WO2017033533A1

WO2017033533A1 - Thermochromic film and thermochromic composite

Info

Publication number: WO2017033533A1
Application number: PCT/JP2016/067606
Authority: WO
Inventors: 鈴木　伸一; 丈範熊谷
Original assignee: コニカミノルタ株式会社
Priority date: 2015-08-21
Filing date: 2016-06-14
Publication date: 2017-03-02
Also published as: CN107922260A; JPWO2017033533A1

Abstract

The present invention addresses the problem of providing a thermochromic film and a thermochromic composite which include vanadium dioxide particles having excellent thermochromic properties and durability. This thermochromic film has, on a transparent substrate, an optically functional layer that includes at least vanadium dioxide particles with thermochromic properties and a binder resin. The thermochromic film is characterized in that: the binder resin has a reactive functional group and is water-soluble; water content of the optically functional layer after being left to stand at 80°C and a humidity of 80% for 24 hours is in the range of 0.5-5.0 g/m²; and the thickness of the optically functional layer is in the range of 0.5-5.0 μm.

Description

Thermochromic film and thermochromic composite

The present invention relates to a thermochromic film and a thermochromic composite. More specifically, the present invention relates to a thermochromic film containing vanadium dioxide particles having thermochromic properties.

In recent years, in order to reduce the heat felt by human skin due to the influence of sunlight entering from a car window, laminated glass having high heat insulating properties or heat shielding properties has been distributed in the market. Recently, with the spread of electric vehicles and the like, development of near-infrared light (heat ray) shielding films applied to laminated glass has been actively conducted from the viewpoint of increasing the cooling efficiency in the vehicle.
The near-infrared light shielding film can be applied to a vehicle body or a window glass of a building to reduce a load on a cooling facility such as an air conditioner in the vehicle, and is an effective means for energy saving.

As such a near infrared light shielding film, an optical film containing a conductor such as ITO (indium tin oxide) as an infrared absorbing substance is disclosed. Also, it has a near infrared light shielding film including a functional plastic film having an infrared reflection layer and an infrared absorption layer, and a reflection layer laminate in which a large number of low refractive index layers and high refractive index layers are alternately laminated. A near-infrared light shielding film that selectively reflects near-infrared light by adjusting the thickness of each refractive index layer has been proposed.
The near-infrared light shielding film having such a configuration is preferably used due to its high near-infrared light shielding effect in a low-latitude zone near the equator where the illuminance of sunlight is high. However, in winter in the mid-latitude to high-latitude zones, conversely, there is a problem that incident light is uniformly shielded even when it is desired to capture sunlight as much as possible in the vehicle or indoors.

In order to solve such a problem, a method of applying a thermochromic material in which the optical properties of near-infrared light shielding and transmission are controlled by temperature has been studied. A typical material is vanadium dioxide (hereinafter also referred to as “VO ₂ ”). VO ₂ is known to undergo a phase transition in a temperature range of around 60 ° C. and exhibit thermochromic properties.

A method of providing a thermochromic film as a laminate for dispersing VO ₂ particles in a transparent resin and forming a VO ₂ dispersed resin layer on a resin substrate (see, for example, Patent Document 1) or doping with molybdenum or the like. A method (for example, refer to Patent Document 2) of providing a thermochromic film by mixing the obtained VO ₂ particles with a polyester resin by a T-die method is disclosed.
However, when VO ₂ particles are synthesized after the particles are filtered and dried, or using a solvent-based coating solution prepared with a binder insoluble in an aqueous solvent, an optical functional film that exhibits thermochromic properties is formed. It was found that the primary particles of the VO ₂ particles tend to aggregate to form secondary particles. Therefore, it is conceivable to use a water-soluble binder as the binder. However, when the water-soluble binder is used, it is understood that when the VO ₂ particles are stored for a long time under high temperature and high humidity, the thermochromic performance is lowered. It was.
Patent Document 3 describes that a laminated body is obtained by dispersing a thermochromic material in a water-soluble acrylic resin. However, a thermal barrier layer must be provided, and the thermochromic property is sufficient. There wasn't. Especially in winter, the heat absorbed by the variable property layer was only transferred to the room by heat transfer, which was not sufficient.

JP 2013-184091 A JP 2004-346260 A JP 2010-247522 A

The present invention has been made in view of the above-described problems and circumstances, and its solution is to provide a thermochromic film and a thermochromic composite containing vanadium dioxide particles exhibiting excellent thermochromic properties and durability. It is.

As a result of examining the cause of the above-mentioned problems in order to solve the above problems, the present inventor has found that the thermochromic film of the present invention has a binder resin having a reactive functional group and water-soluble, and an optical functional layer. It was found that the film thickness and the water content of were within the predetermined ranges, and thus exhibited excellent thermochromic properties and durability, leading to the present invention.
That is, the said subject of this invention is solved by the following means.

1. A thermochromic film having an optical functional layer containing vanadium dioxide particles exhibiting at least thermochromic properties and a binder resin on a transparent substrate,
The binder resin has a reactive functional group and is water-soluble;
The moisture content of the optical functional layer after being left for 24 hours at 80 ° C. and 80% humidity is in the range of 0.5 to 5.0 g / m ² , and the film thickness of the optical functional layer is 0 A thermochromic film characterized by being in the range of 5 to 5.0 μm.

2. ^2. The thermochromic film according to item 1, wherein the water content is in the range of 0.6 to 2.0 g / m ² .

3. The thermochromic film according to

item

1 or 2, which contains a water-soluble cellulose resin as the binder resin.

4. 4. The thermo according to claim 1, wherein the optical functional layer further contains at least one of an isocyanate compound, a melamine compound, a carbodiimide compound, and an epoxy compound. Chromic film.

5. A thermochromic composite comprising the thermochromic film according to any one of items 1 to 4 as a constituent element.

The above-mentioned means of the present invention can provide a thermochromic film and a thermochromic composite containing vanadium dioxide particles exhibiting excellent thermochromic properties and durability.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
As described above, the VO ₂ particles form an optical functional film that exhibits thermochromic properties by using a solvent-based coating solution prepared by filtering and drying after synthesizing the particles or a binder insoluble in an aqueous solvent. In this case, the primary particles of the VO ₂ particles tend to aggregate to form secondary particles. In addition, if a water-soluble binder is used without adjusting the amount of water contained in the vanadium dioxide particles and stored at a high temperature and high humidity for a long time, the reduction of the vanadium dioxide particles is promoted, and the vanadium dioxide thermostat. It is considered that the chromic property is impaired or the durability of the film is lowered.

Specifically, if the water content of the optical functional layer in the thermochromic film is less than 0.5 g / m ² , the film becomes hard, and cracking is likely to occur due to bending, resulting in poor workability. On the other hand, when the water content of the optical functional layer in the thermochromic film is larger than 5.0 g / m ² , the thermochromic property is significantly lowered.
Therefore, by defining the amount of water contained in the optical functional layer in the thermochromic film and further introducing a reactive functional group into the resin, aggregation of vanadium dioxide particles can be suppressed, so that haze is lowered. be able to.
Thereby, it is guessed that the thermochromic film which shows the outstanding thermochromic property and durability can be provided.

Schematic sectional view of the thermochromic film of the present invention

The thermochromic film of the present invention is a thermochromic film having an optical functional layer containing at least thermochromic vanadium dioxide particles and a binder resin on a transparent substrate, wherein the binder resin is a reactive functional group. And the water content of the optical functional layer after standing for 24 hours at 80 ° C. and 80% humidity is in the range of 0.5 to 5.0 g / m ² , and The optical functional layer has a thickness in the range of 0.5 to 5.0 μm. This feature is a technical feature common to or corresponding to the claimed invention.

As an embodiment of the present invention, the water content is more preferably in the range of 0.6 to 2.0 g / m ² from the viewpoint of manifestation of the effect of the present invention.

In addition, it is more preferable to contain a water-soluble cellulose resin as the binder resin from the viewpoints of good dispersibility of vanadium dioxide particles, high thermochromic properties, low haze and flexibility.

In addition, it is preferable that the optical functional layer further contains at least one of an isocyanate compound, a melamine compound, a carbodiimide compound and an epoxy compound from the viewpoint of manifesting the effect of the present invention.

Further, the thermochromic complex of the present invention preferably includes the thermochromic film of the present invention as a constituent element from the viewpoint of manifesting the effects of the present invention.

Hereinafter, the present invention, its constituent elements, and modes and modes for carrying out the present invention will be described in detail. In the following description, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.

[Vanadium oxide]
Vanadium dioxide according to the present invention is an embodiment of vanadium oxide. Vanadium oxide takes various forms in nature, including V ₂ O ₅ , H ₃ V ₂ O ₇ ⁻ , H ₂ VO ₄ ⁻ , HVO ₄ ²⁻ , VO ₄ ³⁻ , VO ²⁺ , VO ₂ , V ³⁺ , V ^Examples of the structure include ₂ O ₃ , V ²⁺ , V ₂ O ₂ , and V. The form changes depending on each environmental atmosphere. Generally, V ₂ O ₅ is formed in an acidic environment, and V ₂ O ₃ is formed in a reducing environment. Therefore, VO ₂ is relatively easy to oxidize and reduce, and the crystal structure changes depending on the surrounding environment.
Since VO ₂ exhibiting thermochromic properties (automatic light control) exhibits a monoclinic structure, VO ₂ used in the present invention is a monoclinic crystal.

[Vanadium dioxide particles]
The crystal form of the vanadium dioxide particles used in the present invention is preferably rutile VO ₂ particles (hereinafter also simply referred to as “VO ₂ particles”) from the viewpoint of efficiently expressing thermochromic properties.
Since the rutile VO ₂ particles have a monoclinic structure below the transition temperature, they are also called M-type. The vanadium dioxide particles according to the present invention may contain VO ₂ particles of other crystal types such as A-type or B-type within a range that does not impair the purpose.
The VO ₂ particles according to the present invention are preferably present in a state where the number average particle diameter of primary particles and secondary particles is less than 500 nm in the optical functional layer.
Various measurement methods can be applied to the particle diameter measurement method, but it is preferable to measure according to the dynamic light scattering method.

The preferred number average particle diameter of the primary particles and secondary particles in the VO ₂ particles according to the present invention is in the range of 1 to 200 nm, more preferably in the range of 5 to 100 nm, and most preferably in the range of 5 to 60 nm. Is within the range.
The aspect ratio of the VO ₂ particles is preferably in the range of 1.0 to 3.0.
The VO ₂ particles having such characteristics have a sufficiently small aspect ratio and isotropic shape, and therefore have good dispersibility when added to a solution. In addition, since the particle diameter of the single crystal is sufficiently small, better thermochromic properties can be exhibited compared to conventional particles.

As long as the objective effect of the present invention is achieved, a substance containing an element for adjusting the phase transition temperature of the vanadium dioxide particles may be further included. The substance for adjusting the phase transition temperature is not particularly limited, but tungsten, titanium, molybdenum, niobium, tantalum, tin, rhenium, iridium, osmium, ruthenium, germanium, chromium, iron, gallium, aluminum, fluorine, phosphorus, etc. are used. it can. By containing the said substance, the phase transition temperature of a vanadium dioxide particle can be lowered | hung. The amount of the above substance added is not particularly limited, but is an amount that is preferably within a range of 0.03 to 1 element, more preferably 0.04 to 0.08 element with respect to 100 elements of vanadium.

(1: Method for producing aqueous dispersion of vanadium dioxide particles)
In general, synthesis of vanadium dioxide particles, a method of pulverizing the VO ₂ sintered body synthesized by the solid phase method, vanadium pentoxide (V 2 _O ₅₎ as a raw material, while combining the VO ₂ in the liquid phase An aqueous synthesis method in which particles are grown can be mentioned.
In the present invention, VO ₂ produced by any method can be applied. A dispersant is added to VO ₂ produced by any method to prepare an aqueous dispersion.
The amount of the dispersant added can be reduced by using water as the solvent, compared with the case of using an organic solvent, and is preferably in the range of 0.1 to 1.0% by mass.
In addition to low molecular weight dispersants such as alkyl sulfonates, alkyl benzene sulfonates, diethylamine, ethylenediamine, and quaternary ammonium salts, dispersants include polyoxyethylene nonylphenyl ether, polyethylene ethylene laurate, hydroxy Examples thereof include ethyl cellulose, polyvinyl pyrrolidone, polyethylene glycol, and hydroxyl ethyl cellulose, and polyvinyl pyrrolidone or cellulose resin is particularly preferable.
Then, without drying the VO ₂ particles of the aqueous dispersion, it is possible to prepare optically functional layer forming coating solution as described below.

By using the coating solution for forming an optical functional layer in this state, an optical functional layer is formed, thereby containing VO ₂ particles having a preferred number average particle size of primary particles and secondary particles having a number average particle size of less than 150 nm. An optical functional layer can be formed.
Further, as a method for producing VO ₂ particles, if necessary, particles such as fine TiO ₂ that becomes the core of particle growth are added as nucleus particles, and the VO ₂ particles are produced by growing the nucleus particles. You can also.

In addition, when using water-soluble binder resin as binder resin, after preparing as the aqueous dispersion containing the above-mentioned VO ₂ particles, the VO ₂ particles are separated without drying the VO ₂ particles in the aqueous dispersion. It is preferable to prepare a coating solution for forming an optical functional layer by mixing with a water-soluble binder resin solution in a dispersed state.
Next, the details of the method for producing VO ₂ particles by the hydrothermal method suitable for the present invention will be described.
Hereinafter, a manufacturing process of the VO ₂ particles by typical hydrothermal method.

(Process 1)
A substance (I) containing vanadium (V), hydrazine (N ₂ H ₄ ) or a hydrate thereof (N ₂ H ₄ .nH ₂ O), and water are mixed to prepare a solution (A). The solution (A) may be an aqueous solution in which the substance (I) is dissolved in water, or may be a suspension in which the substance (I) is dispersed in water.
Examples of the substance (I) include vanadium pentoxide (V ₂ O ₅ ), ammonium vanadate (NH ₄ VO ₃ ), vanadium trichloride oxide (VOCl ₃ ), sodium metavanadate (NaVO ₃ ), and the like. The substance (I) is not particularly limited as long as it is a compound containing pentavalent vanadium (V). Hydrazine (N ₂ H ₄ ) and its hydrate (N ₂ H ₄ .nH ₂ O) function as a reducing agent for the substance (I) and have a property of being easily dissolved in water.

The solution (A) may further contain a substance (II) containing the element to be added in order to add the element to the finally obtained vanadium dioxide (VO ₂ ) single crystal particles. Examples of the element to be added include tungsten (W), molybdenum (Mo), niobium (Nb), tantalum (Ta), tin (Sn), rhenium (Re), iridium (Ir), osmium (Os), ruthenium ( Ru), germanium (Ge), chromium (Cr), iron (Fe), gallium (Ga), aluminum (Al), fluorine (F), or phosphorus (P).

By adding these elements to the finally obtained vanadium dioxide (VO ₂ ) single crystal particles, the thermochromic properties of the vanadium dioxide particles, in particular, the transition temperature can be controlled.
Moreover, this solution (A) may further contain a substance (III) having oxidizing property or reducing property. Examples of the substance (III) include hydrogen peroxide (H ₂ O ₂ ). By adding the oxidizing or reducing substance (III), the pH of the solution can be adjusted, or the substance containing vanadium (V) as the substance (I) can be uniformly dissolved.

(Process 2)
Next, a hydrothermal reaction treatment is performed using the prepared solution (A). Here, “hydrothermal reaction” means a chemical reaction that occurs in hot water (subcritical water) whose temperature and pressure are lower than the critical point of water (374 ° C., 22 MPa). The hydrothermal reaction treatment is performed, for example, in an autoclave apparatus. By the hydrothermal reaction treatment, single crystal particles containing vanadium dioxide (VO ₂ ) are obtained.

The conditions of the hydrothermal reaction treatment (for example, the amount of reactants, the treatment temperature, the treatment pressure, the treatment time, etc.) are set as appropriate, but the temperature of the hydrothermal reaction treatment is, for example, within the range of 250 to 350 ° C. Preferably, it is in the range of 250 to 300 ° C, more preferably in the range of 250 to 280 ° C. By reducing the temperature, the particle diameter of the obtained single crystal particles can be reduced, but if the particle diameter is excessively small, the crystallinity is lowered. The hydrothermal reaction treatment time is preferably in the range of 1 hour to 5 days, for example. By increasing the time, the particle diameter and the like of the obtained single crystal particles can be controlled. However, if the processing time is excessively long, the energy consumption increases.

(Process 3)
If necessary, the surface of the obtained vanadium dioxide particles may be subjected to a coating treatment or a surface modification treatment with a resin. Thereby, the surface of the vanadium dioxide particles is protected, and surface-modified single crystal fine particles can be obtained. In the present invention, among these, it is preferable that the surface of the vanadium dioxide particles is coated with the binder resin according to the present invention having a glass transition temperature of 65 ° C. or lower.
The “coating” referred to in the present invention may be a state where the entire surface of the particle is completely covered with the resin with respect to the vanadium dioxide particles, or a part of the particle surface is covered with the resin. It may be in a state. Preferably, a state where 50% or more of the total area of the particle surface is covered is good, and a state where 80% or more is covered is more preferable.
Through the steps 1 to 3, a dispersion liquid containing VO ₂ -containing single crystal particles having thermochromic properties is obtained.

[VO ₂ grinding method]
There are various methods for making VO ₂ into fine particles, but there are various methods such as bead milling, ultrasonic crushing, and high-pressure homogenizer, and any method can be used to produce VO ₂ particles.
Various beads can be used in the bead mill, but zirconia beads are preferably used from the viewpoint of hardness and price.

<Removal treatment of impurities in aqueous dispersion of vanadium dioxide particles>
The dispersion of vanadium dioxide particles prepared by the above-described aqueous synthesis method contains impurities such as residues generated during the synthesis process, which triggers the generation of secondary aggregated particles when forming the optical functional layer. The optical functional layer may be a cause of deterioration during long-term storage, and it is preferable to remove impurities at the stage of the dispersion.
As a method for removing impurities in the aqueous dispersion of vanadium dioxide particles, conventionally known means for separating foreign substances and impurities can be applied. For example, the VO ₂ particle aqueous dispersion is subjected to centrifugal separation to obtain vanadium dioxide particles. It is possible to remove the impurities in the supernatant, add and disperse the dispersion medium again, or remove the impurities out of the system using an exchange membrane such as an ultrafiltration membrane. From the viewpoint of preventing aggregation of particles, a method using an ultrafiltration membrane is most preferable.
Examples of the material for the ultrafiltration membrane include cellulose, polyethersulfone, and polytetrafluoroethylene (abbreviation: PTFE). Among these, polyethersulfone and PTFE are preferably used.

<Summary of thermochromic film layer structure>
The typical structural example of the thermochromic film of this invention is demonstrated using a figure.
One of the preferable aspects of the thermochromic film of this invention is the structure by which the optical function layer is formed on the transparent base material.
FIG. 1 is a schematic cross-sectional view showing an example of a basic configuration of a thermochromic film having an optical functional layer containing vanadium dioxide particles and a binder resin defined in the present invention.

A thermochromic film 1 shown in FIG. 1 has a configuration in which an optical functional layer 3 is laminated on a transparent substrate 2. This optical functional layer 3 is present in a state where vanadium dioxide particles are dispersed in the binder resin B1 contained in the optical functional layer. This is vanadium dioxide particles, constitute the primary particles VO _S of vanadium dioxide vanadium dioxide particles are present independently, an aggregate of two or more vanadium dioxide particles (also referred to as aggregates.), secondary particles VO _M of VO ₂ is present. In the present invention, an aggregate of two or more vanadium dioxide particles is collectively referred to as secondary particles, and is also referred to as secondary particle aggregates or secondary aggregate particles.

(Water content and film thickness of optical function layer)
The thermochromic film of the present invention has a water content of 0.5 to 5.0 g as measured by the Karl Fischer method (JIS K 0068-2001) after standing at 80 ° C. and 80% humidity for 24 hours. / M ² and the thickness of the optical functional layer is in the range of 0.5 to 5.0 μm.
The film thickness is preferably in the range of 1.0 to 3.0 μm. The water content is preferably in the range of 0.6 to 2.0 g / m ² , more preferably in the range of 0.7 to 1.0 g / m ² . In the thermochromic film of the present invention, the water content can be adjusted by the film thickness of the optical functional layer and the binder resin or hardener contained in the optical functional layer.
The moisture content can be measured by the Karl Fischer method (JIS K 0068-2001), for example, using a Karl Fischer moisture measuring device CA-31 manufactured by Mitsubishi Chemical.

When the film thickness of the optical functional layer of the present invention is thinner than 0.5 μm, sufficient moisture cannot be contained and the optical function layer is easily broken. On the other hand, if it is thicker than 5.0 μm, flexibility is impaired.
In addition, a thermochromic film having a film thickness within the above range of the optical functional layer easily breaks when the moisture content is less than 0.5 g / m ² , and when the moisture content exceeds 5.0 g / m ² , the reduction of vanadium dioxide proceeds. Too much.
Therefore, the optical functional layer of the thermochromic film of the present invention has a film thickness and moisture content within the range, so that the film can be made flexible and the reduction of the vanadium dioxide contained can be advanced to the optimum range. Therefore, it is possible to achieve both excellent thermochromic properties and durability.

(Number average particle size)
The number average particle diameter measured by the total particles of the primary particles VO _S and secondary particles VO _M of VO ₂ particles in the optical functional layer 3, is preferably 200nm or less, and more preferably less than 150 nm.
The number average particle diameter of the VO ₂ particles in the optical functional layer can be determined according to the following method.
First, the side surface of the optical functional layer containing vanadium dioxide particles is trimmed using a microtome or the like to expose the cross section of the optical functional layer as shown in FIG.
Next, the exposed cross section is photographed at a magnification of 10,000 to 100,000 times using a transmission electron microscope (TEM). The particle diameter is measured for all vanadium dioxide particles present in a certain area of the photographed cross section. At this time, the vanadium dioxide particles to be measured are preferably in the range of 50 to 300 particles. In the photographed vanadium dioxide particle group, primary particles and secondary particles are mixed as shown in FIG. 1, and the particle diameter of the primary particles of vanadium dioxide is the diameter of each independent particle. If it is not spherical, the projected area of the particle is converted into a circle, and the diameter is taken as the particle diameter.

On the other hand, for the secondary particles of vanadium dioxide in which two or more particles are aggregated, after obtaining the projected area of the whole aggregate, the projected area is converted into a circle, and the diameter is used as the The aggregated secondary particles are defined as one particle. The number average diameter is obtained for each diameter of the primary particles and secondary particles obtained as described above. Since the cut-out cross-sectional portion has a variation in particle distribution, the measurement of the number-average diameter is carried out for 10 cross-sectional areas of different scenes, the total number-average diameter is obtained, and the number-average particle referred to in the present invention The diameter.

The thermochromic film of the present invention may have a near-infrared light shielding layer having a function of shielding at least part of light within a wavelength range of 700 to 1000 nm, in addition to the optical functional layer.
As the optical characteristics of the thermochromic film of the present invention, the visible light transmittance measured by JIS R 3106-1998 is preferably 60% or more, more preferably 70% or more, and further preferably 80% or more. It is. In addition, it is preferable to have a region with a reflectance exceeding 50% in a wavelength region of 900 to 1400 nm.

<Each component of thermochromic film>
Hereinafter, the details of the optical functional layer, which is a constituent element of the thermochromic film of the present invention, a resin base material provided if necessary, and the near infrared light shielding layer will be described.

[Optical function layer]
The optical functional layer used in the present invention contains at least vanadium dioxide particles exhibiting thermochromic properties and a resin binder.
The vanadium dioxide particles exhibiting thermochromic properties are as described above, and the resin binder has a reactive functional group and is water-soluble. Hereinafter, the resin binder according to the present invention is also referred to as “water-soluble binder resin having a reactive functional group”.

(Water-soluble binder resin having a reactive functional group)
The binder resin used in the optical functional layer according to the present invention has a reactive functional group and is water-soluble (water-soluble binder resin having a reactive functional group).
The water solubility of the binder resin here means the temperature at which the water-soluble resin is most dissolved, and when it is dissolved in water at a concentration of 0.5% by mass, it is filtered through a G2 glass filter (maximum pores 40 to 50 μm). In this case, the mass of the insoluble matter separated by filtration is within 50% by mass of the added water-soluble resin.
Examples of the reactive functional group include a hydroxy group, a methoxy group, a hydroxypropoxy group, an acetoacetyl group, a carbonyl group, and a carboxy group.

Examples of the water-soluble resin having a reactive functional group applicable to the present invention include polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymer, potassium acrylate-acrylonitrile copolymer. Acrylic resins such as vinyl acetate-acrylic acid ester copolymer or acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, styrene-methacrylic acid-acrylic acid Styrene acrylic resin such as ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene-sodium styrenesulfonate copolymer Coalescence, styrene-2-hydroxyl Tyl acrylate copolymer, styrene-2-hydroxyethyl acrylate-potassium styrene sulfonate copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer, vinyl naphthalene -Vinyl acetate copolymers such as maleic acid copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, and their salts and cellulose resins Is mentioned. Among these, a cellulose resin is a particularly preferable example.

(Water-soluble cellulose resin)
The water-soluble cellulose resin that can be used for forming the optical functional layer according to the present invention is a water-soluble cellulose derivative, for example, carboxymethyl cellulose (cellulose carboxymethyl ether), methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, Examples thereof include water-soluble cellulose derivatives such as hydroxypropylmethylcellulose, carboxymethyl cellulose (cellulose carboxymethyl ether) and carboxyethyl cellulose which are carboxylic acid group-containing cellulose resins. Other examples include cellulose derivatives such as nitrocellulose, cellulose acetate propionate, cellulose acetate, and cellulose sulfate.

In the present invention, it is one preferred embodiment that the water-soluble binder resin having a reactive functional group is a resin containing 50 mol% or more of repeating units having a hydroxy group. In the case of a cellulosic resin, the repeating unit component originally has three hydroxy groups, and a part of the three hydroxy groups is substituted. “Containing 50 mol% or more of a repeating unit component having a hydroxy group” means that 50 mol% or more of the repeating unit component having a hydroxy group in this substituent or a repeating unit component in which one or more unsubstituted hydroxy groups remain is contained. Represents.

[Hardener]
The hardener used in the present invention is not particularly limited as long as it causes a curing reaction with the binder resin.
For example, boric acid, an isocyanate compound, a melamine compound, a carbodiimide compound, an epoxy compound, or the like can be used. Examples of the isocyanate compound include compounds having an isocyanate group such as tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), diphenylmethane diisocyanate (MDI).
Commercially available products include Duranate (HDI) manufactured by Asahi Kasei Chemicals Corporation, Takenate manufactured by Mitsui Chemicals (XDI, IPDI, HDI), Cosmonate (TDI), Millionate (MDI) manufactured by Tosoh Corporation. Examples of the melamine compound include MX-706 manufactured by Sanwa Chemical Co., Ltd., becamine manufactured by DIC Co., Ltd., Watersol, and Nicaridine manufactured by Nippon Carbide Industries Co., Ltd. As carbodiimide compounds, there are carbodilites manufactured by Nisshinbo Chemical Co., Ltd., and epoxy compounds such as Denasel manufactured by Nagase ChemteX Co., Ltd. and Epolite manufactured by Kyoeisha Chemical Co., Ltd. The additive concentration ranges from 1 to 50% by mass with respect to the resin. The inside is preferable.
Two or more kinds of the above hardeners may be used in combination.

[Other additives for optical functional layers]
Various additives that can be applied to the optical functional layer used in the present invention as long as the effects of the present invention are not impaired are listed below. For example, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, JP-A-57- No. 878989, JP-A-60-72785, JP-A-61-146591, JP-A-1-95091, JP-A-3-13376, etc. Various surfactants such as cation or nonion, JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-242871, and JP-A-4-242 209266, etc., optical brighteners, sulfuric acid, phosphoric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate and other pH adjusters, antifoaming agents Lubricants such as diethylene glycol, antiseptics, antifungal agents, antistatic agents, matting agents, heat stabilizers, antioxidants, flame retardants, crystal nucleating agents, inorganic particles, organic particles, viscosity reducing agents, lubricants, infrared absorbers And various known additives such as dyes and pigments.

[Method for forming optical functional layer]
The wet coating method used for forming the optical functional layer is not particularly limited, and for example, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a slide curtain coating method, or US Pat. No. 2,761,419. Examples thereof include a slide hopper coating method and an extrusion coating method described in the specification, US Pat. No. 2,761791.

<Transparent substrate>
The transparent substrate applicable to the present invention is not particularly limited as long as it is transparent, and examples thereof include glass, quartz, and a transparent resin film. However, it is possible to provide flexibility and suitability for production (manufacturing process suitability). From the viewpoint, a transparent resin film is preferable. “Transparent” in the present invention means that the average light transmittance in the visible light region is 50% or more, preferably 60% or more, more preferably 70% or more, and particularly preferably 80% or more.
The thickness of the transparent substrate is preferably in the range of 30 to 200 μm, more preferably in the range of 30 to 100 μm, and still more preferably in the range of 35 to 70 μm. If the thickness of the transparent substrate is 30 μm or more, wrinkles and the like are less likely to occur during handling, and if the thickness is 200 μm or less, for example, when producing a laminated glass, Followability to the curved glass surface is improved.

The transparent substrate is preferably a biaxially oriented polyester film, but an unstretched or at least one stretched polyester film can also be used. A stretched film is preferable from the viewpoint of strength improvement and thermal expansion suppression. In particular, when the laminated glass provided with the thermochromic film of the present invention is used as an automobile windshield, a stretched film is more preferable.
From the viewpoint of preventing generation of wrinkles in the thermochromic film and cracking of the infrared reflective layer, the transparent substrate preferably has a thermal shrinkage rate in the range of 0.1 to 3.0% at a temperature of 150 ° C., The content is more preferably in the range of 1.5 to 3.0%, and further preferably in the range of 1.9 to 2.7%.

The transparent substrate applicable to the thermochromic film of the present invention is not particularly limited as long as it is transparent, but various resin films are preferably used. For example, polyolefin films (for example, polyethylene, polypropylene, etc.) ), Polyester films (for example, polyethylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, triacetyl cellulose films, and the like, preferably polyester films and triacetyl cellulose films.

The polyester film (hereinafter simply referred to as “polyester”) is not particularly limited, but is preferably a polyester having a film-forming property having a dicarboxylic acid component and a diol component as main components. The main constituent dicarboxylic acid components include terephthalic acid, isophthalic acid, phthalic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenylsulfone dicarboxylic acid, diphenyl ether dicarboxylic acid, diphenylethanedicarboxylic acid, Examples thereof include cyclohexane dicarboxylic acid, diphenyl dicarboxylic acid, diphenyl thioether dicarboxylic acid, diphenyl ketone dicarboxylic acid, and phenylindane dicarboxylic acid. Examples of the diol component include ethylene glycol, propylene glycol, tetramethylene glycol, cyclohexanedimethanol, 2,2-bis (4-hydroxyphenyl) propane, 2,2-bis (4-hydroxyethoxyphenyl) propane, bis ( 4-Hydroxyphenyl) sulfone, bisphenol fluorene hydroxyethyl ether, diethylene glycol, neopentyl glycol, hydroquinone, cyclohexanediol and the like. Among the polyesters having these as main components, from the viewpoints of transparency, mechanical strength, dimensional stability, etc., dicarboxylic acid components such as terephthalic acid, 2,6-naphthalenedicarboxylic acid, diol components such as ethylene glycol and 1 Polyester having 1,4-cyclohexanedimethanol as the main constituent is preferred. Among these, polyesters mainly composed of polyethylene terephthalate and polyethylene naphthalate, copolymerized polyesters composed of terephthalic acid, 2,6-naphthalenedicarboxylic acid and ethylene glycol, and mixtures of two or more of these polyesters are mainly used. Polyester as a constituent component is preferable.

When using a transparent resin film as a transparent substrate, in order to facilitate handling, particles may be included within a range that does not impair transparency. Examples of particles used in the present invention include inorganic particles such as calcium carbonate, calcium phosphate, silica, kaolin, talc, titanium dioxide, alumina, barium sulfate, calcium fluoride, lithium fluoride, zeolite, molybdenum sulfide, and crosslinked polymers. Examples thereof include organic particles such as particles and calcium oxalate. Examples of the method of adding particles include a method of adding particles in a polyester as a raw material, a method of adding directly to an extruder, and the like. Well, you may use two methods together. In the present invention, additives may be added in addition to the above particles as necessary. Examples of such additives include stabilizers, lubricants, cross-linking agents, anti-blocking agents, antioxidants, dyes, pigments, and ultraviolet absorbers.

In addition, the transparent resin film may be subjected to relaxation treatment or off-line heat treatment in terms of dimensional stability. The relaxation treatment is preferably carried out in the process from the heat setting in the stretching process of the polyester film to the winding in the transversely stretched tenter or after exiting the tenter. The relaxation treatment is preferably performed at a treatment temperature in the range of 80 to 200 ° C., more preferably the treatment temperature is in the range of 100 to 180 ° C. Further, the relaxation rate is preferably within a range of 0.1 to 10% in both the longitudinal direction and the width direction, and more preferably, the relaxation rate is within a range of 2 to 6%. The relaxed substrate is subjected to off-line heat treatment to improve heat resistance and to improve dimensional stability.
The transparent resin film is preferably coated with the undercoat layer coating solution in-line on one or both sides during the film formation process. In the present invention, undercoating during the film forming process is referred to as in-line undercoating.

《Near-infrared light shielding layer》
In the thermochromic film of the present invention, in addition to the optical functional layer, a near infrared light shielding layer having a function of shielding at least part of the light wavelength range within the range of 700 to 1000 nm may be provided. .
For details of the near-infrared light shielding layer applicable to the present invention, for example, JP 2012-131130 A, JP 2012-139948 A, JP 2012-185342 A, JP 2013-080178 A. Reference can be made to constituent elements and formation methods described in JP-A-2014-089347.

《Uses of thermochromic film》
As a use of the thermochromic film of this invention, it can be used as a thermochromic composite body provided with the thermochromic film as a component. For example, a laminated glass can be constituted by being sandwiched between a pair of glass constituent members, and this laminated glass can be used for automobiles, railway vehicles, aircraft, ships, buildings, and the like. Laminated glass can be used for other purposes. The laminated glass is preferably laminated glass for buildings or vehicles. The laminated glass can be used for an automobile windshield, side glass, rear glass, roof glass, or the like.

Examples of the glass member include inorganic glass and organic glass (resin glazing). Examples of the inorganic glass include float plate glass, heat ray absorbing plate glass, polished plate glass, mold plate glass, netted plate glass, lined plate glass, and colored glass such as green glass. The organic glass is a synthetic resin glass substituted for inorganic glass. Examples of the organic glass (resin glazing) include a polycarbonate plate and a poly (meth) acrylic resin plate. Examples of the poly (meth) acrylic resin plate include a polymethyl (meth) acrylate plate. In the present invention, inorganic glass is preferred from the viewpoint of safety when it is damaged by an external impact.
The present invention can also be applied to other than glass, and can be a composite composed of a thermochromic film support including glass and a thermochromic.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "mass part" or "mass%" is represented. In the table, “film” represents a thermochromic film, and “composite” represents a thermochromic complex. “Film thickness” represents the film thickness of the optical functional layer, and “water content” represents the water content of the optical functional layer. However, for the film 136, the total thickness of the heat shielding layer and the variable property layer was defined as the thickness of the optical functional layer.

《Preparation of thermochromic film》
[Production of Film 101]
9 g of an aqueous dispersion of vanadium dioxide particles (15% by mass) having a primary particle diameter of 55 nm and 91 g of 5% by mass of polyvinyl alcohol (PVA-124; polymerization degree: 2400, saponification degree: 98 to 99 mol%, manufactured by Kuraray Co., Ltd.) And the coating liquid which mixed 9.1 g of boric acid (5 mass%) as a hardening agent was produced.
Next, the coating solution was applied onto a PET film having a thickness of 50 μm so that the film thickness of the optical functional layer was 1.5 μm, and dried with hot air at 110 ° C. for 2 minutes to produce a film 101.

[Production of Films 102 to 133]
The films 102 to 133 were produced in the same manner as the film 101 except that the materials were changed according to Table 1.
In Table 1, MC represents 5 mass% methylcellulose, and Shin-Etsu Chemical Co., Ltd. product was used. HEC represents 5 mass% hydroxyethyl cellulose, and Shin-Etsu Chemical Co., Ltd. product was used. HPMC represents 5% by mass hydroxypropyl methylcellulose, and one manufactured by Shin-Etsu Chemical Co., Ltd. was used. PL represents a polyester resin, and “EASTER” Copolyester 6763 manufactured by Eastman Chemical Co. was used. FP represents a 65% by mass TFE-based curable functional group-containing fluororesin solution, and Zaffle GK570 manufactured by Daikin Industries, Ltd. was used.
The types of hardeners are: A: boric acid (manufactured by Kanto Chemical Co., Inc.), B: hexamethylene diisocyanate (manufactured by Asahi Kasei Chemicals Corporation, Duranate (registered trademark) WT30-100), C: polyisocyanate (DIC) Beccamin (registered trademark) M-3), E: aqueous melamine resin (Watersol (registered trademark) S-695 manufactured by DIC Corporation), F: carbodiimide (Carbodilite (registered trademark) manufactured by Nisshinbo Chemical Co., Ltd.) SW-126), G: Epoxy (Nagase ChemteX Corporation Denacol (registered trademark) EX-810), H: Polyisocyanate (Sumika Bayer Urethane Co., Ltd. Sumidur (registered trademark) N3300) did.

[Preparation of film 134]
13.7 g of vanadyl triisopropoxide and 0.73 g of molybdenum pentaethoxide were dissolved in 500 mL of isopropanol. To this solution, 15 mL of ion exchange water was added and stirred at room temperature for 72 hours, and then the solvent was removed. After crushing the residue, it was calcined at 400 ° C. for 2 hours, and then calcined in a hydrogen stream at 450 ° C. for 2 hours to obtain molybdenum-doped vanadium dioxide.

After mixing 3 parts of the molybdenum-doped vanadium dioxide and 97 parts of a polyester resin “EASTER” Copolyester 6763 (manufactured by Eastman Chemical Co.), a film (optical functional layer) 134 having a thickness of 50 μm was obtained by a T-die method. .

[Production of film 135]
A film (optical functional layer) 135 was obtained in the same manner as the film 134 except that the molybdenum-doped vanadium dioxide was changed to 23 parts, and the polyester resin “EASTER” Copolyester 6763 (manufactured by Eastman Chemical) was changed to 77 parts.

[Production of Film 136]
(Preparation of a coating composition for forming a thermal barrier layer)
Zeffle GK570 (TFE curable functional group-containing fluororesin solution manufactured by Daikin Industries, Ltd., solid content concentration: 65% by mass), 49 parts by mass, titanium oxide (D918, Sakai Chemical Industry Co., Ltd.), 32 parts by mass, and acetic acid After mixing 20 parts by mass of butyl, glass beads were added and dispersed in a sand mill. The obtained dispersion was mixed with 6.5 parts by mass of a curing agent (Sumidule N3300 manufactured by Sumika Bayer Urethane Co., Ltd.) to prepare a coating composition for forming a thermal barrier layer.

(Preparation of coating composition for forming variable property layer)
12 parts by mass of thermochromic pigment (Black TCA1015 manufactured by Sands Co., Ltd.) was mixed with 88 parts by mass of Zeffle GK570, and the resulting dispersion was mixed with a homodisper with a curing agent (Sumidule manufactured by Sumika Bayer Urethane Co., Ltd.). N3300) was mixed at 12.4 parts by mass to prepare a coating composition for forming a variable property layer.

(Production of laminate)
A coating composition for forming a thermal barrier layer was applied by bar coating on a PET film having a thickness of 100 μm, and cured and dried at 23 ° C. for 24 hours to form a thermal barrier layer having a thickness of 60 μm. The variable property layer forming coating composition was applied by bar coating on the heat shielding layer and dried to form a variable property layer having a thickness of 50 μm. This laminate was cured at 23 ° C. for 24 hours to prepare a test laminate.
Table 1 shows the structures of the thermochromic films 101 to 136 produced as described above. The measuring method of water content is as follows.

<Measurement of moisture content>
After being allowed to stand at 80 ° C. and 80% humidity for 24 hours, the measurement was performed using a Karl Fischer moisture measuring device CA-31 manufactured by Mitsubishi Chemical Corporation based on the Karl Fischer method (JIS K 0068-2001). Specifically, the moisture content of the optical functional layer was determined by subtracting the moisture content of the PET film used as the substrate from the moisture content of the entire thermochromic film obtained.

《Flexibility evaluation》
About the thermochromic films 101 to 136, using a bending tester type 1 (manufactured by Imoto Seisakusho, model IMC-AOF2, mandrel diameter φ20 mm) based on a bending test method based on JIS K5600-5-1: 1999. Bending tests were performed.
The surface of the thermochromic film after the bending test was visually observed, and the flexibility was evaluated according to the following criteria.

◎: No folding marks or cracks are observed on the surface of the thermochromic film ○: Some bending marks are observed on the surface of the thermochromic film △: Slight cracks are observed on the surface of the thermochromic film ×: Thermochromic film There are many obvious cracks on the surface.

《Preparation of thermochromic complex》
Each of the produced thermochromic films 101 to 136 is made into a transparent adhesive sheet (manufactured by Nitto Denko Corporation) with a size of 15 cm × 20 cm of a glass plate having a thickness of 1.3 mm (manufactured by Matsunami Glass Kogyo Co., Ltd., “sliding glass white edge polishing”). Each of the thermochromic composites 201 to 236 produced by bonding LUCIACS CS9621T) was evaluated.

[Thermochromic evaluation]
Using the produced thermochromic composites 201 to 236, the following heat resistance in the summer and winter conditions was evaluated, and the thermochromic properties of the thermochromic film were determined.

(Summer evaluation)
<Measurement environment>
The thermochromic complex was placed on the wall of the environmental test chamber at room temperature of 28 ° C. Specifically, an environmental test room was used assuming that the indoor side of the environmental test room is a thermochromic film and the side adjacent to the wall surface is glass, assuming a Japanese cool biz room.
A 150 W halogen lamp that assumed the summer sun was lit from a position 50 cm away from the wall surface of the part where the thermochromic complex was placed in the environmental test room.
Further, assuming that the thermochromic complex is heated by the accumulation of sunlight irradiation, the thermochromic complex was heated to 70 ° C. with a thermocouple.

<Evaluation 1>
A thermometer was installed at a position 1 m away from the thermochromic complex in the environmental test chamber, the temperature after 1 hour was measured under the above conditions, and the evaluation performed according to the following criteria was evaluated as “before wet heat resistance”. .
In addition, after being left in an environment of 85 ° C. and humidity of 85% for 100 hours, a thermometer was installed at a position 1 m away from the thermochromic complex in the environmental test chamber, as in the evaluation before the wet heat resistance. The temperature after 1 hour was measured, and the evaluation performed according to the following criteria was evaluated as “after wet heat resistance”.

◎: Temperature after 1 hour is less than 29 ° C, almost no temperature rise due to external light ○: Temperature after 29 hours is 29 ℃ or more and less than 32 ℃ ○ △: After 1 hour The temperature is 32 ° C. or more and less than 34 ° C. Δ: The temperature after the passage of 1 hour is 34 ° C. or more and less than 36 ° C. ×: The temperature after the passage of 1 hour is 36 ° C. or more, which is a harsh environment.

(Estimated winter evaluation)
<Measurement environment>
A thermochromic composite was placed on the wall of an environmental test room having a room temperature of 20 ° C. Specifically, an environmental test chamber was used assuming that the indoor side of the environmental test room is a thermochromic film and the side adjacent to the wall surface is glass, assuming a Japanese warm biz room.
From a position 50 cm away from the wall surface of the part where the thermochromic complex was placed in the environmental test room, a 100 W halogen lamp was used that assumed the winter sun.

<Evaluation 2>
A thermometer was installed at a position 1 m away from the thermochromic complex in the environmental test chamber, the temperature after 1 hour was measured under the above conditions, and the evaluation performed according to the following criteria was evaluated as “before wet heat resistance”. .
In addition, after being left in an environment of 85 ° C. and humidity of 85% for 100 hours, a thermometer was installed at a position 1 m away from the thermochromic complex in the environmental test chamber, as in the evaluation before the wet heat resistance. The temperature after 1 hour was measured, and the evaluation performed according to the following criteria was evaluated as “after wet heat resistance”.

◎: Temperature after 1 hour is 26 ° C or higher, and heat energy from external light has entered moderately. ○: Temperature after 24 hours is more than 24 ° C and less than 26 ° C. Later temperature is 22 ° C. or more and less than 24 ° C. Δ: Temperature after 21 hours is 21 ° C. or more and less than 22 ° C. ×: Many near infrared light is unconditionally shielded and after 1 hour The temperature is less than 21 ° C

<Evaluation of haze>
About each produced said thermochromic composite body, after leaving for 100 hours in an environment of 85 degreeC and 85% of humidity, using a haze meter (Nippon Denshoku Industries Co., Ltd. NDH2000), a haze (%) is measured, The haze was evaluated according to the following criteria.

◎: Haze is less than 2.0% ○: Haze is 2.0% or more and less than 3.0% ○ △: Haze is 3.0% or more and less than 5.0% △: Haze 5.0% or more and less than 8.0% x: Haze is 8.0% or more

<Evaluation results>
As can be seen from the results in Table 2, it was found that the flexibility, wet heat resistance, and haze when using the thermochromic film of the present invention were superior to those when using the thermochromic film of the comparative example.

According to the present invention, a thermochromic film and a thermochromic composite containing vanadium dioxide particles exhibiting excellent thermochromic properties and durability can be obtained, and these can be suitably used for near infrared light shielding films and the like.

1 thermochromic film 2 transparent substrate 3 optical function layer B1 binder resin VO _S primary particles of vanadium dioxide VO _M vanadium dioxide secondary particles

Claims

A thermochromic film having an optical functional layer containing vanadium dioxide particles exhibiting at least thermochromic properties and a binder resin on a transparent substrate,
The binder resin has a reactive functional group and is water-soluble;
The moisture content of the optical functional layer after being left for 24 hours at 80 ° C. and 80% humidity is in the range of 0.5 to 5.0 g / m 2 , and the film thickness of the optical functional layer is 0 A thermochromic film characterized by being in the range of 5 to 5.0 μm.
The thermochromic film according to claim 1, wherein the water content is in the range of 0.6 to 2.0 g / m 2 .
The thermochromic film according to claim 1 or 2, wherein the binder resin contains a water-soluble cellulose resin.
4. The thermo according to claim 1, wherein the optical functional layer further contains at least one of an isocyanate compound, a melamine compound, a carbodiimide compound, and an epoxy compound. 5. Chromic film.
A thermochromic composite comprising the thermochromic film according to any one of claims 1 to 4 as a constituent element.