1. density measurement in the role of packaging and printing
"Density" in the physics concept is the object surface characterization of the absorption of light by nature, if radiation flux for φ 0, reflex luminous flux for φ, the density of defined as:
Type: D for density or say absorbance; R = φ 0 / φ called reflectivity.
Due to the object in the absorption of the energy of the visible light, the light intensity weaken. The light absorption is affected by lambert (Lamber) law and bill (Beer) law control, lambert, the bill law, points out that in a certain wavelength, light absorbing capacity and absorption material is proportional to the concentration, and the thickness of the material suction light relevant, mathematical expressions for:
Type of: alpha λ for absorption index or called extinction index, it and absorption of the molecular structure of the object, but also related to the wavelength of light irradiation on; L for the thickness of the material suction light, C for absorption material contained in the pigment concentration.
According to lambert - beer's law, in printing, use reflection density can easily judge printing ink layer thickness l or concentration c size, the reflection density D can be used to control in the process of printing ink amount of change.
In the actual printing, printing ink density with not only the nature of the ink itself has a complicated relationship, and density D is not because of ink and ink layer thickness change and the increase of the infinite. Most of the paper printing ink thickness in 10 μ m or so will reach saturation state, density value no longer increases. A saturated state density value is D ∞, have the experience formula:
Type: m is with the print paper smoothness relevant constant.
The type discussion shows that the density is to describe material absorption properties of an objective physical quantity, also can use spectral density to describe the physical spectral absorption properties, and this is called selective absorption. What say here density measurement process is a physical process, and people's eyes and subjective feeling matter, Or and people's physiological and psychological factors have nothing to do.
Based on the density the physical properties, in the modern printing medium density for values to control the ink intensity (ink layer thickness or concentration), computing network area rate, network gain, relative contrast value, dieyin efficiency, etc; In the ink color quality testing, can be used to determine the density of the original color is gray and hue error, etc. In a word density and density measurement method, the printing technology development, which plays a large propulsion function, is a more mature technology. American p. toby, o in a printing association annual meeting said: "the United States recognized the printing industry in the past 10 years, the most useful measuring instrument is densitometer." 2 color density measurement
In the printing industry use of special color measurement instrument is densimeter, it is to use red (R) green (G) blue (B) such color piece and a measuring shade with visual color piece (L), therefore, for any printing, use the color densitometer four color filter can be measured respectively 4 density value, recorded as DR, DG, DB, DL. The essence of density measurement is still depends on the surface spectral reflectance. The above four density value measurement is each spectrum interval reflection and absorption of the total, and them as objective quantitative said color characteristic parameter is effective data. Due to the ink spectral selective absorption performance in decided to ink color, play the leading role. Therefore, with the density value to determine the characteristics of the printing ink and the quality of printing industry is a kind of more accurate method. (Gold Printing Group) |
