JP6975441B2 - Marking method - Google Patents

Description

Embodiments of the present invention relate to methods and devices for forming markers inside solid materials, and articles in which markers are formed.

The act of recording information is used not only for the purpose of transmitting information but also as a means for identifying and proving an article (hereinafter referred to as marking). By applying the marking directly to the article itself, the marking formed by the marking (hereinafter, also referred to as a marker) and the article can be integrally inseparable. As a result, various information about the goods, such as the place of origin, the place of manufacture, the producer, the manufacturer, the history related to the transfer of ownership, and the characteristics and properties such as ingredients and purity can be given to the goods themselves. It is possible to easily track the goods and determine the authenticity. Typical marking methods include physical engraving on the article. This is done by physically processing a part of the article by irradiating it with a laser or cutting it. In this method, the physical structural change occurs in the article itself, which may spoil the aesthetic appearance of the article, but it is possible to form a visualized marker.

As an invisible marking method, a method of arbitrarily arranging atoms on the surface of an article using a scanning tunneling microscope or an atomic force microscope is known. As another method, Patent Document 1 discloses a method of applying nanoparticles having an active nitrogen vacancies center (hereinafter referred to as NV center) onto an article. The NV center has no absorption in the visible light region and cannot be observed with the naked eye, but it is excited by ultraviolet light and exhibits photoluminescence. Therefore, although this method is not a method of directly marking the article itself, it has a feature that marking can be performed without significantly impairing the aesthetic appearance of the article.

U.S. Patent Application Publication No. 2010/0062144

One of the objects of the embodiment of the present invention is a method and device for directly forming a marker that is invisible and two-dimensionally distributed inside the article on the article, and an article on which the marker is formed. Is to provide.

One of the embodiments of the present invention is a method for marking an article. This marking method includes directly forming a light emitting center layer distributed in a plane having a constant depth in the normal direction from the surface of the article on the article.

One embodiment of the present invention is a marked article comprising an insulator and a light emitting center layer distributed in a plane having a constant depth in the normal direction from the surface of the insulator.

One of the embodiments of the present invention is a marking device. The marking device has a radiation source configured to emit charged particles and a stage configured to move in two directions perpendicular to each other.

One of the embodiments of the present invention allows an invisible marker to be formed directly on an article and records information on the article to identify and prove the article without compromising the aesthetics or function of the article. Can be done. As a result, various information related to the article can be easily extracted and monitored, the identification of the article can be facilitated, and the traceability can be improved. Furthermore, it is possible to impart high confidentiality to the information contained in the marker and the existence of the marker itself.

A schematic perspective view of an article used in the marking method according to an embodiment of the present invention, and a schematic cross-sectional view showing the marking method. A schematic top view of a marker formed by the marking method according to an embodiment of the present invention, and a schematic cross-sectional view of a marked article. Schematic cross-sectional view of a marked article according to an embodiment of the present invention. The schematic diagram of the marking apparatus which is one Embodiment of this invention. The schematic diagram of the marking apparatus which is one Embodiment of this invention. An irradiation position adjusting mechanism of a marking device according to an embodiment of the present invention. An irradiation position adjusting mechanism for a marking device according to an embodiment of the present invention. The schematic diagram of the marking apparatus which is one Embodiment of this invention. A conceptual diagram and a configuration example of a marker reading device according to an embodiment of the present invention. Articles marked in Example 1 and markers detected. Articles marked in Example 3 and markers detected.

Hereinafter, embodiments of the invention disclosed in this application will be described with reference to the drawings. However, the present invention can be carried out in various forms without departing from the gist thereof, and is not construed as being limited to the description contents of the embodiments exemplified below.

The drawings may schematically represent the width, thickness, shape, etc. of each part as compared with the actual embodiment in order to clarify the explanation, but the drawings are merely examples and limit the interpretation of the present invention. It's not something to do. In the present specification and each figure, elements having the same functions as those described with respect to the above-mentioned figures may be designated by the same reference numerals and duplicate description may be omitted.

Other actions and effects different from those brought about by the following embodiments, which are obvious from the description of the present specification or which can be easily predicted by those skilled in the art, are naturally according to the present invention. It is understood that it will be brought about.

(Embodiment)
[1. Marking method]
In the marking method according to the embodiment of the present invention, the article is directly irradiated with charged particles (charged particle beams), and the reaction of the non-thermal equilibrium process generated by the direct irradiation is used to emit light having a form or defect inside the article different from the surroundings. Induces the central layer with a microscopic density.

FIG. 1A shows a schematic perspective view of the article 100 used for marking, and FIG. 1B shows a schematic cross-sectional view taken along the chain line AA'of FIG. 1A. In FIG. 1B, the surface of the article 100 and its vicinity are schematically shown.

Article 100 is a solid, and the region from the surface of the marking portion to 5 μm, the region from the surface to 10 μm, the region from the surface to 20 μm, the region from the surface to 50 μm, or the region from the surface to 100 μm is an insulator. It should be. Therefore, the inside of these regions (hereinafter referred to as the surface region) may be an insulator, a conductor, or a semiconductor. The surface region can have translucency in at least a part of the wavelength range from ultraviolet-visible light to infrared of 200 nm or more and 900 nm or less in order to read out the distribution of the emission center by fluorescence. The article 100 can be configured such that the transmittance of the surface region is, for example, 80% or more and 100% or less, 50% to 100% or less, or 20% to 100% or less.

The insulator may be an organic compound or an inorganic compound. Examples of the organic compound include polymer materials. The polymer material may be a natural polymer containing cellulose or a synthetic polymer. Examples of the inorganic compound include metal and semi-metal oxides, nitrides, carbides, halides, sulfides, sulfates, nitrates, carbonates and acetates. Typical examples of metalloid oxides are silicon oxide and phosphate glass containing the same, and examples of carbides include silicon carbide (SiC). As the halide, for example, calcium fluoride (fluorite), lithium fluoride, or the like can be selected. Minerals containing one or more of these inorganic compounds can also be used as an insulator. The insulator does not have to be a compound, and may be a simple substance such as diamond.

The shape of the article 100 is not limited, and may be plate-shaped, and the entire surface or a part of the surface may have a curved surface. FIG. 1A shows an article 100 having an octahedral shape as an example.

Charged particles include, for example ^{, lightly charged particles such as protons (H +} ), dehydrogen ions (D ⁺ ), helium ions (He ⁺ ), and helium nuclei (He ²⁺ ), or carbon ions (C ⁺ ) and neon. Heavy-charged particles such as ions (Ne ⁺ ) and argon ions (Ar ^{+) can be used.}

These charged particles can be supplied in various ways. For example, an accelerator is used as a radiation source to accelerate charged particles with an acceleration voltage of several hundred keV to 5 MeV, typically an acceleration voltage of 3 MeV. The obtained charged particle beam 102 (beam current) of several tens to several hundreds of μA is taken out by a beam kicker, and the taken out charged particle beam 102 is adjusted and converged by using a beam shifter, a microslit, a quadrupole electromagnet, etc., and micron. Convert to a beam. This microbeam is scanned and irradiated on the article 100 using a pair of electrodes (beam scanning electrodes) called an electrostatic scanner (see FIG. 1 (B)). As a result, the charged particle beam 102 can be scanned in two directions (for example, the X direction and the Y direction orthogonal to each other).

As will be described later, the scanning of the charged particle beam 102 moves the stage for holding the article 100 in two directions orthogonal to each other, or rotates around two axes orthogonal to each other (perpendicular to each other). You may go by doing.

A non-convergent charged particle beam 102 may be used as the charged particle beam 102. In this case, for example, instead of an accelerator, a radiation source in which a radioactive substance is sealed can be used, and a non-convergent charged particle beam 102 emitted from the radiation source can be used. When the non-convergent charged particle beam 102 is used, the charged particle beam 102 is not scanned, a paper or metal mask is placed between the article 100 and the radiation source, and the charged particle beam 102 is passed through the opening of the mask to the article 100. May be irradiated.

When the article 100 is irradiated with the charged particle beam 102 as shown in FIG. 1 (B), the charged particles proceed from the surface to the inside and lose their kinetic energy while being ionized. When the speed decreases due to the loss of kinetic energy, a large resistance is received in inverse proportion to the square of the speed, and when the speed decreases to a certain constant speed, the speed decreases sharply and stops. At this time, the generation of energy becomes maximum at the stop point. This maximum is called the Bragg peak. At the stop point, the high-density energy given by the charged particles induces defects inside the material of the article 100, and the emission center layer 104 is formed. On the other hand, in the region other than the stop point, the influence of the charged particle beam 102 on the material of the article 100 can be almost ignored. Therefore, the emission center layer 104 can be selectively formed at a certain depth inside the article 100.

The emission center layer 104 can be formed at a low density. Further, the light emitting center layer 104 is transparent to visible light, that is, has no absorption in the visible light region or has little absorption. Therefore, the light emitting center layer 104 cannot be detected with the naked eye, or is very difficult to detect. At the same time, the emission center layer 104 has a level that can be excited by an external stimulus such as light, and is excited by light irradiation to exhibit photoluminescence. For example, by absorbing the light energy of ultraviolet rays and visible light, light emission (fluorescence and / or phosphorescence) is given to the visible light region and the near infrared region. Therefore, for example, as shown in an enlarged view of the region 106 of FIG. 1 (FIG. 2 (A)) and a schematic cross-sectional view (FIG. 2 (B)) along the chain line BB', the charged particle beam 102 is an article. By irradiating the article 100 while scanning in the X and Y directions to form a two-dimensionally distributed emission center layer 104, invisible information can be recorded on the article 100, and external light irradiation is used. Information can be visualized and read by giving a stimulus. Therefore, various information can be secretly given to the article 100.

Due to the characteristics of the Bragg peak, the position of the Bragg peak, that is, the depth of the emission center layer 104 from the surface of the article 100 is determined by the range of charged particles. In other words, the depth can be controlled by the acceleration energy. For example, when the charged particle beam 102 is irradiated from the normal direction of the surface of the article 100, the depth d from the surface of the article 100 of the emission center layer 104 in the normal direction is determined by the penetration length determined by the energy of the charged particles. It can be controlled arbitrarily (see FIG. 2B). Therefore, the depth d can be made constant by fixing the acceleration energy. As a result, the light emitting center layer 104 two-dimensionally distributed in a plane having a constant depth in the normal direction from the surface of the article 100 can be directly formed on the article 100. In other words, a plurality of emission center layers 104 can be directly formed in a plane parallel to the surface of the article 100.

When the surface of the article 100 is a curved surface, the charged particle beam 102 may be irradiated from the normal direction of the surface. Also in this case, as shown in FIG. 3A, the surface on which the light emitting center layer 104 is formed is a curved surface, and the depth d can be made constant in the normal direction of the surface of the article 100.

FIG. 2A shows an example in which the matrix type two-dimensional code is recorded as information, but the recorded information is not limited. Therefore, the light emitting center layer 104 can form a shape that can be expressed in two dimensions, such as a one-dimensional barcode, an image, a symbol, a number, and a character, inside the article 100. In other words, the article 100 can contain a plurality of light emitting center layers 104 in a plane parallel to the surface at a constant depth from the surface in the normal direction of the surface of the article 100.

The thickness t of the emission center layer 104 (see FIG. 2B) is determined by the energy of the charged particles. Alternatively, the thickness t may be controlled by moving the stage holding the article 100 in parallel with the charged particle beam 102.

Marking may be performed so that a plurality of light emitting center layers 104 are formed in the plurality of laminated surfaces. For example, as shown in FIG. 3B, the first emission center layer 104_1 is placed in the plane at a depth d1 from the surface of the article 100 by utilizing the charged particle beam 102 first obtained by using high acceleration energy. Form. Next, a plurality of emission center layers 104 are formed by forming the second emission center layer 104_2 from the surface of the article 100 in the plane of the depth d2 by using the charged particle beam 102 obtained by using the low acceleration energy. Is formed. The formation order of the plurality of emission center layers 104 is not limited, and the first emission center layer 104_1 may be formed after the second emission center layer 104_2 is formed.

Alternatively, different charged particles may be used in the formation of the first emission center layer 104_1 and the second emission center layer 104_2. When the morphology and chemical structure of the emission center layer 104 differ depending on the acceleration energy and the type of charged particles, the absorption characteristics and emission characteristics of the first emission center layer 104_1 and the second emission center layer 104_1 change. Therefore, by changing the excitation wavelength at the time of reading or selecting the wavelength to be detected at the time of reading, it is possible to read a plurality of different information from the same region, and record higher density information on the article 100. Can be done.

As described above, the irradiation of the charged particle beam 102 causes a chemical structural change inside the article 100, which forms a light emitting center layer 104 having a morphology and defects different from those of the surroundings. When the charged particles are lightly charged particles such as protons and helium nuclei, the elemental composition of the emission center layer 104 is the same as or substantially the same as the elemental composition of the surrounding elements. Therefore, it is possible to provide the article 100 having the same or substantially the same chemical composition as the chemical composition of the light emitting center layer 104 and the region (intermediate region) between the light emitting center layer 104 and the surface of the article 100.

When a heavily charged particle is used as the charged particle, the charged particle can exist as an ion, an atom, or in a state of being bonded to a material in the article 100. In this case, an article 100 having a chemical composition of the light emitting center layer 104 different from that of the intermediate region can be obtained.

As described above, by applying the marking method of the present embodiment, information can be directly recorded for an article having an insulating surface. Therefore, it can be applied to various articles such as minerals, securities, banknotes, and ornaments. Since the light emitting center layer 104, which is a marker, has no absorption in the visible light region, or the defect density of the light emitting center layer 104 is so small that it cannot be visually recognized, the marker should be formed without impairing the shape and appearance of the article. Can be done. Further, by concealing the excitation wavelength of the emission center layer 104, it is possible to impart high concealment to the recording of information and its contents.

[2. Marking device]
An example of a marking device for realizing the marking method of one embodiment of the present invention will be described below. FIG. 4 shows a schematic diagram of the marking device 110 when an accelerator is used as a radiation source.

As the accelerator (not shown), a light ion microbeam generator, a heavy ion microbeam generator, or the like can be used. The accelerator may be a linear accelerator or a circular accelerator such as a cycloton.

Although not shown, the charged particle beam 102 generated by the accelerator may use a beam shifter, a microslit, a divergence limiting slit, or the like, and appropriately limit the beam diameter and divergence component, and adjust the beam energy. For example, the beam diameter of the charged particle beam 102 irradiated to the article 100 can be adjusted to be several μm and the beam current can be adjusted to be several pA. After that, the charged particle beam 102 is one-dimensionally converged by using the beam focusing magnet 112. FIG. 4 shows an example using two beam focusing magnets 112 composed of a quadrupole electromagnet.

The one-dimensionally focused charged particle beam 102 is scanned in two directions (X direction and Y direction in the figure) intersecting each other by using two sets of beam scanning electrodes 114_1 and 114_2 composed of a pair of electrodes. NS. Thereby, the irradiation position of the charged particle beam 102 can be controlled.

The article 100 is held and fixed on the stage 116. Although not shown, the article 100 can be appropriately fixed with a clamp or the like. When the article 100 has a plate shape, it may be fixed by a suction chuck or an electrostatic chuck. Further, the stage 116 may be provided with an X-axis moving mechanism 118 and a Y-axis moving mechanism 120, and a marking device 110 may be configured so as to be able to move in two directions (for example, the X direction and the Y direction) intersecting each other. By providing the moving mechanism on the stage 116, the article 100 can be moved in a wider range with respect to the charged particle beam 102, and a marker can be formed in a wide range.

As shown in FIG. 5, the X-axis rotation mechanism 122 and the Y-axis rotation mechanism 124 may be provided together with or in place of the X-axis movement mechanism 118 and the Y-axis movement mechanism 120. As a result, the stage 116 can be rotated around the X-axis and the Y-axis, and when marking the article 100 having a curved surface, the surface is irradiated with the charged particle beam 102 from a certain direction. be able to. Therefore, even for the article 100 having a curved surface, it is possible to form the light emitting center layer 104 in a plane having a certain depth in the normal direction from the surface.

Although not shown, a Z-axis moving mechanism for moving the stage 116 in the Z-axis direction or a mechanism for rotating the stage 116 about the Z-axis may be provided. Alternatively, a robot arm may be used instead of the moving mechanism described above.

The marking device 110 may be provided with a mechanism for precisely adjusting the position (that is, the marking position) at which the convergent charged particle beam 102 is irradiated on the article 100. For example, as shown in FIG. 6, the marking device 110 is provided with an aperture mirror 182 provided between the beam scanning electrode 114_2 and the stage 116 as an irradiation position adjusting mechanism 180, and an image pickup device 184 for observing the article 100 on the stage 116. Can be installed.

The aperture mirror 182 is a mirror having an opening 183 through which the charged particle beam 102 can pass, and is installed so that the axis of the opening 183 coincides with the beam axis of the charged particle beam 102. As a result, not only the article 100 can be observed from the same direction as the irradiation direction of the charged particle beam 102, but also the state and position of the article 100 can be confirmed even during the irradiation of the charged particle beam 102.

Observation of the stage 116 and the article 100 installed on the stage 116 is performed using an image reflected by the aperture mirror 182. This image can be observed and analyzed in detail via the image pickup apparatus 184. As the image pickup apparatus 184, a photodiode or an image sensor may be used. If necessary, a microscope 186 for magnifying the image may be provided between the aperture mirror 182 and the image pickup apparatus 184. As the microscope 186, a long working distance microscope or the like can be used.

Alternatively, as shown in FIG. 7, instead of the microscope 186, a Cassegrain lens 190 may be provided between the beam scanning electrode 114_2 and the stage 116 so that the optical axis of the Cassegrain lens 190 and the optical axis of the charged particle beam 102 coincide with each other. good. The irradiation position can be directly confirmed by reflecting the image magnified by the Cassegrain lens 190 by the aperture mirror 182 and introducing it into the microscope 192.

The element can be excited by the charged particle beam 102 to generate high-energy photons such as characteristic X-rays, and the marking position can be recorded and reproduced. For example, an X-ray detector (for example, a Si (Li) semiconductor type photodetector or a silicon drift type semiconductor X-ray detector) 194 is provided in the irradiation position adjusting mechanism 180 near the stage, and the height of characteristic X-rays from the article 100 is high. Detects energy photons. If necessary, an absorber 196 for removing charged particles scattered from the article may be provided between the stage 116 and the X-ray detector 194. The intensity of the X-ray obtained from the marking by the irradiation of the charged particle beam 102 is measured by the X-ray detector 194. At the same time, a fixed position on the stage 116, for example, a position where the optical axis of the charged particle beam 102 and the stage 116 intersect is recorded by using the control device 198 as coordinates. By using the obtained X-ray intensity distribution and coordinate data, and the relative position between the stage 116 and the article, the irradiation position on the article 100 can be grasped and recorded. In addition, it becomes easy to reproduce the marking on different articles 100.

When the radiation source 130 that emits the non-convergent charged particle beam 102 is used, the marker may be formed by using the mask 132 without scanning the charged particle beam 102. In this case, for example, as shown in FIG. 8, a mask holder 134 may be provided in the marking device so that the mask 132 can be arranged between the radiation source 130 and the stage 116. This allows the same marker to be formed on a large number of articles 100 using a single mask 132.

When irradiating heavy charged particles for marking, an ion implantation device such as an ion doping device or an ion implantation device may be used instead of the heavy ion microbeam generator which is an accelerator. In this case as well, since the charged particles give a non-convergent charged particle beam 102, the marker may be formed by using the mask 132.

[3. Reader]
An example of a reading device for reading markings from a marked article 100, which is one of the embodiments of the present invention, produced by using the marking method described above will be described below.

FIG. 9A shows the basic configuration of the reading device 140 according to the embodiment of the present invention. The reader 140 includes a light source 142 and a photodetector 144 of any configuration. The light source 142 is not limited, and may be a light source having high monochromaticity such as a laser, a lamp such as a mercury lamp, a deuterium lamp, or an arc lamp, or a light emitting element such as a semiconductor diode (LED). As the laser, a gas laser such as an excimer laser or an argon ion laser, a solid-state laser such as a YAG laser or a semiconductor laser, or a liquid laser such as a dye laser can be used. Photodetectors 144 include photodiodes such as avalanche photodiodes (APDs) and photodiodes (PDs) including bipolar transistors, photomultiplier tubes (PMTs), charge-coupled device (CCD) image sensors, and complementary metal oxides. Examples include image sensors such as semiconductor (CMOS) image sensors. If the size of the marker is small, or if the light emitted from the light emitting center layer 104, which is a marker, is weak, a microscopic optical system may be provided. If the size of the marker is sufficiently large or if sufficiently strong light emission can be observed from the light emission center layer 104, the marker may be read visually or by using an optical microscope without using the photodetector 144. ..

FIG. 9B shows a configuration example of the reader 150 including the microscopic optical system. The reader 150 includes a laser light source 152 as a light source for the excitation light. The laser emitted from the laser light source 152 is appropriately introduced into an ND (Neutral Density) filter 156 using a mirror 154, and the amount of light is adjusted. A plurality of ND filters 156 may be used. After that, the laser is introduced into a bandpass filter 158 such as a shortpass filter, and light unnecessary for excitation is removed. The laser is then introduced into the objective lens 164 via the half mirror 162. At that time, the optical path of the laser may be adjusted by appropriately using a single mode fiber (SM fiber) 160 or a mirror 154 according to the installation environment of the microscopic optical system. As the objective lens 164, for example, a lens having a numerical aperture of 1.35 and a diameter of about 60 mm can be used, and its focal point can be adjusted by mounting it on an actuator stage.

The light emitted from the objective lens 164 is absorbed by the marker of the article 100, and light emission is obtained from the light emitting center layer 104 in the marker. This light emission is focused by the objective lens 164 and then introduced into the plano-convex lens 166 via a half mirror to be further focused. The plano-convex lens 166 may be a cylindrical lens or a spherical lens. The focused light is passed through the pinhole 168 to remove light other than the light emitted from the light emitting center layer 104 (for example, scattered light or reflected light from the article 100), and then introduced into the plano-convex lens 170 to be one-dimensional. Converted to light.

The processed light is introduced into the bandpass filter 172. Since the emission from the emission center layer 104 has a longer wavelength than the excitation light, a long pass filter may be used here as the bandpass filter 172. The light focused and adjusted in this way is introduced into the photodetector 144 and the marker is read. If necessary, a plano-convex lens 174 may be installed between the photodetector 144 and the bandpass filter 172 to collect light. As the photodetector 144, the above-mentioned photodiode, photomultiplier tube, image sensor, or the like may be used.

Further, as an arbitrary configuration, the spectroscope 178 may be provided in the reader 150. In this case, a part of the light emission may be taken out by using a half mirror 176 and introduced into the spectroscope through SM fiber or the like. As a result, the spectrum of light emission can be obtained, and it is possible to accurately determine whether or not the light emission is from the light emission center layer 104.

The above-mentioned reading method mainly uses light in the visible light region, but when heavy ions are used as charged particles, reading may be performed using the elements of the charged particles existing in the marker. .. For example, using fluorescent X-ray analysis, the marker can be read by detecting fluorescent X-rays generated from the marker by X-ray irradiation. In this case, the reader can include an X-ray tube for generating X-rays and a Si (Li) semiconductor detector as a main configuration. Alternatively, the article 100 may be irradiated with an electron beam used in scanning electron microscope (SEM) observation, and the energy and wavelength of the characteristic X-ray generated from the marker may be measured and read. In this case, as the reading device, an energy dispersive X-ray analyzer (EDS) or an SEM equipped with an electron probe microanalyzer (EPMA) may be used. Ions may be used as the excitation energy instead of X-rays or electron beams. This method is called particle-induced X-ray analysis (PIXE analysis), and the energy of characteristic X-rays generated by irradiating a marker with high-speed ions is measured. In this case, the main configuration of the reader is an accelerator for accelerating ions, a beamline for adjusting an ion beam containing accelerated ions, and a PIXE detector for measuring the generated characteristic X-rays. And so on.

By applying the present embodiment as described above, various articles 100 can be directly marked, and the article 100 itself can function as an information recording medium. Therefore, duplication of the article 100 can be effectively prevented. Further, the emission center layer 104 introduced as a marker in the article 100 has an excitation wavelength that changes depending on the material of the article 100 and the marking method. Therefore, the excitation wavelength differs depending on the material of the article 100. Since the marker is virtually undetectable visually, the recorded information can only be read by understanding all of the marked areas, how the marker is excited, and how the recording is read (restored). .. Therefore, the information given to the article by this embodiment can be used as a confidential record.

(Example 1)
In this example, an example in which a diamond thin film is marked is shown. The diamond thin film was formed by a chemical vapor deposition (CVD) method, and its size was 2 mm × 2 mm and its thickness was 500 μm. This diamond thin film was irradiated while scanning a charged particle beam obtained by accelerating protons, and marking was performed. The beam diameter of the charged particle beam was about 1 μm, the typical beam current was 50 pA, and the total irradiation time was about 3000 s.

The information in the marked diamond thin film was read using the second harmonic (532 nm) of the YAG laser as the excitation light and using a photodiode as the photodetector. As shown in the figure on the left side of FIG. 10A, the marker could not be detected without irradiating the excitation light. On the other hand, as shown in the right figure of FIG. 10A, light emission was observed from the marker that absorbed the excitation light, and the recorded information (here, the two-dimensional code) could be confirmed. From the above, it was confirmed that the information can be recorded by marking, that the recorded information is invisible, and that the recorded information can be read by using the excitation light.

(Example 2)
In this embodiment, an example in which marking is performed on fluorite, which is a mineral material, is shown. As shown in the left figure of FIG. 10B, the fluorite used had a substantially octahedral shape, and the length of one piece was about 30 mm. One surface of this fluorite was irradiated while scanning a charged particle beam obtained by accelerating protons, and marking was performed. The beam diameter of the charged particle beam was about 1 μm, the typical beam current was 50 pA, and the total irradiation time was about 2000 s.

The information in the marked fluorite was read by using a UV lamp (wavelength 365 nm) as the excitation light and confirming the excitation light visually or by using an optical microscope. As shown in the left figure of FIG. 10B, the marker could not be observed without irradiating the excitation light. On the other hand, as shown in the right figure of FIG. 10B, light emission was observed from the marker that absorbed the excitation light, and the recorded information (here, the two-dimensional code) could be confirmed. From the above, it was confirmed that the information can be recorded by marking, that the recorded information is invisible, and that the recorded information can be read by using the excitation light.

(Example 3)
In this example, an example in which marking is performed on the phosphate glass is shown. As shown in FIG. 11 (A), the phosphate glass used had a substantially square shape, and the length of one piece was about 35 mm. Here, the numbers on the phosphate glass are stamped by physical processing. One surface of this phosphate glass was irradiated while scanning a charged particle beam obtained by accelerating protons, and marking was performed. The beam diameter of the charged particle beam was about 1 μm, the typical beam current was 50 pA, and the irradiation time was 20 s.

The information in the marked phosphate glass was read by using a UV lamp (wavelength 365 nm) as the excitation light and visually confirming the excitation light. As shown in FIG. 11A, it can be seen that markers other than the engraved numbers cannot be detected in the state where the UV lamp is not irradiated. On the other hand, as shown in FIG. 11 (B) and FIG. 11 (C) which is an enlarged view thereof, in the state of being irradiated with the excitation light, light emission is obtained from the marker that has absorbed the excitation light, and the recorded information ( Here, a figure formed by a plurality of dots) could be confirmed. From the above, it was confirmed that the information can be recorded by marking, that the recorded information is invisible, and that the recorded information can be read by using the excitation light.

100: Article, 102: Charged particle beam, 104: Light source center layer, 104_1: First light source center layer, 104_2: Second light source center layer, 106: Region, 110: Marking device, 112: Beam focusing magnet, 114 : Beam scanning electrode, 116: Stage, 118: X-axis movement mechanism, 120: Y-axis movement mechanism, 122: X-axis rotation mechanism, 124: Y-axis rotation mechanism, 130: Radiation source, 132: Mask, 134: Mask holder 140: Reader, 142: Light source, 144: Photodetector, 150: Reader, 152: Laser light source, 154: Mirror, 156: ND filter, 158: Band pass filter, 160: SM fiber, 162: Half mirror 164: Objective lens, 166: Plano-convex lens, 168: Pinhole, 170: Plano-convex lens, 172: Band pass filter, 174: Plano-convex lens, 176: Half mirror, 178: Microscope, 180: Irradiation position adjustment mechanism, 182 : Aperture mirror, 183: Aperture, 184: Imaging device, 186: Microscope, 190: Casegren lens, 192: Microscope, 194: X-ray detector, 196: Absorber, 198: Control device

Claims (8)

A marking method comprising directly forming a light emitting center layer distributed in a plane having a constant depth in the normal direction from the surface of the article by irradiating the article with charged particles. The marking method according to claim 1, wherein the light emitting center layer is formed so as to be distributed in a plurality in the plane. The marking method according to claim 1, wherein the charged particles are protons or nuclei of helium. The marking method according to claim 1, wherein the irradiation of the charged particles is performed while moving the stage on which the article is mounted in two directions perpendicular to each other. The marking method according to claim 1, wherein the irradiation of the charged particles is performed while rotating the stage on which the article is mounted about two axes perpendicular to each other. The marking method according to claim 1, wherein the depth is 5 μm or more and 100 μm or less. The marking method according to claim 1, wherein the light emitting center layer exhibits photoluminescence. The marking method according to claim 1, wherein the article contains an insulator.

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