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SEMI D35-1103 E © SEMI 2003 6 each point to be measured. Fix the lamp and move the spectrora diometer or the colorimeter for better measurement since the lamp wall temperature does not vary an d so the luminance becomes …

SEMI D35-1103

Me asure me nt St arte d

±3%

Overcurrent

Luminanc e

100%

Figure 4

Measuring Time of Optical Characteristics

Commentary on Figure 4: The CCFL luminance has a special rising property. The highest luminance and stable

luminance vary by the combination of ambient temperature and lamp current and the transitions vary as well. This is

based upon the fact that the CCFL luminance depends on temperature and the generated heat by lighting affects it.

For this reason, the luminance varies until the lamp wall temperature becomes stable. Before the measurement, grasp

the special rising property of luminance and set the timing of measurement of the stable luminance.

9.2.4 Measurement of Luminance — Set a spectroradiometer or a colorimeter vertical to a side to be measured and

measure according to the above-mentioned instruction of measurement. Avoid shades of mercury particles in the

lamp. (See Figure 5.)

Station Diame

Lamp insi

diamete

Lamp outsi

diamete

M ercury Grain

(Within 50%

inner diame

Station Diameter

(Within 50% of

inner diameter)

Lamp inner

diameter

Lamp outer

diameter

Figure 5

Measuring Spot (Diameter) for Optical Characteristics

9.2.5 Measurement of Chromaticity — Measure in the same manner and at the same time of the measurement of

luminance.

9.3 Measurement of Effective Length of Luminous Part — Measure when the luminance is fully stable at a specified

lamp current according to the measuring conditions mentioned above. The luminance varies greatly around

electrodes since the temperature variation is big among points of measurement due to high temperature of a lamp

wall. Sufficient aging shall be performed before measurement to avoid impacts of the change of passage of time to

SEMI D35-1103

each point to be measured. Fix the lamp and move the spectroradiometer or the colorimeter for better measurement

since the lamp wall temperature does not vary and so the luminance becomes stable in this way. (See Figure 6.)

100%

Luminance

Effective length of luminous part

70%

Figure 6

Measurement of Effective Length of Luminous Part

9.4 Measurement of Luminance Stabilization Time —

Use a CCFL in which the wall temperature and ambient

temperature are kept in equilibrium before lighting.

From just after a CCFL is turned on by specified lamp

current, measure the luminance changes until it seems

stable (where the luminance fluctuation difference is

within ± 3% of the stable luminance, for example).

10 Reporting Results

10.1 Report the following items:

10.1.1 report date,

10.1.2 test date,

10.1.3 measuring equipment types, and conditions of

use (lighting frequency, rated length of connecting

wire, distance of measurement, viewing angle, etc.),

10.1.4 conditions of test specimen (size, other

specifications, etc.),

10.1.5 to specify item names and necessary entries for

the CCFL outer and inner diameters, lamp length and

necessary specifications,

10.1.6 conditions of measurement (ambient

temperature, aging time, etc.),

10.1.7 measurement results (electrical and optical

characteristics), and

10.1.8 remarks (other notes).

11 Related Documents

Related Information 1: documents regarding main

discharge,

Related Information 2: dark characteristics, and

Related Information 3: precautions for measuring

method (leakage current, lamp wall temperature,

temperature slide-up speed for master CCFL, etc.).

NOTICE: SEMI makes no warranties or

representations as to the suitability of the standards set

forth herein for any particular application. The

determination of the suitability of the standard is solely

the responsibility of the user. Users are cautioned to

refer to manufacturer's instructions, product labels,

product data sheets, and other relevant literature,

respecting any materials or equipment mentioned

herein. These standards are subject to change without

notice.

By publication of this standard, Semiconductor

Equipment and Materials International (SEMI) takes no

position respecting the validity of any patent rights or

copyrights asserted in connection with any items

mentioned in this standard. Users of this standard are

expressly advised that determination of any such patent

rights or copyrights, and the risk of infringement of

such rights are entirely their own responsibility.

SEMI D35-1103

RELATED INFORMATION 1

STARTING VOLTAGE OF COLD CATHODE FLUORESCENT LAMP

(CCFL)

NOTICE: This related information is not an official part of SEMI D35 and was derived from Japan Backlight TF.

R1-1 Phenomenon of CCFL Discharge

Starting

R1-1.1 Although the phenomenon of CCFL discharge

starting shows the similarity to that of low gas pressure

discharge starting, a high frequency lighting circuit

(inverter) with approximately 30–100 kHz is mostly

used to discharge and so it is affected by stray

capacitance.

R1-1.2 When the secondary voltage of inverter is

stepping up from a sufficiently low voltage gradually,

an emission area appears near the electrode connected

to higher voltage side. (See Figure R1-1 1

Phase).

This means that the discharge starts between the

electrode and ground level of discharge circuit through

the stray capacitance, and a spark after dark current

takes place in the discharge space in the tube. In the

discharge, the other electrode is the tube wall (glass or

fluorescent substance); the formation of dielectric

barrier discharge and the existence of the secondary

electron supply system to the discharge space can be

considered and thus the discharge seems sustainable.

Therefore, the emission around the electrode is judged

to be the emission mainly by negative glow of glow

discharge.

R1-2 From Discharge Starting to Stable

Lighting Mode

R1-2.1 After the discharge takes place near the

electrode and the secondary voltage of the inverter

increases gradually, the emission area near the

electrode grows longer accordingly. (See Figure R1-

2.) This means that a positive column is generated by

applied voltage to have such the length as corresponds

to the value of resistance based on the applied voltage.

When the voltage is applied furthermore, the emission

area (i.e. positive column) between two electrodes is

generated finally. (See Figure R1-3 2

Phase.)

However, if the tube is thin and long and the stray

capacitance is relatively greater to the discharge circuit,

the ratio of current that flows through the stray

capacitance is still large at this phase. With the

increase of the inverter secondary voltage, the ratio of

current that flows in the tube also increases and most of

the current flows in the tube because the impedance of

discharge path decreases on the contrary due to

negative characteristics of discharge. (See Figure R1-4

Phase.)

R1-2.2 Each voltage applied at these three phases may

be called starting voltage at the first phase, or stable

discharge voltage or tube current at the third phase, for

example. Sometimes it could be hard to distinguish the

second phase from the third phase. In addition, since

the second phase is hardly observed by the tube designs

(for the tube length, outer and inner diameters of tube,

pressure and composition of filler gas, and peripheral

members of tube), it looks as if the first phase shifted to

the third phase suddenly. This is because the stray

capacitance is so big that the current cannot flow into

the tube, the discharge surges immediately after the

current flows into the tube, the impedance of the

discharge path decreases due to the negative

characteristics and a large amount of current flows in

the tube all of a sudden.

R1-2.3 From the viewpoint of discharge phenomenon,

the voltages applied to the tube at the first and third

phases are important. Especially the voltage applied at

the third phase should be noted practically. (The

voltage applied at the second phase may be noted also.)

R1-3 Cautions at Discharge Starting

R1-3.1 At the discharge starting,  coefficient of

discharge gas and  coefficient of electrode are

involved. These coefficients contain the pressure of

discharge gas (particle density) as a parameter.

Especially when the mercury is filled in, the control of

ambient temperature becomes very important because

the mercury vapor (particle density) pressure changes

sensitively to the ambient temperature.

R1-3.2 In addition, the lighting circuit is usually built

for AC, the reduction of unnecessary stray capacitance

base on frequency shall be required. As the impact of

stray capacitance becomes greater especially when the

tube is thin and long, sufficient consideration shall be

given.