ANSI T 527 OM-2013 Color of paper and paperboard (d 0 C 2).pdf

1、 TAPPI/ANSI T 527 om-13 SUGGESTED METHOD 1972 CLASSICAL METHOD 1992 OFFICIAL METHOD 1994 REVISED 2002 CORRECTED 2002 REVISED 2007 REVISED 2013 2013 TAPPI The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association a

2、ssume no liability or responsibility in connection with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published. Approved by the Stan

3、dard Specific Interest Group for this Test Method TAPPI CAUTION: This Test Method may include safety precautions which are believed to be appropriate at the time of publication of the method. The intent of these is to alert the user of the method to safety issues related to such use. The user is res

4、ponsible for determining that the safety precautions are complete and are appropriate to their use of the method, and for ensuring that suitable safety practices have not changed since publication of the method. This method may require the use, disposal, or both, of chemicals which may present serio

5、us health hazards to humans. Procedures for the handling of such substances are set forth on Material Safety Data Sheets which must be developed by all manufacturers and importers of potentially hazardous chemicals and maintained by all distributors of potentially hazardous chemicals. Prior to the u

6、se of this method, the user must determine whether any of the chemicals to be used or disposed of are potentially hazardous and, if so, must follow strictly the procedures specified by both the manufacturer, as well as local, state, and federal authorities for safe use and disposal of these chemical

7、s. Color of paper and paperboard (d/0, C/2) 1. Scope1.1 This method specifies a procedure for measuring the color of paper or paperboard with tristimulus filter colorimeters or spectrophotometers incorporating diffuse/0 geometry and CIE (International Commission on Illumination) illuminant C. NOTE 1

8、: TAPPI T 524 “Color of Paper and Paperboard (45/0, C/2)” describes a similar procedure using directional illumination and normal viewing. 1.2 In the method, tristimulus values X (red), Y (green), and Z (blue), appropriate to the CIE-1931 (2) standard observer, are calculated from reflectance measur

9、ements Rx, Ry, and Rzor from R () data. Color can then be expressed in various color space systems: 1. Hunter L, a, b 2. CIE L*, a*, b* 3. L*, C*, h 4. Dominant wavelength, purity, luminosity 5. Color difference, E, E*, E*94, E (CMC) 1.3 Instruments equipped with microprocessors which give direct in

10、formation relating to different color scale systems conform to this method only if the means of measurements and calculation conform to the descriptions herein. 2. Significance 2.1 The color appearance of paper and paperboard is important for its aesthetic value in marketing packaged products, as an

11、 aid to distribution of multi-ply forms; to differentiate pages or sections of published literature, in artwork, and in many other applications. T 527 om-13 Color of paper and paperboard (d/0, C/2) / 2 2.2 A numerical definition of color is essential to good quality control and to customer-producer

12、relationships. 3. Definitions 3.1 Dominant wavelength (of an illuminated object), the wavelength of spectrally pure energy which when mixed with the illuminant in suitable proportions will match the color of the specimen. 3.2 Purity, excitation, the ratio of the distance on a CIE chromaticity diagra

13、m between the achromatic point and the specimen point to the distance along a straight line from the achromatic point through the specimen point to the illuminant spectrum locus. The term “saturation” is also applied to this quantity. 3.3 Luminosity, the scale of perception representing a colors sim

14、ilarity to achromatic colors between black and white. This quantity is also known as “luminance” and “luminous reflectance.” 3.4 L, a, b, L*, a*, b*, these symbols are used to designate color values as follows: L, L* represents lightness increasing from zero for black to 100 for perfect white; a, a*

15、 represents redness when positive, greeness when negative; and b, b* represents yellowness when positive, blueness when negative. When a* and b* are simultaneously zero, they represent grey. 3.5 L*, C*, h, L* is as described in 3.4, C* represents chroma, and h represents hue angle. 3.6 E, E*, E (CMC

16、), the overall color difference values take into account lightness/darkness differences as well as chromatic differences. The intent is for a given value of E, E*, E (CMC), to represent the same visual perception of color difference anywhere in color space. 4. Apparatus 4.1 Instrumental components1,

17、 consisting of a means for fixing the location of the surface of the specimen, a system for proper illumination of the specimen, suitable filters, gratings, or other optical components for altering the spectral character of the rays reflected from the specimen, photosensitive receptors to receive th

18、e reflected rays, and a means for transforming the receptor outputs to tristimulus functions. 4.2 Spectral characteristics 4.2.1 Incident light. The spectral power distribution of the light incident on the specimen determines the extent to which reflected light may be augmented by fluorescence. The

19、product of the spectral power distribution of the source and spectral transmittance of the glass lenses and infrared absorbing filter in the incident system should correspond to the energy distribution as defined for a source matching illuminant C given as a function of wavelength in Table 1. This r

20、elative spectral power distribution may be approximated by a select combination of a tungsten filament source, a heat absorbing filter, and UV trimming filter in the incident beam. If the paper or paperboard being measured by a spectrophotometer contains no fluorophores (fluorescent components, i.e.

21、, optical brightness), the spectral distribution of incident light will not affect the measurement of color, provided that sufficient energy is available at each wavelength of measurement. 4.2.2 Light energy. The light energy incident on the test specimen should not appreciably heat or fade the spec

22、imen during the measurement. An infrared absorbing filter (heat filter) in the incident beam will normally prevent overheating the specimen. 4.2.3 Spectral response. The overall spectral response of the instrument, as determined by the combination of the spectral distribution of incident light on th

23、e specimen, the absorption characteristics of the filters and other light altering optics, and the photosensitive response of the receptors to light reflected from the specimen, shall simulate the CIE color-matching functions weighted by the relative spectral energy distribution of CIE Illuminant C/

24、2 given in Table 2. All color spectrophotometers conforming to this method, T 527, must use the integration tables contained in ASTM E308 (Table 5.6), “Standard Practice for Computing the Color of Object by Using the CIE System,” for the computation of tristimulus values X, Y, and Z. 4.3 Geometric c

25、haracteristics. The specimen shall be illuminated diffusely by means of an integrating sphere meeting the requirements of ISO 2469. The direction of viewing shall be perpendicular 0.5 degrees to the specimen surface. Only reflected rays within a solid cone, whose vertex is in the specimen aperture,

26、and of half-angle not greater than 4, shall fall on the receptor. To prevent specularly reflected light from reaching the receptor, the 1Names of suppliers of testing equipment and materials for this method may be found on the Test Equipment Suppliers list, available as part of the CD or printed set

27、 of Standards, or on the TAPPI website general Standards page. 3 / Color of paper and paperboard (d/0, C/2) T 527 om-13 receptor aperture shall be surrounded by a black annulus (gloss trap) with external diameter subtending a half-angle of 15.5 0.5 at the center of the specimen aperture. NOTE 2: Int

28、erchange of incident and viewing directions is allowed under this method. Table 1. Relative spectral energy distribution incident on the specimen Wavelength, nm Relative energy, E Illuminant C 320 0.01 330 0.40 340 2.70 350 7.00 360 12.90 370 21.40 380 33.00 390 47.40 400 63.30 410 80.60 420 98.10 4

29、30 112.40 440 121.50 450 124.00 460 123.10 470 123.80 480 123.90 490 120.70 500 112.10 510 102.30 520 96.90 530 98.00 540 102.10 550 105.20 560 105.30 570 102.30 580 97.80 590 93.20 600 89.70 610 88.40 620 88.10 630 88.00 640 87.80 650 88.20 660 87.90 670 86.30 680 84.00 690 80.20 700 76.30 T 527 om

30、-13 Color of paper and paperboard (d/0, C/2) / 4 Table 2. Tristimulus functions for CIE Illuminant C/2 Wavelength, nm Ecx Ecy Ecz 360 -0.001 -0.000 -0.006 380 -0.011 -0.000 -0.054 400 0.089 -0.001 0.393 420 2.919 0.085 14.033 440 7.649 0.511 38.518 460 6.641 1.382 38.120 480 2.364 3.206 19.564 500 0

31、.069 6.910 5.752 520 1.198 12.876 1.442 540 5.591 18.258 0.357 560 11.750 19.588 0.073 580 16.794 15.991 0.026 600 17.896 10.696 0.013 620 14.018 6.261 0.003 640 7.457 2.902 0.000 660 2.746 1.008 0.000 680 0.712 0.257 0.000 700 0.153 0.055 0.000 720 0.034 0.012 0.000 740 0.007 0.003 0.000 760 0.002

32、0.001 0.000 780 0.000 0.000 0.000 SUM 98.073 100.000 118.232 4.4 Photometric characteristics. The photometric system must be linear over the entire scale to within 0.2% of full scale. Photometric linearity may be determined by following the procedure described in TAPPI T 1217 “Photometric Linearity

33、of Optical Properties Instruments.” The instrument must be sufficiently stable that the reflectance factor reading will not fluctuate by more than 0.1% of full-scale deflection while the measurement is being made. 5. Standards 5.1 Primary reflectance standard1. The primary reflectance standard (100%

34、) is an ideal uniform diffuser with a perfectly reflecting and diffusing surface (the perfect reflecting diffuser). 5.2 Calibration standards1. Reflectance values assigned to calibration standards shall be traceable to an instrument calibrated in terms of the primary reflectance standard and having

35、geometric and spectral characteristics consistent with this method. 5.3 Specific calibration standards1. Specific calibration standards, colored similar to the paper to be tested, may be used to minimize the effect of spectral and geometric differences between instruments whose results are being com

36、pared. The “specific calibration” values for these standards should be established by first exchanging paper samples of the type of paper to be compared. The paper sample and the ceramic standard must not form a metameric pair. 5.4 Black standard a black cavity with a reflectance factor which does n

37、ot differ from its nominal value by more than 0.2 reflectance units at all wavelengths. 5 / Color of paper and paperboard (d/0, C/2) T 527 om-13 6. Calibration 6.1 Carefully check the calibration of photometric scales at reasonable time intervals in a manner to insure linearity and accuracy over all

38、 ranges. Calibration may be accomplished by placing a series of neutral filters of known transmittance in the incident beam, or by measuring the reflectance factor of calibrated opaque specimens. NOTE 3: Reference (1) describes procedures for use of a set of special test panels in calibration of maj

39、or photometric, spectral, and geometric characteristics of the instrument. 6.2 Photometric linearity and proper spectral response of the instrument are key factors for determining accurate color measurements. Carefully measure colored standards and their results compared to assure color measurement

40、accuracy of the apparatus. NOTE 4: If necessary, clean ceramic or glass verification standards, using the procedures provided by the supplier of the standards. 6.3 Place the black standard against the specimen aperture and adjust the zero setting of the instrument. 6.4 Replace the black standard wit

41、h a white calibration standard and set the instrument to the calibrated reflectance value of the standard at each filter position or wavelength, as appropriate. 7. Test specimen From each test unit of the paper obtained in accordance with TAPPI T 400 “Sampling and Accepting a Single Lot of Paper, Pa

42、perboard, Containerboard, or Related Product,” cut the sample to be tested into pieces large enough to extend at least 0.25 in. (6.35 mm) beyond all edges of the instrument aperture. Assemble the pieces into a pad which is thick enough so that doubling the pad thickness does not change the test read

43、ings. (With creped or other bulky papers take care to avoid pillowing of the pad into the instrument by too much pressure.) Do not touch the test areas of the specimens with the fingers, and protect them from contamination, excessive heat, or intense light. 8. Procedure 8.1 Operate the instrument in

44、 accordance with the manufacturers instructions. Allow adequate warm-up to insure stable results. 8.2 Calibrate the instrument as described in Section 6. 8.3 Place the opaque pad of sample sheets with the side to be measured against the sample aperture and obtain the reflectance values Rx, Ry, and R

45、zand/or the reflectance spectra. 8.4 Move the uppermost test piece to the bottom of the pad and obtain the reflectances of the newly exposed specimen. Repeat this process until five specimens have been tested. 8.5 Recheck the instrument calibration and retest the sample if any of the calibration ref

46、lectances show a drift greater than 0.1% of full scale. 9. Calculations NOTE 5: The use of the three-filter system may result in small to significant differences from the values obtained using the full function for the tristimulus value X depending upon the spectral characteristics of the sample (4)

47、. 9.1 Calculate the tristimulus values X, Y, and Z for each specimen from: X = 0.78341 Rx+ 0.19732 Rz Y = Ry Z = 1.18232 Rz or by using the integration tables in ASTM E308, “Standard Practice for Computing the Color of Object by Using the CIE System,” for a spectrophotometer. 9.2 Calculate color in

48、one of the following color space systems: (most instruments are equipped with microprocessors which do the necessary computational work). T 527 om-13 Color of paper and paperboard (d/0, C/2) / 6 9.2.1 Hunter L, a, b. Calculate Hunter color values from: L = 100 (Y/Y0)1/2 a = Ka(X/X0-Y/Y0)/(Y/Y0)1/2 b

49、 = Kb(Y/Y0-Z/Z0)/(Y/Y0)1/2 Constants for the above equations for illuminant C/2 are X0= 98.073, Y0= 100, Z0= 118.232, Ka= 175.0, and Kb= 70.0. If desired, calculate color difference from: E = (L2+ a2+ b2)1/2 9.2.2 CIE L*, a*, b* (CIELAB). Calculate CIELAB color values from: (preferred) L* = 116 (Y/Y0)1/3 - 16 a* = 500 (X/X0)1/3- (Y/Y0)1/3 b* = 200 (Y/Y0)1/3- (Z/Z0)1/3 where: X/X0, Y/Y0and Z/Z0 0.01. The constants X0, Y0, and Z0are given in paragraph 9.2.1. If desired, calculate color difference from: E* = (L*2+ a*2+ b*2)1/2 9.2.3 L*