Research On The Fluorescence Examination In The Sequencing Of Stamping And Printing

Sequencing of stamping and printing is an important problem in forensic document examination.Along with the growinghigh technological and Intellectualized tendency in crime methods,inspections on sequencing of stamping and printing also be subjected to the value more and more,and also become the hard problem to solve for the judges. The causes for the formation of the problem are almost because of the reserved seals with blank pages or stealing seals by the forgers and changers,and if necessary, to add the required contents.Therefore,the the sequence of inspecting the documents writing and the formation of seals has become the key problem to to judge files’ authenticity and the relative time.For a long time,the practice take use of advanced science and technology and equipment,developed and improved many for sequencing of stamping and printing identification techniques,which in general can be divided into two categories, nondestructive inspection and damage inspection.Non-destructive inspection mainly consists of stereoscopic microscope test,three-dimensional microscope test, document examinations and Raman spectroscopy,etc.Damage inspection are mainly made of intersection methods of sectioning microscopy, decolorized methods and tripping pressure transfer method, etc. When inspected,we should choose the appropriate testing method according to the different conditions of examination to obtain good results.Fluorescence examination belongs to the nondestructive examination of sequencing of stamping and printing,which mainly includes two specific methods,that is,file tester fluorescence examination and microscopic fluorescence test.For a long time, fluorescence examination lack systematic research,combined with the traditional comparative mature testing method of sequencing of stamping and printing,this paper using file tester fluorescence test and microscopic fluorescence test method.Based on the file tester fluorescence examination and microscopic fluorescence test, focusing on the research methods of common writing materials, sealing materials and the check results of the sequence,to perform a statistical analysis and summary of the results,the data and the comparative rules of observation.First of all,to analyze and classify the writing materials and the resealing materials.The writing materials and the resealing materials are the most important factors of sequencing of stamping and printing.The paper materials,the writing power,the writing pads, the resealing power and the resealing pads,etc.are less important factors.And also to analyze and classify the writing instruments,the main composition and function of writing pigment,the features of writing materials forming the handwriting and the resealing,the resealing pigment,the features of resealing materials forming the print.We divide the writing materials into black oil ballpoint pens,black neutral pens,black gel pens,black pens, black-blue pens, true blue pens and the traditional carbon paper based on overall analysis and we divide the resealing materials into atomic ink, photosensitive ink,oil stamp pads,dye ink,process ink pad and traditional ink.Secondly,we make the samples of the 215 writing materials and the 69 resealing materials which are chosen from the experiment,based on the fluoroscopic examination and fluorescence microscopic observation by the document examination instrument.To analyze and summarize the commonly used writing materials and resealing materials from the perspective of the fluorescence characteristics of handwriting and imprinting.Through observation it can be found that:1.the fluorescence characteristics of handwriting and imprinting can be divided into two kinds,that is to produce a fluorescence and to maintain the "primary" with no fluorescence.Produce the fluorescence can be divided into strong fluorescence, relatively strong fluorescence,general fluorescence intensity, more bright and red fluorescence;maintaining the "primary" with no fluorescence can be divided into very clear primary color, general clear primary color, color with light and almost disappearing color.2.In the case of fluorescent material can be revealed.The duration of light exposure influences deeply on the intensity of fluorescence appearance. They have positive correlations.To appropriately extend the duration of light exposure can enhance the intensity of fluorescence appearance.3.Under the condition of the microscopic fluorescence test,the writing pigment distribution and writing ink layer is different form different writing materials handwriting.In general,most writing material forming the handwriting can be the "primary" with no fluorescence,a small amount of stimulated emits the intensity of different fluorescence;most resealing materials forming the seals motivated can emit visible fluorescence,which most belongs to the strong fluorescence.The fluoroscopic examination and fluorescence microscopic observation by the document examination instrument to the rare material whether can be tapped into fluorescent test results will be different,and results the differences in a small number of materials about fluorescence intensity and the test results of the "primary" clear degree,most of the rest of the test results are the same.Finally,according to the existing test results, to select representative writing materials and resealing materials to make the sequencing of stamping and printing experimental samples.To make a comparative observation,research and summary of the sequencing of stamping and printing in the way of fluorescence microscopic observation,the main conclusions in this paper are as follows:First,the observation effect of fluorescence intensity and intensity change from the writing materials and sealing materials through file tester fluorescence test turn out to be ideal.The comparing test of problems of sequencing of stamping and printing writing materials and writing ink layer along with the traditional ink pad cover color turn out to be ideal,too.Second, the observation of the pigment distribution state of writing materials through the microscopic fluorescence examination get to a relatively ideal effect.Compared with the normal light microscopic examination,microscopic fluorescence examination can observe the microscopic distribution form of writing pigment and the relationship between the paper fiber and sealing materials more clearly and more directly.The effect of the paper fiber form and clear degrees through fluorescence examination is also very ideal.Third,there are a few theories about the sequencing of stamping and printing examination of the pen ink and oil sealing materials form files through microscopic fluorescence examination in observational studies.In the case of the ink before printed images,pen ink directly form the handwriting on the paper.1.The appearance of paper fibers become more apparent after directly contacting with strong water properties’ writing material.2.Because of the ink strong distribution regularity of pen ink,writing ink is easily into the paper fibers and would distribute in a line along the paper fibers.In the case of the ink before printed images,oil sealing materials first form imprinting on the paper.1.The paper fiber is not obvious after directly contact with oily cover printed materials in most situations.2.The writing material present to be flaky,patch shape, dot, dot, short rod,and there will be no linear distribution along the paper fiber morphology.By observing the differences and similarities in the form distribution of the sequencing of stamping and printing cross area and the non-cross areas’ handwriting materials,which can better examine the sequencing of stamping and printing of pen and ink oily sealing materials.But for the examination effect of irregular distribution and sealing material form files,although there exists some certain characteristics which can be summarized,but they are not stable.Fourth, in the conditions of the same writing conditions and writing materials along with the sealing materials,except from some strong fluorescence characteristics of the relationship of writing materials formed sequencing of stamping and printing problems and also the problem of the writing ink layer cover color of material layers(just for comparison examination, and should enhance the difference of fluorescence intensity processed by the images),in most cases,the differences of fluorescence characteristics ink before printed images and printed images before ink are not that big.The results of the differences between them from the test results and theories are quite large.Speculating the main reason maybe that,he "black" writing pigment has strong light absorption in the conditions of fluorescence examinations.And the lower the pigment layer transparency,the darker the writing ink color,the better the coverage,and also the pigment of light absorption will be stronger,the effect of absorbing excitation light or a light turns to be bad.Next, because the writing ink layer and sealing layer are not a simple complete coverage,but a relationship between similarity to interact with each other,so when the poor fluorescence characteristics cover the strong one,it will not completely cut off strong fluorescence properties of materials stimulated emission fluorescence, and the effect in reducing fluorescence is not obvious.When the strong fluorescence characteristics cover the poor one,the effect emitting fluorescence is not obvious as well.Thus,the fluorescence examinations based on the theory of fluorescence spectrum principles should consider the two factors above.