This method is mainly applicable to coated paper and paperboard, and can also be used for uncoated paper and paperboard or paper and paperboard samples with low printing gloss. The difference in sample color and diffuse reflectance has little effect on the measured gloss. For example, for black and white surfaces with the same gloss, the measured result of the white surface is less than one gloss unit higher than that of the black surface. GB 8941.3-1988 Paper and paperboard specular gloss determination method 75° angle determination method GB8941.3-1988 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Measurement of specular gloss of paper and board
75° angle measurement
Paper and board-
Measurement of specular gloss (75°)This standard specifies the method for measuring the specular gloss of paper and board using a 75° angle gloss meter. 1 Scope of application
GB 8941.3—88
This method is mainly applicable to coated paper and board, and can also be used for uncoated paper and board or paper and board samples with low printing gloss. The difference in sample color and diffuse reflectance has little effect on the measured gloss. For example, for black and white surfaces with the same gloss, the measured result of the white surface is less than one gloss unit higher than that of the black surface.
2 Definition
2.1 Gloss The property of directional selective reflection of the surface of an object. This property determines the degree of strong reflected light or the mirror image of the object that can be seen on the surface of the object.
2.2 Specular gloss The ratio of the luminous flux reflected from the sample surface into the specified aperture in the direction of specular reflection (regular reflection) to the luminous flux reflected by the standard mirror under the same conditions, expressed as a percentage. 3 Instrument
3.1 The main characteristics of the instrument are shown in the appendix. Its optical system consists of a light source, a lens, a sample pressing plate and a photoelectric device. The overall layout and relative dimensions of the main components are shown in the attached figure. The lens forms a converging light beam to irradiate the sample, the pressing plate keeps the sample flat, and the photoelectric device receives the reflected light from the sample. The optical device is installed in a box with a matte black paint on the inner wall. During preheating and normal operation, the structure and optical performance of the instrument are stable. 3.2 Gloss standard:
Theoretically, the standard for specular gloss is an ideal fully reflecting flat mirror, and its gloss value is set at 384.4 gloss units. According to this calculation, the gloss value of a smooth surface with a refractive index of 1.567 given by the Fresnel formula is 100 gloss units. 3.2.1 High gloss working standard The refractive index N of a smooth black glass plate (the refractive index of the mercury e-line spectrum) is measured, and the gloss value G of the working standard plate is calculated according to the following formula:
sin75°
Z arc sin
Y arc sin
rsin2(75° - Z) ± tg2(75° - Z)100[sn-(75.++
tg(75°+2)
sin2(75° -Y) + tg\(75°-Y)sin'(75°+Y)
tg(75°+ Y))
（1）
（2）
3.2.2 Medium gloss standard Objects with similar reflection characteristics to the paper sample to be tested, such as porcelain plates, can be used as medium gloss standard plates. The surface of the ceramic plate must be flat and the gloss must be uniform. Each ceramic plate must be calibrated with a black glass standard plate on an instrument that meets the requirements of (3, 1). Calibration of gloss value Approved by the Ministry of Light Industry of the People's Republic of China on April 12, 1988 and implemented on August 1, 1988
GB8941.388
Note: ① When not in use, the standard plate should be placed in a sealed box and kept clean to prevent contamination or damage to the surface. The working surface of the standard plate should not be placed downward to avoid dirt and wear. When holding the standard plate, hold it by the edge of the plate to prevent the oil and sweat on your hands from contaminating the working surface of the standard plate. The standard plate can be immersed in hot water and light detergent and gently scrubbed with a soft brush (do not use soapy water), and then rinsed with hot water at nearly 65°C. Rinse the detergent, and finally rinse with distilled water, and put it in an oven at about 70°C to dry. The black glass standard plate can be gently wiped clean with non-linting degreased mirror paper or other absorbent materials, but the medium gloss standard plate should not be wiped.
② As a high gloss standard black glass plate, the surface refractive index will gradually change after a few years, so it is recommended to be calibrated by the superior metrology department every year, and it is best to re-polish the surface to restore it to its original state. 3.3 Black cylinder lined with black velvet.
4 Preparation of samples
4.1 Samples are collected, processed and tested under standard conditions in accordance with the provisions of GB450 "Taking of Paper and Paperboard Samples". 4.2 Avoid watermarks, spots and visible paper defects from the extracted paper sheets, and evenly cut 5 test pieces of 100mm×100mm along the horizontal paper width. Keep them clean and do not touch the test surface with your hands. Note: The gloss of the sample will often be irreversibly reduced in a high humidity environment, so be careful not to make the sample damp. 5.1 According to the instrument manual, turn on the power supply. After preheating for the specified time, insert the black glass standard plate at the sample position and adjust the reading to the calibration value of the standard plate.
5.2 Replace the black cylinder and adjust the reading to zero.
5.3 Replace the black glass standard plate and recalibrate once, then replace the medium gloss standard plate to read the gloss value. The reading should be close to the calibration value of the standard plate. If the difference exceeds 1 gloss unit, check the geometry, spectrum and photometer characteristics of the instrument, or recheck the calibration values ​​of the two standard plates.
6 Test procedure
6.1 After calibrating the instrument with the standard plate and black cylinder, insert a sample each time to read the gloss value. Unless otherwise specified, each sample needs to be tested on both the front and back sides in both the vertical and horizontal directions. During the test, the standard plate and black cylinder can be used to recalibrate the instrument, and then check again after the test to ensure that the instrument is always calibrated correctly. 6.2 Take the average of the longitudinal and transverse values ​​as the gloss value for each side, and calculate the average and coefficient of variation of the gloss values ​​of the front and back sides of the five specimens respectively.
7 Accuracy
When the uniform specimen is measured by an instrument that strictly complies with the method of this standard, the reproducibility of the measurement result is within 2 gloss units. 8 Test report
Number of this standard;
Marking and description of the specimen;
Gloss values ​​of the front and back sides, accurate to 1 gloss unit; d.
Report the coefficient of variation of the measurement result as needed; Any test conditions that deviate from this standard.
GB8941.3-88
Appendix A
Provisions for the optical system of the 75° gloss meter
A1 The optical system is shown in the figure. The dot-dash line indicates the path of the paraxial light along the optical axis. The light starts from the light source and passes through the condenser and the center of the rectangular field light bar. The field fence is used to limit the effective size of the filament and should fill the filament image; the light continues to pass through the center of the illumination objective lens and the rectangular aperture light bar and reaches the sample; the intersection of the paraxial light and the sample plane is called the test surface center (not necessarily coincident with the geometric center of the test hole); when the plane mirror reflecting in front of the block is placed at the sample position, the paraxial light is reflected by the plane mirror and passes through the center of the receiving hole, and the illumination objective forms an image of the light source field fence on the receiving hole. The distance "d" from the center of the test surface to the receiving hole is used as the base for determining other dimensions, and d is not less than 10cm. The key dimensions are the angle of the incident light and the position and diameter of the receiving hole. A2 is close to the positive lens of the receiving hole, and the photoelectric device forms an image on the sample surface. In order to make the light entering the receiving hole through different paths be evenly received, a piece of frosted glass can be installed in front of the photoelectric device so that the sample is imaged on the frosted glass, and the photoelectric device receives the scattered light of the frosted glass. There is an extinction gear on the inner wall of the mirror tube connecting the lens and the photoelectric device. In addition to the light reflected by the sample, the stray light entering the receiving hole is absorbed and eliminated by the inner wall.
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Figure A1 Schematic diagram of 75° angle gloss
A3 Angle of incidence: The angle of incidence of the beam axis on the sample is 75±0.1°. A4 Receiving hole: The diameter of the receiving hole is 0.2000d±0.0005d, and the edge thickness is less than 0.005d. When the sample is a plane mirror reflecting from the front, the paraxial light should pass vertically through the center of the receiving hole after being reflected by the mirror, with an allowable error of 0.0004d. 453
GB8941.3—88
A5 Position and size of the light source field bar: The light source field bar is imaged on the plane of the receiving hole, and the position error (along the optical axis direction) is allowed to be within 0.04d. The size of the rectangular image is 0.1d±0.01d×0.05d±0.005d, with the short side parallel to the incident plane. A6 Uniformity of light in the field bar: The luminous flux in the field bar should be evenly distributed, see TAPP1T480 for details. A7 Position and size of the aperture light bar: The rectangular aperture bar is perpendicular to the beam axis, 0.6d ± 0.05d away from the center of the test surface. The size of the light bar is 0.1d ± 0.01d × 0.05d ± 0.005d, and the short side is parallel to the incident plane. The incident light beam is not restricted by other light bars. A8 Uniformity of light in the aperture light bar: The requirements are the same as the light source field bar. A9 Spectral conditions: Incandescent lamp with a color temperature of 2850 ± 100K, use a filter to correct the spectral characteristics of the photoelectric device. The spectral response of the combination of the two should conform to the CIE spectral light efficiency function.
A10 Photoelectric device: The photoelectric device and display circuit convert the received luminous flux into a digital display. The conversion accuracy should be within ±0.0 ...2%, i.e. within 0.2 gloss units. A11 sample pressing plate: The sample pressing plate presses the paper sample tightly against the test hole. When necessary, the suction switch can be turned on to form negative pressure between the pressing plate and the cardboard, and the paper sample is adsorbed on the pressing plate to keep it flat. When the paper sample is a piece of soft plastic film with uniform thickness (such as an optical grade polyester film with a thickness of 0.08 mm), turn on the suction switch, and the image of the filament can be seen on the receiving hole; compare it with the filament image produced by the black glass standard plate mentioned above. There should be no difference in position and size between the two. Additional notes:
This standard is under the jurisdiction of the Paper Industry Science Research Institute of the Ministry of Light Industry. This standard was drafted by the Tianjin Paper Research Institute. This standard refers to the American Pulp and Paper Association standard Tapp1T480om--85.454
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