Electric heating – Metal heating – By arc
Patent
1996-08-07
1998-06-02
Walberg, Teresa J.
Electric heating
Metal heating
By arc
21912185, 349 2, B23K 2606
Patent
active
057603707
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an image display method for a liquid crystal mask marker, and more particularly to an image display method for a liquid crystal mask marker which can clearly display and imprint mask images, such as product numbers and patterns, on the surfaces of nonmetallic articles, such as IC chips, or metallic articles.
BACKGROUND ART
A prior art liquid crystal mask marker will be described with reference to FIG. 5. A high-density energy light beam R1 emitted from a laser oscillator 1, for example, is irradiated onto a display image of a liquid crystal mask 4, and a light beam R2 transmitted through the mask 4 is then irradiated onto a workpiece surface 6 for imprinting the image on the workpiece surface 6. According to Japanese Patent Laid-Open No. 5-210358, for example, the display image of the liquid crystal mask 4 is rewritten with a controller 8 in such a manner that, as shown in FIG. 6B, potentials of all of the picture elements are grounded as indicated by S, i.e., voltages applied to all of the picture elements are made zero, and the step of displaying the next display image P is then started (this rewriting process will be hereinafter referred to as "process of grounding potentials of all of the picture elements").
With the process of grounding potentials of all of the picture elements, there occur phenomena, called an afterimage and a counter afterimage described later, in the display image of the liquid crystal mask 4 immediately after the rewriting. Referring to FIGS. 7A to 7C, for example, when a solid black circle A (FIG. 7A) is marked on the workpiece surface 6 and, after rewriting the display image of the liquid crystal mask 4, a solid black rectangle B (FIG. 7B) is marked on the workpiece surface 6, a rectangle C appears, together with an afterimage A2, as the image of the liquid crystal mask 4 immediately after the rewriting, as shown in FIG. 7C. In addition, the rectangle C is divided into a clear area A1 and an unclear area B1. This unclear area B1 is defined here as "counter afterimage". Incidentally, the letter B indicates an area of the image other than the circle A.
The afterimage A2 and the counter afterimage B1 will disappear naturally with the elapse of time. Therefore, those phenomena are practically not problematic in conventional liquid crystal mask markers which are much inferior in marking speed and image sharpness to the present liquid crystal mask marker described later. More specifically, in conventional liquid crystal mask markers, the high-density energy light beam R1 is irradiated onto the image including both the afterimage A2 and the counter afterimage B1. But when the image is imprinted on the workpiece surface, the counter afterimage B1 does not raise a problem because the irradiation time is long. On the other hand, the afterimage A1 does not appear as imprinted on the workpiece surface by irradiating the high-density energy light beam R1 onto the image in which the afterimage A2 has disappeared. It is to be noted that the counter afterimage B1 will not also appear as imprinted on the workpiece surface if the high-density energy light beam R1 is, as with the above case of the afterimage A2, irradiated onto the image in which the counter afterimage B1 has disappeared. In practice, however, no considerations have been paid so far to the foregoing point and the level of sharpness of the image imprinted does not yet deserve discussing in the present state of art.
Meanwhile, the applicant has previously proposed several liquid crystal mask markers (see, e.g., Japanese Patent Laid-Open No. 5-42379) wherein the rewriting time and the image display time are each on the order of about 30 msec at the minimum, i.e., an image is displayed and rewritten at very high speeds, while ensuring a sharpness of the image imprinted. Accordingly, the irradiation time of a high-density energy light beam (i.e., the marking time) during the image display time is even shorter. In the proposed liquid crystal mask markers, not only the afterimage A2 an
REFERENCES:
patent: 4734558 (1988-03-01), Nakano et al.
patent: 4818835 (1989-04-01), Kuwabara et al.
patent: 5157235 (1992-10-01), Okumura et al.
patent: 5309273 (1994-05-01), Mori et al.
Matsumura Yukinori
Tsuda Yukihiro
Komatsu Ltd.
Mills Gregory L.
Walberg Teresa J.
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