Aggregate of hexaboride fine particles, dispersion liquid, dispersion, transparent substrate sandwiched by the dispersion, infrared absorbing film, and glass
阅读说明：本技术 六硼化物微粒的集合体、分散液、分散体、该分散体夹层透明基材、红外线吸收膜及玻璃 (Aggregate of hexaboride fine particles, dispersion liquid, dispersion, transparent substrate sandwiched by the dispersion, infrared absorbing film, and glass ) 是由 町田佳辅 常松裕史 藤田贤一 于 2015-08-28 设计创作，主要内容包括：本发明提供一种具有宽幅的近红外吸收的透明的新型近红外吸收微粒。提供一种六硼化物的微粒的集合体,在集合体所含的微粒的个数中,将粒子形状近似地看作旋转椭圆体时的长宽比[长轴长度]/[短轴长度]为1.5以上且低于5.0的微粒为20％以上且低于80％,上述长宽比为5.0以上且低于20.0的微粒存在20％以上且低于80％的六硼化物微粒集合体。(The present invention provides a novel transparent near-infrared absorbing fine particle having a wide near-infrared absorption. Provided is an aggregate of fine particles of hexaboride, wherein, among the number of fine particles contained in the aggregate, fine particles having an aspect ratio [ major axis length ]/[ minor axis length ] of 1.5 or more and less than 5.0 when the particle shape is considered as a rotational ellipsoid are 20% or more and less than 80%, and the fine particles having an aspect ratio of 5.0 or more and less than 20.0 are present in an amount of 20% or more and less than 80% of the fine particle aggregate of hexaboride.)
1. A method for producing an aggregate of fine hexaboride particles, wherein,
when the particle shape of the hexaboride fine particles contained in the aggregate is regarded as a rotational ellipsoid, when the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 1.5 or more and less than 4.0 contained in the aggregate is represented by a (number)%, and the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 4.0 or more and less than 20.0 is represented by b (number)%, 60 (number)% -100 (number)%, and a: b is 20: 80-80: 20,
the fine hexaboride particles having an average particle diameter of 0.5 to 5 [ mu ] m are pulverized by a wet bead mill using 1/3 to 1/2 beads having a Vickers hardness equal to that of the fine hexaboride particles.
2. The method for producing an aggregate of hexaboride fine particles according to claim 1, wherein,
the hexaboride particles are lanthanum hexaboride particles, and the beads are zirconia beads or alumina beads.
3. The method for producing an aggregate of hexaboride fine particles according to claim 1, wherein,
the beads are yttria stabilised zirconia beads of 0.3mm diameter.
4. The method for producing an aggregate of hexaboride fine particles according to claim 1, wherein,
the hexaboride fine particles are pulverized together with an acrylic polymer dispersant having an amino group by the wet bead mill.
5. The method for producing an aggregate of hexaboride fine particles according to claim 1, wherein,
the dispersion solvent used in the wet bead mill is an organic solvent selected from the group consisting of isopropyl alcohol, ethyl alcohol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, and n-butyl acetate.
6. The method for producing an aggregate of hexaboride fine particles according to claim 1, wherein,
the time of the pulverization treatment by the wet bead mill is 30 to 50 hours.
Technical Field
The present invention relates to an aggregate of hexaboride fine particles having good visible light transmittance and absorbing near-infrared light, a hexaboride fine particle dispersion liquid, a hexaboride fine particle dispersion, a transparent substrate sandwiched by hexaboride fine particle dispersions, an infrared absorbing film, and infrared absorbing glass.
Background
Various techniques have been proposed as a heat ray shielding technique having a good visible light transmittance, maintaining transparency, and reducing solar transmittance. Among them, the heat ray shielding technology using a dispersion of conductive fine particles has advantages such as excellent heat ray shielding properties, low cost, radio wave permeability, and high weather resistance, compared with other technologies.
For example, patent document 1 proposes an infrared-absorbing synthetic resin molded article formed by laminating a transparent synthetic resin containing tin oxide fine powder in a dispersed state or a transparent synthetic resin containing tin oxide fine powder in a dispersed state, which is molded into a sheet or a film, on a transparent synthetic resin substrate.
Patent document 2 proposes a laminated glass In which a metal such as Sn, Ti, Si, Zn, Zr, Fe, Al, Cr, Co, Ce, In, Ni, Ag, Cu, Pt, Mn, Ta, W, V, Mo, an oxide of the metal, a nitride of the metal, a sulfide of the metal, a dopant of Sb or F and the metal, or a mixture thereof is dispersed between at least 2 opposed plate glasses.
The applicant disclosed in patent documents 3 to 5 a coating liquid or a permselective film for a permselective film in which titanium nitride fine particles or hexaboride fine particles are dispersed, a heat ray shielding component dispersion, a heat ray shielding resin molded article, and the like.
Patent document 1 Japanese patent application laid-open No. 2-136230
Patent document 2 Japanese patent application laid-open No. 8-259279
Patent document 3, Japanese patent application laid-open No. 11-181336
Patent document 4 Japanese laid-open patent publication No. 2000-96034
Disclosure of Invention
Problems to be solved by the invention
However, according to the studies of the present inventors, the heat ray shielding structures such as the infrared absorbing synthetic resin molded articles disclosed in patent documents 1 and 2 have a problem that the heat ray shielding performance is insufficient when a high visible light transmittance is required.
Here, the inventors thought of hexaboride fine particles as light absorbing fine particles and a dispersion of the hexaboride fine particles. That is, it has been recognized that hexaboride fine particles and hexaboride fine particle dispersions have high transparency, high near infrared absorption ability, high molar absorption coefficient, low cost, and high weather resistance, and they are thought to be used as light absorbing fine particle dispersions and light absorbing fine particle dispersions.
Based on this idea, the present applicant has disclosed the above-mentioned patent documents 3 to 5, and has provided a coating liquid or a permselective film for a permselective film in which titanium nitride fine particles or hexaboride fine particles are dispersed, a heat ray shielding component dispersion, a heat ray shielding resin molded article, and the like.
However, the present inventors have further studied and found the following problems.
That is, the hexaboride fine particles disclosed in patent documents 3 to 5 may not sufficiently absorb light having a wavelength of around 1000nm, which has a high weight coefficient, in sunlight. Therefore, if the concentration of the hexaboride fine particles is increased to sufficiently absorb light having a wavelength around 1000nm, light in the current visible light region is also greatly absorbed. Therefore, the solar radiation shielding material may not have sufficient properties to shield solar light while transmitting visible light.
In order to solve this problem, for example, patent document 4 discloses a structure in which other types of light absorbing fine particles than hexaboride fine particles are mixed with the hexaboride fine particles. However, when light-absorbing fine particles of different types are mixed, it is difficult to select a dispersant that can stably contain a plurality of types of light-absorbing fine particles in a solvent or to select an addition method, and there is a possibility that aggregation of the light-absorbing fine particles occurs during mixing. As a result, there are many problems in quality control as follows: it is necessary to sufficiently perform a difficult mixing and dispersing operation of the light-absorbing fine particles and the dispersing agent, and finally, the influence on the medium such as a resin containing the light-absorbing fine particles differs depending on the kind of each light-absorbing fine particle and also on the progressing state of the kind of each light-absorbing fine particle with time.
The present invention has been made under the above circumstances, and an object of the present invention is to provide an aggregate of hexaboride fine particles, a hexaboride fine particle dispersion liquid, a hexaboride fine particle dispersion interlayer transparent substrate, an infrared ray absorbing film, and an infrared ray absorbing glass, in which selectivity of absorption wavelength is controlled and which have sufficient characteristics as a solar radiation shielding material for shielding sunlight.
Means for solving the problems
The present inventors have made studies to solve the above problems.
Moreover, it is recognized that: in the hitherto known fine hexaboride particles or fine hexaboride particle dispersions of the prior art using the same, no studies have been made on a technical means for controlling the shape of the fine particles.
Further, the reason why the hexaboride fine particles disclosed in the above patent documents 3 to 5 may not sufficiently absorb light having a wavelength of about 1000nm with a high weight coefficient in sunlight is considered to be that: since the control of the particle shape is not taken into consideration in the granulation of the fine hexaboride particles, the shape of the particles to be produced or the ratio of the particles having each shape to be present are not appropriate.
For example, patent document 3 or
Similarly, patent document 4 discloses only the following steps of preparing a dispersion of boride fine particles in examples: boride fine particles having an average particle diameter of 85 to 120nm are mixed with an organic solvent and a coupling agent for fine particle dispersion, and are mixed by a ball mill using zirconia beads having a diameter of 4mm, and the shape of particles in the form of a dispersion or a coating film is not particularly mentioned.
In other known documents, the control of the particle shape of hexaboride and its effect are not substantially beyond the range described in the above patent documents 3 to 5. That is, in the hexaboride fine particles, the light absorption characteristics exhibited by the dispersion when the hexaboride fine particles are dispersed by a technique of controlling the respective fine particles to a predetermined shape are not completely clear.
The present inventors have further studied under the above-described knowledge.
Further, as will be described in detail later, when the aspect ratio of the hexaboride fine particles is considered by considering the particle shape of the hexaboride fine particles as a rotational ellipsoid, it is recognized that the hexaboride fine particles having an aspect ratio of 1.5 or more and less than 4.0 have a main absorption peak for light having a wavelength of 900 to 1000 nm. Thus, visible light is transmitted while on the other hand sunlight can be effectively shielded. However, it was recognized that the hexaboride fine particles could not sufficiently absorb light having a wavelength longer than 1100nm, which has a high weight coefficient, in sunlight.
Further, since the hexaboride fine particles having an aspect ratio of 4.0 or more and less than 20.0 have a main absorption peak in light having a wavelength of 1000 to 2000nm, visible light is transmitted, and sunlight can be efficiently shielded. However, it is recognized that the hexaboride fine particles cannot sufficiently absorb light having a wavelength of 800 to 1000nm, which has a high weight coefficient of sunlight.
On the other hand, the hexaboride fine particles having an aspect ratio of less than 1.5 have a main absorption peak at a wavelength of 700 to 900 nm. Therefore, light near 1000nm, which has a high weight coefficient of sunlight, is not sufficiently absorbed, and light in the visible light region is also greatly absorbed. Therefore, the properties as a solar radiation shielding material are not sufficient.
Based on this finding, the present inventors thought: when hexaboride fine particles having an aspect ratio of 1.5 or more and less than 4.0 and hexaboride fine particles having an aspect ratio of 4.0 or more and less than 20.0 are mixed at a predetermined ratio to prepare an aggregate, an aggregate of hexaboride fine particles which transmits visible light and has a wide absorption in a near infrared region where the weight coefficient of sunlight is high can be obtained.
Specifically, it is recognized that: in an aggregate of hexaboride fine particles present in a field of view of a specified TEM tomography image or a dispersion thereof, the particle shape of the hexaboride fine particles present in the field of view is regarded as a rotational ellipsoid, and when the number of all hexaboride fine particles present in the field of view is 100 (number)%, the proportion of the number of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 1.5 or more and less than 4.0 is a (number)%, the proportion of the number of hexaboride fine particles having an aspect ratio of 4.0 or more and less than 20.0 is b (number)%, the values of a and b satisfy 60 (number)% < a + b) (number)% < 100 (number)%, and a: b < 20:80 to 80:20, the hexaboride fine particle aggregate and the dispersion having the hexaboride fine particle aggregate dispersed therein have very good sunlight shielding properties, and the present invention has been completed.
Note that the "aggregate" in the present invention is used as a concept as follows: the term "substance" means a substance in which 1 particle and 1 particle having each form are present in a large amount in the same space and the state thereof. On the other hand, in the present invention, it is not used as a concept meaning a substance in which a plurality of fine particles form an aggregate with each other and a state thereof.
That is, the invention 1 to solve the above problems is an aggregate of fine hexaboride particles, wherein,
when the particle shape of the fine hexaboride particles contained in the aggregate is regarded as a rotational ellipsoid,
when the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 1.5 or more and less than 4.0 contained in the aggregate is represented by a (number)%, and the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 4.0 or more and less than 20.0 is represented by b (number)%, 60 (number)% < a + b) (number)% < 100% (number)%, and a: b is 20:80 to 80: 20.
The invention 2 is the assembly of hexaboride fine particles according to claim 1, wherein,
the average dispersed particle diameter of the hexaboride fine particles contained in the above-mentioned aggregate of hexaboride fine particles is 1nm or more and 100nm or less.
The invention 3 is the assembly of hexaboride fine particles according to claim 1 or 2, wherein,
the hexaboride particles are lanthanum hexaboride particles.
The invention of claim 4 is a hexaboride fine particle dispersion liquid in which an aggregate of hexaboride fine particles according to any one of claims 1 to 3 is dispersed in a liquid medium,
the liquid medium is selected from: water, an organic solvent, an oil or fat, a liquid resin, a plasticizer for liquid plastics, or a mixture of 2 or more selected from these media.
The 5 th aspect of the invention is the hexaboride fine particle dispersion according to the 4 th aspect of the invention, which contains the hexaboride fine particles in an amount of 0.02 mass% to 20 mass%.
The invention 6 is a hexaboride microparticle dispersion wherein,
an aggregate of the hexaboride fine particles according to any one of claims 1 to 4 dispersed in a thermoplastic resin or a UV curable resin.
The 7 th invention is the hexaboride microparticle dispersion according to the 6 th invention, wherein,
the thermoplastic resin is any of the following:
1 resin selected from the group consisting of polyethylene terephthalate resins, polycarbonate resins, acrylic resins, styrene resins, polyamide resins, polyethylene resins, vinyl chloride resins, olefin resins, epoxy resins, polyimide resins, fluorine resins, ethylene-vinyl acetate copolymers, polyvinyl acetal resins, or a mixture of 2 or more resins selected from the group of the resins, or a copolymer of 2 or more resins selected from the group of the resins.
The 8 th aspect of the invention is the hexaboride fine particle dispersion according to the 6 th or 7 th aspect of the invention, which contains the hexaboride fine particles in an amount of 0.001 to 80.0 mass%.
The 9 th aspect of the invention is the hexaboride fine particle dispersion according to any one of the 6 th to 8 th aspects of the invention,
the hexaboride particle dispersion is in the form of a sheet, plate or film.
The invention according to
the content of the hexaboride fine particle dispersion per projected area contained in the hexaboride fine particle dispersion was 0.01g/m2Above and 0.5g/m2The following.
The 11 th invention is a hexaboride particle dispersion interlayer transparent substrate comprising:
a plurality of transparent base materials, and the hexaboride microparticle dispersion according to any one of claims 6 to 10 present between the plurality of transparent base materials.
The 12 th invention is an infrared absorbing film or an infrared absorbing glass, wherein,
the hexaboride fine particle dispersion according to any one of the inventions 6 to 10 is provided as a coating on at least one surface of a transparent substrate selected from a transparent film substrate or a transparent glass substrate.
The 13 th invention is the infrared absorbing film or the infrared absorbing glass according to the 12 th invention, wherein,
the resin is a UV curable resin.
The 14 th invention is the infrared absorbing film or the infrared absorbing glass according to the 12 th or 13 th invention, wherein a thickness of the coating layer is 10 μm or less.
The 15 th invention is the infrared absorbing film according to any one of the 12 th to 14 th inventions, wherein,
the transparent film substrate is a polyester film.
The 16 th invention is the infrared absorbing film or the infrared absorbing glass according to any one of the 12 th to 15 th inventions, wherein,
the content of the hexaboride particles per unit projected area contained in the coating layer is 0.01g/m2Above and 0.5g/m2The following.
Effects of the invention
According to the hexaboride fine particle aggregate, the hexaboride fine particle dispersion liquid, the hexaboride fine particle dispersion, the transparent substrate with the hexaboride fine particle dispersion interlayer, the infrared ray absorbing film and the infrared ray absorbing glass of the present invention, hexaboride fine particles are used, and the transparent substrate has broad absorption characteristics in a near infrared wavelength region and has suitable characteristics as a solar radiation shielding material.
Drawings
FIG. 1 is a TEM tomographic image of an aggregate dispersed in a lanthanum hexaboride microparticle dispersion of example 1.
Fig. 2 is a frequency distribution of the aspect ratio of the hexaboride fine particles contained in the aggregate dispersed in the lanthanum hexaboride fine particle dispersion of example 1.
FIG. 3 is a graph showing the optical properties of the dispersions of examples and comparative examples.
Fig. 4 is a 30000-fold TEM image of the lanthanum hexaboride fine particle of comparative example 1.
Detailed Description
Hereinafter, embodiments of the present invention will be described in the following order: [a] hexaboride fine particles, [ b ] an aggregate of hexaboride fine particles, [ c ] a method for producing an aggregate of hexaboride fine particles, [ d ] a dispersion of hexaboride fine particles and a method for producing the same, [ e ] a dispersion of hexaboride fine particles and a method for producing the same, [ f ] a dispersion of hexaboride fine particles in a sheet or film form and a method for producing the same, [ g ] a transparent substrate laminated with a dispersion of hexaboride fine particles and a method for producing the same, [ h ] an infrared absorbing film and an infrared absorbing glass and a method for producing the same.
[a] Fine particles of hexaboride
The fine hexaboride particles used in the present invention exhibit absorption of light in the near infrared region due to plasmon absorption. Its composition is represented by formula XB6Meaning that the shape has a non-spherical shape.
Here, the element X is preferably at least 1 or more selected from La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Y, Sm, Eu, Er, Tm, Yb, Lu, Sr, and Ca. Specifically, there may be mentioned: lanthanum hexaboride [ LaB ]6]Cerium hexaboride [ CeB ]6]Praseodymium hexaboride [ PrB ]6]Neodymium hexaboride [ NdB ]6]Gadolinium hexaboride [ GdB6]Terbium hexaboride [ TbB ]6]Dysprosium hexaboride [ DyB6]Holmium hexaboride [ HoB6]Yttrium hexaboride [ YB ]6]Samarium hexaboride [ SmB ]6]Europium hexaboride [ EuB ]6]Erbium hexaboride [ ErB6]Thulium hexaboride [ TmB6]YbB, YbB6]LuB hexaboride [ LuB ]6]Lanthanum cerium hexaboride [ (La, Ce) B [ ]6]Strontium hexaboride [ SrB ]6]Calcium hexaboride [ CaB6]And the like as representative substances thereof. Among them, lanthanum hexaboride [ LaB ] is preferably used because of its high intensity of near infrared absorption with respect to visible light absorption6]。
In the fine boride particles used in the present invention, the surface thereof is preferably not oxidized, and usually, the surface is slightly oxidized. In addition, the oxidation of the surface in the dispersion step of the hexaboride fine particles is inevitable to some extent. However, even in this case, the effectiveness of exhibiting the near infrared ray shielding effect does not change. Therefore, even when the fine hexaboride particles are surface-oxidized, for example, the fine hexaboride particles used in the present invention can be used.
In addition, the higher the integrity of the crystal as the hexaboride fine particles used in the present invention is, the greater the heat ray shielding effect can be obtained. However, even when the hexaboride fine particles have low crystallinity and generate a broad diffraction peak by X-ray diffraction, the hexaboride fine particles can be used in the present invention because the heat ray shielding effect is exhibited as long as the basic bond inside the fine particles is formed by bonding of each metal and boron. The hexaboride is not strictly required to have a metal to boron ratio of 6, and may be in the range of 5.8 to 6.2.
[b] Aggregate of fine particles of hexaboride
The fine boride particle aggregate of the present invention is composed of an aggregate of fine boride particles having a particle shape in a predetermined range.
Here, the characteristics of the hexaboride microparticles contained in the assembly of hexaboride microparticles will be described with reference to fig. 1, which is a TEM tomographic image of the lanthanum hexaboride microparticle assembly of example 1 described later. As a method for producing a hexaboride fine particle dispersion and a method for producing a hexaboride fine particle dispersion, which will be described later, it was found that: the characteristics of the hexaboride fine particles contained in the hexaboride fine particle aggregate are the same as those of the hexaboride fine particles in the hexaboride fine particle dispersion liquid and the hexaboride fine particle dispersion.
First, the particle shape of the hexaboride fine particles contained in the aggregate is regarded as a rotational ellipsoid, and the aspect ratio [ (major axis length)/(minor axis length) ] of the hexaboride fine particles is considered.
In this case, when the number ratio of hexaboride fine particles contained in the aggregate, which have an aspect ratio of 1.5 or more and less than 4.0, is expressed as a (number)%, and the number ratio of hexaboride fine particles, which have an aspect ratio [ (major axis length)/(minor axis length) ] of 4.0 or more and less than 20.0, is expressed as b (number)%, (a + b) (number)% is 60 (number)% or more and 100 (number)% or less. The ratio of a to b is in the range of 20:80 to 80:20, and more preferably in the range of 30:70 to 70: 30.
The aspect ratio of the hexaboride fine particles is determined by the following method: the aspect ratio [ (major axis length)/(minor axis length) ] of each hexaboride microparticle was calculated by identifying each hexaboride microparticle from a 3-dimensional image obtained by TEM tomography and comparing the length scale of the 3-dimensional image with the specific shape of the particle.
Specifically, 100 or more, preferably 200 or more hexaboride microparticles are identified from the 3-dimensional image. For each of the identified hexaboride fine particles, the directions of the major axis and the minor axis are determined (the longest axis perpendicular to each other is defined as the major axis, and the shortest axis is defined as the minor axis), the lengths of the major axis and the minor axis are measured, and the aspect ratio is calculated from the measured values.
As described above, the hexaboride fine particles having an aspect ratio of less than 1.5 have their main absorption peak at a wavelength of 700 to 900 nm. Therefore, light near 1100nm, which has a high weight coefficient of sunlight, is not sufficiently absorbed, and light in the visible light region is also greatly absorbed. Therefore, the properties as a solar radiation shielding material are not sufficient.
On the other hand, the hexaboride fine particles having an aspect ratio of 1.5 or more and less than 4.0 have a main absorption peak at a wavelength of 900 to 1000 nm. Therefore, while light can be transmitted and sunlight can be effectively shielded, light having a high weight coefficient of sunlight and longer than the wavelength of 1100nm cannot be sufficiently absorbed.
Also, the hexaboride fine particles having an aspect ratio of 4.0 or more and less than 20.0 have a main absorption peak at a wavelength of 1000 to 2000nm, and can transmit visible light, while they can effectively shield sunlight, but cannot sufficiently absorb light having a high weight coefficient of sunlight at a wavelength of 800 to 1000 nm.
In addition, fine hexaboride particles having an aspect ratio of 20.0 or more are hardly present.
Based on the above findings, the present inventors have found that: when the value of (a + b)% by number in the aggregate of hexaboride fine particles is 60% by number or more and the ratio of a to b is in the range of 20:80 to 80:20, the aggregate of hexaboride fine particles of the present invention uses hexaboride fine particles as light absorbing fine particles, but has broad absorption characteristics in the near infrared wavelength region and exhibits suitable characteristics as a solar radiation shielding material.
[c] Method for producing aggregate of fine hexaboride particles
The aggregate of hexaboride fine particles of the present invention and a method for producing the same will be described. The method for producing the assembly of hexaboride fine particles is not limited to the above example, and any method may be used as long as the shape characteristics and the existence ratio of the fine particles constituting the assembly of hexaboride fine particles of the present invention can be implemented.
Fine particles of a hexaboride compound having an average particle diameter of 0.5 to 5 μm are prepared, and the mixture is charged into a mill (for example, a solvent diffusion mill) together with a grinding medium (hereinafter, may be simply referred to as beads) having a lower hardness than the fine particles, a dispersion medium (for example, an organic solvent such as isopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, or n-butyl acetate), and an appropriate dispersant (for example, a polymer dispersant) as desired, and ground by a bead mill. In this case, the mill is operated at a peripheral speed lower than that in the usual pulverization (for example, about 0.3 to 0.8 times that in the usual pulverization), and wet pulverization is carried out by a low shearing force in the presence of a dispersion medium and an appropriate dispersant added as desired.
By wet grinding using such a low shearing force, when the particle shape of the hexaboride fine particles contained in the aggregate of hexaboride fine particles is regarded as a rotational ellipsoid, when the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 1.5 or more and less than 4.0 contained in the aggregate is represented by a (number)%, and the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 4.0 or more and less than 20.0 is represented by b (number)%, an aggregate satisfying 60 (number)% < a + b) (number)% < 100 (number)%, and a: b 20: 80:20 can be produced.
The reason why the assembly of the fine hexaboride particles of the present invention can be produced under the above production conditions is not clear. However, the reason for this is considered to be that, by selecting the hardness of the beads and the peripheral speed of the bead mill as described above, the mode of breaking the hexaboride fine particles having a cubic crystal structure and having a very high hardness is a mode of peeling off scale-like fragments having a high aspect ratio from the particle surface, and is not a mode of breaking the hexaboride fine particles by applying an impact over the entire particles.
On the other hand, a method of preparing coarse (for example, having a particle diameter of 1 μm or more) hexaboride fine particles, loading the fine particles into a mill together with a dispersion medium and a dispersant using a grinding medium harder than the fine particles, and applying high peripheral speed to wet grind the fine particles with a strong shearing force is not preferable for producing the aggregate of the present invention.
This is because the aggregate of the fine hexaboride particles pulverized by such a strong load contains a large amount of substantially spherical particles having an aspect ratio of less than 1.5.
The reason why the fine hexaboride particles are roughly nearly spherical particles having an aspect ratio of less than 1.5 is considered to be that: the mode of destruction of the hexaboride particles is a mode of impacting the whole particle and crushing it, and is not a mode of peeling off scale-like fragments having a high aspect ratio from the particle surface.
On the other hand, when the coarse hexaboride fine particles are subjected to wet grinding using a grinding medium having a hardness lower than that of the fine particles themselves and a low shearing force in the presence of a dispersion medium and a dispersant, it is not possible to produce an aggregate of fine particles having a high aspect ratio. It is believed to be because: when the hardness of the grinding media is lower than that of the hexaboride fine particles and the hardness difference between the hexaboride fine particles and the grinding media is too large, the grinding media themselves are ground by the hexaboride fine particles and the grinding force on the hexaboride fine particles is lost before the hexaboride fine particles are subjected to a destruction mode of peeling off scale-like fragments from the particle surfaces.
According to the above studies, it is possible to efficiently produce an aggregate of hexaboride fine particles having a predetermined aspect ratio by using a grinding medium having a vickers hardness of about 1/3 to 1/2 with respect to the vickers hardness of the hexaboride fine particles.
In particular, the method of manufacturing a semiconductor device,for example lanthanum hexaboride as a preferred example of hexaboride has a Vickers hardness of 2770kg/mm2The hardness of the grinding medium suitable for efficiently producing the aggregate of lanthanum hexaboride fine particles of the present invention is 920kg/mm2～1850kg/mm2Left and right. Namely, zirconia beads (1100 kg/mm)2～1300kg/mm2) Alumina beads (1000 kg/mm)2～1100kg/mm2) And the like are suitable. On the other hand, if it is a glass bead (550 kg/mm)2About) and the hardness is too low, and the resulting beads are unsuitable for use (2300 kg/mm)2Left and right) or diamond beads (7000 kg/mm)2Left or right) hardness is too high to be suitable.
Among the mills used for producing the above-mentioned aggregate of hexaboride fine particles, a ball mill, a three-roll mill, and a sand mill are preferable as the bead mill. Ball mills, three-roll mills, sand mills are often used to produce non-spherical (generally flat, scaly) particles of metals or metal compounds such as aluminum or nickel. However, since the hexaboride fine particles are generally very high in hardness and rigidity and hardly cause plastic deformation, it is considered that it is very difficult to process spherical fine particles of hexaboride into non-spherical particles by plastic deformation.
The method for producing the assembly of fine hexaboride particles of the present invention is explained above. The above-mentioned production method is merely an example, and hexaboride fine particles produced by a wet method in which the shape is controlled or hexaboride fine particles produced by a plasma gun method in which the shape can be controlled can be used. In any case, the following methods can be preferably used: when the particle shape of the hexaboride fine particles contained in the aggregate is regarded as a rotational ellipsoid when the aggregate finally becomes an aggregate of hexaboride fine particles, when the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 1.5 or more and less than 4.0 contained in the aggregate is represented by a (number)%, and the number proportion of hexaboride fine particles having an aspect ratio [ (major axis length)/(minor axis length) ] of 4.0 or more and less than 20.0 is represented by b (number)%, 60 (number)% < a + b) (number)% < 100 (number)%, and a: b is 20:80 to 80: 20.
The average particle diameter of the fine particles contained in the aggregate of hexaboride fine particles of the present invention is preferably 200nm or less. This is because, if the average particle diameter is 200nm or less, transparency can be effectively maintained while maintaining visibility in the visible light region without completely shielding light by scattering when a hexaboride fine particle dispersion described later is produced.
In the hexaboride fine particles of the present invention, when importance is attached to transparency in the visible light region in particular, it is more preferable to consider reduction of scattering by the hexaboride fine particles.
When the scattering by the hexaboride fine particles is considered to be reduced, the average particle diameter of the hexaboride fine particles may be 100nm or less. This is because the smaller the dispersed particle size of the hexaboride fine particles is, the less the geometrical scattering or the light scattering in the visible light region having a wavelength of 400nm to 780nm due to mie scattering is. As a result of this reduction in light scattering, the below-described dispersion of hexaboride fine particles can avoid the problem of the occurrence of ground glass, which makes it impossible to obtain clear transparency.
This is because when the average particle size of the hexaboride fine particles is 100nm or less, the geometric scattering or mie scattering is reduced, and the hexaboride fine particles become a rayleigh scattering region. In the rayleigh scattering region, since scattered light decreases in inverse proportion to the 6 th power of the particle size, scattering decreases with a decrease in the average particle size of the hexaboride fine particles, and transparency improves. Further, it is preferable that the average particle diameter of the fine hexaboride particles is 50nm or less because scattered light is extremely small. From the viewpoint of avoiding scattering of light, it is preferable that the average particle size of the hexaboride fine particles is small, and if the average particle size is 1nm or more, industrial production is easy.
Further, it is preferable to coat the surface of the hexaboride fine particles with an oxide containing any one or more of Si, Ti, Zr, and Al because the weather resistance can be further improved.
[d] Hexaboride microparticle dispersion and process for producing the same
The fine hexaboride particle dispersion of the present invention can be obtained by dispersing the aggregate of fine hexaboride particles of the present invention in a liquid medium.
The following describes a method for producing a dispersion of fine hexaboride particles. In the present invention, the dispersion of the fine hexaboride particles may be referred to simply as "dispersion".
The fine hexaboride particle dispersion of the present invention can be obtained by adding the aggregate of fine hexaboride particles of the present invention and an appropriate amount of a dispersant, a coupling agent, a surfactant, and the like, which are added as desired, to a liquid medium and performing dispersion treatment. The medium of the fine boride particle dispersion is required to have a function of maintaining the dispersibility of the fine boride particle dispersion and a fine boride particle dispersion described later, and a function of preventing defects when the fine boride particle dispersion is used.
(1) Medium
The hexaboride fine particle dispersion can be produced by selecting water, an organic solvent, an oil or fat, a liquid resin, a liquid plasticizer for plastics, or a mixture of 2 or more kinds selected from these as a medium. As the organic solvent satisfying the above requirements, various organic solvents such as alcohols, ketones, hydrocarbons, glycols, and water can be selected. Specifically, there may be mentioned: alcohol solvents such as methanol, ethanol, 1-propanol, isopropanol, butanol, pentanol, benzyl alcohol, diacetone alcohol, etc.; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isobutyl ketone, cyclohexanone, and isophorone; ester solvents such as 3-methyl-methoxy-propionate; glycol derivatives such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol methyl ether acetate, and propylene glycol ethyl ether acetate; amides such as formamide, N-methylformamide, dimethylformamide, dimethylacetamide, and N-methyl-2-pyrrolidone; aromatic hydrocarbons such as toluene and xylene; vinyl chloride, halogenated hydrocarbons such as chlorobenzene, and the like. Among these, organic solvents having low polarity are preferable, and particularly, isopropyl alcohol, ethanol, 1-methoxy-2-propanol, dimethyl ketone, methyl ethyl ketone, methyl isobutyl ketone, toluene, propylene glycol monomethyl ether acetate, n-butyl acetate and the like are more preferable. These solvents may be used in 1 kind or in combination of 2 or more kinds.
As the liquid resin, methyl methacrylate and the like are preferable. As the liquid plasticizer for plastics, preferred examples include plasticizers of compounds of monohydric alcohols and organic acid esters, plasticizers of esters such as polyhydric alcohol organic acid ester compounds, and plasticizers of phosphoric acids such as organic phosphoric acid plasticizers. Among them, triethylene glycol di-2-ethylhexanoate, triethylene glycol di-2-ethylbutyrate, and tetraethylene glycol di-2-ethylhexanoate are more preferable because of their low hydrolyzability.
(2) Dispersing agent, coupling agent and surfactant
The dispersant, the coupling agent, and the surfactant may be selected depending on the intended use, and preferably have an amine-containing group, a hydroxyl group, a carboxyl group, or an epoxy group as a functional group. These functional groups are adsorbed on the surfaces of the hexaboride fine particles, and have an effect of preventing aggregation of the hexaboride fine particle aggregate and uniformly dispersing the hexaboride fine particles in a hexaboride fine particle dispersion described later.
Examples of the dispersant that can be preferably used include, but are not limited to, phosphate ester compounds, polymer dispersants, silane coupling agents, titanate coupling agents, and aluminum coupling agents. Examples of the polymer dispersant include: acrylic polymer dispersants, polyurethane polymer dispersants, acrylate-block copolymer polymer dispersants, polyether dispersants, polyester polymer dispersants, and the like.
The amount of the dispersant to be added is preferably in the range of 10 to 1000 parts by weight, more preferably in the range of 20 to 200 parts by weight, based on 100 parts by weight of the hexaboride fine particle assembly. When the amount of the dispersant added is within the above range, the dispersion stability is maintained without causing aggregation of the hexaboride fine particle aggregate in the liquid.
The method of the dispersion treatment may be arbitrarily selected from known methods as long as the particle aggregates of hexaboride are uniformly dispersed in the liquid medium, and for example, a method such as bead mill, ball mill, sand mill, ultrasonic dispersion, or the like may be used.
Various additives or dispersants may be added or pH adjustment may be performed in order to obtain a uniform dispersion of the fine hexaboride particles.
(3) Hexaboride microparticle dispersion
The content of the hexaboride fine particles in the hexaboride fine particle dispersion is preferably 0.02 to 20% by mass. When the content is 0.02% by mass or more, it can be preferably used for the production of a coating film, a plastic molded article, or the like, which will be described later, and when the content is 20% by mass or less, industrial production is easy. More preferably 0.5 mass% or more and 20 mass% or less.
The dispersion of the fine hexaboride particles of the present invention obtained by dispersing the fine hexaboride particles in a liquid medium can be put in an appropriate transparent container and measured by using a spectrophotometer as a function of the light transmittance as a wavelength. The hexaboride fine particle dispersion of the present invention has a main absorption peak in the vicinity of approximately 850 to 1300nm in wavelength, and has excellent optical properties optimum for a transparent substrate, an infrared absorbing glass, an infrared absorbing film, and the like, which will be described later, in which the value of the ratio of the absorbance of light at the absorption peak position to the absorbance of light at 550nm in wavelength [ (absorbance of light at the absorption peak position)/(absorbance of light at 550nm in wavelength) ] is 5.0 to 12.0.
In this measurement, the transmittance of the hexaboride fine particle dispersion is easily adjusted by diluting with the dispersion solvent or an appropriate solvent having compatibility with the dispersion solvent.
[e] Hexaboride microparticle dispersion and process for producing the same
A hexaboride microparticle dispersion comprises the hexaboride microparticles and a thermoplastic resin or a UV curable resin.
The thermoplastic resin is not particularly limited, and is preferably any of the following: 1 resin selected from the group consisting of polyethylene terephthalate resin, polycarbonate resin, acrylic resin, styrene resin, polyamide resin, polyethylene resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluororesin, ethylene-vinyl acetate copolymer, polyvinyl acetal resin, or
A mixture of 2 or more resins selected from the above-mentioned resin group, or
A copolymer of 2 or more resins selected from the group of resins.
On the other hand, the UV curable resin is not particularly limited, and for example, an acrylic UV curable resin can be preferably used.
The amount of the hexaboride fine particles dispersed in the hexaboride fine particle dispersion is preferably 0.001 mass% or more and 80.0 mass% or less, and more preferably 0.01 mass% or more and 70 mass% or less. When the content of the hexaboride fine particles is less than 0.001% by mass, the hexaboride fine particle dispersion needs to be increased in thickness in order to obtain a desired infrared shielding effect, and when the content of the hexaboride fine particles exceeds 80% by mass, the proportion of the thermoplastic resin component in the hexaboride fine particle dispersion may be decreased and the strength may be lowered.
In addition, from the viewpoint of obtaining the infrared shielding effect from the hexaboride fine particle dispersion, the content of the hexaboride fine particles per projected area contained in the hexaboride fine particle dispersion is preferably 0.01g/m2Above and 0.5g/m2The following. The "content per projected area" is the unit area (m) through which light passes in the hexaboride microparticle dispersion of the present invention2) The weight (g) of the hexaboride fine particles contained in the thickness direction thereof.
The hexaboride fine particle dispersion may be processed into a sheet, plate or film form and may be applied to various uses.
The following describes a method for producing a fine hexaboride particle dispersion.
When the thermoplastic resin or the plasticizer and the dispersion of the hexaboride fine particles are mixed and the solvent component is removed, a dispersion powder of the hexaboride fine particles (hereinafter, may be simply referred to as a dispersion powder) as a dispersion in which the hexaboride fine particles are dispersed at a high concentration in the thermoplastic resin and/or the dispersant, or a dispersion in which the hexaboride fine particles are dispersed at a high concentration in the plasticizer (hereinafter, may be simply referred to as a plasticizer dispersion liquid) can be obtained. As a method for removing the solvent component from the hexaboride fine particle dispersion, it is preferable to dry the hexaboride fine particle dispersion under reduced pressure. Specifically, the dispersion powder or the plasticizer dispersion is separated from the solvent component by reducing the pressure of the hexaboride fine particle dispersion while stirring. The device used for the reduced pressure drying is not particularly limited as long as it is a vacuum agitation type dryer and has the above-described functions. The pressure value at the time of pressure reduction in the drying step can be appropriately selected.
By using this reduced-pressure drying method, the removal efficiency of the solvent from the hexaboride fine particle dispersion liquid is improved, and the hexaboride fine particle dispersion powder or the plasticizer dispersion liquid is not exposed to high temperature for a long time, and therefore, aggregation of the hexaboride fine particle aggregates dispersed in the dispersion powder or the plasticizer dispersion liquid is not caused, which is preferable. Also, the productivity of the hexaboride fine particle dispersion powder or the hexaboride fine particle plasticizer dispersion liquid is improved, and it is easy to recover the evaporated solvent, and it is also preferable from the viewpoint of the environment.
In the hexaboride fine particle dispersed powder or the hexaboride fine particle plasticizer dispersion liquid obtained after the drying step, the residual solvent is preferably 5 mass% or less. This is because, if the residual solvent is 5 mass% or less, bubbles are not generated when the hexaboride fine particle dispersion powder or the hexaboride fine particle plasticizer dispersion liquid is processed into, for example, a transparent substrate sandwiched by hexaboride fine particle dispersions described later, and the appearance and optical characteristics are favorably maintained.
Further, a master batch can be obtained by dispersing a dispersion liquid of hexaboride fine particles or a dispersion powder of hexaboride fine particles in a resin and granulating the resin.
Further, a master batch can also be obtained by processing into pellets by the following method: the hexaboride fine particle dispersion liquid or the hexaboride fine particle dispersion powder, the thermoplastic resin powder particles or granules, and other additives added as needed are uniformly mixed, and then kneaded by a belt type single-shaft or twin-shaft extruder, and a strand obtained by ordinary melt extrusion is cut. In this case, the shape may be a cylindrical shape or a prismatic shape. In addition, a so-called hot cutting method of directly cutting the molten extrudate may be employed. In this case, a shape close to a sphere is generally adopted.
[f] Sheet-like or film-like dispersion of hexaboride particles and process for producing the same
The hexaboride fine particle dispersion powder, the hexaboride fine particle dispersion liquid, or the master batch of the present invention is uniformly mixed with a transparent resin to produce a sheet-like, plate-like, or film-like hexaboride fine particle dispersion of the present invention. The transparent substrate, infrared absorbing film, and infrared absorbing glass having a layer of the hexaboride fine particle dispersion sandwiched therebetween can be produced from the hexaboride fine particle dispersion in the form of a sheet, a plate, or a film.
When the hexaboride fine particle dispersion in a sheet, plate or film form is produced, various thermoplastic resins can be used as the resin constituting the sheet or film. Further, the sheet-like, plate-like or film-like dispersion of hexaboride fine particles is preferably a thermoplastic resin having sufficient transparency.
Specifically, a preferable resin can be selected from the following: a resin selected from the group consisting of polyethylene terephthalate resins, polycarbonate resins, acrylic resins, styrene resins, polyamide resins, polyethylene resins, vinyl chloride resins, olefin resins, epoxy resins, polyimide resins, fluorine resins, and ethylene-vinyl acetate copolymers, or a mixture of 2 or more resins selected from the group of resins, or a copolymer of 2 or more resins selected from the group of resins.
When the sheet-like, plate-like or film-like dispersion of hexaboride fine particles is used as the intermediate layer and the thermoplastic resin constituting the sheet, plate or film alone does not have sufficient flexibility or adhesion to the transparent substrate, for example, when the thermoplastic resin is a polyvinyl acetal resin, it is more preferable to add a plasticizer.
As the plasticizer, a substance used as a plasticizer for the thermoplastic resin of the present invention can be used. Examples of plasticizers used for the infrared absorbing film made of a polyvinyl acetal resin include: a plasticizer which is a compound of monohydric alcohol and an organic acid ester, a plasticizer which is an ester such as a polyhydric alcohol organic acid ester compound, and a plasticizer which is a phosphoric acid such as an organic phosphoric acid plasticizer. Any plasticizer is preferably liquid at room temperature. Among them, a plasticizer as an ester compound synthesized from a polyhydric alcohol and a fatty acid is preferable.
The hexaboride fine particle dispersion powder or the dispersion liquid or the master batch of hexaboride fine particles, the thermoplastic resin, and optionally other additives such as a plasticizer are kneaded, and then the kneaded product is molded into a sheet-like hexaboride fine particle dispersion having a planar or curved surface by a known method such as extrusion molding or injection molding.
A known method can be used for forming the sheet-like or film-like dispersion of hexaboride particles. For example, a calender roll method, an extrusion method, a casting method, a blow molding method, or the like can be used.
[g] Transparent substrate with hexaboride microparticle dispersion interlayer and method for producing same
A description will be given of a hexaboride fine particle dispersion-laminated transparent substrate formed by interposing a sheet-like, plate-like or film-like hexaboride fine particle dispersion as an intermediate layer between a plurality of transparent substrates made of a material such as plate glass or plastic.
The transparent substrate having a hexaboride fine particle dispersion interlayer is formed by sandwiching an intermediate layer from both sides thereof with a transparent substrate. As the transparent substrate, plate glass, plate plastic, or film plastic transparent in the visible light region can be used. The material of the plastic is not particularly limited, and may be selected according to the application, and polycarbonate resin, acrylic resin, polyethylene terephthalate resin, PET resin, polyamide resin, vinyl chloride resin, olefin resin, epoxy resin, polyimide resin, fluorine resin, or the like may be used.
The transparent substrate having a layer of the hexaboride fine particle dispersion of the present invention can be obtained by bonding and integrating a plurality of opposing transparent substrates, which are present with the hexaboride fine particle dispersion of the present invention sandwiched therebetween, by a known method.
The optical properties of the sheet-like, plate-like or film-like dispersion of hexaboride fine particles or the light-absorbing sandwich structure of the present invention can achieve a minimum value of transmittance (minimum transmittance) of 35% or less in a light wavelength region having a wavelength of 850 to 1300nm, when the visible light transmittance is 70%.
Here, the visible light transmittance can be easily adjusted to 70% by adjusting the concentration of the hexaboride fine particle aggregate contained in the hexaboride fine particle dispersion liquid, the dispersion powder, the plasticizer dispersion liquid, or the master batch, the amount of the hexaboride fine particle aggregate, the dispersion powder, the plasticizer dispersion liquid, or the master batch at the time of preparing the resin composition, the film thickness of the film or the sheet, and the like.
[h] Infrared absorbing film, infrared absorbing glass, and method for producing same
An infrared absorbing film or an infrared absorbing glass can be produced by forming a coating layer containing an aggregate of hexaboride fine particles on at least one surface of a transparent substrate selected from a substrate film and a substrate glass using the above dispersion of hexaboride fine particles.
The infrared absorbing film or the infrared absorbing glass can be produced by mixing the above-mentioned dispersion of fine hexaboride particles with a plastic or a monomer to prepare a coating liquid, and forming a coating film on a transparent substrate by a known method.
For example, an infrared absorbing film can be produced as follows.
A dielectric resin is added to the above-mentioned dispersion of fine hexaboride particles to obtain a coating liquid. When the coating liquid is applied to the surface of a film substrate, and then the solvent is evaporated to cure the resin by a predetermined method, a coating film in which the particle assembly of hexaboride is dispersed in a medium can be formed.
The dielectric resin of the coating film may be selected from, for example, a UV curable resin, a thermosetting resin, an electron beam curable resin, a normal temperature curable resin, a thermoplastic resin, and the like, depending on the purpose. Specifically, there may be mentioned: polyethylene resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyvinyl alcohol resin, polystyrene resin, polypropylene resin, ethylene-vinyl acetate copolymer, polyester resin, polyethylene terephthalate resin, fluororesin, polycarbonate resin, acrylic resin, polyvinyl butyral resin.
These resins may be used alone or in combination. In particular, in the medium for coating, a UV curable resin binder is particularly preferably used from the viewpoint of productivity, device cost, and the like.
In addition, a binder using a metal alkoxide can be used. Typical examples of the metal alkoxide include alkoxides of Si, Ti, Al, Zr, and the like. The binder containing these metal alkoxides is hydrolyzed and polycondensed by heating or the like, whereby a coating layer formed of an oxide film can be formed.
In addition to the above method, the dispersion of the fine hexaboride particles may be applied to a substrate film or a substrate glass, and then a binder using a dielectric resin or a metal alkoxide may be further applied to form a coating layer.
The film base is not limited to a film shape, and may be, for example, a plate shape or a sheet shape. As the film base material, PET, acrylic, polyurethane, polycarbonate, polyethylene, ethylene vinyl acetate copolymer, vinyl chloride, fluororesin, or the like can be used according to various purposes. However, the infrared absorbing film is preferably a polyester film, and more preferably a PET film.
In addition, in order to achieve ease of coating adhesion, the surface of the film substrate is preferably subjected to surface treatment. In order to improve the adhesion between the glass substrate or the film substrate and the coating layer, it is preferable to form an intermediate layer on the glass substrate or the film substrate and form the coating layer on the intermediate layer. The intermediate layer is not particularly limited, and may be formed of, for example, a polymer film, a metal layer, an inorganic layer (for example, an inorganic oxide layer such as silica, titania, or zirconia), an organic/inorganic composite layer, or the like.
The method for providing a coating layer on the substrate film or the substrate glass is not particularly limited as long as the dispersion of the fine hexaboride particles can be uniformly applied to the surface of the substrate. Examples thereof include a bar coating method, a gravure coating method, a spray coating method, and a dip coating method.
For example, according to the bar coating method using a UV curable resin, a coating film can be formed on a substrate film or a substrate glass using a wire bar (wire bar) of a bar number that can be fitted so as to satisfy the thickness of the coating film and the content of the hexaboride fine particles, and a coating liquid having a liquid concentration and additives appropriately adjusted so as to have appropriate leveling properties. Then, the solvent contained in the coating liquid is removed by drying, and then, ultraviolet rays are irradiated to cure the solvent, whereby a coating layer can be formed on the substrate film or the substrate glass. In this case, the drying conditions of the coating film are usually about 20 seconds to 10 minutes at a temperature of 60 ℃ to 140 ℃ depending on the kind of each component, solvent and the ratio of the solvent used. The ultraviolet ray irradiation is not particularly limited, and for example, a UV exposure machine such as an ultrahigh pressure mercury lamp can be preferably used.
Further, the adhesion between the substrate and the coating layer, the smoothness of the coating film during coating, the drying property of the organic solvent, and the like can be controlled by the steps before and after the formation of the coating layer. Examples of the preceding and subsequent steps include a surface treatment step of the substrate, a pre-baking (pre-heating of the substrate) step, and a post-baking (post-heating of the substrate) step, and can be selected as appropriate. The heating temperature in the pre-baking step and/or the post-baking step is preferably 80 to 200 ℃ and the heating time is preferably 30 to 240 seconds.
The thickness of the coating layer on the substrate film or on the substrate glass is not particularly limited, but is preferably 10 μm or less, and more preferably 6 μm or less in practical use. This is because, if the thickness of the coating layer is 10 μm or less, the scratch resistance is exhibited by sufficient pencil hardness, and the occurrence of process abnormalities such as warpage of the substrate film can be avoided when the solvent in the coating layer is volatilized and the binder is cured.
Regarding the optical properties of the infrared absorbing film or the infrared absorbing glass to be produced, the minimum value of the transmittance (minimum transmittance) in the wavelength region of light having a wavelength of 850 to 1300nm is 35% or less when the visible light transmittance is 70%. Further, the visible light transmittance can be easily adjusted to 70% by adjusting the concentration of the hexaboride fine particles in the coating liquid or adjusting the film thickness of the coating layer.
For example, the six per projected area contained in the coatingThe content of boride fine particle aggregate is preferably 0.01g/m2Above and 0.5g/m2The following.
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