time, the ink filled inside the intaglio pattern 39 is formed on the intaglio 39 side of the offset screen 30 as an ink pattern. Next, the printing material 34
An offset screen 37b is set on top at a certain distance, and the offset screen 30 is pressed against the printing medium 34 using the offset squeegee 31. At this time, the printing material 3 of the offset screen 30
The ink pattern formed on the side 4 is transferred to the surface of the printing medium 34 to form a print pattern 35.

[0031] Next, it will be explained in more detail. Since sufficient accuracy cannot be obtained with ordinary resin intaglio plates or metal intaglio plates, the intaglio plate used in the present invention was created using a Cr photomask for semiconductor production. First, a pattern was formed using a photoresist on a glass blank Cr mask (about 300 mm square), and the Cr was etched to obtain a predetermined Cr pattern. Next, this Cr mask was immersed in a dilute solution of fluoro-nitric acid, and the glass portion not covered with Cr was etched to form an intaglio. In this way, the effective printing area is 250 mm.
An intaglio plate was prepared which included a portion with a pattern pitch of 30 to 50 μm on almost the entire surface at the corners. Also, the offset screen was created as follows. First, a screen was placed on a 400 mm square screen frame, and commercially available silicone rubber was formed on the surface to a certain thickness. Specifically, an offset screen was created by setting a screen stretched at a constant tension in a mold, pouring silicone rubber into it, and curing it for 24 hours.

Printing was carried out as follows. First, the intaglio plate thus prepared was filled with ink using a ceramic squeegee, and then an offset screen was set at a distance of about 1 mm on top of the ink-filled intaglio plate. Next, the offset screen was pressed against the intaglio using an offset squeegee, and the ink pattern formed in the intaglio was transferred onto the surface of the offset screen. Next, this offset screen was set on a printing medium (using a glass plate) at a distance of about 1 mm. Next, the offset screen was similarly pressed onto the printing material using an offset squeegee, and the ink pattern formed on the offset screen was transferred onto the printing material.

For comparison, a comparison was made with an offset intaglio plate as a conventional example. Here, as a conventional example, an offset intaglio plate shown in FIG. 7 was selected. In the offset intaglio for comparison, the part of the offset screen 37 shown in FIG. 2 is placed around the blanket cylinder 14 shown in FIG.
A comparison was made using a wrapped version (corresponding to Fig. 8). The results of comparing the screen intaglio and offset intaglio will be explained using (Table 2). In (Table 2),
The pressure is the air pressure (kg) applied to the air cylinder that drives the blanket cylinder or offset squeegee.
/cm2). The reason why air pressure is used as a guideline is that it is extremely difficult to measure the printing pressure per unit area in the actual nip. Furthermore, even if it is measured accurately, if the thickness of the printing medium changes (particularly the thickness of an alumina substrate varies greatly), the printing pressure per unit area in the nip will change. The pattern direction was the rolling direction of the blanket cylinder vertically, and the longitudinal direction of the cylinder horizontally. The elongation of the pattern was evaluated by the elongation (μm) of the pattern length on the printing substrate with respect to the intaglio pattern of 100 mm. From Table 2, it can be seen that in the offset intaglio plate, as the air pressure increases, the pattern elongation increases in the vertical direction. This is because the blanket used in conventional offset printing is distorted by the printing pressure. Conventionally, this problem has been avoided when the printing material is paper by inserting a layer of compressible material (sponge, etc.) inside the blanket. In the case of materials that do not have ink absorption properties, this has been a problem for some time.

However, in the case of screen intaglio printing, the pattern hardly changes both vertically and horizontally with respect to changes in air pressure. The reason why the pattern hardly changes vertically or horizontally in response to changes in air pressure is because the transfer body is stretched with uniform tension in each direction. This is thought to be because the principle is the same as above. Also, even if the dimensional accuracy of the offset screen changes over time,
This is not a problem during the short time it takes for the ink pattern to be transferred from the plate to the offset screen and from the offset screen to the substrate. These results are also clear from the fact that even in the case of ordinary screen printing, the printed pattern hardly expands or contracts depending on the magnitude of the squeegee pressure.

As described above, it can be seen that by using the offset screen of the present invention, highly accurate printing can be performed regardless of the pressure. It goes without saying that the offset screen used in the present invention can be either a solid type or a compressible type depending on the purpose.

[0036] In Table 2, the absolute accuracy of the printed pattern by screen letterpress is ±10μ per 100mm.
m, but in reality, it was about ±10 μm even per 250 mm square of effective printing area. In addition, the measurement value of ±10 μm is due to the accuracy of the large Cr mask length measuring machine used to measure the absolute accuracy of the pattern, and the edges of the printed pattern are vague (not sharp) compared to the photoresist pattern. ) is considered to include measurement variation.

[0037]

[Table 2]

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows the configuration of an offset screen printing apparatus according to a third embodiment of the present invention, and explains a case where the offset screen printing apparatus is applied to a screen plate. In FIG. 3, 30a and 30b are offset screen frames, and inside the offset screen frames 29a and 29b, there is an offset screen 30 on which a transfer body is formed.
a and 30b are stretched with a constant tension. Hereinafter, portions constituted by the offset screens 30a, 30b on which the transfer bodies are formed and the offset screen frames 29a, 29b will be referred to as offset screens 37a, 37b. Note that the offset screens 30a and 30b, the offset screen frames 29a and 29b, and the offset screens 37a and 37b are front and back. 31 is an offset squeegee. Reference numeral 36 denotes a stand, on which the printing medium 34 is fixed.

The operation of the offset screen printing apparatus constructed as above will be explained. First, inside the screen frame 40 for screen printing, a screen 41 for screen printing is stretched with a constant tension. A screen printing emulsion pattern 42 is formed on the surface of the screen printing screen 41. A screen plate 43 is constituted by the screen frame 40 for screen printing, the screen 41 for screen printing, and the emulsion pattern 42 for screen printing. Reference numeral 36 denotes a stand, on which the printing medium 34 is fixed.

The operation of the offset screen printing apparatus constructed as above will be explained. First, an ink pattern 45 was printed and formed on the surface of the offset screen 37 using a squeegee 44 and a screen printing screen 43. Next, the offset screen 37 on which the ink pattern 45 was formed was inverted to form an offset screen 37. Next, set the offset screen 37 a certain distance apart, and use the offset squeegee 31 to
The offset screen 30 is pressed against the printing medium 34 and squeezed. At this time, the offset screen 30
The ink pattern formed on the side of the printing medium 34 is transferred onto the surface of the printing medium 34c, forming a printed pattern 35c.

[0041] Next, it will be explained in more detail. The screen plate used in the present invention is a Cr photomask (pattern pitch 3
(contains a portion of 0 to 50 μm over almost the entire surface).

[0042] Also, an offset screen was created as follows. First, a screen was placed on a 400 mm square screen frame, and commercially available silicone rubber was formed on the surface to a certain thickness. Specifically, an offset screen was created by setting a screen stretched at a constant tension in a mold, pouring silicone rubber into it, and curing it for 24 hours. Here, the size of the screen plate and the frame size of the offset screen are made the same for ease of handling and to match each other's accuracy.

Printing was carried out as follows. First, an ink pattern 45 was printed on the surface of the offset screen thus created using a screen plate 43 and a squeegee 44. After this, the offset screen was turned over so that the ink pattern 45 faced the printing medium 34. Next, the offset screen was pressed against the printing material using an offset squeegee, and the ink pattern formed on the offset screen was transferred onto the printing material (using a glass plate).

As a conventional example for comparison, using the screen plate used in this example, it was printed using a normal screen printing method (that is, without using an offset screen).
An ink pattern was printed on a glass plate as a printing medium. Next, the fine pattern printing results obtained using (Table 3) will be explained. ○ in (Table 3)
△ indicates that there is almost no pattern defect on almost the entire surface, △ indicates that there is no pattern defect except for a part, and × indicates that there is pattern defect on almost the entire surface. As shown in (Table 3), the offset screen method is more effective than the conventional screen method.
It was possible to print a finer pitch. In the sample obtained by the offset screen method, almost no short-circuiting (ink did not bleed) occurred in the fine pitch area compared to the sample obtained by the conventional screen method. On the other hand, in samples produced using the conventional screen method, the fine pitch portions on the printing medium (glass substrate) were almost always short-circuited (the ink smeared). Next, when the offset screen used for printing by the offset screen method was observed, the portions where the ink was transferred from the screen plate were swollen by the ink solvent. As a result, in the case of the offset screen method, the solvent component in the printed ink is absorbed into the transfer body of the offset screen, as if the ink solvent soaked into the paper, so the ink hardly runs or smudges. As a result, it was found that transfer printing could be performed on the transfer object in that state. On the other hand, in the case of samples made using the conventional screen method, it was found that because the ink solvent did not penetrate into the glass substrate to be printed, the ink pattern ran or blurred in the fine pitch areas, resulting in short circuits.

Next, when the screen printing emulsion pattern of the screen plate used in the experiment was observed, it was found that the pitch was 30.
Almost the entire surface of the 60 μm pattern and a pitch of 90 μm
In some parts, the pattern was not missing. It is thought that because of this defective screen mask, printing could not be performed even with the offset screen method on almost the entire surface of the patterns with pitches of 30 and 60 μm and a portion of the patterns with pitch of 90 μm.

[0046]

[Table 3]

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 4 shows the configuration of an offset screen printing apparatus according to a fourth embodiment of the present invention, and is intended to explain a case where the offset screen printing apparatus is applied to lithography (hereinafter simply referred to as screen lithography). In FIG. 4, 47 is a lithographic pattern, which is formed on the surface of the lithographic plate 46. In FIG. A printing medium 34 and a lithographic plate 46 having a lithographic pattern 47 formed on its surface are fixed to the stand 36 .

The operation of the screen lithographic printing apparatus constructed as above will be explained. First, a very thin layer of dampening water is applied to the surface of the planographic pattern 47 using a dampening water roller, and then ink is applied using an ink roller. Next, the offset screen 37 is set at a certain distance on the planographic pattern 47 with ink adhered to its surface, and the offset screen 30 is pressed against the planographic pattern 47 using the offset squeegee 31. At this time, the ink deposited on the planographic pattern 47 is formed as an ink pattern on the planographic pattern 47 side of the offset screen 30. Next, an offset screen 37 is set on the printing medium 34 at a certain distance apart, and the offset squeegee 31 is used to press the screen 30 against the printing medium 34. At this time, the ink pattern formed on the side of the printing medium 34 of the offset screen 30 is transferred to the surface of the printing medium 34,
A print pattern 35 is formed.

[0049] Next, a more detailed explanation will be given. Since sufficient precision could not be obtained by exposing from a lithium film widely used for photolithography, a Cr photomask for semiconductor production was used as the exposure mask used in the present invention. This C
Using a photomask, commercially available PS was selected as a lithographic plate.
(Presensitized) After exposing an image pattern to the surface of the plate, a planographic plate was prepared using an automatic developing machine. In this way, the effective printing area is 250 mm square, and the pattern pitch is 30 to 50 μm.
A lithographic plate containing almost the whole area was created. The offset screen was created as follows. First 400
A screen was attached to a mm square screen frame, and a commercially available silicone rubber was formed on the surface to a certain thickness. Specifically, an offset screen was created by setting a screen stretched at a constant tension in a mold, pouring silicone rubber into it, and curing it for 24 hours.

Printing was carried out as follows. First, a commercially available dampening water was diluted and supplied to the planographic plate prepared in this way, and ink was applied using an ink roller. Then, an offset screen was placed at a distance of about 1 mm on top of the ink-covered planographic plate. I set it after setting it. Next, the offset screen was pressed against the lithographic plate using an offset squeegee, and the ink pattern formed on the surface of the lithographic plate was transferred and formed on the surface of the offset screen. Next, place this offset screen on the printing medium (using a glass plate) for about 1 m.
They were set at a distance of m. Next, the offset screen was similarly pressed onto the printing material using an offset squeegee, and the ink pattern formed on the offset screen was transferred onto the printing material.

For comparison, a comparison was made with offset lithographic printing as a conventional example. In an offset planographic plate as a conventional example, the offset screen 37 shown in FIG. 4 was formed by wrapping the blanket 13 around the blanket cylinder 14 shown in FIG. 8. The results of comparing screen lithography and offset lithography will be explained using (Table 4). Note that in (Table 4), the pressure is the air pressure (kg/cm2) applied to the air cylinder that drives the blanket cylinder or the offset squeegee. The reason why air pressure is used as a guideline is that it is extremely difficult to measure the printing pressure per unit area in the actual nip. Furthermore, even if it is measured accurately, if the thickness of the printing medium changes (particularly the thickness of an alumina substrate varies greatly), the printing pressure per unit area in the nip will change. The pattern direction was the rolling direction of the blanket cylinder vertically, and the longitudinal direction of the cylinder horizontally. The stretch of the pattern is 100mm for a letterpress pattern.
Expansion and contraction of pattern length on printing substrate (μm)
It was evaluated by From Table 4, it can be seen that in the case of offset planography, as the air pressure increases, the pattern elongation increases in the vertical direction. This is because the blanket used in conventional offset lithography is distorted by the printing pressure. Traditionally, this problem has been avoided when the printing material is paper by inserting a layer of compressible material (sponge, etc.) inside the blanket.
This has long been a problem when the printing material is a glass substrate or other material that does not have compressibility or ink absorption properties.

However, in the case of screen lithography, the pattern hardly changes both vertically and horizontally with respect to changes in air pressure. The reason why the pattern hardly changes vertically or horizontally in response to changes in air pressure is because the transfer body is stretched with uniform tension in each direction. This is thought to be because the principle is the same as above. Also, even if the dimensional accuracy of the offset screen changes over time,
This is not a problem during the short time it takes for the ink pattern to be transferred from the plate to the offset screen and from the offset screen to the substrate. These results are also clear from the fact that even in the case of ordinary screen printing, the printed pattern hardly expands or contracts depending on the magnitude of the squeegee pressure.

As described above, it can be seen that by using the offset screen of the present invention, highly accurate printing can be performed regardless of the pressure. It goes without saying that the offset screen used in the present invention can be either a solid type or a compressible type depending on the purpose.

[0054] In Table 4, the absolute accuracy of the printed pattern by screen letterpress is ±10μ per 100mm.
m, but in reality, it was about ±10 μm even per 250 mm square of effective printing area. In addition, the measurement value of ±10 μm is due to the accuracy of the large Cr mask length measuring machine used to measure the absolute accuracy of the pattern, and the edges of the printed pattern are vague (not sharp) compared to the photoresist pattern. ) is considered to include measurement variation.

[0055] In both the offset lithographic plate and the screen lithographic plate, the ink film thickness on the surface of the printing material was quite thin, with a maximum of 1 to 2 μm. Therefore, there is a problem in using this ink pattern as it is as an etching resist. From the above, in the case of ink patterns formed by planography, it is considered necessary to increase the ink film thickness by overprinting the same pattern multiple times. In order to print the same pattern multiple times, the absolute accuracy of the printed pattern becomes more important. For this reason as well, screen lithography is considered to be an effective method.

[0056]

[Table 4]

(Embodiment 5) A fifth embodiment of the present invention will be described below with reference to the drawings. Figure 5(a),
(b) shows the structure of an offset screen printing apparatus in a fifth embodiment of the present invention, and particularly shows the structure of an offset squeegee used for the offset screen. In FIG. 5, 48 is a plate-shaped offset squeegee, 49 is an offset screen, 50 is a printing medium, and 51 is a rod-shaped offset squeegee. Figure 5(a)
The arrow in FIG. 5B indicates the direction in which the plate-shaped offset squeegee 48 moves while sliding, and the arrow in FIG. 5B indicates the direction in which the bar-shaped offset squeegee 51 moves while rolling. In the offset screen printing of the present invention, the plate-shaped offset squeegee 48 is generally suitable, but the rod-shaped offset squeegee 51 is easier to use when it is desired to increase the printing pressure or depending on the type of offset screen. In particular, the rod-shaped offset squeegee 51 is advantageous in that it produces rolling friction, whereas the plate-shaped offset squeegee 48 produces sliding friction.

(Embodiment 6) A sixth embodiment of the present invention will be described below with reference to the drawings. Figure 6(a),
(b) shows the configuration of an offset screen printing apparatus in a sixth embodiment of the present invention, and in particular is a diagram showing the structure of the offset screen. In Figure 6, 5
2 is a plate-like support, 53a and 53b are transfer bodies, and 54 is a net-like support. In the offset screen printing of the present invention, FIG. 6(a) shows a transfer body 5 on the surface of a plate-like support 49.
3a is formed. FIG. 6(b) shows the net-like support 5
4 is embedded inside the transfer body 53b. In the present invention, by using a net-like support as the support, the transfer body can be more firmly fixed with high dimensional accuracy. It goes without saying that the structure of the offset screen used in the present invention can be arbitrarily selected from various screen forms used in various types of screen printing.

[0059]

As described above, the present invention transfers the ink pattern formed on the plate to the surface of the offset screen, which has a transfer material formed on the surface of the screen, and then transfers it onto the printing material. The ink pattern formed on the surface of the intaglio plate can be transferred and formed on the surface of the printing material without changing the accuracy of absolute dimensions.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the implementation status of an offset screen printing method in an embodiment of the present invention.

FIG. 2 is a perspective view showing the implementation status of the offset screen printing method in one embodiment of the present invention.

FIG. 3 is a perspective view showing the implementation status of an offset screen printing method in an embodiment of the present invention.

FIG. 4 is a perspective view showing the implementation status of the offset screen printing method in one embodiment of the present invention.

[Fig. 5] (a) and (b) are cross-sectional views showing the implementation status of the offset screen printing method in another embodiment of the present invention.

[Fig. 6] (a) and (b) are cross-sectional views showing the structure of an offset screen in the printing method of the present invention.

[Fig. 7] A perspective view illustrating an example of fine pattern printing by conventional screen printing.

[Fig. 8] A perspective view showing a conventional intaglio offset printing method.

[
FIG. 9 is a perspective view showing octopus printing, which is a conventional intaglio offset printing method.

[Figure 10] (a) and (b) are cross-sectional views to explain the elongation of the blanket.

[Figure 11] (a) and (b) are cross-sectional views to explain the elongation of the blanket.

[Explanation of symbols]

29, 29a, 29b Offset screen frame 30
, 30a, 30b Offset screen 31 Offset squeegee 32 Plate 33 Intaglio pattern 34 Printed material 35 Print pattern 36 Machine 37, 37a, 37b Offset screen 38
Plate 39 Intaglio 40 Screen frame 41 Screen for screen printing 42 Emulsion pattern for screen printing 43 Screen plate 44 Squeegee 45 Ink pattern 46 Planographic plate 47 Planographic pattern 48 Plate-shaped offset squeegee 49 Offset screen 50 Printing medium 51 Rod-shaped offset squeegee 52 Plate-shaped support bodies 53a, 53b transfer body 54 net-like support

Claims (3)

[Claims] 1. An offset screen printing method in which an ink pattern formed on a plate is transferred to the surface of an offset screen formed in the shape of a screen, and then transferred onto a printing medium. 2. The offset screen printing method according to claim 1, wherein the ink pattern transferred to the surface of the offset screen is formed on the printing material by pressing the ink pattern onto the printing material with a plate-shaped or rod-shaped squeegee. 3. The offset screen printing method according to claim 1, wherein the offset screen has a transfer body made of silicone resin formed on the surface of a plate-like or net-like support.