Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product
Reexamination Certificate
2000-07-10
2001-11-27
Heinrich, Samuel M. (Department: 1725)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
C219S121850, C219S121680, C430S416000, C264S482000, C428S098000, C428S203000, C065S111000, C065SDIG003
Reexamination Certificate
active
06322958
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a marking method using a laser beam and a laser marking apparatus, and more particularly to a laser marking method and apparatus for forming a marker in a transparent member to be worked.
BACKGROUND ART
A method is known by which the surface of a work member such as a transparent glass substrate is marked by utilizing ablation by a laser beam. With this method, fine cracks are formed on the surface of a work member and broken pieces are sometimes mixed with another work member on a manufacture line. Since deposits called debris are formed near the marked area, it becomes necessary to clean and remove such deposits.
A method is disclosed in JP-A-HEI-3-124486 by which a marker is formed in a work member by converging a laser beam at the inside thereof, without damaging the surface of the work member. With this method, since the surface of a work member is not damaged, it is possible to prevent formation of fine cracks and attachment of debris.
According to the method disclosed in JP-HEI-A-3-124486, when the energy density of a laser beam exceeds a breakdown threshold value of a work member, at the converging point of the laser beam or in its nearby area, fine parts of the work member are destructed and a marker is formed. By disposing fine markers in two- or three-dimensionally, characters or figures can be drawn. By narrowing a pitch between disposed fine markers, the contrast of characters or figures can be improved.
With this method, however, it is difficult to control the shape of a fine marker formed through destruction of a work member. The shapes of markers become, therefore, irregular. If adjacent markers contact each other, the mechanical strength of the work member lowers. It is therefore preferable to dispose markers in a dispersed manner. In order not to make adjacent markers contact each other even if the shapes of markers are irregular, it is necessary to increase the pitch between adjacent markers and provide a margin to some extent.
DISCLOSURE OF THE INVENTION
It is an object of the present invention to provide a marking method and apparatus capable of improving controllability of marker shapes to be formed by a laser beam.
It is another object of the present invention to provide a transparent member with markers formed therein and having high contrast.
According to one aspect of the present invention, there is provided a marking method comprising the steps of: radiating a laser beam from a laser source; and converging the laser beam radiated from the laser source at a converging point inside of a work member to form cracks at the converging point and in its nearby area, by making a cross section of the laser beam at the converging point have a shape long in a first direction perpendicular to an optical axis of the laser beam.
The optical characteristics of the work member change at the converging point of the laser beam and in its nearby area. The portion whose optical characteristics changed has a linear shape along the optical axis of the laser beam. Areal (Plane-like) cracks extend from the linear part in the first direction. The linear part with changed optical characteristics and areal cracks can be visually recognized.
According to another aspect of the present invention, there is provided a marking apparatus comprising: a laser source for radiating a laser beam; beam shaping means for shaping a shape of a cross section of the laser beam radiated from the laser source so as to make the cross section have a shape long in a first direction perpendicular to an optical axis of the laser beam; optical converging means for converging the laser beam shaped by the beam shaping means; and holding means for holding a work member so as to set a converging point of the laser beam converged by the optical converging means to a position inside of the work member.
As the laser beam having a shape long in the first direction is converged, the cross section of the laser beam at the converging point is made to have the shape long in a direction perpendicular to the first direction. Therefore, a marker having the linear part and areal cracks can be formed.
According to another aspect of the present invention, there is provided a marked member comprising: a transparent member; and markers formed in the transparent member, each of the markers including a linear portion having optical characteristics different from a nearby region and a pair of areal cracks extending from the linear portion in opposite directions.
The linear part and areal cracks can be visually recognized. They can be visually recognized easily particularly along a direction crossing a virtual plane along the areal cracks.
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Arent Fox Kintner & Plotkin & Kahn, PLLC
Heinrich Samuel M.
Sumitomo Heavy Industrie's, Ltd.
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