GB/T 20314-2017Thin float glass for liquid crystal display ( LCD ) applications (English PDF)

3.1 TN-LCD

Liquid crystal display of the twisted nematic type.

3.2 STN-LCD

Liquid crystal display of the super-twisted nematic type.

3.3 Edge defects

Cracks, bulges, missing parts, etc. of glass pane, including chips, edge irregularities, missing angles and so on.

3.4 Micro-waveness

Degree of tiny unevenness of glass pane.

3.5 Warp

Misfit between glass surface and reference plane, which is expressed as degree of warp.

6.1 Dimensional deviation

As specified in 6.1 of GB 11614-2009.

6.2 Diagonal difference

Measure the length of two diagonal lines as specified in 6.2 of GB 11614-2009. The percentage of the difference of diagonal line lengths to the average length of diagonal lines is the diagonal difference.

6.3 Thickness deviation

Use an external micrometer of division value 0.001 mm as specified in GB/T 1216 to measure 5 points in the direction perpendicular to the stretching direction of glass pane, including one point inwards about 15 mm from the edge respectively and three points equally dividing the distance between the two points. Round the measure values off to the third decimal place. The difference between actual value and nominal thickness is the thickness deviation.

6.4 Thick-thin difference

Use the same method specified in 6.3 to measure the thicknesses of 5 different points of a glass pane; calculate the difference between its maximum value and minimum value.

6.5 Appearance quality

6.5.1 Point defects, intensity of point defects, scratches, optical spot distortions, lines, surface cracks and surface stains

6.5.1.1 After washing and drying, transfer sample to a dark room of 100,000 grade's cleanliness. The light intensity of the test point is 2,500 lx; the distances from the light source and the observing position are 300 mm respectively; observe sample at any random angle against the matt black-white background, through reflected light [as shown in Figure 1a)] and transmission light [as shown in Figure 1b)].

6.5.1.2 On an ambient light detector, 300 mm apart from the test point, observe sample at any random angle.

6.5.1.3 Use a microscope of division value 0.001 mm as specified in JB/T 2369 to measure the maximum dimensions of point defects and the widths of scratches.

7.2.4.2 Batch criteria

7.2.4.2.1 During the inspection of appearance quality, refer to the sample quantities in Table 5; if the rejected quantity of pieces is less than the rejected quantities in Table 5, then the batch of product is acceptable for the item.

7.2.4.2.2 During the inspection of dimensional deviation, diagonal difference, thickness deviation, thick-thin difference, micro-waveness and warp, if the results comply with the requirements of corresponding clauses, then the batch is acceptable for the corresponding items.

7.2.4.2.3 During the inspection of light transmittance, if the test results are as specified in 5.6, then the batch is acceptable for the item.

7.2.4.2.4 If the above-mentioned 7.2.4.2.1, 7.2.4.2.2 and 7.2.4.2.3 are met, then the batch is acceptable; or else, it is rejectable.

7.3 Type inspection

7.3.1 General rules

Type inspection shall be carried out in one of the following cases.

a) during the commissioning of a new product or the finalization evaluation of a product;

b) when production is resumed after a cold repair of melting furnaces;

c) when there is any significant change in raw materials or technological parameters;

d) when there is any significant difference between the result of exit-factory inspection and that of last type inspection;

e) at least once each year during normal production.

7.3.2 Inspection items

The items of type inspection are as in 7.2.1.

7.3.3 Batch

As in 7.2.2.

7.3.4 Sampling

7.3.4.1 During the inspection of appearance quality, as in 7.2.3.1. […]