Patent ID: 8097160

Claim:
A method for manufacturing a solid-liquid separation flat membrane element, the method comprising: providing a support plate, a first membrane sheet, and a second membrane sheet, wherein: the support plate comprises: a water passing portion; a circumferential edge that defines a frame around a lateral edge of the water passing portion, the circumferential edge comprising a laser penetrable material; and a first surface configured to support the first membrane sheet, and a second surface configured to support the second membrane sheet, the first surface and second surface being positioned opposite to each other; the first and second membrane sheets each comprise a pigment; the first membrane sheet has a size and a shape that is larger than an entire inner perimeter of the circumferential edge along the first surface of the support plate, and is smaller than an entire outer perimeter of the circumferential edge along the first surface of the support plate; and the second membrane sheet has a size and a shape that is larger than the first membrane sheet; arranging the first membrane sheet on the first surface of the support plate so that the first membrane sheet overlaps the entire inner perimeter of the circumferential edge, but does not overlap an outer portion of the circumferential edge that is a part of the first surface; forming a weld between the first membrane sheet and the first surface of the support plate by emitting a laser through the second surface of the support plate to the first surface of the support plate and to the first membrane sheet, wherein the weld is formed around an entire periphery defined by the overlap between the first membrane sheet and the first surface of the support plate; arranging the second membrane sheet on the second surface of the support plate so that the second membrane sheet covers and overlaps an entire area on the second surface corresponding to an area on the first surface covered by the first membrane sheet welded to the first surface of the support plate; and forming a weld between the second membrane sheet and the second surface of the support plate by emitting a laser through the first surface of the support plate that is not covered by the first membrane sheet to the second surface of the support plate and to the second membrane sheet, wherein the weld is formed around an entire periphery defined by the overlap between the second membrane sheet and the second surface of the support plate.