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 comprises near-infrared absorbing particles containing composite tungsten oxide and can have a more neutral color tone when cured.SOLUTION: The near-infrared curable ink composition comprises a thermosetting resin or thermoplastic resin and near-infrared absorbing particles, where the near-infrared absorbing particles contain cesium tungsten oxide having an orthorhombic or hexagonal crystal structure and represented by general formula CsxW1-yO3-z (0.2≤x≤0.4, 0<y≤0.4, 0<z≤0.46).SELECTED DRAWING: Figure 1

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. It relates thereto.

Background Art

[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 printing can be performed without heating.

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

[0004] Furthermore, in order to improve the light resistance of the obtained printed surface or coated surface, generally, an ultraviolet absorber is added to the printed surface or coated surface. However, when an ultraviolet absorber is added to an ultraviolet curable ink or paint, there is a problem 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 light rather than ultraviolet light.

[0006] In addition, the applicant of the present application discloses a near-infrared curable ink composition containing a composite tungstate in Patent Documents 9 and 10.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

[0008] [Non-Patent Document 1] K. Adachi and T. Asahi, "Activation of plasmons and polarons in solar control cesium tungsten bronze and reduced tungsten oxide nanoparticles," Journal of Material Research, Vol. 27, 965-970 (2012) [Non-Patent Document 2] S. Yoshio and K. Adachi, "Polarons in reduced cesium tungsten bronzes studied using the DFT+U method," Materials Research Express, Vol. 6, 026548 (2019) [Non-Patent Document 3] K. Machida, M. Okada, and K. Adachi, "Excitations of free and localized electrons at nearby energies in reduced cesium tungsten bronze nanocrystals," Journal of Applied Physics, Vol. 125, 103103 (2019)

Non-Patent Document 4

Non-Patent Document 5

Non-Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0009] However, according to the study by the inventors of the present invention, the near-infrared curable compositions described in Patent Documents 7 and 8 mentioned above all had problems such as insufficient near-infrared absorption characteristics.

[0010] On the other hand, the composite tungsten oxide fine particles contained in the near-infrared curable ink compositions disclosed in Patent Documents 9 and 10 are materials that have a high transmittance of visible light and a low absorption rate, but have a low transmittance of light in the near-infrared region and a high absorption rate. Therefore, the near-infrared curable ink composition containing such composite tungsten oxide fine particles also has excellent near-infrared absorption characteristics.

[0011] However, since the composite tungsten oxide fine particles preferentially absorb light with a long wavelength in visible light, that is, red light, they are accompanied by blue coloring, and the degree of blue becomes stronger as the addition amount of the fine particles increases. For this reason, the cured film etc. obtained by containing the composite tungsten oxide fine particles as a near-infrared absorption component are accompanied by blue coloring, and it was difficult to color them with yellow-based or light colors other than blue, which are complementary colors of blue, by adding other pigments.

[0012] Therefore, an object of one aspect of the present invention is to provide a near-infrared curable ink composition containing near-infrared absorbing particles containing a composite tungsten oxide, which can have a neutral color tone when cured.

Means for Solving the Problems

[0013] In one aspect of the present invention, a thermosetting resin or a thermoplastic resin and, near-infrared absorbing particles, and the near-infrared absorbing particles have the general formula Cs x W 1-y O 3-zContaining cesium tungstate represented by (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46) and having an orthorhombic or hexagonal crystal structure and the cesium tungsten oxide has linear or planar defects on one or more surfaces selected from the orthorhombic (010) plane, the {100} plane which is the prism plane of the hexagonal crystal, and the (001) plane which is the bottom plane of the hexagonal crystal Provided is a near-infrared curable ink composition.

Advantages of the Invention

[0014] In one aspect of the present invention, it is possible to provide a near-infrared curable ink composition containing near-infrared absorbing particles containing a composite tungstate and capable of achieving a neutral color tone when cured.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

[0001] HEX crystal zone axis of the pseudo-hexagonal crystal particles of powder A obtained in Experimental Example 1-1.

Figure 6

[0221] crystal zone axis of the pseudo-hexagonal crystal particles of powder A obtained in Experimental Example 1-1.

Figure 7

[0001] HEX crystal zone axis of the pseudo-hexagonal crystal particles of powder B obtained in Experimental Example 1-2.

Figure 8

[0001] HEX crystal zone axis of the pseudo-hexagonal crystal particles of powder C obtained in Experimental Example 1-3.

Modes for Carrying Out 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] Regarding the near-infrared curable ink composition of this embodiment, [1] near-infrared absorbing particles and a method for producing the near-infrared absorbing particles, [2] a near-infrared absorbing particle dispersion, [3] a near-infrared curable ink composition, and [4] a method for producing the near-infrared curable ink composition will be described in this order. [1] Near-infrared absorbing particles and a method for producing the near-infrared absorbing particles (Near-infrared absorbing particles) Conventionally, the transmitted color of cesium-added hexagonal tungsten bronze particles used as near-infrared absorbing particles is defined by the imaginary part of its dielectric function (ε2) (the ε2 obtained in the experiment is published in Non-Patent Document 1) and the band structure (Non-Patent Document 2).

[0017] In the energy region of visible light (1.6 eV to 3.3 eV), the band gap of cesium-added hexagonal tungsten bronze (hereinafter abbreviated as Cs-HTB) is sufficiently large. In addition, since electron transitions between the d-d orbits of tungsten are prohibited by Fermi's golden rule, the probability of electron transition becomes small, and ε2 takes a small value. Since ε2 represents the absorption of photons by electrons, visible light transparency occurs if ε2 is small at visible wavelengths. However, in the vicinity of the blue wavelength, which has the shortest wavelength in the visible light region, absorption due to interband transitions exists, and in the vicinity of the red wavelength, which has the longest wavelength, localized surface plasmon resonance (LSPR) absorption and polaronic electron transition absorption exist (Non-Patent Document 3). Therefore, each is subject to restrictions on light transparency.

[0018] As described above, in Cs-HTB, the band gap is large enough that the inter-band transition has an energy equal to or higher than that of blue-wavelength light, resulting in high blue transparency. Conversely, on the red-wavelength side, Cs-HTB has a large number of conduction electrons, so LSPR absorption and polaritonic absorption become stronger, and at the same time, the absorption wavelength approaches the red-wavelength side, resulting in low transparency. Therefore, the transmitted color of a Cs-HTB particle dispersion film or the like appears blue.

[0019] That is, in order to neutralize the blue transmitted color of Cs-HTB, it is sufficient to enhance the absorption on the blue side and the transmission on the red side. For this purpose, it is preferable to shift the absorption position of the inter-band transition to lower energy and also weaken the LSPR absorption and polaritonic absorption and shift them to the lower energy side.

[0020] In order to weaken the LSPR absorption and polaritonic absorption, it is effective to reduce the amount of free electrons and bound electrons contained in the material.

[0021] The increase in the absorption on the blue side described above is realized by using a material with a different energy band structure having a lower energy band gap as a base. Also, the transmission on the red side can be controlled by adjusting the amounts of cesium ions (Cs + ) and oxygen vacancies (V O ), which are the sources of free electrons and bound electrons.

[0022] Based on the above considerations, the inventors of the present invention have conducted various studies on cesium tungstate, which is an oxide containing cesium (Cs) and tungsten (W). As a result, when near-infrared absorbing particles containing cesium tungstate obtained by reducing the crystal powder of a cesium tungstate precursor nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0) containing Cs and W are used, it has been found that the color tone of a near-infrared absorbing particle dispersion such as a dispersed transmission film or a near-infrared absorbing particle dispersion liquid also has a reduced blue tint and is neutralized. Further, it has been found that a near-infrared curable ink composition containing such near-infrared absorbing particles and a cured product thereof can also have a more neutral color tone.

[0023] Starting from a compound with a band gap narrower than that of hexagonal Cs-HTB and lower blue transmissivity, the near-infrared absorbing particles are reduced to gradually increase V O and gradually increase LSPR absorption and polarronic absorption within an acceptable range to optimize the red transmittance, thereby neutralizing the color tone.

[0024] In the cesium tungstate precursor nCs2O·mWO3 containing Cs, the charges of the positive elements Cs and W are neutralized by O, and it is a non-conductor. Cs2W7O 22 、Cs6W 20 O 63 、Cs2W6O 19 、Cs4W 11 O 35 、Cs6W 11 O 36 、Cs2W3O 10 In compounds aligned on the WO3-Cs2O line such as etc., since the valences are balanced, the Fermi energy E F exists between the valence band and the conduction band, and it is a non-conductor. When the Cs / W ratio (molar ratio) is 0.2 or more, in order to incorporate Cs with a large ionic radius, the basic skeleton formed by W-O octahedra has a hexagonal symmetric structure with large hexagonal voids, or a crystal structure with a plane defect containing W deficiency (tungsten deficiency) in the atomic arrangement of a hexagonal crystal or a cubic crystal (pyrochlore structure) with large hexagonal voids, and the symmetry has dropped to orthorhombic or monoclinic.

[0025] For example, in the case of 2Cs2O·11WO3, in the model of Solodovnikov 1998 (Non-Patent Document 4), within the hexagonal arrangement of W-O octahedra similar to hexagonal tungsten bronzes, a plane with W and O deficiencies at a pitch of b / 8 of the orthorhombic unit cell is inserted into the hexagonal (110) plane (= orthorhombic (010) plane), and as a whole, it is orthorhombic. In these cesium tungsten oxide precursors nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0), the band gap is narrower than that of Cs-HTB, and thus the blue permeability is low. However, when this is heated and reduced, the whole gradually changes to the hexagonal structure of tungsten bronzes. During this process, the band structure changes, the band gap widens, and the absorption of blue weakens, so it was found that the transmission of blue becomes stronger. In addition, at this time, as the reduction progresses, electrons are gradually injected into the conduction band and it becomes a conductor, and the band gap gradually widens due to the Burstein-Moss effect, so the transmission of blue becomes even stronger.

[0026] When the orthorhombic crystal becomes hexagonal by heat reduction, the plane defects containing W deficiencies in the orthorhombic crystal gradually disappear, and a hexagonal framework of W-O octahedra is formed. The plane defects containing W deficiencies exist on the (010) ORTH plane, and this plane is the hexagonal prism plane {100} HEX , that is, [(100) HEX , (010) HEX , (110) HEX , so as the heat reduction progresses, it gradually becomes a hexagonal crystal with defects on the {100} HEX plane. The hexagonal crystal at this time deviates from the perfect hexagonal symmetry because the {100} HEX plane contains defects, and it can be said to be in a pseudo-hexagonal state. In this way, as the heat reduction progresses, the crystal structure changes from orthorhombic to pseudo-hexagonal and further to hexagonal. At this time, the plane defects of the (010) ORTH plane containing W deficiencies in the orthorhombic crystal are inherited by the plane defects of the {100} HEX plane and gradually decrease, and are finally considered to disappear.

[0027] As the crystal structure changes during heating and reduction, the electronic structure also changes. The disappearance of W defects brings about a large amount of electron injection into the material. In the orthorhombic crystal, the outer shell electrons of Cs are consumed for the neutralization of O, resulting in overall charge neutrality. However, when the W defects decrease and the crystal becomes pseudo-hexagonal, six outer shell electrons per W atom are consumed for the neutralization of O, causing the outer shell electrons of Cs to enter the lower conduction band W-5d orbitals and become free electrons. These free electrons cause near-infrared absorption due to LSPR absorption. On the other hand, heating and reduction simultaneously have the effect of generating V O . The generation of V O proceeds at random sites. When V O occurs, the two adjacent W atoms become charge-excessive, and localized electrons bound to W 5+ are generated (Non-Patent Document 2). These localized electrons transition to the vacancies in the upper conduction band, causing polaronic absorption, and a part of them is excited to the free electron orbitals, causing LSPR absorption (Non-Patent Document 3). Since the absorption by these free electrons and bound electrons both has a peak wavelength in the near-infrared range, the tail of the absorption extends to the red wavelength, thus reducing the red transmissivity. The greater the amount of free electrons and bound electrons, that is, the greater the degree of reduction, the more the LSPR absorption and polaronic absorption wavelengths shift to higher wavelengths, and the absorption amount also increases, so the red transmissivity decreases.

[0028] Therefore, by reducing the crystal powder of the cesium tungstate precursor nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0) and adjusting the degree of reduction during that process, the blue transmission color can be neutralized.

[0029] The near-infrared absorbing particles of the present embodiment described above can be produced by heating the crystal powder of the cesium tungstate precursor nCs2O·mWO3 containing Cs and W in a reducing atmosphere at 650 °C or higher and 950 °C or lower. In the formula of the above cesium tungstate, n and m are integers, and it is preferable to satisfy 3.6 ≦ m / n ≦ 9.0.

[0030] That is, as the near-infrared absorbing particles, crystal powder of cesium tungsten oxide precursor nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0) containing cesium and tungsten can be used, which is obtained by heating and reducing in an atmosphere of a reducing gas at 650°C or higher and 950°C or lower.

[0031] In order for all or part of them to become hexagonal tungsten bronze by heating and reduction, the value of m / n needs to be in the range of 3.6 ≦ m / n ≦ 9.0 as described above. If it is less than 3.6, it will become a cubic pyrochlore phase after heating and reduction, with strong coloring and no near-infrared absorption. If it is greater than 9.0, it will phase-separate into hexagonal tungsten bronze and tungsten trioxide after heating and reduction, and the near-infrared absorption effect will be significantly reduced. The above cesium tungsten oxide precursor is more preferably Cs4W 11 O 35 That is, as the near-infrared absorbing particles, it is more preferable to use particles obtained by heating and reducing a cesium tungsten oxide precursor containing a Cs4W 11 O 35 phase in an atmosphere of a reducing gas at 650°C or higher and 950°C or lower. By using near-infrared absorbing particles obtained by high-temperature reduction of Cs4W 11 O 35 a large near-infrared absorption effect can be obtained while having a transmitted color with suppressed blueness when the near-infrared absorbing particles are dispersed. Here, the main phase means the phase most contained in terms of mass ratio.

[0032] As described above, the heating temperature during the reduction of cesium tungsten oxide is preferably 650°C or higher and 950°C or lower. By setting it at 650°C or higher, the structural change from orthorhombic to hexagonal can proceed sufficiently, and the near-infrared absorption effect can be enhanced. Also, by setting it at 950°C or lower, the speed of the crystal structure change can be appropriately maintained, and it can be easily controlled to an appropriate crystal state and electronic state. If the heating temperature is higher than 950°C and the reduction goes too far, lower oxides such as W metal and WO2 may be generated, which is not preferable from this perspective.

[0033] And the near-infrared absorbing particles of the present embodiment are represented by the general formula Cs x W 1-y O 3-z (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46), and can contain cesium tungstate having an orthorhombic or hexagonal crystal structure. Note that the near-infrared absorbing particles can also contain cesium tungstate having an orthorhombic crystal structure and cesium tungstate having a hexagonal crystal structure at the same time.

[0034] By satisfying the above general formula for the cesium tungstate contained in the near-infrared absorbing particles, the degree of W deficiency and oxygen vacancies V o are in an appropriate range. When dispersed to form a near-infrared curable ink composition or the like, while suppressing the solar transmittance, the transmitted color of the cured product can also be made a more neutral color tone.

[0035] Note that the near-infrared absorbing particles can also be composed of the above composite tungstate. However, even in this case, it does not exclude containing inevitable impurities mixed in during the manufacturing process or the like.

[0036] Conventionally known tungsten bronzes for near-infrared absorption have a hexagonal crystal structure. On the other hand, the composite tungstate of the near-infrared absorbing particles of the present embodiment can have an orthorhombic or hexagonal crystal structure. Here, the hexagonal crystal includes pseudo-hexagonal crystals.

[0037] Cesium tungstate, which is a composite tungstate containing near-infrared absorbing particles, preferably has linear or planar defects on one or more surfaces selected from the orthorhombic (010) plane, the {100} plane which is the prism plane of the hexagonal crystal, and the (001) plane which is the bottom plane of the hexagonal crystal. The above-mentioned defects include stacking irregularities based on the misalignment between planes, and the disorder of the arrangement and atomic positions of Cs atoms and W atoms within the plane. Therefore, the electron diffraction spots often have streaks. The {100} plane which is the prism plane of the above-mentioned hexagonal crystal means the (100) plane, the (010) plane, and the (110) plane. Such defects of the composite tungstate, that is, lattice defects, are accompanied by at least W deficiency, specifically, partial deficiency of W. This W deficiency causes the deficiency of electrons in the crystal, and as described above, this is one of the essential causes and acts on the neutralization of the blue tone.

[0038] Cesium tungstate has defects, and such defects can include tungsten deficiency as described above.

[0039] In addition, a part of O in the W - O octahedron, that is, the WO6 octahedron, which constitutes the orthorhombic or hexagonal crystal that is the basic structure of cesium tungstate, can also have further deficiencies. Such defects can be random defects. The vacancy V of this octahedral oxygen O can be introduced randomly as described above. In the known hexagonal tungsten bronze Cs 0.32 WO 3―y it is known that y = 0.46 or up to 15% of the total O lattice points (Non-Patent Document 5). The general formula Cs x W 1―y O 3―z of the cesium tungstate containing near-infrared absorbing particles in this embodiment can contain V O in an amount of up to z = 0.46. That is, z can be 0.46 or less.

[0040] The lattice constant of cesium tungsten oxide corresponds to the amount of defects, composition, and crystallinity in the crystal lattice. Variations in the value of the a-axis are observed with respect to these variables, while the value of the c-axis corresponds relatively well to the amount of lattice defects or optical properties. As a result, it is preferable that the cesium tungsten oxide contained in the near-infrared absorbing particles of the present embodiment has a c-axis length in terms of hexagonal crystal of 7.560 Å or more and 7.750 Å or less. By setting the c-axis length in terms of hexagonal crystal of cesium tungsten oxide within the above range, the near-infrared absorption effect can be sufficiently enhanced, and the visible light transmittance can be particularly enhanced. When the cesium tungsten oxide is hexagonal, conversion is not necessary, and the c-axis length in the hexagonal crystal becomes the c-axis length in terms of the above hexagonal crystal conversion.

[0041] When the diffraction pattern of the sample of the cesium tungsten oxide contained in the near-infrared absorbing particles of the present embodiment is measured by the X-ray powder diffraction method, it is often identified as a mixed phase of orthorhombic and hexagonal crystals. For example, when reducing the raw material of Cs4W 11 O 35 , it is identified as a mixed phase of orthorhombic Cs4W 11 O 35 and hexagonal Cs 0.32 WO3. In this case, the lattice constants of each phase can be obtained by Rietveld analysis or the like and converted into values in terms of hexagonal crystal. As already explained, orthorhombic crystal is a hexagonal crystal with lattice defect planes, so the lattice constant of orthorhombic crystal can be converted into the lattice constant of hexagonal crystal by an appropriate lattice correspondence model. Assuming the correspondence of the lattice change between orthorhombic and hexagonal crystals to be the model of Solodovnikov 1998 (Non-Patent Document 4), from the geometric relationship with respect to this model, 4a orth 2 + b orth 2 = 64a hex 2 = 64b hex 2 , c orth = c hex relationships are extracted, so all lattice constants in terms of hexagonal crystal can be obtained using these equations. Note that a orth , b orth , c orthmeans the lengths of the a-axis, b-axis, and c-axis of the orthorhombic crystal. Also, a hex , b hex , c hex means the lengths of the a-axis, b-axis, and c-axis of the hexagonal crystal.

[0042] In the cesium tungstate contained in the near-infrared absorbing particles of this embodiment, part of Cs may be substituted with an additive element. In this case, it is preferable that the additive element is one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga.

[0043] The above-mentioned additive element has electron-donating properties and assists the electron donation to the conduction band of the W-O octahedral skeleton at the Cs site.

[0044] 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 when the average particle size of the near-infrared absorbing particles is 200 nm or less, the localized surface plasmon resonance is more significantly expressed, so the near-infrared absorption characteristics can be particularly enhanced, that is, the solar transmittance can be particularly suppressed. Also, when the average particle size of the near-infrared absorbing particles is 0.1 nm or more, it can be easily manufactured industrially. Also, the particle size is closely related to the color of the near-infrared absorbing particle dispersion, etc., which is a dispersion transmission film in which the near-infrared absorbing particles are dispersed. In the particle size range where Mie scattering is dominant, the shorter the wavelength in the visible light region, the less the scattering as the particle size decreases. Therefore, increasing the particle size has the effect of particularly suppressing the blue color tone, but when it exceeds 100 nm, the haze of the film due to light scattering becomes a size that cannot be ignored, and when it exceeds 200 nm, in addition to the increase in the haze of the film, the generation of surface plasmons is suppressed and the LSPR absorption may become excessively small.

[0045] Here, the average particle size of the near-infrared absorbing particles can be known from the average value of the particle sizes of a plurality of near-infrared absorbing particles measured from the transmission electron microscope image, or from the dispersed particle size measured by a particle size measuring device based on the dynamic light scattering method of the dispersion liquid.

[0046] In addition, when applying particularly to applications that emphasize transparency in the visible light region, for example, when it is required to particularly suppress the influence on the color tone of a near-infrared curable ink composition or its cured product, etc., it is preferable to further consider reducing scattering by the near-infrared absorbing particles. When emphasizing such scattering reduction, the average particle size of the near-infrared absorbing particles is particularly preferably 30 nm or less.

[0047] Also, the near-infrared absorbing particles can be surface-treated for purposes such as surface protection, durability improvement, antioxidant property, and water resistance improvement. The specific content of the surface treatment is not particularly limited. For example, the near-infrared absorbing particles of this embodiment can have the surface of the near-infrared absorbing particles coated with a compound containing one or more kinds of atoms selected from Si, Ti, Zr, Al, and Zn. At this time, examples of the compound containing one or more kinds of atoms (elements) selected from Si, Ti, Zr, Al, and Zn include one or more selected from oxides, nitrides, carbides, etc.

[0048] Here, the band structures of cesium tungstate and the cesium tungstate precursor will be described.

[0049] As described above, it has been shown that when nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0) is reduced at a high temperature, a solar radiation shielding material with a transmission color closer to neutral can be obtained. During high-temperature reduction, hexagonal crystallization including the disappearance of W deficiency and the generation of V O inject electrons into the conduction band, which is considered to be the source of near-infrared absorption expression. Such changes in the electronic structure are verified by first-principles calculations.

[0050] Fig. 1(a) shows the crystal structure of Cs4W 11 O 35 . Also, Fig. 1(b) shows Cs 0.33 WO3, which is Cs4W 12 O 36shows the crystal structure. In FIGS. 1(a) and 1(b), cesium 11 and oxygen 12 are shown. Note that the same type of atoms are hatched the same. Since tungsten is arranged in the octahedron formed by oxygen 12, it is not shown in FIGS. 1(a) and 1(b). FIG. 1(b) is the structure of Cs 0.33 WO3 with the axes re-oriented in orthorhombic form for comparison with Cs4W 11 O 35 in FIG. 1(a).

[0051] The structure of Cs4W 11 O 35 in FIG. 1(a) is a structure in which W and O are regularly missing in the crystal structure of Cs4W 12 O 36 in FIG. 1(b).

[0052] The band structures of the cesium tungsten oxides with the crystal structures shown in FIGS. 1(a) and 1(b) are shown in FIGS. 2(a) and 2(b), respectively. Also, based on Cs4W 12 O 36 in FIG. 1(b), the band structure of Cs4W 11 O 36 with one W missing, and the band structures of Cs6W 17 O 54 with one W missing and the cell made 1.5 times in the b-axis direction are shown in FIGS. 2(c) and 2(d), respectively.

[0053] The band structures of Cs4W 11 O 35 shown in FIGS. 2(a) and 2(b), and the band structure of Cs4W 12 O 36 are similar, but the position of the Fermi energy (E F ) is within the band gap for the former and at the lower part of the conduction band for the latter. Therefore, Cs4W 11 O 35 is an insulator, and Cs4W 12 O 36 is a conductor. In Cs4W 11 O 35 , in Cs4W 12 O 36When viewed with reference to [it], there is a shortage of one each of W and O in the unit cell. When W and O are sufficient, Cs4W 12 O 36 forms a hexagonal WO3 network, and it is interpreted that Cs electrons are injected into its W-5d orbitals to become a conductor (Non-Patent Document 6).

[0054] Cs4W in Fig. 2(c) 11 O 36 is a structure in which one W is subtracted from Cs4W in Fig. 2(b) 12 O 36 .

[0055] Cs6W in Fig. 2(d) 17 O 54 , that is, 3Cs2O·17WO3, is a structure in which one W is subtracted while maintaining charge neutrality as seen from Cs4W in Fig. 2(b) 12 O 36 , that is, Cs6W 18 O 54 .

[0056] The amount of W deficiency decreases in the order of Fig. 2(a), Fig. 2(d), and Fig. 2(b), but E F rises successively to the bottom of the conduction band, which supports that W electrons are injected into the W-5d orbitals and the conduction electrons increase, resulting in an increase in near-infrared absorption Cs4W 12 O 36 When O is deficient from [it], detailed calculation examples have already been reported, and it has been found that localized orbitals are introduced at the bottom of the conduction band and both free electrons and localized electrons increase significantly (Non-Patent Document 2).

[0057] In the experimentally obtained pseudo-hexagonal crystal (an intermediate structure in the phase transition between orthorhombic and hexagonal crystals), an electronic state in which the above elements are mixed is considered. That is, with reduction, hexagonal crystallization including the disappearance of W deficiency and the generation of V O inject electrons into the conduction band little by little, and the Fermi energy E F rises from the band gap to the lower part of the conduction band.

[0058] Based on these band structures, the results of calculating the dielectric function including the Drude term are shown in Fig. 3. Focusing on the position of ε1 = 0 of the dielectric function ε1 shown in Fig. 3(b), the screened plasma frequency (Ω SP ) is found to increase in the order of Cs4W 11 O 35 , Cs6W 17 O 54 , Cs4W 12 O 36 , Cs4W 12 O 35 . It is expected that the near-infrared absorption will increase in this order, and this tendency is consistent with the observation results.

[0059] From the dielectric function ε2 plot shown in Fig. 3(a), it can be seen that ε2 in the visible region is generally small for cesium tungstate oxide. At 3.3 eV in the blue region indicated by the dotted line 31, the absorption of Cs4W 11 O 35 and Cs6W 17 O 54 with a narrow band gap is large due to interband transitions. On the other hand, at 1.6 eV in the red region indicated by the dotted line 32, the absorption of Cs4W 12 O 35 is large due to the influence of the tail of the surface plasmon absorption. The transmitted light in the red region is expected to decrease in the order of decreasing Ω SP . Compared with the conventionally used cesium tungstate oxide, the reason for the decrease in blue color in the cesium tungstate oxide contained in the near-infrared curable ink composition suitable for use in this embodiment is that Cs 0.33 W 1-y O 3―z phase containing W deficiency is formed by using nCs2O·mWO3 (3.6 ≦ m / n ≦ 9.0) with W and O deficiencies as a raw material, resulting in an increase in absorption on the high-energy side. By adjusting the high-temperature reduction of nCs2O·mWO3 (3.6 ≦ m / n ≦ 9.0), the band gap and the amount of electrons injected into the conduction band can be adjusted, and the bluish color tone can be adjusted. It was also confirmed that the near-infrared absorption effect at that time was maintained at a relatively high level. (Method for manufacturing near-infrared absorbing particles) The manufacturing method of the near-infrared absorbing particles of the present embodiment is not particularly limited, and any method can be used as long as it can manufacture near-infrared absorbing particles that satisfy the above-described characteristics. Here, a configuration example of the manufacturing method of the near-infrared absorbing particles will be described.

[0060] The manufacturing method of the near-infrared absorbing particles of the present embodiment can include, for example, the following steps.

[0061] A cesium tungstate oxide precursor synthesis step of synthesizing a cesium tungstate oxide precursor which is a tungstate containing cesium. A heat reduction step of heating and reducing the cesium tungstate oxide precursor at 650 ° C or higher and 950 ° C or lower in an atmosphere of a reducing gas.

[0062] Hereinafter, each step will be described. (1) Cesium tungstate oxide precursor synthesis step In the cesium tungstate oxide precursor synthesis step, a tungstate containing cesium, that is, a cesium tungstate oxide precursor which is a cesium tungstate can be synthesized. When the cesium tungstate oxide precursor has already been synthesized, the manufacturing method of the near-infrared absorbing particles of the present embodiment can also start from the heat reduction step.

[0063] The cesium tungstate oxide precursor which is a cesium tungstate is preferably a crystalline powder of nCs2O·mWO3 (n and m are integers, 3.6 ≦ m / n ≦ 9.0). As the cesium tungstate oxide precursor which is a cesium tungstate, a stable cesium tungstate is more preferable. As the stable cesium tungstate, Cs4W O 11 O 35 、Cs2W6O 19 、Cs6W 20 O 63 、Cs2W7O 22 、Cs6W 11 O 36One or more selected from the like. The cesium tungsten oxide precursor is particularly Cs4W as the main phase 11 O 35 It is more preferable that the cesium tungsten oxide precursor contains a phase.

[0064] These cesium tungstates can be prepared, for example, by firing a raw material powder mixture containing cesium and tungsten at 700 ° C or higher and 1000 ° C or lower in the atmosphere. The production method of cesium tungstate is not limited to the above form, and other methods such as the sol-gel method and the complex polymerization method can also be used.

[0065] In addition, as the cesium tungstate used as a starting material, an unbalanced tungstate obtained by vapor phase synthesis or the like may be used. Powders by the thermal plasma method, powders by electron beam melting, etc. are included in this. (2) Heating reduction process The cesium tungsten oxide precursor as the starting material described above, specifically, for example, cesium tungstate having one or more crystal structures selected from orthorhombic, monoclinic, and pseudo-hexagonal crystals can be subjected to the heating reduction process.

[0066] In the heating reduction process, the above-mentioned cesium tungsten oxide precursor can be heated and reduced at 650 ° C or higher and 950 ° C or lower in an atmosphere of a reducing gas. By carrying out the heating reduction process, near-infrared absorbing particles containing cesium tungsten oxide of a desired composition can be obtained.

[0067] When performing the heating reduction treatment, it is preferably performed under a gas flow 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. In addition, heating in a water vapor atmosphere, vacuum atmosphere, or other mild heating and reduction conditions may be used in combination.

[0068] Note that the method for manufacturing the near-infrared absorbing particles of the present embodiment is not particularly limited to the above form. As the method for manufacturing the near-infrared absorbing particles, various methods capable of forming a predetermined structure including a defective microstructure can be used. Examples of the method for manufacturing the near-infrared absorbing particles include a method of reducing tungstate obtained by a solid-phase method, a liquid-phase method, or a gas-phase method, and a method of reducing WO3 in molten alkali halide.

[0069] The method for manufacturing the near-infrared absorbing particles can further include an arbitrary step. (3) Grinding step As described above, it is preferable that the near-infrared absorbing particles are refined into particles. Therefore, in the method for manufacturing the near-infrared absorbing particles, a grinding step of grinding the powder obtained by the heat reduction step can be included.

[0070] The specific means for grinding and refining is not particularly limited, and various means capable of mechanically grinding can be used. As the mechanical grinding method, a dry grinding method using a jet mill or the like can be used. Further, in the process of obtaining the near-infrared absorbing particle dispersion liquid described later, it may be mechanically ground in a solvent. In this case, since the near-infrared absorbing particles are dispersed in the liquid medium in the grinding step, it can also be referred to as a grinding and dispersion step. (4) Coating step As described above, the surface of the near-infrared absorbing particles may be coated with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn. Therefore, the method for manufacturing the near-infrared absorbing particles can further include, for example, a coating step of coating the near-infrared absorbing particles with a compound containing one or more atoms selected from Si, Ti, Zr, Al, and Zn.

[0071] In the coating step, the specific conditions for coating the near-infrared absorbing particles are not particularly limited. For example, an alkoxide or the like containing one or more atoms selected from the above atomic group (metal group) can be added to the near-infrared absorbing particles to be modified to form a film on the surface of the near-infrared absorbing particles. [2] Near-infrared absorbing particle dispersion liquid Next, a configuration example of the near-infrared absorbing particle dispersion of the present embodiment will be described.

[0072] The near-infrared absorbing particle dispersion of the present embodiment can also be used, for example, when manufacturing a near-infrared curable ink composition described later.

[0073] The near-infrared absorbing particle dispersion of the present embodiment can contain the above-described near-infrared absorbing particles and one or more liquid media 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 the near-infrared absorbing particles are dispersed in the liquid medium.

[0074] As the liquid medium, as described above, one or more selected from water, organic solvents, oils and fats, liquid resins, and liquid plasticizers can be used.

[0075] As the organic solvent, various types such as alcohol-based, ketone-based, hydrocarbon-based, and glycol-based can be selected. Specifically, alcohol-based solvents such as isopropyl alcohol, methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, diacetone alcohol, and 1-methoxy-2-propanol; ketone-based solvents such as dimethyl ketone, acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester-based 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; formamide, N-methyl -ole monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, propylene glycol ethyl ether acetate, etc.; formamide, N-methyl One or more selected from amides such as N,N-dimethylformamide, dimethylacetamide, N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; halogenated hydrocarbons such as ethylene chloride and chlorobenzene, etc. can be mentioned.

[0076] However, among these, organic solvents with low polarity are preferred. 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. are more preferred. These organic solvents can be used alone or in combination of two or more.

[0077] Examples of the oil and fat 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 subjecting fatty acids of vegetable oils and monoalcohols to an ester reaction; ethers; petroleum solvents such as Isopar (registered trademark) E, Exxsol (registered trademark) Hexane, Heptane, E, D30, D40, D60, D80, D95, D110, D130 (the above are manufactured by ExxonMobil), etc.

[0078] As the liquid resin, one or more selected from, for example, liquid acrylic resin, liquid epoxy resin, liquid polyester resin, liquid urethane resin, etc. can be used.

[0079] As the liquid plasticizer, for example, a liquid plasticizer for plastics can be used.

[0080] The components contained in the near-infrared absorbing particle dispersion liquid are not limited to the above-mentioned near-infrared absorbing particles and liquid medium. The near-infrared absorbing particle dispersion liquid can also add and contain any components as necessary.

[0081] For example, an acid or an alkali may be added to the near-infrared absorbing particle dispersion as needed to adjust the pH of the dispersion.

[0082] In addition, in the above-described near-infrared absorbing particle dispersion, in order to further improve the dispersion stability of the near-infrared absorbing particles and avoid coarsening of the dispersion particle size due to re-aggregation, various surfactants, coupling agents, etc. can also be added as dispersants to the near-infrared absorbing particle dispersion.

[0083] The dispersants such as the surfactant and the coupling agent can be selected according to the application, but it is preferable that the dispersant has one or more selected from a group containing an amine, a hydroxyl group, a carboxyl group, and an epoxy group as functional groups. These functional groups adsorb on the surface of the near-infrared absorbing particles to prevent aggregation, and have an effect of uniformly dispersing the near-infrared absorbing particles even in an infrared shielding film formed using the near-infrared absorbing particles, for example. A polymer dispersant having one or more selected from the above functional groups (functional group groups) in the molecule is more desirable.

[0084] Commercially available dispersants that can be preferably used include Solsperse (registered trademark) 9000, 12000, 17000, 20000, 21000, 24000, 26000, 27000, 28000, 32000, 35100, 54000, 250 (manufactured by Nippon Lubrizol Corporation) 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), Ajsper® PA111, PB821, PB822, PN411, Feimex L-12 (manufactured by Ajinomoto Fine-Techno Co., Ltd.), DisperBYK® 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.), Disparon® 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, Ltd.), Alphon® UC-3000, UF-5022, UG-4010, UG-4035, UG-4070 (manufactured by Toagosei Co., Ltd.), etc. One or more selected from these can be mentioned.

[0085] The method for dispersing 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. At this time, it is preferable that the average particle size of the near-infrared absorbing particles can be dispersed so as to be 200 nm or less, and more preferably so as to be 0.1 nm or more and 200 nm or less.

[0086] As a method for dispersing near-infrared absorbing particles in a liquid medium, for example, there are dispersion treatment methods using devices such as bead mills, ball mills, sand mills, paint shakers, ultrasonic homogenizers, etc. Among them, from the perspective of shortening the time required to obtain the desired average particle size by pulverizing and dispersing with media stirring mills such as bead mills, ball mills, sand mills, paint shakers, etc. that use media (beads, balls, Ottawa sand), it is preferable. By the pulverization-dispersion treatment using a media stirring mill, at the same time as the dispersion of the near-infrared absorbing particles in the liquid medium, the formation of fine particles due to the collision of the near-infrared absorbing particles with each other or the collision of the media with the near-infrared absorbing particles also progresses, and the near-infrared absorbing particles can be made finer and dispersed. That is, it is pulverized-dispersed.

[0087] The average particle size of the near-infrared absorbing particles is preferably 0.1 nm or more and 200 nm or less as described above. This is because if the average particle size is small, the scattering of light in the visible light region with a wavelength of 400 nm or more and 780 nm or less due to geometric scattering or Mie scattering is reduced. As a result of the reduction of such light scattering, for example, the near-infrared absorbing particle dispersion in which the near-infrared absorbing particles are dispersed in a resin or the like obtained using the near-infrared absorbing particle dispersion liquid of the present embodiment does not become cloudy like frosted glass, and the loss of clear transparency can be avoided. That is, when the average particle size becomes 200 nm or less, the mode of the above geometric scattering or Mie scattering of light scattering becomes weak, and it becomes the Rayleigh scattering mode. In the Rayleigh scattering region, the scattered light is proportional to the sixth power of the dispersed particle size, so the scattering decreases and the transparency improves as the dispersed particle size decreases. And when the average particle size becomes 100 nm or less, the scattered light becomes very small, which is preferable.

[0088] By the way, as long as a known method of adding the dispersion liquid to the solid medium is performed, the dispersion state of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion in which the near-infrared absorbing particles are dispersed in a solid medium such as resin obtained using the near-infrared absorbing particle dispersion liquid of the present embodiment does not aggregate more than the average particle size of the near-infrared absorbing particles in the dispersion liquid.

[0089] In addition, if the average particle diameter of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less, it is possible to avoid the manufactured near-infrared absorbing particle dispersion and its molded body (such as a plate or a sheet) from becoming a grayish one with a monotonically decreasing transmittance.

[0090] The content of the near-infrared absorbing particles in the near-infrared absorbing particle dispersion liquid of the present 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 absorption rate can be exhibited by setting the content of the near-infrared absorbing particles to 0.01% by mass or more. Further, it is because the near-infrared absorbing particles can be uniformly dispersed in the dispersion medium by setting it to 80% by mass or less. [3] Near-infrared curable ink composition The near-infrared curable ink composition according to the present embodiment will be described.

[0091] The near-infrared curable ink composition of the present embodiment can contain a thermosetting resin or a thermoplastic resin and near-infrared absorbing particles. As the near-infrared absorbing particles, the above-described near-infrared absorbing particles can be used. Therefore, the near-infrared absorbing particles are, for example, represented by the general formula Cs x W 1-y O 3-z (0.2 ≤ x ≤ 0.4, 0 < y ≤ 0.4, 0 < z ≤ 0.46) and can contain cesium tungstate having an orthorhombic or hexagonal crystal structure. The thermosetting resin can be in an uncured state, specifically, for example, a state having fluidity.

[0092] Hereinafter, the components contained in the near-infrared curable ink composition of the present embodiment will be described. (1) Resin component The near-infrared curable ink composition of the present embodiment can contain a resin component, specifically, a thermosetting resin or a thermoplastic resin. (1-1) Regarding the thermosetting resin

[0093] The thermosetting resin is not particularly limited, and for example, one or more selected from epoxy resins, urethane resins, acrylic resins, urea resins, melamine resins, phenol resins, ester resins, polyimide resins, silicone resins, unsaturated polyester resins, etc. can be used.

[0094] These thermosetting resins are cured by being imparted with thermal energy from the near-infrared absorbing particles irradiated with near-infrared rays, and they are uncured resins. And the thermosetting resin may contain monomers and oligomers that form the thermosetting resin by a curing reaction, and known curing agents added as appropriate. Furthermore, a known curing accelerator may be added to the curing agent. (1-2) Regarding thermoplastic resins As the thermoplastic resin, for example, one or more selected from polyester resins, polycarbonate resins, acrylic resins, polystyrene resins, polyamide resins, vinyl chloride resins, olefin resins, fluorine resins, polyvinyl acetate resins, thermoplastic polyurethane resins, acrylonitrile-butadiene-styrene resins, polyvinyl acetal resins, acrylonitrile-styrene copolymer resins, ethylene-vinyl acetate copolymer resins, etc. can be used.

[0095] These thermoplastic resins are imparted with thermal energy from the near-infrared absorbing particles irradiated with near-infrared rays and once dissolved, and then can be cured into a desired shape by subsequent cooling. (2) Near-infrared absorbing particles As the near-infrared absorbing particles, the above-mentioned near-infrared absorbing particles can be used. Since the near-infrared absorbing particles have already been described, the description is omitted here.

[0096] 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 according to the properties required for the near-infrared curable ink composition, etc.

[0097] The amount of the near-infrared absorbing particles contained in the near-infrared curable ink composition of the present embodiment may be selected and added in such an amount that the uncured thermosetting resin can be cured during the curing reaction. Further, the amount of the near-infrared absorbing particles contained in the near-infrared curable ink composition of the present embodiment may be selected and added in such an amount that the thermoplastic resin can be dissolved during the heat dissolution reaction.

[0098] Therefore, considering the coating thickness when applying the near-infrared curable ink composition, the amount of the near-infrared absorbing particles per unit coating area of the near-infrared curable ink composition can be selected and determined.

[0099] 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 media mill or the like.

[0100] (3) Other components The near-infrared curable ink composition of the present embodiment can be composed only of the above resin component and the near-infrared absorbing particles, but can also contain an arbitrary component, for example, a pigment, a dye, a dispersant, a solvent, etc. described below according to the purpose. Even when the near-infrared curable ink composition is composed only of the resin component and the near-infrared absorbing particles as described above, it does not exclude containing inevitable components mixed in during the manufacturing process.

[0101] (3-1) Pigments and dyes As described above, the near-infrared curable ink composition of the present embodiment can further contain one or more selected from organic pigments, inorganic pigments, and dyes in order to color the ink composition. (3-1-1) Pigments The pigments are not particularly limited, and known pigments can be used without particular limitation. One or more selected from organic pigments such as insoluble pigments and lake pigments, and inorganic pigments such as carbon black can be preferably used.

[0102] These pigments are preferably present in a dispersed state in the near-infrared curable ink composition of the present embodiment. As a method for dispersing these pigments, known methods can be used without particular limitation.

[0103] The insoluble pigments are not particularly limited. For example, azo, azomethine, methine, diphenylmethane, triphenylmethane, quinacridone, anthraquinone, perylene, indigo, quinophthalone, isoindolinone, isoindoline, azine, oxazine, thiazine, dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole, etc. can be used.

[0104] The organic pigments are not particularly limited either, but specific pigment names that can be preferably used are listed below.

[0105] Examples of pigments for magenta or red include, for example, C.I. Pigment Red 2, C.I. Pigment Red 3, C.I. Pigment Red 5, C.I. Pigment Red 6, C.I. Pigment Red 7, C.I. Pigment Red 15, C.I. Pigment Red 16, C.I. Pigment Red 48:1, C.I. Pigment Red 53:1, C.I. Pigment Red 57:1, C.I. Pigment Red 122, C.I. Pigment Red 123, C.I. Pigment Red 139, C.I. Pigment Red 144, C.I. Pigment Red 149, C.I. Pigment Red 166, C.I. Pigment Red 177, C.I. Pigment Red 178, C.I. Pigment Red 202, C.I. Pigment Red 222, C.I. Pigment Violet 19, etc.

[0106] Examples of pigments for orange or yellow include, for example, C.I. Pigment Orange 31, C.I. Pigment Orange 43, C.I. Pigment Yellow 12, C.I. Pigment Yellow 13, C.I. Pigment Yellow 14, C.I. Pigment Yellow 15, C.I. Pigment Yellow 15:3, C.I. Pigment Yellow 17, C.I. Pigment Yellow 74, C.I. Pigment Yellow 93, C.I. Pigment Yellow 128, C.I. Pigment Yellow 94, C.I. Pigment Yellow 138, and the like.

[0107] Examples of pigments for green or cyan include, for example, C.I. Pigment Blue 15, C.I. Pigment Blue 15:2, C.I. Pigment Blue 15:3, C.I. Pigment Blue 16, C.I. Pigment Blue 60, C.I. Pigment Green 7, and the like.

[0108] Examples of pigments for black include, for example, C.I. Pigment Black 1, C.I. Pigment Black 6, C.I. Pigment Black 7, and the like.

[0109] Although there are no particular limitations on inorganic pigments, for example, carbon black, titanium dioxide, zinc sulfide, zinc oxide, zinc phosphate, mixed metal oxide phosphates, iron oxide, manganese iron oxide, chromium oxide, ultramarine, nickel or chromium antimony titanate oxide, cobalt oxide, aluminum, aluminum oxide, silicon oxide, silicate, zirconium oxide, mixed oxides of cobalt and aluminum, molybdenum sulfide, rutile mixed phase pigments, rare earth sulfides, bismuth vanadate, extender pigments composed of aluminum hydroxide and barium sulfate, etc. can be preferably used.

[0110] The average dispersed particle diameter of the pigment in the near-infrared curable ink composition according to the present invention is not particularly limited, but is preferably, for example, 1 nm or more and 100 nm or less. This is because when the average dispersed particle diameter of the pigment dispersion is 1 nm or more and 100 nm or less, the storage stability in the near-infrared curable ink composition is particularly good. The average dispersed particle diameter can be measured, for example, with an ELS-8000 manufactured by Otsuka Electronics Co., Ltd., which is a particle size measuring device based on the dynamic light scattering method.

[0111] (3-1-2) Dye The dye is not particularly limited either, and either an oil-soluble dye or a water-soluble dye can be used, and yellow dyes, magenta dyes, cyan dyes, etc. can be preferably used.

[0112] Examples of yellow dyes include aryl or heteroaryl azo dyes having phenols, naphthols, anilines, pyrazolones, pyridones, and open-chain active methylene compounds as coupling components; azomethine dyes having open-chain active methylene compounds as coupling components; methine dyes such as benzylidene dyes and monomethine oxonol dyes; quinone-based dyes such as naphthoquinone dyes and anthraquinone dyes. Other dye species include quinophthalone dyes, nitro·nitroso dyes, acridine dyes, acridinone dyes, etc. These dyes may be those that exhibit yellow only after a part of the chromophore dissociates. In that case, the counter cation may be an inorganic cation such as an alkali metal or ammonium, an organic cation such as pyridinium or a quaternary ammonium salt, or even a polymer cation having these as partial structures.

[0113] Examples of magenta dyes include aryl or heteroaryl 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, or oxonol dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, or xanthene dyes; quinone dyes such as naphthoquinone, anthraquinone, or anthrapyridone; and condensed polycyclic dyes such as dioxazine dyes. These dyes may exhibit magenta only when a part of the chromophore dissociates. In such cases, the counter cation may be an inorganic cation such as an alkali metal or ammonium, an organic cation such as pyridinium or a quaternary ammonium salt, or even a polymeric cation having these as partial structures.

[0114] Examples of cyan dyes include azomethine dyes such as indoaniline dyes or indophenol dyes; polymethine dyes such as cyanine dyes, oxonol dyes, or merocyanine dyes; carbonium dyes such as diphenylmethane dyes, triphenylmethane dyes, or xanthene dyes; phthalocyanine dyes; anthraquinone dyes; aryl or heteroaryl azo dyes having phenols, naphthols, or anilines as coupling components; and indigo and thioindigo dyes. These dyes may exhibit cyan only when a part of the chromophore dissociates. In such cases, the counter cation may be an inorganic cation such as an alkali metal or ammonium, an organic cation such as pyridinium or a quaternary ammonium salt, or even a polymeric cation having these as partial structures. Also, black dyes such as polyazo dyes can be used.

[0115] Water-soluble dyes are not particularly limited, and direct dyes, acid dyes, food dyes, basic dyes, reactive dyes, etc. can be preferably used.

[0116] Specific dye names that can preferably be used as water-soluble dyes are listed below.

[0117] C.I. 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, C.I. Direct Violet 7, 9, 47, 48, 51, 66, 90, 93, 94, 95, 98, 100, 101, C.I. 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, C.I. 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, C.I. 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, C.I. Acid Red 35, 42, 52, 57, 62, 80, 82, 111, 114, 118, 119, 127, 128, 131, 143, 151, 154, 158, 249, 254, 257, 261, 263, 266, 289, 299, 301, 305, 336, 337, 361, 396, 397, C.I. Acid Violet 5, 34, 43, 47, 48, 90, 103, 126, C.I. Acid Yellow 17, 19, 23, 25, 39, 40, 42, 44, 49, 50, 61, 64, 76, 79, 110, 127, 135, 143, 151, 159, 169, 174, 190, 195, 196, 197, 199, 218, 219, 222, 227, C.I. Acid Blue 9, 25, 40, 41, 62, 72, 76, 78, 80, 82, 92, 106, 112, 113, 120, 127:1, 129, 138, 143, 175, 181, 205, 207, 220, 221, 230, 232, 247, 258, 260, 264, 271, 277, 278, 279, 280, 288, 290, 326, C.I. Acid Black 7, 24, 29, 48, 52:1, 172, C.I. Reactive Red 3, 13, 17, 19, 21, 22, 23, 24, 29, 35, 37, 40, 41, 43, 45, 49, 55, C.I. Reactive Violet 1, 3, 4, 5, 6, 7, 8, 9, 16, 17, 22, 23, 24, 26, 27, 33, 34, C.I. Reactive Yellow 2, 3, 13, 14, 15, 17, 18, 23, 24, 25, 26, 27, 29, 35, 37, 41, 42, C.I. Reactive Blue 2, 3, 5, 8, 10, 13, 14, 15, 17, 18, 19, 21, 25, 26, 27, 28, 29, 38, C.I. Reactive Black 4, 5, 8, 14, 21, 23, 26, 31, 32, 34, C.I. Basic Red 12, 13, 14, 15, 18, 22, 23, 24, 25, 27, 29, 35, 36, 38, 39, 45, 46, C.I. Basic Violet 1, 2, 3, 7, 10, 15, 16, 20, 21, 25, 27, 28, 35, 37, 39, 40, 48, C.I. Basic Yellow 1, 2, 4, 11, 13, 14, 15, 19, 21, 23, 24, 25, 28, 29, 32, 36, 39, 40, C.I. Basic Blue 1, 3, 5, 7, 9, 22, 26, 41, 45, 46, 47, 54, 57, 60, 62, 65, 66, 69, 71, Examples include C.I. Basic Black 8, etc.

[0118] It is preferable to determine the particle size of the pigment or the like, which is a coloring material, as described above, in consideration of the characteristics of the coating apparatus for the near-infrared curable ink composition.

[0119] (3-2) Dispersant The near-infrared curable ink composition of this embodiment may further contain a dispersant. That is, the above-described near-infrared absorbing particles may be dispersed in a thermosetting resin, a thermoplastic resin, or a solvent, which is an arbitrary component described later, together with the dispersant. By adding the dispersant, the near-infrared absorbing particles can be easily dispersed in the near-infrared curable ink composition. In addition, when the coating film of the near-infrared curable ink composition is cured, the variation in curing can be particularly suppressed.

[0120] The dispersant used in the near-infrared curable ink composition of this embodiment is not particularly limited, and for example, commercially available dispersants can be arbitrarily used. However, as the molecular structure of the dispersant, those having a main chain of polyester-based, polyacrylic-based, polyurethane-based, polyamine-based, polycaprolactone-based, or polystyrene-based and having functional groups such as amino groups, epoxy groups, carboxyl groups, hydroxyl groups, and sulfo groups are preferable. Such a dispersant is less likely to be altered when the coating film of the near-infrared curable ink composition of this embodiment is intermittently irradiated with near-infrared rays for several tens of seconds. Therefore, it is possible to particularly suppress the occurrence of problems such as coloring caused by the alteration.

[0121] Specific examples of commercially available dispersants that can be suitably used include, for example, SOLSPERSE 3000, SOLSPERSE 9000, SOLSPERSE 11200, SOLSPERSE 13000, SOLSPERSE 13240, SOLSPERSE 13650, SOLSPERSE 13940, SOLSPERSE 16000, SOLSPERSE 17000, SOLSPERSE 18000, SOLSPERSE 20000, SOLSPERSE 21000, SOLSPERSE 24000SC, SOLSPERSE 24000GR, SOLSPERSE 26000, SOLSPERSE 27000, SOLSPERSE 28000, SOLSPERSE 31845, SOLSPERSE 32000, SOLSPERSE 32500, SOLSPERSE 32550, SOLSPERSE 32600, SOLSPERSE 33000, SOLSPERSE 33500, SOLSPERSE 34750, SOLSPERSE 35100, SOLSPERSE 35200, SOLSPERSE 36600, SOLSPERSE 37500, SOLSPERSE 38500, SOLSPERSE 39000, SOLSPERSE 41000, SOLSPERSE 41090, SOLSPERSE 53095, SOLSPERSE 55000, SOLSPERSE 56000, SOLSPERSE 76500, etc. manufactured by Lubrizol Japan Ltd.; Disperbyk-101, Disperbyk-103, Disperbyk-107, Disperbyk-108, Disperbyk-109, Disperbyk-110, Disperbyk-111, Disperbyk-112, Disperbyk-116, Disperbyk-130, Disperbyk-140, Disperbyk-142, Disperbyk-145, Disperbyk-154, Disperbyk-161, Disperbyk-162, Disperbyk-163, Disperbyk-164, Disperbyk-165, Disperbyk-166, Disperbyk-167, Disperbyk-168, Disperbyk-170, Disperbyk-171, Disperbyk-174, Disperbyk-180, Disperbyk-181, Disperbyk-182, Disperbyk-183, Disperbyk-184, Disperbyk-185, Disperbyk-190, Disperbyk-2000, Disperbyk-2001, Disperbyk-2020, Disperbyk-2025, Disperbyk-2050, Disperbyk-2070, Disperbyk-2095, Disperbyk-2150, Disperbyk-2155, Anti-Terra-U, Anti-Terra-203, Anti-Terra-204, BYK-P104, BYK-P104S, BYK-220S, BYK-6919, etc. manufactured by BIG CHEMICAL JAPAN CO., LTD.; EFKA4008, EFKA4046, EFKA4047, EFKA4015, EFKA4020, EFKA4050, EFKA4055, EFKA4060, EFKA4080, EFKA4300, EFKA4330, EFKA4400, EFKA4401, EFKA4402, EFKA4403, EFKA4500, EFKA4510, EFKA4530, EFKA4550, EFKA4560, EFKA4585, EFKA4800, EFKA5220, EFKA6230, JONCRYL67, JONCRYL678, JONCRYL586, JONCRYL611, JONCRYL680, JONCRYL682, JONCRYL690, JONCRYL819, JONCRYL-JDX5050, etc. manufactured by BASF Japan Ltd.; Examples include Ajisper PB-711, Ajisper PB-821, Ajisper PB-822, etc. of Ajinomoto Fine-Techno Co., Inc.

[0122] In addition, as the dispersant, the dispersant described in the above-mentioned near-infrared particle dispersion can also be used.

[0123] (3-3) Solvent The near-infrared curable ink composition of this embodiment can also use a solvent together with a thermosetting resin or a thermoplastic resin. That is, the near-infrared curable ink composition of this embodiment can further contain a solvent.

[0124] In this case, as the solvent of the near-infrared curable ink composition, for example, 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 thermosetting resin in an uncured state during the curing reaction of the thermosetting resin is preferably used.

[0125] By adding a solvent, the viscosity of the near-infrared curable ink composition can be adjusted. By adjusting the viscosity of the near-infrared curable ink composition, the coatability of the near-infrared curable ink composition and the smoothness of the coating film can be easily ensured.

[0126] The solvent is not particularly limited either. For example, alcohols such as water, 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 inbutyl ketone, and various organic solvents such as ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, polyethylene glycol, and polypropylene glycol can be used.

[0127] In addition, as the solvent, the liquid medium described in the above-mentioned near-infrared absorbing particle dispersion can also be used. (4) Near-infrared curable ink composition As described above, the near-infrared curable ink composition of the present embodiment can be prepared by adding near-infrared absorbing particles to an uncured thermosetting resin or thermoplastic resin. Further, the near-infrared curable ink composition of the present embodiment may be prepared by dispersing near-infrared absorbing particles in an appropriate solvent and then adding an uncured thermosetting resin or thermoplastic resin. Note that the near-infrared curable ink composition of the present embodiment can also be prepared by adding an uncured thermosetting resin or a thermoplastic resin to the above-mentioned near-infrared absorbing particle dispersion.

[0128] Since the near-infrared curable ink composition of the present embodiment contains the above-mentioned near-infrared absorbing particles, for example, when it is applied on a substrate and irradiated with near-infrared rays to form a cured film, a more neutral color tone can be obtained. In addition, since the above-mentioned near-infrared absorbing particles have excellent near-infrared absorption characteristics, sufficient heat can be supplied when irradiated with near-infrared rays or the like, and the adhesion of the obtained cured film to the substrate can be sufficiently enhanced.

[0129] In addition, according to the near-infrared curable ink composition of the present embodiment, a three-dimensional object can also be formed on a substrate. That is, it is also a near-infrared curable ink composition optimal for the stereolithography method for forming a three-dimensional object.

[0130] As described above, since the near-infrared curable ink composition of the present embodiment contains a solvent, its viscosity can be adjusted, so that the handleability when applying it to a substrate or the like can be improved.

[0131] However, as described above, the near-infrared curable ink composition of the present embodiment does not necessarily have to contain a solvent. Since the near-infrared curable ink composition of the present embodiment does not contain a solvent, an operation such as volatilizing the solvent can be omitted, so that the efficiency when curing the coating of the near-infrared curable ink composition can be improved.

[0132] In addition, when the near-infrared curable ink composition of the present embodiment contains a solvent, the method for removing the solvent after applying the near-infrared curable ink composition is not particularly limited, and for example, a heating distillation method with a reduced pressure operation or the like can be used. [Near-infrared cured film] The near-infrared cured film of the present embodiment can be a cured product of the above-described near-infrared curable ink composition.

[0133] 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.

[0134] Specifically, after applying the above-described near-infrared curable ink composition to the surface of a substrate or the like (coating step), if necessary, removing a solvent or the like and irradiating with near-infrared rays can cure the near-infrared curable ink composition (curing step).

[0135] The above coating step and curing step can be repeatedly performed to obtain a near-infrared cured film having a desired shape and size. Also, a three-dimensional object can be formed on the substrate, and in this case, it can also be called a near-infrared cured product.

[0136] [Method for producing near-infrared cured product] The method for producing a near-infrared cured product of the present embodiment can include the following coating step and curing step.

[0137] In the coating step, the aforementioned near-infrared curable ink composition can be coated on a substrate to form a coating film.

[0138] In the curing step, the coating film can be irradiated with near-infrared rays to cure the near-infrared curable ink composition.

[0139] Since the aforementioned near-infrared curable ink composition has visible light transmittance, by applying the near-infrared curable ink composition to obtain a coating film and irradiating the coating film with near-infrared rays for curing, a near-infrared cured film that exhibits excellent adhesion to a predetermined substrate can be obtained.

[0140] Also, a colored film can be obtained by adding at least one or more kinds of various pigments and dyes to the near-infrared curable ink composition. In the colored film, since there is almost no influence on the color tone by the near-infrared absorbing particles, the colored film can also be used for color filters such as liquid crystal displays.

[0141] In the near-infrared cured film of the present embodiment, as a factor for having the above excellent adhesion, the near-infrared absorbing particles absorb the irradiated near-infrared rays and generate heat, and the thermal energy of the generated heat promotes reactions such as polymerization reactions, condensation reactions, and addition reactions by monomers, oligomers, etc. contained in the uncured thermosetting resin, causing the curing reaction of the thermosetting resin. Also, in the near-infrared cured film of the present embodiment, as a factor for having the above excellent adhesion, it is also considered that sufficient heat is supplied by the heat generation of the near-infrared absorbing particles due to the irradiation of near-infrared rays, and curing occurs due to the dissolution and cooling of the thermoplastic resin.

[0142] Note that the aforementioned near-infrared curable ink composition can also contain a solvent, but the heat generation of the near-infrared absorbing particles can also cause the volatilization of the solvent and the like.

[0143] When the above-described near-infrared absorption curable ink composition contains a thermosetting resin as a resin component, the cured film formed using the near-infrared absorption curable ink composition will not remelt even when further irradiated with near-infrared rays. This is because such a near-infrared cured film contains a cured product of a thermosetting resin, so even if the near-infrared absorption particles generate heat due to irradiation with near-infrared rays, it will not remelt.

[0144] This property is particularly effective when applied to a stereolithography method for fabricating a three-dimensional object by repeatedly applying and irradiating with near-infrared rays the near-infrared absorption curable ink composition of the present embodiment and repeatedly laminating the cured product of the near-infrared absorption curable ink composition, in combination with the excellent adhesion to the above-described substrate.

[0145] Hereinafter, each step will be described. (1) Coating step In the coating step, the above-described near-infrared absorption curable ink composition can be applied onto a substrate to form a coating film.

[0146] In the coating step, the material of the substrate (base material) onto which the near-infrared absorption curable ink composition is applied is not particularly limited.

[0147] As the substrate, for example, one or more substrates selected from paper, resin, glass, etc. can be used.

[0148] The above resin is not particularly limited, but for example, 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. can be used.

[0149] The shape of the substrate is not particularly limited and can be made into a shape suitable for the shape required for the near-infrared cured product, for example, a plate shape.

[0150] The method of applying the near-infrared curable ink composition to the substrate surface is not particularly limited, and dipping method, flow coating method, spraying method, bar coating method, spin coating method, gravure coating method, roll coating method, screen printing method, blade coating method, etc. can be used.

[0151] (2) Curing step In the curing step, the coating film can be irradiated with near-infrared rays to cure the near-infrared curable ink composition.

[0152] As a method for curing the near-infrared curable ink composition, infrared irradiation is preferable, and near-infrared irradiation is more preferable. Near-infrared rays have a large energy density and can efficiently impart the energy necessary for the resin in the near-infrared curable ink composition to cure.

[0153] It is also preferable to combine infrared irradiation with any method selected from known methods to cure the near-infrared curable ink composition. For example, methods such as heating, blowing, and electromagnetic wave irradiation may be used in combination with infrared irradiation.

[0154] In this specification, infrared rays refer to electromagnetic waves having a wavelength in the range of 0.1 μm or more and 1 mm or less, near-infrared rays refer to infrared rays having a wavelength of 0.75 μm or more and 4 μm or less, and far-infrared rays refer to infrared rays having a wavelength of 4 μm or more and 1000 μm or less. Generally, regardless of whether either near-infrared rays or far-infrared rays, which are generally called, are irradiated, the near-infrared curable ink composition can be cured and the same effects can be obtained. However, when near-infrared rays are irradiated, the coating film can be cured more efficiently in a shorter time.

[0155] As described above, when curing the near-infrared curable ink composition, electromagnetic waves can also be irradiated together with near-infrared rays. As such electromagnetic waves, microwaves can be preferably used. Note that microwaves refer to electromagnetic waves having a wavelength in the range of 1 mm or more and 1 m or less.

[0156] The microwave to be irradiated preferably has a power of 200 W or more and 1000 W or less. If the power is 200 W or more, the vaporization of the organic solvent remaining in the near-infrared curable ink composition is promoted. If it is 1000 W or less, the irradiation conditions are mild, and there is no risk of deterioration of the resin components contained in the near-infrared curable ink composition such as the substrate and the thermosetting resin.

[0157] The infrared irradiation time for the near-infrared curable ink composition varies depending on the energy and wavelength to be irradiated, the composition of the near-infrared curable ink, and the coating amount of the near-infrared curable ink, and is not particularly limited. For example, generally, the above infrared irradiation time is preferably 0.1 second or more. By setting the irradiation time to 0.1 second or more, it becomes possible to perform sufficient infrared irradiation to cure the near-infrared curable ink composition. By increasing the irradiation time, for example, it is also possible to sufficiently dry the solvent in the infrared absorption curable ink composition. However, in view of high-speed printing and coating, the irradiation time is preferably within 30 seconds, and more preferably within 10 seconds.

[0158] The infrared radiation source is not particularly limited, and the infrared rays may be obtained directly from a heat source, or an effective infrared radiation may be obtained therefrom through a heat medium. For example, infrared rays can be obtained by heating discharge lamps such as mercury, xenon, cesium, and sodium, carbon dioxide lasers, and further heating of electrical resistors such as platinum, tungsten, nichrome, and kanthal. In addition, a halogen lamp is mentioned as a preferable radiation source. The halogen lamp has advantages such as good thermal efficiency and fast startup.

[0159] The irradiation of infrared rays on the coating film may be performed from the side of the near-infrared curable ink coating surface of the substrate or from the back side. It is also preferable to perform irradiation simultaneously from both sides, and it is also preferable to combine with heating and drying or air blowing and drying. Further, it is more preferable to use a condenser plate as necessary. By combining these methods, it becomes possible to cure the near-infrared curable ink composition by short-time infrared irradiation.

[0160] According to the method for producing a near-infrared cured product of the present embodiment, the above-described near-infrared cured film can be produced. Further, 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 above-described coating step and irradiation step, a near-infrared cured product having a desired three-dimensional structure can also be produced.

[0161] According to the method for producing a near-infrared cured product of the present embodiment, a stereolithography method can be carried out. That is, it can also be a stereolithography method having the coating step and the curing step described so far.

Examples

[0162] Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples.

[0163] First, the evaluation method of the near-infrared absorbing particles in the following experimental examples will be described. (Chemical analysis) The chemical analysis of the obtained near-infrared absorbing particles was performed by atomic absorption spectrometry (AAS) for Cs and by inductively coupled plasma optical emission spectrometry (ICP-OES) for W (tungsten). For O, a method of melting the sample in He gas using a light element analyzer (manufactured by LECO Corporation, model ON-836) and reacting with carbon in the crucible to quantify the CO gas by IR absorption spectrometry was used for analysis. In the following Experimental Examples 1-1 to 1-13, powders of near-infrared absorbing particles containing cesium tungsten composite oxides having W deficiency were obtained. Therefore, for powders A to M, which are the near-infrared absorbing particles obtained in Experimental Examples 1-1 to 1-13, the composition ratios obtained by multiplying the composition ratios when W is set to 1 by the values corresponding to the W deficiency determined by TEM observation, etc. all satisfy the general formula Cs x W 1-y O 3-z (0.2 ≦ x ≦ 0.4, 0 < y ≦ 0.4, 0 < z ≦ 0.46). (X-ray diffraction measurement) X-ray diffraction measurement was carried out by powder XRD measurement using a Cu-Kα ray with a Spectris X'Pert-PRO / MPD apparatus. The measurement was performed after calibrating the diffraction angle with a standard sample (NIST640e). Then, Rietveld analysis was performed on the obtained XRD diffraction pattern to determine the lattice constants of the crystal phases. In Table 1, the identified crystal phases are indicated in the pattern column of the XRD column. In the case of "orthorhombic + hexagonal", it means that both orthorhombic and hexagonal crystals are included. Also, in the case of "orthorhombic", it means that orthorhombic crystals are included, and in the case of "hexagonal", it means that hexagonal crystals are included.

[0164] In the case of a mixed phase of orthorhombic and hexagonal crystals, the lattice constants for each phase were determined. Then, the lattice constant of the orthorhombic crystal was converted to the lattice constant of the hexagonal crystal using the following lattice correspondence model. The correspondence of the lattice change between the orthorhombic and hexagonal crystals was extracted from the model of Solodovnikov 1998 (Non-Patent Document 4), Equation 4a

[0165] +b orth 2 +b orth 2 =64a hex 2 = 64b hex 2 、c orth =c hex Using, the lattice constant in terms of hexagonal crystal was determined. In the above equation, a orth 、b orth 、c orth mean the lengths of the a-axis, b-axis, and c-axis of the orthorhombic crystal. Also, a hex 、b hex 、c hex mean the lengths of the a-axis, b-axis, and c-axis of the hexagonal crystal. [Experimental Example 1] Near-infrared absorbing particles used in Experimental Example 2 described later were manufactured and evaluated. [Experimental Example 1-1] Cesium carbonate (Cs2CO3) and tungsten trioxide (WO3) were weighed, mixed, and kneaded in a molar ratio of Cs2CO3:WO3 = 2:11. The kneaded material thus obtained was placed in a carbon boat and heated twice at 850 °C for 20 hours each in a tubular furnace in the atmosphere to obtain a powder A´ which was a very pale greenish white powder. When heating, after heating at 850 °C for 20 hours, it was taken out once, pulverized and mixed, and then reheated under the same conditions.

[0166] The obtained white powder, powder A´, was evaluated as follows.

[0167] The X-ray powder diffraction pattern slightly contained Cs6W 11 O 36 but was almost identified as a Cs4W 11 O 35 single phase (ICDD 00-51-1891).

[0168] The lattice constants were measured to be a = 14.6733 Å, b = 52.3841 Å, and c = 7.7424 Å. These values were extremely close to the values of a = 14.6686 Å, b = 52.3971 Å, and c = 7.7356 Å by Solodovnikov (Non-Patent Document 4). The chemical analysis result of this white powder was Cs 0.36 WO 3.18 which was almost in agreement with the weighed composition.

[0169] Next, TEM observation of the obtained white powder, powder A´, was performed. When taking a restricted-field electron beam diffraction pattern, an orthorhombic spot pattern was obtained. Fig. 4 shows the spot pattern taken from the c-axis direction of the orthorhombic crystal. Periodicity of b / 8 cycle appeared in the b-axis direction, and the presence of the W and O defect planes was confirmed. Also, from the streak running in the b-axis direction, it was found that there were some plane defects on the b plane. This spot pattern of the c-axis zone axis is close to six-fold symmetry, but the angle between the (480) and (4-80) spots is 52.2°, deviating from 60° in the case of six-fold symmetry, which is considered to be due to the W and O defect planes incorporated in the b / 8 cycle and deviating from six-fold symmetry.

[0170] The obtained white powder, Cs4W11 O 35 The powder was thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800 °C in an Ar gas stream. While maintaining the temperature at 800 °C, the gas stream was switched to a mixed gas stream of 1 vol% H2 gas using Ar gas as a carrier (hereinafter, vol% will be simply described as %), and after reduction for 5 minutes, the H2 gas was stopped, and it was gradually cooled to 100 °C only with the Ar gas stream, and then the Ar gas stream was stopped and gradually cooled to room temperature, and powder A was taken out. The color tone of the taken-out powder A was light blue.

[0171] The XRD pattern of powder A showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. When the lattice constants of each phase were determined by the Rietveld method, for the orthorhombic crystal, a = 14.6609 Å, b = 52.4040 Å, c = 7.7419 Å (the hexagonal crystal conversion values are a = 7.5062 Å, c = 7.7419 Å), and for the hexagonal crystal, a = 7.4170 Å, c = 7.5752 Å. It was confirmed that the value of the c-axis was in the range of 7.560 Å ≤ c ≤ 7.750 Å.

[0172] Next, when TEM observation of powder A was performed, orthorhombic crystal particles and pseudo-hexagonal crystal particles were observed.

[0173] Here, the electron diffraction image of the pseudo-hexagonal crystal particles is shown in Fig. 5. The pseudo-hexagonal crystal particles showed a diffraction pattern close to that of a hexagonal crystal, as shown by the electron diffraction image of the

[0001] HEX zone axis in Fig. 5. Here, the interplanar angle between (200) HEX and (110) HEX was measured to be 59.2°, which was a value close to that of a hexagonal crystal.

[0174] Next, powder A was observed in the STEM-HAADF mode (STEM: scanning transmission electron microscopy, HAADF: High-angle annular dark field).

[0175] The HAADF image of the pseudo-hexagonal crystal particles observed from the

[0221] zone axis is shown in Fig. 6. In the HAADF mode, atomic grains are observed with brightness proportional to the atomic number and the probability of atomic existence in the projection direction. Therefore, the linear region along the (110) HEX identified as a W defect with the largest atomic number. Traces of such W defect regions were confirmed to spread planar along the (110) HEX by observation from another direction. Also, a part of the trace with weak contrast is considered to shrink linearly.

[0176] In this experimental example, the heat reduction treatment was set for 5 minutes, which is shorter than other experimental examples described later. At the initial stage of reduction at high temperature, the orthorhombic (010) ORTH W defects contracted and a structural transition occurred to pseudo-hexagonal crystals. In the pseudo-hexagonal crystals, many W defect regions in the process of contraction were observed on the {100} HEX plane. [Experimental Example 1-2] The Cs4W 11 O 35 powder, which is the powder A' obtained in Experimental Example 1-1, was thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800 °C in an Ar gas stream. While maintaining the temperature at 800 °C, the gas flow was switched to a mixed gas flow of 1% H2 gas with Ar gas as the carrier, and after reducing for 15 minutes, the H2 gas was stopped, and it was gradually cooled to 100 °C only with the Ar gas stream, and then the Ar gas stream was stopped and gradually cooled to room temperature, and the powder B was taken out. The color tone of the taken-out powder B was blue.

[0177] The XRD pattern of the powder B showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. When the lattice constants of each phase were determined by the Rietveld method, for the orthorhombic crystal, a = 14.6576 Å, b = 52.4315 Å, c = 7.7412 Å (the hexagonal crystal conversion values are a = 7.5088 Å, c = 7.7412 Å), and for the hexagonal crystal, a = 7.4122 Å, c = 7.5940 Å were obtained. It was confirmed that the value of the c-axis was in the range of 7 .560 Å ≤ c ≤ 7.750 Å.

[0178] Next, when the TEM observation of powder B was carried out, similar to the case of powder A obtained in Experimental Example 1-1, orthorhombic particles and pseudo-hexagonal particles were observed. The pseudo-hexagonal particles showed a diffraction pattern close to that of hexagonal crystal as shown in the electron diffraction image of the

[0001] zone axis in Fig. 7. Here, the interplanar angle between (200) HEX and (110) HEX was measured to be 59.5°, which was a value close to that of hexagonal crystal. HEX [Experimental Example 1-3] The powder A' obtained in Experimental Example 1-1, Cs4W 11 O 35 powder was thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated from room temperature to 800 °C in an Ar gas stream. While maintaining the temperature at 800 °C, the gas stream was switched to a mixed gas stream of 1% H2 gas with Ar gas as the carrier, and after reducing for 30 minutes, the H2 gas was stopped, and it was slowly cooled to 100 °C only with the Ar gas stream, and then the Ar gas stream was stopped and slowly cooled to room temperature, and powder C was taken out. The color tone of the taken-out powder C was dark blue.

[0179] The XRD pattern of powder C showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. When the lattice constants of each phase were determined by the Rietveld method, for the orthorhombic crystal, a = 14.6649 Å, b = 52.4010 Å, c = 7.7451 Å (the hexagonal crystal conversion values are a = 7.5064 Å, c = 7.7451 Å), and for the hexagonal crystal, a = 7.4076 Å, c = 7.6107 Å were obtained. It was confirmed that the value of the c-axis was in the range of 7.560 Å ≤ c ≤ 7.750 Å for both.

[0180] Next, when the TEM observation of powder C was carried out, similar to the case of powder A obtained in Experimental Example 1-1, orthorhombic particles and pseudo-hexagonal particles were observed. The pseudo-hexagonal particles showed a diffraction pattern of hexagonal crystal as shown in the electron diffraction image of the

[0001] zone axis in Fig. 8. Here, the interplanar angle between (200) HEX and (110) HEX was measured to be 60.0°, which was the value of hexagonal crystal. [Experimental Examples 1-4 to 1-7] The powder A' obtained in Experimental Example 1-1, Cs4W 11 O 35The reduction time during the reduction treatment of the powder was changed to 35 minutes to 90 minutes as shown in Table 1 to prepare Powder D, Powder E, Powder F, and Powder G. The powder color tones of Powder D to Powder G were all dark blue, and the XRD lattice constants were as shown in the table.

[0181] As shown in Table 1, in Experimental Examples 1-4, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was 7.7440 Å (Experimental Examples 1-4). [Experimental Examples 1-8 to Experimental Examples 1-11] Cs4W which is the powder A' obtained in Experimental Example 1-1 11 O 35 The heating temperature and reduction time during the heat reduction treatment of the powder were changed as shown in Table 1. Specifically, in Experimental Example 1-8, it was 650 °C for 120 minutes, in Experimental Example 1-9, it was 700 °C for 60 minutes, in Experimental Example 1-10, it was 900 °C for 10 minutes, and in Experimental Example 1-11, it was 950 °C for 20 minutes. Except for the above points, Powder H, Powder I, Powder J, and Powder K were prepared in the same manner as when preparing Powder A in Experimental Example 1-1. Powders of sky blue, blue, dark blue, and dark blue were obtained respectively. The lattice constants determined from the XRD patterns of the obtained powders were as shown in Table 1.

[0182] As shown in Table 1, in Experimental Examples 1-8 and Experimental Example 1-9, an orthorhombic phase was also observed, and the c-axis length converted to hexagonal crystal was 7.7428 Å (Experimental Example 1-8) and 7.7471 Å (Experimental Example 1-9). [Experimental Example 1-12] Cesium carbonate and tungsten trioxide were mixed at a molar ratio of Cs2CO3:WO3 = 3:11, thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated at 850 °C for 5 hours to obtain a very thin white powder with a greenish tint. The main phase of this white powder was Cs6W 11 O 36 which was identified as (ICDD1-70-632), but it was a mixed phase with Cs4W 11 O 35

[0183] The obtained white powder was heat-treated at 800 °C for 30 minutes in a 1% H2-N2 gas stream to obtain a dark blue powder L.​

[0184] The XRD pattern of powder L showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. The lattice constants determined from the obtained XRD pattern of powder L are as shown in Table 1. In addition, as described above, the orthorhombic phase was also observed, and the c-axis length converted to hexagonal was 7.7449 Å. [Experimental Example 1-13] Cesium carbonate and tungsten trioxide were mixed at a molar ratio of Cs2CO3:WO3 = 1:6, thinly and evenly spread on a carbon boat, placed in a tubular furnace, and heated at 850 °C for 5 hours to obtain a very thin greenish-white powder. The main phase of this white powder was identified as Cs4W 11 O 35 but it was a mixed phase with Cs2W6O 19 (ICDD00-045-0522).

[0185] The obtained white powder was heat-treated in a 1% H2-N2 gas stream at 800 °C for 30 minutes to obtain a dark blue powder M.

[0186] The XRD pattern of powder M showed a two-phase mixed pattern of orthorhombic and hexagonal crystals. The lattice constants determined from the obtained XRD pattern of powder M are as shown in Table 1. In addition, the orthorhombic phase was also observed, and the c-axis length converted to hexagonal was 7.7466 Å.

[0187]

Table 1

[0188] As shown in the above Experimental Example 1-1 to Experimental Example 1-13, when the white Cs4W 11 O 35 or Cs6W 11 O 36 and the powder of Cs4W 19 containing Cs2W6O 11 O 35 was reduced at high temperature, the color of the powder gradually changed from light blue to blue and then to dark blue.

[0189] Also, Cs4W 11 O35 In the phase, lattice defects including W defects exist and it is orthorhombic. However, when this is reduced at high temperature, it was confirmed that the lattice defects including W defects are reduced and disappear, and the orthorhombic crystal changes to a hexagonal crystal.

[0190] It should be noted that it has been confirmed that all of the cesium tungstate oxides contained in Powders A to M obtained in Experimental Examples 1-1 to 1-13 have W defects and O defects. [Experimental Example 2] Using the near-infrared absorbing particles produced in Experimental Example 1, a near-infrared absorbing curable ink composition and a near-infrared absorbing cured film (hereinafter, may be simply referred to as "cured film") were produced and evaluated.

[0191] Experimental Examples 2-1 to 2-14 are examples, and Experimental Examples 2-15 and 2-16 are comparative examples. [Experimental Example 2-1] 20% by mass of Powder A prepared in Experimental Example 1-1, 20% by mass of an acrylic polymer dispersant having a group containing an amine as a functional group (hereinafter abbreviated as "dispersant a"), and 60% by mass of methyl isobutyl ketone as a solvent were weighed. 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.

[0192] Here, when measuring the average particle diameter of the near-infrared absorbing particles in Dispersion A (the dispersed particle diameter measured by ELS-8000 manufactured by Otsuka Electronics Co., Ltd., a particle diameter measuring device based on the dynamic light scattering method), it was 28.2 nm.

[0193] 25 parts by mass of Dispersion A and 75 parts by mass of a thermosetting ink containing a commercially available one-component type uncured thermosetting resin (manufactured by Teikoku Ink Manufacturing Co., Ltd., MEG Screen Ink (medium)) were mixed to prepare a near-infrared curable ink composition according to Experimental Example 2-1 (hereinafter, referred to as Ink A).

[0194] Ink A was applied onto a blue plate glass with a thickness of 3 mm using a bar coater (No. 10) to form a coating film (coating step).

[0195] Next, the coating film was irradiated with near-infrared rays to obtain a near-infrared cured film (hereinafter referred to as cured film A) (curing step).

[0196] In the curing step, a line heater HYP-14N (output 980 W) manufactured by High-Vac Co., Ltd. was used as the near-infrared irradiation source. The heater was installed at a height of 5 cm from the coating surface of the coating film, and near-infrared rays were irradiated for 10 seconds.

[0197] The film thickness of the obtained cured film A was 20 μm. And it was confirmed to be transparent by visual inspection.

[0198] When the average particle diameter of the cesium tungstate oxide particles dispersed in the cured film A was calculated by an image processing apparatus using a transmission electron microscope image, it was 24 nm. The particle diameter of each particle is the diameter of the circumscribed circle of the particle, and the above average particle diameter is calculated as the average value of the particle diameters measured for 100 particles.

[0199] The adhesion of the cured film A was evaluated by the method shown below.

[0200] One hundred grid-shaped cuts were made on the cured film A using a cutter guide with a gap interval of 1 mm. Then, a tape with a width of 18 mm (Nitto Denko Corporation's cellophane tape (registered trademark) CT-18) was attached to the cut surface on the grid, and after a 2.0 kg roller was reciprocated 20 times to completely adhere it, it was rapidly peeled at a peeling angle of 180 degrees, and the number of peeled grids was counted. The number of peeled grids was 0.

[0201] Even when the cured film A was irradiated with near-infrared rays under the same conditions as those during the above-described near-infrared curable ink curing for 20 seconds, the cured film did not remelt.

[0202] Also, the spectral characteristics of the produced cured film A were measured by the reflectance of light with a wavelength of 200 nm or more and 2100 nm or less using a spectrophotometer manufactured by Hitachi, Ltd., and the color index was calculated. As a result, L * = 88, a * = -1, b * = 8, and it was confirmed that the color was a very weak blue and had a neutral color tone.

[0203] The results are shown in Table 2. Also, Table 2 also includes the results obtained in Experimental Examples 2-2 to 2-16 described later. [Experimental Examples 2-2 to 2-13] Near-infrared curable ink compositions and cured films according to Experimental Examples 2-2 to 2-13 were obtained and evaluated in the same manner as Experimental Example 2-1, except that powders B to M prepared in Experimental Examples 1-2 to 1-13 were used instead of powder A. The evaluation results are shown in Table 2. [Experimental Example 2-14] Near-infrared curable ink compositions and cured films according to Experimental Example 2-14 were obtained and evaluated in the same manner as Experimental Example 2-1, except that a methyl isobutyl ketone solution of an acrylic resin was used as the thermoplastic resin instead of the thermosetting resin according to Experimental Example 2-1. The evaluation results are shown in Table 2. [Experimental Example 2-15] Near-infrared curable ink compositions and cured films according to Experimental Example 2-15 were obtained and evaluated in the same manner as Experimental Example 2-1, except that the Cs4W 11 O 35 powder obtained in Experimental Example 1-1 was used instead of powder A. The evaluation results are shown in Table 2. [Experimental Example 2-16] An aqueous solution of cesium carbonate (Cs2CO3), tungstic acid (H2WO4), and tungsten dioxide powder (WO2) were weighed, mixed, and kneaded to prepare a raw material mixture so that the composition became Cs2O·5WO3·4WO2. After sufficient mixing, the raw material mixture was thinly and evenly spread on a carbon boat and held at 550 °C for 60 minutes under a 1% H2 gas stream with N2 gas as the carrier, then changed to a 100% N2 gas stream, held for 1 hour, heated to 800 °C, held for 1 hour, and slowly cooled to room temperature to obtain powder O. The color of powder O was dark blue. As a result of chemical analysis, the composition Cs 0.33 WO 2.74 was obtained.

[0204] The XRD pattern of powder O showed a hexagonal single phase. By Rietveld analysis, lattice constants a = 7.4088 Å and c = 7.6033 Å were obtained. The value of the c-axis of the lattice constant was within the preferred range.

[0205] Next, when TEM observation was performed, no particularly noticeable lattice defects were found. No noticeable lattice defects were observed in the STEM atomic image observation either, and no W deficiency was found.

[0206] Instead of powder A, the above Cs 0.33 WO 2.74 Near-infrared curable ink compositions and cured films according to Experimental Example 2-16 were obtained and evaluated in the same manner as in Experimental Example 2-1 except that the powder was used. The evaluation results are shown in Table 2.

[0207]

Table 2

[0208] On the other hand, the near-infrared absorbing particles contained in the cured films of Experimental Examples 2-15 and 2-16 do not contain cesium tungstate oxide that satisfies the above general formula.

[0209] And the cured film of Experimental Example 2-16 has a b * value that is negative, indicating that a bluish tint is clearly recognized. That is, it was confirmed that the cured film of Experimental Example 2-16 cannot have a neutral color tone.

[0210] Although the cured film of Experimental Example 2-15 was able to have a neutral color tone, it was confirmed from the results in Table 2 that it has poor adhesion. This is presumably because the near-infrared absorbing particles contained in the near-infrared curable ink composition used in Experimental Example 2-15 have a low solar radiation absorption rate.

Claims

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

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

3. The near-infrared curable ink composition according to claim 1 or 2, wherein the cesium tungstate has a c-axis length in terms of hexagonal crystal of 7.560 Å or more and 7.750 Å or less.

4.

5. WO that constitutes the crystal of the cesium tungsten oxide ６ The near-infrared curable ink composition according to any one of claims 1 to 3, wherein a part of O in the octahedron has a defect. A part of Cs of the cesium tungstate is substituted by an additive element, and the additive element is one or more selected from Na, Tl, In, Li, Be, Mg, Ca, Sr, Ba, Al, and Ga. The near-infrared curable ink composition according to any one of claims 1 to 4.

6. The near-infrared curable ink composition according to any one of claims 1 to 5, wherein the average particle diameter of the near-infrared absorbing particles is 0.1 nm or more and 200 nm or less.

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

8.

9. The near-infrared absorbing particles are cesium tungstate precursors nCs ２ O·mWO ３ (n and m are integers, 3.6 ≤ m / n ≤ 9.0), and the near-infrared curable ink composition according to any one of claims 1 to 7, which is obtained by heating and reducing the crystalline powder at 650°C or higher and 950°C or lower in an atmosphere of a reducing gas.

10. The near-infrared absorbing particles are particles obtained by heating and reducing a cesium tungstate precursor containing a Cs ４ W １１ O ３５ phase in an atmosphere of a reducing gas at 650°C or higher and 950°C or lower, according to any one of claims 1 to 8 of the near-infrared curable ink composition. The near-infrared curable ink composition according to any one of claims 1 to 9, further comprising one or more selected from organic pigments, inorganic pigments, and dyes.

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

12. The near-infrared curable ink composition according to any one of claims 1 to 11, further comprising a solvent.

13. A near-infrared cured film which is a cured product of the near-infrared curable ink composition according to any one of claims 1 to 12.

14. A method for producing a near-infrared cured product, comprising: a coating step of coating a near-infrared curable ink composition according to any one of claims 1 to 12 on 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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