JP7577273B2 - Recording medium - Google Patents

Description

This disclosure provides a recording medium.

Patent Document 1 discloses a film in which a multilayer pearlescent film (1) having the ability to transmit both visible light and infrared light is provided on one side with a printed layer (3a) having a pattern, letters, etc. having the ability to absorb infrared light, and a printed layer (3b) having a pattern, letters, etc. having the ability to transmit infrared light, and the printed layer (3a) and the printed layer (3b) appear to be the same color under normal light, but have different spectral reflectances in the infrared region.
Patent Document 2 discloses a printed matter in which individual information is displayed on a substrate having a glossy surface formed entirely or partially thereon, and at least a part of the glossy surface is made visible.

Patent Document 3 discloses a method for producing a metallic gloss film made of a thiophene polymer by electrolytic polymerization of a thiophene monomer on a conductor by a potential sweep method.
Patent Document 4 discloses a film having metallic luster that contains a thiophene polymer.
Patent Document 5 discloses a coating liquid for forming a metallic coating film, which contains polythiophene and is doped with chloride ions or perchlorate ions.
Patent Document 6 discloses a film having a gold or copper luster, which contains a thiophene polymer doped with at least one of perchlorate ions, hexafluorophosphate ions, tetrafluoroborate ions, chloride ions, and paratoluenesulfonate ions.
Patent Document 7 discloses a solution for producing an article having a metallic luster, which contains at least one of a polyester resin, a polycarbonate resin, a polyvinylpyrrolidone resin, a polystyrene resin, a polymethyl methacrylate resin, and a styrene-acrylic copolymer resin, a thiophene polymer, and a solvent.

JP 2004-142129 A Japanese Patent Application Publication No. 10-850 JP 2017-052856 A JP 2017-110232 A Patent No. 6031197 Patent No. 6308624 JP 2018-012831 A

As the performance of electrophotographic copying machines, computer scanners, and multi-color printers improves, there is a risk that counterfeiting of banknotes, securities, credit cards, etc. will become easier and more sophisticated than ever before.

The embodiments of the present disclosure have been made under the above circumstances.
An embodiment of the present disclosure aims to provide a recording medium that makes it easier to distinguish between an original and a copy, as compared with a case in which the weight-average molecular weight of the thiophene polymer contained in the metallic luster layer is less than 200 or exceeds 30,000, or a case in which the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms, and Ce atoms in the metallic luster layer exceeds 1,500 ppm with respect to the thiophene polymer, and an object of the present disclosure is to achieve this.

Specific means for solving the above problems include the following aspects.
<1> A substrate,
A metallic luster layer containing a thiophene polymer provided on the substrate,
the weight average molecular weight of the thiophene polymer contained in the metallic luster layer is 200 or more and 30,000 or less;
the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer is 1500 ppm or less relative to the thiophene polymer;
Recording medium.
<2> The recording medium according to <1>, further comprising a metal layer between the substrate and the metallic luster layer.
<3> The recording medium according to <2>, wherein the metal layer contains at least one metal selected from the group consisting of Au, Ag, Cu, and Al.
<4> The recording medium according to any one of <1> to <3>, wherein the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms, and Ce atoms in the metallic luster layer is 500 ppm or less with respect to the thiophene polymer.
<5> The recording medium according to any one of <1> to <4>, wherein the weight-average molecular weight of the thiophene polymer contained in the metallic luster layer is 500 or more and 20,000 or less.
<6> The recording medium according to any one of <1> to <5>, wherein the thiophene polymer includes a polymer of at least one selected from the group consisting of an alkoxythiophene, an alkylthiophene, an aminothiophene, and a hydroxythiophene.
<7> The recording medium according to <6>, wherein the thiophene polymer includes a polymer in which at least an alkoxythiophene is polymerized, and the alkoxythiophene includes an alkoxythiophene having an alkoxy group having 1 to 6 carbon atoms.
<8> The recording medium according to <6> or <7>, wherein the thiophene polymer includes a polymer of at least an alkylthiophene, and the alkylthiophene includes an alkylthiophene having an alkyl group having 1 to 6 carbon atoms.

According to <1>, <6>, <7> and <8>, a recording medium is provided which makes it easier to distinguish between the original and a copy, compared with a case in which the weight-average molecular weight of the thiophene polymer contained in the metallic luster layer is less than 200 or exceeds 30,000, or a case in which the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer exceeds 1,500 ppm with respect to the thiophene polymer.
According to items <2> and <3>, a recording medium is provided which makes it easier to distinguish between the original and the copy, as compared with a recording medium which does not have a metal layer between the base material and the metallic gloss layer.
According to <4>, a recording medium is provided which makes it easier to distinguish between the original and a copy, as compared with a case in which the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms, and Ce atoms in the metallic luster layer exceeds 500 ppm with respect to the thiophene polymer.
According to <5>, a recording medium is provided which makes it easier to distinguish between the original and a copy, as compared with a case in which the weight-average molecular weight of the thiophene polymer contained in the metallic luster layer is less than 500 or exceeds 20,000.

1 is a schematic cross-sectional view showing an example of a recording medium according to an embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing another example of a recording medium according to the present embodiment.

Embodiments of the present disclosure are described below. These descriptions and examples are intended to illustrate the embodiments and are not intended to limit the scope of the embodiments.

In the numerical ranges described in this disclosure in stages, the upper or lower limit value described in one numerical range may be replaced with the upper or lower limit value of another numerical range described in stages. Also, in the numerical ranges described in this disclosure, the upper or lower limit value of that numerical range may be replaced with a value shown in the examples.

In this disclosure, the term "process" includes not only independent processes, but also processes that cannot be clearly distinguished from other processes, as long as the intended purpose of the process is achieved.

When embodiments of this disclosure are described with reference to drawings, the configuration of the embodiment is not limited to the configuration shown in the drawings. In addition, the sizes of components in each drawing are conceptual, and the relative relationships between the sizes of components are not limited to these.

In this disclosure, each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition in this disclosure, if there are multiple substances corresponding to each component in the composition, the total amount of those multiple substances present in the composition is meant unless otherwise specified.

<Recording media>
The recording medium of this embodiment includes a recording medium onto which information indicating that the recording medium has a specific value is to be recorded (i.e., the recording medium before the information is recorded), and a recording medium onto which information indicating that the recording medium has a specific value is recorded.
Information indicating that a recording medium has a specific value (hereinafter simply referred to as "information") includes, for example, words such as "stock certificate" or "securities", amounts, serial numbers, trademarks, symbols, logos, emblems, bar codes, QR codes (registered trademarks), country names, company names, locations, telephone numbers, names, dates of birth, ages, biometric information (for example, fingerprint shapes, vein shapes), warranty expiration dates, warranty contents, usage methods, and the like.
Methods of recording information include methods that can be recognized by human perception and methods that cannot be recognized by human perception (for example, electronic methods and magnetic methods).

Examples of recording media in this embodiment on which information is recorded include banknotes, revenue stamps, certificates, postage stamps, postcards; securities such as gift certificates, stock certificates, bonds, bills, checks, insurance policies, lottery tickets, etc.; credit cards, cash cards, debit cards, prepaid cards; passports, visas, health insurance cards, driver's licenses, ID cards; tickets, boarding passes, airline tickets, boat tickets, admission tickets, and exhibition tickets.
In other words, the recording medium according to this embodiment before information is recorded thereon is a material for producing the above-mentioned article.

The recording medium according to this embodiment has a substrate and a metallic luster layer containing a thiophene polymer provided on the substrate, and the metallic luster layer has the following characteristics (1) and (2).
(1) The weight-average molecular weight of the thiophene polymer contained in the metallic luster layer is 200 or more and 30,000 or less.
(2) The total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer is 1500 ppm or less based on the thiophene polymer.
ppm is an abbreviation for parts per million, and the above (2) is based on mass.

A thiophene polymer is a polymer formed by polymerizing two or more thiophenes. A film containing a thiophene polymer exhibits a metallic luster due to the reflection of light of a specific wavelength by the layer-oriented thiophene polymer. A metallic luster film containing a thiophene polymer is expected to be used as an anti-counterfeiting image for securities and the like, since it is difficult to reproduce the metallic luster by an electrophotographic copier or multicolor printer. In the recording medium according to the present embodiment, the metallic luster layer containing the thiophene polymer has the above characteristics (1) and (2), and therefore the metallic luster layer has excellent metallic luster and little uneven luster, making it more difficult to reproduce the metallic luster by an electrophotographic copier or multicolor printer, and making it easy to distinguish between the original and the copy.

Figure 1 is a schematic cross-sectional view showing an example of a recording medium according to this embodiment. The recording medium 10 shown in Figure 1 has a metallic luster layer 14 on a substrate 12. One side of the metallic luster layer 14 is exposed and is recognized by human vision. The metallic luster layer 14 may be on one side of the substrate 12 as shown in Figure 1, or on both sides of the substrate 12. The metallic luster layer 14 may be on a part of the surface of at least one side of the substrate 12, or on the entire surface. Information may be recorded on the substrate 12. Information may be recorded on the metallic luster layer 14.

Figure 2 is a schematic cross-sectional view showing another example of the recording medium according to this embodiment. The recording medium 20 shown in Figure 2 has a metal layer 23 on a substrate 22, and a metallic gloss layer 24 on the metal layer 23. One side of the metallic gloss layer 24 is exposed and can be recognized by human vision. The area where the metal layer 23 and the metallic gloss layer 24 are laminated exhibits a stronger metallic gloss, making it more difficult to reproduce the metallic gloss using an electrophotographic copier or multi-color printer. The metal layer 23 and the metallic gloss layer 24 may be on one side of the substrate 22 as shown in Figure 2, or on both sides of the substrate 22. The metal layer 23 and the metallic gloss layer 24 may be on a part of the surface or on the entire surface of at least one side of the substrate 22. Information may be recorded on the substrate 22. Information may be recorded on the metallic gloss layer 24.

Although not shown in FIG. 1 and FIG. 2, a transparent protective layer may be laminated on the metallic gloss layer 14 or the metallic gloss layer 24. Examples of the transparent protective layer include a resin film and a resin sheet. The recording medium 10 or the recording medium 20 may have a transparent protective layer on one or both of its entire surfaces.

Although not shown in FIG. 1 and FIG. 2, the recording medium 10 or the recording medium 20 may have a code or tag that can be detected by electromagnetic waves. The code or tag is provided, for example, at a position on the substrate 12 (or the substrate 22) where the metallic gloss layer 14 (or the metallic gloss layer 24) is not present.

The recording medium according to this embodiment may have both the form shown in FIG. 1 and the form shown in FIG. 2. For example, one surface of the substrate may have the form shown in FIG. 1, and the other surface of the substrate may have the form shown in FIG. 2.

The metallic luster layer 14 is preferably present at least on the front surface (the surface having the main information) of the recording medium 10. The metallic luster layer 14 may be present on the back surface (the surface opposite to the front surface) of the recording medium 10, or on both surfaces of the recording medium 10. The area of the metallic luster layer 14 is not particularly limited.
The form of the metallic luster layer 24 is similar to that of the metallic luster layer 14 described above.

The shape of the metallic luster layer 14 is not particularly limited. The metallic luster layer 14 may be information, or may be a graphic or pattern that is not information. Examples of information that the metallic luster layer 14 constitutes include monetary amounts, trademarks, symbols, logos, and emblems. When the metallic luster layer 14 is a graphic or pattern that is not information, it is preferable that the metallic luster layer 14 be located in a position separate from or below the information so as not to interfere with reading of the information.
The form of the metallic luster layer 24 is similar to that of the metallic luster layer 14 described above.

From the viewpoint of preventing the metallic luster layer 14 from being cut off or replaced, a plurality of metallic luster layers 14 may be disposed at appropriate intervals over the entire front surface or the entire back surface of the recording medium 10. The metallic luster layer 14 may be, for example, in a frame shape that fits along the edge of the recording medium 10.
The form of the metallic luster layer 24 is similar to that of the metallic luster layer 14 described above.

The substrate, metallic gloss layer, and metal layer are described in detail below. Reference numerals will be omitted in the following description.

[Substrate]
Examples of the substrate for the recording medium include paper, coated paper, cloth, resin sheets, films or plates, metal sheets, films or plates, glass plates, ceramic plates, resin sheets coated or vapor-deposited with a magnetic material, and composites of these. The substrate may have a member (e.g., an integrated circuit, magnetic tape) inside or on its surface that records information by an electronic or magnetic method.

The material, shape, and thickness of the substrate may be selected depending on the purpose of the recording medium. Information may be recorded on the substrate prior to the formation of the metallic gloss layer.

[Metallic gloss layer]
The metallic luster layer contains at least a thiophene polymer. The metallic luster layer may further contain a resin, a filler, and the like.

A thiophene polymer is a polymer formed by polymerizing two or more thiophenes. The thiophene polymer may be a polymer formed by polymerizing one type of thiophene, or may be a polymer formed by polymerizing multiple types of thiophenes. An example of a thiophene polymer is a polymer represented by the following general formula:

In the above general formula, R is a substituent, m is 1 or 2, and n is an integer of 2 or more. R may be one type or multiple types. When m is 2, the two Rs in one thiophene ring may be the same type or different types. When m is 2, the two Rs in one thiophene ring may be linked to form a cyclic group.

R represents, for example, an alkoxy group, an alkyl group, an amino group, a hydroxy group, a hydroxyalkyl group, an aryl group, an allyl group, a cyano group, or a halogeno group. From the viewpoint of providing a metallic gloss layer with superior metallic gloss, R is preferably an alkoxy group, an alkyl group, an amino group, or a hydroxy group, more preferably an alkoxy group, an alkyl group, or an amino group, and even more preferably an alkoxy group or an alkyl group.

When R is an alkoxy group, the number of carbon atoms in the alkoxy group is preferably 1 or more and 8 or less, more preferably 1 or more and 6 or less, even more preferably 1 or more and 4 or less, and particularly preferably 1 or 2, from the viewpoint of facilitating the orientation of the thiophene polymer in a layer form.
Examples of thiophenes having at least one alkoxy group include 3-methoxythiophene, 3,4-dimethoxythiophene, 3-ethoxythiophene, 3,4-diethoxythiophene, 3-propoxythiophene, 3-butoxythiophene, 3,4-ethylenedioxythiophene, and 3,4-propylenedioxythiophene.

When R is an alkyl group, the number of carbon atoms in the alkyl group is preferably 1 or more and 12 or less, more preferably 1 or more and 8 or less, even more preferably 1 or more and 6 or less, still more preferably 1 or more and 4 or less, and particularly preferably 1 or 2, from the viewpoint of facilitating the orientation of a layer in the thiophene polymer.
Examples of thiophenes having at least one alkyl group include 3-methylthiophene, 3,4-dimethylthiophene, 3-ethylthiophene, 3,4-diethylthiophene, 3-butylthiophene, 3-hexylthiophene, 3-heptylthiophene, 3-octylthiophene, 3-nonylthiophene, 3-decylthiophene, 3-undecylthiophene, 3-dodecylthiophene, and 3-bromo-4-methylthiophene.

When R is an amino group, the amino group may be a primary amino group (-NH ₂ ), a secondary amino group (-NHR ¹ , R ¹ is an alkyl group or an aryl group, preferably an alkyl group), or a tertiary amino group (-NR ¹ R ² , R ¹ and R ² are each independently an alkyl group or an aryl group, preferably an alkyl group). The number of carbon atoms in the alkyl group in the secondary amino group or tertiary amino group is preferably 1 or 2, from the viewpoint of facilitating layer-like orientation of the thiophene polymer.
Examples of thiophenes having at least one amino group include 3-aminothiophene, 3,4-diaminothiophene, 3-methylaminothiophene, and 3-dimethylaminothiophene.

As the thiophene polymer, from the viewpoint of the metallic luster layer being superior in metallic luster, a polymer in which at least one selected from the group consisting of alkoxythiophenes, alkylthiophenes, aminothiophenes, and hydroxythiophenes is polymerized is preferable, a polymer in which at least one selected from the group consisting of alkoxythiophenes and alkylthiophenes is polymerized is more preferable, and a poly(alkoxythiophene) in which only alkoxythiophenes are polymerized, a poly(alkylthiophene) in which only alkylthiophenes are polymerized, or a poly(alkylthiophene) (alkoxythiophene) in which only alkylthiophenes and alkoxythiophenes are polymerized is even more preferable. The number of carbon atoms of the alkoxy group in the alkoxythiophene is preferably 1 to 8, more preferably 1 to 6, even more preferably 1 to 4, and particularly preferably 1 or 2. The number of carbon atoms of the alkyl group in the alkylthiophene is preferably 1 to 12, more preferably 1 to 8, even more preferably 1 to 6, even more preferably 1 to 4, and particularly preferably 1 or 2.

The thiophene polymer contained in the metallic luster layer has a weight average molecular weight of 200 to 30,000, preferably 500 to 20,000, and more preferably 1,000 to 10,000, from the viewpoint of facilitating layer-like orientation of the thiophene polymer.

The molecular weight of the thiophene polymer contained in the metallic luster layer is measured by dissolving the metallic luster layer in a solvent capable of dissolving the thiophene polymer and extracting the thiophene polymer.
The molecular weight of the thiophene polymer is measured by gel permeation chromatography (GPC) using an HPLC1100 manufactured by Tosoh Corporation as a measuring device, two TSKgel GMHHR-M columns (inner diameter 7.8 mm, length 30 cm) manufactured by Tosoh Corporation arranged in series, chloroform as a solvent, and monodisperse polystyrene as a standard sample.

The total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer is 1500 ppm or less relative to the thiophene polymer in order to suppress uneven luster in the metallic luster layer. If the total content of the metal atoms is excessive, the layered orientation of the thiophene polymer is disturbed, and uneven luster is likely to occur in the metallic luster. The total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer is preferably 500 ppm or less, more preferably 100 ppm or less, relative to the thiophene polymer.
However, in order to stabilize the doped state of the thiophene polymer, the thiophene polymer preferably contains a small amount of the above metal atoms, and the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms, and Ce atoms is preferably 1 ppm or more, and more preferably 5 ppm or more, relative to the thiophene polymer.

The total content (ppm) of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the thiophene polymer is determined as follows.
The metallic luster layer is dissolved in nitric acid to obtain a nitric acid solution. The nitric acid solution is heated by microwave irradiation (maximum temperature reached: 260°C) to incinerate the nitric acid solution, and the ashes are dissolved or dispersed in water to obtain a liquid composition. This liquid composition is used as a sample, and the metal atoms and S atoms are quantified by inductively coupled plasma optical emission spectrometry (ICP-OES), to obtain the ratio of S atoms to each metal atom. The total content (ppm) of Fe atoms, Cu atoms, Mn atoms, Cr atoms, and Ce atoms relative to the thiophene polymer is calculated from the amount of thiophene polymer (converted from the amount of S atoms) and the amount of metal atoms contained in a unit amount of the metallic luster layer.

The thickness of the metallic gloss layer is preferably a thickness that exhibits metallic gloss, specifically, 0.01 μm or more and 200 μm or less.

The metallic gloss layer can be formed, for example, using a composition for forming a metallic gloss layer. Examples of compositions for forming a metallic gloss layer include ink in which a thiophene polymer is dissolved in a solvent; and toner to which a thiophene polymer is added internally or externally. Methods for forming a metallic gloss layer include, for example, screen printing, offset printing, inkjet printing, and electrophotography.

After forming the metallic gloss layer on the substrate or metal layer, it is preferable to apply pressure to the metallic gloss layer in order to adhere the metallic gloss layer to the substrate or metal layer. Pressurization also includes rubbing.

The thiophene polymer for producing the composition for forming the metallic luster layer is synthesized, for example, by oxidative polymerization. The oxidative polymerization method is a method for polymerizing thiophenes in the liquid or solid phase using an oxidizing agent.

Examples of oxidizing agents include ferric salts, cupric salts, cerium salts, dichromates, permanganates, ammonium persulfate, boron trifluoride, bromates, hydrogen peroxide, chlorine, bromine, and iodine.

The oxidizing agent is preferably a ferric salt, which may be in the form of a hydrate.
Examples of counter ions of the ferric salt include chloride ions, citrate ions, oxalate ions, paratoluenesulfonate ions, perchlorate ions, hexafluorophosphate ions, tetrafluoroborate ions, etc. When at least one of the perchlorate ions, hexafluorophosphate ions, and tetrafluoroborate ions is used as the counter ion of the ferric salt, a film exhibiting a gloss close to gold can be formed.

When an oxidizing agent whose counter ion is a perchlorate ion, a hexafluorophosphate ion, a tetrafluoroborate ion, or a chloride ion is used, these counter ions remain stably bound to the thiophene polymer, and the metallic luster state can be stably maintained.

The oxidative polymerization is preferably carried out in a solvent. The solvent is preferably one that dissolves the thiophenes and the oxidizing agent and efficiently polymerizes the thiophenes. The solvent is preferably an organic solvent that has high polarity and a certain degree of volatility.

Examples of solvents include acetonitrile, nitromethane, γ-butyrolactone, propylene carbonate, nitromethane, 1-methyl-2-pyrrolidinone, dimethylsulfoxide, 2-butanone, tetrahydrofuran, acetone, methanol, anisole, chloroform, ethyl acetate, hexane, trichloroethylene, cyclohexanone, dichloromethane, chloroform, dimethylformamide, ethanol, butanol, pyridine, dioxane, and mixtures thereof.

From the viewpoint of providing a metallic gloss layer with superior metallic gloss, the solvent is preferably an aprotic polar solvent, and more preferably at least one selected from the group consisting of acetonitrile, nitromethane, γ-butyrolactone, and propylene carbonate.

The mass ratio of the solvent to the thiophenes, solvent:thiophenes, is preferably from 1:0.00007 to 1:7, and more preferably from 1:0.0007 to 1:0.7.
For example, when the oxidizing agent is iron(III) perchlorate n-hydrate (2D), the mass ratio of the solvent to the oxidizing agent is preferably solvent:iron(III) perchlorate n-hydrate (2D)=1:0.0006 to 1:6, and more preferably 1:0.006 to 1:0.6.
The mass ratio of the thiophenes to the oxidizing agent, thiophenes:oxidizing agent, is preferably from 1:0.1 to 1:1000, and more preferably from 1:1 to 1:100.

The technique of oxidative polymerization is not particularly limited. The thiophenes and the oxidizing agent may be added to a solvent at once and dissolved to perform oxidative polymerization, or a solution in which the thiophenes are dissolved in a solvent and a solution in which the oxidizing agent is dissolved in a solvent may be separately prepared, and the two solutions may be mixed to perform oxidative polymerization.

The molecular weight of the thiophene polymer can be adjusted by changing the concentration of thiophenes, reaction temperature, and reaction time in the oxidative polymerization.

The thiophene polymer synthesized by the oxidative polymerization method may be used as a solution, or the solvent may be removed to use the thiophene polymer in powder form.

The powdered thiophene polymer may contain impurities derived from the oxidizing agent used in the oxidative polymerization. In order to remove the impurities, it is preferable to carry out at least one of the following treatments (a), (b), and (c). By carrying out at least one of the following treatments (a), (b), and (c), the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms, and Ce atoms contained in the metallic luster layer can be reduced.
(a) The thiophene polymer is washed using a poor solvent.
(b) A solution in which a thiophene polymer is dissolved in a good solvent is dropped into a poor solvent to precipitate the thiophene polymer.
(c) A poor solvent is dropped into a solution in which a thiophene polymer is dissolved in a good solvent, thereby precipitating the thiophene polymer.
As the poor solvent, alcohols such as methanol, ethanol, and isopropanol are preferable, and as the good solvent, dimethylformamide, dimethylsulfoxide, and tetrahydrofuran are preferable.

An example of a method for forming a metallic gloss layer is electrolytic polymerization. Electrolytic polymerization is a method in which a film made of an insoluble polymer is formed on a conductor by electrochemically oxidizing a monomer in an electrolytic solution in which the monomer is dissolved in a solvent containing a supporting electrolyte. According to electrolytic polymerization, a metallic gloss layer containing a thiophene polymer can be directly formed on a conductive substrate or on a metal layer provided on a substrate using thiophenes as a raw material.

Examples of solvents for electrolytic polymerization include water, alcohol, and mixed solvents of these. Solvents described in "Electrochemical Measurement Methods, Vol. 1," pp. 107-114 (Akira Fujishima, Masuo Aizawa, Toru Inoue, Gihodo Publishing, 1984) may also be used.

The supporting electrolyte is preferably one that is sufficiently soluble in the solvent and is not easily electrolyzed. In terms of the cation, preferred supporting electrolytes are lithium salts, sodium salts, potassium salts, calcium salts, and tetraalkylammonium salts, and in terms of the anion, preferred supporting electrolytes are halides, sulfates, nitrates, phosphates, perchlorates, boron trifluorides, and hexafluorophosphates.

The concentration of thiophenes in the electrolytic solution is preferably 0.1 mmol/L or more and the solubility thereof or less, and more preferably 1 mmol/L or more and 1 mol/L or less.
The concentration of the supporting electrolyte in the electrolytic solution is preferably 0.001 mol/L or more and the solubility or less, and more preferably 0.01 mol/L or more and 1 mol/L or less.

The electrolytic polymerization method is preferably a three-electrode method using a conductor that functions as a working electrode, a counter electrode, and a reference electrode that serves as a potential standard, or a two-electrode method using a conductor that functions as a working electrode and a counter electrode. The three-electrode method is preferred from the viewpoint of being able to polymerize the desired thiophene polymer with good reproducibility.

The material of the conductor functioning as the working electrode is preferably a substance that is stable against electrode oxidation, whether in the three-electrode or two-electrode system. For example, an electrode coated with a conductive film such as indium tin oxide or tin oxide (transparent glass electrode, metal electrode, glassy carbon electrode, etc.) is preferred. As the counter electrode, the above-mentioned electrodes, stainless steel, copper plate, or other metal electrodes are preferred. As the reference electrode, an Ag/AgCl electrode or a saturated calomel electrode is preferred.

When anodizing in electrolytic polymerization, it is preferable to use the potential sweep method. The potential sweep method refers to a process in which a potential is applied while being changed at a constant rate.

In the potential sweep method, it is preferable to sweep between a negative potential and a positive potential. In this case, the negative potential is preferably in the range of -1.5 V or more and -0.01 V or less, more preferably in the range of -1.0 V or more and -0.1 V or less, and even more preferably in the range of -0.7 V or more and -0.2 V or less. The positive potential is preferably in the range of +1.0 V or more and +3.0 V or less, more preferably in the range of +1.0 V or more and +2.0 V or less, and even more preferably in the range of +1.0 V or more and +1.5 V or less.
The sweep rate in the potential sweep method is preferably in the range of 0.1 mV/sec to 10 V/sec, more preferably in the range of 1 mV/sec to 1 V/sec, and further preferably in the range of 2 mV/sec to 300 mV/sec.

The time for electrolytic polymerization is preferably in the range of 1 second to 5 hours, more preferably in the range of 10 seconds to 1 hour.
The temperature of electrolysis during electrolytic polymerization is preferably in the range of -20°C or higher and 60°C or lower.

Electrolysis during electropolymerization is a reaction that involves little atmospheric components and is carried out at a relatively low potential, so it can be carried out in the air. It is preferable to carry out the process in a nitrogen or argon gas atmosphere to avoid the possibility of contaminating the formed film, such as by oxidizing impurities in the electrolyte, but there is little risk of contamination. Nevertheless, the presence of a large amount of oxygen in the electrolyte solution can affect the electrode reaction, so bubbling with an inert gas (nitrogen gas or argon gas) is also useful.

After forming the metallic gloss layer by electrolytic polymerization, it is preferable to apply pressure to the metallic gloss layer in order to fix the metallic gloss layer onto the substrate or metal layer. Pressurization also includes rubbing.

[Metal Layer]
The recording medium according to this embodiment preferably has a metal layer between the substrate and the metallic gloss layer. By having a metal layer below the metallic gloss layer, the metallic gloss of the metallic gloss layer becomes more excellent.

From the viewpoint of increasing the metallic luster of the metal layer and the metallic luster layer, it is preferable that the metal layer is a metal layer containing at least one metal selected from the group consisting of Au, Ag, Cu, and Al.

The metal layer contains at least a metal. The metal layer may further contain a resin, a filler, etc.

A known film-forming method can be used to form the metal layer. Examples include plating such as electroless plating, vacuum deposition, sputtering, and ion plating; coating using a coating liquid containing metal powder and resin; and image formation using metallic toner containing metal powder.

The thickness of the metal layer is preferably 0.02 μm or more and 200 μm or less.

The ratio of the thickness of the metallic gloss layer to the thickness of the metal layer is preferably metallic gloss layer thickness:metal layer thickness=1:0.001 to 1:2000, and more preferably 1:0.05 to 1:20.

The present embodiment will be described in more detail below by way of examples, but the present embodiment is not limited to the following examples. Unless otherwise specified, "parts" and "%" are by weight. Synthesis, processing, manufacturing, etc. were performed at room temperature (25°C ± 3°C) unless otherwise specified.

Example 1
[Synthesis of thiophene polymer]
11.4 g of 3-methoxythiophene was placed in a three-necked flask, and 0.5 L of acetonitrile was added to dissolve 3-methoxythiophene in acetonitrile. The atmosphere in the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 101 g of iron (III) perchlorate n-hydrate [II] was dissolved in 0.5 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 1 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected and dried at 60°C under reduced pressure for 16 hours to obtain 10.5 g of a thiophene polymer.

[Methanol washing]
2.0 g of the synthesized thiophene polymer was placed in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45° C., and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid content was placed in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45° C., and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, and the solid content was collected and dried at 60° C. under reduced pressure for 16 hours to obtain 1.8 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3,000.

[Preparation of coating liquid]
1.0 g of the thiophene polymer after washing with methanol was dissolved in 99 g of nitromethane, stirred with a stirrer for 1 hour, and then allowed to stand for 22 hours to obtain a coating liquid.

[Formation of metallic gloss layer]
The coating liquid was applied to a regular wood-free paper (C2 paper, Fuji Xerox Co., Ltd.) in a square shape with a side length of 10 mm, and then dried at a temperature of 25° C. for 45 minutes to form a metallic gloss layer. The metallic gloss layer had a thickness of about 1.0 μm.

<Examples 2 to 5, Comparative Examples 1 and 2>
Thiophene polymers having different weight average molecular weights were synthesized in the same manner as in Example 1, except that the concentration of 3-methoxythiophene, the reaction temperature, and the reaction time in the synthesis of the thiophene polymer were changed, and the polymers were washed with methanol in the same manner as in Example 1. In this manner, thiophene polymers having the weight average molecular weights shown in Table 1 were obtained, respectively. Then, a coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1. The metallic gloss layer had a thickness of about 1.0 μm.

<Comparative Example 3>
A metallic glossy layer was formed in the same manner as in Example 1, except that the synthesized thiophene polymer was used for the preparation of a coating liquid without being washed with methanol. The metallic glossy layer had a thickness of about 1.0 μm.

<Comparative Example 4>
A coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1, except that the methanol washing was changed as follows. The metallic gloss layer had a thickness of about 1.0 μm.

[Methanol washing]
2.0 g of the synthesized thiophene polymer was placed in a beaker, 50 mL of methanol was added, and the mixture was stirred for 1 hour. Then, the mixture was subjected to solid-liquid separation using a centrifuge, and the solid matter was collected and dried at 60° C. under reduced pressure for 16 hours to obtain 1.8 g of the thiophene polymer.

Example 6
A coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1, except that the methanol washing was changed to the following precipitation treatment. The metallic gloss layer had a thickness of about 1.0 μm.

[Precipitation treatment]
2.0 g of the synthesized thiophene polymer was placed in a beaker and dissolved in 100 mL of dimethylformamide. This solution was added dropwise to 500 mL of isopropyl alcohol over 30 minutes to gradually precipitate a solid. Then, solid-liquid separation was performed using a centrifuge, and the solid was collected and dried at 60° C. under reduced pressure for 16 hours to obtain 1.85 g of a thiophene polymer.

Example 7
A coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1, except that the methanol washing was changed to the following precipitation treatment and methanol washing. The metallic gloss layer had a thickness of about 1.0 μm.

[Precipitation and methanol washing]
2.0 g of the synthesized thiophene polymer was taken in a beaker and dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate a solid. Then, solid-liquid separation was performed using a centrifuge, the solid content was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid content was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 1.8 g of a thiophene polymer.

Example 8
[Synthesis of thiophene polymer]
2.28 g of 3-methoxythiophene was placed in a three-necked flask, and 0.1 L of acetonitrile was added to dissolve 3-methoxythiophene in acetonitrile. The atmosphere in the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 24.5 g of copper (II) tetrafluoroborate hexahydrate was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 2.0 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3200.

[Preparation of coating liquid]
1.0 g of the thiophene polymer after washing with methanol was dissolved in 99 g of nitromethane, stirred with a stirrer for 1 hour, and then allowed to stand for 22 hours to obtain a coating liquid.

[Formation of metallic gloss layer]
The coating liquid was applied to a regular wood-free paper (C2 paper, Fuji Xerox Co., Ltd.) in a square shape with a side length of 10 mm, and then dried at a temperature of 25° C. for 45 minutes to form a metallic gloss layer. The metallic gloss layer had a thickness of about 1.0 μm.

<Example 9>
[Synthesis of thiophene polymer]
3.1 g of 3-methoxythiophene was placed in a three-necked flask, and 0.1 L of acetonitrile was added to dissolve 3-methoxythiophene in acetonitrile. The atmosphere inside the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 15.8 g of potassium permanganate was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 2.0 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3300.

[Preparation of coating liquid]
1.0 g of the thiophene polymer after washing with methanol was dissolved in 99 g of nitromethane, stirred with a stirrer for 1 hour, and then allowed to stand for 22 hours to obtain a coating liquid.

[Formation of metallic gloss layer]
The coating liquid was applied to a regular wood-free paper (C2 paper, Fuji Xerox Co., Ltd.) in a square shape with a side length of 10 mm, and then dried at a temperature of 25° C. for 45 minutes to form a metallic gloss layer. The metallic gloss layer had a thickness of about 1.0 μm.

Example 10
3.1 g of 3-methoxythiophene was placed in a three-necked flask, and 0.1 L of acetonitrile was added to dissolve 3-methoxythiophene in acetonitrile. The atmosphere inside the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 19.7 g of potassium dichromate was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 2.0 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3400.

[Preparation of coating liquid]
1.0 g of the thiophene polymer after washing with methanol was dissolved in 99 g of nitromethane, stirred with a stirrer for 1 hour, and then allowed to stand for 22 hours to obtain a coating liquid.

[Formation of metallic gloss layer]
The coating liquid was applied to a regular wood-free paper (C2 paper, Fuji Xerox Co., Ltd.) in a square shape with a side length of 10 mm, and then dried at a temperature of 25° C. for 45 minutes to form a metallic gloss layer. The metallic gloss layer had a thickness of about 1.0 μm.

Example 11
3.1 g of 3-methoxythiophene was placed in a three-necked flask, and 0.1 L of acetonitrile was added to dissolve 3-methoxythiophene in acetonitrile. The atmosphere in the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 54.8 g of cerium (IV) ammonium nitrate was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 2.0 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3100.

[Preparation of coating liquid]
1.0 g of the thiophene polymer after washing with methanol was dissolved in 99 g of nitromethane, stirred with a stirrer for 1 hour, and then allowed to stand for 22 hours to obtain a coating liquid.

[Formation of metallic gloss layer]
The coating liquid was applied to a regular wood-free paper (C2 paper, Fuji Xerox Co., Ltd.) in a square shape with a side length of 10 mm, and then dried at a temperature of 25° C. for 45 minutes to form a metallic gloss layer. The metallic gloss layer had a thickness of about 1.0 μm.

Example 12
[Synthesis of thiophene polymer]
3.1 g of 3-butoxythiophene was placed in a three-necked flask, and 0.1 L of acetonitrile was added, and 3-butoxythiophene was dissolved in acetonitrile. The atmosphere in the three-necked flask was then replaced with nitrogen, and the flask was cooled to 0°C. A solution in which 20 g of iron (III) perchlorate n-hydrate [II] was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature, and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added, and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 1.9 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3200.

Using the thiophene polymer after methanol washing, a coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1. The thickness of the metallic gloss layer was approximately 1.0 μm.

<Example 13>
[Synthesis of thiophene polymer]
0.02 g of 3-methylthiophene and 2.05 g of 3-methoxythiophene were placed in a three-necked flask, and 0.1 L of acetonitrile was added to dissolve the thiophenes in the acetonitrile. The atmosphere in the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 20 g of iron (III) perchlorate n-hydrate [II] was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 1.9 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3200.

Using the thiophene polymer after methanol washing, a coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1. The thickness of the metallic gloss layer was approximately 1.0 μm.

<Example 14>
[Synthesis of thiophene polymer]
0.03 g of 3,4-ethylenedioxythiophene and 2.05 g of 3-methoxythiophene were placed in a three-necked flask, and 0.1 L of acetonitrile was added to dissolve the thiophenes in the acetonitrile. The atmosphere in the three-necked flask was then replaced with nitrogen and cooled to 0°C. A solution in which 20 g of iron (III) perchlorate n-hydrate [II] was dissolved in 0.1 L of acetonitrile was then added dropwise while maintaining the solution and the reaction system at 5°C or lower. The temperature was then raised to room temperature and the mixture was stirred at room temperature for 15 hours. 0.2 L of methanol was then added and the mixture was stirred for 1 hour. The mixture was then subjected to solid-liquid separation using a centrifuge, and the solid content was collected.

[Precipitation and methanol washing]
The collected solid was dissolved in 100 mL of dimethylformamide. While stirring this solution, 1 L of isopropyl alcohol was dropped over 30 minutes to gradually precipitate the solid. Then, solid-liquid separation was performed using a centrifuge, the solid was taken in a beaker, 50 mL of methanol was added, the liquid temperature was adjusted to 45 ° C, and the mixture was stirred for 1 hour. Then, solid-liquid separation was performed using a centrifuge, the solid was collected, and dried at 60 ° C under reduced pressure for 16 hours to obtain 1.9 g of a thiophene polymer. The weight average molecular weight of the thiophene polymer after washing with methanol was 3100.

Using the thiophene polymer after methanol washing, a coating liquid was prepared and a metallic gloss layer was formed in the same manner as in Example 1. The thickness of the metallic gloss layer was approximately 1.0 μm.

Example 15
Five parts of Al flakes (Toyo Aluminum Co., Ltd.) and eight parts of polyester resin (Vylon 200, Toyobo Co., Ltd.) were dispersed in toluene, applied to ordinary wood-free paper (C2 paper, Fuji Xerox Co., Ltd.), and then dried at a temperature of 60° C. for 15 minutes to form a metal layer having a thickness of about 5.0 μm. A metal layer having a thickness of about 5.0 μm was formed in the same manner as in Example 1, except that a metal layer having a metallic luster was formed on this metal layer. The thickness of the metal layer was about 1.0 μm.

<Performance evaluation>
Using an electrophotographic copier DocuCentre-V C6685 (Fuji Xerox Co., Ltd.) and toner cartridges “CT202676” (yellow), “CT202675” (magenta), “CT202674” (cyan), “CT202673” (black) and “CT203318” (gold) (all Fuji Xerox Co., Ltd.), the metallic gloss layers of each of the examples and comparative examples were copied onto ordinary high-quality paper (C2 paper, Fuji Xerox Co., Ltd.).

[Measurement of regular reflectance]
An integrating sphere was attached to a UV-2600 UV-visible spectrophotometer (Shimadzu Corporation), and the specular reflection spectra of the original and copy of the metallic gloss layer were measured using an aluminum-deposited mirror as a reference. The specular reflectance (%) at a wavelength of 600 nm is shown in Table 1.

[Measurement of diffuse reflectance]
An integrating sphere was attached to a UV-2600 UV-visible spectrophotometer (Shimadzu Corporation) and the diffuse reflectance spectra of the original and copy of the metallic gloss layer were measured using a barium sulfate white plate as a reference. The diffuse reflectance (%) at a wavelength of 600 nm is shown in Table 1.

[Glossiness]
The duplicates of the metallic gloss layer were visually observed, and the gloss was classified as follows.
G1: No gloss at all.
G2: Glossy depending on viewing angle.
G3: Glossy regardless of viewing angle.

In the examples, the difference in regular reflectance between the original and the copy was large. The color of the copy in the examples, when visually observed, was close to black.
In the comparative example, the copy reproduced the gloss of the original, and the color of the copy was gold to yellow .

10, 20 Recording medium 12, 22 Substrate 14, 24 Metallic gloss layer 23 Metal layer

Claims (10)

A substrate;
A metallic luster layer containing a thiophene polymer provided on the substrate,
the weight average molecular weight of the thiophene polymer contained in the metallic luster layer is 200 or more and 30,000 or less;
a total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer is 1 ppm or more and 1500 ppm or less with respect to the thiophene polymer,
The contents of Cu atoms, Mn atoms, Cr atoms and Ce atoms are each 0 ppm;
Recording medium. 2. The recording medium according to claim 1 , wherein the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in said metallic luster layer is 500 ppm or less with respect to said thiophene polymer. 3. The recording medium according to claim 1, wherein the weight average molecular weight of the thiophene polymer contained in the metallic luster layer is 500 or more and 20,000 or less. A substrate;
A metallic luster layer containing a thiophene polymer provided on the substrate,
the weight average molecular weight of the thiophene polymer contained in the metallic luster layer is 1,000 or more and 10,000 or less ,
the total content of Fe atoms, Cu atoms, Mn atoms, Cr atoms and Ce atoms in the metallic luster layer is 1 ppm or more and 100 ppm or less with respect to the thiophene polymer;
Recording medium. The recording medium according to any one of claims 1 to 4 , further comprising a metal layer containing a metal between the substrate and the metallic luster layer. 6. The recording medium according to claim 5, wherein the metal layer does not contain the thiophene polymer. 7. The recording medium according to claim 5 , wherein the metal layer contains at least one metal selected from the group consisting of Au, Ag, Cu and Al. 8. The recording medium according to claim 1, wherein the thiophene polymer comprises a polymer of at least one selected from the group consisting of alkoxythiophenes, alkylthiophenes, aminothiophenes, and hydroxythiophenes. the thiophene polymer contains at least a polymer in which an alkoxythiophene is polymerized,
The recording medium according to claim 8 , wherein the alkoxythiophene includes an alkoxythiophene having an alkoxy group having 1 to 6 carbon atoms. the thiophene polymer includes a polymer in which at least an alkylthiophene is polymerized,
10. The recording medium according to claim 8 , wherein the alkylthiophene includes an alkylthiophene having an alkyl group having 1 to 6 carbon atoms.