Investigation on synchronization of the offset printing process for fine patterning and precision overlay

Abstract

Offset printing processes are promising candidates for producing printed electronics due to their capacity for fine patterning and suitability for mass production. To print high-resolution patterns with good overlay using offset printing, the velocities of two contact surfaces, which ink is transferred between, should be synchronized perfectly. However, an exact velocity of the contact surfaces is unknown due to several imperfections, including tolerances, blanket swelling, and velocity ripple, which prevents the system from being operated in the synchronized condition. In this paper, a novel method of measurement based on the sticking model of friction force was proposed to determine the best synchronized condition, i.e., the condition in which the rate of synchronization error is minimized. It was verified by experiment that the friction force can accurately represent the rate of synchronization error. Based on the measurement results of the synchronization error, the allowable margin of synchronization error when printing high-resolution patterns was investigated experimentally using reverse offset printing. There is a region where the patterning performance is unchanged even though the synchronization error is varied, and this may be viewed as indirect evidence that printability performance is secured when there is no slip at the contact interface. To understand what happens at the contact surfaces during ink transfer, the deformation model of the blanket's surface was developed. The model estimates how much deformation on the blanket's surface can be borne by the synchronization error when there is no slip at the contact interface. In addition, the model shows that the synchronization error results in scale variation in the machine direction (MD), which means that the printing registration in the MD can be adjusted actively by controlling the synchronization if there is a sufficient margin of synchronization error to guarantee printability. The effect of synchronization on the printing registration was verified experimentally using gravure offset printing. The variations in synchronization result in the differences in the MD scale, and the measured MD scale matches exactly with the modeled MD scale.

Selective Light-Induced Patterning of Carbon Nanotube/Silver Nanoparticle Composite To Produce Extremely Flexible Conductive Electrodes

“…Conventional lithographic techniques involving UV irradiation and chemical etching are widely used to produce microscale and nanoscale patterns; however, these methods have several disadvantages, including the use of expensive equipment, complex processes with multiple steps, and a low throughput. − In addition, the patterning of composite materials consisting of organic and inorganic components is difficult with such techniques because the etchant is generally designed to selectively react with one component (e.g., metal) of the composite. As an alternative to optical lithography, solution-based printing approaches such as inkjet printing, screen printing, transfer printing, gravure (offset) printing, and reverse-offset printing have been adopted for fabrication of composite electrode patterns. − However, despite their tremendous technical successes, issues remain unsolved, such as the imperfect control of defects and pattern shapes, low patterning resolution, and poor uniformity over large areas. In this regard, it is critical to develop more practical and simple pattering routes to obtain composite-based highly reliable flexible conductive features that are commercially viable for the next-generation electronics industry.…”

Push-pull process for contact defect-free patterning in reverse offset printing

“…Further, we anticipate that our method may be useful for applications that require a high overlay accuracy, as a finite indentation of the blanket in the conventional pushonly process often causes a pattern deformation because of a mismatch in the rotational and translational motions of the blanket roller and the stage. This is due to the reduced superficial speed of the compressed blanket roller [35], as well as a pattern-width reduction due to undesired contact at the edge of the cliché's grooves [29]. A roll-to-sheet printing was adopted in the present study and thus a further investigation is required to apply for a roll-to-roll printing.…”

Escape dynamics of liquid droplets confined between soft interfaces: non-inertial coalescence cascades

“…The behavior of liquid confined between solids, of which at least one is soft and elastomeric, is important in a number of technological applications such as aquaplaning, [1][2][3][4][5][6][7][8][9][10][11] tribology, printing [12][13][14] and adhesion. [15][16][17][18][19][20] The stability of liquid films is highly desirable in tribological applications such as contact lenses and cartilage joints, where direct solid on solid contact would induce wear and frictional heating.…”