Near-infrared curable ink composition, near-infrared cured film, and method for producing near-infrared cured product

Abstract

Provided is a near-infrared curable ink composition comprising: a thermosetting resin or a thermoplastic resin, and near-infrared absorbing particles, wherein the near-infrared absorbing particles contain a near-infrared absorbing particle having a general formula of Cs x W 1‑y O 3‑z (0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46) indicates cesium tungsten oxide having an orthorhombic or hexagonal crystal structure.

Description

Technical Field

[0001] The present invention relates to a near-infrared curable ink composition, a near-infrared cured film, and a method for producing a near-infrared cured product. Background Art

[0002] In recent years, ultraviolet curing paints that are cured by ultraviolet light can be printed without heating, and therefore are widely known as environmentally friendly paints as described in Patent Documents 1 to 6, for example.

[0003] However, when using compositions that undergo free radical polymerization upon UV irradiation as UV-curable inks or coatings, the presence of oxygen hinders polymerization (curing). On the other hand, when using compositions that undergo cation polymerization upon UV irradiation, there is a problem of generating strong acid during polymerization.

[0004] Furthermore, to improve the light resistance of printed or coated surfaces of films obtained by applying UV-curable inks or coatings, UV absorbers are generally added to the UV-curable inks or coatings used as the raw materials for these printed or coated surfaces. However, the addition of UV absorbers to UV-curable inks or coatings poses the problem of hindering curing by UV irradiation.

[0005] In order to solve these problems, Patent Documents 7 and 8 propose near-infrared curing compositions that are cured by irradiation with near-infrared rays other than ultraviolet rays.

[0006] Furthermore, the applicant of the present application disclosed in Patent Documents 9 and 10 a near-infrared curable ink composition containing a composite tungsten oxide.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Laid-Open No. 7-100433

[0010] Patent Document 2: Japanese Patent Application Laid-Open No. 2001-146559

[0011] Patent Document 3: Japanese Patent Application Laid-Open No. 2009-057548

[0012] Patent Document 4: Japanese Patent Application Laid-Open No. 2012-140516

[0013] Patent Document 5: Japanese Patent Application Laid-Open No. 2000-037943

[0014] Patent Document 6: Japanese Patent Application Laid-Open No. 2004-18716

[0015] Patent Document 7: Japanese Patent Application Laid-Open No. 2008-214576

[0016] Patent Document 8: Japanese Patent Application Laid-Open No. 2015-131928

[0017] Patent Document 9: International Publication No. 2017 / 047736

[0018] Patent Document 10: International Publication No. 2019 / 054478

[0019] Non-patent literature

[0020] Non-patent document 1: K.Adachi and T.Asahi, "Activation of plasmons and polarons in solar control cesium tungsten bronze and reduced tungsten oxidenanoparticles," Journal of Material Research, Vol. 27, 965-970 (2012)

[0021] Non-patent document 2: S. Yoshio and K. Adachi, "Polarons in reduced cesiumtungsten bronzes studied using the DFT+U method," Materials Research Express, Vol. 6, 026548 (2019)

[0022] Non-patent document 3: K.Machida, M.Okada, and K.Adachi, "Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronzenanocrystals," Journal of Applied Physics, Vol.125,103103(2019)

[0023] Non-patent document 4: SFSolodovnikov, NVIvannikova, ZASolodovnikova, ESZolotova, "Synthesis and X-ray diffraction study of potassium, rubidium, andcesium polytungstates with defect pyrochlore and hexagonal tungsten bronzestructures," Inorganic Materials, Vol. 34, 845-853 (1998)

[0024] Non-patent document 5: M. Okada, K. Ono, S. Yoshio, H. Fukuyama and K. Adachi, "Oxygenvacancies and pseudo Jahn-Teller destabilization in cesium-doped hexagonaltungsten bronzes," Journal of American Ceramic Society, Vol. 102, 5386-5400 (2019)

[0025] Non-Patent Document 6: S. Yoshio, M. Okada, K. Adachi, “Destabilization of PseudoJahn-Teller Distortion in Cesium-doped Hexagonal Tungsten Bronzes”, J. Appl. Phys., vol. 124, 063109-1-8 (2018) Summary of the Invention

[0026] Problems to be solved by the invention

[0027] However, according to the studies conducted by the present inventors, both of the near-infrared curable compositions described in Patent Document 7 and Patent Document 8 have the problem of insufficient near-infrared absorption properties.

[0028] In contrast, the composite tungsten oxide microparticles contained in the near-infrared-curable ink compositions disclosed in Patent Documents 9 and 10 have high transmittance and low absorptivity for visible light, but low transmittance and high absorptivity for light in the near-infrared region. Therefore, near-infrared-curable ink compositions containing these composite tungsten oxide microparticles exhibit excellent near-infrared absorption properties.

[0029] However, composite tungsten oxide microparticles preferentially absorb long-wavelength light in the visible spectrum, specifically red light. This results in a bluish coloration, which intensifies as the amount of these microparticles added increases. Consequently, cured films containing composite tungsten oxide microparticles as near-infrared absorbing components exhibit a bluish coloration, making it difficult to color with yellow or other light colors other than blue, which complement blue, by adding other pigments.

[0030] Therefore, an object of one aspect of the present invention is to provide a near-infrared curable ink composition that contains near-infrared absorbing particles containing a composite tungsten oxide and can have a neutral color tone depending on the curing state.

[0031] Methods for solving problems

[0032] One aspect of the present invention provides a near-infrared curable ink composition comprising a thermosetting resin or a thermoplastic resin and near-infrared absorbing particles.

[0033] The above-mentioned near infrared absorbing particles contain Cs x W 1-y O 3-z (0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46) indicates cesium tungsten oxide having an orthorhombic or hexagonal crystal structure.

[0034] Effects of the Invention

[0035] One aspect of the present invention provides a near-infrared curable ink composition comprising near-infrared absorbing particles containing a composite tungsten oxide, which can have a neutral color tone depending on the curing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1A This is an illustration of the crystal structure of cesium tungsten oxide.

[0037] Figure 1B This is an illustration of the crystal structure of cesium tungsten oxide.

[0038] Figure 2A This is the energy band structure of cesium tungsten oxide.

[0039] Figure 2B This is the energy band structure of cesium tungsten oxide.

[0040] Figure 2C This is the energy band structure of cesium tungsten oxide.

[0041] Figure 2D This is the energy band structure of cesium tungsten oxide.

[0042] Figure 3A is the dielectric function of cesium tungsten oxide.

[0043] Figure 3B is the dielectric function of cesium tungsten oxide.

[0044] Figure 4 This is an electron diffraction image taken along the c-axis direction of powder A′ obtained in Experimental Example 1-1.

[0045] Figure 5

[001] of the pseudo-hexagonal particles of powder A obtained in Experimental Example 1-1 HEX Electron diffraction image of the crystal zone axis.

[0046] Figure 6 This is a STEM-HAADF image observed from the

[221] zone axis of the pseudo-hexagonal particles of powder A obtained in Experimental Example 1-1.

[0047] Figure 7

[001] of the pseudo-hexagonal particles of powder B obtained in Experimental Example 1-2 HEX Electron diffraction image of the crystal zone axis.

[0048] Figure 8

[001] of the pseudo-hexagonal particles of powder C obtained in Experimental Example 1-3 HEX Electron diffraction image of the crystal zone axis. DETAILED DESCRIPTION

[0049] Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. However, the present invention is not limited to the following embodiments, and various modifications and substitutions can be made to the following embodiments without departing from the scope of the present invention.

[0050] [Near infrared curable ink composition]

[0051] The near-infrared curable ink composition of this embodiment will be described in the following order: [1] near-infrared absorbing particles and a method for producing near-infrared absorbing particles; [2] a dispersion of near-infrared absorbing particles; [3] a near-infrared curable ink composition; and [4] a method for producing a near-infrared curable ink composition.

[0052] [1] Near-infrared absorbing particles and method for producing near-infrared absorbing particles

[0053] (Near-infrared absorbing particles)

[0054] Conventionally, the transmission color of cesium-doped hexagonal tungsten bronze particles used as near-infrared absorbing particles is determined by the imaginary part of their dielectric function (ε2) (ε2 obtained experimentally is described in Non-Patent Document 1) and the band structure (Non-Patent Document 2).

[0055] In the energy region of visible light (1.6eV to 3.3eV), the band gap of hexagonal tungsten bronze (hereinafter referred to as Cs-HTB) with the addition of cesium is sufficiently large. In addition, the electron migration between the dd orbits of tungsten is prohibited by Fermi's golden rule, so the probability of electron migration becomes smaller and ε2 takes a small value. ε2 represents the absorption of photons brought by electrons, so when ε2 is small at visible wavelengths, visible light transmittance is generated. However, near the shortest blue wavelength in the visible light region, there is absorption caused by inter-band migration, and near the longest red wavelength, there is local surface plasmon resonance (LSPR) absorption and polarographic electron migration absorption (non-patent document 3). Therefore, they are respectively subject to light transmittance restrictions.

[0056] As mentioned above, Cs-HTB has a sufficiently large band gap, so the interband transition reaches energy levels above blue wavelengths, resulting in high blue transmittance. Conversely, Cs-HTB has more conduction electrons in the red, resulting in stronger LSPR and polarographic absorption. Simultaneously, the absorption wavelength shifts toward the red, reducing transmittance. Consequently, the transmission color of films with dispersed Cs-HTB particles appears blue.

[0057] That is, in order to neutralize the blue transmission color of Cs-HTB, it is sufficient to enhance the absorption on the blue side and enhance the transmission on the red side. Therefore, it is preferred to move the absorption position of inter-band migration to low energy, and also weaken the LSPR absorption and polarographic absorption to move to the low energy side.

[0058] In order to weaken LSPR absorption and polarographic absorption, it is effective to reduce the amount of free electrons and bound electrons contained in the material.

[0059] The increase in the absorption on the blue side is achieved by using a material with a different energy band structure having a low energy band gap. In addition, the transmission on the red side can increase or decrease the cesium ions (Cs) that are the source of free electrons and bound electrons. + ), oxygen pores (V O ) to control the amount.

[0060] Based on the above findings, the inventors of the present invention studied various cesium tungsten oxides containing oxides of cesium (Cs) and tungsten (W). They found that when near-infrared-absorbing particles containing cesium tungsten oxide are prepared by reducing a crystalline powder of nCs2O·mWO3 (n and m are integers, 3.6 ≤ m / n ≤ 9.0), a cesium tungsten oxide precursor containing Cs and W, the blue hue of the dispersed near-infrared-absorbing particles, such as a permeable membrane, and the near-infrared-absorbing particle dispersion liquid, is reduced and becomes neutral. Furthermore, they discovered that near-infrared-curable ink compositions containing these near-infrared-absorbing particles, and their cured products, can exhibit a more neutral hue.

[0061] It is believed that the near-infrared absorbing particles are derived from a compound having a narrower band gap than hexagonal Cs-HTB and a lower blue transmittance, and that the compound is reduced to gradually increase V O , gradually increase LSPR absorption and polarographic absorption within the allowable range, optimize the red transmittance, and thus neutralize the color tone.

[0062] In the cesium tungsten oxide precursor nCs2O·mWO3 containing Cs, the charges of Cs and W, which are positive elements, are neutralized by O, making it a non-conductor. 22 、Cs6W 20 O 63 、Cs2W6O 19 、Cs4W 11 O 35 、Cs6W 11 O 36 、Cs2W3O 10 In compounds arranged on the WO3-Cs2O line, the valence is balanced, so the Fermi energy E F It exists between the valence band and the conduction band, becoming a non-conductor. When the Cs / W ratio (molar ratio) is 0.2 or higher, the basic skeleton composed of WO octahedrons becomes a hexagonal symmetrical structure with large hexagonal voids to absorb Cs with a large ionic radius. Alternatively, the atomic arrangement of hexagonal or cubic crystals (pyrochrome structure) with large hexagonal voids contains W defects (tungsten defects), reducing the symmetry to orthorhombic or monoclinic crystal structures.

[0063] For example, in the model of Solodovnikov 1998 (Non-Patent Document 4), in 2Cs2O·11WO3, within the hexagonal arrangement of WO octahedra, similar to hexagonal tungsten bronze, W and O deficient planes are inserted into the hexagonal (110) plane (=orthorhombic (010) plane) at a spacing of b / 8 of the orthorhombic unit cell, resulting in an orthorhombic structure as a whole. These cesium tungsten oxide precursors, nCs2O·mWO3 (n and m are integers, 3.6 ≤ m / n ≤ 9.0), have narrower band gaps than Cs-HTB, resulting in lower blue transmittance. However, it is known that when these are heated and reduced, the overall structure gradually changes to the hexagonal structure of tungsten bronze. During this process, the band structure changes, the band gap widens, and the blue absorption weakens, resulting in stronger blue transmittance. Furthermore, at this time, as reduction proceeds, electrons are gradually injected into the conduction band, thereby becoming a conductor, and the band gap gradually widens due to the Burstein-Moss effect, thereby further enhancing blue transmittance.

[0064] When the orthorhombic crystal is reduced to hexagonal crystal by heating, the surface defects containing W defects in the orthorhombic crystal gradually disappear, forming a hexagonal crystal skeleton of WO octahedron. The surface defects containing W defects are in (010)ORTH The surface exists, which is occupied by the hexagonal prism face {100} HEX , that is [(100) HEX 、(010) HEX 、(110) HEX ] inherited, and thus gradually became {100} together with the heating reduction HEX The hexagonal crystal contains defects. At this time, the hexagonal crystal has defects in {100} HEX The surface contains defects, thus deviating from the complete hexagonal symmetry, and is in a state called pseudo-hexagonal crystal. In this way, while heating and reducing, the crystal structure changes from orthorhombic to pseudo-hexagonal, and further to hexagonal. At this time, the orthorhombic crystal contains the (010) containing W defects. ORTH The surface defects of the surface are {100} HEX The surface defects of the surface are inherited and gradually reduced and eventually disappear.

[0065] As the crystal structure changes during heating and reduction, the electronic structure also changes. The disappearance of W defects leads to the injection of a large amount of electrons into the material. In the orthorhombic crystal, the outer shell electrons of Cs are spent on the neutralization of O, and the charge becomes neutral as a whole. However, when the W defects are reduced and it becomes a pseudo-hexagonal crystal, each W atom has 6 outer shell electrons spent on the neutralization of O, and thus the outer shell electrons of Cs enter the W-5d orbit at the bottom of the conduction band and become free electrons. The free electrons bring about the absorption of near-infrared rays through LSPR absorption. On the other hand, heating and reduction have the effect of generating V at the same time. O The role of V O The generation of V is performed at random sites. O When the W atoms on both sides have excess charge, the W atoms will be affected by the W 5+ Bound local electrons (non-patent literature 2). The local electrons transition to the vacancy at the top of the conduction band, producing polarographic absorption, but a portion is excited to the free electron orbit, producing LSPR absorption (non-patent literature 3). The absorption of these free electrons and bound electrons is due to the peak wavelength being near-infrared, so the footing of absorption is affected by the red wavelength, thereby reducing the red transmittance. The more the amount of free electrons and bound electrons, that is, the more the degree of reduction increases, the more LSPR absorption and polarographic absorption wavelength move to high wavelengths, and the absorption amount is also greater, so the red transmittance is reduced.

[0066] Therefore, by reducing the crystalline powder of the cesium tungsten oxide precursor nCs2O·mWO3 (n and m are integers, 3.6≤m / n≤9.0) and adjusting the degree of reduction at this time, the blue transmission color can be neutralized.

[0067] The near-infrared absorbing particles of the present embodiment described above can be produced by heating a crystalline powder of a cesium tungsten oxide precursor, nCs2O·mWO3, containing Cs and W, in a reducing atmosphere at a temperature of 650°C to 950°C. In the formula of the cesium tungsten oxide, n and m are integers, preferably satisfying 3.6≤m / n≤9.0.

[0068] That is, as near-infrared absorbing particles, particles can be used that are obtained by heating and reducing a crystalline powder of a cesium tungsten oxide precursor nCs2O·mWO3 (n and m are integers, 3.6≤m / n≤9.0) containing cesium and tungsten in a reducing gas atmosphere at a temperature of 650°C to 950°C.

[0069] In order to convert all or part of the hexagonal tungsten bronze into hexagonal tungsten bronze by heating and reduction, the m / n value must be within the range of 3.6 ≤ m / n ≤ 9.0 as mentioned above. If it is less than 3.6, after heating and reduction, it will form a cubic chromium phase, which has strong coloration and does not produce near-infrared absorption. In addition, if it is greater than 9.0, after heating and reduction, the hexagonal tungsten bronze and tungsten trioxide phase will separate, and the near-infrared absorption effect will be significantly reduced. The cesium tungsten oxide precursor is more preferably Cs4W with m / n = 5.5. 11 O 35 That is, as the near infrared absorbing particles, it is more preferable to use as the main phase a particle containing Cs4W 11 O 35 The particles are obtained by heating and reducing the precursor of cesium tungsten oxide in a reducing gas atmosphere at a temperature between 650°C and 950°C. 11 O 35 The near-infrared absorbing particles obtained by high-temperature reduction are dispersed to achieve a high near-infrared absorbing effect while having a blue-suppressed transmission color. The main phase herein refers to the phase containing the most by mass.

[0070] As described above, the heating temperature for reducing cesium tungsten oxide is preferably between 650°C and 950°C. A temperature of 650°C or higher allows for a sufficient structural transition from orthorhombic to hexagonal, enhancing near-infrared absorption. Furthermore, a temperature of 950°C or lower allows for a moderate rate of crystal structure transition, making it easier to maintain an appropriate crystalline and electronic state. Furthermore, heating temperatures above 950°C may result in excessive reduction, potentially leading to the formation of lower oxides such as W metal and WO2, which is undesirable from this perspective.

[0071] Furthermore, the near infrared absorbing particles of this embodiment may contain Cs x W 1-y O 3-z(0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46) indicates cesium tungsten oxide having an orthorhombic or hexagonal crystal structure. Furthermore, the near-infrared absorbing particles may contain both orthorhombic and hexagonal cesium tungsten oxides.

[0072] The cesium tungsten oxide contained in the near infrared absorbing particles satisfies the above general formula, thereby o When the degree of the near-infrared curable ink composition is dispersed within an appropriate range, the solar transmittance can be suppressed, and the transmitted color of the cured product can be made more neutral.

[0073] The near-infrared absorbing particles can also be formed from cesium tungsten oxide, which is the composite tungsten oxide. However, even in this case, the particles may contain unavoidable impurities introduced during the production process.

[0074] Conventional tungsten bronzes for near-infrared absorption have a hexagonal structure. Meanwhile, the composite tungsten oxide contained in the near-infrared absorbing particles of this embodiment can have an orthorhombic or hexagonal crystal structure. Furthermore, the hexagonal structure herein includes a pseudo-hexagonal structure.

[0075] The cesium tungsten oxide as a composite tungsten oxide contained in the near-infrared absorbing particles preferably has linear or planar defects on one or more surfaces selected from the (010) surface of the orthorhombic crystal, the {100} surface as the prism surface of the hexagonal crystal, and the (001) surface as the bottom surface of the hexagonal crystal. The above-mentioned defects include stacking errors based on the mutual offset of the surfaces, the arrangement of Cs atoms and W atoms in the surface, and the disorder of the atomic positions, and therefore are often accompanied by stripes in the electron beam diffraction spots. The {100} surface as the prism surface of the hexagonal crystal refers to the (100) surface, the (010) surface, and the (110) surface. The defects involved in the composite tungsten oxide, that is, the lattice defects are accompanied by at least W defects, specifically, a part of the W is missing, and the W defects lead to the loss of electrons in the crystal. As mentioned above, this is one of the essential reasons and acts on the neutralization of the blue tone.

[0076] Cesium tungsten oxide has defects, and these defects may include tungsten defects as described above.

[0077] In addition, a portion of the O in the WO octahedron, i.e., the WO6 octahedron, which constitutes the orthorhombic or hexagonal crystal structure of the basic structure of cesium tungsten oxide may further have defects. The defects involved may be random defects. It is known that the pore V of the octahedral oxygen O As mentioned above, it can be randomly introduced into the known hexagonal tungsten bronze Cs 0.32 WO 3―yIn the general formula Cs representing cesium tungsten oxide contained in the near-infrared absorbing particles of this embodiment, the maximum of 15% of the total lattice points is covered (Non-Patent Document 5). x W 1―y O 3―z The maximum amount of V that can be included is z = 0.46. O That is, z can be 0.46 or less.

[0078] The lattice constant of cesium tungsten oxide corresponds to the amount of defects in the crystal lattice, or the composition and crystallinity. The a-axis value is observed to be uneven with respect to these variables, while the c-axis value corresponds relatively well to the amount of lattice defects or optical properties. As a result, the cesium tungsten oxide contained in the near-infrared absorbing particles of this embodiment preferably has a c-axis length of 1000 nm in terms of hexagonal conversion. above By setting the c-axis length of the cesium tungsten oxide in the above range, the near-infrared absorption effect is substantially enhanced, and the visible light transmittance is particularly improved. Furthermore, in the case of hexagonal cesium tungsten oxide, conversion is not necessary; the c-axis length of the hexagonal crystal corresponds to the above hexagonal c-axis length.

[0079] The cesium tungsten oxide contained in the near infrared absorbing particles of this embodiment is often identified as a mixed phase of orthorhombic and hexagonal crystals when the diffraction pattern of the sample is measured by X-ray powder diffraction. 11 O 35 When the raw material was reduced, it was identified as orthorhombic Cs4W 11 O 35 With hexagonal Cs 0.32 Mixed phase of WO3. In this case, the lattice constants of each phase can be obtained by using Rietveld analysis and the like, and they can be converted into hexagonal conversion values. As already explained, the orthorhombic crystal is a hexagonal crystal with a lattice defect plane, so the lattice constant of the orthorhombic crystal can be converted into the lattice constant of the hexagonal crystal by an appropriate lattice correspondence model. If the correspondence of the lattice changes between the orthorhombic crystal and the hexagonal crystal is assumed to be the model of Solodovnikov 1998 (non-patent document 4), then 4a is extracted from the geometric relationship with the model. orth 2 +b orth 2 =64a hex 2 =64b hex 2 , c orth =c hex By using these formulas, the lattice constants of all hexagonal crystals can be calculated. orth 、b orth 、corth Refers to the length of the a-axis, b-axis, and c-axis of the orthorhombic crystal. hex 、b hex 、c hex It refers to the length of the a-axis, b-axis, and c-axis of the hexagonal crystal.

[0080] The cesium tungsten oxide contained in the near-infrared absorbing particles of this embodiment may have a portion of the Cs replaced by an additive element. In this case, the additive element is preferably one or more selected from the group consisting of Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0081] The aforementioned additional elements have electron-donating properties and are located at the Cs site, thereby assisting in the electron donation to the conduction band of the WO octahedral framework.

[0082] The average particle size of the near-infrared absorbing particles of the present embodiment is not particularly limited, and is preferably between 0.1 nm and 200 nm. This is because, by making the average particle size of the near-infrared absorbing particles less than 200 nm, the local presence of surface plasmon resonance is more significantly expressed, thereby being able to particularly improve the near-infrared absorption characteristics, that is, being able to particularly suppress the solar transmittance. In addition, this is because by making the average particle size of the near-infrared absorbing particles more than 0.1 nm, it is possible to easily manufacture industrially. In addition, the particle size is closely related to the color of the near-infrared absorbing particle dispersion as a dispersed permeable film for dispersing the near-infrared absorbing particles, and within the particle size range dominated by Mie scattering, the smaller the particle size, the more the scattering of the short wavelength in the visible light region is reduced. Therefore, if the particle size is increased, there is a special effect of suppressing blue hues. If it exceeds 100 nm, it becomes the size of the haze of the film with light scattering that cannot be ignored. If it exceeds 200 nm, in addition to the rise in the haze of the film, sometimes the generation of surface plasmons is suppressed and the LSPR absorption becomes excessively smaller.

[0083] Here, the average particle size of the near-infrared absorbing particles can be known from the average value of the particle sizes of a plurality of near-infrared absorbing particles measured using a transmission electron microscope image or the dispersed particle size measured using a particle size analyzer using a dynamic light scattering method of the dispersion.

[0084] Furthermore, particularly for applications where transparency in the visible light range is important, such as when it is desired to particularly minimize the effect on the color tone of a near-infrared-curable ink composition or its cured product, it is further preferable to consider the reduction in scattering achieved by the near-infrared-absorbing particles. When this reduction in scattering is important, the average particle size of the near-infrared-absorbing particles is particularly preferably 30 nm or less.

[0085] Furthermore, the near-infrared absorbing particles may be surface-treated for purposes such as surface protection, durability improvement, oxidation prevention, and water resistance improvement. The specific content of the surface treatment is not particularly limited. For example, the near-infrared absorbing particles of this embodiment may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. Examples of the compound containing one or more atoms (elements) selected from Si, Ti, Zr, Al, and Zn include one or more selected from oxides, nitrides, and carbides.

[0086] Here, the band structures of cesium tungsten oxide and a cesium tungsten oxide precursor are described.

[0087] As described above, it is shown that if nCs2O·mWO3 (n, m are integers, 3.6≤m / n≤9.0) is reduced at high temperature, a sunlight shielding material with a transmittance color closer to neutral can be obtained. It is believed that during high temperature reduction, hexagonal crystallization including the disappearance of W defects and V O The generation of electrons into the conduction band becomes the source of near-infrared absorption, and such electronic structure changes are supported by first-principles calculations.

[0088] Figure 1A Cs4W 11 O 35 In addition, Figure 1B Indicated as Cs 0.33 WO3 Cs4W 12 O 36 crystal structure. Figure 1A 、 Figure 1B In the figure, cesium 11 and oxygen 12 are shown. In addition, atoms of the same type have the same shading. Tungsten is arranged in an octahedron formed by oxygen 12, so Figure 1A 、 Figure 1B Not displayed in . Figure 1B In order to be able to 0.33 WO3 and Figure 1A Cs4W 11 O 35 The contrast method uses the orthorhombic crystal to re-axis the structure.

[0089] Figure 1A Cs4W 11 O 35 The structure of Figure 1B Cs4W 12 O 36 In the crystal structure, W and O are regularly missing.

[0090] The above Figure 1A 、 Figure 1BThe band structures of the crystal structure of cesium tungsten oxide are shown in Figure 2A 、 Figure 2B In addition, Figure 1B Cs4W 12 O 36 As a benchmark, the Cs4W with 1 W missing 11 O 36 The band structure of the b-axis is 1.5 times the unit, missing 1 W Cs6W 17 O 54 The band structures of Figure 2C 、 Figure 2D .

[0091] Figure 2A 、 Figure 2B Cs4W shown 11 O 35 The band structure of Cs4W 12 O 36 The band structure is similar, but the Fermi energy (E F ) is located in the band gap and the latter is located below the conduction band. 11 O 35 As an insulator, Cs4W 12 O 36 It is a conductor. 11 O 35 In the case of Cs4W 12 O 36 As a benchmark, there is one missing W and one missing O in the unit cell. W and O satisfy Cs4W 12 O 36 In the figure, a hexagonal WO3 network is formed, and it is explained that Cs electrons are injected into the W-5d orbit to become a conductor (Non-Patent Document 6).

[0092] Figure 2C Cs4W 11 O 36 For Figure 2B Cs4W 12 O 36 Minus 1 W structure.

[0093] Figure 2D Cs6W 17 O 54 , that is, 3Cs2O·17WO3 is from Figure 2B Cs4W 12 O 36 , namely Cs6W 18 O 54 Let's look at a structure that reduces 1 W while maintaining charge neutrality.

[0094] The amount of W defect is based on Figure 2A 、 Figure 2D 、 Figure 2B The order of decrease, E F As the number of electrons increases toward the bottom of the conduction band, W electrons are injected into the W-5d orbit and the number of conduction electrons increases, suggesting that near-infrared absorption increases.

[0095] Reported from Cs4W 12 O 36 In the case of the missing O, the calculation example described in detail shows that the localized orbitals are introduced at the bottom of the conduction band, and the number of free electrons and localized electrons increases significantly (Non-Patent Document 2).

[0096] It is believed that the experimentally obtained pseudo-hexagonal crystal (an intermediate structure in the phase transition between orthorhombic and hexagonal) is an electronic state in which the above elements are mixed. That is, along with reduction, the hexagonal crystallization including the disappearance of W defects and the V O The generation of electrons in the conduction band little by little, the Fermi energy E F rising from the band gap toward the lower part of the conduction band.

[0097] Based on these band structures, Figure 3A 、 Figure 3B Displays the results of the dielectric function calculation including the Drude term. Figure 3B The dielectric function ε1 is shown as ε1 = 0, and the shielded plasma frequency (Ω SP ) with Cs4W 11 O 35 、Cs6W 17 O 54 、Cs4W 12 O 36 、Cs4W 12 O 35 In this order, it is expected that near-infrared absorption increases, and this tendency is consistent with the observation results.

[0098] Depend on Figure 3A The dielectric function ε2 graph shown in the figure shows that ε2 in the visible region is generally small for cesium tungsten oxide. In the 3.3 eV blue region shown by the dotted line 31, the band gap of Cs4W is narrow, which is defined by the inter-band transition. 11 O 35 、Cs6W 17 O 54 On the other hand, in the red region of 1.6 eV shown by the dotted line 32, the absorption of Cs4W is enhanced by the influence of the surface plasmon absorption. 12 O 35 The absorption of red light is expected to be SPThe reason why the blue color of the cesium tungsten oxide contained in the near infrared absorbing particles suitable for use in the near infrared curable ink composition of this embodiment is reduced compared to the cesium tungsten oxide used in the past is believed to be that nCs2O·mWO3 (3.6≤m / n≤9.0) with W and O defects is used as a raw material, thereby containing Cs with W defects. 0.33 W 1-y O 3―z The formation of a phase increases absorption on the high-energy side. By adjusting the high-temperature reduction of nCs2O·mWO3 (3.6 ≤ m / n ≤ 9.0), the band gap and the amount of electrons injected into the conduction band can be adjusted, thereby adjusting the blue hue. Furthermore, it was confirmed that the near-infrared absorption effect is maintained at a relatively high level during this process.

[0099] (Method for producing near-infrared absorbing particles)

[0100] The method for producing the near-infrared absorbing particles of this embodiment is not particularly limited, and any method that can produce near-infrared absorbing particles satisfying the aforementioned characteristics can be used without particular limitation. Here, a configuration example of a method for producing near-infrared absorbing particles is described.

[0101] The method for producing the near-infrared absorbing particles according to the present embodiment can include, for example, the following steps.

[0102] A cesium tungsten oxide precursor synthesis step is to synthesize a cesium tungsten oxide precursor containing cesium tungstate.

[0103] The cesium tungsten oxide precursor is heated and reduced in a reducing gas atmosphere at 650° C. to 950° C.

[0104] Hereinafter, each step will be described.

[0105] (1) Cesium tungsten oxide precursor synthesis process

[0106] In the cesium tungsten oxide precursor synthesis step, tungstate containing cesium, that is, a cesium tungstate precursor, can be synthesized. If the cesium tungsten oxide precursor has already been synthesized, the method for producing near-infrared absorbing particles of this embodiment can also start with the heating reduction step.

[0107] In addition, the cesium tungstate oxide precursor is preferably a crystalline powder of nCs2O·mWO3 (n and m are integers, 3.6≤m / n≤9.0). As the cesium tungstate oxide precursor, the stable cesium tungstate is more preferable. Examples of the stable cesium tungstate include Cs4W 11 O 35 、Cs2W6O 19 、Cs6W 20 O63 、Cs2W7O 22 、Cs6W 11 O 36 The cesium tungsten oxide precursor is particularly preferably a main phase containing Cs4W 11 O 35 phase cesium tungsten oxide precursor.

[0108] These cesium tungstates can be prepared, for example, by calcining a raw material powder mixture containing cesium and tungsten in air at a temperature of 700° C. to 1000° C. The production method of cesium tungstate is not limited to the above-mentioned method, and other methods such as a sol-gel method and a coordination compound polymerization method can also be used.

[0109] Furthermore, as the starting material, cesium tungstate used may be non-equilibrium tungstate obtained by gas phase synthesis, etc. This includes powders obtained by a thermal plasma method, powders obtained by electron beam dissolution, and the like.

[0110] (2) Heating reduction process

[0111] The cesium tungsten oxide precursor as the starting material, specifically, for example, cesium tungstate having one or more crystal structures selected from orthorhombic, monoclinic, and pseudohexagonal structures, can be subjected to the heat reduction step.

[0112] In the heat reduction step, the cesium tungsten oxide precursor can be heated and reduced in a reducing gas atmosphere at 650° C. to 950° C. By performing the heat reduction step, near-infrared absorbing particles containing cesium tungsten oxide having a desired composition can be obtained.

[0113] When performing a heat reduction treatment, it is preferably carried out under a stream of a reducing gas. The reducing gas may be a mixed gas containing a reducing gas such as hydrogen and one or more inert gases selected from nitrogen, argon, etc. Furthermore, heating under a steam atmosphere, a vacuum atmosphere, or other mild heating and reducing conditions may be used in combination.

[0114] The method for producing the near-infrared-absorbing particles of this embodiment is not particularly limited to the aforementioned form. Various methods capable of achieving a predetermined microstructure including defects can be used as methods for producing the near-infrared-absorbing particles. Examples of methods for producing the near-infrared-absorbing particles include methods of reducing tungstates obtained by solid-phase, liquid-phase, or vapor-phase methods, and methods of reducing WO3 in a molten alkali halide.

[0115] The method for producing near-infrared absorbing particles may further include an arbitrary step.

[0116] (3) Crushing process

[0117] As described above, the near-infrared absorbing particles are preferably miniaturized to form particles. Therefore, the method for producing the near-infrared absorbing particles may include a pulverization step of pulverizing the powder obtained in the heat-reduction step.

[0118] The specific means of pulverization and micronization are not particularly limited, and various mechanical pulverization methods can be used. As a mechanical pulverization method, a dry pulverization method using a jet mill or the like can be employed. Alternatively, mechanical pulverization can be performed in a solvent during the process of obtaining the near-infrared absorbing particle dispersion described later. In this case, the pulverization step disperses the near-infrared absorbing particles in the liquid medium, and thus can also be referred to as a pulverization and dispersion step.

[0119] (4) Coating process

[0120] As described above, the surface of the near-infrared absorbing particles may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. Therefore, the method for producing near-infrared absorbing particles may further include, for example, a coating step of coating the near-infrared absorbing particles with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn.

[0121] In the coating step, the specific conditions for coating the near-infrared absorbing particles are not particularly limited. For example, an alkoxide containing one or more atoms selected from the aforementioned atomic groups (metal groups) can be added to the modified near-infrared absorbing particles to form a coating on the surface of the near-infrared absorbing particles.

[0122] [2]Near-infrared absorbing particle dispersion

[0123] Next, a configuration example of the near-infrared absorbing particle dispersion according to the present embodiment will be described.

[0124] The near-infrared absorbing particle dispersion of this embodiment can also be used, for example, to produce a near-infrared curable ink composition described later.

[0125] The near-infrared-absorbing particle dispersion of this embodiment can include the aforementioned near-infrared-absorbing particles and one or more liquid media selected from the group consisting of water, an organic solvent, oil, a liquid resin, and a liquid plasticizer. The near-infrared-absorbing particle dispersion preferably has a configuration in which the near-infrared-absorbing particles are dispersed in the liquid medium.

[0126] As the liquid medium, as described above, one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used.

[0127] As the organic solvent, various organic solvents can be selected, such as alcohols, ketones, hydrocarbons, and glycols. Specifically, one or more organic solvents can be selected from the group consisting of alcohol solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropyl alcohol, butanol, amyl alcohol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as 3-methyl-methoxy-propionate and butyl acetate; glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, and propylene glycol ethyl ether acetate; amides such as formamide, N-methylformamide, dimethylformamide, dimethylazoamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as vinyl chloride and chlorobenzene.

[0128] However, among these, organic solvents with low polarity are preferred, and particularly more preferred are isopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate, etc. These organic solvents can be used alone or in combination of two or more.

[0129] As the oil and fat, for example, one or more selected from drying oils such as linseed oil, sunflower oil, and tung oil, semi-drying oils such as sesame oil, cottonseed oil, rapeseed oil, soybean oil, and rice bran oil, non-drying oils such as olive oil, coconut oil, palm oil, and dehydrated castor oil, fatty acid monoesters obtained by directly reacting fatty acids of vegetable oils with monohydric alcohols, ethers, and petroleum solvents such as Isopar (registered trademark) E, EXXSOL (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, and D130 (all manufactured by ExxonMobil) can be used.

[0130] As the liquid resin, for example, one or more selected from liquid acrylic resins, liquid epoxy resins, liquid polyester resins, liquid urethane resins, and the like can be used.

[0131] As the liquid plasticizer, for example, liquid plasticizers for plastics can be used.

[0132] The components contained in the near-infrared absorbing particle dispersion are not limited to the aforementioned near-infrared absorbing particles and liquid medium. The near-infrared absorbing particle dispersion may further contain arbitrary components as needed.

[0133] For example, an acid or a base may be added to the near-infrared absorbing particle dispersion as needed to adjust the pH of the dispersion.

[0134] Furthermore, in order to further improve the dispersion stability of the near-infrared absorbing particles and prevent the coarsening of the dispersed particles due to reaggregation, various surfactants, coupling agents, etc. may be added as dispersants to the near-infrared absorbing particle dispersion.

[0135] Dispersants such as surfactants and coupling agents can be selected according to the intended use. Preferably, the dispersant has one or more functional groups selected from amine-containing groups, hydroxyl groups, carboxyl groups, and epoxy groups. These functional groups have the ability to adsorb to the surface of the near-infrared absorbing particles and prevent aggregation. For example, even in infrared shielding films such as near-infrared cured films formed using near-infrared absorbing particles, they have the effect of uniformly dispersing the near-infrared absorbing particles. Furthermore, polymeric dispersants having one or more of the above functional groups (functional group groups) in the molecule are desirable.

[0136] Examples of commercially available dispersants that can be suitably used include Solspers (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, and 250 (manufactured by Japan Lubrizol Co., Ltd.), EFKA (registered trademark) 4008, 4009, 4010, 4015, 4046, 4047, 4060, 4080, 7462, 4020, 4050, 4055, 4400, 4401, 4402, 4403, 4300, 4320, 4330, 4340, 6220, 6225, 6700, 6780, 6782, and 8503 (manufactured by EFKA). ADDITIVES), Ajispur (registered trademark) PA111, PB821, PB822, PN411, FameEX L-12 (Ajinomoto FINE TECHNO Co., Ltd.), DisperBYK (registered trademark) 101, 102, 106, 108, 111, 116, 130, 140, 142, 145, 161, 162, 163, 164, 166, 167, 168, 170, 171, 174, 180, 182, 192, 193, 2000, 2001, 2020, 2025, 2050, 2070, 2155, 2164, 220S, 300, 306, 320, 322, 325, 330, 340, 350, 377, 378, 380N, 410, 425, 430 (BYK Japan Co., Ltd.), DISPARLON (registered trademark) 1751N, 1831, 1850, 1860, 1934, DA-400N, DA-703-50, DA-725, DA-705, DA-7301, DN-900, NS-5210, NVI-8514L (manufactured by Kusumoto Chemicals Co., Ltd.), ARUFON (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), etc., one or more

[0137] The method for dispersing the near-infrared-absorbing particles in the liquid medium is not particularly limited as long as the near-infrared-absorbing particles can be dispersed in the liquid medium. In this case, the near-infrared-absorbing particles are preferably dispersed so that the average particle size is 200 nm or less, and more preferably are dispersed so that the average particle size is 0.1 nm or more and 200 nm or less.

[0138] As a dispersion treatment method for near-infrared absorbing particles in a liquid medium, for example, a dispersion treatment method using devices such as a bead mill, a ball mill, a sand mill, a paint shaker, and an ultrasonic homogenizer can be cited. Among them, it is preferred from the viewpoint of shortening the time required to crush and disperse the particles into a desired average particle size using a medium stirred mill such as a bead mill, a ball mill, a sand mill, and a paint shaker using a medium (beads, balls, Ottawa sand). By using a pulverization-dispersion treatment of a medium stirred mill, it is possible to simultaneously disperse the near-infrared absorbing particles in a liquid medium while also performing micronization caused by collisions between the near-infrared absorbing particles and collisions of the medium with the near-infrared absorbing particles, thereby further micronizing the near-infrared absorbing particles and dispersing them. That is, pulverization-dispersion treatment is performed.

[0139] As described above, the average particle size of the near-infrared absorbing particles is preferably between 0.1 nm and 200 nm. This is because a smaller average particle size reduces the scattering of light in the visible light region with a wavelength of 400 nm to 780 nm caused by geometric scattering or Mie scattering. Reducing the scattering of this light can prevent a near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which the near-infrared absorbing particles are dispersed in a resin or the like, from becoming cloudy, like glass, thereby preventing a lack of clear transparency. Specifically, if the average particle size is less than 200 nm, the geometric scattering or Mie scattering mode of light scattering weakens, resulting in a Rayleigh scattering mode. In the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size. Therefore, as the dispersed particle size decreases, scattering decreases and transparency improves. Furthermore, an average particle size of less than 100 nm is preferred, as the scattered light becomes significantly less.

[0140] However, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin, does not become more agglomerated than the average particle size of the near-infrared absorbing particles in the dispersion as long as a known method of adding the dispersion to the solid medium is performed.

[0141] Furthermore, when the average particle size of the near-infrared absorbing particles is 0.1 nm to 200 nm, it is possible to avoid the produced near-infrared absorbing particle dispersion and its molded body (plate, sheet, etc.) from becoming gray particles with monotonically decreasing transmittance.

[0142] The content of the near-infrared-absorbing particles in the near-infrared-absorbing particle dispersion of this embodiment is not particularly limited, but is preferably, for example, from 0.01% to 80% by mass. This is because a near-infrared-absorbing particle content of 0.01% by mass or greater allows for a sufficient solar absorption rate. Furthermore, a content of 80% by mass or less allows for uniform dispersion of the near-infrared-absorbing particles within the dispersion medium.

[0143] [3] Near infrared curable ink composition

[0144] The near-infrared curable ink composition according to this embodiment will be described.

[0145] The near infrared curable ink composition of this embodiment can contain a thermosetting resin or a thermoplastic resin and near infrared absorbing particles. In addition, as the near infrared absorbing particles, the near infrared absorbing particles described above can be used. Therefore, the near infrared absorbing particles can contain, for example, a near infrared absorbing particle having the general formula Cs x W 1-y O 3-z (0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46) indicates cesium tungsten oxide having an orthorhombic or hexagonal crystal structure. Furthermore, the thermosetting resin may be in an uncured state, specifically, a fluid state, for example.

[0146] Hereinafter, the components contained in the near-infrared curable ink composition according to this embodiment will be described.

[0147] (1) Resin component

[0148] The near-infrared curable ink composition of this embodiment can contain a resin component, specifically, a thermosetting resin or a thermoplastic resin.

[0149] (1-1) About thermosetting resins

[0150] The thermosetting resin is not particularly limited, and for example, one or more selected from epoxy resins, urethane resins, acrylic resins, urea resins, melamine resins, phenolic resins, ester resins, polyimide resins, silicone resins, and unsaturated polyester resins can be used.

[0151] These thermosetting resins are uncured resins that cure by applying thermal energy from near-infrared absorbing particles exposed to near-infrared radiation. Furthermore, the thermosetting resin may comprise monomers or oligomers that form the thermosetting resin through a curing reaction, and a known curing agent that is appropriately added. Furthermore, a known curing accelerator may be added to the curing agent.

[0152] (1-2) About thermoplastic resins

[0153] As the thermoplastic resin, for example, one or more selected from polyester resins, polycarbonate resins, acrylic resins, polystyrene resins, polyamide resins, vinyl chloride resins, olefin resins, fluororesins, polyvinyl acetate resins, thermoplastic polyurethane resins, acrylonitrile butadiene styrene resins, polyvinyl acetal resins, acrylonitrile-styrene copolymer resins, ethylene-vinyl acetate copolymer resins, etc. can be used.

[0154] These thermoplastic resins are temporarily dissolved by applying thermal energy from the near-infrared absorbing particles irradiated with near-infrared rays, and can be solidified into a desired shape by subsequent cooling.

[0155] (2) Near-infrared absorbing particles

[0156] As the near-infrared absorbing particles, the aforementioned near-infrared absorbing particles can be used. The near-infrared absorbing particles have already been described, and their description is omitted here.

[0157] The content of the near-infrared absorbing particles in the near-infrared curable ink composition of the present embodiment is not particularly limited and can be selected based on the properties required of the near-infrared curable ink composition.

[0158] The near-infrared-curable ink composition of this embodiment can be added in an amount selected so that the uncured thermosetting resin can be cured during the curing reaction. Furthermore, the near-infrared-curable ink composition of this embodiment can be added in an amount selected so that the thermoplastic resin can be dissolved during the thermal dissolution reaction.

[0159] Therefore, the amount of near-infrared absorbing particles per unit area of ​​application of the near-infrared curable ink composition can be selected and determined in consideration of the coating thickness when applying the near-infrared curable ink composition.

[0160] The method for dispersing the near-infrared absorbing particles in the near-infrared curable ink composition is not particularly limited, but a wet media mill or the like is preferably used.

[0161] (3) Other ingredients

[0162] The near-infrared-curable ink composition of this embodiment may consist solely of the aforementioned resin component and near-infrared-absorbing particles, and may further contain arbitrary components, such as pigments, dyes, dispersants, and solvents described below, depending on the intended purpose. Furthermore, even when the near-infrared-curable ink composition consists solely of the resin component and near-infrared-absorbing particles, as described above, it is not excluded that it may contain unavoidable components that are introduced during the manufacturing process.

[0163] (3-1) Pigments and dyes

[0164] As described above, the near-infrared curable ink composition of the present embodiment may further contain one or more selected from organic pigments, inorganic pigments, and dyes in order to color the ink composition.

[0165] (3-1-1) Pigments

[0166] The pigment is not particularly limited, and known pigments can be used without particular limitation. Preferably, one or more pigments selected from organic pigments such as insoluble pigments and lake pigments and inorganic pigments such as carbon black can be used.

[0167] These pigments are preferably present in a state of being dispersed in the near-infrared curable ink composition of this embodiment. As a method for dispersing these pigments, a known method can be used without particular limitation.

[0168] The insoluble pigment is not particularly limited, and examples thereof include azo, azomethine, methylamine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, and diketopyrrolopyrrole.

[0169] The organic pigment is not particularly limited, but the specific pigments listed below can be preferably used.

[0170] Examples of the pigment for magenta or red include CI Pigment Red 2, CI Pigment Red 3, CI Pigment Red 5, CI Pigment Red 6, CI Pigment Red 7, CI Pigment Red 15, CI Pigment Red 16, CI Pigment Red 48:1, CI Pigment Red 53:1, CI Pigment Red 57:1, CI Pigment Red 122, CI Pigment Red 123, CI Pigment Red 139, CI Pigment Red 144, CI Pigment Red 149, CI Pigment Red 166, CI Pigment Red 177, CI Pigment Red 178, CI Pigment Red 202, CI Pigment Red 222, and CI Pigment Violet 19.

[0171] Examples of orange or yellow pigments include CI Pigment Orange 31, CI Pigment Orange 43, CI Pigment Yellow 12, CI Pigment Yellow 13, CI Pigment Yellow 14, CI Pigment Yellow 15, CI Pigment Yellow 15:3, CI Pigment Yellow 17, CI Pigment Yellow 74, CI Pigment Yellow 93, CI Pigment Yellow 128, CI Pigment Yellow 94, and CI Pigment Yellow 138.

[0172] Examples of green or blue pigments include CI Pigment Blue 15, CI Pigment Blue 15:2, CI Pigment Blue 15:3, CI Pigment Blue 16, CI Pigment Blue 60, and CI Pigment Green 7.

[0173] Examples of black pigments include CI Pigment Black 1, CI Pigment Black 6, and CI Pigment Black 7.

[0174] The inorganic pigment is not particularly limited, and preferably used are, for example, carbon black, titanium dioxide, zinc sulfide, zinc oxide, zinc phosphate, mixed metal oxide phosphates, iron oxide, manganese iron oxide, chromium oxide, ultramarine, nickel or chromium antimony titanium oxide, cobalt oxide, aluminum, aluminum oxide, silicon oxide, silicate, zirconium oxide, mixed oxides of cobalt and aluminum, molybdenum sulfide, rutile mixed-phase pigments, rare earth sulfides, bismuth vanadate, aluminum hydroxide, and extender pigments containing barium sulfate.

[0175] The average dispersed particle size of the dispersed pigment contained in the near-infrared-curable ink composition according to the present invention is not particularly limited, but is preferably, for example, 1 nm or more and 100 nm or less. This is because the storage stability of the near-infrared-curable ink composition is particularly good when the average dispersed particle size of the pigment dispersion is 1 nm or more and 100 nm or less. The average dispersed particle size can be measured, for example, using a particle size analyzer (ELS-8000, manufactured by Otsuka Electronics Co., Ltd.) using dynamic light scattering.

[0176] (3-1-2) Dyes

[0177] The dye is not particularly limited, and any oil-soluble dye or water-soluble dye can be used. Preferably, a yellow dye, a magenta dye, a blue dye, or the like can be used.

[0178] Yellow dyes include, for example, aromatic or heteroazo dyes having phenols, naphthols, anilines, pyrazolones, pyridones, and open-chain active methylene compounds as coupling components; azomethine dyes having open-chain active methylene compounds as coupling components; methine dyes such as benzylidene dyes and monomethine oxirol dyes; and quinone dyes such as naphthoquinone dyes and anthraquinone dyes. Other dye types include quinophthalone dyes, nitro-nitroso dyes, acridine dyes, and acridone dyes. These dyes may also be dyes that initially exhibit yellow color due to partial dissociation of the chromophore. In such cases, the countercation may be an inorganic cation such as an alkali metal or ammonium, an organic cation such as a pyridinium or quaternary ammonium salt, or a polymer cation having these compounds in a partial structure.

[0179] Examples of magenta dyes include aromatic or heteroazo dyes having phenols, naphthols, or anilines as coupling components; azomethine dyes having pyrazolones or pyrazolotriazoles as coupling components; methine dyes such as aromatic dyes, styryl dyes, merocyanine dyes, and oxanthene dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone, and anthrapyridone; and condensed polycyclic dyes such as dioxazine dyes. These dyes may initially exhibit magenta color by partial dissociation of the chromophore. In such cases, the countercation may be an inorganic cation such as an alkali metal or ammonium, an organic cation such as a pyridinium or quaternary ammonium salt, or a polymer cation having these as part of its structure.

[0180] Examples of blue dyes include azomethine dyes such as indoaniline dyes and indophenol dyes; polymethine dyes such as cyanine dyes, oxol dyes, and merocyanine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and xanthene dyes; phthalocyanine dyes; anthraquinone dyes; aromatic or heteroazo dyes having phenols, naphthols, and anilines as coupling components, and indigo-thioindigo dyes. These dyes may be dyes that initially exhibit a blue color by partial dissociation of the chromophore. In this case, the countercation may be an inorganic cation such as an alkali metal or ammonium, an organic cation such as a pyridinium or quaternary ammonium salt, or a polymer cation having these in a partial structure. In addition, black dyes such as polyazo dyes can also be used.

[0181] The water-soluble dye is not particularly limited, and direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, and the like can be preferably used.

[0182] As the water-soluble dye, the specific dyes listed below can be preferably used.

[0183] Examples include CIDIRECT RED 2, 4, 9, 23, 26, 31, 39, 62, 63, 72, 75, 76, 79, 80, 81, 83, 84, 89, 92, 95, 111, 173, 184, 207, 211, 212, 214, 218, 21, 223, 224, 225, 226, 227, 232, 233, 240, 241, 242, 243, 247,

[0184] CIDirect Violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101,

[0185] CIDIRECT YELLOW 8, 9, 11, 12, 27, 28, 29, 33, 35, 39, 41, 44, 50, 53, 58, 59, 68, 86, 87, 93, 95, 96, 98, 100, 106, 108, 109, 110, 130, 132, 142, 144, 161, 163,

[0186] CIDirect Blue 1, 10, 15, 22, 25, 55, 67, 68, 71, 76, 77, 78, 80, 84, 86, 87, 90, 98, 106, 108, 109, 151, 156, 158, 159, 160, 168, 189, 192, 193, 194, 1 99,200,201,202,203,207,211,213,214,218,225,229,236,237,244,248,249,251,252,264,270,280,288,289,291, CIDirect Black 9, 17, 19, 22, 32, 51, 56, 62, 69, 77, 80, 91, 94, 97, 108, 112, 113, 114, 117, 118, 121, 122, 125, 132, 146, 154, 166, 168, 173, 199,

[0187] C.I.Acid Red 35、42、52、57、62、80、82、111、114、118、119、127、128、131、143、151、154、158、249、254、257、261、263、266、289、299、301、305、336、337、361、396、397、

[0188] C.I.Acid Violet 5、34、43、47、48、90、103、126、

[0189] C.I.Acid yellow 17、19、23、25、39、40、42、44、49、50、61、64、76、79、110、127、135、143、151、159、169、174、190、195、196、197、199、218、219、222、227、

[0190] C.I.Acid blue 9、25、40、41、62、72、76、78、80、82、92、106、112、113、120、127:1、129、138、143、175、181、205、207、220、221、230、232、247、258、260、264、271、277、278、279、280、288、290、326、

[0191] C.I.Acid black 7、24、29、48、52:1、172、

[0192] C.I.Reactive Red 3、13、17、19、21、22、23、24、29、35、37、40、41、43、45、49、55、

[0193] C.I.Reactive Violet 1、3、4、5、6、7、8、9、16、17、22、23、24、26、27、33、34、

[0194] C.I.Reactive yellow 2、3、13、14、15、17、18、23、24、25、26、27、29、35、37、41、42、

[0195] C.I.Reactive blue 2、3、5、8、10、13、14、15、17、18、19、21、25、26、27、28、29、38、

[0196] CIReactive black 4, 5, 8, 14, 21, 23, 26, 31, 32, 34,

[0197] CIBasic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29, 35, 36, 38, 39, 45, 46,

[0198] CIBasic Violet 1, 2, 3, 7, 10, 15, 16, 20, 21, 25, 27, 28, 35, 37, 39, 40, 48,

[0199] CIBasic yellow 1, 2, 4, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39, 40,

[0200] CIBasic blue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69, 71,

[0201] CIBasic black 8, etc.

[0202] As described above, the particle size of the pigment or the like as the colorant is preferably determined in consideration of the characteristics of the coating apparatus for the near-infrared curable ink composition.

[0203] (3-2) Dispersant

[0204] The near-infrared-curable ink composition of this embodiment may further contain a dispersant. Specifically, the near-infrared-absorbing particles described above can be dispersed together with the dispersant in a thermosetting resin, a thermoplastic resin, or a solvent (an optional component described below). The addition of a dispersant facilitates the dispersion of the near-infrared-absorbing particles in the near-infrared-curable ink composition. Furthermore, when curing a coating film of the near-infrared-curable ink composition, uneven curing can be particularly suppressed.

[0205] The dispersant used in the near-infrared-curable ink composition of this embodiment is not particularly limited; for example, any commercially available dispersant can be used. However, the dispersant's molecular structure preferably has a polyester, polyacrylic acid, polyurethane, polyamine, polycarbonate, or polystyrene backbone, and a molecular structure having functional groups such as amino, epoxy, carboxyl, hydroxyl, or sulfonic groups. Dispersants with such molecular structures are less susceptible to degradation when a coating film of the near-infrared-curable ink composition of this embodiment is intermittently irradiated with near-infrared radiation for tens of seconds. This is because the occurrence of adverse effects such as discoloration caused by such degradation can be suppressed.

[0206] Specific examples of commercially available dispersants that can be suitably used include SOLSPERSE 3000, SOLSPERSE 9000, SOLSPERSE 11200, SOLSPERSE 13000, SOLSPERSE 13240, SOLSPERSE 13650, SOLSPERSE 13940, SOLSPERSE 16000, SOLSPERSE 17000, SOLSPERSE 18000, SOLSPERSE 20000, SOLSPERSE 21000, SOLSPERSE 24000SC, SOLSPERSE 24000GR, SOLSPERSE 26000, SOLSPERSE 27000, SOLSPERSE 28000, SOLSPERSE 29000, SOLSPERSE 30000, SOLSPERSE 31000, SOLSPERSE 32000, SOLSPERSE 33000, SOLSPERSE 33000, SOLSPERSE 34000, SOLSPERSE 35000, SOLSPERSE 36000, SOLSPERSE 37000, SOLSPERSE 38000, SOLSPERSE 39 ... S OLSPERSE36600, SOLSPERSE37500, SOLSPERSE38500, SOLSPERSE39000, SOLSPERSE41000, SOLSPERSE41090, SOLSPERSE53095, SOLSPERSE55000, SOLSPERSE56000, SOLSPERSE76500, etc.;

[0207] Manufactured by BYK Japan Co., Ltd.: Disperbyk-101, Disperbyk-103, Disperbyk-107, Disperbyk-108, Disperbyk-109, Disperbyk-110, Disperbyk-111, Disperbyk-112, Disperbyk-116, Disperbyk-130, Disperbyk-140, Disperbyk-142, Disperbyk-145, Disperbyk-154, Disperbyk-161, Disperbyk-162, Disperbyk-163, Disperbyk-164, Disperbyk-165, Disperbyk-166, Disperbyk-167, Disperbyk-168, Disperbyk-170, Disperbyk-171, Disperbyk-174, Disperbyk-180, Disperbyk-181, Disperbyk-182, Disperbyk-183, Disperbyk-184, Disperbyk-185, Disperbyk-190, Disperbyk-2000, Disperbyk-2001, Disperbyk-2020, Disperbyk-2025, Disperbyk-2050, Disperbyk-2070, Disperbyk-2095, Disperbyk-2150, Disperbyk-2155, Anti-Terra-U, Anti-Terra-203, Anti-Terra-204, BYK-P104, BYK-P104S, BYK-220S, BYK-6919, etc.;

[0208] EFKA4008, EFKA4046, EFKA4047, EFKA4015, EFKA4020, EFKA4050, EFKA4055, EFKA4 manufactured by BASFjapan Co., Ltd. 060, EFKA4080, EFKA4300, EFKA4330, EFKA4400, EFKA4401, EFKA4402, EFKA4403, EFKA4500, EFKA4510 , EFKA4530, EFKA4550, EFKA4560, EFKA4585, EFKA4800, EFKA5220, EFKA6230, JONCRYL67, JONCRYL678 , JONCRYL586, JONCRYL611, JONCRYL680, JONCRYL682, JONCRYL690, JONCRYL819, JONCRYL-JDX5050, etc.;

[0209] Ajinomoto Fine Techno Co., Ltd. Ajispur PB-711, Ajispur PB-821, Ajispur PB-822, etc.

[0210] Furthermore, as the dispersant, the dispersants described in the aforementioned near-infrared absorbing particle dispersion can also be used.

[0211] (3-3) Solvent

[0212] The near-infrared curable ink composition of this embodiment can also use a solvent together with the thermosetting resin or the thermoplastic resin. That is, the near-infrared curable ink composition of this embodiment can also further contain a solvent.

[0213] In this case, as a solvent for the near-infrared curable ink composition, for example, a reactive organic solvent having a functional group such as an epoxy group that reacts with monomers or oligomers of the thermosetting resin contained in the thermosetting resin that is in an uncured state during the curing reaction of the thermosetting resin is preferably used.

[0214] The addition of a solvent can adjust the viscosity of the near-infrared curable ink composition. This is because adjusting the viscosity of the near-infrared curable ink composition facilitates ensuring the coating properties of the near-infrared curable ink composition and the smoothness of the coating film.

[0215] The solvent is not particularly limited, and various organic solvents such as water, methanol, ethanol, propanol, butanol, isopropanol, isobutyl alcohol, and diacetone alcohol, ethers such as methyl ether, ethyl ether, and propyl ether, esters, ketones such as acetone, methyl ethyl ketone, diethyl ketone, cyclohexanone, and isobutyl ketone, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, polyethylene glycol, and polypropylene glycol can be used.

[0216] Furthermore, as the solvent, the liquid medium described in the aforementioned near-infrared absorbing particle dispersion can also be used.

[0217] [4] Method for producing near-infrared curable ink composition

[0218] As described above, the near-infrared-curable ink composition of this embodiment can be prepared by adding the near-infrared-absorbing particles to an uncured thermosetting resin or thermoplastic resin. Alternatively, the near-infrared-curable ink composition of this embodiment can be prepared by dispersing the near-infrared-absorbing particles in a suitable solvent and then adding the uncured thermosetting resin or thermoplastic resin. Furthermore, the near-infrared-curable ink composition of this embodiment can also be prepared by adding the uncured thermosetting resin or thermoplastic resin to the aforementioned near-infrared-absorbing particle dispersion.

[0219] The near-infrared-curable ink composition of this embodiment contains the aforementioned near-infrared-absorbing particles. Therefore, when applied to a substrate and irradiated with near-infrared light to form a cured film, a more neutral hue can be achieved. Furthermore, the near-infrared-absorbing particles have excellent near-infrared absorption properties, allowing sufficient heat to be supplied during irradiation with near-infrared light, resulting in a cured film with substantially improved adhesion to the substrate.

[0220] Furthermore, the near-infrared curable ink composition of this embodiment can also be used to form three-dimensional objects on a substrate. In other words, it is an optimal near-infrared curable ink composition for photolithography methods for forming three-dimensional objects.

[0221] As described above, the near-infrared curable ink composition of this embodiment contains a solvent, and thus its viscosity can be adjusted. Therefore, the workability when applied to a substrate or the like can be improved.

[0222] However, as previously mentioned, the near-infrared-curable ink composition of this embodiment does not need to contain a solvent. By not containing a solvent, the near-infrared-curable ink composition of this embodiment can save on operations such as solvent volatilization, thereby improving the efficiency of curing an article coated with the near-infrared-curable ink composition.

[0223] When the near-infrared curable ink composition of this embodiment contains a solvent, the method for removing the solvent after applying the near-infrared curable ink composition is not particularly limited, and for example, a heating distillation method with reduced pressure can be used.

[0224] [Near infrared curing film]

[0225] The near-infrared cured film of the present embodiment can be a cured product of the aforementioned near-infrared curable ink composition.

[0226] The near-infrared cured film of the present embodiment can be produced by, for example, the method for producing a near-infrared cured product described below.

[0227] Specifically, after applying the aforementioned near-infrared curable ink composition to a surface of a substrate or the like (coating step), the solvent and the like are removed as needed, and the near-infrared curable ink composition is cured by irradiation with near-infrared rays (curing step).

[0228] The coating step and curing step can be repeated to form a near-infrared cured film of desired shape and size. In addition, a three-dimensional object can be formed on the substrate, in which case it can also be called a near-infrared cured product.

[0229] [Method for producing near-infrared cured product]

[0230] The method for producing a near-infrared cured product according to the present embodiment can include the following coating step and curing step.

[0231] In the coating step, the aforementioned near-infrared curable ink composition can be applied to the substrate to form a coating film.

[0232] In the curing step, the coating film can be irradiated with near-infrared rays to cure the near-infrared curable ink composition.

[0233] The aforementioned near-infrared curable ink composition has visible light transmittance. Therefore, the near-infrared curable ink composition is applied to obtain a coating film, and the coating film is irradiated with near-infrared rays to be cured, thereby obtaining a near-infrared cured film that exhibits excellent adhesion to a predetermined substrate.

[0234] Furthermore, a colored film can be obtained by adding at least one of various pigments or dyes to the near-infrared-curable ink composition. Since the near-infrared-absorbing particles have little effect on the color of the colored film, the colored film can also be used in color filters for liquid crystal displays and the like.

[0235] The near-infrared-cured film of this embodiment exhibits excellent adhesion as described above. This is believed to be because the near-infrared-absorbing particles absorb the irradiated near-infrared rays and generate heat. This heat energy promotes polymerization, condensation, and addition reactions of monomers and oligomers contained in the uncured thermosetting resin, thereby causing a curing reaction of the thermosetting resin. Furthermore, the near-infrared-cured film of this embodiment exhibits excellent adhesion as described above. It is believed that the heat generated by the near-infrared-absorbing particles upon irradiation with near-infrared rays provides sufficient heat, causing the thermoplastic resin to dissolve and cure by cooling.

[0236] Furthermore, the aforementioned near-infrared curable ink composition may also contain a solvent, and the solvent and the like may be volatilized by the heat generated by the near-infrared absorbing particles.

[0237] When the aforementioned near-infrared absorption curable ink composition contains a thermosetting resin as a resin component, the near-infrared cured film formed using the near-infrared absorption curable ink composition does not remelt even when further irradiated with near-infrared rays. This is because the near-infrared cured film comprises a cured product of the thermosetting resin, and therefore, even when irradiated with near-infrared rays, the near-infrared absorbing particles generate heat and do not remelt.

[0238] This characteristic is particularly effective when applied to a photolithography method for molding three-dimensional objects by repeatedly applying the near-infrared curable ink composition of this embodiment and irradiating it with near-infrared rays, and repeatedly laminating the cured product of the near-infrared curable ink composition, combined with excellent adhesion to the above-mentioned substrate.

[0239] Hereinafter, each step will be described.

[0240] (1) Coating process

[0241] In the coating step, the aforementioned near-infrared curable ink composition can be applied to the substrate to form a coating film.

[0242] The material of the substrate (base material) to which the near-infrared curable ink composition is applied in the coating step is not particularly limited.

[0243] As the substrate, for example, one or more substrates selected from paper, resin, glass, and the like can be used.

[0244] The resin is not particularly limited, and for example, one or more selected from polyesters such as PET (polyethylene terephthalate), acryl, urethane, polycarbonate, polyethylene, ethylene vinyl acetate copolymer, vinyl chloride, fluororesin, polyimide, polyacetal, polypropylene, nylon, etc. can be used.

[0245] The shape of the substrate is not particularly limited, and can be formed into a shape that conforms to the shape required for the near-infrared-cured product, for example, a plate-like shape.

[0246] The method for coating the substrate surface with the near-infrared curable ink composition is not particularly limited, and methods such as dipping, flow coating, spraying, bar coating, spin coating, gravure coating, roll coating, screen printing, and blade coating can be used.

[0247] (2) Curing process

[0248] In the curing step, the coating film can be irradiated with near-infrared rays to cure the near-infrared curable ink composition.

[0249] As a method for curing a near-infrared curable ink composition, infrared irradiation is preferred, and near-infrared irradiation is more preferred. Near-infrared rays have a high energy density and can efficiently provide the energy required to cure the resin in the near-infrared curable ink composition.

[0250] The near-infrared curable ink composition is preferably cured by combining infrared irradiation with any method selected from known methods. For example, heating, air blowing, or electromagnetic wave irradiation can be used in combination with infrared irradiation.

[0251] In this specification, infrared radiation refers to electromagnetic waves with a wavelength in the range of 0.1 μm to 1 mm, near-infrared radiation refers to infrared radiation with a wavelength of 0.75 μm to 4 μm, and far-infrared radiation refers to infrared radiation with a wavelength of 4 μm to 1000 μm. Generally speaking, near-infrared-curable ink compositions can be cured even when irradiated with either far-infrared or near-infrared radiation, achieving the same effects. However, irradiation with near-infrared radiation allows for more efficient curing of the coating film in a shorter time.

[0252] As mentioned above, it is also possible to irradiate electromagnetic waves together with near-infrared rays when curing a near-infrared curable ink composition. Microwaves are suitable for use as such electromagnetic waves. Microwaves are electromagnetic waves with a wavelength in the range of 1 mm to 1 m.

[0253] The microwave power used for irradiation is preferably 200 W to 1000 W. A power of 200 W or greater promotes the vaporization of the organic solvent remaining in the near-infrared curable ink composition, while a power of 1000 W or less provides mild irradiation conditions, eliminating the risk of deterioration of the substrate, thermosetting resin, and other resin components contained in the near-infrared curable ink composition.

[0254] The infrared irradiation time for a near-infrared-curable ink composition varies depending on the irradiation energy, wavelength, composition of the near-infrared-curable ink, and the amount of near-infrared-curable ink applied, and is therefore not particularly limited. For example, the infrared irradiation time is generally preferably 0.1 seconds or longer. By setting the irradiation time to 0.1 seconds or longer, the near-infrared-curable ink composition can be cured, thereby enabling sufficient infrared irradiation. Prolonging the irradiation time allows, for example, sufficient drying of the solvent in the infrared absorption-curable ink composition. If high-speed printing or coating is involved, the irradiation time is preferably 30 seconds or less, and more preferably 10 seconds or less.

[0255] The infrared radiation source is not particularly limited. Infrared radiation can be generated directly from a heat source or efficiently through the use of a heat medium. For example, infrared radiation can be generated by discharge lamps such as mercury, xenon, cesium, and sodium lamps, carbon dioxide lasers, or by heating resistors such as platinum, tungsten, nickel-chromium, and tantalum. Halogen lamps are also preferred radiation sources. Halogen lamps offer advantages such as good thermal efficiency and rapid heat rise.

[0256] Irradiation of the coating film with infrared light can be performed from either the side of the substrate coated with the near-infrared-curable ink or from the back side of the substrate, the side opposite the coated surface. Simultaneous irradiation from both sides is preferred, and is preferably combined with elevated temperature drying or air drying. Furthermore, the use of a focusing plate is more preferred as needed. By combining these methods, it is possible to cure the near-infrared-curable ink composition using short-term infrared irradiation.

[0257] Furthermore, the method for producing a near-infrared-cured product according to this embodiment can produce the aforementioned near-infrared-cured film. Furthermore, by repeatedly laminating cured products of near-infrared-curable ink compositions, three-dimensional objects can be formed. Specifically, by repeating the aforementioned coating and curing (irradiation) steps, a near-infrared-cured product having a desired three-dimensional structure can be produced.

[0258] The method for producing a near-infrared cured product according to this embodiment can be implemented with a photolithography method, that is, a photolithography method including the coating step and the curing step described here can also be implemented.

[0259] Example

[0260] Hereinafter, the present invention will be described in detail with reference to Examples. However, the present invention is not limited to the following Examples.

[0261] First, the evaluation method of the near-infrared absorbing particles in the following experimental examples will be described.

[0262] (Chemical Analysis)

[0263] In the chemical analysis of the obtained near-infrared absorbing particles, Cs was analyzed by atomic absorption analysis (AAS), and W (tungsten) was analyzed by ICP emission spectrometry (1CP-OES). In addition, for O, a light element analyzer (manufactured by LECO, type ON-836) was used, the sample was melted in He gas, and the CO gas that reacted with the carbon in the crucible was analyzed by IR absorption spectrometry. In addition, in the following Experimental Examples 1-1 to Experimental Example 1-13, powders as near-infrared absorbing particles containing cesium tungsten composite oxides with W defects were obtained. Therefore, with respect to the powders A to powder M as near-infrared absorbing particles obtained by Experimental Examples 1-1 to Experimental Examples 1-13, it can be confirmed that any of the composition ratios obtained by multiplying the composition ratio when W is 1 by the value corresponding to the W defect obtained by TEM observation, etc. satisfies the general formula Cs x W 1-y O 3-z (0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46).

[0264] (X-ray diffraction measurement)

[0265] X-ray diffraction measurement was performed by powder XRD measurement using Cu-Kα radiation using an X'Pert-PRO / MPD apparatus from Spectris.

[0266] Utilize standard sample (NIST640e) to calibrate the diffraction angle and measure after that.And, about the XRD diffraction pattern of gained, carry out Rietveld analysis, obtain the lattice constant of crystallization phase.In addition, in Table 1, the crystallization phase of description identification in the hurdle of the pattern of the hurdle of X-ray diffraction measurement result, when " rhombic + hexagonal ", comprise rhombic and hexagonal.In addition, when " rhombic ", comprise rhombic, when " hexagonal ", comprise hexagonal.

[0267] In the case of a mixed phase of orthorhombic and hexagonal crystals, the lattice constants of each phase were determined. The lattice constants of the orthorhombic crystal were converted to the lattice constants of the hexagonal crystal using the following lattice correspondence model. The correspondence between the lattice changes of the orthorhombic and hexagonal crystals was calculated using the formula extracted from the model of Solodovnikov 1998 (Non-Patent Document 4), 4a orth 2 +b orth 2 =64a hex 2 =64b hex 2 , c orth =c hex, find the lattice constant of hexagonal crystal conversion. In addition, a in the above formula orth 、b orth 、c orth Indicates the lengths of the a-axis, b-axis, and c-axis of the orthorhombic crystal. hex 、b hex 、c hex Indicates the lengths of the a-axis, b-axis, and c-axis of the hexagonal crystal.

[0268] [Experimental Example 1]

[0269] Near-infrared absorbing particles used in Experimental Example 2 described later were produced and evaluated.

[0270] [Experimental Example 1-1]

[0271] Cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 2:11. The resulting kneaded mixture was placed in a carbon boat and heated twice in a tubular furnace at 850°C in air for 20 hours. This yielded a very thin, greenish white powder A'. Furthermore, after heating at 850°C for 20 hours, the mixture was temporarily removed, crushed, mixed, and then reheated under the same conditions.

[0272] The obtained white powder A' was evaluated as follows.

[0273] The X-ray powder diffraction pattern showed that only Cs6W was mixed in. 11 O 36 , but basically Cs4W 11 O 35 Single phase (ICDD 00-51-1891).

[0274] The lattice constant was determined to be The values ​​involved are the same as those of Solodovnikov (Non-Patent Document 4) The chemical analysis results of the white powder were Cs 0.36 WO 3.18 , which is basically consistent with the weighing composition.

[0275] Next, the obtained white powder, Powder A', was observed by TEM. A restricted field electron diffraction pattern was taken to obtain an orthorhombic spot pattern. Figure 4The figure shows the spot pattern obtained from the c-axis of the orthorhombic crystal. A periodicity of b / 8 cycles is confirmed along the b-axis, with the presence of W and O defect surfaces. Furthermore, it can be seen from the lines running along the b-axis that the b-plane has a certain degree of surface defects. The spot pattern along the c-axis crystal zone axis is close to 6-fold symmetry, with the (480) and (4-80) spot angles being 52.2°, which is offset from the 60° in the case of 6-fold symmetry. This is believed to be due to the W and O defect surfaces entering the b / 8 cycle, resulting in a shift from 6-fold symmetry.

[0276] The obtained white powder Cs4W 11 O 35 The powder was spread thinly and evenly on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800°C in an Ar gas flow. While maintaining the temperature at 800°C, the flow was switched to a 1 vol% H2 gas (hereinafter simply referred to as % by volume) mixed with Ar gas as a carrier. After 5 minutes of reduction, the H2 gas flow was stopped, and the Ar gas flow alone was used to slowly cool the mixture to 100°C. The Ar gas flow was then stopped, and the mixture was slowly cooled to room temperature before removal of Powder A. The removed Powder A had a light blue hue.

[0277] The XRD pattern of powder A shows a two-phase mixed pattern of orthorhombic and hexagonal crystals. The lattice constants of each phase were calculated using the Rietveld method, and the orthorhombic crystal was (The hexagonal conversion value is ), hexagonal crystal is It is confirmed that both of the c-axis values ​​are located at within the range.

[0278] Next, TEM observation of the powder A was performed, and as a result, orthorhombic particles and pseudo-hexagonal particles were observed.

[0279] here, Figure 5 The electron beam diffraction image of pseudo-hexagonal particles is shown in Figure 2. Figure 5

[001] HEX The electron beam diffraction image of the crystal zone axis shows a diffraction pattern close to that of a hexagonal crystal. Here (200) HEX and (110) HEX The interplanar angle was measured to be 59.2°, which is a value close to that of a hexagonal crystal.

[0280] Next, powder A was observed using the STEM-HAADF mode (STEM: scanning transmission electron microscopy, HAADF: High-angle annular dark field).

[0281] The HAADF image observed from the

[221] zone axis of the pseudo-hexagonal particles is shown in Figure 6 In the HAADF mode, the atomic particles are observed by atomic number and brightness proportional to the probability of atomic existence in the projection direction. Figure 6 Looks dark (110) HEX The linear region is identified as the defect of the largest atomic number W. The trajectory of such a W defect region is confirmed by observing from other directions. HEX Furthermore, it is considered that a portion of the trajectory with low contrast shrinks linearly.

[0282] In this experimental example, the heating reduction treatment was 5 minutes, which was shorter than that of other experimental examples described later. In the initial stage of reduction at high temperature, the orthorhombic (010) ORTH The W defects shrink and the structure shifts to the pseudo-hexagonal crystal. In the pseudo-hexagonal crystal, it is observed that the {100} HEX Most of the W defect areas are in the process of surface shrinkage.

[0283] [Experimental Example 1-2]

[0284] The Cs4W powder A' obtained in Experimental Example 1-1 was 11 O 35 The powder was spread thinly and evenly on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800°C in an Ar gas flow. While maintaining the temperature at 800°C, the flow was switched to a 1% H₂ gas mixed with Ar gas as a carrier. After 15 minutes of reduction, the H₂ gas flow was stopped, and the Ar gas flow alone was used, slowly cooling to 100°C. The Ar gas flow was then stopped, and the mixture was slowly cooled to room temperature before powder B was removed. The removed powder B had a blue hue.

[0285] The XRD pattern of powder B shows a mixed pattern of orthorhombic and hexagonal phases. The lattice constants of each phase were calculated using the Rietveld method, and the orthorhombic phase was obtained as (The hexagonal conversion value is ), hexagonal crystal is It is confirmed that both of the c-axis values ​​are located at within the range.

[0286] Next, TEM observation of powder B was performed. As in the case of powder A obtained in Experimental Example 1-1, orthorhombic particles and pseudo-hexagonal particles were observed. Figure 7

[001] HEXThe electron beam diffraction image of the crystal zone axis shows a diffraction pattern close to that of a hexagonal crystal. Here (200) HEX and (110) HEX The interplanar angle was measured to be 59.5°, which is a value close to that of a hexagonal crystal.

[0287] [Experimental Examples 1-3]

[0288] The Cs4W powder A' obtained in Experimental Example 1-1 was 11 O 35 The powder was spread thinly and evenly on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800°C in an Ar gas flow. While maintaining the temperature at 800°C, the flow was switched to a 1% H₂ gas mixed with Ar gas as a carrier. After 30 minutes of reduction, the H₂ gas flow was stopped, and the Ar gas flow alone was used, slowly cooling to 100°C. The Ar gas flow was then stopped, and the mixture was slowly cooled to room temperature before removal of powder C. The removed powder C had a dark blue hue.

[0289] The XRD pattern of powder C showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. The lattice constants of each phase were calculated using the Rietveld method, and the orthorhombic crystal was (The hexagonal conversion value is ), hexagonal crystal is It is confirmed that both of the c-axis values ​​are located at within the range.

[0290] Next, TEM observation of powder C was performed. As in the case of powder A obtained in Experimental Example 1-1, orthorhombic particles and pseudo-hexagonal particles were observed. Figure 8 The electron beam diffraction image of the

[001] zone axis shows a hexagonal diffraction pattern. Here, (200) HEX and (110) HEX The inter-plane angle of was measured to be 60.0°, which is a value of a hexagonal crystal.

[0291] [Experimental Examples 1-4 to 1-7]

[0292] The Cs4W powder A' obtained in Experimental Example 1-1 was 11 O 35 The reduction time during the powder reduction treatment was changed to 35 to 90 minutes as shown in Table 1, producing Powders D, E, F, and G. Powders D to G all had a dark blue color tone and had XRD lattice constants as shown in the table.

[0293] In addition, as shown in Table 1, in Experimental Examples 1-4, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was (Experimental Examples 1-4).

[0294] [Experimental Examples 1-8 to 1-11]

[0295] The Cs4W powder A' obtained in Experimental Example 1-1 was 11 O 35 The heating temperature and reduction time for the powders during the heat reduction treatment were varied as shown in Table 1. Specifically, in Experiment 1-8, the heating temperature was 650°C for 120 minutes, in Experiment 1-9, the heating time was 700°C for 60 minutes, in Experiment 1-10, the heating time was 900°C for 10 minutes, and in Experiment 1-11, the heating time was 950°C for 20 minutes. Otherwise, the same procedures as those for preparing Powder A in Experiment 1-1 were followed to produce Powder H, Powder I, Powder J, and Powder K. Light blue, blue, dark blue, and dark blue powders were obtained, respectively. The lattice constants obtained from the XRD patterns of the obtained powders are shown in Table 1.

[0296] In addition, as shown in Table 1, in Experimental Examples 1-8 and 1-9, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was (Experimental Example 1-8), (Experimental Example 1-9).

[0297] [Experimental Example 1-12]

[0298] Cesium carbonate and tungsten trioxide were mixed at a molar ratio of Cs2CO3:WO3=3:11, spread thinly and evenly on a carbon boat, placed in a tubular furnace, and heated at 850℃ for 5 hours to obtain an extremely thin white powder with a green tint. The main phase of this white powder was identified as Cs6W 11 O 36 (ICDD1-70-632), is the same as Cs4W 11 O 35 of mixed phase.

[0299] The obtained white powder was heat-treated at 800°C for 30 minutes in a 1% H2-N2 gas flow to obtain a dark blue powder L.

[0300] The XRD pattern of powder L showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. The lattice constants obtained from the XRD pattern of the obtained powder L are shown in Table 1. In addition, as mentioned above, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystals was

[0301] [Experimental Example 1-13]

[0302] Cesium carbonate and tungsten trioxide were mixed at a molar ratio of Cs2CO3:WO3 = 1:6, and then spread thinly and evenly on a carbon boat. The mixture was placed in a tubular furnace and heated at 850°C for 5 hours to obtain an extremely thin white powder with a green tint. The main phase of the white powder was identified as Cs4W 11 O 35 , is the same as Cs2W6O 19 (ICDD00-045-0522) miscible phase.

[0303] The obtained white powder was heat-treated at 800°C for 30 minutes in a 1% H2-N2 gas flow to obtain a dark blue powder M.

[0304] The XRD pattern of powder M showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. The lattice constants obtained from the XRD pattern of the obtained powder M are shown in Table 1. In addition, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystals was

[0305] [Table 1]

[0306]

[0307] As shown in Experimental Examples 1-1 to 1-13 above, if the Cs4W 11 O 35 、Cs6W 11 O 36 、Cs2W6O 19 Cs4W 11 O 35 When the powder is reduced at high temperature, the pink color gradually changes from light blue to blue and dark blue.

[0308] In addition, in Cs4W 11 O 35 The phase contains lattice defects including W defects, forming an orthorhombic crystal. However, when reduced at high temperature, it was confirmed that the lattice defects including W defects were reduced and disappeared, and the orthorhombic crystal was converted into a hexagonal crystal.

[0309] Furthermore, it was confirmed that the cesium tungsten oxides contained in the powders A to M obtained in Experimental Examples 1-1 to 1-13 all had W defects and O defects.

[0310] [Experimental Example 2]

[0311] Using the near-infrared absorbing particles produced in Experimental Example 1, a near-infrared absorbing curable ink composition and a near-infrared absorbing cured film (hereinafter, sometimes simply referred to as a “cured film”) were produced and evaluated.

[0312] Experimental Examples 2-1 to 2-14 are examples, and Experimental Examples 2-15 and 2-16 are comparative examples.

[0313] [Experimental Example 2-1]

[0314] 20% by mass of Powder A prepared in Experimental Example 1-1, 20% by mass of an acrylic polymer dispersant having an amine-containing functional group (hereinafter referred to as "Dispersant A"), and 60% by mass of methyl isobutyl ketone as a solvent were weighed. These materials were placed in a glass container along with 0.3 mm diameter silica beads and dispersed and pulverized for 1 hour using a paint shaker to obtain Dispersion A.

[0315] Here, the average particle size of the near-infrared absorbing particles in the dispersion A was measured (dispersed particle size measured using a particle size measuring apparatus ELS-8000 manufactured by Otsuka Electronics Co., Ltd. using a dynamic light scattering method) and was found to be 28.2 nm.

[0316] 25 parts by mass of the dispersion A was mixed with 75 parts by mass of a commercially available one-part thermosetting ink (MEG screen ink (medium) manufactured by Teikoku Ink Manufacturing Co., Ltd.) containing an uncured thermosetting resin to prepare a near-infrared curable ink composition according to Experimental Example 2-1 (hereinafter referred to as Ink A).

[0317] Ink A was applied to a blue plate glass having a thickness of 3 mm using a bar coater (No. 10) to form a coating film (coating step).

[0318] Next, the coating film was irradiated with near-infrared rays to obtain a near-infrared cured film (hereinafter referred to as a cured film A) (curing step).

[0319] In the curing step, a line heater HYP-14N (output 980 W) manufactured by Hi-bec Co., Ltd. was used as a near-infrared irradiation source. The heater was set at a height of 5 cm from the coated surface of the coating film, and near-infrared irradiation was performed for 10 seconds.

[0320] The obtained cured film A had a thickness of 20 μm and was visually confirmed to be transparent.

[0321] The average particle size of the cesium tungsten oxide particles dispersed in the cured film A was calculated using an image processing device using a transmission electron microscope image and was found to be 24 nm. The particle size of each particle is the diameter of the circumscribed circle of the particle, and the average particle size was calculated as the average of the particle sizes measured for 100 particles.

[0322] The adhesiveness of the cured film A was evaluated by the method shown below.

[0323] Cured film A was cut into 100 square grids using a cutter guide with 1 mm gaps. An 18 mm wide tape (Cellotape (registered trademark) CT-18, manufactured by Nichiban Co., Ltd.) was then applied to the cut surfaces of the grid. A 2.0 kg roller was moved back and forth 20 times to completely adhere the film. The film was then peeled sharply at a 180-degree peel angle, and the number of peeled squares was counted. The number of peeled squares was considered zero.

[0324] Even when the cured film A was irradiated with near infrared rays for 20 seconds under the same conditions as those used for curing the near infrared curing ink, the cured film did not remelt.

[0325] Furthermore, the spectral characteristics of the prepared cured film A were measured using a spectrophotometer manufactured by Hitachi, Ltd., by measuring the reflectivity of light with a wavelength of 200 nm to 2100 nm, and the color index was calculated. As a result, it was confirmed that L ＊ =88,a ＊ =-1, b ＊ =8, a very weak blue, neutral tone.

[0326] The results are shown in Table 2. In addition, Table 2 also shows the results obtained in Experimental Examples 2-2 to 2-16 described later.

[0327] [Experimental Examples 2-2 to 2-13]

[0328] The near-infrared-curable ink compositions and cured films of Experimental Examples 2-2 to 2-13 were obtained and evaluated in the same manner as in Experimental Example 2-1, except that Powders B to M prepared in Experimental Examples 1-2 to 1-13 were used instead of Powder A. The evaluation results are shown in Table 2.

[0329] [Experimental Example 2-14]

[0330] A near-infrared-curable ink composition and cured film according to Experimental Example 2-14 were obtained and evaluated in the same manner as in Experimental Example 2-1, except that a solution of an acrylic resin in methyl isobutyl ketone was used as the thermoplastic resin instead of the thermosetting resin in Experimental Example 2-1. The evaluation results are shown in Table 2.

[0331] [Experimental Example 2-15]

[0332] Instead of powder A, Cs4W was used as powder A′ obtained in Experimental Example 1-1. 11 O 35 The near-infrared curable ink composition and cured film according to Experimental Example 2-15 were obtained and evaluated in the same manner as in Experimental Example 2-1 except for the above-mentioned changes in the powder. The evaluation results are shown in Table 2.

[0333] [Experimental Example 2-16]

[0334] A raw material mixture was prepared by weighing, mixing, and kneading cesium carbonate (Cs2CO3) aqueous solution, tungstic acid (H2WO4) and tungsten dioxide powder (WO2) so as to have a composition of Cs2O·5WO3·4WO2. After thorough mixing, the raw material mixture was spread thinly and evenly on a carbon boat. Under a 1% H2 gas flow with N2 gas as a carrier, it was kept at 550°C for 60 minutes, then changed to 100% N2 gas flow, kept for 1 hour, and then heated to 800°C and kept for 1 hour. It was slowly cooled to room temperature to obtain powder O. The color of powder O was dark blue. As a result of chemical analysis, the composition of Cs 0.33 WO 2.74 .

[0335] The XRD pattern of powder O shows a single phase of hexagonal crystals. The lattice constants were obtained by Rietveld analysis. The value of the lattice constant c-axis is a preferred value.

[0336] TEM observations revealed no significant lattice defects, and STEM atomic imaging revealed no significant lattice defects or W defects.

[0337] Instead of powder A, the above-mentioned Cs 0.33 WO 2.74 A near-infrared curable ink composition and a cured film according to Experimental Example 2-16 were obtained and evaluated in the same manner as in Experimental Example 2-1 except for the above-mentioned changes in the powder. The evaluation results are shown in Table 2.

[0338] [Table 2]

[0339]

[0340] According to the results shown in Table 2, it can be confirmed that the use of x W 1-y O 3-z (0.2 ≤ x ≤ 0.4, 0 < y ≤ 0.4, 0 < z ≤ 0.46) indicates that the cured films produced using the near-infrared-curable ink compositions of Experimental Examples 2-1 to 2-14, which contain near-infrared-absorbing particles of cesium tungsten oxide with an orthorhombic or hexagonal crystal structure, exhibited a very weak blue hue, with a neutral hue. This indicates that the cured films of these experimental examples, containing near-infrared-absorbing particles containing composite tungsten oxide, exhibited a more neutral hue.

[0341] On the other hand, the near-infrared absorbing particles contained in the cured films of Experimental Examples 2-15 and 2-16 did not contain cesium tungsten oxide satisfying the above-mentioned general formula.

[0342] Furthermore, it can be seen that b of the cured film of Experimental Example 2-16 ＊ The value was negative, and the color was clearly recognized as blue. In other words, it was confirmed that the cured film of Experimental Example 2-16 could not have a neutral color tone.

[0343] The cured film of Experimental Example 2-15 had a neutral hue, but poor adhesion was confirmed as apparent from the results in Table 2. This is presumably because the near-infrared absorbing particles contained in the near-infrared curable ink composition used in Experimental Example 2-15 had a low solar absorptivity.

[0344] This application claims the benefit of priority based on Japanese Patent Application No. 2021-124045 filed with the Japan Patent Office on July 29, 2021, and the entire contents of Japanese Patent Application No. 2021-124045 are incorporated herein by reference.

Claims

1. A near-infrared curable ink composition comprising: Thermosetting resin or thermoplastic resin, and Near-infrared absorbing particles, The near infrared absorbing particles contain Cs x W 1-y O 3-z It represents cesium tungsten oxide having an orthorhombic or hexagonal crystal structure, wherein 0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46, The cesium tungsten oxide has linear or planar defects on one or more planes selected from the group consisting of a (010) plane of an orthorhombic crystal, a {100} plane which is a prism plane of a hexagonal crystal, and a (001) plane which is a bottom plane of a hexagonal crystal.

2. The near-infrared curable ink composition according to claim 1, The cesium tungsten oxide has defects, and the defects include tungsten defects.

3. The near-infrared curable ink composition according to claim 1 or 2, In the cesium tungsten oxide, the c-axis length of the hexagonal conversion is above the following.

4. The near-infrared curable ink composition according to any one of claims 1 to 3, A portion of O in the WO 6 octahedron constituting the cesium tungsten oxide crystal is defective.

5. The near-infrared curable ink composition according to any one of claims 1 to 4, A portion of the Cs in the cesium tungsten oxide is replaced by an additional element. The added element is one or more selected from the group consisting of Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

6. The near-infrared curable ink composition according to any one of claims 1 to 5, The near-infrared absorbing particles have an average particle size of 0.1 nm to 200 nm.

7. The near-infrared curable ink composition according to any one of claims 1 to 6, The surfaces of the near-infrared absorbing particles are coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn.

8. The near-infrared curable ink composition according to any one of claims 1 to 7, The near-infrared absorbing particles are particles obtained by heating and reducing the crystalline powder of cesium tungsten oxide precursor nCs2O·mWO3 in a reducing gas atmosphere at a temperature of 650°C to 950°C, wherein n and m are integers, and 3.6≤m / n≤9.

0.

9. The near-infrared curable ink composition according to any one of claims 1 to 8, The near infrared absorbing particles contain Cs4W as a main phase. 11 O 35 Particles obtained by heating and reducing a cesium tungsten oxide precursor in a reducing gas atmosphere at 650°C to 950°C.

10. The near-infrared curable ink composition according to any one of claims 1 to 9, It further contains one or more selected from organic pigments, inorganic pigments, and dyes.

11. The near-infrared curable ink composition according to any one of claims 1 to 10, It further comprises a dispersant.

12. The near-infrared curable ink composition according to any one of claims 1 to 11, It further comprises a solvent. 13 . A near-infrared cured film, which is a cured product of the near-infrared curable ink composition according to claim 1 .

14. A method for producing a near-infrared cured product, comprising the following steps: a coating step of coating a substrate with the near infrared curable ink composition according to any one of claims 1 to 12 to form a coating film, and A curing step of irradiating the coating film with near-infrared rays to cure the near-infrared curable ink composition.

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