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

Abstract

To provide a near-infrared curable ink composition which contains near-infrared absorption particles containing a composite tungsten oxide, and can be set to a more neutral color tone when it is cured.SOLUTION: A near-infrared curable ink composition contains a thermosetting resin or a thermoplastic resin, and near-infrared absorption particles, wherein the near-infrared absorption particles contain a cesium tungstate, the cesium tungstate has a pseudo hexagonal crystal structure modulated to one or more kinds selected from orthorhombic, rhombohedral and cubic crystals, the cesium tungstate is represented by general formula: CsxWyOz, in a ternary composition diagram with Cs, W and O as each apex, and it has a composition in an area surrounded by four straight lines of x=0.6y, z=2.5y, y=5x and Cs2O:WO3=m:n (m and n are integers).SELECTED DRAWING: Figure 1A

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 technology]

[0002] In recent years, ultraviolet-curable paints that are cured using ultraviolet light have become widely known as environmentally friendly paints, as described in, for example, Patent Documents 1 to 6, because they can be printed without heating.

[0003] However, when a composition that undergoes radical polymerization upon irradiation with ultraviolet light is used as a UV-curable ink or paint, the polymerization (curing) is inhibited in the presence of oxygen.On the other hand, when a composition that undergoes cationic polymerization upon irradiation with ultraviolet light is used, there is a problem in that a strong acid is generated during the polymerization.

[0004] Furthermore, in order to improve the light resistance of the resulting printed or coated surface, an ultraviolet absorber is generally added to the printed or coated surface, but when an ultraviolet absorber is added to an ultraviolet-curable ink or paint, there is a problem in that curing by ultraviolet irradiation is inhibited.

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

[0006] Furthermore, the applicant of the present application has disclosed near-infrared curable ink compositions containing composite tungsten oxide in Patent Documents 9 and 10. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 7-100433 [Patent Document 2] Japanese Patent Application Laid-Open No. 2001-146559 [Patent Document 3] Japanese Patent Publication No. 2009-057548 [Patent Document 4] Japanese Patent Publication No. 2012-140516 [Patent Document 5] Japanese Patent Publication No. 2000-037943 [Patent Document 6] Japanese Patent Publication No. 2004-18716 [Patent Document 7] Japanese Patent Publication No. 2008-214576 [Patent Document 8] Japanese Patent Publication No. 2015-131928 [Patent Document 9] International Publication No. 2017 / 047736 [Patent Document 10] International Publication No. 2019 / 054478

Non-licensed literature

[0008]

Non-patent document 1

Non-patent document 2

Non-patent document 3

[0009] However, according to the investigations of the present inventors, the near-infrared-curable compositions described in Patent Documents 7 and 8 above both have the problem of insufficient near-infrared absorption properties.

[0010] In contrast, the composite tungsten oxide microparticles contained in the near-infrared curable ink compositions disclosed in Patent Documents 9 and 10 are materials that have high transmittance and low absorbance for visible light, but low transmittance and high absorbance for light in the near-infrared region. Therefore, near-infrared curable ink compositions containing such composite tungsten oxide microparticles also have excellent near-infrared absorption properties.

[0011] However, composite tungsten oxide microparticles preferentially absorb the long wavelength light of visible light, that is, the red light, so that they are accompanied by blue coloring, and the blue degree becomes stronger with the amount of added microparticles.Therefore, the cured film obtained by incorporating composite tungsten oxide microparticles as near-infrared absorbing component is accompanied by blue coloring, and it is difficult to add other pigments to make it into the yellow system, which is the complementary color of blue, or the pale color other than blue.

[0012] 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 that contain a composite tungsten oxide and that can have a more neutral color tone when cured. [Means for solving the problem]

[0013] In one aspect of the present invention, a thermosetting or thermoplastic resin is used. near-infrared absorbing particles, the near-infrared absorbing particles contain cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated into one or more crystal structures selected from orthorhombic, rhombohedral, and cubic crystal structures; The cesium tungstate has the general formula Cs x W y O z In a ternary composition diagram with Cs, W, and O at the vertices, the ink composition has a composition within the region surrounded by the four straight lines x=0.6y, z=2.5y, y=5x, and CsO:WO=m:n (m and n are integers). [Effects of the Invention]

[0014] One aspect of the present invention can provide a near-infrared curable ink composition that contains near-infrared absorbing particles that contain a composite tungsten oxide and that can have a more neutral color tone when cured. [Brief explanation of the drawings]

[0015] [Figure 1A] Figure 1A is a Cs-WO composition diagram with Cs, W, and O at the vertices. [Figure 1B] Figure 1B is an enlarged view of a portion of the Cs-WO composition diagram with Cs, W, and O at the vertices. [Figure 2] FIG. 2 shows powder XRD diffraction patterns of the near infrared absorbing particles produced in Examples 1 to 6 and Comparative Examples 1 and 2. [Figure 3] FIG. 3 shows powder XRD diffraction patterns of the near infrared absorbing particles produced in Examples 9 to 14. [Figure 4] FIG. 4 shows a transmission electron microscope bright-field image, a selected area electron diffraction image, and a high angle electron dark-field (HAADF) image of the near-infrared absorbing particles produced in Example 1. [Figure 5] FIG. 5 is an explanatory diagram of a near-infrared absorbing particle having a coating. [Figure 6] FIG. 6 is an explanatory diagram of a near-infrared curable ink composition. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments for carrying out the present invention will be described with reference to the 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. [Near-infrared curable ink composition] The methods for producing the near-infrared curable ink composition, near-infrared cured film, and near-infrared cured product according to this embodiment will be described in the following order: [1] near-infrared absorbing particles; [2] a method for producing near-infrared absorbing particles; [3] a near-infrared absorbing particle dispersion; [4] a near-infrared curable ink composition; [5] a method for producing a near-infrared curable ink composition; [6] a near-infrared cured film; a method for producing a near-infrared cured film; and [7] a method for producing a near-infrared cured product. [1] Near-infrared absorbing particles As will be described later, the near-infrared curable ink composition of this embodiment contains near-infrared absorbing particles. Therefore, the near-infrared absorbing particles will be described first.

[0017] The near-infrared absorbing particles contain cesium tungstate, which is a composite tungsten oxide. The near-infrared absorbing particles of this embodiment may also be composed of cesium tungstate. However, even in this case, the inclusion of inevitable impurities is not excluded. (1) Cesium tungstate Cesium tungstate (cesium polytungstate) can have a pseudo-hexagonal crystal structure modified to one or more of orthorhombic, rhombohedral, and cubic crystals, specifically, a modified pseudo-hexagonal structure that is a partial modification of the hexagonal alkali tungsten bronze structure, selected from orthorhombic, rhombohedral, and cubic crystals.

[0018] The transmission color and optical absorption of cesium-doped hexagonal tungsten bronze particles, which have been conventionally used as near-infrared absorbing particles, are determined by their imaginary part of the dielectric function (ε2) and band structure.

[0019] In the visible light energy range (1.6 eV to 3.3 eV), cesium-doped hexagonal tungsten bronze (hereinafter also referred to as Cs-HTB) has a sufficiently large band gap that light absorption in the visible light range is essentially suppressed. Additionally, tungsten dd-orbital transitions and oxygen pp-orbital transitions are forbidden by the Fermi golden rule, reducing the probability of electronic transitions. These two factors result in small values ​​of ε2 at wavelengths in the visible light range. Since ε2 represents the absorption of photons by electrons, a small ε2 at wavelengths in the visible light range results in visible light transmittance. However, it has recently been revealed that absorption due to band-edge transitions exists near the shortest wavelengths in the visible light range (blue), and that localized surface plasmon resonance (LSPR) absorption and polaronic electronic transition absorption exist near the longest wavelengths in the visible light range (Non-Patent Document 1). These factors limit light transmittance in each case.

[0020] As mentioned above, the band gap of Cs-HTB is large enough that the band edge transition exceeds the energy of blue wavelength light, resulting in blue transmittance. Conversely, at red wavelengths, Cs-HTB has a large number of conduction electrons, resulting in strong LSPR absorption and polaronic absorption, and the base of this absorption extends into the red wavelengths, resulting in low red transmittance. Therefore, the transmitted color of a Cs-HTB nanoparticle-dispersed film appears blue due to the balance between these two.

[0021] That is, to neutralize the blue transmission color of Cs-HTB, it is necessary to increase the absorption on the blue side and increase the transmission on the red side.

[0022] Strengthening the blue absorption of Cs-HTB can be achieved, for example, by shifting the absorption position of the band edge transition to lower energy. Shifting the absorption position of the band edge transition to lower energy corresponds to narrowing the band gap of Cs-HTB. Therefore, this can be achieved by selecting a material with a slightly smaller band gap.

[0023] The red absorption of Cs-HTB can be weakened by decreasing the concentration of surface plasmon resonance electrons or polaron-bound electrons.

[0024] Based on the above considerations, the inventors of the present invention have investigated various cesium tungsten oxides, which are oxides containing cesium (Cs) and tungsten (W), and have improved the material by using band structure calculations based on first-principles calculations. As a result, they have found that when the conventional hexagonal crystal structure is modified to an orthorhombic, rhombohedral, or cubic pseudo-hexagonal structure by changing the microstructure, the band structure changes and the amount of free and bound electrons changes, resulting in a change in color.

[0025] Here, a pseudo-hexagonal structure modulated to one or more of the orthorhombic, rhombohedral, and cubic crystals refers to a pseudo-hexagonal crystal in which Cs-rich planes are inserted regularly or randomly into the prism or basal planes of the hexagonal crystal. A Cs-rich plane is synonymous with a plane lacking W or O. Furthermore, as described below, O, OH, OH2, and OH3 ions can substitute for the Cs site, and the introduction of these ions into the prism or basal planes can promote the modulation of the pseudo-hexagonal crystal structure, just like Cs.

[0026] Orthorhombic, rhombohedral, and cubic crystal structures can be identified, for example, by electron diffraction, by noting the symmetry of the diffraction spots when the electron beam is incident along the c-axis, i.e., from the (0001) direction.

[0027] In a hexagonal crystal, the diffraction spots of the three types of prism planes, (10-10), (01-10), and (1-100), appear at the same distance from the incident spot within the reciprocal lattice plane. In other words, the hexagonal crystal has the same crystal plane spacing. Note that the above-mentioned "same distance" includes distances that can be considered to be the same within the error range of the electron diffraction spot distance measurement. For this reason, the hexagonal crystal produces an electron diffraction pattern that is hexagonally symmetric, i.e., invariant to a 60° rotation.

[0028] In the orthorhombic crystal, one type of prism surface spot appears closer to the incident spot than the other two types of prism surface spots, i.e., in the orthorhombic crystal, only one type of prism surface has a long crystal plane spacing.

[0029] In a rhombohedral crystal, the three types of prism surface spots have different crystal plane spacings.

[0030] Cubic crystals have the same hexagonal symmetry as hexagonal crystals, but the cubic symmetry can be easily identified by observing from other crystal zone axis directions.

[0031] In XRD powder patterns, pseudohexagonal crystals are often considered to be a mixed pattern of orthorhombic and hexagonal crystals, or a mixed pattern of rhombohedral and hexagonal crystals, or a mixed pattern of cubic and hexagonal crystals. However, due to the insertion of the planar lattice defects mentioned above, the positions and intensities of the diffraction peaks change slightly.

[0032] One method for obtaining a pseudo-hexagonal crystal structure modulated to one or more types selected from the above-mentioned orthorhombic, rhombohedral, and cubic crystals is to add one or more types of additive components selected from O, OH, OH2, and OH3. Therefore, in the near infrared absorbing particles of the present embodiment, it is preferable that the cesium tungstate contains one or more types of additive components selected from O, OH, OH2, and OH3.

[0033] The one or more additive components selected from O, OH, OH2, and OH3 are preferably present at one or more positions selected from hexagonal windows and hexagonal cavities present in hexagonal tunnels that penetrate the c-axis direction of a hexagon formed by six WO6 octahedra that constitute the hexagonal alkali tungsten bronze structure of a cesium tungstate crystal, and triangular cavities formed by three WO6 octahedra.

[0034] The hexagonal tunnel has two voids: the large hexagonal cavity and the hexagonal window. The hexagonal window is the second largest void in the hexagonal crystal after the hexagonal cavity and is surrounded by six oxygen atoms that make up the WO6 octahedron. The hexagonal window is adjacent to the Cs ions located in the hexagonal cavity above and below it in the c-axis direction. The trigonal cavity is the next largest void after the hexagonal window and penetrates the hexagonal crystal along the c-axis direction. One or more of O, OH, OH2, and OH3 can enter the hexagonal cavity by substituting for Cs, but they also invade the hexagonal window when there is a sufficient amount of Cs or when there is a large amount of invaded water. In some cases, they invade the trigonal cavity at the bottom or the cavities on the prism surface in parallel with the hexagonal window void, replacing Cs. The addition of the above-mentioned additives creates defects on the base and prism surfaces, which shifts the crystal structure from hexagonal to orthorhombic, rhombohedral, and then cubic, narrowing the band gap and reducing the conduction band electron density. As a result, cesium tungstate, which has a pseudo-hexagonal crystal structure, can enhance absorption on the blue side and transmission on the red side compared to Cs-HTB, neutralizing blue transmission colors.

[0035] In this case, the orthorhombic, rhombohedral, and cubic crystals can be considered pseudo-hexagonal crystals, which have atomic arrangements similar to those of hexagonal tungsten bronze, but have a different symmetry from hexagonal crystals. Roughly speaking, without being too strict, the orthorhombic crystals in this case are crystals in which hexagonal symmetry is broken by inserting, regularly or randomly, planes lacking W and O atoms into one of the three prism faces of a hexagonal crystal. Therefore, in an orthorhombic crystal, only one prism face has a longer interplanar spacing. Using this, modulation to an orthorhombic crystal can be easily identified, for example, by the (0001) electron diffraction pattern.

[0036] In this case, a rhombohedron is formed by inserting a plane that accepts excess Cs into the basal surface of a hexagonal crystal, i.e., a plane lacking W and O, and by systematically displacing the stacking of the basal surface in the c-axis direction, breaking the hexagonal symmetry. In this case, the excess Cs plane includes not only displacement on the plane but also expansion in the direction perpendicular to the plane, resulting in a change in the prism plane spacing and a change in the c-axis lattice constant. Therefore, in a rhombohedron, all three prism planes have different spacings. Utilizing this, modulation to a rhombohedron can be easily identified, for example, by the (0001) electron diffraction pattern.

[0037] Furthermore, when the three axes of the rhombohedron intersect at 90 degrees, it becomes a cubic crystal. This cubic crystal has a pyrochlore structure, and a typical composition is CsW2O6.

[0038] Therefore, voids corresponding to the above-mentioned hexagonal windows, hexagonal cavities, and trigonal cavities are also inherited by orthorhombic crystals, rhombohedral crystals, and cubic crystals. Therefore, the hexagonal windows, hexagonal cavities, and trigonal cavities in the cesium tungstate contained in the near infrared absorbing particles of the present embodiment also refer to the corresponding voids in the orthorhombic crystals, rhombohedral crystals, and cubic crystals (pyrochlore phase).

[0039] Hereinafter, a structural example of the method for producing near infrared absorbing particles of this embodiment will be described, mainly taking as an example the case of a hexagonal window as a site or gap where O, OH, OH2, and OH3 can be substituted or penetrated.

[0040] One method for obtaining orthorhombic, rhombohedral, or cubic crystals in which one or more species selected from O, OH, OH2, and OH3 are present in the hexagonal window is to crystallize the cesium tungstate in saturated water vapor during crystallization during synthesis. Generally, in a Cs-HTB structure, the ionic radius of Cs is slightly larger than the hexagonal cavity, making it difficult for Cs to move. Therefore, once crystallized into a hexagonal crystal, it becomes difficult to diffuse and insert oxygen atoms or the like into the hexagonal window through subsequent heat treatment or the like. Therefore, we devised a method in which the atmosphere is filled with saturated water vapor before the cesium tungstate crystallizes, and water molecules and O, OH, and OH3 ions derived from the water molecules are inserted into the hexagonal window simultaneously with the crystallization of the cesium tungstate. Therefore, as described below, the method for producing near-infrared absorbing particles of this embodiment preferably includes a step of introducing water vapor at a heating temperature close to the crystallization temperature of the cesium tungstate and crystallizing the cesium tungstate in an atmosphere containing water vapor. When near-infrared absorbing fibers are produced using the near-infrared absorbing particles synthesized through the above steps, or near-infrared absorbing particles that have been further heat-treated in a reducing atmosphere as necessary, the blueness of the color tone can be reduced while the near-infrared absorbing effect is sufficiently maintained, i.e., a neutral color tone can be achieved.

[0041] On the other hand, once hexagonal cesium tungstate crystals are produced, heating the cesium tungstate in a water vapor atmosphere or maintaining and heating it in a high-temperature, high-humidity environment does not neutralize the transmitted color. This is because elements with a large ionic radius, such as Cs, inhibit the diffusion of oxygen atoms and other atoms through hexagonal tunnels, so once the crystals are crystallized into hexagonal crystals, subsequent heat treatments make it difficult for oxygen atoms and other atoms to diffuse into the hexagonal windows of the voids. Therefore, the heat treatment in water vapor must be performed during the initial crystallization process.

[0042] When heating in an atmosphere containing water vapor during crystallization, it is also possible to simultaneously mix in a reducing gas such as hydrogen gas and crystallize in a reducing gas atmosphere. Furthermore, if the crystals are once crystallized in a water vapor atmosphere, they can be further heated at a high temperature of 500°C to 950°C in an atmosphere containing a reducing gas such as hydrogen gas, or in an inert gas atmosphere. In either case, near-infrared absorbing particles with a neutralized transmitted color and a high near-infrared absorption effect can be obtained. By heating at 500°C or higher, the arrangement of equilibrium atomic positions, such as an orthorhombic crystal structure containing defects, is sufficiently promoted, thereby enhancing the near-infrared absorption effect. Furthermore, by heating at 950°C or lower, the speed of crystal structure change can be maintained at an appropriate level, allowing for easy control of the appropriate crystalline state and electronic state. Note that heating at temperatures higher than 950°C, for example, excessive reduction, may result in the production of lower oxides such as W metal and WO2, which is undesirable from this perspective.

[0043] During the initial crystallization by heating with water vapor, the incorporation of O, OH, OH2, and OH3 results in the formation of one or more crystal types selected from orthorhombic, rhombohedral, and cubic (pyrochlore phase) crystals, which are microscopically modified from hexagonal crystals. By heating these in atmospheres with different degrees of reduction, one or more crystal structures selected from various orthorhombic, rhombohedral, and cubic crystals with different amounts and distributions of lattice defects are generated.

[0044] The cesium tungstate contained in the near infrared absorbing particles of the present embodiment may have lattice defects of Cs, W, or O. The reason why lattice defects of Cs, W, or O are introduced into the cesium tungstate will be described below.

[0045] Hexagonal Cs 0.33 At compositions around WO3, crystal stability is determined by the balance between structural stability due to high crystal symmetry and charge balance stability, where charge transfer between elements produces overall charge neutrality. For example, the charge-neutral 2Cs2O·11WO3=Cs4W 11 O 35is considered to be a thermodynamically stable phase, but when heated in a reducing atmosphere, it easily transforms into a hexagonal Cs with high crystal symmetry. 0.32 WO 3-y (Non-Patent Document 2) 0.32 WO 3-y is a metastable structure with high crystal symmetry, while Cs4W 11 O 35 is a stable composition in terms of charge balance. 11 O 35 has poor symmetry in the atomic arrangement within the crystal. For example, in the model by Solodovnikov (Non-Patent Document 3), in the hexagonal arrangement of WO6 octahedra, the same as in hexagonal tungsten bronze, planes with missing W and O atoms are inserted at a b / 8 pitch in the hexagonal (1,1,-2,0) plane (= orthorhombic (010) plane) of the orthorhombic unit cell, resulting in an orthorhombic crystal as a whole. In other words, the Cs, W, and O defects were inevitably introduced to locally satisfy both the crystal structure and charge balance, and have actually been observed recently using TEM and XRD (Non-Patent Document 4).

[0046] In the near-infrared absorbing particles of this embodiment, in the orthorhombic, rhombohedral, or cubic crystals in which O, OH, OH2, or OH3 is incorporated into the hexagonal windows, hexagonal cavities, or trigonal cavities, the local charge balance is disturbed, and the crystal microstructure is further modified. + and H3O + are introduced into the crystal, but these ions are Cs + and W 6+ In order to compete with the OH atoms, local charge neutrality is achieved by the vacancies of Cs and W. As a result, lattice defects including vacancies of Cs and W are introduced. O, OH, OH2, and OH3 may invade not only the hexagonal windows but also the trigonal cavities. Furthermore, OH2 and OH3 may substitute for the alkali element (Cs) in the hexagonal cavity, and when the charge-neutral OH2 is substituted, the alkali ion (Cs) that was originally present may be vacant. + ) no longer emits electrons, so the conduction band electrons in the crystal decrease.

[0047] Among the cesium tungstates having a pseudo-hexagonal crystal structure modulated to one or more types selected from orthorhombic, rhombohedral, and cubic crystals, those that satisfy excellent near-infrared absorption effects and visible light transmittance have a predetermined composition.

[0048] Figure 1A shows a ternary composition diagram 10 with Cs-WO as the three vertices. Figure 1B shows an enlarged view of the region 11 in the ternary composition diagram 10 of Figure 1A, with CsWO3, W2O3, and WO4 as the vertices. It should be noted that this diagram is not a phase diagram showing the thermodynamic equilibrium phases, but rather a convenient composition diagram showing the range of compositions in this system. Therefore, CsWO3, W2O3, WO4, etc. are compositions shown for convenience, and it does not refer to whether these are actually obtained compounds.

[0049] The cesium tungstate contained in the near infrared absorbing particles of the present embodiment is represented by the general formula Cs x W y O z In a ternary composition diagram represented by the formula (1), with Cs, W, and O at the vertices, it is preferable that the composition be within the region surrounded by the four lines x=0.6y, z=2.5y, y=5x, and Cs2O:WO3=m:n (m and n are integers). Specifically, in the ternary composition diagram shown in Figures 1A and 1B, it is preferable that the composition be within region 16 surrounded by line 12 satisfying x=0.6y, line 13 satisfying z=2.5y, line 14 satisfying y=5x, and line 15 satisfying Cs2O:WO3=m:n (m and n are integers). Note that region 16 also includes points on lines 12 to 15. Moreover, a line 15 that satisfies Cs2O:WO3=m:n (m and n are integers) is a line that connects Cs2O and WO3 in the ternary composition diagram 10, as shown in FIG. 1A.

[0050] In the above ternary composition diagram, when x > 0.6y, cesium tungstate has a predominantly tetragonal crystal structure, resulting in the loss of near-infrared absorption. Furthermore, when z < 2.5y, cesium tungstate has a hexagonal structure with lower W oxides mixed in, significantly impairing its near-infrared absorption and visible light transmittance. When y > 5x, cesium tungstate has a crystal structure called intergrowth, in which WO3 is mixed into the hexagonal substructure, resulting in the loss of near-infrared absorption. Furthermore, if the Cs2O:WO3 ratio falls to the O-rich side (to the right of line 15, where the Cs2O:WO3 ratio is an integer), no near-infrared absorption effect is obtained. Therefore, it is preferable for cesium tungstate to satisfy the aforementioned range.

[0051] The cesium tungstate contained in the near-infrared absorbing particles of this embodiment may have defects in each of the elements cesium, tungsten, and oxygen, but the atomic ratio (x / y) of cesium to tungsten may be in the range of 0.2 or more and 0.6 or less. That is, the near-infrared absorbing particles of this embodiment have defects in part of one or more elements selected from Cs and W that constitute the crystal of the cesium tungstate, and are represented by the general formula Cs x W y O z It is preferable that x and y satisfy the relationship 0.2≦x / y≦0.6.

[0052] Cesium and tungsten supply electrons to the crystal, so by setting x / y to 0.2 or more, near-infrared absorption function can be improved. Furthermore, by setting x / y to 0.2 or more, it is possible to create a hexagonal crystal structure or a crystal structure in which the hexagonal crystal is modulated. When x / y exceeds 0.33, Cs ions cannot fit into the hexagonal cavity and begin to occupy the trigonal cavity as well, causing modulations on the prism faces and bases, gradually changing locally into a layered structure of orthorhombic, rhombohedral, or cubic pyrochlore. Furthermore, when x / y exceeds 0.6, the tetragonal Cs2W3O 10 The crystal structure changes to the above, which significantly impairs the visible light transmittance and reduces the usefulness.

[0053] The near-infrared absorbing particles of this embodiment have a hexagonal cesium tungsten bronze structure Cs 0.33 Using WO3 as a base, the WO6 octahedra that make up the crystal can have defects in at least some of the W. These W defects are introduced as planar defects mainly on the hexagonal prism faces or bases, but because the ionic repulsion of the atomic rows on both sides of the defect plane increases the interplanar spacing, the crystal symmetry changes from hexagonal to orthorhombic, rhombohedral, or cubic.

[0054] The near-infrared absorbing particles of this embodiment can have vacancies in at least some of the O atoms in the WO octahedra that make up the cesium tungstate crystal, based on the hexagonal alkali tungsten bronze structure CsW3O9. These O vacancies are introduced randomly, and the vacancies can supply localized electrons to the system, enhancing the near-infrared absorbing function. The known hexagonal tungsten bronze Cs 0.32 WO 3-y In the near-infrared absorbing particles of this embodiment, it is known that the vacancy rate is y=0.46 or up to 15% of all the lattice points of O constituting the octahedron (Non-Patent Document 3). When the vacancy rate exceeds 0.5, the crystal becomes unstable, a different phase is generated, and decomposition occurs. The cesium tungstate Cs contained in the near-infrared absorbing particles of this embodiment x W y O z In this case, it is possible to include an O vacancy amount equivalent to a maximum z / y = 2.5. However, when excess O, OH, OH2, or OH3 is introduced into voids such as hexagonal windows, it is important to note that the identified O value obtained by chemical analysis includes these excess amounts.

[0055] In the cesium tungstate contained in the near infrared absorbing particle of the present embodiment, a part of Cs may be substituted with an additional element. In this case, the additional element is preferably one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0056] These added elements have electron donating properties and assist in donating electrons to the conduction band of the WO octahedral framework at the Cs site. (2) Moisture and heat resistance of near-infrared absorbing particles The near-infrared absorbing particles of this embodiment exhibit improved moist heat resistance compared to cesium-doped hexagonal tungsten bronze. This effect is reasonable considering that a portion of the near-infrared absorbing particles of this embodiment contains one or more types of crystals selected from orthorhombic, rhombohedral, and cubic (pyrochlore) phases modulated by interstitial substitution with O, OH, OH2, and OH3. In other words, humidity and moisture degradation of cesium-doped hexagonal tungsten bronze is essentially a substitution reaction between Cs and water molecules. However, when the cavities and windows of the hexagonal tunnels, which are the main oxygen diffusion pathways, are filled with Cs, O, OH, OH2, and OH3, this substitution reaction is significantly slowed down. Therefore, the near-infrared absorbing particles of this embodiment not only suppress the loss of near-infrared absorbing function in high-humidity environments, but also slow down atmospheric moisture-mediated degradation reactions in high-temperature heat resistance tests at normal humidity, thereby improving moist heat resistance. (3) Average particle size of near-infrared absorbing particles The average particle size of the near-infrared absorbing particles of this embodiment is not particularly limited, but is preferably 0.1 nm or more and 200 nm or less. This is because, by setting the average particle size of the near-infrared absorbing particles to 200 nm or less, localized surface plasmon resonance is more pronounced, thereby particularly enhancing the near-infrared absorption characteristics, i.e., particularly suppressing the solar transmittance. Furthermore, setting the average particle size of the near-infrared absorbing particles to 0.1 nm or more facilitates industrial production. Furthermore, particle size is closely related to the color of the near-infrared curable ink composition and the near-infrared cured film. In the particle size range where Mie scattering is dominant, the smaller the particle size, the less scattering of short wavelengths in the visible light region. Therefore, while increasing the particle size has the effect of suppressing the blue hue, an average particle size exceeding 200 nm suppresses the generation of surface plasmons and reduces LSPR absorption. Therefore, by setting the average particle size of the near-infrared absorbing particles to 200 nm or less, the color of the near-infrared curable ink composition and the near-infrared cured film can be made particularly neutral while maintaining a certain level of LSPR absorption.

[0057] Here, the average particle size of the near-infrared absorbing particles can be known from the median size of a plurality of near-infrared absorbing particles measured from a transmission electron microscope image, or the dispersed particle size measured with a particle size measuring device based on a dynamic light scattering method of a dispersion liquid.

[0058] In particular, when the film is applied to an application in which transparency in the visible light region is important, it is preferable to further consider reducing scattering by near-infrared absorbing particles. When the reduction in scattering is important, it is particularly preferable that the average particle size of the near-infrared absorbing particles is 30 nm or less.

[0059] The average particle size refers to the particle size at 50% of the cumulative value in the particle size distribution, and the same meaning applies to the average particle size in other parts of this specification. A method for measuring particle size distribution to calculate the average particle size can be, for example, direct measurement of the particle size of each particle using a transmission electron microscope. The average particle size can also be measured using a particle size measuring device based on the dynamic light scattering method of the dispersion liquid, as described above. (4) Optional configuration of near-infrared absorbing particles The near-infrared absorbing particles may be subjected to a surface treatment for purposes such as surface protection, improved durability, oxidation prevention, and improved water resistance. The specific content of the surface treatment is not particularly limited. For example, as shown in FIG. 5 , the near-infrared absorbing particles of this embodiment may have a coating 51 on a surface 50A of a near-infrared absorbing particle 50. Specifically, the surface of the near-infrared absorbing particle 50 may be coated with a coating 51 of a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. That is, the near-infrared absorbing particles may have a coating of the above-mentioned compound. In this case, examples of the compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn include one or more selected from oxides, nitrides, carbides, and the like.

[0060] 5 merely schematically illustrates the shape of the near-infrared absorbing particle, and is not limited to such a shape. For example, the near-infrared absorbing particle 50 may be irregularly shaped instead of spherical. The coating 51 does not need to completely cover the surface 50A of the near-infrared absorbing particle 50, and may be disposed so as to cover only a portion of the surface 50A. Furthermore, the thickness of the coating 51 may vary depending on the location on the surface 50A of the near-infrared absorbing particle 50. [2] Manufacturing method for near-infrared absorbing particles Next, a structural example of the method for producing near-infrared absorbing particles according to this embodiment will be described. Since the method for producing near-infrared absorbing particles according to this embodiment can produce the near-infrared absorbing particles described above, a part of the description will be omitted.

[0061] The method for producing near-infrared absorbing particles is not particularly limited, and any method can be used as long as it can produce near-infrared absorbing particles that satisfy the above-mentioned properties. Here, one configuration example of the method for producing near-infrared absorbing particles will be described. (1) First heat treatment process The method for producing near-infrared absorbing particles of the present embodiment can include, for example, the following steps.

[0062] A first heat treatment step in which a compound raw material containing Cs and W is heated at 400°C or higher and 650°C or lower in an atmosphere containing water vapor or an atmosphere containing water vapor and a reducing gas.

[0063] In the first heat treatment step, the cesium tungstate can be crystallized by heating at 400° C. or higher and 650° C. or lower.

[0064] However, in order to make cesium tungstate a pseudo-hexagonal crystal, it is preferable to have sufficient water vapor in the atmosphere when the cesium tungstate crystallizes, i.e., when the WO6 units form hexagonal crystals with Cs. During this crystallization process, Cs is mainly taken up into the hexagonal cavities, and water molecules or its decomposition product, OH3 + , O.H. - and O 2-is mainly taken up in the hexagonal windows. When the composition contains a relatively large amount of Cs or water molecules, Cs or water molecules are also taken up in the three-sided cavities.

[0065] The compound raw material containing Cs and W can be a mixture of a compound raw material containing Cs and a compound raw material containing W. The compound raw material containing Cs and W can be any material containing Cs and W, and for example, a mixture of Cs2CO3 and WO3 can be used.

[0066] However, the purpose of the crystallization process in the first heat treatment step is to incorporate water molecules, OH, O, etc. into the crystals during crystallization. Therefore, it is preferable not to use cesium tungsten oxides that already form a hexagonal crystal structure, such as crystal powders of nCs2O·mWO3 (n and m are integers, 3.6≦m / n≦9.0), as the compound raw material containing Cs and W. It is also preferable not to use cesium tungstates obtained by other methods, such as the sol-gel method or complex polymerization method, non-equilibrium cesium tungstates obtained by gas-phase synthesis, or powders obtained by thermal plasma or electron beam melting. In raw materials that already form a hexagonal crystal structure, Cs inhibits the diffusion of oxygen atoms, making it difficult for water molecules to be incorporated into the crystals. In other words, it is preferable not to use cesium tungstates with a hexagonal crystal structure as the compound raw material containing Cs and W.

[0067] The supply of water vapor during the crystallization process of the first heat treatment step is preferably achieved by, for example, supplying superheated water vapor into a heating furnace. Superheated water vapor is high-enthalpy water vapor obtained by further heating saturated water vapor vaporized at 100°C to a temperature above 100°C, and may be supplied together with a carrier gas. When the carrier gas is an inert gas, an atmosphere nearly free of oxygen is formed. Superheated water vapor may be supplied at 400°C or above, at which point crystallization becomes active, but it is preferable to supply it from a temperature sufficiently low before crystallization. A mixture of superheated water vapor and an inert gas, or a mixture of superheated water vapor, an inert gas, and a reducing gas such as hydrogen, may also be supplied. When a reducing gas is mixed, the rate of hexagonal crystal arrangement tends to increase, and even if the same orthorhombic, rhombohedral, or cubic crystal is used, different microscopic defect structures may be obtained.

[0068] In the first heat treatment step, heating may be performed in an atmosphere not containing water vapor, such as an inert atmosphere, before or after crystallization of the cesium tungstate.

[0069] The method for producing near infrared ray absorbing particles of the present embodiment may further include an optional step. (2) Second heat treatment process The method for producing near infrared absorbing particles of this embodiment may also include, after the first heat treatment step, a second heat treatment step of heating at a temperature of 500° C. or more and 950° C. or less in an atmosphere containing a reducing gas.

[0070] The second heat treatment process involves heating and reducing the material powder that has undergone the first heat treatment process at a temperature between 500°C and 950°C. This process stabilizes the orthorhombic, rhombohedral, and cubic crystals, which have defect structures, by annealing. The high-temperature reduction process also serves to remove some of the oxygen in the WO6 octahedra. The reduction and removal of the octahedral oxygen generates bound electrons on adjacent W atoms, resulting in a structural treatment that enhances near-infrared absorption properties.

[0071] When performing the thermal reduction treatment, it is preferable to perform it under a stream of a reducing gas. As the reducing gas, a mixed gas containing a reducing gas such as hydrogen and one or more inert gases selected from nitrogen, argon, etc. can be used. Alternatively, heating in a water vapor atmosphere or a vacuum atmosphere or other mild heating and reduction conditions may be used in combination.

[0072] The second heat treatment step may be composed of a plurality of steps, and after the heating in the reducing gas atmosphere, heating in an inert gas atmosphere may be further carried out.

[0073] Furthermore, in the second heat treatment step, if partial removal of oxygen from the WO octahedra is not intended, heating can be performed in an inert gas atmosphere instead of the reducing gas atmosphere within the above temperature range. That is, the second heat treatment step can be performed in an inert gas atmosphere or a reducing gas atmosphere at a temperature of 500°C to 950°C.

[0074] As described above, the method for producing the near-infrared absorbing particles of the present embodiment is not particularly limited. As the method for producing the near-infrared absorbing particles, various methods that can form a predetermined structure including a defect microstructure can be used.

[0075] The near-infrared absorbing particles may be produced by synthesizing a tungstate by a solid phase method, a liquid phase method, or a gas phase method in an atmosphere in which water molecules coexist. (3) Crushing process As described above, the near-infrared absorbing particles are preferably pulverized into fine particles, and therefore the method for producing near-infrared absorbing particles may also include a pulverization step of pulverizing the powder obtained in the first heat treatment step and the second heat treatment step.

[0076] The specific means for pulverizing and pulverizing is not particularly limited, and various means capable of mechanical pulverization can be used. As the mechanical pulverization method, a dry pulverization method using a jet mill or the like can be used. Furthermore, mechanical pulverization may be performed in a solvent in the process of obtaining a near-infrared absorbing particle dispersion liquid described below.

[0077] If necessary, further sieving or the like can be carried out. (4) Coating process As described above, the surface of the near infrared absorbing particle may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. Therefore, the method for producing the near infrared absorbing particle may further include, for example, a coating step of coating the near infrared absorbing particle with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn.

[0078] In the coating step, the specific conditions for coating the surfaces of the near infrared absorbing particles are not particularly limited. For example, a coating step may be included in which an alkoxide containing one or more metals selected from the above metal group is added to the near infrared absorbing particles to be coated, and a film is formed on the surfaces of the near infrared absorbing particles. [3] Near-infrared absorbing particle dispersion Next, a configuration example of the near-infrared absorbing particle dispersion liquid of this embodiment will be described.

[0079] The near-infrared absorbing particle dispersion of this embodiment can also be used, for example, when producing a near-infrared curable ink composition described below.

[0080] The near-infrared absorbing particle dispersion of the present embodiment can contain the above-described near-infrared absorbing particles and one or more liquid mediums selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers. The near-infrared absorbing particle dispersion preferably has a configuration in which near-infrared absorbing particles are dispersed in a liquid medium.

[0081] As described above, the liquid medium may be one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers.

[0082] As the organic solvent, various types can be selected, such as alcohols, ketones, esters, hydrocarbons, and glycols. Specific examples of the solvent include one or more selected from the group consisting of alcohol solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, 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, dimethylacetamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; and halogenated hydrocarbons such as ethylene chloride and chlorobenzene.

[0083] However, among these, organic solvents with low polarity are preferred, and in particular, 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.

[0084] Examples of fats and oils that can be used include 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 esterifying fatty acids of vegetable oils with monoalcohols; ethers; and petroleum solvents such as Isopar (registered trademark) E, Exxor (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, and D130 (all manufactured by ExxonMobil).

[0085] As the liquid resin, for example, one or more types selected from liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc. can be used.

[0086] As the liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0087] The components contained in the near-infrared absorbing particle dispersion are not limited to the near-infrared absorbing particles and the liquid medium described above. The near-infrared absorbing particle dispersion may further contain any optional components added thereto, as necessary.

[0088] For example, an acid or alkali may be added to the near-infrared absorbing particle dispersion liquid as needed to adjust the pH of the dispersion liquid.

[0089] In addition, in order to further improve the dispersion stability of the near infrared absorbing particles in the near infrared absorbing particle dispersion liquid described above and to prevent the dispersed particle size from becoming coarse due to re-aggregation, various surfactants, coupling agents, and the like may be added to the near infrared absorbing particle dispersion liquid as dispersants.

[0090] The dispersant, such as the surfactant or coupling agent, can be selected depending on the application, but it is preferable that the dispersant has one or more functional groups selected from an amine-containing group, a hydroxyl group, a carboxyl group, and an epoxy group. These functional groups adsorb to the surface of the near-infrared absorbing particles to prevent aggregation and have the effect of uniformly dispersing the near-infrared absorbing particles, for example, in an infrared shielding film formed using the near-infrared absorbing particles. It is more preferable that the dispersant is a polymeric dispersant having one or more functional groups selected from the above functional groups (functional groups) in the molecule.

[0091] Suitable commercially available dispersants include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, and 250 (available from The Lubrizol Chemical Company, Ltd.). Manufactured by EFKA 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, 8503 (manufactured by Efka Additives), Ajisper (registered trademark) PA111, PB821, PB822, PN411, Famex L-12 (manufactured by 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 (manufactured by Pick Chemie Japan Co., Ltd.), Disparlon (registered trademark) Examples of the acrylic acid ester include one or more selected from 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.), Alphon (registered trademark) UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), and the like.

[0092] The method for dispersing the near-infrared absorbing particles in a liquid medium is not particularly limited as long as it can disperse the near-infrared absorbing particles in the liquid medium. In this case, it is preferable that the near-infrared absorbing particles be dispersed so that their average particle size is 200 nm or less, and more preferably 0.1 nm or more and 200 nm or less.

[0093] Examples of methods for dispersing near-infrared absorbing particles in a liquid medium include dispersion methods using devices such as a bead mill, a ball mill, a sand mill, a paint shaker, and an ultrasonic homogenizer. Among these, pulverization and dispersion using a media agitation mill such as a bead mill, a ball mill, a sand mill, or a paint shaker that uses a medium media (beads, poles, or Ottawa sand) is preferred from the viewpoint of shortening the time required to achieve a desired average particle size. By using a media agitation mill, the near-infrared absorbing particles are dispersed in a liquid medium, and at the same time, microparticulation due to collisions between the near-infrared absorbing particles and collisions between the medium and the near-infrared absorbing particles also progresses, allowing the near-infrared absorbing particles to be dispersed in a more microparticulate form. That is, a pulverization-dispersion process is performed.

[0094] As described above, the average particle size of the near-infrared absorbing particles is preferably 0.1 nm or more and 200 nm or less. This is because a small average particle size reduces scattering of light in the visible light region with wavelengths of 400 nm or more and 780 nm or less due to geometric scattering or Mie scattering. As a result of this reduced light scattering, for example, a near-infrared absorbing particle dispersion obtained using the near-infrared absorbing particle dispersion of this embodiment, in which near-infrared absorbing particles are dispersed in a resin or the like, can be prevented from becoming like frosted glass, thereby preventing clear transparency from being obtained. That is, when the average particle size is 200 nm or less, the light scattering mode weakens from the geometric scattering or Mie scattering mode and shifts to the Rayleigh scattering mode. In the Rayleigh scattering region, scattered light is proportional to the sixth power of the dispersed particle size, so scattering decreases as the dispersed particle size decreases, thereby improving transparency. Furthermore, an average particle size of 100 nm or less is preferable because scattered light is significantly reduced.

[0095] Incidentally, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion obtained by using the near-infrared absorbing particle dispersion of the present embodiment, in which the near-infrared absorbing particles are dispersed in a solid medium such as a resin, does not cause aggregation of particles having a particle size smaller than the average particle size of the near-infrared absorbing particles in the dispersion, as long as a known method for adding the dispersion to the solid medium is used.

[0096] Furthermore, when the average particle size of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less, it is possible to prevent the near-infrared absorbing particle dispersion and its molded product (plate, sheet, etc.) from being produced as grayish with monotonically decreasing transmittance.

[0097] 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, 0.01% by mass or more and 80% by mass or less. This is because a sufficient solar radiation absorptivity can be exhibited by setting the content of the near-infrared absorbing particles to 0.01% by mass or more. Also, by setting the content to 80% by mass or less, the near-infrared absorbing particles can be uniformly dispersed in the dispersion medium. [4] Near-infrared curable ink composition The near-infrared curable ink composition according to this embodiment will be described.

[0098] The near-infrared curable ink composition of this embodiment can contain a thermosetting resin or a thermoplastic resin, and near-infrared absorbing particles. That is, as shown in Fig. 6, for example, a near-infrared curable ink composition 60 of this embodiment can contain the above-described near-infrared absorbing particles 61 and a resin component 62 that is a thermosetting resin or a thermoplastic resin. The near-infrared absorbing particles 61 are preferably dispersed in the resin component 62.

[0099] 6 is a schematic diagram, and the near-infrared curable ink composition of this embodiment is not limited to this form. For example, in FIG. 6, the near-infrared absorbing particles 61 are depicted as spherical particles, but the shape of the near-infrared absorbing particles 61 is not limited to this form and can have any shape. The near-infrared curable ink composition 60 can also contain other additives as needed, in addition to the near-infrared absorbing particles 61 and the resin component 62.

[0100] The near-infrared absorbing particles may be the same as those described above. Therefore, the near-infrared absorbing particles may contain cesium tungstate. Cesium tungstate has a specific crystal structure, for example, a general formula Cs x Wy O z In a ternary composition diagram with Cs, W, and O at the vertices, the composition falls within the region surrounded by the four lines x=0.6y, z=2.5y, y=5x, and Cs2O:WO3=m:n (m and n are integers). Note that the thermosetting resin can be in an uncured state, specifically in a fluid state.

[0101] The components contained in the near-infrared curable ink composition of this embodiment will be described below. (1) Resin component The near-infrared curable ink composition of this embodiment can contain a resin component, specifically a thermosetting resin or a thermoplastic resin. (1-1) Thermosetting resins The thermosetting resin is not particularly limited, but for example, one or more types selected from epoxy resin, urethane resin, acrylic resin, urea resin, melamine resin, phenol resin, ester resin, polyimide resin, silicone resin, unsaturated polyester resin, etc. can be used.

[0102] These thermosetting resins are uncured resins that are cured by the application of thermal energy from near-infrared absorbing particles irradiated with near-infrared rays. The thermosetting resins may contain monomers or oligomers that form the thermosetting resin through a curing reaction, and a known curing agent that is added as needed. Furthermore, a known curing accelerator may be added to the curing agent. (1-2) Thermoplastic resins The thermoplastic resin may be one or more selected from polyester resin, polycarbonate resin, acrylic resin, polystyrene resin, polyamide resin, vinyl chloride resin, olefin resin, fluororesin, polyvinyl acetate resin, thermoplastic polyurethane resin, acrylonitrile butadiene styrene resin, polyvinyl acetal resin, acrylonitrile-styrene copolymer resin, ethylene-vinyl acetate copolymer resin, etc.

[0103] These thermoplastic resins are melted by the thermal energy from the near-infrared absorbing particles irradiated with near-infrared rays, and then hardened into a desired shape by cooling. (2) Near-infrared absorbing particles As the near-infrared absorbing particles, the near-infrared absorbing particles already described can be used. Since the near-infrared absorbing particles have already been described, a description thereof will be omitted here.

[0104] The content of the near-infrared absorbing particles in the near-infrared curable ink composition of this embodiment is not particularly limited, and can be selected depending on the properties required of the near-infrared curable ink composition.

[0105] The amount of near-infrared absorbing particles contained in the near-infrared curable ink composition of this embodiment may be selected and added in an amount that allows the uncured thermosetting resin to be cured during the curing reaction. Also, the amount of near-infrared absorbing particles contained in the near-infrared curable ink composition of this embodiment may be selected and added in an amount that allows the thermoplastic resin to dissolve during the thermal dissolution reaction.

[0106] Therefore, the amount of near-infrared absorbing particles per applied area of ​​the near-infrared curable ink composition can be selected and determined taking into consideration the application thickness when applying the near-infrared curable ink composition.

[0107] The method for dispersing the near-infrared absorbing particles in the near-infrared curable ink composition is not particularly limited, but it is preferable to use a wet medium mill or the like. (3) Other ingredients The near-infrared curable ink composition of this embodiment can be composed only of the above-mentioned resin component and near-infrared absorbing particles, but can also contain any optional components, such as pigments, dyes, dispersants, solvents, etc., which will be described below, depending on the purpose. Note that even when the near-infrared curable ink composition is composed only of a resin component and near-infrared absorbing particles as described above, this does not exclude the inclusion of unavoidable components, etc., that are mixed in during the manufacturing process. (3-1) Pigments and dyes As described above, the near-infrared curable ink composition of this embodiment may further contain one or more pigments selected from organic pigments, inorganic pigments, and dyes in order to color the ink composition. (3-1-1) Pigments The pigment is not particularly limited, and known pigments can be used without particular limitation. One or more pigments selected from organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as carbon black can be preferably used.

[0108] These pigments are preferably present in a dispersed state in the near-infrared curable ink composition of this embodiment. As a method for dispersing these pigments, any known method can be used without any particular limitation.

[0109] The insoluble pigment is not particularly limited, but examples thereof include azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, and diketopyrrolopyrrole.

[0110] Although there are no particular limitations on the organic pigment, the following specific pigments can be preferably used.

[0111] Examples of pigments 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.

[0112] 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.

[0113] Examples of pigments for green or cyan 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.

[0114] Examples of black pigments include CI Pigment Black 1, CI Pigment Black 6, and CI Pigment Black 7.

[0115] The inorganic pigment is not particularly limited either, but preferred examples include carbon black, titanium dioxide, zinc sulfide, zinc oxide, zinc phosphate, mixed metal oxide phosphate, iron oxide, manganese iron oxide, chromium oxide, ultramarine, nickel or chromium antimony titanium oxide, cobalt oxide, aluminum, aluminum oxide, silicon oxide, silicates, zirconium oxide, mixed oxides of cobalt and aluminum, molybdenum sulfide, rutile mixed phase pigments, rare earth sulfides, bismuth vanadate, and extender pigments made of aluminum hydroxide or barium sulfate.

[0116] The average dispersed particle diameter of the dispersed pigment contained in the near-infrared curable ink composition according to this embodiment is not particularly limited, but is preferably, for example, 1 nm or more and 100 nm or less. This is because if the average dispersed particle diameter of the pigment dispersion is 1 nm or more and 100 nm or less, the storage stability of the near-infrared curable ink composition is particularly good. The average dispersed particle diameter can be measured, for example, using an ELS-8000 manufactured by Otsuka Electronics Co., Ltd., which is a particle size measuring device based on the dynamic light scattering method. (3-1-2) Dye There are no particular limitations on the dye, and either oil-soluble dyes or water-soluble dyes can be used, with yellow dyes, magenta dyes, cyan dyes, etc. being preferred.

[0117] Yellow dyes include, for example, aryl or heteryl azo dyes having phenols, naphthols, anilines, pyrazolones, pyridones, or 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 oxonol dyes; and quinone dyes such as naphthoquinone dyes and anthraquinone dyes. Other dyes include quinophthalone dyes, nitro / nitroso dyes, acridine dyes, and acridinone dyes. These dyes may exhibit yellow only upon partial dissociation of the chromophore. In this case, the countercation may be an inorganic cation such as an alkali metal or ammonium, or an organic cation such as pyridinium or a quaternary ammonium salt, or may even be a polymer cation having these as a partial structure.

[0118] Examples of magenta dyes include aryl or heteryl azo dyes having phenols, naphthols, or anilines as coupling components; azomethine dyes having pyrazolones or pyrazolotriazoles as coupling components; methine dyes such as arylidene dyes, styryl dyes, merocyanine dyes, and oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and xanthene dyes; quinone dyes such as naphthoquinones, anthraquinones, and anthrapyridones; and condensed polycyclic dyes such as dioxazine dyes. These dyes may exhibit magenta only upon partial dissociation of the chromophore. In this case, the counter cation may be an inorganic cation such as an alkali metal or ammonium, or an organic cation such as a pyridinium or quaternary ammonium salt, or may even be a polymer cation having such a cation in its partial structure.

[0119] Cyan dyes include azomethine dyes such as indoaniline dyes and indophenol dyes; polymethine dyes such as cyanine dyes, oxonol dyes, and merocyanine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, and xanthene dyes; phthalocyanine dyes; anthraquinone dyes; aryl or heteryl azo dyes with phenols, naphthols, or anilines as coupling components; and indigo and thioindigo dyes. These dyes may exhibit cyan only upon partial dissociation of the chromophore. In this case, the countercation may be an inorganic cation such as an alkali metal or ammonium, or an organic cation such as a pyridinium or quaternary ammonium salt, or even a polymeric cation containing these cations. Black dyes such as polyazo dyes may also be used.

[0120] There are no particular limitations on the water-soluble dye, and direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, etc. can be preferably used.

[0121] Specific dye names that can be preferably used as the water-soluble dye are listed below.

[0122] CI Direct 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, CI Direct Violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101, CI Direct 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, CI Direct 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, 199, 200, 201, 202, 203, 207, 211, 213, 214, 218, 225, 229, 236, 237, 244, 248, 249, 251, 252, 264, 270, 280, 288, 289, 291, CI Direct 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, CI 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 CI Acid Violet 5, 34, 43, 47, 48, 90, 103, 126, CI 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, CI 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, CI Acid Black 7, 24, 29, 48, 52:1, 172, CI Reactive Red 3, 13, 17, 19, 21, 22, 23, 24, 29, 35, 37, 40, 41, 43, 45, 49, 55, CI Reactive Violet 1, 3, 4, 5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33, 34, CI Reactive Yellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41, 42, CI Reactive Blue 2, 3, 5, 8, 10, 13, 14, 15, 17, 18, 19, 21, 25, 26, 27, 28, 29, 38, CI Reactive Black 4, 5, 8, 14, 21, 23, 26, 31, 32, 34, CI Basic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29, 35, 36, 38, 39, 45, 46, CI Basic Violet 1, 2, 3, 7, 10, 15, 16, 20, 21, 25, 27, 28, 35, 37, 39, 40, 48, CI Basic Yellow 1, 2, 4, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39, 40, CI Basic Blue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69, 71, CI Basic Black 8, etc.

[0123] The particle size of the pigment or the like used as the colorant described above is preferably determined in consideration of the characteristics of the coating device for the near-infrared curable ink composition.

[0124] (3-2) Dispersant The near-infrared curable ink composition of this embodiment may further contain a dispersant. That is, the near-infrared absorbing particles described above may be dispersed together with a dispersant in a thermosetting resin, a thermoplastic resin, or a solvent, which is an optional component described below. The addition of a dispersant makes it possible to easily disperse the near-infrared absorbing particles in the near-infrared curable ink composition. Furthermore, when a coating film of the near-infrared curable ink composition is cured, variation in curing can be particularly suppressed.

[0125] The dispersant used in the near-infrared curable ink composition of this embodiment is not particularly limited, and any commercially available dispersant can be used, for example. However, the molecular structure of the dispersant preferably has a polyester-based, polyacrylic-based, polyurethane-based, polyamine-based, polycaprolactone-based, or polystyrene-based main chain, and functional groups such as an amino group, epoxy group, carboxyl group, hydroxyl group, or sulfo group. Dispersants with such molecular structures are less likely to deteriorate when a coating film of the near-infrared curable ink composition of this embodiment is intermittently irradiated with near-infrared rays for several tens of seconds. This is because, therefore, the occurrence of defects such as coloration due to such deterioration can be particularly suppressed.

[0126] Specific examples of commercially available dispersants that can be suitably used include SOLSPERSE3000, SOLSPERSE9000, SOLSPERSE11200, SOLSPERSE13000, SOLSPERSE13240, SOLSPERSE13650, SOLSPERSE13940, SOLSPERSE16000, SOLSPERSE17000, SOLSPERSE18000, SOLSPERSE20000, SOLSPERSE21000, SOLSPERSE24000SC, SOLSPERSE24000GR, SOLSPERSE26000, SOLSPERSE27000, SOLSPERSE28000, SOLSPERSE31845, SOLSPERSE32000, SOLSPERSE32500, SOLSPERSE32550, SOLSPERSE32600, SOLSPERSE33000, SOLSPERSE33500, SOLSPERSE34750, SOLSPERSE35100, SOLSPERSE35200, SOLSPERSE36600, SOLSPERSE37500, SOLSPERSE38500, SOLSPERSE39000, SOLSPERSE41000, SOLSPERSE41090, SOLSPERSE53095, SOLSPERSE55000, SOLSPERSE56000, SOLSPERSE76500, etc.; 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. manufactured by BIG CHEMICAL JAPAN CO., LTD.; BASF Japan Ltd. EFKA4008, EFKA4046, EFKA4047, EFKA4015, EFKA4020, EFKA4050, EFKA4055, EFKA4060, EFKA4080, EFKA4300, EFKA4330, EFKA4400, EFKA4401, EFKA4402, EFKA4403, EFKA4500, EFKA4510, EFKA453 0, EFKA4550, EFKA4560, EFKA4585, EFKA4800, EFKA5220, EFKA6230, JONCRYL67, JONCRYL678, JON CRYL586, JONCRYL611, JONCRYL680, JONCRYL682, JONCRYL690, JONCRYL819, JONCRYL-JDX5050, etc.; Examples include Ajisper PB-711, Ajisper PB-821, and Ajisper PB-822 manufactured by Ajinomoto Fine-Techno Co., Ltd.

[0127] As the dispersant, the dispersant already explained in the near-infrared particle dispersion liquid can also be used.

[0128] (3-3) Solvent The near-infrared curable ink composition of this embodiment may also contain a solvent together with the thermosetting resin or thermoplastic resin. That is, the near-infrared curable ink composition of this embodiment may also contain a solvent.

[0129] In this case, it is also preferable to use, as the solvent for the near-infrared curable ink composition, a reactive organic solvent having a functional group such as an epoxy group that reacts with a monomer or oligomer of the thermosetting resin contained in the uncured thermosetting resin during the curing reaction of the thermosetting resin.

[0130] The viscosity of the near-infrared curable ink composition can be adjusted by adding a solvent. This is because adjusting the viscosity of the near-infrared curable ink composition makes it possible to easily ensure the coatability of the near-infrared curable ink composition and the smoothness of the coated film.

[0131] The solvent is not particularly limited, and various organic solvents such as water, alcohols such as methanol, ethanol, propanol, butanol, isopropyl alcohol, 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.

[0132] As the solvent, the liquid medium described above in connection with the near-infrared absorbing particle dispersion liquid can also be used. [5] Method for producing near-infrared curable ink composition As described above, the near-infrared curable ink composition of this embodiment can be prepared by adding near-infrared absorbing particles to an uncured thermosetting resin or thermoplastic resin. Alternatively, the near-infrared curable ink composition of this embodiment may be prepared by dispersing near-infrared absorbing particles in an appropriate solvent and then adding an uncured thermosetting resin or thermoplastic resin. The near-infrared curable ink composition of this embodiment can also be prepared by adding an uncured thermosetting resin or thermoplastic resin to the near-infrared absorbing particle dispersion liquid described above.

[0133]

[0043] The near-infrared curable ink composition of this embodiment contains the near-infrared absorbing particles described above, and therefore, when applied to a substrate and irradiated with near-infrared rays to form a cured film, it is possible to achieve a more neutral color tone. Furthermore, since the near-infrared absorbing particles have excellent near-infrared absorption properties, they can supply sufficient heat when irradiated with near-infrared rays, and the resulting cured film can have sufficiently high adhesion to the substrate.

[0134] The near-infrared curable ink composition of this embodiment can also be used to form a three-dimensional object on a substrate. In other words, the near-infrared curable ink composition is also ideal for stereolithography, which forms three-dimensional objects.

[0135] As described above, by including a solvent in the near-infrared curable ink composition of this embodiment, the viscosity of the ink composition can be adjusted, and therefore the ink composition can be more easily handled when applied to a substrate or the like.

[0136] However, as described above, the near-infrared curable ink composition of this embodiment does not need to contain a solvent. By not including a solvent in the near-infrared curable ink composition of this embodiment, it is possible to omit the operation of volatilizing the solvent, etc., and therefore it is possible to improve the efficiency when curing an applied product of the near-infrared curable ink composition.

[0137] 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 in which a reduced pressure operation is applied can be used. [6] Near-infrared cured film and method for producing the near-infrared cured film The near-infrared ray cured film of this embodiment can be a cured product of the near-infrared ray curable ink composition described above.

[0138] The near-infrared-cured film of the present embodiment can be produced, for example, by the method for producing a near-infrared-cured product described below.

[0139] Specifically, the near-infrared curable ink composition described above is applied to the surface of a substrate or the like (application step), and then the solvent or the like is removed as necessary. The near-infrared curable ink composition is then irradiated with near-infrared rays to cure (curing step).

[0140] The coating and curing steps can be repeated to produce a near-infrared cured film of desired shape and size. It is also possible to form a three-dimensional object on a substrate, in which case the resulting product can be called a near-infrared cured product. [7] Method for manufacturing near-infrared cured products The method for producing a near-infrared-cured product of the present embodiment can include the following coating step and curing step.

[0141] In the coating step, the near-infrared curable ink composition described above can be coated onto a substrate to form a coating film.

[0142] In the curing step, the coating film is irradiated with near-infrared rays, thereby curing the near-infrared curable ink composition.

[0143] The near-infrared curable ink composition described above has excellent near-infrared absorption properties, and therefore, by applying the near-infrared curable ink composition to obtain a coating film, and then irradiating the coating film with near-infrared rays to cure it, a near-infrared cured film that exhibits excellent adhesion to a predetermined substrate can be obtained.

[0144] Furthermore, by adding at least one type of pigment or dye to the near-infrared curable ink composition, a colored film can be obtained. Since the color of the colored film is hardly affected by the near-infrared absorbing particles, the colored film can also be used as a color filter for a liquid crystal display or the like.

[0145] The near-infrared cured film of this embodiment has excellent adhesion, which is thought to be due to the fact that the near-infrared absorbing particles absorb the irradiated near-infrared rays and generate heat, and the thermal energy of the heat generation promotes reactions such as polymerization reactions, condensation reactions, and addition reactions of monomers, oligomers, etc. contained in the uncured thermosetting resin, thereby causing a curing reaction of the thermosetting resin. Another reason for the near-infrared cured film of this embodiment has excellent adhesion is thought to be that the heat generated by the near-infrared absorbing particles due to irradiation with near-infrared rays supplies sufficient heat, causing the thermoplastic resin to melt and harden by cooling.

[0146] The near-infrared curable ink composition described above may contain a solvent, but the solvent may be volatilized by heat generation from the near-infrared absorbing particles.

[0147] When the near-infrared absorbing curable ink composition described above contains a thermosetting resin as a resin component, even if a near-infrared absorbing cured film formed using the near-infrared absorbing curable ink composition is further irradiated with near-infrared rays, the cured film does not re-melt. This is because the near-infrared absorbing cured film contains a cured product of the thermosetting resin, and therefore does not re-melt even if the near-infrared absorbing particles generate heat upon irradiation with near-infrared rays.

[0148] This property, together with the excellent adhesion to the substrate described above, is particularly effective when the near-infrared curable ink composition of this embodiment is applied to a stereolithography method in which a three-dimensional object is formed by repeatedly applying the near-infrared curable ink composition and irradiating it with near-infrared rays, and repeatedly laminating a cured product of the near-infrared curable ink composition.

[0149] Each step will be described below. (1)Coating process In the coating step, the near-infrared curable ink composition described above can be coated onto a substrate to form a coating film.

[0150] In the coating step, the material of the substrate (base material) onto which the near-infrared curable ink composition is coated is not particularly limited.

[0151] The substrate may be one or more types of substrate selected from, for example, paper, resin, glass, and the like.

[0152] The resin is not particularly limited, but may be one or more selected from polyesters such as PET (polyethylene terephthalate), acrylic, urethane, polycarbonate, polyethylene, ethylene-vinyl acetate copolymer, vinyl chloride, fluororesin, polyimide, polyacetal, polypropylene, nylon, etc.

[0153] The shape of the substrate is not particularly limited, and can be made to match the shape required for the near-infrared cured product, for example, a plate shape.

[0154] The method for applying the near-infrared curable ink composition to the substrate surface 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. (2) Curing process In the curing step, the coating film is irradiated with near-infrared rays, thereby curing the near-infrared curable ink composition.

[0155] The near-infrared curable ink composition is preferably cured by infrared irradiation, more preferably by near-infrared irradiation, because near-infrared radiation has a high energy density and can efficiently impart the energy required to cure the resin in the near-infrared curable ink composition.

[0156] It is also preferable to cure the near-infrared curable ink composition by combining infrared irradiation with any method selected from known methods. For example, methods such as heating, blowing air, and irradiation with electromagnetic waves may be used in combination with infrared irradiation.

[0157] In this specification, infrared radiation refers to electromagnetic waves having a wavelength in the range of 0.1 μm to 1 mm, near-infrared radiation refers to infrared radiation having a wavelength of 0.75 μm to 4 μm, and far-infrared radiation refers to infrared radiation having a wavelength of 4 μm to 1000 μm. Generally, irradiation with either far-infrared radiation or near-infrared radiation can cure a near-infrared-curable ink composition and provide similar effects. However, irradiation with near-infrared radiation can cure a coating film more efficiently in a shorter time.

[0158] As described above, when curing the near-infrared-curable ink composition, electromagnetic waves can be irradiated together with near-infrared rays. Microwaves are preferably used as such electromagnetic waves. Microwaves refer to electromagnetic waves having a wavelength in the range of 1 mm to 1 m.

[0159] The microwaves to be irradiated preferably have a power of 200 W or more and 1000 W or less. A power of 200 W or more promotes the evaporation of the organic solvent remaining in the near-infrared curable ink composition, while a power of 1000 W or less ensures mild irradiation conditions and there is no risk of deterioration of the base material or resin components contained in the near-infrared curable ink composition, such as a thermosetting resin.

[0160] The infrared irradiation time for the near-infrared curable ink composition varies depending on the irradiation energy and wavelength, the composition of the near-infrared curable ink, and the amount of near-infrared curable ink applied, and is 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, it is possible to irradiate the near-infrared curable ink composition with infrared rays sufficient to cure it. By extending the irradiation time, it is possible, for example, to sufficiently dry the solvent in the near-infrared absorbing curable ink composition. However, with high-speed printing and application in mind, the irradiation time is preferably 30 seconds or shorter, and more preferably 10 seconds or shorter.

[0161] The infrared radiation source is not particularly limited, and infrared radiation may be obtained directly from a heat source, or effective infrared radiation may be obtained through a heat medium. For example, infrared radiation can be obtained by heating a discharge lamp of mercury, xenon, cesium, sodium, etc., a carbon dioxide laser, or an electric resistor of platinum, tungsten, nichrome, kanthal, etc. A preferred radiation source is a halogen lamp. Halogen lamps have advantages such as good thermal efficiency and quick start-up.

[0162] The infrared radiation to the coating film may be applied from the side of the substrate on which the near-infrared curable ink is applied, or from the backside. Simultaneous irradiation from both sides is also preferred, and it is also preferred to combine irradiation with elevated temperature drying or air drying. It is also more preferred to use a light collecting plate as needed. By combining these methods, it becomes possible to cure the near-infrared curable ink composition with infrared radiation for a short period of time.

[0163] According to the method for producing a near-infrared-cured product of this embodiment, the near-infrared-cured film described above can be produced. Furthermore, by repeatedly laminating the cured product of the near-infrared-curable ink composition, a three-dimensional object can also be formed. That is, by repeatedly performing the coating step and the irradiation step described above, a near-infrared-cured product having a desired three-dimensional structure can also be produced.

[0164] The near-infrared cured film and near-infrared cured product of this embodiment may contain a cured thermosetting resin or thermoplastic resin and the near-infrared absorbing particles described above. The near-infrared absorbing particles are preferably contained and dispersed in the thermosetting resin or thermoplastic resin. The near-infrared cured film and near-infrared cured product of this embodiment may further contain the pigments, dyes, dispersants, etc. described above. The components contained in the near-infrared cured film and near-infrared cured product of this embodiment may be partially or completely modified by irradiation with near-infrared rays, heat generation, etc. during the curing process.

[0165] According to the method for producing a near-infrared cured product of this embodiment, a stereolithography method can be carried out. That is, the method can be a stereolithography method having the coating step and the curing step described above. [Example]

[0166] The present invention will be specifically described below with reference to examples, although the present invention is not limited to the following examples. (Evaluation method) First, the evaluation methods used in the following examples and comparative examples will be described. (chemical analysis) The obtained near-infrared absorbing particles were chemically analyzed by atomic absorption spectrometry (AAS) for Cs and by inductively coupled plasma optical emission spectroscopy (ICP-OES) for W (tungsten). A LECO light element analyzer (ON-836) was used for O. (X-ray diffraction measurement) X-ray diffraction measurements were carried out by powder XRD measurement using Cu-Kα radiation with a Spectris X'Pert-PRO / MPD instrument.

[0167] (Optical properties of near-infrared cured film) Near-infrared cured film L * a * b * The color index was calculated in accordance with JIS Z 8701 (1999) by calculating the tristimulus values ​​X, Y, and Z for a D65 standard light source and a light source angle of 10°, and then calculated from the tristimulus values ​​in accordance with JIS Z 8729 (2004). [Example 1] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:6. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0168] The cesium tungsten oxide precursor powder was placed on an alumina boat and placed in a heating muffle furnace. While flowing a mixed gas of superheated steam and nitrogen gas (volume ratio: 50:50), the temperature was raised to 550°C and held for 1 hour. In Table 1, the mixed gas is represented as 50% N2-50% superheated H2O. Next, the gas supplied was changed to 100% nitrogen gas by volume. While flowing nitrogen gas, the temperature was held at 550°C for 0.5 hours, then the temperature was raised to 800°C and held for 1 hour. The temperature was then lowered to room temperature, yielding a slightly greenish-white powder (first heat treatment step).

[0169] The X-ray powder diffraction pattern of this white powder is Cs4W 11 O 35 (ICDD 00-51-1891).

[0170] Next, this white powder was placed in a carbon boat and placed in a tubular furnace. The temperature was increased in a 1% by volume H-Ar gas flow (represented as 1% H-Ar in Table 1) and the temperature was held at 550°C for 1 hour for reduction. Next, the gas supply was changed to 100% by volume Ar gas, and the temperature was held at 550°C for 30 minutes while Ar gas was flowing. The temperature was then increased to 800°C and heated for 1 hour, after which the temperature was lowered to room temperature to obtain a pale blue powder A (second heat treatment step).

[0171] The XRD powder pattern of the obtained powder A shows that the main phase is hexagonal Cs as shown in Figure 2. 0.32 WO3, the second phase is orthorhombic Cs4W 11 O 35 A broad two-phase mixture pattern was observed. Chemical analysis of Powder A revealed that the molar ratio of Cs / W was 0.33. The composition ratios of the other components are shown in Table 2. The XRD powder pattern in this case showed a hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction lines of both Cs4W were mixed. 11 O 35 The diffraction lines of were observed to have slight deviations from the ideal positions and intensities. No data matching this diffraction pattern was found in the ICDD database.

[0172] When this powder was observed under a transmission electron microscope (Hitachi High-Tech Corporation HF-2200), fine particles 40 were observed, as shown in Figure 4(A). The crystals of each fine particle were observed as a single-phase structure, rather than a mixed structure consisting of two separate phases, hexagonal and orthorhombic, as shown in the selected-area electron diffraction pattern in Figure 4(B). The electron diffraction pattern shown in Figure 4(B) corresponds to the hexagonal

[0001] crystal zone, and the diffraction spots indicate the plane indices when considered as hexagonal. When the corresponding interplanar spacings were calculated from the nearest diffraction spots in the three directions, only the (01-10) interplanar spacing was 3.88 Å, significantly larger than the values ​​for the other two directions, 3.48 Å and 3.43 Å, indicating deviation from precise hexagonal symmetry. Note that, although in crystallography, negative indices are usually indicated by a bar above the number, for convenience of description, a minus sign is used in front of the number in this specification.

[0173] On the other hand, Figure 4(C) shows an atomic image taken using the STEM-HAADF method (high-angle-angle-diffusion dark-field observation in scanning electron mode). The higher the atomic number and the greater the atomic density in the projection direction, the brighter and more intense the atomic spot obtained. When combined with the projection plane information of the

[0001] crystal zone, the atomic species in the image can be identified. The most intense spot in Figure 4(C) is a W atom, but it is aligned along the (01-10) plane. A similar arrangement is not observed along the equivalent (1-100) or (10-10) planes in a hexagonal crystal. The streaks observed in the (01-10) spot direction in Figure 4(C) indicate that many planar defects (W and O vacancies) have been inserted only in the (01-10) plane, which is interpreted as increasing the interplanar spacing of the (01-10) plane. In a hexagonal crystal, almost no defects are introduced into the (01-10), (1-100), and (10-10) planes, which intersect at 60°. However, many planar defects have been inserted only into the (01-10) plane, causing it to lose its hexagonal symmetry and become orthorhombic. The regular spots indicated by arrow 41 in Figure 4(B) show that the W vacancy planes have been introduced with a periodicity of approximately 3.88 Å. As described above, it was determined that these near-infrared absorbing particles are single-crystal particles of cesium tungstate with a pseudo-hexagonal crystal structure that has been modulated into an orthorhombic crystal.

[0174] Furthermore, the obtained near-infrared-absorbing particle powder was irradiated with 25 W Al-Kα X-rays using an X-ray photoelectron spectrometer (ULVAC-PHI XPS-Versa Probe II). Observation of excited photoelectrons revealed that the O1s peak near 530.45 eV had a shoulder on the high-energy side. The component near 532.80 eV was assumed to be due to H2O, and peak separation revealed that it contained a large amount of OH2. Furthermore, thermal desorption spectroscopy confirmed that OH and OH2 were expelled from the crystals during heating in the temperature range between 500°C and 700°C. These observations suggest that OH and OH2 are contained in the cesium tungstate of Powder A. Considering the voids in the uniaxially elongated pseudohexagonal crystals, they are presumed to have infiltrated the window voids of the hexagonal tunnel. It is believed that water and its decomposition products were introduced into the crystals during crystallization in superheated steam, and the H generated during this process was also a major source of hydrogen. + and H3O + It is thought that the ions competed with the positive W ions, leading to partial desorption of the W ions. (Near-infrared curable ink composition, production and evaluation of cured film)

[0175] 20% by mass of the prepared powder A, 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 out. These weighed materials were placed in a glass container together with 0.3 mm diameter silica beads and dispersed and pulverized for 1 hour using a paint shaker to obtain dispersion A.

[0176] A near-infrared curable ink composition according to Example 1 (hereinafter referred to as ink A) was prepared by mixing 25 parts by mass of dispersion A and 75 parts by mass of a commercially available one-component thermosetting ink containing an uncured thermosetting resin (MEG Screen Ink (Medium) manufactured by Teikoku Ink Mfg. Co., Ltd.).

[0177] Ink A was applied to a 3 mm thick blue plate glass using a bar coater (No. 10) to form a coating film (coating step).

[0178] Next, the coated film was irradiated with near-infrared rays to obtain a near-infrared cured film (hereinafter referred to as cured film A) (curing step).

[0179] In the curing process, a line heater HYP-14N (output 980 W) manufactured by Hibeck Co., Ltd. was used as the near-infrared radiation source. The heater was placed at a height of 5 cm from the coating surface of the coating film, and near-infrared radiation was irradiated for 10 seconds.

[0180] The resulting cured film A had a thickness of 20 μm and was visually confirmed to be transparent.

[0181] The average particle size of the cesium tungsten oxide particles dispersed in the cured film A was calculated to be 24 nm using an image processing device based on a transmission electron microscope image. The particle size of each particle is the diameter of the circumscribed circle of the particle, and the average particle size is calculated as the median diameter in the particle size distribution of particle sizes measured for 100 particles.

[0182] The adhesion of the cured film A was evaluated by the following method.

[0183] One hundred square-shaped cuts were made in the cured film A using a cutter guide with a gap spacing of 1 mm. Then, 18 mm wide tape (Cellotape (registered trademark) CT-18 manufactured by Nichiban Co., Ltd.) was attached to the cut surface above the squares, and a 2.0 kg roller was rolled back and forth 20 times to completely adhere the tape. After that, the tape was rapidly peeled off at a peeling angle of 180 degrees, and the number of peeled squares was counted. The number of peeled squares was zero.

[0184] 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-curable ink described above, the cured film did not re-melt.

[0185] The spectral characteristics of the prepared cured film A were measured using a spectrophotometer manufactured by Hitachi Ltd., based on the reflectance of light with wavelengths of 200 nm to 2100 nm, and the color index was calculated. * =88, a * =-1, b* =8, which confirmed that the blue color was very weak and the color tone was neutral.

[0186] The results are shown in Table 3. Table 3 also shows the results obtained in Examples 2 to 14, Comparative Examples 1 and 2, which will be described later. [Example 2] (Production and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder prepared in Example 1 was placed on an alumina boat and placed in a heating muffle furnace. The temperature was raised to 150°C while flowing 100% by volume of nitrogen gas. The gas supplied here was changed to a gas containing superheated steam, hydrogen gas, and nitrogen gas in a volume ratio of 50:1:49 (represented in Table 1 as 1% H2-49% N2-50% superheated H2O). The temperature was raised to 550°C while flowing this mixed gas and maintained at that temperature for 1 hour. The temperature was then lowered to room temperature, yielding light blue powder B (first heat treatment step).

[0187] The X-ray powder diffraction pattern of this powder has broad diffraction lines, as shown in Figure 2, and is consistent with hexagonal Cs 0.32 The main phase is WO3, but the orthorhombic Cs4W 11 O 35 and pyrochlore phase (CsO) 0.44 The diffraction lines of the W2O6 phase showed a pattern mixed with a different phase. The diffraction lines of this pyrochlore phase were broad and the reflection positions were slightly shifted. It is thought that O, OH, OH2, and OH3 derived from water were incorporated into the pyrochlore cavities. The (111) plane of the cubic pyrochlore phase is a plane with hexagonal symmetry similar to the basal plane of a hexagonal crystal, and the pyrochlore cavities correspond to the voids between the hexagonal and trigonal cavities in a hexagonal crystal. In other examples, small amounts of reflections from the pyrochlore phase were often observed mixed in the XRD powder patterns.

[0188] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction image was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0189] Chemical analysis of Powder B showed that Cs / W=0.32. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder B. The evaluation results are shown in Table 3. [Example 3] (Production and evaluation of near-infrared absorbing particles) The light blue powder B obtained in Example 2 was spread on a carbon boat and held at 550°C for 2 hours in a 1% by volume H-Ar gas flow. Next, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 550°C for 0.5 hours while flowing nitrogen gas, then heated and held at 800°C for 1 hour. The boat was cooled to room temperature, and light blue powder C was obtained (second heat treatment step).

[0190] Chemical analysis of Powder C revealed that the Cs / W ratio was 0.31. The composition ratios of other components are shown in Table 2.

[0191] As shown in Figure 2, the X-ray powder diffraction pattern of Powder C has broader diffraction lines than those of Examples 1 and 2, and is a hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed with Cs4W. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0192] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder C. The evaluation results are shown in Table 3. [Example 4] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat, heated in a 100% by volume Ar gas flow, and held at 800° C. for 1 hour. The temperature was then lowered to room temperature, and a pale blue powder D was obtained.

[0193] The X-ray powder diffraction pattern of Powder D has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0194] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0195] Chemical analysis of Powder D showed that Cs / W=0.33. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder D. The evaluation results are shown in Table 3. [Example 5] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas supplied was changed to 1% by volume H-Ar, and the temperature was maintained at 800°C for 10 minutes in the gas flow. The temperature was then lowered to room temperature, and a pale blue powder E was obtained.

[0196] The X-ray powder diffraction pattern of Powder E has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0197] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0198] Chemical analysis of Powder E showed that Cs / W=0.32. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder E. The evaluation results are shown in Table 3. [Example 6] (Production and evaluation of near-infrared absorbing particles) The pale blue powder B obtained in Example 2 was spread on a carbon boat and held at 500°C for 30 minutes in a 1% by volume H-Ar gas flow. Next, the gas supplied was changed to 100% by volume nitrogen gas, and the boat was held at 550°C for 30 minutes while flowing nitrogen gas. After that, the temperature was further increased to 800°C and held for 1 hour. The temperature was then lowered to room temperature, and pale blue powder F was obtained.

[0199] The X-ray powder diffraction pattern of Powder F has broad diffraction lines as shown in Figure 2, and is consistent with hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0200] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism plane spot that appeared in the electron diffraction pattern was short and accompanied by a weak streak, indicating that the hexagonal crystal was an orthorhombic crystal modulated by prismatic defects.

[0201] Chemical analysis of Powder F showed that Cs / W=0.31. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder F. The evaluation results are shown in Table 3. [Example 7] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:10. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0202] The first heat treatment step was carried out under the same conditions as in Example 2, except that the cesium tungsten oxide precursor powder was used.

[0203] The powder obtained in the first heat treatment step was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas being supplied was changed to a 1% by volume H-Ar gas flow, and the temperature was maintained at 800°C for 10 minutes while the gas was being supplied. Then, the temperature was lowered to room temperature, and light blue powder G was obtained.

[0204] The X-ray powder diffraction pattern of powder G has broad diffraction lines, indicating that it is hexagonal Cs 0.20 WO3 (ICDD0-083-1333) and orthorhombic Cs4W 11 O 35 The diffraction patterns were mixed. 11 O 35The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0205] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the position of the prism spot appearing in the electron diffraction pattern was short and accompanied by a weak streak, and the powder was identified as an orthorhombic crystal with the hexagonal crystals modulated by prismatic defects.

[0206] Chemical analysis of Powder G showed that Cs / W=0.20. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder G. The evaluation results are shown in Table 3. [Example 8] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 3:10. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0207] The first heat treatment step was carried out under the same conditions as in Example 2, except that the cesium tungsten oxide precursor powder was used.

[0208] The powder obtained in the first heat treatment step was spread on a carbon boat and heated to 800°C in a 100% by volume Ar gas flow. Then, the gas supplied was changed to 1% by volume H-Ar, and the temperature was maintained at 800°C for 10 minutes while the gas was flowing, and then the temperature was lowered to room temperature to obtain light blue powder H.

[0209] The X-ray powder diffraction pattern of Powder I has broad diffraction lines, indicating that it is a rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48is the main phase, and hexagonal Cs 0.32 WO3 and tetragonal Cs2W3O 10 The diffraction patterns showed a slight mixture of Cs6W. 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0210] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0211] Chemical analysis of Powder H showed that Cs / W=0.59. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except that Powder H was used. The evaluation results are shown in Table 3. [Example 9] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 2:11. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0212] Then, the first heat treatment step was carried out under the same conditions as in Example 2, except that the above cesium tungsten oxide precursor powder was used, and a pale green powder I was obtained.

[0213] The X-ray powder diffraction pattern of Powder I has broad diffraction lines as shown in Figure 3, indicating the pyrochlore phase (CsO). 0.44 The main phase is W2O6, and the hexagonal Cs 0.32 WO3 and orthorhombic Cs4W11 O 35 The diffraction patterns showed a slight mixture of the (Cs2O) 0.44 W2O6 and Cs4W 11 O 35 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0214] Transmission electron microscopy of this powder revealed a cubic electron diffraction pattern.

[0215] Chemical analysis of Powder I showed that Cs / W=0.36. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder I. The evaluation results are shown in Table 3. [Example 10] (Production and evaluation of near-infrared absorbing particles) Powder I prepared in Example 9 was spread on a carbon boat and heated to 800°C while flowing 100% by volume of Ar gas. Then, the gas being supplied was changed to 1% by volume of H-Ar, and the boat was kept at 800°C for 10 minutes while flowing this gas, and then cooled to room temperature to obtain light blue Powder J.

[0216] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0217] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0218] Chemical analysis of Powder J showed that Cs / W=0.36. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder J. The evaluation results are shown in Table 3. [Example 11] (Production and evaluation of near-infrared absorbing particles) The powder I prepared in Example 9 was spread on a carbon boat and held in a 1% by volume H-Ar gas flow at 500°C for 30 minutes. Then, the gas being supplied was changed to 100% by volume nitrogen gas, and the boat was held at 800°C for 1 hour while the nitrogen gas was flowing, and then cooled to room temperature to obtain a light blue powder K.

[0219] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0220] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0221] Chemical analysis of the powdered K showed that Cs / W=0.35. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder K. The evaluation results are shown in Table 3. [Example 12] (Production and evaluation of near-infrared absorbing particles) A total of 20 g of cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded to a molar ratio of Cs2CO3:WO3 = 1:5. The resulting mixture was placed in a carbon boat and dried in air at 110°C for 12 hours. This yielded a cesium tungsten oxide precursor powder, a compound raw material containing Cs and W.

[0222] The precursor powder was then placed on an alumina boat in a heating muffle furnace and heated to 150°C while flowing 100% by volume of nitrogen gas. The gas supplied here was changed to a gas containing superheated steam, hydrogen gas, and nitrogen gas in a volume ratio of 50:1:49, and the temperature was raised to 550°C while flowing this mixed gas and maintained at that temperature for 1 hour. The temperature was then lowered to room temperature, yielding a light blue powder L (first heat treatment step).

[0223] The X-ray powder diffraction pattern of Powder L has broad diffraction lines as shown in Figure 3, indicating the pyrochlore phase (CsO). 0.44 The main phase is W2O6, and the hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 The diffraction patterns showed a slight mixture of the (Cs2O) 0.44 W2O6 and Cs4W 11 O 35The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0224] Transmission electron microscopy of this powder revealed a cubic electron diffraction pattern.

[0225] Chemical analysis of Powder L showed that Cs / W=0.40. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder L. The evaluation results are shown in Table 3. [Example 13] (Production and evaluation of near-infrared absorbing particles) The powder L prepared in Example 12 was spread on a carbon boat and heated to 800°C while flowing 100% by volume of Ar gas. Then, the gas being supplied was changed to 1% by volume of H-Ar, and the boat was kept at 800°C for 10 minutes while flowing this gas, and then cooled to room temperature to obtain a light blue powder M.

[0226] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0227] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0228] Chemical analysis of Powder M showed that Cs / W=0.42. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder M. The evaluation results are shown in Table 3. [Example 14] (Production and evaluation of near-infrared absorbing particles) The powder L prepared in Example 12 was spread on a carbon boat and held in a 1% by volume H-Ar gas flow at 500°C for 30 minutes. Then, the gas being supplied was changed to 100% by volume Ar, and the boat was held at 550°C for 30 minutes while the gas was being flowed. The temperature was then further increased to 800°C and held for 1 hour, and the temperature was then lowered to room temperature to obtain light blue powder N.

[0229] The X-ray powder diffraction pattern of this powder is shown in Figure 3, which indicates that it is a hexagonal Cs 0.32 WO3, orthorhombic Cs4W 11 O 35 , rhombohedral Cs6W 11 O 36 and Cs 8.5 W 15 O 48 However, the diffraction patterns of Cs4W 11 O 35 , Cs6W 11 O 36 , Cs 8.5 W 15 O 48 The diffraction line positions and intensities of the SiO2 did not completely agree with the ICDD data.

[0230] When one particle of this powder was observed under a transmission electron microscope from the (0001) direction, the positions of the prism plane spots appearing in the electron diffraction pattern were found to differ by more than the experimental error range, indicating that the powder was mainly composed of rhombohedral crystals in which hexagonal crystals were modulated by basal defects.

[0231] Chemical analysis of the powder N showed that Cs / W=0.42. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) A near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1, except for using Powder N. The evaluation results are shown in Table 3. [Comparative Example 1] (Production and evaluation of near-infrared absorbing particles)

[0232] The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat, heated to 850°C in a tubular furnace in the atmosphere, and held for 20 hours. The temperature was then lowered to room temperature, and the powder was crushed and mixed in a grinder. The powder was then heated again to 850°C in the atmosphere, held for 20 hours, and then lowered to room temperature, yielding a very slightly greenish white powder i. The X-ray powder diffraction pattern of this powder i, as shown in Figure 2, showed a slight CsW 11 O 36 There are some mixed in, but it's mostly Cs4W 11 O 35 It was identified as a single phase (ICDD 0-51-1891). Chemical analysis of powder i showed a Cs / W ratio of 0.36. The composition ratios of other components are shown in Table 2. (Near-infrared curable ink composition, production and evaluation of cured film) Except for using Powder i, a near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3. Comparative Example 2

[0233] (Production and evaluation of near-infrared absorbing particles) The cesium tungsten oxide precursor powder obtained in Example 1 was placed in a carbon boat and held at 550°C for 2 hours under a 1% by volume H gas flow with N gas as a carrier. The flow was then changed to 100% by volume N gas and held for 1 hour. The temperature was then increased to 800°C and held for 1 hour, and the powder was slowly cooled to room temperature to obtain powder II. Powder II was dark blue in color. The X-ray powder diffraction pattern of this powder II, as shown in Figure 2, showed Cs 0.32 It was identified as a single phase WO3 (ICDD 0-81-1244), a hexagonal cesium tungsten oxide. Chemical analysis of powder II showed a Cs / W ratio of 0.34. The composition ratios of other components are shown in Table 2.

[0234] (Near-infrared curable ink composition, production and evaluation of cured film) Except for using Powder ii, a near-infrared curable ink composition and a cured film were obtained and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 3.

[0235] [Table 1]

[0236] [Table 2]

[0237] [Table 3] The XRD powder patterns of the powders prepared in Examples 1 to 7 all showed hexagonal Cs 0.32 WO3 and orthorhombic Cs4W 11 O 35 However, the intensity ratio and position of the diffraction lines were observed to deviate from the ICDD data, which is thought to be due to the influence of irregular planar defects inserted on the prism surface. The (0001) electron diffraction pattern showed an increase in the interplanar spacing of one of the prism surface spots, confirming the modulation of the crystal structure to orthorhombic. In addition, the XRD powder patterns of the powders prepared in Examples 8 to 14 all showed hexagonal Cs 0.32 WO3 and rhombohedral Cs6W 11 O 36 , Cs 8.5 W 15 O 48 or pyrochlore phase (CsO) 0.44 Although the presence of W2O6 was observed, the diffraction line positions and intensity distributions of the rhombohedral and pyrochlore phases deviated from the ICDD data. The (0001) electron diffraction patterns showed changes in the interplanar spacing of all three prism surface spots, confirming the modulation of the crystal structure to rhombohedral. Furthermore, the powders identified as having a pyrochlore phase pattern by XRD also showed cubic electron diffraction patterns. This confirms that the cesium tungstates contained in the powders prepared in Examples 1 to 14 have a pseudohexagonal crystal structure.

[0238] The cured films prepared using the near-infrared curable ink compositions prepared in Examples 1 to 14, which contained near-infrared absorbing particles containing cesium tungstate that satisfied the predetermined composition, all had a color tone of b * Ga b * ≧0, and the blue color was very weak and neutral. In other words, it was confirmed that the cured films of these examples contained near-infrared absorbing particles containing composite tungsten oxide and could be made to have a more neutral color tone.

[0239] In contrast, the near-infrared absorbing particles contained in the cured films of Comparative Examples 1 and 2 do not contain cesium tungsten oxide that satisfies the predetermined composition.

[0240] The cured film produced using the near-infrared curable ink composition in Comparative Example 1 exhibited a neutral color tone, but the number of peeled squares was as high as 25, confirming poor adhesion. This is thought to be due to the low solar radiation absorptance of the near-infrared absorbing particles contained in the near-infrared curable ink composition used in Comparative Example 1.

[0241] In addition, the cured film using the near-infrared curable ink composition prepared in Comparative Example 2 had a color tone of b * Ga b * <0, and it can be seen that a bluish tinge is clearly recognized. In other words, it was confirmed that the cured film of Comparative Example 2 could not be made to have a neutral color tone. [Explanation of symbols]

[0242] 10 Ternary Composition Diagram 11, 16 areas 12~15 straight line 40 Fine particles 41 Arrow 50, 61 Near-infrared absorbing particles 50A surface 51 Covering 60 Near-infrared curable ink composition 62 Resin component

Claims

1. a thermosetting or thermoplastic resin; near-infrared absorbing particles, the near-infrared absorbing particles contain cesium tungstate, The cesium tungstate has a pseudo-hexagonal crystal structure that is modulated into one or more crystal structures selected from orthorhombic, rhombohedral, and cubic crystal structures; The cesium tungstate has the general formula Cs ｘ W ｙ O ｚ In the ternary composition diagram with Cs, W, and O at the vertices, x = 0.6y, z = 2.5y, y = 5x, and Cs ２ O:W.O. ３ = m:n (m and n are integers).

2. The cesium tungstate is O, OH, OH ２ , O.H. ３ The near-infrared curable ink composition according to claim 1 , further comprising one or more additive components selected from the following:

3. The additive component is WO of the cesium tungstate crystal. ６ The near-infrared curable ink composition according to claim 2 , wherein the octahedron is present in one or more positions selected from a hexagonal window, a hexagonal cavity, and a trigonal cavity.

4. The cesium tungstate crystal has a partial deficiency in one or more elements selected from Cs and W, The general formula Cs ｘ W ｙ O ｚ The near-infrared curable ink composition according to claim 1 , wherein x and y satisfy the relationship 0.2≦x / y≦0.

6.

5. WO constituting the cesium tungstate crystal ６ The near-infrared curable ink composition according to claim 1 , wherein a part of the O in the octahedron is missing.

6. 6. The near-infrared curable ink composition according to claim 1, wherein a portion of Cs in the cesium tungstate is substituted with an additional element, and the additional element is one or more elements selected from the group consisting of Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

7. 7. The near-infrared curable ink composition according to claim 1, wherein the near-infrared absorbing particles have an average particle size of 0.1 nm or more and 200 nm or less.

8. 8. The near-infrared curable ink composition according to claim 1, wherein the near-infrared absorbing particles have surfaces coated with a compound containing one or more types of atoms selected from the group consisting of Si, Ti, Zr, Al, and Zn.

9. The near-infrared curable ink composition according to claim 1 , further comprising at least one pigment selected from the group consisting of an organic pigment, an inorganic pigment, and a dye.

10. The near-infrared curable ink composition according to claim 1 , further comprising a dispersant.

11. The near-infrared curable ink composition according to claim 1 , further comprising a solvent.

12. A near-infrared cured film that is a cured product of the near-infrared curable ink composition according to claim 1 .

13. a coating step of applying the near-infrared curable ink composition according to any one of claims 1 to 11 onto a substrate 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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