Patent Application
20080223234
The present invention relates to a method for producing a screen print excellent in printing precision.
Screen printing which forms a print film comprising ink, paste or the like on the surface of a material to be printed using a printing plate for screen printing (hereinafter sometimes referred to as merely “screen printing plate” or “printing plate”) can form fine patterns and has high mass-productivity, and hence is utilized in a wide variety of industrial fields. In general, screen printing is a method according to which using a screen mask constructed by stretching on a printing plate frame a mesh having openings closed with a resin (such as photosensitive emulsion film), an ink material is placed on the upper face of the screen mask and a squeegee is slid, thereby to squeeze out the ink material to the under side of the screen mask (substrate side) through the given openings formed in the screen mask to perform printing.
According to this screen printing, since the screen mask is flexible and besides the printing pressure is low, it is possible to carry out the printing on various printing materials, such as papers, fabrics, plastics, glasses, metals, and ceramics. Furthermore, since patterns formed by ink materials can be made thick, the screen printing is applied to production of electronic parts such as thick film IC (hybrid IC), printed-wiring boards, resistors and capacitors. The screen mask is produced by patterning a photosensitive emulsion film coated on a mesh by photolithographic technology. It is also produced by forming mesh patterns by selectively etching a metallic film by photolithographic technology.
General screen printing plates used for screen printing have a film-like screen having a support member comprising a gauze and a mask material having openings of a given shape and placed on the support member and a printing plate frame on which the screen is stretched. In printing, first the screen of the screen printing plate is put on the surface (the surface to be subjected to printing) of a suitable printing material, and ink or paste is placed on the screen. Then, a squeegee or the like is slid on the screen to squeeze out the paste or the like from the openings, whereby print patterns corresponding to the shape of openings or the arranged patterns when a plurality of openings can be formed on the surface of the printing material.
For example, in the field of production of electronic parts, the above screen printing is employed from the points of precision and mass-productivity. In this field, demand for forming finer print patterns in further higher precision increases because of recent development of technology to miniaturize the size of parts.
However, a printing plate frame has some distortion, and hence it is difficult to make a completely flat screen stretched on the printing plate frame. Moreover, since the distortion of the printing plate frame differs depending on the printing plate frame, the arranged patters of the openings on the screen stretched on the printing plate frame also delicately differ depending on the respective screen printing plates. Therefore, there is a problem that when screen printing is carried out using a plurality of screen printing plates differing in arranged patterns of openings, the print patterns on the respective resulting screen prints delicately differ from each other.
Recently, substrates which are to be printed tend to become larger, and hence the screen (screen printing plate) used for printing on large-sized substrates similarly tends to be large-sized. Therefore, due to increase of size of substrates or screen printing plate, the difference in print patterns of the respective resulting screen prints further becomes conspicuous.
The degree of difference in opening patterns of respective screen printing plates is not particularly significant as long as it is within a specific tolerance permissible for the respective prints obtained by the printing. However, with recent progress in technology, the printing precision must be further improved. Particularly, in the case of making laminated electronic parts by laminating screen prints, slight deviation of printing position between the screen prints results in more conspicuous deviation caused by lamination of the screen prints. Therefore, in order to make laminated electronic parts of higher performance, it is important that the degree of deviation in printing position on screen prints is within a permissible specific tolerance range.
As relevant prior art, there are disclosed a printing plate for screen printing in which the crossing portion of wire (gauze) constituting the support member of screen is fastened (Patent Document 1), a printing plate for screen printing in which linear expansion coefficient of printing plate frame is specified (Patent Document 2), a method of screen printing in the state of a given side of a printing plate frame being curved in a convex form (Patent Document 3), and a printing plate for screen printing provided with a printing plate frame deformable in both the outer and inner directions, and a method for producing prints using the same (Patent Document 4). However, even these printing plates for screen printing or printing method using them cannot sufficiently meet the demands that high printing precision should be assured and the degree of deviation in printing position should be within a permissible range, and thus further improvement is required.
Patent Document 1: JP-A-9-136394
Patent Document 2: JP-A-11-34288
Patent Document 3: JP-A-2000-318120
Patent Document 4: JP-A-2006-62241
The present invention has been made in an attempt to solve the above problems, and the object is to provide a method for producing a screen print according to which screen printing excellent in precision can be performed even when the material to be subjected to printing (printing material) is large and has a large printing area, and the resulting screen print is excellent in printing precision.
As a result of intensive research conducted by the inventors, it has been found that the above object can be attained by selecting and setting an optimum clearance between the printing material and the screen on the basis of the correlation of the clearance between the printing material and the screen with the degree of deviation in printing position of print pattern formed. Thus, the present invention has been accomplished.
That is, the present invention provides the following method for production of screen prints.
[1] A method for producing a screen print having a given print pattern formed thereon by sliding a squeegee in a given direction over a screen of a screen printing plate comprising the screen having a mask material with openings and a printing plate frame on which the screen is stretched, said screen being disposed above a printing material in the form of a flat plate in parallel to the printing material with keeping a given clearance therebetween, wherein a ratio (LP/LF) of a length (LP) of a side of the print pattern perpendicular to axis of the sliding direction of the squeegee to an internal size (LF) of a side of the printing plate frame perpendicular to axis of the sliding direction of the squeegee is 0.45 or more, and an optimum clearance between the printing material and the screen is selected and set on the basis of correlation between the clearance in the range of 0.1-2 mm and the degree of deviation in printing position of the print pattern.
[2] A method for producing a screen print described in the above [1], wherein the optimum clearance is selected and set according to the following procedures (1)-(5):
(1) a test printing is carried out with setting the clearance at values of optional two or more points in the range of 0.1-2 mm to obtain an initial trial print,
(2) the degree of deviation in printing position of the initial trial print is measured, and a calibration curve is obtained by plotting the degree of deviation in printing position against the clearance set above,
(3) a test printing is carried out with setting the clearance at value of optional one or more points in the range of 0.1-2 mm to obtain a subsequent trial print,
(4) the degree of deviation in printing position of the subsequent trial print is measured, the degree of deviation in printing position is plotted against the clearance set above, and then the calibration curve is offset to obtain a virtual calibration curve which passes the plotted points, and
(5) the optimum clearance at which the degree of deviation in printing position of the print pattern is the smallest is selected and set from the virtual calibration curve.
[3] A method for producing a screen print described in the above [1], wherein the optimum clearance is selected and set according to the following procedures (1a)-(3a):
(1a) a test printing is carried out with setting the clearance at values of optional two or more points in the range of 0.1-2 mm to obtain a trial print,
(2a) the degree of deviation in printing position of the trial print is measured, and a calibration curve is obtained by plotting the measured degree of deviation in printing position against the clearance set above, and
(3a) the optimum clearance at which the degree of deviation in printing position of the print pattern is the smallest is selected and set from the calibration curve.
[4] A method for producing a screen print described in any one of the above [1]-[3], wherein the clearance is 0.3-1.5 mm.
[5] A method for producing a screen print described in any one of the above [1]-[4], wherein the printing material is a fired ceramics substrate or a ceramics green sheet.
[6] A method for producing a screen print described in the above [5], wherein the printing material is a ceramics green sheet and the screen print is a constituent of a laminated substrate obtained by laminating a plurality of the prints.
According to the method for producing a screen print of the present invention, screen printing excellent in precision can be performed even on a large printing material having a large printing area and a screen print excellent in printing precision can be produced. Furthermore, according to the method for producing a screen print of the present invention, a screen print in which the degree of deviation in printing position is controlled to a specific range can be produced. Therefore, in the case of using the screen print obtained by the method for producing a screen print of the present invention, even when a plurality of the screen prints are laminated, total of deviation in printing position (deviation caused by lamination) can be controlled to a small value in a permissible range and thus laminated electronic parts of higher performance can be provided.
1: opening, 2: mask material, 3: screen, 4: printing plate frame, 5: screen printing plate, 6: air cylinder, 10: printing material, 11: printing plate frame holder, 12: printing stage, 30: print pattern, A-H: measuring points, CL: clearance, LF: internal size of printing plate frame, LP: length of one side of print pattern
The preferred embodiments of the present invention will be explained below. It will be understood that the present invention is not limited to the embodiments, and various changes and improvements may be made based on the common knowledge of those skilled in the art within the principle and scope of the invention.
Examples of the materials constituting the mask material are resins and metals. Openings of the shape and number corresponding to the desired print pattern are formed in the screen 3. For convenience,
As shown in
As shown in
In the method for producing a screen print according to this embodiment, the screen printing plate 5 is placed on the printing plate frame holder 11 in such a manner that the printing material 10 (printing surface of the printing material) and the screen 3 are in parallel to each other. In this case, the screen printing plate 5 is placed keeping a given clearance CL between the printing material 10 and the screen 3. It is necessary that the clearance CL is within the range of 0.1-2 mm, preferably 0.3-1.5 mm, especially preferably 0.4-1.5 mm, especially preferably 0.5-1.3 mm. By keeping the clearance CL in the range of 0.1-2 mm, there is obtained an advantage that the printing precision hardly decreases even when the printing is repeatedly carried out. If the clearance CL is less than 0.1 mm, defects such as blurring sometimes occur on the print pattern formed. On the other hand, if the clearance CL exceeds 2 mm, elongation of screen 3 caused by sliding of the squeegee is too much, and printing of high precision cannot be repeatedly performed.
Hitherto, in order to improve positional precision of print patterns formed by screen printing, there have been attempted mainly to devise and improve screen printing plates such as employment of lithography using glass mask or increasing of rigidity of meshes. On the other hand, adjustment of the clearance between printing material and screen has been considered to be a factor to control the shape of print patterns to be formed.
On the other hand, according to the present invention, it has been found that clearance within a given numerical range and degree of deviation in printing position of print pattern (degree of deviation from the desired design value) have a correlation, and utilizing the correlation, an optimum clearance at which the degree of deviation in printing position is smallest is selected, a printing material and a screen are disposed with keeping the selected optimum clearance, and screen printing is carried out. That is, the method for producing a screen print according to the present invention is a method which reduces the deviation in printing position of print pattern by adjusting the clearance between the printing material and the screen which has not been noticed as a means for improving the positional precision of the print pattern, and thus, according to the present invention it becomes possible to produce a screen print excellent in printing precision. The method for producing a screen print of the present invention will be explained in more detail attaching an importance to the method of selecting and setting of optimum clearance.
As specific methods for selecting and setting the optimum clearance in the present invention, mention may be made of a method according to the following procedures (1)-(5) (the first selecting and setting method) and a method according to the following procedures (1a)-(3a) (the second selecting and setting method).
(1) Test printing is carried out with setting the clearance at values of optional two or more points in the range of 0.1-2 mm to obtain an initial trial print (procedure (1)). Then, (2) the degree of deviation in printing position of the initial trial print is measured, and a calibration curve is prepared by plotting the measured degree of deviation in printing position against the clearance set above (procedure (2)).
In procedure (2), as shown in
Next, (3) test printing is carried out with setting the clearance at values of optional one or more points in the range of 0.1-2 mm to obtain a subsequent trial print (procedure (3)). In the procedure (3), there is used a screen printing plate which is the same as the screen printing plate used in procedure (2) in design specification, but different from the screen printing plate used in procedure (2) (different in individual). In many cases, the screen printing plates according to the same design specification show different degree of deviation in printing position respectively even when the clearance is the same because of individual difference. However, since the design specification is the same, it can be assumed that the correlations between the clearance and the degree of deviation in printing position are close to each other even in the case of different individuals.
The number of point of clearance set at the procedure (3) may be 1 point or more. However, setting of clearances of 3 points or more is not preferred because the procedure becomes complicated.
Thereafter, (4) degree of deviation in printing position of the subsequent trial print is measured, and the measured degree of deviation in printing position is plotted against the clearance set above, and then the calibration curve is offset to obtain a virtual calibration curve which passes the plotted points (procedure (4)). As shown in
Then, the calibration curve (1) prepared at the procedure (2) is offset in the direction of Y-axis to prepare virtual calibration curves (1) and (2) which pass the plotted points (black circle () and black triangle (▴) in
Then, (5) the optimum clearance at which the degree of deviation in printing position of the print pattern is the smallest is selected and set from the virtual calibration curve (procedure (5)). As shown in
(1a) Test printing is carried out with setting the clearance at values of optional two or more points in the range of 0.1-2 mm to obtain a trial print (procedure (1a)). Then, (2a) degree of deviation in printing position of the trial print in the procedure (1a) is measured, and a calibration curve is prepared by plotting the measured degree of deviation in printing position against the clearance set above (procedure (2a)). The number of the points of clearance set at the procedure (6) may be 2 points or more, and for obtaining the higher correlation with the degree of deviation in printing position, it is preferred to set clearances of 3 points or more, and it is more preferred to set clearances of 4-5 points. However, setting of clearances of 8 points or more is not preferred because the procedure becomes complicated.
In procedure (2a), as shown in
Then, (3a) the optimum clearance at which the degree of deviation in printing position of the print pattern is the smallest is selected from the calibration curve and is set (procedure (3a)). As shown in
As mentioned above, selecting and setting the optimum clearance by the first selecting and setting method is particularly effective when the screen printing plate used for preparation of calibration curve and the screen printing plate used for actual printing are of the same design specification (lot), but are different individuals. On the other hand, selecting and setting the optimum clearance by the second selecting and setting method are conducted on condition that the screen printing plate used for preparation of calibration curve and the screen printing plate used for actual printing are the same individuals.
Specifically, screen printing can be carried out in the following manner. That is, a given ink, paste or the like is put on screen 3 (cf.
According to the method for producing a screen print of the present invention, with using as a parameter a clearance between a printing material and a screen which has very high correlation with degree of deviation in printing position of print pattern, printing is carried out by selecting an optimum clearance, and hence printing of very high precision can be carried out. Therefore, there can be simply produced a screen print on which a given print pattern of high precision is formed. Furthermore, since a general screen printing plate and a general screen printing machine can be used without any special reconstruction, the method is high in general versatility and reduction of printing cost can be attained.
In the case of carrying out screen printing on an LTCC substrate (printing material) of 200 mm×200 mm (□200 mm, 40000 mm2) in area of printing surface, the print pattern is usually required to have a positional precision of about 5 μm in view of the inhibition of deviation caused by lamination of LTCC substrates. The method for producing a screen print of the present invention is particularly effective when the size (internal size) of printing plate frame (screen) is large, namely, 300 mm×300 mm (□300 mm, 90000 mm2)-400 mm×400 mm (□400 mm, 160000 mm2). With reference to the size of print pattern, the method is particularly effective when it is large size of 150 mm×150 mm (□150 mm, 22500 mm2) or more, and the size is more preferably 180 mm×180 mm (□180 mm, 32400 mm2) or more.
As screen prints obtained by the method for producing a screen print of the present invention, mention may be made of those which have circuits comprising at least dielectrics or conductors or have patterns having passive elements or active elements by virtue of the characteristics that the print having a highly precise print pattern may be easily produced. The passive elements include capacitor elements, etc. and the active elements include electro-mechanical transducers, etc.
When the printing material is a ceramics green sheet, the screen print is preferably a constituent of laminated substrate obtained by laminating a plurality of the screen prints. Specific examples of the laminated substrate are LTCC substrate, ceramic capacitor, laminate type piezoelectric actuator, NOx.oxygen sensor, etc. That is, according to the method for producing a screen print of the present invention, since prints having high precision printing patterns can be produced, when a plurality of the prints are laminated, LTCC substrates little in deviation of prints from each other caused by lamination can be easily produced. Furthermore, when the resulting LTCC substrates are fired, high performance circuit substrates on which circuits are very precisely disposed can be produced.
The present invention will be specifically explained by the following examples, which should not be construed as limiting the invention.
Using a screen printing plate 5 of 330 mm×330 mm in internal size as shown in
Using a screen printing plate which was the same in design specification (lot) as the screen printing plate used hereinbefore, but different in individual from the screen printing plate used hereinbefore, test printing was conducted in the state of setting the clearance at 0.7 mm to produce a second trial print. The degree of deviation in printing position of the resulting second trial print was measured.
Screen prints were produced in the same manner as in Example 1, except that screen printing plates of different lots were used.
Using a screen printing plate 5 of 330 mm×330 mm in internal size as shown in
From the intersection point of the degree of deviation in printing position=0 (mm) and the calibration curve (3), the optimum clearance (about 0.58 mm) for the screen printing plate used for producing the trial print according to the second selecting and setting method was read, and screen printing was carried out using the screen printing plate used hereinbefore as it was with setting the clearance between the printing material and the screen at about 0.58 mm to produce a screen print. The degree of deviation in printing position of the resulting screen print was measured, and a graph prepared by plotting the results of measurement is shown in
Screen prints were produced in the same manner as in Example 3, except that screen printing plates of different lots were used.
As shown in
The method for producing a screen print according to the present invention is suitable as a method for producing various electronic parts since the method can form fine patterns, is high in general versatility, and is suitable for mass-production. Furthermore, according to the method of the present invention, the degree of positional deviation of screen prints can be controlled to a certain range of permissible tolerance. Therefore, the method of the present invention exhibits particularly conspicuous effects in producing laminated electronic parts by laminating a plurality of screen prints.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-061968 | Mar 2007 | JP | national |
| 2007-282973 | Oct 2007 | JP | national |
