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1

Parametry sensytometryczne płyt fotopolimerowych służących do wytwarzania form fleksodrukowych cyfrową metodą laserowo-fotochemiczną

Harri L.

Polimery

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2010

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T. 55, nr 11-12

863-868

PL

Wyznaczono parametry sensytometryczne wybranych płyt fotopolimerowych przeznaczonych do wytwarzania form fleksodrukowych cyfrową metodą laserowo-fotochemiczną. Sporządzono krzywe charakterystyczne badanych płyt opisujące funkcyjną zależność grubości fotoutwardzonej warstwy światłoczułej od dziesiętnego logarytmu naświetlenia. Określono względną światłoczułość progową (S0) i współczynnik szybkości fotoutwardzania (fotosieciowania) warstwy światłoczułej (W). Parametry te wyznaczano stosując równania regresji liniowej opisujące odcinki prostoliniowe krzywych charakterystycznych poszczególnych płyt fotopolimerowych. Wykorzystując równania regresji określono również optymalny czas naświetlania wstępnego badanych płyt zapewniający niezbędną głębokość reliefu formy fleksodrukowej. Zastosowana metoda wyznaczania parametrów sensytometrycznych płyt fotopolimerowych pozwala na ilościowe porównanie różnych płyt fotopolimerowych pod względem ich parametrów sensytometrycznych oraz na ustalenie, w wyniku rozwiązania określonych równań regresji, optymalnego czasu naświetlania wstępnego dużej liczby rozmaitych płyt przy zmianie żądanej głębokości reliefu formy fleksodrukowej lub zmianie płyty fotopolimerowej. Wykorzystując zgromadzone dane można też, dobierając odpowiednie parametry, sterować procesem naświetlania wstępnego płyt fotopolimerowych.

EN

The sensitometric parameters of selected photopolymer plates designated for use in the production of flexographic forms by the digital laser-photochemical method have been determined. Characteristic curves for the selected plates indicating the dependence of the thickness (d) of the hardened photosensitive layer as a function of the logarithm of irradiation (log H) were obtained (Fig. 2). The relative photosensitivity threshold (S0) and the coefficient (W) of the rate of photohardening (photocrosslinking) of the layer were evaluated (Tables 1,2). The linear regression equation method, which describes the linear fragments of the obtained curves, was applied to determine the sensitometric parameters of these photopolymer plates as well as the optimal period of preliminary exposure required to achieve an appropriate depth of relief of the flexographic printing form (Fig.l). Moreover, this method allows for a quantitative comparison of different photopolymer plates, taking into consideration their sensitometric parameters, and the determination of the optimal preliminary exposure duration for a large number of different plates after a change either of the required relief depth of the flexographic printing form or of the photopolymer plate itself. The accumulated data can serve as an essential tool in selecting the most suitable parameters and controlling the preliminary irradiation process of the polymeric plates.

2

Model examinations of edge effects in light-sensitive materials

Rajkowski B., Nowak P.

Optica Applicata

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2001

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Vol. 31, nr 1

185-191

EN

The results of theoretical examinations of the dependence of edge effects on the optical density, which influence directly the contour sharpness in the image, are presented. Besides, the results of calculations of the influence of contrast in the characteristic curve of the radiation sensitive layer on the shape and properties of the limiting curve are shown. The results obtained are presented in the form of functions of changes in the relative edge enhancement indicator and maximum gradient of the limiting curve as dependent on the level and difference of the optical density in the image and background, respectively.

3

Model examination of the reflex-halation in single-layer light-sensitive system

Latacz L., Nowak P.

Optica Applicata

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2001

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Vol. 31, nr 2

499-506

EN

The results of computer simulation of the effects of light scattering in a system composed of single silver halide light-sensitive layer coated on a transparent base are presented. The scattered light penetrating the base film can suffer from internal reflection from its lower surface and thus contributes to some loss of image sharpness. This effect, called reflex-halation, is very disadvantageous. The qualitative dependence of the MTF curve of the system on its geometric and optical parameters is examined. It has been shown, among others, that the deterioration of image quality is stronger for the thinner light-sensitive layer and is more elongated for the elementary scattering indicatrix of silver halide crystals. The result is similar to that obtained in the case of crossover effect, though in the presence of the antihalation layer the observed dependences are opposite to those just mentioned.

4

Model examination of application of fluorescent substance to silver halide light-sensitive layers

Latacz L., Nowak P.

Optica Applicata

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2001

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Vol. 31, nr 1

165-175

EN

The results of computer simulation of the outcomes of scattering, fluorescence and absorption of actinic light inside the hypothetical light-sensitive layer containing the silver halide crystals and fluorescent substance are presented. It has been assumed that the modelled layer is exposed exclusively to the radiation of the wavelength belonging to the intrinsic sensitivity range of silver halide. The quantitative dependence of the effective light absorption by the silver halide on the fluorescent substance concentration, the layer thickness, quantum efficiency of fluorescence and the ratio of the absorption probability of a photon of wavelength belonging to the sensitized sensitivity range and the absorption probability of a photon of the wavelength from the intrinsic sensitivity range has been examined. Also, the dependence of the modulation transfer function curve on the above parameters has been studied. The results obtained indicate that under some circumstances an addition of fluorescent substance can enhance the photosensitivity of the layer and improve simultaneously the sharpness of the recorded image.