UV radiation curing measurement and calibration

  UV machine, UV radiation curing technology after nearly 30 years of development, are widely used in coatings, inks, adhesives and electronics, and many other fields. Uv radiation curing were introduced in this paper in the field of commonly used terms, radiation measurement, unit and definition, ultraviolet radiation national standard system. Article stressed the importance of measurement in the field of ultraviolet radiation curing, uv radiation intensity of illumination/energy meter reach the surface of the coating is the quantitative measurement of radiation intensity of illumination/energy instrument, regular calibration of measuring instruments is the only way to ensure accurate and reliable value.

  Radiation curing the basic meaning is the use of ultraviolet (UV) or for the energy of the electron beam, have caused chemical activity of liquid formula in the solidification process of substrate surface to achieve rapid response. Radiation curing is a rapid development of high and new technology industry, curing speed, high coating quality, less environmental pollution, low energy consumption etc [1]. Since the 70 s, the application of radiation curing technology is more and more popular, with an average annual rate of more than 10% in the growth, has huge development potential and application prospect is very broad [1] [2] [3]. UV radiation curing technology involves wide, industry, thus gained by the radiation curing technology and its various materials and the product is known as the 21st century green industry technology and products.

  With the gradually mature of ultraviolet radiation curing technology, the market gradually expanded, the uv light radiation of accurate measurement is increasingly important. Ultraviolet radiation intensity of illumination can/meter is a kind of relatively reliable performance, convenient use of wide band ultraviolet radiation testing equipment, used for quantitative measurement of uv light reaches the coating on the surface of the radiation intensity of illumination or radiation energy. Ultraviolet radiation measurement can provide reliable parameter basis for the production of the component, strengthen quality control, reduce the wastage of the products, energy saving, consumption for manufacturers and end use customers provide defined quality standards in the production. Due to ultraviolet radiation intensity of illumination/energy meter's own characteristics, in order to ensure accurate and reliable measuring results, must be measured in accordance with regulations on a regular basis to the authority department for calibration.

      This paper from the measurement problems in the field of ultraviolet radiation curing, the ultraviolet radiation measurement and calibration method and importance are discussed in this paper. Uv radiation curing was introduced in detail in the field of commonly used terms, radiation measurement, and quantity traceability of ultraviolet radiation measurement system in our country, the international comparison results and international consistency of the value, finally discussed the measurement issues that should be paid attention to in the field of ultraviolet radiation curing.

Spectral radiometric measurement terms

      Often used in the field of ultraviolet radiation curing, the spectral radiation metrology terms in order to facilitate understanding and international communication, ought to use these terms, otherwise easy to cause confusion.

Table 1 lists the commonly used in the field of radiation curing radiation measurement terms, unit and definition of [4].

Table 1. Radiation measurement terms, unit and definition

名词术语 (nomenclature)	符号 (symbol)	定义 (define)	公式 (formula)	单位 (unit)
辐射能量 （Radiant energy）	,	在指定的时程 内，辐射通量的时间积分 （within a specified time history of radiation flux integral）		J (焦耳)
辐射通量/辐射功率（Radiant flux/ Radiant power）	, /	以辐射的形式发射、传输或接收的功率。 （In the form of radiation emission and power transmitted or received.）		W (瓦特)
辐射强度 （Radiant intensity）	,	点辐射源在指定方向上的辐射强度是该辐射源在包含指定方向的立体角元内传输的辐射通量 ，除以该立体角元之商。（Point source in the specified direction of radiation is the radiation source specified in the include direction within the solid Angle of yuan transmission radiation flux, divided by the quotient of the solid Angle per person.）		W·sr-1 (瓦特∕单位立体角)
辐射亮度 （Radiance）	,	由公式 定义的量。式中 是由经过实际或假想面上指定点的束元在包含指定方向的立体角元 内传播的辐射通量，是包含指定点的该辐射束截面积，是该截面法线与辐射束方向之间的夹角。(The amount of defined by the formula. Type is specified by a real or imaginary plane beam direction of solid Angle specified in the include yuan In the spread of radiation flux, contains the specified point of the radiation beam cross-sectional area, the cross section of the normal and the Angle between the direction of the radiation beam.)		W·m-2·sr-1（瓦特∕平方米·单位立体角）
辐射照度 （Irradiance）	,	表面上一点处的辐射照度是入射在包含该点的面元上的辐射通量除以该面元面积之商。(On the surface of the radiation intensity of illumination is incident on the bin contains point of radiation flux divided by the surface area of the business.)		W·m-2（瓦特∕平方米）
辐射出射度 （Radiant exitance）	,	表面上一点处的辐射出射度是离开包含该点的面元的辐射通量 除以该面元面积之商。(Point on the surface of the radiant exitance is left contain radiation flux of the point Divided by the surface area of the business.)		W·m- 2（瓦特∕平方米）

   
   Our country has established the ultraviolet radiation metrology equipment

     Spectral radiant intensity of illumination is one of the important basic optical field value, is the world each country independent repetition, save the important reference value, also is the source of all ultraviolet radiation measurement source.Spectral radiant emittance of national reference unit was built in 1975, is 250 nm to 2500 nm wavelength range, covering the ultraviolet, visible and near infrared wavelength range, 30 years for our country's spectral radiation luminance and illuminance meter provides the highest standards of measurement. (250 ~ 2500) nm spectral radiation national reference device is the source of the ultraviolet radiation measurement system quantity traceability, in order to meet the demand of a growing number of ultraviolet radiation measurement, in 1989 our country build a reference unit of ultraviolet radiation intensity of illumination is used to carry out various kinds of uv light source and ultraviolet rad iation intensity of illumination/energy meter calibration work, to ensure that the internal unity of the value. Figure 1 is the ultraviolet radiation measurement system sche matic diagram.

     
  Figure 1 the system schematic diagram of uv radiation measurement delivery in China; Figure 2 ultraviolet radiation intensity of illumination of the working reference unit in our country


  Ultraviolet radiation intensity of illumination benchmark work mainly by the spectral radiant intensity of illumination standard lamp, uv spectroradiometer, ultraviolet radiation, all kinds of uv light illuminance meter, etc (see figure 2). In 1989, according to the market needs, establish four bands of standards. A1 band: 320 nm to 390 nm, lp: peak wavelength 360 nm + / - 5 nm; A2 band: 365 nm, the peak wavelength of lp: 1 nm to 365 nm +, peak and a half high width of Dl < 10 nm; Band B: 290 nm to 320 nm, lp: peak wavelength 310 nm + / - 5 nm; C band: 253.7 nm, peak wavelength of lp: 253.7 nm + 1 nm, peak and a half high width of Dl < 10 nm.
  In order to meet the market of high-energy multiband ultraviolet radiation intensity of illumination/energy meter calibration requirements, our hospital has established the high-energy ultraviolet radiation intensity of illumination/energy meter and multiband ultraviolet radiation intensity of illumination/energy meter standard device, using spectral radiometer absolute measure the spectral radiant intensity of illumination light source of the application, then to integration of specific wavelengths, obtained the integral radiation intensity of illumination.

Ultraviolet radiation measurements of international comparison and international consistency of the value

  International BIPM bureau of standard measurement is the most authoritative organization of measurement, sets professional committee of photometric radiometric CCPR, the aim is responsible for organize regular worldwide international comparison of optical radiation measurement, to ensure that the value of international consistency.

  Ultraviolet radiation intensity of illumination/energy meter is quantitative measuring instrument for ultraviolet radiation intensity of illumination of light/energy, is widely used in aerospace, military defense, industry and agriculture, health care, electric light source and environmental protection and other fields. So far, however, haven't international calibration of the broadband uv radiometer related standards and specifications. In December 2002, the asia-pacific metrological organization APMP organized "the intensity of illumination with the UVA detector responsivity" international comparison, is for the first time this type on the international comparison, designed to assess each participating laboratory photoelectric detector in calibration and measurement of UVA light response degrees of equivalence.

  Than leading laboratory is Singapore, Australia, South Africa, Japan, Taiwan, South Korea, China, New Zealand, Singapore and other eight national laboratory to attend because time over exit than conflict (New Zealand). Table 2 is each participating laboratory and the relative deviation between the international reference and uncertainty.

Table 2 each participating laboratory and the relative deviation between the international reference and uncertainty

实验室 （laboratory）	365nm		UVA
	D (%)★	UC (%)★	D (%)★	UC (%)★
澳大利亚NMIA	-0.50	1.2	-0.65	1.0
日本NMIJ	1.30	2.8	2.24	4.7
南非CSIR	5.54	4.0	7.72	7.5
台湾ITRI	3.39	1.8	3.80	1.6
韩国KRISS	-1.32	1.2	-3.36	1.7
中国NIM	-0.25	2.1	-0.29	2.1
新加坡SPRING	-0.52	1.6	-0.01	2.4

★  D   and the relative deviation between the international reference
★  UC measurement standard is not confirmed
  International comparison shows that the ultraviolet radiation intensity of illumination of our country's (NIM) measurement level in a leading position in the world. For narrow band UV365 illumination responsivity, quantity of our country and the international reference the closest, deviating from the quantity is only 0.25%; For wide band UVA light responsivity, the quantity and the magnitude of the deviation between the international reference 0.29%.

   In 1999, the institute of metrology, on behalf of the Chinese in the international (BIPM) bureau of standard measurement signed the "national measurement standard and the calibration and measurement certificates issued by national metrology institutes mutual recognition agreement". Ultraviolet radiation intensity of illumination calibration project was listed in the international quality in our country and the relevant amount of calibration/test (CMC) mutual recognition program. Therefore, the certificate issued by the China metrology institute with the international generality.

  Ultraviolet radiation measuring important role in the field of ultraviolet radiation curing

  How to ensure the quality of the printing ink, paint, and other products, how to truly realize the energy saving of production efficiency? Along with the development of science and technology, the enterprise in the pursuit of the number of products at the same time, more and more attention to the quality of the products and the production efficiency, and measurement is an effective technology to ensure product quality.

  Engaged in ultraviolet radiation curing enterprises are rapidly increasing,more and more manufacturers have realized quantitative measurement of ultraviolet radiation on the importance of the product.Is common problem is: when buying ultraviolet radiation test equipment of the same, not clear whether the instrument need to be calibrated regularly, where should be calibrated, the calibration cycle is how long? Some people think that foreign measurement standard must be better than China, rather than relying on foreign manufacturers standard, also do not want to place your trust in me the national standard. Some units in the process of research paint or ink formula, no ultraviolet radiation intensity of illumination with full awareness of quantitative measurement problem, once the product has a problem, can't make rapid and accurate judgment, do not know is the problem that the light source or the problem of glue or paint, seriously affected the production efficiency.

5.1  The importance of quantitative measurement in the field of radiation curing

  Uv light source is in use process, with the increase of time, gradually decay radiation intensity of illumination. When the radiation intensity of illumination is less than certain value, the radiation process cannot be completed, the value is known as the critical value. When the radiation intensity of illumination is lower than the critical value, light can't continue to use, must be replaced. Otherwise it will cause serious influence to production process and product quality. Deep ultraviolet radiation intensity of illumination of coating curing has a direct impact. When the strong ultraviolet radiation intensity of illumination, but under the condition of invariable radial according to time, will produce coating aging, if ultraviolet radiation intensity of illumination is too weak, cannot achieve good curing effect.

  Ultraviolet radiation intensity of illumination/energy meter is to reach the surface of the coating uv light source professional quantitative measurement of the radiation intensity of illumination/energy of the instrument, provides reliable parameter basis for product production process, and encourage enterprises to strengthen quality control, to achieve the purpose of save energy, reduce rejection rate, and for uv equipment manufacturers, coating, printing ink manufacturers and end use customers provide defined quality standards in the production.

5.2  The necessity of measuring instrument calibration on a regular basis

  Through the use of ultraviolet radiation intensity of illumination/energy meter for quantitative measurement of light sources such as uv curing, implements the qualitative to the quantitative transformation, to ensure that the quality of the products. There was no unified international on ultraviolet radiation measurement standards, leading to different countries, different instruments manufacturer production quantity. Another compared with optical measuring instruments, the stability of the uv radiation intensity of illumination/energy meter is relatively poor, value easy to change. Based on ultraviolet radiation illuminance meter national verification regulation JJG879-2002, in order to ensure that uv radiation measuring value in the field of unification, must be conducted regularly to the provisions of the metrology department calibration, calibration cycle for a year, according to the instrument's shorten appropriately use frequency and accuracy requirements.

  Ultraviolet radiation intensity of illumination/energy meter special structure is another important reason should be calibrated on a regular basis.Because of the limitation of technological level and the technical conditions of ultraviolet illumination/energy meter UVA filter easy to mildew occurred in damp environment,UVC filter peak may drift over time, these factors directly affect the stability of the value.Verification regulations require uv light meter probe must be stored in dry container,to prevent the possibility of mildew.But due to the special working environment, in the field of ultraviolet radiation curing as well as the measuring probe and display instrument integration conditions, place the meter long dry environment is unrealistic. Therefore, more likely to change the value of the instrument.

  Ultraviolet radiation curing used in the field of light source is commonly high uv light source, measuring instrument of detector material under the strong ultraviolet light irradiation for a long time, it is easy to aging, affect stability of the value of the instrument.

  Above all, regular calibration of ultraviolet radiation intensity of illumination/energy meter is very necessary, is the only way to ensure accurate and reliable value.

   conclusion

   Radiation curing technology after nearly 30 years development, has been widely used for coatings, inks, adhesives and electronics, and many other areas. Commonly used in the field of radiation curing were introduced in this paper the radiation measurement, definitions, and units, the specification using radiometric measurement terms. Understand our country's degree of ultraviolet radiation metrology, standards and dissemination traceability system, through the international comparison results clearly China measurement standard and international standard of equivalent mutual recognition. Finally introduces the importance of measurement in the field of ultraviolet radiation curing, uv radiation intensity of illumination/energy meter reach the surface of the coating is the quantitative measurement of radiation intensity of illumination/energy professional quantitative measurement instrument, regular calibration of measuring instruments is the only way to ensure accurate and reliable value.

  The application of ultraviolet radiation curing technology are developing rapidly, the importance of quantitative measurement of ultraviolet radiation is being accepted and attention.

  China institute of metrology has been committed to continuously improve the degree of uv radiation measuring ability and level, for each application domain to provide accurate and reliable measurement standard.

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