Medium

Abstract

The medium (100) has: a substrate (1); an absorption portion (22) (near-infrared absorption layer (3)) which is provided on the substrate 1 by including near-infrared absorbing material; and a code shape (20) which is formed into a predetermined shape by utilizing the absorption portion (22) or by covering a portion of the absorption portion (22), and outputs code information (CI) in the form of reflected light of near-infrared light when near-infrared light is irradiated, wherein, in the near-infrared absorbing material, when the integral value of the transmittance of visible light from 400 nm to 750 nm is set as the first integral value X1, and the integral value of the transmittance of a width of 20 nm centered on the predetermined wavelength λ of near-infrared light is set as the second integral value X2, the ratio R = X2 / X1 of the first integral value X1 to the second integral value X2 is 0.09 or more.

Description

Technical Field

[0001] This invention relates to media. Background Technology

[0002] For the purpose of ensuring the security of documents and embedding additional data, the following techniques are known: printing text using infrared-absorbing materials, irradiating these printed materials with infrared light, and reading the text printed by the infrared-absorbing materials.

[0003] As such a technology, for example, there is an image forming apparatus that uses a printing toner (IR toner) that employs near-infrared light absorbing material to form a coded image on a recording medium for the purpose of preventing illegal copying (see, for example, Patent Document 1).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-117352 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] In recent years, concerns about security have been rising, leading to a demand for technologies that embed invisible information (text, code, etc.) into media across various fields. Particularly when using near-infrared absorbing materials to embed invisible information (text, code, etc.) into a medium, a technology capable of reliably identifying this information is needed.

[0009] The present invention was made in view of the above-mentioned situation, and its object is to provide a technique for stably identifying invisible information when using near-infrared absorbing materials to set invisible information in a medium.

[0010] Methods for solving problems

[0011] According to the present invention, a medium is provided comprising: a substrate; a near-infrared absorbing layer disposed thereon comprising a near-infrared absorbing material; and a code shape formed in a predetermined shape using the near-infrared absorbing layer or using a shielding layer covering a portion of the near-infrared absorbing layer, and outputting code information in the form of reflected light of the near-infrared irradiation. In the near-infrared absorbing material, when the integral value of the transmittance of visible light from 400 nm to 750 nm is set as the first integral value X1, and the integral value of the transmittance over a width of 20 nm centered on a predetermined wavelength λ of near-infrared light is set as the second integral value X2, the ratio R = X2 / X1 of the first integral value X1 to the second integral value X2 is 0.09 or more.

[0012] Invention Effects

[0013] According to the present invention, a technology is available that enables stable identification of information when invisible information is placed in a medium using a near-infrared absorbing material. Attached Figure Description

[0014] [ Figure 1 [ ] is a diagram illustrating the general operation of the first embodiment using a medium embedded with invisible information and a device for reading that information.

[0015] [ Figure 2A [This is a top view of the medium in the first embodiment.]

[0016] [ Figure 2B [This is a top view of the medium in the first embodiment.]

[0017] [ Figure 3A [This is a cross-sectional view of the medium in the first embodiment.]

[0018] [ Figure 3B [This is a cross-sectional view of the medium in the first embodiment.]

[0019] [ Figure 4A [This is a diagram illustrating the absorption and reflection of near-infrared light in the code shape of the first embodiment.]

[0020] [ Figure 4B [This is a diagram illustrating the absorption and reflection of near-infrared light in the code shape of the first embodiment.]

[0021] [ Figure 5 [Figure number] is used to illustrate the method for manufacturing the medium in the first embodiment.

[0022] [ Figure 6 [Figure number] is used to illustrate the method for manufacturing the medium in the first embodiment.

[0023] [ Figure 7A [This is a cross-sectional view of the medium in the second embodiment.]

[0024] [ Figure 7B [This is a cross-sectional view of the medium in the second embodiment.]

[0025] [ Figure 8 [This is a graph showing the transmission spectrum (T%) measured in Example 9 with a sampling interval of 1 nm in the wavelength range of 300 nm to 1,000 nm, and the transmission spectrum with a transmittance of 10% at 780 nm.]

[0026] [ Figure 9[This is a graph showing the transmission spectrum (T%) measured in Example 9 with a sampling interval of 1 nm in the wavelength range of 300 nm to 1,000 nm, and the transmission spectrum with a transmittance of 10% at 830 nm.]

[0027] [ Figure 10 [This is a graph showing the transmission spectrum (T%) measured in Example 9 with a sampling interval of 1 nm in the wavelength range of 300 nm to 1,000 nm, and the transmission spectrum with a transmittance of 10% at 850 nm.]

[0028] [ Figure 11 The graph illustrates the spectral distribution of transmittance as a function of particle size in the embodiments.

[0029] [ Figure 12 The graph shows the ratio R (=X2 / X1) for each particle size in the embodiment.

[0030] [ Figure 13 [A graph showing the test results of the near-infrared absorbing material's ability to improve weather resistance in the embodiments.] Detailed Implementation

[0031] There are no particular limitations on the composition of the medium of the present invention, but examples generally include: a medium formed by a substrate and a code shape containing a near-infrared absorbing material (first embodiment); and a medium having an intermediate layer between the surface of the substrate and a printed layer containing a near-infrared absorbing material (second embodiment).

[0032] [First Implementation]

[0033] Referring to the figures, the first embodiment will be described in summary by way of the reading operation of code information superimposed on a code shape provided with near-infrared absorbing material.

[0034] Figure 1 This diagram illustrates an example of how the reading device 90 reads the invisible code shape 20 printed on the medium 100 according to this embodiment.

[0035] Figure 2A and Figure 2B This is a top view of the medium 100. The lower left area of ​​the medium 100, which is rectangular in shape, is provided with code shape 20. Figure 2A (a) and Figure 2B (a) shows the state that is normally invisible. Figure 2A (b) and Figure 2B (b) schematically shows the state of being visible when illuminated by near-infrared light (represented by IR in the figure). That is, it shows the state read by the reading device 90 when illuminated by near-infrared light.

[0036] The medium 100 is, for example, a plate made of paper, glass, resin, etc., and has a code shape 20 printed on one side (here, surface 1a).

[0037] It should be noted that the reading device 90 is shown as a movable type, but it can also be a type that is fixed to a device, or it can be a type that is not a dedicated device, but a type that has IR reading function in a general terminal of a mobile terminal (tablet device, smartphone, etc.).

[0038] There are no particular restrictions on the near-infrared light used for irradiation. Assuming the use of a semiconductor laser for irradiation, and considering factors such as implementation cost and marketability, the wavelength of the near-infrared light is assumed to be, for example, 780nm, 830nm, and 850nm. That is, semiconductor lasers that output the above wavelengths (780nm, 830nm, and 850nm) are widely used as semiconductor lasers installed in the reading device 90, and are therefore preferred from the viewpoints of cost and technological stability.

[0039] First, refer to Figure 1 and Figure 2A A detailed summary of the reading action of the code information CI superimposed on the code shape 20 is provided.

[0040] Code shape 20 has a near-infrared absorption layer 3 (see reference) Figure 3A When observed under visible light without near-infrared light (hereinafter referred to as "normal time"), it is invisible. When near-infrared light is irradiated, the code information CI superimposed on the code shape 20 is revealed and identified.

[0041] The surface 1a of the medium 100 is printed only with the color of the state of the code shape 20 (i.e., the background color of the medium 100), for example, white. In other words, since the code shape 20 is formed by an invisible near-infrared absorption layer, even when the code shape 20 is formed, the background color originally present in the medium 100 is recognized as the color of the medium 100.

[0042] Regarding the irradiated near-infrared light, the near-infrared absorbing material is absorbed in the near-infrared absorbing layer region of the code shape 20, while reflection occurs in the regions where no near-infrared absorbing material is provided, resulting in reflected light. Figure 1 (In the middle, represented by RR) it returns to the reading device 90.

[0043] It should be noted that the reading device 90 identifies the light level of the portion irradiated by the near-infrared absorbing material as "LOW (hereinafter referred to as "black"), and the light level of the area irradiated elsewhere as "High (hereinafter referred to as "white"), and displays the identification result in the form of code information CI (such as a QR code) on the display unit 91 (the white / black is obtained by binarizing High / Low). That is, the image displayed as "black" and "white" becomes the code information CI, and by having the designated reading device 90 read the code shape 20, the code information CI superimposed on the code shape 20 is obtained.

[0044] Code information (CI) can represent barcodes, QR codes (e.g., QR codes (registered trademarks)), combinations of numbers, words, and marks, or product markings. It should be noted that the illustrations in this specification show examples of QR codes.

[0045] Furthermore, the construction of code shape 20 will be explained.

[0046] Figure 3A This is a cross-sectional view of medium 100. Figure 2A (a) X1-X1 sectional view. Figure 4A It is Figure 3A The diagram shown is an enlarged view of region A1.

[0047] The medium 100 has: a substrate 1; and a near-infrared absorbing layer 3 disposed on one surface (here, surface 1a) of the substrate 1 by printing technology. It should be noted that, for convenience, the near-infrared absorbing layer 3 is represented in the form of a diagram in which circles of the same diameter are stacked.

[0048] The substrate 1 can be any component that is a plate-shaped part, such as paper, glass, or resin, with at least one side being a printable flat surface.

[0049] As a printing technology (printing method), for example, as a type of printing, there are letterpress printing, offset printing, gravure printing, and screen printing. In addition, as a plateless printing on-demand printing method, for example, image forming apparatuses that are readily available on the market, such as laser printing, inkjet printing, and thermal transfer printing, can be selected according to the type of medium 100 to be printed.

[0050] It should be noted that, regarding the near-infrared absorption layer set by printing technology, it can be set on the substrate 1 to cover only the area where the code shape 20 is set, or it can be set to cover the entire area where the code shape 20 is set (hereafter, the former is referred to as "Implement 1-A" and the latter as "Implement 1-B" as needed).

[0051] A summary of the aforementioned code information CI reading action, as it is based on... Figure 2A , Figure 3A and Figure 4A The description in "Embodiment 1-A" is as follows: the near-infrared absorption layer 3 is configured to cover only the area where the code shape 20 is set. It should be noted that the printed layer 2 in "Embodiment 1-A" refers to the layer formed by the near-infrared absorption layer 3 provided on the surface 1a of the substrate 1.

[0052] Next, refer to Figure 2B , Figure 3B , Figure 4B The outline of the reading operation of the code information CI in the "first-B embodiment" which is set such that the near-infrared absorption layer 3 completely covers the area where the code shape 20 is set will be described.

[0053] When explaining the construction of code shape 20, Figure 3B This is a cross-sectional view of medium 100, and is Figure 2B (a) X1-X1 sectional view. Figure 4B It is Figure 3B The diagram shown is an enlarged view of region A1.

[0054] The medium 100 has: a substrate 1; and a printed layer 2 disposed on one side (here, surface 1a) of the substrate 1 by printing technology. The printed layer 2 has: a near-infrared absorbing layer 3 disposed on surface 1a of the substrate 1; and the aforementioned shielding layer 6 disposed on the near-infrared absorbing layer 3.

[0055] The near-infrared absorption layer 3 is transparent and is applied by printing to cover approximately 40% of the lower surface of the surface 1a of the substrate 1 when viewed from above. The area where the near-infrared absorption layer 3 is applied is not limited to the above-mentioned area; for example, it can be the entire surface 1a of the substrate 1, or it can be the lower right quarter of the surface 1a. In short, any area where the size of the code shape 20 can be appropriately set is acceptable.

[0056] When the near-infrared absorbing layer 3 is observed under visible light without near-infrared illumination (hereinafter, for convenience, referred to as "normal state"), it is invisible, and the color of the layer on which the near-infrared absorbing layer 3 is provided (i.e., the surface 1a of the substrate 1) is observed. When the near-infrared absorbing layer 3 is illuminated with near-infrared light, it absorbs near-infrared light, and therefore appears black.

[0057] The surface of the medium 100 is printed with only the color of the near-infrared absorbing layer 3 (i.e., the background color of the medium 100), for example, white. In other words, the near-infrared absorbing layer 3 is formed of a near-infrared absorbing material that is almost colorless, so even when the near-infrared absorbing layer 3 is formed, the background color (here, white) of the medium 100 is recognized as the color of the medium 100.

[0058] Next, the shielding layer 6 contains a material that reflects near-infrared light, for example, reflecting more than 80% of the irradiated near-infrared light. The near-infrared light irradiated from the reading device 90 is reflected by the reflective part 21 (code mask part 61 described later) and absorbed by the absorptive part 22.

[0059] The masking layer 6 has a code mask portion 61 and an outer frame mask portion 62. The code shape 20 is composed of a reflective portion 21 based on the code mask portion 61 and an absorbing portion 22 based on the near-infrared absorbing layer 3 not covered by the code mask portion 61.

[0060] The code mask section 61 forms a code shape 20, for example, a square area when viewed from above, and is provided as an assembly of multiple reflective sections 21 corresponding to the part (unit) of the code information CI that is identified as "white".

[0061] The outer frame mask 62 is a region that can clearly distinguish and identify the area of ​​the code mask 61 (i.e., the code shape 20) from the area outside it. It should be noted that if the code shape 20 has a defined "cutting unit" formed in it and the outer shape of the code shape 20 can be clearly distinguished, then the outer frame mask 62 is not needed.

[0062] The shielding layer 6 is formed, for example, from a printing material that is adjusted to the same color as the base color of the substrate 1. The printing material is selected according to the type of printing. The type of printing material is a material containing pigments, dyes, and binder resins, and may also contain other components as needed, but which does not have near-infrared absorbing materials and reflects near-infrared light with a specified reflectivity (e.g., 80% or more). Therefore, even if the shielding layer 6 is provided on the transparent near-infrared absorbing layer 3, the code shape 20 (code information CI) will not be recognized when observed under visible light (i.e., under normal conditions).

[0063] The near-infrared light irradiated by the reading device 90 is reflected by the shielding layer 6 (code mask part 61) in the area of ​​the code shape 20 and becomes reflected light (represented as "RR" in the figure), and is absorbed by the near-infrared absorbing material in the area where the shielding layer 6 is not formed.

[0064] As a reading method, the reading device 90 identifies the light level of the portion irradiated to the near-infrared absorbing material as "black" and the light level of the reflected light returned after irradiating the shielding layer 6 (code mask section 61) as "white", and displays the identification result (white / black) in the display section 91 in the form of code information CI (QR code, etc.).

[0065] Near-infrared absorption layer

[0066] The near-infrared absorbing layer 3, which is applied using printing technology, will be described. The printing material used to apply the code shape 20 to the substrate 1 in the on-demand printing technology can be selected depending on the type of printing. Types of printing materials include pigments, dyes, and binder resins, and may also contain other components as needed; any material shown below can be used.

[0067] For convenience, printing materials composed of pigments and dyes with near-infrared absorption function will be referred to as "near-infrared absorbing materials".

[0068] There are no particular restrictions on the use of adhesive resins; any previously known adhesive resins can be used.

[0069] Examples include styrene-based resins such as styrene, α-methylstyrene, chlorostyrene, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-maleic acid copolymer, styrene-acrylate copolymer, styrene-methacrylate copolymer, and styrene-acrylonitrile-acrylate copolymer; polyester resins; vinyl chloride resins; rosin-modified maleic acid resins; phenolic resins; epoxy resins; polyethylene resins; polypropylene resins; ionomer resins; polyurethane resins; silicone resins; ketone resins; xylene resins; petroleum-based resins; and hydrogenated petroleum-based resins. These can be used individually or in combination with two or more. Among these, styrene-based resins and polyester resins containing aromatic compounds as structural units are preferred, and polyester resins are more preferred.

[0070] Polyester resins are obtained through the polycondensation reaction of alcohols and acids, which is generally known.

[0071] Examples of alcohols include, for example, glycols such as polyethylene glycol, diethylene glycol, triethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-propanediol, neopentyl glycol, and 1,4-butanediol; etherified bisphenols such as 1,4-bis(hydroxymethyl)cyclohexane, bisphenol A, hydrogenated bisphenol A, polyoxyethyleneized bisphenol A, and polyoxypropyleneized bisphenol A; and binary alcohols obtained by substituting these alcohols with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms. Alcohol monomers, other binary alcohol monomers, sorbitol, 1,2,3,6-hexanetetrol, 1,4-dehydrated sorbitol, pentaerythritol, dipentaerythritol, tripentaerythritol, sucrose, 1,2,4-butanetriol, 1,2,5-pentanetriol, glycerol, 2-methylpropanetriol, 2-methyl-1,2,4-butanetriol, trimethylolethane, trimethylolpropane, 1,3,5-trihydroxymethylbenzene, and other high-alcohol monomers with three or more components. These can be used individually or in combination with two or more.

[0072] There are no particular restrictions on the type of acid; it can be selected appropriately according to the purpose, with carboxylic acids being the preferred choice.

[0073] Examples of carboxylic acids include, for example, monocarboxylic acids such as palmitic acid, stearic acid, and oleic acid; maleic acid, fumaric acid, nicotinic acid, citrate, terephthalic acid, cyclohexanedicarboxylic acid, succinic acid, adipic acid, sebacic acid, malonic acid; dicarboxylic acid monomers obtained by substituting them with saturated or unsaturated hydrocarbon groups having 3 to 22 carbon atoms; anhydrides of these acids; dimers of lower alkyl esters and linoleic acid; 1,2,4-benzenetricarboxylic acid, 1,2,5-benzenetricarboxylic acid, 2,5,7-naphthalenetricarboxylic acid, 1,2,4-naphthalenetricarboxylic acid, 1,2,4-butanetricarboxylic acid, 1,2,5-hexanetricarboxylic acid, 1,3-dicarboxy-2-methyl-2-methylenecarboxypropane, tetra(methylenecarboxy)methane, 1,2,7,8-octanetetracarboxylic acid, Empol trimeric acid, and anhydrides of these acids; and polycarboxylic acid monomers of three or more ternary or higher ... These can be used individually or in combination with two or more.

[0074] It should be noted that adhesive resins may also contain crystalline resins.

[0075] As a crystalline resin, any resin that is crystalline is acceptable and there are no particular limitations. It can be appropriately selected according to the purpose. Examples include polyester resin, polyurethane resin, polyurea resin, polyamide resin, polyether resin, vinyl resin, and modified crystalline resin. These can be used alone or in combination of two or more. Among these, polyester resin, polyurethane resin, polyurea resin, polyamide resin, and polyether resin are preferred. For moisture resistance and incompatibility with the amorphous resins described later, resins having at least one of a urethane backbone and a urea backbone are preferred.

[0076] Pigments and pigments with near-infrared absorption function can be either organic or inorganic materials, without any particular restrictions.

[0077] Furthermore, there are no particular restrictions as long as the integral value of the transmittance in the visible light range of 400nm to 750nm is set as the first integral value X1, and the integral value of the transmittance over a 20nm wide area centered on a specified wavelength λ of near-infrared light is set as the second integral value X2, and the ratio R = X2 / X1 of the aforementioned first integral value X1 to the aforementioned second integral value X2 satisfies 0.09 or higher. It should be noted that the integral values ​​X1 and X2 will be described later.

[0078] For example, as an inorganic material, glass can be made by adding transition metal ions to known glass network forming components with wavelengths in the visible light transmission region, such as phosphoric acid, silicon dioxide, and boric acid, or by using pigments formed from inorganic and / or organic compounds, or by crystallizing such glass through heat treatment.

[0079] These inorganic materials can reflect light well in the visible light region to obtain invisible images, but from the point of view of ease of printing, organic materials are preferred.

[0080] As organic materials, anthocyanin compounds, phthalocyanine compounds, naphthalene phthalocyanine compounds, anthraquinone compounds, dithiol nickel complexes, aluminum salt compounds, etc., can be used.

[0081] It should be noted that, in this specification, for example, the term "naphthalene phthalocyanine compounds" refers to the general term for metal naphthalene phthalocyanine compounds with substituents, metal-free naphthalene phthalocyanine compounds with substituents, metal naphthalene phthalocyanine compounds without substituents, and metal-free naphthalene phthalocyanine compounds without substituents.

[0082] These compounds exhibit excellent near-infrared absorption properties. Specifically, they possess maximum absorption characteristics (maximum absorption wavelength) in the absorption distribution range of 700 nm to 900 nm. More specifically, they are materials that satisfy the above-mentioned properties, capable of good absorption at wavelengths of near-infrared light emitted from semiconductor lasers (e.g., 780 nm, 830 nm, and 850 nm), and exhibit low absorption characteristics in the visible light region (e.g., 400 nm to 750 nm). Therefore, in the medium 100 printed using near-infrared absorbing materials composed of these compounds, the printed portion is not visually discernible.

[0083] In particular, phthalocyanine compounds and naphthalene phthalocyanine compounds have better performance in terms of near-infrared absorption.

[0084] Specifically, vanadium oxynaphthalene phthalocyanine compounds having one or more of the following as substituents: nitro, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted alkylamino, and copper naphthalene phthalocyanine compounds having one or more of the following as substituents are preferred. More specifically, vanadium oxynaphthalene phthalocyanine compounds having one or more of the following as substituents: nitro, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, or substituted or unsubstituted alkylamino, are particularly preferred.

[0085] Organic materials deteriorate in performance when exposed to the atmosphere, ultraviolet light, etc., but if the rate of deterioration is slow, they can function as a medium without special deterioration countermeasures. Therefore, from the viewpoint of weather resistance (durability), pigment compounds without substituents in phthalocyanine and naphthalene phthalocyanine compounds have good performance.

[0086] That is, the medium 100 containing near-infrared absorbing material and printed with code information CI can maintain its function.

[0087] The numerical range for the content of pigments and dyes with near-infrared absorption function varies depending on the characteristics of the pigments and dyes with near-infrared absorption function. However, regardless of the type of pigment, if the content is insufficient, the absorption of near-infrared light will be insufficient.

[0088] As a component other than pigments and colorants that have near-infrared absorption function, any component commonly found in printing inks (including toners) is acceptable without particular restrictions. It can be selected appropriately according to the purpose. Examples include mold release agents, charge control agents, and additives.

[0089] Furthermore, the thickness T1 of the near-infrared absorption layer 3 will be explained.

[0090] First, refer to Figure 3A and Figure 4A The thickness T1 of the near-infrared absorption layer 3 in the "first embodiment" will be described in detail.

[0091] The thickness T1 is not particularly limited, but the lower limit is, for example, 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.5 μm or more. In addition, the upper limit is, for example, 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less.

[0092] By increasing the thickness T1, the absorption (absorption rate) of near-infrared light can be increased. On the other hand, if the thickness T1 is increased, a portion of the near-infrared light or reflected light irradiating the reflective portion 21 will enter its interior from the side of the near-infrared absorption layer 3. If a large amount of near-infrared light and reflected light enters the interior, the light level of the reflected light reaching the reading device 90 will decrease. That is, the contrast will decrease.

[0093] Therefore, by keeping the thickness T1 within the range described above, the balance between the amount of light absorbed by the absorbing part 22 and the amount of light reflected by the reflecting part 21 and reaching the reading device 90 can be optimized.

[0094] That is, the reading device 90 can obtain the code information CI with high contrast. As a result, when the desired amount of information is superimposed on the code information CI, the area of ​​the code shape 20 can be reduced, achieving very high concealment. Furthermore, even with the same area, more information can be superimposed on the code information CI.

[0095] Furthermore, if the thickness T1 is increased, the presence of the code shape 20 may be easily identified even under normal conditions when not exposed to near-infrared light due to the unevenness of the code shape 20. Therefore, by keeping it within the aforementioned range, the presence of the code shape 20 may not be easily identified under normal conditions.

[0096] Furthermore, when only the code shape 20 is printed, since the medium 100 has a background color (e.g., white) and no additional images are attached, the code shape 20 is rarely noticed. However, in cases where other images are printed on the code shape 20 (see the description of the manufacturing method described later),... Figure 5 Under the image layer 5 of (c), due to the large unevenness, the printing is different from the expected state, thus making it easy to identify the presence of the code shape 20.

[0097] However, by keeping the thickness T1 within the aforementioned range, sufficiently high print quality can be achieved even when other printing is performed on the medium 100 on which the code shape 20 is formed. That is, the presence of the code shape 20 will not be noticeable.

[0098] The longitudinal surface roughness Ra of the near-infrared absorption layer 3 is 0.5 μm or less, preferably 0.4 μm or less, and more preferably 0.3 μm or less. There is no particular limitation on the lower limit; however, if a generally achievable range is assumed, it is 0.05 μm or more.

[0099] By making the surface roughness Ra below 0.5 μm, the recognition accuracy of code information (CI) can be made highly stable.

[0100] Furthermore, the transverse surface roughness RSm is 0.5 μm or less, preferably 0.4 μm or less, and more preferably 0.3 μm or less. There is no particular limitation on the lower limit; however, if a generally achievable range is assumed, it is 0.05 μm or more.

[0101] By making the surface roughness RSm below 0.5μm, the recognition accuracy of code information CI can be made highly stable.

[0102] By analogy: In particular, by making the surface roughness RSm less than 0.4 μm, the near-infrared light does not reflect off the incident surface (i.e., the surface 3a of the near-infrared absorption layer 3) but enters the interior of the near-infrared absorption layer 3 and is absorbed by the near-infrared absorbing material, regardless of the incident angle of the near-infrared light.

[0103] Additionally, an image layer 5 is formed on the near-infrared absorption layer 3 by printing or the like (see...). Figure 5 In case (c), high printing quality can be achieved. In other words, even when the image layer 5 is provided on the code shape 20, the printing quality of the image layer 5 can be good, so the existence of the code shape 20 and the shape itself cannot be inferred from the unevenness of the image layer 5, thus achieving high security.

[0104] Next, refer to Figure 3B and Figure 4B The thickness T1 of the near-infrared absorption layer 3 in the "Embodiment 1-B" will be described in detail.

[0105] The thickness T1 is not particularly limited, but the lower limit is, for example, 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.5 μm or more. The upper limit is, for example, 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less.

[0106] By increasing the thickness T1, the absorption (absorption rate) of near-infrared IR can be increased. That is, the level (low level) of reflected light (RR) identified as "black" by the reading device 90 can be lowered. It should be noted that in this embodiment, since the near-infrared absorption layer 3 is coated all over the surface 1a of the substrate 1, a thinner layer is preferable from a cost perspective. Therefore, by keeping the thickness T1 of the near-infrared absorption layer 3 within the aforementioned range, a balance between achieving the desired black level (low level) and cost can be obtained.

[0107] It should be noted that the longitudinal surface roughness Ra and the transverse surface roughness RSm of the near-infrared absorption layer 3 are the same as those described in the aforementioned "Implementment 1-A", and the preferred range is also the same.

[0108] Regarding the thickness T2 of the shielding layer 6 disposed on the near-infrared absorption layer 3, the lower limit is, for example, 0.1 μm or more, preferably 0.3 μm or more, and more preferably 0.5 μm or more. The upper limit is, for example, 20 μm or less, preferably 15 μm or less, and more preferably 10 μm or less.

[0109] By increasing the thickness T2, the unevenness is increased, thereby achieving high contrast. On the other hand, from the viewpoint of minimizing the unevenness caused by the masking layer 6 and preventing recognition under normal circumstances, it is preferable to reduce the thickness T2. Therefore, by keeping the thickness T2 within the aforementioned range, high contrast can be achieved, and recognition under normal circumstances can be avoided. That is, when the desired amount of information is superimposed on the code information CI realized by the code shape 20 (code mask portion 61), the area of ​​the code shape 20 can be reduced, and very high concealment can be achieved. Furthermore, even with the same area, more information can be superimposed on the code information CI.

[0110] Furthermore, when only the code shape 20 is printed, since the medium 100 has a base color (e.g., white) and no additional images are attached, the code shape 20 is rarely noticed. However, when other images are printed on the code shape 20, if the relief is large, the printing will differ from the desired result, making the presence of the code shape 20 easily identifiable. Therefore, by keeping the thickness T2 within the aforementioned range, sufficiently high print quality can be achieved even when other printing is performed on the medium 100 on which the code shape 20 is formed. That is, the presence of the code shape 20 will not be noticeable.

[0111] Furthermore, when the masking layer 6 is provided on the near-infrared absorption layer 3, the masking layer 6, especially the code mask portion 61, can be printed with high quality. In other words, when the masking layer 6 is provided by printing, the desired printing quality can be obtained by making the surface 3a of the near-infrared absorption layer 3 on which the masking layer 6 is provided appropriately flat.

[0112] The longitudinal surface roughness Ra of the shielding layer 6 is 0.5 μm or less, preferably 0.4 μm or less, and more preferably 0.3 μm or less. There is no particular limitation on the lower limit; however, if a generally achievable range is assumed, it is 0.05 μm or more.

[0113] By making the surface roughness Ra below 0.5 μm, the recognition accuracy of code information (CI) can be made highly stable.

[0114] Furthermore, the lateral surface roughness RSm of the shielding layer 6 is 0.5 μm or less, preferably 0.4 μm or less, and more preferably 0.3 μm or less. There is no particular limitation on the lower limit; if a generally achievable range is assumed, it is 0.05 μm or more.

[0115] By reducing the surface roughness RSm to below 0.5 μm, the recognition accuracy of the code information CI can be made highly stable. In particular, by reducing the surface roughness RSm to below 0.5 μm, diffuse reflection and reflection in inappropriate directions in the reflected light can be suppressed, and the reflected light can be reliably returned to the reading device 90. That is, high-contrast code information CI can be obtained.

[0116] Furthermore, when other images are provided on the surface 6a of the masking layer 6, the desired print quality can be obtained for those images. That is, when other images are provided on the surface 6a of the masking layer 6, it is possible to prevent the code shape 20 from being recognized under normal circumstances due to print quality issues.

[0117] <Transmittance of near-infrared absorbing materials>

[0118] Regarding the aforementioned "near-infrared absorbing materials," the explanation will focus on transmittance.

[0119] The near-infrared absorbing material preferably satisfies the following relationships shown in equations (1) to (2).

[0120] [Formula 1]

[0121]

[0122]

[0123] In near-infrared absorbing materials, the integral value of the transmittance of visible light from 400 nm to 750 nm is set as the first integral value X1 (Equation (1)).

[0124] As a method for calculating the integral value X1, for example, it is calculated by measuring the transmission spectrum (T%) of the near-infrared absorbing material at sampling intervals of 1 nm in the wavelength range of 300 nm to 1,000 nm, and accumulating the values ​​of 100-transmission spectrum (%) for every 1 nm in the visible light range of 400 nm to 750 nm.

[0125] Here, the integral value X1 represents the color perception in the visible light region. Therefore, if this value is small, the color perception (coloring) becomes smaller. As a result, an invisible near-infrared absorption layer 3 is formed. Thus, even when the code shape 20 is formed, the original background color of the medium 100 is recognized as the color of the medium 100. It should be noted that the value of the integral value X1 is preferably 17,000 or less.

[0126] Let the wavelength of near-infrared light be λ, and let the integral value of the transmittance over a 20nm wide (i.e. ±10nm) centered on λ be the second integral value X2 (Equation (2)).

[0127] The method for calculating the integral value X2 is the same as that for calculating the integral value X1. For example, it is calculated by measuring the transmission spectrum (T%) of the near-infrared absorbing material at sampling intervals of 1 nm in the wavelength range of 300 nm to 1,000 nm, and accumulating the values ​​of 100-transmission spectrum (%) at wavelengths at 20 nm intervals (λ±10 nm) centered on λ.

[0128] It should be noted that the reason for using an integral value with a width of 20 nm centered at λ is as follows.

[0129] That is, the reason is that the spectral distribution and intensity of near-infrared light typically fluctuate. For example, depending on the reading device 90, the intensity of the irradiated near-infrared light may vary, or the reading sensitivity of the reflected light may differ.

[0130] The ratio R = X2 / X1 of the first integral value X1 to the second integral value X2 is 0.09 or higher. The lower limit of the ratio R is preferably 0.1 or higher, more preferably 0.11 or higher. There is no particular limitation on the upper limit of the ratio R, as long as it is a value calculated based on the preferred range of the integral value X1 of 17,000 or lower. By ensuring that the ratio R (=X2 / X1) is within such a range, the reading device 90 cannot recognize the code information CI when not illuminated by near-infrared light, but can recognize the code information CI only after illuminating near-infrared light.

[0131] However, as mentioned earlier, the wavelengths λ used for near-infrared light are frequently chosen as 780nm, 830nm, and 850nm. Therefore, for any of these three wavelengths λ, it is preferable to satisfy the aforementioned ratio R (=X2 / X1). By ensuring that all three wavelengths λ satisfy the aforementioned ratio R (=X2 / X1), more versatile code information (CI) can be achieved.

[0132] Particle size D of near-infrared absorbing material 50 The particle size is 0.05 μm to 1.0 μm. Preferably, the particle size D... 50 The particle size is 0.1 μm or more and 0.5 μm or less, preferably, the particle size D 50 It is between 0.2μm and 0.4μm.

[0133] Particle size D 50 If the value is too small, it is easy to agglomerate, the dispersibility will be reduced, and the quality of the near-infrared absorption layer 3 may also be reduced. Therefore, it is preferable to meet the above-mentioned lower limit value.

[0134] Particle size D 50 As the particle size increases, there is a tendency for a decrease in near-infrared absorption. For example, the spectral distribution of absorptivity (and corresponding transmittance) becomes broad. Therefore, by increasing the particle size D... 50Within the aforementioned range, high-contrast code information (CI) can be achieved.

[0135] In addition, by making the particle size D 50 Within the aforementioned range, the surface roughness Ra and RSm of the near-infrared absorption layer 3 can be reduced, thereby improving print quality and achieving higher contrast. Furthermore, when the image layer 5 is applied to the code shape 20 via printing or similar means, since the code shape 20 is within an appropriate range of surface roughness, the print quality can be achieved.

[0136] When the near-infrared absorbing material is a pigment, the crystallite size obtained from the crystallite diameter distribution is sometimes used as an indicator of the dispersion state. X-ray diffraction data analysis is also used as a method to estimate the crystallite size.

[0137] Generally, a microcrystal refers to a region within a grain that is considered a single crystal. Therefore, it can also be said that a grain is a polycrystalline aggregate of multiple microcrystals. Thus, the size of a microcrystal is considered to be smaller than or approximately equal to the grain size.

[0138] Therefore, if the lower limit of 0.05 μm in terms of particle size of the present invention is applied to the crystallite size, it naturally includes particles smaller than 0.05 μm. For convenience, the present invention will be described based on the particle size measurement results.

[0139] <Methods for Manufacturing Media>

[0140] First, regarding the method for manufacturing the medium 100 in "Embodiment 1-A", refer to... Figure 2A and Figure 5 A detailed explanation will be provided.

[0141] like Figure 5 As shown in (a), first, a flat substrate 1 with unprinted code shape 20, etc., is prepared.

[0142] Next, as Figure 5 As shown in (b), the absorbent portion 22 of the desired shape (code information CI) is disposed on a predetermined area of ​​the surface 1a of the substrate 1 by printing. Thus, a Figure 2A The medium 100 with code shape 20 is shown in (a).

[0143] Furthermore, such as Figure 5 As shown in (c), an image layer 5 can be set on a medium 100 with code shape 20 in a manner that covers code shape 20.

[0144] Regarding the image layer 5, it can be set by printing or by attaching a sealing component on which the image is set. It should be noted that the image layer 5 is formed of a material with high near-infrared transmittance, and 80% or more, more preferably 90% or more, more preferably 95% or more of the irradiated near-infrared light is transmitted to the absorption section 22.

[0145] Next, refer to Figure 2B and Figure 6 The manufacturing method of the medium 100 in "Embodiment 1-B" will be described in detail.

[0146] It should be noted that, Figure 6 In, with Figure 2B Similarly, in order to easily identify the transparent near-infrared absorbing layer 3, it is shown in a state of being observed by irradiating it with near-infrared light.

[0147] like Figure 6 As shown in (a), a flat substrate 1 with nothing set on surface 1a is first prepared.

[0148] Next, as Figure 6 As shown in (b), in the specified area of ​​surface 1a of substrate 1, here is a top view ( Figure 6 In the top view of (b), the specified area on the lower side (approximately 40% of the area in this case) is covered by a near-infrared absorbing layer 3 by printing. In this state, as... Figure 6 As shown in (b), when observed under near-infrared light, approximately 40% of the area on the underside of substrate 1 is identified as “black”.

[0149] Furthermore, such as Figure 6 As shown in (c), a masking layer 6 is formed on the desired area of ​​the surface 3a of the near-infrared absorbing layer 3 by printing. The code mask portion 61 and the outer frame mask portion 62 of the masking layer 6 are formed at the same time. Thus, a code shape 20 is formed through the code mask portion 61. That is, a medium 100 with a code shape 20 having code information CI superimposed is obtained.

[0150] It should be noted that, as mentioned above, the near-infrared absorption layer 3 is transparent under visible light. Therefore, if the surface 1a of the substrate 1 and the shielding layer 6 are "white", then under normal conditions when not irradiated with near-infrared light, the entire surface of the substrate 1 will be identified as white.

[0151] [Second Implementation]

[0152] Reference Figure 7A and Figure 7B The second embodiment will be described. The difference from the first embodiment is that a white layer 4 is provided as an intermediate layer between the surface 1a of the substrate 1 and the aforementioned printed layer 2.

[0153] First, refer to Figure 7A (Cross-sectional view of medium 100) The case in which the near-infrared absorbing layer 2 provided by printing technology covers only the area where the code shape 20 is provided on the substrate 1 (hereinafter, the former will be referred to as "Embodiment 2-A" as needed) will be described.

[0154] When the substrate 1 is, for example, a transparent resin sheet such as polyethylene terephthalate (PET) resin (i.e., a high transmittance), the irradiated near-infrared light is not sufficiently reflected by the reflective portion 21, which is not provided with the absorption portion 22, but is transmitted.

[0155] In this case, to improve reflectivity, for example, a white layer 4 (e.g., a layer formed by printing) is provided on the surface 1a of the substrate 1, and a code shape 20 (absorption portion 22) is provided thereon. This allows for stable reading of the code information CI in the reading device 90. At this time, the reflectivity of near-infrared light in the intermediate layer (here, the white layer 4) can be set to, for example, 70% or more, preferably 80% or more, and more preferably 90% or more.

[0156] Next, refer to Figure 7B (Cross-sectional view of medium 100) The near-infrared absorbing layer 3 provided by printing technology is provided in the case where the area of ​​the code shape 20 is completely covered on the substrate 1 (hereinafter, the former will be referred to as "Embodiment 2-B" as needed).

[0157] When the substrate 1 is a transparent resin sheet such as polyethylene terephthalate (PET) resin (i.e., with high transmittance) or when the color of its surface 1a is not constant, it is difficult to adjust the color of the surface 1a of the substrate 1 and the color of the masking layer 6, resulting in the masking layer 6 being easily identifiable under normal circumstances.

[0158] Furthermore, there is a situation where the surface roughness of the substrate 1a is unsuitable for directly depositing the near-infrared absorbing material layer 3. Considering this, a white layer 4 is placed between the near-infrared absorbing material layer 3 and the substrate 1 as an intermediate layer. It should be noted that, in this case, the shielding layer 6 is white.

[0159] [Features and effects of the implementation]

[0160] The embodiments of the invention have been described above with reference to the accompanying drawings. The features and effects of these embodiments can be summarized as follows.

[0161] (1) The medium 100 of this embodiment has: an absorption portion 22 (near-infrared absorption layer 3) which is provided on a substrate 1 by including a near-infrared absorbing material; and a code shape 20 which is formed into a predetermined shape by utilizing the absorption portion 22 or by covering a portion of the absorption portion 22, and outputs code information CI in the form of reflected light of the near-infrared light when near-infrared light is irradiated. In the near-infrared absorbing material, when the integral value of the transmittance of visible light from 400 nm to 750 nm is set as the first integral value X1 and the integral value of the transmittance of a width of 20 nm centered on the predetermined wavelength λ of near-infrared light is set as the second integral value X2, the ratio R = X2 / X1 of the first integral value X1 to the second integral value X2 is 0.09 or more.

[0162] By ensuring that the ratio R (=X2 / X1) is within such a range, the reading device 90 cannot recognize the code information CI when not illuminated by near-infrared light, but can recognize the code information CI when illuminated by near-infrared light. That is, the security of the code information CI can be ensured.

[0163] (2) The aforementioned absorption section 22 (near-infrared absorption layer 3) can be provided to completely cover the area where the aforementioned code shape 20 is set on the aforementioned substrate 1. However, if this is done, it will not be recognized as a black rectangular shape when read by the reading device 90. Therefore, by providing a shielding layer 6 in the area that is recognized as "white" on the absorption section, the near-infrared light will not reach the absorption section, but will be reflected by the shielding layer 6 provided on the absorption section.

[0164] As a result, the reading device 90 is able to identify the code information CI superimposed on the code shape 20 in "white" and "black".

[0165] (3) Regarding the integral value X1, when its value is small, the color of the near-infrared absorption layer also decreases, and the background color of the medium is recognized. Therefore, values ​​below 17,000 are preferred.

[0166] (4) The integral value X2 is calculated under the condition that the wavelength λ is at least one of 780nm, 830nm and 850nm.

[0167] As for the semiconductor laser installed in the reading device 90, semiconductor lasers that output the above wavelengths (780nm, 830nm and 850nm) are widely used, and are therefore preferred from the viewpoint of cost and technological stability.

[0168] (5) Near-infrared absorbing materials preferably use organic materials formed by pigments and dyes. From the point of view of durability, naphthalene phthalocyanine compounds have good performance.

[0169] (6) The aforementioned naphthylphthalocyanine compounds may preferably be vanadium-oxynaphthalocyanine compounds that may have substituents.

[0170] (7) Particle size D of near-infrared absorbing material 50 The range is from 0.1μm to 1.0μm.

[0171] Particle size D of near-infrared absorbing material 50 As the particle size increases, there is a tendency for a decrease in near-infrared absorption. For example, the spectral distribution of absorptivity (and corresponding transmittance) becomes broad, making it impossible to achieve high-contrast code information (CI). Therefore, it is preferable to have a particle size D... 50 Within the aforementioned range.

[0172] The embodiments of the present invention have been described above, but these are examples of the present invention, and various configurations other than those described above may also be used.

[0173] Example

[0174] Next, the invention will be described in detail based on an example of near-infrared absorbing materials.

[0175] Near-infrared absorbing materials

[0176] In the embodiments and comparative examples, the near-infrared absorbing materials used are as described below.

[0177] [Compound 1] Except that 0.9 g of copper chloride (I) was used in place of 1.6 g of vanadium trichlorooxide (V) in Synthesis Example 3 of Japanese Patent Application Publication No. 2017-226820, the procedure was the same as in Synthesis Example 3 to obtain 0.323 g of copper-1-phenyl-2,3-naphthalenephthalocyanine (I).

[0178] [Compound 2] The compound described in Example 8 of Japanese Patent Application Publication No. 2001-64255

[0179] [Compound 3] The compound described in Example 11 of Japanese Patent Application Publication No. 10-88017

[0180] [Compound 4] The compound described in the synthesis example of Japanese Patent Application Publication No. 10-45785

[0181] [Compound 5] Except that 21.9 g of 1,4-bis(2,2,3,3-tetrafluoropropoxy)-2,3-dicyanonaphthalene was used instead of 16.1 g of 1,4-dibutoxy-2,3-dicyanonaphthalene in Example 12 of Japanese Patent Application Publication No. 08-508269, the same procedure was followed as in Example 12 to obtain 0.323 g of copper-octa(2,2,3,3-tetrafluoropropoxy)naphthalenephthalocyanine (λmax: 842 nm; ε: 140000 (in toluene)) (I).

[0182] [Compound 6] The compound described in Synthesis Example 3 of Japanese Patent Application Publication No. 2017-226820

[0183] [Compound 7] The compound described in Synthesis Example 1 of Japanese Patent Application Publication No. 2017-226820

[0184] [Compound 8] Except that 25 g of 1-n-butoxy-2,3-dicyanonaphthalene was used instead of 25 g of 6-n-butoxy-2,3-dicyanonaphthalene in Example 1 of Japanese Patent Application Publication No. 61-215663, the procedure was the same as in Example 1 to obtain 0.323 g of vanadium-tetrabutoxynaphthalene phthalocyanine (λmax: 844 nm; ε: 202000 (in toluene)) (I).

[0185] [Compound 9] The compound described in Example 12 of Japanese Patent Application Publication No. 08-508269

[0186] [Compound 10] Except that 17.5 g of 1,4-diisopentyloxy-2,3-dicyanonaphthalene was used instead of 16.1 g of 1,4-dibutoxy-2,3-dicyanonaphthalene in Example 12 of Japanese Patent Application Publication No. 08-508269, the procedure was the same as in Example 12 to obtain 0.323 g of copper-octaisopentyloxynaphthalene phthalocyanine (λmax: 850 nm; ε: 150000 (in toluene)) (I).

[0187] [Compound 11] Except that 16.1 g of 1,4-diisobutoxy-2,3-dicyanonaphthalene was used instead of 16.1 g of 1,4-dibutoxy-2,3-dicyanonaphthalene in Example 12 of Japanese Patent Application Publication No. 08-508269, the procedure was the same as in Example 12 to obtain 0.323 g of copper-octaisobutoxynaphthalene phthalocyanine (λmax: 857 nm; ε: 167000 (in toluene)) (I).

[0188] [Compound 12] The compound described in Example 1 of Japanese Patent Application Publication No. 11-152413

[0189] [Compound 13] Except for the absence of 0.323 g of copper chloride (I) in Example 1 of Japanese Patent Application Publication No. 11-152413, 0.323 g of octaisobutoxy-nitrometal-free naphthylphthalocyanine (λmax: 873 nm; ε: 186000 (in toluene)) (I) was obtained by operating in the same manner as in Example 1.

[0190] [Compound 14] The compound described in Example 6 of Japanese Patent Application Publication No. 11-269399

[0191] [Compound 15] The compound described in Example 13 of Japanese Patent Application Publication No. 08-60008

[0192] [Compound 16] Except that 252 g of 4,5-bis(4-tert-butylphenylthio)-3,6-bis(2-ethoxyethoxy)phthalonitrile was used instead of 240 g of the phthalonitrile derivative in Example 45 of Japanese Patent Application Publication No. 07-56019, the same procedure was followed as in Example 45 to obtain 0.323 g of copper-octa(4-tert-butylphenylthio)-octa(2-ethoxyethoxy)phthalocyanine (λmax: 777 nm; ε: 93700 (in toluene))(I).

[0193] <Evaluation Methods>

[0194] [Integral value of transmittance]

[0195] Regarding compounds 1-13 (Examples 1-13) and compounds 14-16 (Comparative Examples 1-3), the integral value (X1) of the transmittance of visible light from 400nm to 750nm was calculated using the above formula (1) when the transmittance at wavelengths of 780nm, 830nm, and 850nm was 10%, and the integral value (X2) of the transmittance over a 20nm width (i.e., ±10nm) centered on wavelengths of 780nm, 830nm, and 850nm (which are near-infrared wavelengths) was calculated using the above formula (2). The results of the calculated integral values ​​(X1) are shown in Table 1.

[0196] In addition, the ratio R (=X2 / X1) of the integral value (X1) to the integral value (X2) for each wavelength of 780nm, 830nm and 850nm is also shown in Table 1.

[0197] It should be noted that the specific calculation steps are illustrated in Example 9 below.

[0198] [Table 1]

[0199]

[0200] (Example 9)

[0201] The calculation steps for the integral value of transmittance are specifically explained using compound 9 (Example 9) as an example. The transmittance spectrum (T%) of compound 9 was measured at 1 nm sampling intervals within the wavelength range of 300 nm to 1,000 nm. The transmittance spectrum at 780 nm, representing 10%, is shown below. Figure 8 . Figure 8 And as will be discussed later Figure 9 , 10 The oblique plane indicates the range of integral value X1, and the point plane indicates the range of integral value X2.

[0202] The integral value (X1) calculated using the transmission spectrum (T%) of every 1 nm in the visible light range of 400 nm to 750 nm is 13,979.

[0203] The integral value (X2) calculated using the transmission spectrum (T%) at every 1 nm interval (wavelength 770 nm to wavelength 790 nm) centered at 780 nm is 1,957.

[0204] It should be noted that since the ratio R (=X2 / X1) of the integral value (X1) to the integral value (X2) is 0.14, Table 1 records the results of the integral value (X1), integral value (X2) and ratio R (=X2 / X1) at a wavelength of 780nm.

[0205] Next, the transmission spectrum (T%) of compound 9 was measured at 1 nm sampling intervals in the wavelength range of 300 nm to 1,000 nm, and the transmission spectrum with a transmittance of 830 nm as 10% is shown below. Figure 9 .according to Figure 9 Similarly, the integral values ​​(X1), (X2), and ratio R (=X2 / X1) at a wavelength of 830nm were also calculated. The results are shown in Table 1.

[0206] Furthermore, the transmission spectrum (T%) of compound 9 was measured at 1 nm sampling intervals within the wavelength range of 300 nm to 1,000 nm, and the transmission spectrum with a transmittance of 850 nm as 10% is shown below. Figure 10 .according to Figure 10 Similarly, the integral values ​​(X1), (X2), and ratio R (=X2 / X1) at a wavelength of 850nm were also calculated. The results are shown in Table 1.

[0207] [Physical Property Evaluation]

[0208] The lower limit of R (=X2 / X1) is 0.09 or more, preferably 0.1 or more, and more preferably 0.11 or more.

[0209] In Examples 1 to 13, for the three types of λ = 780nm, 830nm, and 850nm, the value of the ratio R is included in the above range.

[0210] Regarding Comparative Examples 1 to 3, for any of the three values ​​of λ = 780nm, 830nm, and 850nm, the value of the ratio R is outside the range mentioned above.

[0211] [Regarding color perception in the visible light region]

[0212] The integral value X1 is preferably 17,000 or less.

[0213] In Examples 1 to 13, for the three types of λ = 780nm, 830nm, and 850nm, the value of X1 is included in the above range. Therefore, when it is used to print code information CI, an invisible code shape 20 is formed.

[0214] On the other hand, from the perspective of safety and appearance design, there are also cases where the surface color (background color) of the medium 100 is, for example, black. In such cases, the desired purpose can be achieved by using the materials of Comparative Examples 1 to 3.

[0215] [Influence of particle size]

[0216] Regarding the material of Example 7, the transmittance and the aforementioned ratio R (=X2 / X1) were verified as to vary depending on the particle size, and the results obtained are shown.

[0217] Figure 11 A graph showing the spectral distribution of transmittance as a function of particle size. Figure 12 A graph showing the ratio R (=X2 / X1) of each particle size.

[0218] The experimental conditions (test samples and evaluation methods) are as follows.

[0219] • Pigment: Resin solution = 1:100 (Resin solution = 5 wt% Delpet 80 NEDC solution)

[0220] • Test sample: 2000 rpm spin-coated glass plate (50×50×1mm) • dried at 60℃ for 1 hour

[0221] • Particle size: 0.3μm, 0.5μm, 2.0μm, 0.2μm (only) Figure 12 )

[0222] like Figure 11 As shown, when the particle size is large, the absorption capacity of near-infrared rays decreases (transmittance increases), and a wide spectrum is displayed.

[0223] like Figure 12 As shown, regarding the ratio R (=X2 / X1), the smaller the particle size, the larger the ratio R, exhibiting good light absorption performance in the near-infrared region (780nm, 830nm, 850nm).

[0224] [Regarding weather resistance]

[0225] Figure 13 The test results show the improved weather resistance (light resistance) of near-infrared absorbing materials (pigments).

[0226] The materials of Examples 2, 7 and Comparative Example 2, which were exemplified in the above-described absorbance test, were verified.

[0227] The experimental conditions (test samples and evaluation methods) are as follows.

[0228] • Pigment: Resin solution = 1:100 (Resin solution = 5 wt% Delpet 80 NEDC solution)

[0229] • Test sample: The sample dried at 2000 rpm on a glass plate (50×50×1 mm) at 60℃ for 1 hour was taken as 0 h and obtained by the following light irradiation method.

[0230] • Evaluation device: EYE SUPER UV TESTER (SUV-F11) manufactured by Iwasaki Electric Co., Ltd.

[0231] • Irradiation method: Using a metal halide lamp (295-450nm (100mW / cm²)) 2 The test sample was irradiated at 60℃.

[0232] • Evaluation method: After irradiation begins, the absorbance residual rate (%) is measured every 1 hour.

[0233] Regarding the material of Example 7, even under long light exposure time, a high absorbance retention rate (%), i.e., high weather resistance, can be confirmed.

[0234] Regarding the material of Example 7, its performance can be maintained for a long time when used to print code information CI.

[0235] On the other hand, regarding the materials of Example 2 and Comparative Example 2, in order to maintain high performance over a long period of time, countermeasures such as coating treatment are required.

[0236] In other words, from a safety perspective, maintaining high performance over a long period is sometimes not preferable. In such cases, the desired objective can be achieved by using the materials of Example 2 and Comparative Example 2.

[0237] This application claims priority based on Japanese Patent Application No. 2020-208169, filed on December 16, 2020, the entire disclosure of which is incorporated herein by reference.

[0238] Explanation of reference numerals in the attached figures

[0239] 1 matrix

[0240] Surfaces 1a, 3a, and 6a

[0241] 2 Printed Layer

[0242] 3. Near-infrared absorption layer

[0243] 4. White layer (middle layer)

[0244] 5 Image Layers

[0245] 6. Shielding layer

[0246] 20 Code Shapes

[0247] 21 Reflector

[0248] 22 Absorption section (near-infrared absorption layer)

[0249] 61 Code Mask Section

[0250] 62 Outer frame mask section

[0251] 90 Reading device

[0252] 91 Display Department

[0253] 100 media

[0254] CI code information

[0255] IR (Near Infrared)

[0256] RR reflected light

Claims

1. A medium, which has the following characteristics: Matrix; A near-infrared absorbing layer is disposed on the substrate comprising a near-infrared absorbing material; and The code shape is formed using the near-infrared absorption layer, or by covering a portion of the near-infrared absorption layer, and outputs code information in the form of reflected light from the near-infrared rays when illuminated. In the near-infrared absorbing material, when the integral value of the transmittance of visible light from 400nm to 750nm is set as the first integral value X1, and the integral value of the transmittance over a 20nm wide area centered on the specified wavelength λ of near-infrared light is set as the second integral value X2, the ratio R = X2 / X1 of the first integral value X1 to the second integral value X2 is 0.09 or higher.

2. The medium of claim 1, wherein, The near-infrared absorption layer is configured to completely cover the area on the substrate in which the code shape is set.

3. The medium of claim 1 or 2, wherein, The value of the first integral value X1 is less than 17,000.

4. The medium of claim 1 or 2, wherein, The second integral value X2 is calculated under the condition that the specified wavelength λ is at least one of 780nm, 830nm and 850nm.

5. The medium of claim 1 or 2, wherein, The near-infrared absorbing material is a naphthalene phthalocyanine compound.

6. The medium of claim 5, wherein, The naphthalene phthalocyanine compounds are vanadium oxynaphthalene phthalocyanine compounds that may have substituents.

7. The medium of claim 1 or 2, wherein, The near-infrared absorbing material is a pigment, and the particle diameter D 50 is 0.05 μm or more and 1.0 μm or less.

8. The medium of claim 1 or 2, wherein, There is an intermediate layer with a near-infrared light reflectivity of more than 70% between the substrate and the near-infrared absorption layer.

9. The medium as claimed in claim 1 or 2, having an image layer that covers the code shape and has a near-infrared transmittance of 80% or more.

Images