WO2010082625A1

WO2010082625A1 - Information pattern carrier and method for optically reading information pattern

Info

Publication number: WO2010082625A1
Application number: PCT/JP2010/050412
Authority: WO
Inventors: 中西　幹育
Original assignee: メトロ電気株式会社
Priority date: 2009-01-19
Filing date: 2010-01-15
Publication date: 2010-07-22
Also published as: CN102282568B; HK1162723A1; JP5339382B2; JPWO2010082625A1; CN102282568A

Abstract

Provided is an information pattern carrier, wherein an information pattern (12) is made invisible by forming a mask (13) on the information pattern formed by colored ink or making the color of the colored ink the same as the ground color of an information recording medium (11) or the color of a colored underprint portion. When the information recording medium (11) having the information pattern (12) is mounted on or carried into a predetermined position, excitation light (H1) having energy higher than that of the bandgap of semiconductor quantum dots is applied to the information pattern (12) from a light-emitting diode (15) to thereby thermally expand the semiconductor quantum dots. Light having a wavelength that is shifted to the long-wavelength side is emitted from the thermally expanded semiconductor quantum dots, the emitted light is received by a light sensor (16) having sensitivity to a portion on the long-wavelength side of the shifted wavelength, and the information pattern (12) is read by an information determining unit (17).

Description

Information pattern carrier and information pattern optical reading method

The present invention relates to an information recording medium on which an information pattern such as a barcode or a QR code is printed, an information pattern carrier such as a management target, and an optical reading method of the information pattern.

In recent years, information patterns such as barcodes or QR codes have been printed on various articles, various prepaid cards or pass-through cards, etc., and this information pattern is read using an optical reading device and used for management and authentication checks. Has been done. In this case, various security systems have been proposed in which an information pattern is subjected to anti-counterfeiting processing and is read by an optical reading system to determine whether the information pattern is forged.

Patent Document 1 prints an information pattern such as a barcode containing a phosphor, irradiates the information pattern with a semiconductor laser to excite the phosphor, receives light emitted from the phosphor, and optically transmits the information pattern. An optical reader that reads with a reader is disclosed. In this apparatus, when reading, since the wavelength peaks of the excitation light from the semiconductor laser diode and the fluorescence from the phosphor are separated from each other, only the emission spectrum of the phosphor can be read. In this security system, since it is difficult to forge the phosphor mark and the technology for reading the phosphor mark is difficult to forge, it is possible to provide relatively high security.

Patent Document 2 proposes an optical reading system using a light emitting diode, which can be made smaller and less expensive than an apparatus using a semiconductor laser diode. This optical reading system optically reads a printed layer printed with invisible ink, and the phosphor is made of an inorganic oxide to which neodymium is added as an activation element. In this phosphor, the light emission center wavelength of the light emitting element that excites the phosphor is separated from the wavelength region in which the light receiving element that receives the fluorescence from the printing layer can receive light. Therefore, even if a light emitting diode having a wavelength wider than that of a semiconductor laser diode is used for irradiation of excitation light, the excitation light and the light emission of the phosphor do not overlap, and the excitation light is read at the time of reading. This prevents erroneous determination. In this technique, since the information pattern is invisible, the presence of the information pattern is not noticed except at the time of reading, and high security can be provided.

In Patent Document 3, in an optical data carrier containing metal particles, an increase in the volume of the data carrier due to thermal expansion as a result of the absorption of radiation causes a shift of the absorbed light to a longer wavelength. It is disclosed.

JP 2001-52108 A Japanese Patent Laid-Open No. 6-274677 JP 2008-512807 A

In the optical reading device of Patent Document 1, since a semiconductor laser diode is used as a light source, the driving circuit of the light source becomes complicated and large, and the cost of the optical reading device increases.

Further, when the inventor of the present application tested the optical reading system disclosed in Patent Document 2, there were many cases where reading was impossible. This is because the light intensity of the light emitting diode is lower than that of the semiconductor laser diode, and sufficient excitation cannot be obtained, so the light emission of the phosphor is weak, and the light intensity of the light makes the light emission of the phosphor difficult to detect. It seems that it was inevitable to detect. Therefore, a means that can read the information pattern more clearly is desired.

Therefore, the inventor of the present application can adopt light from a light emitting diode as excitation light, can be miniaturized, can be an inexpensive optical reading system, has a strong light emission from a phosphor, and is a method different from Patent Document 1. The inventors have eagerly searched for a printing layer and an optical reading method that can receive light emitted from a printing layer (information pattern) excited by excitation light and can avoid receiving excitation light.

Further, the inventor of the present application pays attention to the shift of the wavelength to the longer wavelength side due to thermal expansion in Patent Document 3, and uses this for avoiding reception of excitation light at the time of reading, and is one step higher for the invisible information pattern. Accumulated thoughts to gain security.

The present invention has been devised in view of the above circumstances. The object of the present invention is to provide a barcode or QR formed on an information pattern carrier such as an information recording medium or a management object so that it cannot be recognized with the naked eye. It is extremely difficult to maliciously develop an optical reading device that can clearly read information patterns such as codes when reading, and can read the information of this information pattern even if it notices the existence of the information pattern, An object of the present invention is to provide an information pattern carrier and an information pattern optical reading method capable of realizing a high security system and realizing invisible traceability that provides high quality assurance.

An information pattern carrier of the present invention includes an information pattern formed of a colored ink containing core / shell type semiconductor quantum dots, and a mask which is formed on the information pattern to make the information pattern invisible. Yes. The information pattern is configured so that the semiconductor quantum dot emits light having a wavelength that has been thermally expanded and shifted to the longer wavelength side when irradiated with an excitation light having energy higher than the band gap of the semiconductor quantum dot. ing.

Furthermore, the information pattern carrier of the present invention is formed of a colored ink containing core / shell type semiconductor quantum dots, and is made the same color as the color of the ground color of the information recording medium or management object or the underlying colored layer. The information pattern is made invisible. The information pattern is configured so that the semiconductor quantum dot emits light having a wavelength that has been thermally expanded and shifted to the longer wavelength side when irradiated with an excitation light having energy higher than the band gap of the semiconductor quantum dot. ing.

An information pattern carrier such as an information recording medium or an object to be managed has an information pattern printed thereon with a colored ink and formed in an invisible state. With respect to this information pattern, the semiconductor quantum dots are excited by excitation light during reading to thermally expand, and light having a wavelength transitioning to the long wavelength side that is emitted at that time is received to decode the information. For this reason, since the information pattern is visible when the carrier is manufactured, it is easy to form the pattern. After the manufacturing, the information pattern is invisible, so that the presence of the information pattern is not noticed except during reading. When reading an information pattern, the core / shell type semiconductor quantum dot emits strong light, and the wavelength region of the light is greatly separated from the excitation light by the transition of the emission wavelength due to thermal expansion. Is clearly read. Further, since the emission wavelength is changed, it is difficult to imitate the reading device. The colored ink enhances the heat absorbability due to the irradiation of excitation light, and the temperature easily changes, so that the semiconductor quantum dots are easily expanded. It is difficult to easily imitate / manufacture colored ink, and security can be improved. Therefore, the information pattern can be reliably decoded by the optical reading device that can compensate for the handling in which the information pattern cannot be recognized with the naked eye and can decode the shifted wavelength.

The colored ink is preferably colored with any colorant of dyes, leuco dyes or pigments having a particle size of submicron. By using these colorants, coloring that absorbs visible light can be easily obtained without inhibiting the irradiation of the excitation light to the semiconductor quantum dots by adjusting the concentration.

It is preferable that the core / shell type semiconductor quantum dots have CdSe / ZnS as a core. Since it can disperse | distribute favorably with respect to colored ink and aggregation does not occur, it can be used as an ink and an information pattern can be printed well.

Core / shell type semiconductor quantum dots
(A) A core obtained by adding Te to ZnSe nanoparticles, and a shell of ZnS nanoparticles,
(B) (Zn (1-2 _x ) In _x Ag _x S) is used as a core or shell;
(C) Core ZnS nanoparticles containing Mn ions,
(D) using ZnS nanoparticles as a core,
(E) using Zn—In—Ag—S based semiconductor nanoparticles as a core;
(F) silicon nanoparticles as the core or shell,
It is also preferable that it is any one of these. By using these semiconductor quantum dots, strong light emission and wavelength transition due to thermal expansion of the semiconductor quantum dots can be suitably obtained.

Core / shell type semiconductor quantum dots
(G) Using silicon nanoparticles as a core and erbium as a shell,
(H) Erbium as a core and silicon nanoparticles as a shell,
It is also preferable that it is any one of these. Since erbium has a high coefficient of thermal expansion, the wavelength transition increases when the semiconductor quantum dot expands greatly when thermally expanded. Therefore, information can be read more clearly and security can be improved.

Also, the optical reading method of the present invention is made invisible by forming a colored ink containing core / shell type semiconductor quantum dots on an information recording medium or an object to be managed, and forming a mask thereon. An information pattern optical reading method, in which the semiconductor quantum dot is thermally expanded by irradiating the information pattern with an excitation light whose energy is higher than the band gap of the semiconductor quantum dot, and the long wavelength side from the thermally expanded semiconductor quantum dot The light having the wavelength shifted to is emitted, the emitted light is received by an optical sensor having sensitivity to the shifted long wavelength side portion, and the information pattern is read.

Another optical reading method of the present invention is formed with a colored ink containing core / shell type semiconductor quantum dots on an information recording medium or a management object, and is made the same color as the ground color or the color of the underlying colored layer. An optical reading method for an information pattern that is made invisible by irradiating the semiconductor quantum dot with an excitation beam having energy higher than the band gap of the semiconductor quantum dot to thermally expand the semiconductor quantum dot. Light having a wavelength shifted to the long wavelength side is emitted from the dot, and the emitted light is received by an optical sensor having sensitivity to the shifted long wavelength side portion, and the information pattern is read.

An information pattern printed on an information pattern carrier such as an information recording medium or an object to be managed is printed with colored ink, and is invisible. When reading, the semiconductor quantum dots are excited by excitation light to thermally expand, and light is emitted at that time. Receiving light of a wavelength that shifts to the long wavelength side, and decoding the information. In this way, at the time of reading, the core / shell type semiconductor quantum dot emits strong light, and the wavelength region of the light is greatly separated from the excitation light by the transition of the light emission wavelength due to thermal expansion, so that the excitation light is not read. Information is clearly read. Further, since the emission wavelength is changed, it is difficult to imitate the reading device. The colored ink enhances the heat absorbability due to the irradiation of excitation light, and the temperature easily changes, so that the semiconductor quantum dots are easily expanded. It is difficult to easily imitate / manufacture colored ink, and security can be improved. Therefore, the information pattern can be reliably decoded by the optical reading device that can compensate for the handling in which the information pattern cannot be recognized with the naked eye and can decode the shifted wavelength.

It is also preferable that the colored ink is colored with any one of a dye, a leuco dye, or a pigment having a particle size of submicron. By using these colorants, coloring that absorbs visible light can be easily obtained without inhibiting the irradiation of the excitation light to the semiconductor quantum dots by adjusting the concentration.

According to the information pattern carrier and the optical reading method of the present invention, the information pattern carrier such as the information recording medium or the management object is printed with the colored ink and is made invisible by the mask or the colored ink having the same color as the carrier. Regarding the information pattern, the semiconductor quantum dots are thermally expanded while being excited by excitation light at the time of reading, and light having a wavelength that shifts to the long wavelength side that is emitted at that time is received to decode the information. For this reason, since the information pattern is invisible after manufacture, the presence of the information pattern is not noticed except during reading. When reading, the core / shell type semiconductor quantum dot emits strong light, and the wavelength of the emitted light is shifted by thermal expansion, so the wavelength region is far away from the excitation light, so the information is clear without reading the excitation light. To be read. Further, since the emission wavelength is changed, it is difficult to imitate the reading device. The colored ink enhances the heat absorbability due to the irradiation of excitation light, and the temperature easily changes, so that the semiconductor quantum dots are easily expanded. It is difficult to easily imitate / manufacture colored ink, and security can be improved. Therefore, the information pattern can be reliably decoded by the optical reading device that can compensate the handling in which the information pattern cannot be recognized with the naked eye and can decode the shifted wavelength.

FIG. 1 is a schematic view of a reading apparatus for carrying out the optical reading method of the first embodiment. FIG. 2 is a graph showing the relationship between the wavelength and intensity of light emitted by exciting semiconductor quantum dots at room temperature. FIG. 3 is a graph showing the relationship between the wavelength and intensity of light emitted by expanding and exciting semiconductor quantum dots. FIG. 4 is a schematic view of a reading apparatus for carrying out the optical reading method of the second embodiment. FIG. 5 is a schematic view of a reading apparatus for carrying out the optical reading method of the third embodiment. FIG. 6 is a graph showing the relationship between the wavelength and intensity of light emitted by exciting the semiconductor quantum dots by heat shrinking according to the optical reading method of the third embodiment.

DESCRIPTION OF SYMBOLS 1,

1A reader

10A, 10B Information recording card 11

Information recording medium

11A, 11B Information pattern carrier 12 Information pattern 13 Mask 14 Underprint layer 15

Light emitting diode

16, 16A Optical sensor 17 Information determination part 2 Optical reading mechanism 3 Cooling means H1 Excitation light H2 Light emitted by excitation

Hereinafter, embodiments of an information pattern carrier and an optical reading method of the present invention will be described with reference to the drawings.

[First Embodiment]
FIG. 1 is a schematic diagram of a reading apparatus for carrying out the information pattern carrier and the optical reading method of the present embodiment. The reading device 1 is for reading information on the information recording card 10 </ b> A, and generally includes a light emitting diode 15 and an optical reading mechanism 2.

The information recording card 10A includes an information recording medium 11 and an information pattern carrier 11A on the information recording medium 11. The information pattern carrier 11A makes the information pattern 12 invisible by printing the information pattern 12 such as a visible barcode or QR code printed on the information pattern 12 after printing the information pattern 12. And a mask printing body 13 for the purpose. The information recording card 10A is in the form of a card on which information is recorded. For example, a cash card, various prepaid cards, a telephone card, a traffic card, a health insurance card, or the like is applied.

The information recording medium 11 is a main body of the information recording card 10A on which the information pattern 12 is printed. The information recording medium 11 is made of a vinyl chloride sheet or the like in which a white pigment such as titanium oxide is dispersed and held, and has a property of reflecting infrared rays, visible rays, and ultraviolet rays.

The information pattern 12 is formed by printing on the information recording medium 11 with colored ink containing core / shell type semiconductor quantum dots. In the present embodiment, the colored ink includes semiconductor quantum dots, a coloring material, and a binder for dispersing and holding them.

Semiconductor quantum dots are nanometer-sized semiconductor fine particles. The core / shell type refers to a type in which a core made of an inner material is covered with a shell made of an outer material. In this embodiment, a CdSe / ZnSe core / shell type semiconductor quantum dot is used.

The colorant is a material that absorbs visible light. The coloring material is a dye, a leuco pigment, or a pigment having a particle size of submicron, and includes a concentration that does not hinder the irradiation of the excitation light to the core / shell type semiconductor quantum dots. Suppose that By using these colorants and adjusting the concentration, it is possible to easily obtain a color that does not inhibit irradiation and a color that absorbs visible light.

When pigment is used as a colorant, coloring and durability are more durable than dyes and leuco dyes. However, when the particle size of the pigment exceeds 1 μm, the pigment exhibits its original light-shielding properties. Therefore, the light is blocked and irradiation to the semiconductor quantum dots contained in the ink is hindered. If the particle diameter of the pigment is submicron (less than 1 μm), preferably the particle diameter is in the range of 0.6 to 0.8 μm, it can retain translucency like a color filter, so that a colored ink other than black is used. In this case, it is particularly preferable to use an appropriate amount of pigment having a particle size in the range of 0.6 to 0.8 μm. In the present embodiment, the colored ink is black ink using carbon black as a coloring material.

The information pattern is made invisible by forming an opaque mask 13 on the information pattern 12. Here, invisible means that it is almost impossible to see with the eye or cannot be seen at all (including so-called invisible).

In this embodiment, the mask 13 is formed by mask printing in which the pattern is painted over the entire surface with the same color as the information pattern 12. The mask printing uses printing that does not absorb or block the excitation light H1 so as not to inhibit the excitation of the information pattern 12 by the excitation light H1. Specifically, the coloring material for printing that does not absorb the excitation light H1 includes a dye, a leuco dye, or a pigment having a submicron particle size. In particular, it is preferable to use carbon black as black ink and a density at which the information pattern 12 cannot be recognized. A masking film (not shown) is formed on the mask printing, and the ink forming the mask printing cannot be removed.

The information recording card 10A is configured to be able to scan and move relative to the light-emitting diode 15 and the optical sensor 16 in a straight line. In this embodiment, the scanning movement is performed by a mechanical mechanism (not shown) provided in the optical reading mechanism 2, but may be performed by a manual operation.

The light emitting diode 15 irradiates the core / shell type semiconductor quantum dots included in the information pattern 12 with the excitation light H1. The light emitting diode 15 is selected so that the excitation light H1 has higher energy than the band gap of the semiconductor quantum dots. In the present embodiment, the core / shell type semiconductor quantum dots included in the information pattern 12 are excited by the irradiation of the excitation light H1, and the thermal expansion of the semiconductor quantum dots also occurs.

The optical reading mechanism 2 includes an optical sensor 16 and an information determination unit 17.

The optical sensor 16 receives the light beam H2 emitted when the core / shell type semiconductor quantum dots included in the information pattern 12 are excited. The optical sensor 16 has a wavelength of a long wavelength side portion of light emitted by shifting to the long wavelength side in a state where the information pattern 12 including the core / shell type semiconductor quantum dots is thermally expanded, specifically, as shown in FIG. It is necessary to have sensitivity in the range Y on the long wavelength side. In the present embodiment, a photodiode is used for the optical sensor 16.

The optical sensor 16 is configured to receive light emitted from the information pattern 12 when the time required for the temperature rise of the information pattern 12 has elapsed. Specifically, the temperature before the information pattern 12 is heated and the temperature after the information pattern 12 are heated can be measured by, for example, a radiation temperature sensor directed to the information pattern 12, and the temperature before the information pattern 12 is heated (for example, 15 ° C. to 30 ° C.). ° C) to a temperature after heating (for example, 60 ° C to 85 ° C), and light reception is performed at this time.

The information determination unit 17 amplifies an electrical signal (rectangular signal) obtained by receiving light by the optical sensor 16 and forms an electrical code information signal corresponding to the code information of the information pattern 12.

In the optical reading method of this embodiment, when the information recording card 10A having the information pattern 12 made invisible by the mask printing 13 is placed or sent to a predetermined position by a mechanical mechanism, the light emitting diode 15 emits light, and the information The pattern 12 is irradiated with excitation light H1 having energy higher than the band gap of the semiconductor quantum dots. The excitation light H1 excites the semiconductor quantum dots and heats the information pattern 12 to thermally expand the semiconductor quantum dots.

Excited semiconductor quantum dots emit light whose wavelength has shifted due to thermal expansion. Specifically, when the CdSe / ZnSe core / shell type semiconductor quantum dots including those having different particle diameters are excited without being thermally expanded, as shown in FIG. A plurality of lights having different wavelengths are emitted every time. On the other hand, when excited in a thermally expanded state, as shown in FIG. 3, it emits light whose wavelength has greatly shifted to the long wavelength side. Even when the core particles of the core / shell type semiconductor quantum dots have a single particle diameter, the relationship in which the wavelength is largely shifted to the longer wavelength side by thermal expansion is the same. Since the semiconductor quantum dot is a core / shell type of CdSe / ZnSe, the obtained light emission is particularly strong.

The light emitted from the semiconductor quantum dots is received by the optical sensor 16 having sensitivity to the long wavelength side portion Y and converted into an electrical signal. The information determination unit 17 patterns this electrical signal and checks whether the information pattern 12 can be read, and further checks whether the code information of the information pattern 12 matches the data recorded in the database. The authenticity of the information pattern 12 is determined.

According to the present embodiment, the information pattern 12 can be excited by a normal inexpensive light emitting diode 15 and strong light can be emitted from the semiconductor quantum dots (quantum size effect). In addition, since semiconductor quantum dots are excited with thermal expansion and light emission is shifted to the long wavelength side, information patterns can be clearly detected without the excitation light and light emission overlapping, and ordinary inexpensive silicon photodiodes It is possible to detect with high sensitivity by a light receiving element such as.

The optical reading device 1 has a configuration in which the light emitted from the semiconductor quantum dots is shifted to the long wavelength side to emit light, and thus the optical sensor having sensitivity to the long wavelength side portion receives the emitted light and decodes the information. For this reason, it is difficult to imitate the optical reading device, and an optical reading method that provides high security or quality assurance can be realized. As a result, it is possible to prevent forgery, alteration, and tampering of credit cards, cash cards, telephone cards, ID cards, student ID cards, stamp cards, point cards, etc., and to reduce the size and space of the system. Invisible traceability can be realized.

An information pattern such as a barcode or QR code is formed in an invisible state on the information recording medium 11 so that the information pattern is not recognized with the naked eye. In addition, even if a malicious person or organization familiar with IT technology notices the presence of an information pattern from a minute bulge in the printed film on the surface of the information recording medium 11, the ink of this embodiment is imitated. Manufacturing is difficult. Furthermore, we analyzed that the light source of the information pattern is a core / shell type semiconductor quantum dot, and based on that we developed a reading device that can receive light emitted by normal excitation of the semiconductor quantum dot and decode the information However, since the wavelength of the emitted light is shifted to the longer wavelength side, the information pattern cannot be decoded by such a normal reading device.

In addition, when the information pattern 12 is printed on the information recording medium 11 with the colored ink, the information pattern 12 is visible, so that the printed pattern can be easily confirmed. At the time of reading, since the colored ink absorbs visible light, the temperature of the information pattern 12 is likely to increase due to the irradiation of excitation light, and the semiconductor quantum dots are likely to thermally expand. In particular, in the present embodiment, since a pigment is used, the heat absorption due to irradiation of excitation light is good. Since it is difficult to easily imitate and manufacture the composition of the colored ink, high security can be realized in this respect. In particular, in this embodiment, since the information pattern 12 is printed using ink colored with a pigment having a particle size of submicron, the information pattern 12 having high weather resistance and fading resistance can be obtained with respect to the color. Combined with the high chemical stability of shell-type semiconductor quantum dots, it is possible to realize a system that provides high quality assurance over a long period of time. Also, since CdSe / ZnS core / shell type semiconductor quantum dots are used for the colored ink, it can be dispersed well with toluene or the like and does not aggregate, and it can be used as an ink and can print information patterns well. .

As a modification of the present embodiment, the reading device may be provided with heating means for thermally expanding the semiconductor quantum dots. For example, an electric heater for applying high heat to the lower side of the information recording card 10 on which the information pattern 12 is printed as a heating means and thermally expanding the semiconductor quantum dots of the information pattern 12 may be provided. Good. Moreover, a means for irradiating the information pattern 12 with heat rays (infrared rays or the like) may be provided as a heating means. By these means, the semiconductor quantum dots 12 can be reliably heated and thermally expanded, and a light emission transition can be obtained more effectively.

In order to facilitate the thermal expansion of the semiconductor quantum dots by the excitation light, the excitation light H1 of the light emitting diode 15 may be condensed via the condenser lens and irradiated to the information pattern 12. As for the light emitting diode 15, one having a high output may be selected, a plurality of light emitting diodes may be used for irradiation, or a light emitting diode that emits infrared light and a light emitting diode that emits ultraviolet light may be used in combination.

Instead of the information recording medium 11, an information pattern of a management target object other than a card shape may be read. Examples of management objects include products other than cards and barcodes, QRs, etc. printed as information patterns 12, such as books with a spine on a book or a sticker printed with information patterns 12. There is.

[Second Embodiment]
FIG. 4 is a schematic view of a reading apparatus for carrying out the optical reading method of the second embodiment. The information recording card 10B of this embodiment includes an information pattern carrier 11B. The information pattern carrier 11B is printed on the information recording medium (or management target) 11 and the base on which the information recording medium 11 is printed but does not form an information pattern. A printing layer 14 and an information pattern 12 such as a barcode or QR code printed on the information recording medium 11 are provided. In addition, about the part which overlaps with 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

In the present embodiment, the information pattern 12 is made invisible by making the color of the information pattern 12 the same as the color of the ground colored printing layer 14 that is printed on the information recording medium 11 before the information pattern 12. is doing. Here, the color ink used for the information pattern 12 is the same color as that of the base print layer 14. That is, both the base printing layer 14 and the information pattern 12 use a carbon black pigment having a particle size of submicron.

According to the present embodiment, it is compensated that the information pattern 12 is handled in an invisible state except at the time of reading, and at the time of reading, since the colored ink absorbs visible light, the information pattern 12 is irradiated by excitation light. 12 easily rises in temperature, and the semiconductor quantum dots are likely to thermally expand, thereby enabling reading. Further, since it is difficult to easily imitate or manufacture the composition of the colored ink, high security can be realized also in this respect.

As a modification of this embodiment, the base print layer 14 is omitted, and the color of the information pattern 12 is set to the same color as the ground color of the surface on which the information recording medium 11 or the information pattern 12 of the management target is printed. 12 may be invisible. For example, the same coloring material as the pigment kneaded in the material of the information recording card 10B may be used for the colored ink of the information pattern 12, and the information pattern 12 may be directly printed on the information recording card 10B.

[Third Embodiment]
FIG. 5 is a schematic view of a reading apparatus for carrying out the optical reading method of the third embodiment. In the reading apparatus 1 </ b> A of the present embodiment, a cooling unit 3 that thermally contracts the semiconductor quantum dots by cooling the semiconductor quantum dots is provided. In addition, about the part which overlaps with 1st Embodiment, the same code | symbol is attached | subjected and description is abbreviate | omitted.

In this embodiment, the cooling means 3 cools the information pattern 12 and cools the semiconductor quantum dots. Here, the cooling means 3 is an electric cooler provided adjacent to or in contact with the surface of the information recording medium 11 on which the information pattern 12 is not printed, and can be cooled to a temperature of −10 to 0 ° C. is there.

As the optical sensor 16A provided in the optical reading mechanism 2A, a sensor having sensitivity in the wavelength region indicated by Ya shown in FIG. 6 which is a range deviated from the wavelength region shown in FIG. 2 to the short wavelength side is used.

In the present embodiment, when the information recording medium 10 having the information pattern 12 is placed or sent to a predetermined position, the cooling unit 3 cools the information pattern 12 and causes the semiconductor quantum dots to thermally contract. Then, the light emitting diode 15 emits light, and the information pattern 12 is irradiated with excitation light H1 having energy higher than the band gap of the semiconductor quantum dots. The semiconductor quantum dots subjected to heat shrinkage emit light having a wavelength that shifts to the short wavelength side shown in FIG. 6 as compared to the wavelength emitted from the semiconductor quantum dots when not thermally contracted (FIG. 2). This emitted light is received by the optical sensor 16A having sensitivity to the long wavelength side portion Ya, and an electric signal is generated. The information determination unit 17 patterns this electrical signal and checks whether the information pattern 12 can be read, and further checks whether the code information of the information pattern 12 matches the data recorded in the database. The authenticity of the information pattern 12 is determined.

According to the present embodiment, the core / shell type semiconductor quantum dot that is the light emission source of the information pattern 12 is excited so as to be accompanied by thermal contraction, and the light emission at that time is shifted to the short wavelength side. Since the optical sensor that has sensitivity to the part receives this emitted light and decodes the information, the information can be decoded for the first time by using a special optical reading device, which further enhances security or quality assurance. The system to give can be realized.

As a modification of the present embodiment, the cooling unit 3 may be a unit that blows low-temperature air or low-temperature gas as long as the information pattern 12 and the information recording card 11 are not damaged.

The present invention is not limited to the above-described embodiments, but includes variously modified forms within the technical scope without departing from the gist of the invention described in the claims. For example, in the above-described embodiments, CdSe / ZnSe core / shell type semiconductor quantum dots are used. However, even if security information is printed with visible ink containing the following core / shell type semiconductor quantum dots, good.

(A) a core / shell type semiconductor quantum dot having a core obtained by adding Te to ZnSe nanoparticles and a shell containing ZnS nanoparticles;
(B) a core / shell type semiconductor quantum dot in which the core / shell type semiconductor quantum dot has ZnS nanoparticles containing Mn ions as a core;
(C) ZnS nanoparticles doped with In ³⁺ and Ag ⁺ (Zn (1-2 _x ) In _x Ag _x S) by thermally decomposing a thiol complex containing Zn ²⁺ , In ³⁺ and Ag ⁺ Core / shell type semiconductor quantum dots,
(D) a core / shell type semiconductor quantum dot whose core is a ZnS nanoparticle containing Mn ions;
(E) A core / shell semiconductor quantum dot having Zn—In—Ag—S based semiconductor nanoparticles as a core, or (f) a core / shell semiconductor quantum dot having silicon nanoparticles as a core or shell.

In addition, the core / shell type semiconductor quantum dots contained in the visible ink are:
(G) a core / shell type semiconductor quantum dot having silicon nanoparticles as a core and erbium as a shell, or
(H) A core / shell type semiconductor quantum dot having erbium as a core and silicon nanoparticles as a shell may be used. The thermal expansion coefficient of erbium is 7.6 × 10 ⁻⁶ / ° C. at 20 ° C., which is about three times the thermal expansion coefficient of silicon, which is 2.5 × 10 ⁻⁶ / ° C. at 20 ° C. Therefore, it is most preferable to use erbium in order to realize wavelength shift due to expansion.

When silicon nanoparticles are used as the core and erbium nanoparticles are used as the shell, the silicon nanoparticles are preferably 1.9 nm to 4.3 nm, and the erbium nanoparticles are preferably 1.9 nm to 4.3 nm.

For semiconductor quantum dots having silicon nanoparticles as the core and erbium nanoparticles as the shell, the semiconductor quantum dots are dispersed in water and the water temperature is increased within a range of 22 ° C. to 90 ° C., and then excitation light having a wavelength of 325 nm is used. It has been confirmed that light emission with a wavelength of 720 to 740 nm can be obtained from semiconductor quantum dots.

When erbium nanoparticles are used as the core and silicon nanoparticles are used as the shell, the erbium nanoparticles should be 1.9 nm to 4.3 nm, and the silicon nanoparticles should be 1.9 nm to 4.3 nm. preferable.

For semiconductor quantum dots with erbium nanoparticles as the core and silicon nanoparticles as the shell, the semiconductor quantum dots are dispersed in water and the water temperature is increased in the range of 22 ° C. to 90 ° C., and then excitation at a wavelength of 325 nm is performed. It has been confirmed that strong light emission with a wavelength of 720 to 740 nm can be obtained from semiconductor quantum dots when irradiated with light.

Further, when silicon nanoparticles having oxygen doped on the surface, or silicon oxide nanoparticles whose inside is oxidized are used as a core or shell, and a core / shell type semiconductor quantum dot using erbium as a shell or core, This is preferable because it emits stronger light.

Furthermore, in the core / shell type semiconductor quantum dot having silicon nanoparticles as the core, a plurality of hydrocarbon groups are bonded to respective Si atoms in the silicon nanoparticles, and the surface of the Si atoms is covered with the hydrocarbon groups. A thing may be used. This semiconductor quantum dot can prevent a decrease in emission wavelength and emission efficiency, and can emit visible light by ultraviolet excitation. Further, preferably it is possible to adjust the particle size by the reaction conditions of the _Mg 2 Si and SiCl ₄ (silicon tetrachloride).

The present invention can be used not only for authenticating various cards, but also for reading traceable visual information for tracking product items. Note that the present invention does not exclude using a semiconductor laser diode as a light source of excitation light.

The present invention can prevent counterfeiting, falsification, and falsification of cards and certificates, and can reduce the size and space of the system, realize invisible traceability, and in fields where information retention is required. It can contribute widely.

Claims

An information pattern carrier comprising an information pattern formed of a colored ink containing a core / shell type semiconductor quantum dot, and a mask formed on the information pattern so as to be invisible. The information pattern emits light having a wavelength at which the semiconductor quantum dot thermally expands and shifts to a longer wavelength side when irradiated with an excitation light having energy higher than the band gap of the semiconductor quantum dot. An information pattern carrier configured as described above.
It is formed with colored ink containing core / shell type semiconductor quantum dots, and has an information pattern that is made invisible by making it the same color as the ground color of the information recording medium or management object or the color of the underlying colored layer When the information pattern is irradiated with an excitation light having an energy higher than the band gap of the semiconductor quantum dot, the semiconductor quantum dot thermally expands and shifts to a longer wavelength side. An information pattern carrier configured to emit light having a wavelength.
3. The information pattern carrier according to claim 1, wherein the colored ink is colored with any one of a dye, a leuco pigment, or a pigment having a particle diameter of submicron.
The information pattern carrier according to any one of claims 1 to 3, wherein the core / shell type semiconductor quantum dots have CdSe / ZnS as a core.
The core / shell type semiconductor quantum dots are:
(A) A core obtained by adding Te to ZnSe nanoparticles, and a shell of ZnS nanoparticles,
(B) (Zn (1-2 x ) In x Ag x S) is used as a core or shell,
(C) Core ZnS nanoparticles containing Mn ions,
(D) using ZnS nanoparticles as a core,
(E) using Zn—In—Ag—S based semiconductor nanoparticles as a core;
(F) silicon nanoparticles as the core or shell,
5. The information pattern carrier according to claim 1, wherein the information pattern carrier is any one of the above (a) to (f).
The core / shell type semiconductor quantum dots are:
(G) Using silicon nanoparticles as a core and erbium as a shell,
(H) Erbium as a core and silicon nanoparticles as a shell,
The information pattern carrier according to any one of claims 1 to 4, wherein the information pattern carrier is any one of (g) and (h).
An optical reading method of an information pattern formed by coloring ink containing core / shell type semiconductor quantum dots on an information recording medium or an object to be managed and made invisible by forming a mask on the ink, The information pattern is irradiated with an excitation beam having energy higher than the band gap of the semiconductor quantum dot to thermally expand the semiconductor quantum dot, and the transition from the thermally expanded semiconductor quantum dot to the wavelength shifted to the longer wavelength side is performed. An optical reading method, wherein light having a wavelength is emitted, the emitted light is received by an optical sensor having sensitivity to the transitioned long wavelength side portion, and the information pattern is read.
Optical of an information pattern formed by a colored ink containing core / shell type semiconductor quantum dots on an information recording medium or management object and made invisible by making it the same color as the background color or the color of the underlying colored layer In the reading method, the information pattern is irradiated with an excitation beam having energy higher than a band gap of the semiconductor quantum dot to thermally expand the semiconductor quantum dot, and from the thermally expanded semiconductor quantum dot to a longer wavelength side An optical reading method comprising: emitting light having a transitioned wavelength; receiving the emitted light by an optical sensor having sensitivity to the transitioned long wavelength side portion; and reading the information pattern.
9. The optical reading method according to claim 7, wherein the colored ink is colored with any one of a dye, a leuco dye, or a pigment having a particle diameter of submicron.
10. The optical reading method according to any one of claims 7 to 9, wherein the core / shell type semiconductor quantum dots have CdSe / ZnS as a core.
The core / shell type semiconductor quantum dots are:
(A) A core obtained by adding Te to ZnSe nanoparticles, and a shell of ZnS nanoparticles,
(B) (Zn (1-2 x ) In x Ag x S) is used as a core or shell;
(C) Core ZnS nanoparticles containing Mn ions,
(D) using ZnS nanoparticles as a core,
(E) using Zn—In—Ag—S based semiconductor nanoparticles as a core;
(F) silicon nanoparticles as the core or shell,
The optical reading method according to any one of claims 7 to 10, wherein any one of (a) to (f) above is provided.
The core / shell type semiconductor quantum dots are:
(G) Using silicon nanoparticles as a core and erbium as a shell,
(H) Erbium as a core and silicon nanoparticles as a shell,
The optical reading method according to any one of claims 7 to 10, wherein any one of (g) and (h) is provided.