Color Filter Glass Glossary

Color Specification

CIE Equivalents have been obtained in conformance with the Japanese industrial. Standard JIS Z 8701, "Specification of Colors According to the CIE 1931 Standard Colorimetric System and the CIE 1964 Supplementary Standard Colorimetric System", and JIS Z 8722, "Methods of Measurement for Color of Reflecting or Transmitting Objects". On this home page, the values x and y for standard illuminants A have been used. Please ask our sales department for other values such as Y for illuminants A, Y, x and y for illuminants C and D65.

Thickness

The transmittance of color filter glass may slightly vary by melt, in which case the variance may be compensated for with thickness. Thicknesses stated on this home page are those usually used, but the thickness of standard products may differ from these.

Refractive Index (nd)

The refractive indices listed is given for standard spectral lines of d line (587.6nm).

Chemical Properties

Dimming and Staining sometimes may be observed on the glass surface in the polishing or coating process or during storage. The resistibility of glasses to these surface phenomena is expressed in terms of Water Durability, for dimming, and Acid Durability, for staining.

Dimming

Polished glass exposed to high humidity or temperature variation may "sweat". Water vapour may condense to form droplets on the glass surface. Some of the glass components that dissolve in the droplets may in turn attack the glass surface and react with gaseous elements in the air (CO2 for example). Reaction products form as white spots or a cloudy film as the glass surface dries. This phenomenon is called "dimming".

Staining

In varying degrees, water contact causes a chemical reaction {ion exchange between cations in the glass and hydronium ions (H3O+) in water} which result in a silica-rich surface layer that causes an interference color at the layer. This phenomenon is called "staining".

Water Durability (Dw)

Glass is powdered and sieved to select particle sizes of 420~590µm. The powdered glass, weighed by its specific gravity, is placed in a platinum net basket and soaked in 80 ml pure water (pH 6.5~7.5), which is contained in a fused silica flask. The glass is then boiled for 60 minutes and classified according to the percentage of weight loss.
Class Weight Loss (wt%)
1 ≤0.04
2 0.05~0.09
3 0.10~0.24
4 0.25~0.59
5 0.60~1.09
6 ≥1.10

Acid Durability (DA)

Glass is powdered and sieved to select particle sizes of 420 ~590µm. The powdered glass, weighed by its specific gravity, is placed in a platinum net basket and soaked in 80 ml 0.01 N nitric acid solution, which is contained in a fused silica flask. The glass is then boiled for 60 minutes and classified according to the percentage of weight loss.
Class Weight Loss (wt%)
1 ≤0.19
2 0.20~0.34
3 0.35~0.64
4 0.65~1.19
5 1.20~2.19
6 ≥2.20

Thermal Properties

The thermal properties of color filter glass are important for annealing and thermal processing. Three thermal properties are given, namely, transformation temperature (Tg), sag temperature (Ts), and mean coefficient of liner thermal expansion (α). They are determined from a thermal expansion curve obtains from a well annealed specimen heated at a rate of 4°C/min (or at 2°C/min when the temperature is between -30°C and +70°C). A differential thermal dilatometer is used for the measurement as it maintains a uniform temperature distribution within ±1°C.

Transformation Temperature (Tg)

As illustrated in fig.1, the transformation temperature is determined by the intersection point of the two tangents of the high and low temperature ranges of the thermal expansion curve.

Sag Temperature (Ts)

As illustrated in fig.1, the sag temperature is defined as the temperature at which the thermal expansion curve starts to yield.

fig. 1

Mean Coefficient of Linear Thermal Expansion (α)

The mean coefficients of linear thermal expansion are measured over both the temperature ranges of -30°C~+70°C and +100°C~+300°C, and are expressed in 10-7deg-1 units.

Mechanical Properties

The Knoop Hardness and Abrasion Factors are listed as a guide for lapping and polishing operations of color filter glass.

Knoop Hardness (Hk)

Knoop hardness is determined by loading a pyramid-shaped diamond indenter with vertex angles of 172°30' and 130° on a polished glass surface at 0.1 kgf for 15 seconds. It is calculated using the following formula.

Abrasion Factor (FA)

Abrasion factor is a relative measure for lapping. A glass sample with a surface area of 9cm2 is placed 80 mm from the center of a cast iron circular plate. The plate is then rotated horizontally at 60 r.p.m., and a 1kgf lapping weight is vertically loaded on the sample. Lapping is continued for 5 minutes, with a continuous supply of a lapping compound composed of 10 g aluminum oxide (gain size 20µm) in 20 ml of water. The weight loss of the sample is then measured and compared to the standard reference material (BSC7) specified by the Japanese Optical Glass Industrial Standard. The abrasion factor is determined with the following formula.

Specific Gravity (S)

Specific gravity of glass is defined relative to the density of pure water at 4°.

 

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