| The time sequence examination of crossed stamp impression and ink is an important item in the judicial identification of documents.At present,in practice,the examination method mainly depends on the observation and analysis of the microscopic characteristics of the crossed area based on experience.However,due to the difference in the time interval between the forming sequence of the cross area of the stamp and printing,especially in cases where the materials have certain permeability between each other,it is easy to cause cognitive confusion of experts due to "false positive" characteristics.The interaction and joint movement of the two materials will also affect their microscopic characteristics after the formation of the intersection.In view of this,this paper considers the two-time factors involved in the time series test of crossed stamp impression and ink,and sets different time intervals(30min,1 day,7 days,30 days)for printing and stamp impression and different observation time(30min,1 day,7 days,30 days)after the formation of the crossed area to observe its diachronic characteristics by controlling variables.At the same time,due to the different physical and chemical properties of different printing materials and stamp materials,this experiment collected five kinds of stamp materials(Waterborne pigment stamp oil,oil-based dye stamp oil,atomic stamp oil,photosensitive stamp oil,stamp mud)that are more common and easily available on the market,as well as commonly used office printing materials(laser printing and inkjet printing),and combined them in two,In order to observe the microscopic characteristics of the crossed areas under different combinations.Through the experiment,it is found that,in terms of diachronic characteristics,the microscopic characteristics of laser printing ink and oil-based stamp color can be observed to change with time at the cross parts,mainly reflected in the mutual fusion of materials,the diachronic characteristics of water-based stamp ink have no reaction basically,and the diachronic characteristics of oily dye(Liberty)ink have little change;However,the diachronic characteristics of the combination of ink jet printing and five kinds of stamp inks are basically not reflected.In terms of the impact caused by different time intervals,in terms of the influence caused by different time intervals,for laser printing files,the time interval factor of character formation mainly affects the microscopic characteristics of the cross parts of character under the sequence of first stamp and then printing,which is mainly manifested by the different degree of dissolution and incomplete characteristics of the text material,However,for oil-based dyes(Liberty),the microscopic characteristics of the cross part with different time intervals are not obvious;The micro-characteristics of the intersection of ink-jet printing documents are mainly affected by the time interval which is also concentrated in the time sequence of stamp first and printing later,mainly manifested by different degrees of scattering and incomplete characteristics of printing materials,but in the oily dye(Liberty)stamp and inkjet printing,there is still little change.This paper also carried out targeted experimental research on the identification of sequence in the case of less ink,and tested it with fluorescence microscope as a supplementary means of common microscopic observation.The experimental results show that when the printing color is pale to a certain extent,the influence of double time factors on the microscopic characteristics of ink sequence at the intersection of printing cannot be reflected,and for inkjet printing documents,When the stamp is pale,its "false positive" feature is obvious,and it cannot be effectively distinguished even by using fluorescence microscope. |
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