Separation lines are formed in a glass plate having first and second main surfaces by irradiating with laser light. The separation lines are configured of a product line corresponding to an outline of a glass article to be separated; and a release line. The product line includes a first in-plane void array configured of in-plane voids arranged on the first main surface; and internal void arrays for product line, each having an in-plane void. The release line includes internal void arrays for release line. A maximum length of the internal void array for product line L.sub.1max is equal to a maximum length of the internal void array for release line L.sub.2max, and a minimum length of the internal void array for product line L.sub.1min is greater than a minimum length of the internal void array for release line L.sub.2min; or the length L.sub.1max is greater than the length L.sub.2max.

Separation lines are formed in a glass plate having first and second main surfaces by irradiating with laser light. The separation lines are configured of a product line corresponding to an outline of a glass article to be separated; and a release line. The product line includes a first in-plane void array configured of in-plane voids arranged on the first main surface; and internal void arrays for product line, each having an in-plane void. The release line includes internal void arrays for release line. A maximum length of the internal void array for product line L.sub.1max is equal to a maximum length of the internal void array for release line L.sub.2max, and a minimum length of the internal void array for product line L.sub.1min is greater than a minimum length of the internal void array for release line L.sub.2min; or the length L.sub.1max is greater than the length L.sub.2max.

A method for separating and releasing a closed-form piece from a workpiece made of a brittle material is disclosed. A first pulsed laser-beam creates defects along the outline of the closed-form piece. A second laser-beam selectively heats the closed-form piece for a first time that is sufficient to initiate cracking between the defects. The heating is stopped for a period sufficiently long for the cracks to propagate completely between the defects. The second laser-beam is applied for a second time that causes melting and deformation of the closed-form piece. The deformation opens a gap between the closed-form piece and the rest of the workpiece, thereby allowing release of the closed-form piece.

A method for separating and releasing a closed-form piece from a workpiece made of a brittle material is disclosed. A first pulsed laser-beam creates defects along the outline of the closed-form piece. A second laser-beam selectively heats the closed-form piece for a first time that is sufficient to initiate cracking between the defects. The heating is stopped for a period sufficiently long for the cracks to propagate completely between the defects. The second laser-beam is applied for a second time that causes melting and deformation of the closed-form piece. The deformation opens a gap between the closed-form piece and the rest of the workpiece, thereby allowing release of the closed-form piece.

There is provided a laser processing device that performs laser processing on an object made of a birefringent material, the device including: a light source that outputs laser light; a spatial light modulator that modulates the laser light output from the light source; a focusing lens that focuses the laser light toward the object; and a polarized light component control unit that is a function of the spatial light modulator to control polarized light components of the laser light such that the laser light is focused on one point in the object in a Z direction (optical axis direction).

There is provided a laser processing device that performs laser processing on an object made of a birefringent material, the device including: a light source that outputs laser light; a spatial light modulator that modulates the laser light output from the light source; a focusing lens that focuses the laser light toward the object; and a polarized light component control unit that is a function of the spatial light modulator to control polarized light components of the laser light such that the laser light is focused on one point in the object in a Z direction (optical axis direction).

A crack detection method includes a crack forming step of applying a laser beam to a plate-shaped workpiece that has a first side and a second side opposite to the first side linearly from the first side with a focal point of the laser beam positioned inside the workpiece, the laser beam being of a wavelength having a transmitting property to the workpiece, to thereby form a modified layer inside the workpiece and further form a crack extending from the modified layer toward the second side, a coating material applying step of applying a coating material to the second side, and a crack detecting step of detecting the crack by searching for a portion where the coating material is linearly repelled.

An ultrasonic wave is applied to an upper surface of an ingot via a liquid layer, in a state in which an outer circumferential region of a lower surface of the ingot is sucked. A lower side around an outer circumferential arc-shaped portion of the lower surface of the ingot is open so that liquid that serves as a medium of the ultrasonic wave does not collect around the outer circumferential arc-shaped portion of the lower surface of the ingot. As a result, a peel-off layer formed in the ingot is not immersed in liquid when an ultrasonic wave is applied to the upper surface of the ingot via the liquid layer. Consequently, even when the ingot becomes thin, the ingot can be separated at the peel-off layer, and a wafer can be peeled off from the ingot.

An ultrasonic wave is applied to an upper surface of an ingot via a liquid layer, in a state in which an outer circumferential region of a lower surface of the ingot is sucked. A lower side around an outer circumferential arc-shaped portion of the lower surface of the ingot is open so that liquid that serves as a medium of the ultrasonic wave does not collect around the outer circumferential arc-shaped portion of the lower surface of the ingot. As a result, a peel-off layer formed in the ingot is not immersed in liquid when an ultrasonic wave is applied to the upper surface of the ingot via the liquid layer. Consequently, even when the ingot becomes thin, the ingot can be separated at the peel-off layer, and a wafer can be peeled off from the ingot.

Methods of separating a glass web include exposing a separation path on the glass web to a laser beam that produces thermal stress along the separation path without damaging the glass web. The methods further include redirecting a portion of the laser beam to create a defect on the separation path while the separation path is under thermal stress produced during the exposing the separation path on the glass web to the laser beam, whereupon the glass web separates along the separation path in response to creating the defect. Apparatus are further provided for separating a glass web with at least one laser beam generator that produces a laser beam to heat a separation path and a mirror configured to reflect an end portion of the laser beam to create a defect at a location of the separation path on the glass web.