METHOD FOR DETERMINING CUTTING POSITIONS OF OPTICAL FILM

1 . A method for determining cutting positions of a lengthwise extending optical film to form a plurality of optical film sheet pieces by cutting the optical film along a width direction of the optical film with intervals in a length direction of the optical film, the method comprising the steps of:

(a) previously acquiring information on defect positions of the optical film based on the length direction of the optical film;

(b) dividing a whole area of the optical film into a plurality of relatively large calculation areas for deriving a plurality of cutting positions, based on a normal cutting distance condition and minimum cutting distance condition in the length direction of the optical film, and the information on the defect positions of the optical film; and

(c) determining the cutting positions from an area, in which none of the cutting positions are determined in the length direction of the optical film, among the plurality of large calculation areas.

2 . The method of claim 1 , wherein step (b) comprises the steps of:

(b-1) setting a normal area, in which at least one normal cutting distance may be included, among a determination target area between any one of a first setting position and a defect and a defect adjacent to the any one, as a first relatively small calculation area for deriving the cutting positions, and if defective areas, in which the normal cutting distance may not be included, among a determination target area between any one of a first setting position and a defect and a defect adjacent to the any one, are consecutive to each other, setting the normal area, including all the consecutive defective areas, as a second relatively small calculation area for deriving the cutting positions;

(b-2) calculating the maximum quantity of normal cutting in which the normal cutting distances may be included to the maximum in the small calculation area set through step (b-1); and

(b-3) for a subsequent relatively small calculation area, including any one relatively small calculation area, classifying as a relatively large calculation area an area including up to the first relatively small calculation area, in which a small calculation area remainder obtained by subtracting the product of the normal cutting distance and the maximum quality of normal cutting from the length of the relatively small calculation area is smaller than the minimum cutting distance.

3 . The method of claim 2 , wherein

the cutting positions are determined so that they maintain a distance equal to or greater than a predetermined minimum spacing distance from the defects, and

the maximum quantity of normal cutting in step (b-2) is an integer portion calculated by dividing a value, obtained by subtracting twice the minimum spacing distance from the length of the relatively small calculation area, by the normal cutting distance.

4 . The method of claim 2 , wherein step (c) comprises selecting the relatively small calculation area from among the plurality of relatively small calculation areas in the relatively large calculation area in the order in which the relatively small calculation area remainder is smaller, and determining the cutting positions in the selected relatively small calculation area.

5 . The method of claim 4 , wherein step (c) comprises step (c-1) of determining the cutting positions in the relatively selected small calculation area, based on the small calculation area remainder of each of the selected relatively small calculation area, the previous relatively small calculation area and the subsequent relatively small calculation area, and the minimum cutting distance, in the length direction of the optical film.

6 . The method of claim 5 , wherein step (c) comprises step (c-2) of substituting a value, obtained by subtracting the distance between a defect present between the selected relatively small calculation area and the previous relatively small calculation area and the final cutting position in the previous relatively small calculation area from the small calculation area remainder of the previous relatively small calculation area, with the previous small calculation area remainder, if the cutting positions in the relatively small calculation area before the selected relatively small calculation area have been determined in the length direction of the optical film, and

step (c-1) is performed after step (c-2).

7 . The method of claim 5 , wherein step (c) comprises step (c-3) of substituting a value, obtained by subtracting the distance between a defect present between the selected relatively small calculation area and the subsequent small calculation area and the first cutting position in the subsequent relatively small calculation area from the small calculation area remainder of the subsequent relatively small calculation area, with the subsequent relatively small calculation area remainder, if the cutting positions in the relatively small calculation area subsequent to the selected relatively small calculation area have been determined in the length direction of the optical film, and

step (c-1) is performed after step (c-3).

8 . The method of claim 1 , wherein the cutting positions in step (c) are determined so that the distance between the cutting positions adjacent to each other does not exceed a predetermined maximum cutting distance, and

the maximum cutting distance is the same as the normal cutting distance.