JP2008215914A - Inspection method of cultural properties by terahertz spectral diffraction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inspection method of a cultural property for identifying a material used for manufacture, by analyzing the cultural properties by means of a nondestructive method. <P>SOLUTION: A method for analyzing a material included in cultural properties includes at least one material between a die, a pigment, a color developing agent and a surface protection agent used for the cultural property is applied and cured onto a basic material fully transmissible by terahertz waves, whose absorption or reflection spectrum is known, to thereby prepare a sample; the sample is irradiated with the terahertz waves having an approximately continuously-different wavelength, and the absorption or reflection spectrum is determined by a transmission or reflection spectroscopy; a material applied onto the basic material is changed, and the absorption or the reflection spectrum in each sample is determined, and thereby each absorption or reflection spectrum database of the terahertz wave by various materials, such as the die, the pigment, the color developing agent or the surface protection agent used for the cultural properties is acquired; and the cultural property which is an object of analysis is irradiated with the terahertz wave and its absorption characteristics are analyzed, based on each acquired database, to thereby identify a material included in the cultural property. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for analyzing a substance contained in a cultural property.

  Cultural properties fade or change in quality over time, and pigments may peel off. Therefore, repair work is necessary for cultural assets. In order to carry out repair work, it is necessary to identify substances such as pigments used in the production of cultural properties.

  Here, cultural assets refer to art works in a broad sense whose surface is decorated with at least one of dyes, pigments, color extenders, and surface protectants. Specifically, paintings, pottery Arts and crafts such as textiles, sculptures, musical instruments, antiques, and antiques.

  Substances used for cultural properties, especially coloring agents and surface protection agents for fixing pigments, vary depending on the era of production. Therefore, by identifying these substances, it is possible to clarify the original production time and the restoration history in the middle, and contribute to the study of art history. Further, by determining the production time, it is possible to provide information useful for authenticity assessment.

  In order to restore cultural properties such as cleaning, filling, and painting, it is necessary to investigate and analyze the target material first. Conventional analysis methods include the following means.

  In a destructive test such as a chromatograph, it is necessary to burn or dissolve the sample. Therefore, even a part that does not impair the artistic value is not suitable for cultural assets because it cannot maintain the current status.

  Infrared, ultraviolet camera, and oblique light photography are used to get an overview of the entire cultural property, whether different types of materials may have been used or whether there are different parts of writing. However, the substance cannot be identified.

  Various analysis methods using X-rays and electron beams were analyzed for inorganic materials such as stoneware and earthenware, and metals. Even for pigments, it was limited to the identification of metal elements contained therein. Therefore, it can be applied to the field of archeology. However, since there is a possibility of deteriorating organic materials and the like, it is impossible to identify organic substances such as dyes, color formers and surface protective agents used in paintings from the Middle Ages onwards.

  Similarly, infrared spectroscopy is difficult to identify organic materials because there is an increase in temperature on the surface of the object, and all the absorption based on the structure between atoms in the molecule appears.

  In analysis methods using millimeter waves or even lower frequency electromagnetic waves, absorption specific to a substance rarely appears. Regarding cultural properties, there are some examples such as non-destructive measurement of moisture absorption of paper products using relatively strong absorption of moisture.

Conventional techniques for analyzing substances contained in cultural properties include the following means.
JP 2006-53070 “Dye Estimation Method” Japanese Patent Application Laid-Open No. 2004-340750 “Cultural property alteration assessment method, alteration assessment device and alteration causative substance identification method”

Patent Document 1 discloses that a pigment such as a pigment or a dye applied to a cultural property is estimated to contribute to a digital archive.
Japanese Patent Application Laid-Open No. H10-228667 discloses that an evaluation regarding alteration due to a chemical substance in ambient atmospheric gas is performed from surface state information obtained by analyzing the surface of a cultural property by Raman spectroscopy.
However, none of the conventional techniques disclose a means for identifying dyes, pigments, color formers, and surface protective agents that can be used for cultural properties.

On the other hand, there are the following conventional techniques for analysis methods using terahertz waves, which have recently been put into practical use.
JP 2005-265793 “Specific Substance Detection Device” "Inspection method and equipment for goods" Japanese Patent Application Laid-Open No. 2004-61455 “Powder Physical Property Measuring Apparatus and Method Using Terahertz Electromagnetic Wave”

  However, none of the prior arts discloses a means for identifying dyes, pigments, color formers, and surface protective agents that can be used for cultural properties using terahertz waves.

  Therefore, an object of the present invention is to provide a method for inspecting a cultural property by analyzing the cultural property by a non-destructive method and identifying a substance used for the production.

 In order to solve the above-described problems, a cultural property inspection method using terahertz spectroscopy according to the present invention has the following configuration. In other words, it is a method for analyzing substances contained in cultural assets, and it is a basic material that transmits terahertz waves sufficiently and has a known absorption or reflection spectrum. A sample is prepared by applying and curing at least one of the agent and surface protective agent, and the sample is irradiated with terahertz waves having substantially different wavelengths, and absorbed or reflected by transmission or reflection spectroscopy. Absorption of terahertz waves by various dyes, pigments, color developing agents, surface protection agents that can be used for cultural properties by obtaining spectra and obtaining absorption or reflection spectra in each sample by changing the substance applied to the base material By obtaining a reflection spectrum database, based on the obtained database, the terahertz wave is irradiated to the cultural property to be analyzed and its absorption characteristics are analyzed. And identifying the substance contained in cultural properties.

  Similarly, at least one of dyes, pigments, color formers, and surface protection agents that can be used for cultural properties is mixed and cured in a basic medium that sufficiently transmits terahertz waves and has a known absorption or reflection spectrum. The sample is prepared, and the sample is irradiated with terahertz waves having substantially different wavelengths, the absorption or reflection spectrum is obtained by transmission or reflection spectroscopy, and the substance mixed in the basic medium is changed. By obtaining absorption or reflection spectra, we obtain a database of absorption or reflection spectra of terahertz waves with various dyes, pigments, color extenders and surface protectants that can be used for cultural properties, and analyze based on the obtained database A substance contained in a cultural property may be identified by irradiating the target cultural property with terahertz waves and analyzing its absorption characteristics.

  Here, almost all surfaces of the cultural property to be analyzed are irradiated with terahertz waves almost continuously, and the result is output as an image showing the overall image of the cultural property, contributing to the understanding of the overall appearance. Also good.

  Similarly, it is possible to irradiate the entire surface of the cultural property to be analyzed with terahertz waves from multiple directions and output the result as an image showing the overall image of the cultural property, thereby contributing to the understanding of the overall appearance. Good.

  Alternatively, a terahertz wave may be used to identify a substance located at a predetermined depth from the surface of the cultural property to be analyzed, thereby contributing to detection of the internal structure.

  Each substance located at different depths from different surface positions of the cultural property to be analyzed is identified almost continuously, and the result is output as an image showing the cross section of the cultural property, contributing to the understanding of the internal structure Also good.

  On the other hand, when the terahertz wave is irradiated to the cultural property to be analyzed and the absorption characteristics thereof are analyzed, the spectrum of a plurality of types of substances may be separated and analyzed using principal component analysis to contribute to the convenience of analysis.

 According to the present invention, a terahertz wave absorption or reflection spectrum database by various dyes, pigments, color developing agents, and surface protecting agents that can be used for cultural properties is obtained, and is included in the cultural property to be analyzed based on the database. Can be identified. This provides useful information for art history research and restoration activities.

Embodiments of the present invention will be described below with reference to the drawings.
In spectroscopy using electromagnetic waves in the terahertz wave band (approximately 3-650 cm-1), absorption due to intermolecular interactions such as hydrogen bonds and van der Waals forces appears, so non-destructive organic materials such as proteins and sugars Suitable for analysis. Terahertz wave spectrometers, which were difficult to generate and detect in the past, have been developed in recent years. By using the spectroscopic method, dyes, pigments, color developers, surfaces that have characteristic absorption for terahertz waves It becomes possible to specify a protective agent and the like.

Spectroscopic technology cannot identify a substance without an absorption / reflection spectrum database indicating which frequency band terahertz wave is absorbed by. Previously, there was no spectral data in the terahertz wave band of various materials used for cultural properties, so we developed a means to obtain them.
That is, at least one of dyes, pigments, color formers and surface protective agents that can be used for cultural properties is applied to a basic material such as polyethylene that sufficiently transmits terahertz waves and has a known absorption or reflection spectrum. Harden to make a sample. The sample is irradiated with terahertz waves of substantially different wavelengths, and an absorption or reflection spectrum is obtained by transmission or reflection spectroscopy.
Absorption or reflection spectrum of terahertz waves by various dyes, pigments, color developing agents and surface protective agents that can be used for cultural properties by changing the number of substances applied to the base material and obtaining the absorption or reflection spectrum in each sample Get the database.

  Similarly, at least one of dyes, pigments, color developing agents, and surface protecting agents that can be used for cultural properties in a basic medium or solvent such as polyethylene that sufficiently transmits terahertz waves and has a known absorption or reflection spectrum. A sample may be prepared by mixing and curing.

Based on the obtained database, the terahertz wave is irradiated to the cultural property to be analyzed and its absorption characteristics are analyzed, so that the substances contained in the cultural property are identified.
Since terahertz waves are a safe non-ionizing and non-thermal electromagnetic wave frequency band, there is an advantage that safety of not only cultural assets but also analysis workers is ensured.

  Here, with the light source and detector in the terahertz wave band, the substantially entire surface of the cultural property to be analyzed may be irradiated substantially continuously. Then, it becomes possible to image the entire cultural property and output it as an image showing the overall image, which contributes to grasping the overall appearance.

  Similarly, a plurality of terahertz wave sources and detectors may be used as a camera to irradiate substantially the entire surface of the cultural property to be analyzed from a plurality of directions. Then, the entire cultural property can be imaged at a time, and it is output as an image showing the overall image, contributing to the understanding of the overall appearance.

Terahertz spectroscopy can analyze both transmission and reflection, and can be selectively used according to the thickness of the object and the depth of the analysis target position.
In particular, since low-frequency terahertz waves have moderate transparency, it is possible to obtain information in the depth direction in a non-destructive manner in combination with tomography technology. In other words, it is possible to grasp the internal structure by identifying each substance located at different depths from different surface positions of the cultural property to be analyzed and outputting the result as an image showing the cross section of the cultural property. Become. Similarly, a high-frequency terahertz wave with an increased output may be used.
As the tomography, a conventionally known CT technique based on a projection cutting theorem that obtains a cross-sectional image by calculation from measurement of projection amounts from a plurality of directions can be appropriately applied.

By applying a spectrum analysis technique such as principal component analysis to the analysis of the measured spectrum, it is possible to separate and analyze the spectra of a plurality of substances.
In addition to principal component analysis, this spectrum analysis includes statistical analysis of multivariate data consisting of multiple values such as factor analysis, cluster analysis, multiple regression analysis, discriminant analysis, conjoint analysis, and covariance structure analysis. The conventionally known multivariate analysis to be handled can be applied as appropriate.

Experimental example:
Absorption spectra of terahertz waves were determined for dyes, pigments, color extenders, and surface protection agents that can be used for cultural properties. Clear spectral data were obtained for more than 100 types of samples, but several examples are shown below, and examples of dyes, pigments, color developing agents, and surface protecting agents that can be used in the database are shown.
1 and 2 are graphs showing analysis examples of inorganic pigments and organic pigments.
Each of these was measured by mixing 5 types of inorganic pigments and 4 types of organic pigments in polyethylene powder that does not absorb terahertz waves. As shown in the figure, characteristic absorption was confirmed.

In general, a dye refers to a colored substance that is used to dye cloth or paper by being dissolved in a solvent such as water. On the other hand, what is used by being dispersed in some medium without being dissolved in a solvent is called a pigment.
Examples of the dye include natural dyes, synthetic dyes, and fluorescent dyes.

Natural dyes extracted from various animals and plants have been used as natural dyes since ancient times.
There are many types of plant-derived dyes, and Akane, Ai, Turmeric, Safflower, Murasaki, etc. have been known since ancient times.
Examples of animal origin include ancient purple obtained from mussels and cochineal obtained from Enjimushi.
Mineral-derived compounds are soluble inorganic compounds with coloring power, such as mud, potassium permanganate, and cobalt complex salts used to dye Oshima koji. Ocher, red, and petal may be mentioned, but these are insoluble in the solvent and may be classified as pigments.

  Synthetic dyes have been used since the 19th century, starting with the synthesis of purple mauve obtained by oxidizing aniline with potassium dichromate, and the synthesis of akane pigment alizarin and eye pigment indigo.

  Fluorescent dyes are dyes whose pigments are fluorescent substances, and have been industrially used from the modern day with the intention of whitening effect by fluorescence.

Pigments are roughly classified into two types according to their components: inorganic pigments and organic pigments.
Inorganic pigments include natural mineral pigments that have been used since prehistory and synthetic inorganic pigments that have been chemically synthesized. Ceramic pigments used for coloring ceramics are also included in inorganic pigments.

Natural mineral pigments have been mainly pulverized natural rocks and minerals as they are, except for the black color that uses firewood when burning oils and fats.
Black candy is now called carbon black and is used for a variety of purposes. Ink used in calligraphy once used oil smoke (lamp black), but nowadays, furnace black made by incomplete combustion of natural gas and oil is used.
In paints, plant black (peach black, vine black) made by burning plants and animal black (bone black) made by burning animal bones are also used. Ultramarine with lapis lazuli and patina with peacock stone were used for high-quality paintings and decorations. In red, a petal (iron oxide) and cinnabar (mercury sulfide) were used. Many industrially used materials are brown pigments derived from natural earth such as amber and senna, calcium carbonate (white or colorless), kaolin (clay: colorless), and the like.
Of these natural mineral pigments, colorless pigments are used to make pale colors and are also used as rake pigment materials. A special example is pearl pigments (pulverized with pearly luster) that are used by grinding white mica.

There are many types of synthetic inorganic pigments, including bitumen (Prussian blue, milory blue), since the 18th century. Inorganic pigments generally lack coloring power, transparency, and clarity compared to organic pigments, but have good light resistance and are frequently used in paints and the like.
Typical synthetic inorganic pigments include white zinc white, lead white, lithopone, titanium dioxide, red red lead, petal, yellow yellow chrome (chrome yellow), zinc yellow (zinc chromate, zinc yellow). ), Cadmium Yellow, Nickel Titanium Yellow, Strontium Chromate, Blue Ultramarine, Bitumen Blue, Cobalt Blue, Synthetic Ultramarine, Black Carbon Black, Green Viridian, Oxide of Chromium Precipitating barium sulfate, barite powder, lime carbonate powder, precipitated calcium carbonate, gypsum, clay (China Clay), silica powder, diatomaceous earth, talc, alumina white, basic magnesium carbonate, abrasive powder and the like.

Ceramic pigments are ceramic pigments that have been discovered and developed for the purpose of glaze coloring. It has significantly different characteristics from other inorganic pigments in that it has high heat resistance, weather resistance, and chemical resistance. There are a wide variety of other inorganic pigment materials such as oxides, carbonates, sulfates, sulfides, aluminum powder, and carbon, but ceramic pigments include oxides, composite oxides, and silicates.
Typical ceramic pigments include gray zircon gray, yellow praseodymium yellow, chrome titanium yellow, green chrome green, peacock, Victoria green, blue blue, turquoise blue, pink chrome tin pink, There is salmon pink.

Other anti-corrosive pigments used to prevent metal rust include red lead, cyanamide lead, lead suboxide, basic lead sulfate, calcium lead acid, zinc chromate, strontium chromate, and zinc white.
Examples of the metal powder pigment added to give a decorative effect and a protective effect include zinc powder, aluminum powder, pearl mica powder, brass powder, and scale-like iron oxide powder.

The organic pigment is a pigment mainly composed of an organic compound. In the past, dyes collected from plants and animals, such as indigo, cochineal lakes, and indigo lakes, were solidified by various methods, but today all are used industrially. It is a petrochemical synthetic pigment.
Organic pigments are largely classified into azo pigments and polycyclic pigments depending on their chemical structures, but they are sometimes classified into insoluble pigments and lake pigments depending on hue. The organic pigment has an unsaturated double bond, absorbs and stabilizes resonance energy from light, and is colored according to the specific absorption wavelength region.

Azo pigments are synthesized in water by the reaction of an aromatic amine and a coupling component. The hue changes from yellow to orange, red, and magenta, and its coloring power is generally stronger than that of inorganic pigments. Azo-based pigments have hydrogen bonds due to intramolecular polarization, and their strength strengthens the ability to bind crystals and improves fastness such as weather resistance.
Depending on the structure, monoazo pigments with one azo chromophoric group in the molecular structure, two azo chromophoric groups in the structure, symmetric disazo pigments centered on the center, and azo color development with an orientation structure at the center by condensation reaction They are classified into condensed azo pigments having two groups.

Polycyclic pigments have a history of insolubilizing dyes having a quinone structure to make pigments, and many pigments have higher fastness than azo pigments.
Typical polycyclic pigments include yellow quinophthalone, isoindoline, isoindolinone, orange diketopyrrolopyrrole, quinacridone, perinone, anthanthrone, red quinacridone, perylene, diketopyrrolopyrrole, Examples include purple dioxazine, blue phthalocyanine blue, indanthrene blue, and green phthalocyanine green.

FIG. 3 is a graph showing an example of analyzing the color developing agent.
Three kinds of color developing agents were mixed with polyethylene powder having no absorption of terahertz waves and measured. As shown in the figure, characteristic absorption was confirmed.
FIG. 4 is a graph showing an example of analyzing a color developing agent by infrared spectroscopy as a comparative experiment.
Three kinds of color developing agents were mixed with polyethylene powder having no absorption of terahertz waves and measured. In the case of infrared spectroscopy, as shown in the figure, it was confirmed that identification was not possible because it showed similar absorption characteristics.

  Among the components contained in the paint, the components other than the pigment are generally called a vehicle. When the medium is dried and solidified, the pigment particles are adhered to each other and fixed to the substrate surface. Although the color developing agent is also almost synonymous, it may be used specifically to indicate a component of the vehicle that remains without evaporating. A component that dissolves a color developing agent without chemical change and evaporates after being applied is called a solvent.

The media used in the paint are classified as follows according to the solidification mode.
Examples of physical drying that solidify as the solvent evaporates include Japanese glue, watercolor gum arabic, and mastic and damar resins used in oil. Examples of physicochemical drying that cause a chemical change when the solvent evaporates and become insoluble are tempera emulsions and acrylic resins for acrylic paints. Chemical drying that hardens only through chemical changes includes oil painting drying oils and alkyd resins. Examples of thermoplastics that are applied in a melted state by heat and that cool and solidify include waxes used in encaustics.

For the adhesive, a method using gelatin has been performed for a long time. Gelatin is extracted by applying heat to collagen, which is the main component of connective tissues such as animal skin, bones, and tendons, and contains protein as the main component.
Gelatin has been used as an adhesive for musical instruments such as violins that need to be adjusted and repaired, because it exhibits extremely strong adhesion to wood, but the bond loosens and peels off when exposed to steam. A low-purity material used as an adhesive for Japanese painting materials and crafts is called glue.

Casein has long been used as an eyepiece for paintings, as a medium, and as an adhesive.
Casein tempera has an emulsifying action and becomes water resistant after drying. It is hardly affected by temperature and is alkaline in liquid form, but becomes neutral when dried. Compared to glue tempera, it is slightly brittle but the color is vivid.

  A typical tempera technique in painting is egg tempera. When the paint is dry, it can be applied immediately, and after drying for a few days, it will not dissolve in water. The classic tempera painting technique is that the board is primed with Bologna plaster, but the tempera painting that has been mixed with eggs in the finish of oil has also come to be called tempera painting.

Varnishes or varnishes have also been used for a long time to protect the surface of materials such as wood.
By component, there are dry oils such as linseed oil, tung oil, walnut oil, natural resins such as kohaku, copal, and rosin, synthetic resins such as alkyd resin and polyurethane, solvents such as turpentine oil and stocked solvent.

Most natural varnishes consist of sap or resin dissolved in a solvent. Depending on the solvent used, alcoholic varnish, turpentine varnish, and oil varnish are classified.
The combination of walnut oil, linseed oil and amber, copal and rosin was most often used for varnishes for musical instruments such as violins. Spar varnish was used for articles that require waterproofness and weather resistance, such as sails.

 According to the present invention, it is possible to specify non-destructive substances such as pigments used in the production of cultural properties, so that it is possible to effectively perform art history research and restoration activities. In addition, since safe electromagnetic waves are used for the human body, the safety of not only cultural assets but also analysis workers is ensured, so the industrial utility value is high.

Absorption spectrum showing an analysis example of inorganic pigments Absorption spectrum showing organic pigment analysis example Absorption spectrum showing an example of analysis of color extender As a comparative example, an absorption spectrum showing an example of analyzing a color developing agent by infrared spectroscopy

Claims (7)

A method for analyzing substances contained in cultural properties,
Apply at least one of dyes, pigments, colorants, and surface protection agents that can be used for cultural properties to a basic material that has sufficient transmission of terahertz waves and has a known absorption or reflection spectrum, and cures the sample. make,
The sample is irradiated with terahertz waves having substantially different wavelengths, and an absorption or reflection spectrum is obtained by transmission or reflection spectroscopy.
By calculating the absorption or reflection spectrum of each sample by changing the substance applied to the base material, we have created a database of absorption or reflection spectra of terahertz waves by various dyes, pigments, color developers and surface protective agents that can be used for cultural properties. Get,
Based on the obtained database, Terahertz spectroscopy is characterized by identifying the substances contained in the cultural property by irradiating the target cultural property with terahertz waves and analyzing its absorption characteristics. Inspection method. A method for analyzing substances contained in cultural properties,
Samples are prepared by mixing and curing at least one of dyes, pigments, colorants and surface protective agents that can be used for cultural properties in a basic medium that is sufficiently transparent to terahertz waves and has a known absorption or reflection spectrum. make,
The sample is irradiated with terahertz waves having substantially different wavelengths, and an absorption or reflection spectrum is obtained by transmission or reflection spectroscopy.
By obtaining the absorption or reflection spectrum of each sample by changing the material mixed in the basic medium, we have created a database of absorption or reflection spectra of terahertz waves by various dyes, pigments, color developers, and surface protection agents that can be used for cultural properties. Get,
Based on the obtained database, Terahertz spectroscopy is characterized by identifying the substances contained in the cultural property by irradiating the target cultural property with terahertz waves and analyzing its absorption characteristics. Inspection method. Terahertz waves are irradiated almost continuously on almost the entire surface of the cultural property being analyzed,
The method for inspecting a cultural property by terahertz spectroscopy according to claim 1, wherein the result is output as an image indicating an overall image of the cultural property. Irradiate terahertz waves from multiple directions to almost the entire surface of the cultural property being analyzed,
The method for inspecting a cultural property by terahertz spectroscopy according to claim 1, wherein the result is output as an image indicating an overall image of the cultural property. The method for inspecting a cultural property by terahertz spectroscopy according to claim 1, wherein a substance located at a predetermined depth from the surface of the cultural property to be analyzed is identified using terahertz waves. Identify each substance located at different depths from different surface positions of the cultural asset to be analyzed,
6. The method for inspecting a cultural property by terahertz spectroscopy according to claim 5, wherein the result is output as an image showing a cross section of the cultural property. 7. Inspecting cultural properties by terahertz spectroscopy according to claim 1 to 6, wherein the spectrum of a plurality of kinds of substances is separated and analyzed using principal component analysis when the terahertz wave is irradiated to the cultural property to be analyzed and its absorption characteristics are analyzed. Method.

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