Printing – Stenciling
Reexamination Certificate
1998-11-25
2001-05-29
Funk, Stephen R. (Department: 2854)
Printing
Stenciling
C101S425000
Reexamination Certificate
active
06237484
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a screen printing apparatus and, more particularly, to a screen printing apparatus which has a roller carrying cleaning paper for removing residue, such as paste, attached on a surface of a screen mask and paste attached inside openings of the mask pattern, using the cleaning paper.
When film (pattern) forming is repetitively carried out on substrates by screen printing, paste begins to remain on the side of the mask surface which is in contact with the substrate or within the openings in the mask. Thereby, a blur or dimness gradually appears in the pattern printed on the substrate, which causes a pattern short-circuit or a pattern line-break. Therefore, it is necessary to perform a cleaning operation for removing the attached paste residue (mask cleaning) by cleaning the mask which has been used for a certain number of printings.
For such mask cleaning, for example, Japanese Patent Application Laid-Open No. 63-59535 proposes a cleaning apparatus for a printing machine in which a cleaning roller is arranged in contact with the lower surface of a printing plate, and the cleaning roller is vibrated in the direction of its shaft using compressed air or the like to wipe off ink attached onto the lower surface of the printing plate. Japanese Patent Application Laid-Open No. 5-229108 proposes a cleaning apparatus for a printing machine which operates to wipe the lower side of a mask using a roll cloth in combination with a suction nozzle.
Since the openings of a pattern or the amount of clearance between patterns has been getting smaller in recent high-definition masks, problems occur as described below.
In the vibration cleaning roller method described above, if residue transferred onto the roller surface is not removed from the roller when the apparatus is operated without human intervention for a long time, the residue may be retransferred onto the mask during the continuous operation. Therefore, it is necessary for the cleaning roller to be provided with an adhesive force by increasing the friction coefficient of the cleaning roller surface. However, the cleaning roller cannot be vibrated at a high speed if the cleaning roller surface is provided with a large friction coefficient, and, accordingly, the residue attached on the inside of openings cannot be completely removed in a high-definition mask.
On the other hand, in the method which uses a roll cloth in combination with a suction nozzle, the cleaning apparatus can be operated without human intervention for a long time because the mask is cleaned continuously with a new cloth. However, there occurs a problem in that, since the winding direction of the roll cloth is unidirectional in order to perform cleaning always with a new cloth surface, residue tends to remain on the edge of the narrow opening portion of the mask pattern, particularly on the winding direction side, and so the residue cannot be completely removed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a screen cleaning apparatus which can maintain a good printing performance, even though the apparatus is being used automatically and continuously for a long time, by highly precisely removing paste remaining on the lower surface and inside the pattern openings of a mask having a high-definition and very narrow pattern openings.
In order to attain the above object, a screen printing apparatus in accordance with the present invention includes a mask having pattern openings; a squeegee for forming a pattern through the mask on a substrate, the squeegee being slid on an upper surface of the mask to print the pattern by forcing paste supplied on the upper surface of the mask onto the substrate placed under a lower surface of the mask through the pattern openings; cleaning paper to be brought in contact with the lower surface of the mask; a roller pressing against the lower surface of the mask with the cleaning paper interposed therebetween; roller moving means for moving the roller in a desired direction; and cleaning paper vibrating means for moving the cleaning paper relative to the moving direction of the roller.
The purpose of “moving the cleaning paper relative to the moving direction of the roller” is to provide a screen printing apparatus which can more certainly remove paste attached on the lower surface of the mask by increasing the total contact area of the cleaning paper with the lower surface of the mask, thereby to maintain a good printing performance. As to how to move the cleaning paper relative to the moving direction of the roller, one may employ a method wherein the cleaning paper itself is vibrated, a method wherein the cleaning paper is vibrated indirectly by vibrating the roller and a combination of both. Thus, as to the concept of a “cleaning paper vibrating means” which moves the cleaning paper relative to the moving direction of the roller, either a “roller vibrating means” or a “cleaning paper moving means” are available.
A screen printing apparatus in accordance with the present invention is characterized in that a roller is pressed against the lower surface of a mask with the cleaning paper interposed therebetween and with the cleaning paper being vibrated directly or indirectly, so that the cleaning paper is moved in contact with the mask in a wave-form pattern on the lower surface of the mask. The combined movement may be performed by providing independent movement of the roller and movement of the cleaning paper, or by causing the movement of the cleaning paper to follow the movement of the roller.
Further, another feature of a screen printing apparatus in accordance with the present invention resides in the fact that the screen printing apparatus comprises a control means for adjusting the moving speed of the roller moving means or the vibration speed of a cleaning paper vibrating means corresponding to the distribution of openings in the mask or the material property of the paste being used.
In detail, the present invention provides the apparatuses described below.
The screen printing apparatus in accordance with the present invention forms a pattern on a substrate by sliding a squeegee on an upper surface of a mask having pattern openings to print the pattern by forcing paste supplied on the upper surface of the mask through the pattern openings and onto the substrate placed under a lower surface of the mask, the screen printing apparatus comprising a roller moving means for moving a roller, which presses against the lower surface of the mask with cleaning paper interposed therebetween in contact with the lower surface of the mask, in a desired direction; and a cleaning paper vibrating means for moving or vibrating the cleaning paper in a direction perpendicular to the moving direction of the roller. The cleaning paper vibrating means may be an independently provided apparatus, or the cleaning paper vibrating means may be constructed so to generate a vibration formed by movements of the roller in both X-axis and Y-axis directions or by movement of the roller in the direction of the X-axis and movement of the cleaning paper in the direction of the Y-axis. By doing so, the desired construction can be obtained, since the movements or the vibrations can be composed.
It is preferable when the roller is formed of an elastic body. It is also preferable when the screen printing apparatus comprises a control means for adjusting the speed of operation of the roller moving means, or the speed of movement of the cleaning paper vibrating means, or the speed of vibration of the cleaning paper vibrating means.
It is preferable when the screen printing apparatus comprises a sponge member soaked with a solvent; and a solvent storing tank is provided for supplying the solvent to the sponge member. It is also preferable when the screen printing apparatus comprises a pallet-shaped member, which is in contact with a surface of the mask and moves together with the roller; and a paste residue intake port movable together with the pallet-shaped member while maintaining a ga
Abe Isao
Homma Makoto
Mukai Noriaki
Sato Mitsuhiko
Antonelli Terry Stout & Kraus LLP
Funk Stephen R.
Hitachi Techno Engineering Co. Ltd.
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