Method for Estimating a Spectral Reflectance Value to be Expected of a Layer System

Abstract

The aim of the invention is to provide a method for estimating a spectral reflectance value to be expected of a layer system consisting of a layer sequence of materials and printing inks that involves reliably predicting the appearance of the desired print. This aim is achieved according to the invention by providing a method for estimating a spectral reflectance value to be expected of a layer system consisting of a layer sequence of materials and printing inks, in which: a) firstly the values are determined for each individual layer in relation to i) the spectral transmission at the interfaces of the layer, ii) the spectral reflectance at the interfaces of the layer, iii) the spectral absorption in the layer volume, and iv) the spectral scattering in the layer volume; b) a resulting reflectance value is ascertained from the determined values in relation to the layer sequence by following the various light paths in a sequential course through the layers.

Claims

1. Method for estimating an expected spectral reflectance value to be expected of a layer system consisting of a layer sequence of materials and printing inks, the method comprising: a) firstly, determining, for each individual layer of the layer sequence, values for i) a spectral transmission at interfaces of the individual layer, ii) a spectral reflectance at the interfaces of the individual layer, iii) a spectral absorption in a layer volume of the individual layer, and iv) a spectral scattering in the layer volume of the individual layer, b) ascertaining a resulting reflectance value from the values determined in step a) for the layer sequence by tracing the different light paths in a special path through the individual layers.

2. Method according to claim 1, characterized in that the sequential course through the individual layers corresponds to a theoretical observation of a light beam impinging on the surface of the layer system and a course of the light beam through the individual layers and a remaining reflection.

3. Method according to claim 1, characterized by respectively determining the spectral transmission, the spectral reflectance, the spectral absorption, and the spectral scattering as a function of a wavelength λ.

4. Method according to claim 1, characterized by approximating the spectral transmission in an estimation method.

5. Method according to claim 1, characterized by measuring the spectral absorption.

6. Method according to claim 1, characterized by arranging a foil as an uppermost layer of the layer system.

7. Method according to claim 1, characterized by positioning the layer system on white and/or black substrates when performing step a).

Description

[0021] Further advantages and features of the invention will be apparent from the following description with reference to the figures. Thereby showing:

[0022] FIG. 1 a schematic representation of a layer to explain transmission and reflection;

[0023] FIG. 2 an illustration according to FIG. 1 for explaining absorption and scattering and

[0024] FIG. 3 a representation of a layer system for explaining the method according to the invention.

[0025] According to FIG. 1, a light beam 2 of known wavelength A is sent into a layer 1 to be assumed. Reflections 4 take place at the boundary surfaces, remaining light components penetrate the layer and represent the transmission 3. At a possible substrate, the light beam is reflected and can thus experience a further reflection 4 of the layer and a residual transmission 3, which continues to emerge to the outside.

[0026] According to FIG. 2, a portion of the light 2 is absorbed in the layer 1 due to the printing ink or pigments, which is symbolized by the bar 5. A further portion is scattered within the layer in its volume by internal reflections, which is symbolized by the arrow bundle 6.

[0027] The interaction of all the above cases in a layer system is shown in FIG. 3. In the embodiment shown, a light beam 10 passes through layers 11, 12, 13, 14, 15 and strikes a measuring substrate 16.

[0028] The measuring substrate 16 is white or black.

[0029] In the embodiment example shown, the uppermost layer 11 is a film, layers 12 and 13 may be ink layers applied to an ink layer 14 by overprinting. By 15 is indicated, for example, a support, paper, foil, metallic foil, aluminum or the like. An air gap can be seen between 15 and support 16 as part of the layer system.

[0030] In each of the layers, transmissions, reflections, absorptions and scatterings take place as described above, which is indicated by the different arrows. The light beam 10 passes through the foil 11 and experiences reflections in the interfaces. The rest of the light enters the ink layer 12, where absorption, scattering, reflection take place and another rest of the light 10 enters the layer 13. This process repeats itself until the residual light is reflected at the white measuring substrate and the light beam traveling upward experiences the same reflections, absorptions and scatterings in each of the layers, so that finally a remaining part emerges.

[0031] After the behavior of each individual layer with respect to transmission, reflection, absorption and scattering has been predetermined, the resulting reflectance value can thus be determined using the method according to the invention.

REFERENCE CHARACTERS

[0032] 1 layer [0033] 2 light beam [0034] 3 transmission [0035] 4 reflection [0036] 5 beam [0037] 6 arrow bundle [0038] 10 light beam [0039] 11 foil [0040] 12 layer [0041] 13 layer [0042] 14 layer [0043] 15 layer [0044] 16 measuring pad