An ink jet printing apparatus and method using a pressure generating device to induce surface waves in an ink meniscus

Abstract

Characteristics of a droplet ejection apparatus are changed depending on the shape or cone angle of the main chamber of the apparatus or the diameter of the ejection aperture of the apparatus and thus, the apparatus may not be normally operated depending on the setting of the shape, angle, or diameter. Therefore, in the case of the first invention, the shape of the ejection aperture is formed to be circular or regular polygonal so that surface waves are synthesized at the central portion of the ejection aperture. Moreover, the cone angle of the main chamber is set to 65° or less from the plane vertical to the droplet ejecting direction and the diameter of the ejection aperture is set to a value 1.25 times or more larger than a desired droplet diameter. The droplet diameter and droplet speed are changed depending on the temperature of a liquid to be ejected. Therefore, it is necessary to decide an optimum liquid temperature for obtaining a desired droplet diameter and speed. Moreover, it is necessary to keep the optimum temperature. Therefore, in the case of the second invention, a heater for heating a liquid to be ejected and a temperature sensor are used so as to keep the temperature of the liquid constant. The diameter of a droplet to be ejected is changed depending on the main chamber pressurizing time. Therefore, it is necessary to decide an optimum pressurizing time for obtaining a desired droplet diameter. Therefore, in the case of the third invention, droplet diameters are measured while variously changing widths of a single pulse for deciding a pressurizing time. It is necessary that a droplet diameter for obtaining a resolution of 300 dpi or higher is 60 to 70 μm or less. Therefore, it is clarified that the width of a single pulse must be 100 μS or less. Droplet ejection states may be variously changed depending on the single-pulse waveform to be applied to a droplet ejection apparatus and thereby, the change of the states may cause a trouble in control. To solve the above problem, it is most suitable to apply a sine-wave single pulse having a single frequency component. However, to directly generate the sine-wave single pulse, a complex and expensive apparatus is necessary. Therefore, in the case of the fourth invention, a triangular, rectangular, or trapezoidal wave is generated and the signal of the wave is passed through a low-pass filter to fetch a sine wave which is the basic wave of the signal.

Dependencies are inferred from the claim text.