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4713A
Background Statement for SEMI Draft Document 4713A
New Standard: Measurement Method for Depolarization Effect of FPD Color Filter
Note: This background statement is not part of the balloted item. It is provided solely to assist the recipient in reaching an informed decision based on the rationale of the activity that preceded the creation of this document.
Note: Recipients of this document are invited to submit, with their comments, notification of any relevant patented technology or copyrighted items of which they are aware and to provide supporting documentation. In this context, “patented technology” is defined as technology for which a patent has issued or has been applied for. In the latter case, only publicly available information on the contents of the patent application is to be provided.
Background Statement
Depolarization effect of color filter (CF) greatly influences display quality of liquid crystal display. So, many companies have tried to decrease depolarization effect of CF. However, it is difficult to compare the data of depolarization effect that many companies are presented because there is no standard measurement method for depolarization effect of CF. Therefore, this document standardizes the measurement method for depolarization effect of CF.
If you have any questions, please contact to the Color Filter Depolarization Effect Task Force leader,
Tetsuo Yamashita (Toray Industries), or Hirofumi Kanno (SEMI Japan),
The results of this letter ballot will be discussed at the next Japan FPD Materials & Components Committee Meeting on 14th of April, 15:00-17:00 at SEMI Japan Tokyo Office.
SEMI Draft Document 4713A
New Standard: Measurement Method for Depolarization Effect of FPD Color Filter
1 Purpose
1.1 This standard establishes implementation practices for measuring the depolarization effect of FPD color filters.
1.2 These methods can be applied to manufacturing, quality control, and development work.
2 Scope
2.1 This standard specifies measuring methods.
2.2 In this standard, the depolarization effect of color filters is obtained by measuring the reduction in polarization efficiency when polarized light passes through color filters.
NOTICE: This standard does not purport to address safety issues, if any, associated with its use. It is the responsibility of the users of this standard to establish appropriate safety and health practices and determine the applicability of regulatory or other limitations prior to use.
3 Referenced Standards and Documents
None.
4 Definitions of Measurement Objects and Measuring Methods
4.1 Contrast Ratio
4.1.1 Definition of Contrast Ratio ― The contrast ratio is defined as the ratio between the maximum and minimum luminance when two polarizing films are set parallel and perpendicularly to one another while a sample to be tested is placed between them. An absolute value is measured unique to the measurement system consisting of a light source, polarizing film, and luminance meter. Absolute contrast ratio values cannot be compared with different measurement systems.
4.1.2 Measurement Method for Contrast Ratio
4.1.2.1 Reference Measurement
4.1.2.1.1 Place the light source, two polarizing films, and luminance meter as shown in Figure 1.
4.1.2.1.2 Set two polarizing films parallel and perpendicularly, and obtain the maximum luminance (LRmax) and the minimum luminance (LRmin).
Figure 1
Configuration of Contrast Ratio Measurement (Reference Measurement)
4.1.2.1.3 Calculate LRmax/LRmin to obtain the reference contrast ratio (CRref).
4.1.2.2 Sample Measurement
4.1.2.2.1 Place the sample between two polarizing films (Figure 2).
4.1.2.2.2 Set two polarizing films parallel and perpendicularly, and obtain the maximum luminance (LSmax) and the minimum luminance (LSmin).
4.1.2.2.3 Calculate LSmax/LSmin to obtain the sample contrast ratio (CRsam).
Figure 2
Configuration of Contrast Ratio Measurement (Sample Measurement)
4.1.2.3 Recording the Measurement Results
4.1.2.3.1 Record the following items together with the measurement results (LRmax, LRmin, CRref, LSmax, LSmin, and CRsam).
· Sample creation conditions, film thickness, glass substrate type, and product name
· Measurement environment (brightness, temperature, and humidity of the measurement environment)
· Light source (type, product name, luminance, and wavelength distribution)
· Polarizing film (type, product name, and transmitted light wavelength distribution of parallel Nicol and crossed Nicol)
· Type of polarizing film rotation (manual, automatic, and resolution)
· Luminance meter (type and product name) and luminance performance and measurement conditions (view angle, parameter used, etc.)
· Distance of the measurement materials placed
4.2 Depolarization Level
4.2.1 Definition of Depolarization Level ― The depolarization level is defined by an increase in the minimum luminance (reduction in depolarization level) when the sample is inserted between two polarizing films from when it is placed outside the two films.
4.2.2 Measurement Method of Depolarization Level
4.2.2.1 Reference Measurement
4.2.2.1.1 Place the light source, two polarizing films, luminance meter, and the sample as shown in Figure 3 (the sample can be placed either above or below the polarizing films).
4.2.2.1.2 Set two polarizing films perpendicularly to obtain the minimum luminance, Lref.
Figure 3
Configuration of Depolarizing Level Measurement (Reference Measurement)
4.2.2.2 Sample Measurement
4.2.2.2.1 Place the sample between two polarizing films (Figure 4).
4.2.2.2.2 Set two polarizing films perpendicularly to obtain the minimum luminance, Lsam.
4.2.2.2.3 Calculate (Lsam-Lref)/Lref X 100 (%) for the depolarization level.
Figure 4
Configuration of Depolarizing Level Measurement (Sample Measurement)
4.2.2.3 Recording the Measurement Results
4.2.2.3.1 Record the following items together with the measurement results (Lref, Lsam, and depolarization level).
· Sample creation conditions, film thickness, glass substrate type, and product name
· Measurement environment (brightness, temperature, and humidity of the measurement environment)
· Light source (type, product name, luminance, and wavelength spectrum)
· Polarizing films (type, product name, and transmitted light wavelength distribution of parallel Nicol and crossed Nicol)
· Type of polarizing film rotation (manual, automatic, and resolution)
· Luminance meter (type and product name) and luminance performance and measurement conditions (view angle, parameter used, etc.)
· Distance of the measurement materials placed
5 Notice for Measurement
5.1 Measurement Environment
5.1.1 Measurement varies depending on the ambient environment (brightness, temperature, and humidity), dust, scratches and dirt of the polarizing films and a sample, and deterioration of the light source. Therefore, measurement shall be run in a dark room. Furthermore, measurement shall be run in an environment of controlled temperature and humidity and with very little dust. Confirm that the polarizing films and samples have no scratches or dirt, and that there is no deterioration of the light source before measurement.
5.2 Measurement Material and Equipment
5.2.1 Light Source
5.2.1.1 Use a light source that can illuminate the measurement area uniformly (no luminance variation throughout the measurement area). A conventional light source including LED, CCFL (Cold Cathode Fluorescent Lamp), halogen lamp etc, can be used; however, when a spectrophotometer is used for luminance metering, a continuous light source shall be used.
5.2.2 Polarizing Film
5.2.2.1 Use polarizing films with a polarizing ratio of over 10000:1 and small wavelength dispersion of transmittance in parallel Nicol and crossed Nicol. Comfirm that there is no deterioration with time, scratches and dust.
5.2.3 Luminance Meter
5.2.3.1 Lower measurement limit of luminance meter shall be less than 1/10 of the measured minimum luminance. When the measurement limit is not small enough, luminance of the light source shall be increased. In addition, ensure that the maximum luminance does not exceed the upper measurement limit of luminance meter. For greater accuracy, a luminance meter of the spectrophotometer type is more preferable as it can measure luminance of the individual wavelength. The distance between luminance meter and color filter shall be within 1.5m and the measuring area shall be from 1mm to 30mm in diameter.
5.3 Measurement Method
5.3.1 How to Obtain the Maximum Luminance and the Minimum Luminance
5.3.1.1 The maximum luminance and the minimum luminance are obtained by setting two polarizing films parallel and perpendicularly; however, the following shall be adopted for high reproducibility.
· Automatic setting for polarizing films with resolution less than 0.05° instead of manual setting.
· For minimum luminance several measurements (desirably five points or more) around crossed Nicol or, alternatively, the estimation of the minimum luminance from an approximation curve of the measured points.
· For maximum luminance several measurements (desirably five points or more) around parallel Nicol or, alternatively, the estimation of the maximum luminance from an approximation curve of the measured points.
5.3.2 Improving the Reproducibility of the Contrast Ratio
5.3.2.1 For reproducibility a measurement shall be run by adjusting the luminance of the light source to make the maximum reference luminance constant and adjusting the polarizing film angle to make the minimum luminance constant, against the change of contrast ratio due to deterioration with time of the light source and the polarizing films.
6 Calibration of Equipment
6.1 Equipment shall be calibrated based on the manufacturers’ operation manuals.
6.2 When the measurement characteristics change by calibration, they shall be recorded.
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.
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