JP6954807B2 - How to make infrared reflective pigment powder - Google Patents

Description

The present invention relates to a method for producing a powder of an infrared reflective pigment.

The heat shield function is one of the important functions in paints. In particular, in the case of a paint used for painting the outer panel of a vehicle such as an automobile, the air conditioning load in the vehicle interior can be reduced by improving the heat shielding function. This can improve the fuel efficiency or electricity cost of the vehicle and reduce the carbon dioxide emission from the vehicle.

For example, Patent Document 1 describes a coating material containing a colored metal pigment in which an amorphous silicon oxide layer and a metal layer are formed on a scaly metal base material and further coated with metal particles, and a colored pigment that reflects and / or transmits infrared rays. The composition is described. The document describes a coating film having low brightness and high saturation as a whole, which is capable of forming a coating film having a heat-shielding function and a coating film whose color changes significantly from highlight (near specular reflection light) to shade (diagonal direction). It is stated that a product and a coating film forming method can be provided.

Patent Document 2 describes the above by supplying an inert gas using a metal film forming step of forming a metal film using a first metal target and a second metal-containing target having an activated surface. It has a dielectric film forming step of forming a first dielectric film on a metal film and then forming a second dielectric film on the first dielectric film by supplying a reactive gas. A method for manufacturing a multilayer film structure will be described. The document states that the multilayer structure obtained by the above method can be used as an ND (neutral density) filter for reducing the amount of light.

Patent Document 3 describes a heat-shielding glass characterized by forming a low-radioactivity film having a vertical emissivity of 0.2 or less, which is composed of a multilayer film containing a silver layer on one side of a heat ray / ultraviolet ray absorbing green glass.

Patent Document 4 describes a first antireflection layer; a first infrared reflection film adhered on the first antireflection layer; and a second antireflection film adhered on the first infrared reflection film. Layer; second infrared reflective film adhered on top of second antireflection layer; third antireflection layer adhered on second infrared reflective film; and third antireflection layer A coating containing a third infrared reflective film adhered onto the top is described. The document describes that the antireflection layer may contain titanium oxide and the infrared reflective film may contain silver.

Japanese Unexamined Patent Publication No. 2012-36331 Japanese Unexamined Patent Publication No. 2016-194110 Japanese Unexamined Patent Publication No. 7-10609 Special Table 2005-516818

As described above, pigments having a heat-shielding function are known. However, for example, since the pigment contained in the coating composition described in Patent Document 1 is colored, it is difficult to apply it to a dark-colored coating material.

Since the multilayer film structure described in Patent Document 2 has high transparency, it is expected that the pigment obtained from the multilayer film structure described in the document can be applied to dark-colored paints without changing the color tone. NS. However, in the case of a coating film produced by using a pigment obtained from the multilayer film structure described in Patent Document 2, it has been found that the infrared reflection performance may decrease with the passage of time.

Therefore, it is an object of the present invention to provide a method for producing an infrared reflective pigment having a multi-layered film structure, which can maintain infrared reflective performance for a long period of time.

The present inventors have studied various means for solving the above problems. The present inventors have found that reduction of infrared reflection performance can be suppressed by annealing a multilayer film in which a metal film containing silver and a metal oxide film containing titanium dioxide are alternately laminated at a predetermined temperature. rice field. The present inventors have completed the present invention based on the above findings.

That is, the gist of the present invention is as follows.
(1) A method for producing an infrared reflective pigment having a multilayer structure, which is as follows:
On the surface of the substrate, a first metal film containing one or more metals selected from the group consisting of silver, gold, platinum, palladium and copper, and titanium dioxide, tantalum pentoxide, niobium pentoxide, zirconia and A second metal oxide film containing one or more metal oxides selected from the group consisting of zinc dioxide is alternately formed, and the first metal film and the second metal are formed on the surface of the base material. Multilayer film forming step of obtaining a multilayer film in which oxide films are alternately laminated;
A peeling step of peeling the obtained multilayer film from the substrate;
A grinding step of grinding the peeled multilayer film to obtain a powder of the multilayer film; and an annealing step of annealing the multilayer film or its powder at a temperature in the range of 100 to 200 ° C .;
The method, wherein the annealing step is carried out after at least one step of a multilayer film forming step, a peeling step and a grinding step.
(2) The multilayer film forming step is a metal film forming step of forming a silver-containing first metal film using a silver-containing first metal target, and a metal film forming step of forming a silver-containing first metal film, and a surface containing titanium dioxide is oxidized. A first dielectric film is formed on the first metal film by supplying an inert gas using the second metal-containing target, and then the first by supplying an oxygen-containing reactive gas. The method according to the first embodiment (1), which is carried out by alternately repeating a dielectric film forming step of forming a second dielectric film on the dielectric film of 1.
(3) The method according to the above embodiment (1) or (2), wherein the first metal film contains silver and the second metal oxide film contains titanium dioxide.
(4) The method according to any one of the above-described embodiments (1) to (3), wherein the annealing step is performed at a temperature in the range of 150 to 200 ° C.
(5) The method according to any one of the above-described embodiments (1) to (4), wherein the annealing step is carried out after the pulverization step.

INDUSTRIAL APPLICABILITY According to the present invention, it is possible to provide a method for producing an infrared reflective pigment having a multilayer film structure, which can maintain infrared reflection performance for a long period of time.

Issues, configurations and effects other than the above will be clarified by the following description of the embodiments.

FIG. 1 shows the reflection spectra of the test coating film before and after the xenon lamp type accelerated weathering test. FIG. 2 is an optical microscope image of the surface of the test coating film before the start of the weather resistance test and 1653 hours after the start of the weather resistance test. A: Image of the surface of the test coating film before the start of the weathering test, B: Image of the surface of the test coating film 1653 hours after the start of the weathering test. FIG. 3 is a scanning electron microscope (SEM) image of the surface of the test coating film 1653 hours after the start of the weathering test. A: SEM image of the surface of the test coating film 1653 hours after the start of the weather resistance test, B: Fluorescent X-ray (EDX) spectrum of the region shown in the SEM image. FIG. 4 is an optical microscope image of the surface of the test coating film after the heat resistance test is completed. FIG. 5 is an SEM image of a cross section of the infrared reflective pigment of Example 1. FIG. 6 is a reflection spectrum of the test coating films of Examples 1 to 3 and Comparative Example 1. FIG. 7 is an optical microscope image of the surface of the test coating film of Comparative Example 1 before and after the heat resistance test. A: Optical microscope image of the surface of the test coating film before the heat resistance test, B: Optical microscope image of the surface of the test coating film after the heat resistance test (200 ° C, 5 hours). FIG. 8 is an optical microscope image of the surface of the test coating film of Example 1 before and after the heat resistance test. A: Optical microscope image of the surface of the test coating film before the heat resistance test, B: Optical microscope image of the surface of the test coating film after the heat resistance test (200 ° C, 5 hours). FIG. 9 is an optical microscope image of the surface of the test coating film of Example 2 before and after the heat resistance test. A: Optical microscope image of the surface of the test coating film before the heat resistance test, B: Optical microscope image of the surface of the test coating film after the heat resistance test (200 ° C, 5 hours). FIG. 10 is an optical microscope image of the surface of the test coating film of Example 3 before and after the heat resistance test. A: Optical microscope image of the surface of the test coating film before the heat resistance test, B: Optical microscope image of the surface of the test coating film after the heat resistance test (200 ° C, 5 hours).

Hereinafter, preferred embodiments of the present invention will be described in detail.

<1. Method for manufacturing infrared reflective pigments>
One aspect of the present invention relates to a method for producing an infrared reflective pigment.

For example, a pigment having infrared reflective performance (hereinafter, also referred to as "infrared reflective pigment") is important for improving the heat shielding function of the paint as a component of the paint that can be used for painting the outer panel of a vehicle such as an automobile. Is. As known infrared reflective pigments, colored pigments such as azo pigments, aniline black and perylene black are known (Patent Document 1). Since these pigments are colored by themselves, it is difficult to apply them to dark-colored paints. This is a very important problem because dark-colored paints are required to have an improved heat-shielding function.

As a known infrared reflective pigment, a pigment having a multilayer structure having high transparency is also known (Patent Document 2). It is expected that such an infrared reflective pigment can be applied to dark-colored paints without changing the color tone. However, the present inventors have found that in the case of a coating film prepared by using a pigment obtained from the multilayer film structure described in Patent Document 2, the infrared reflection performance may decrease with the passage of time. .. It is considered that this phenomenon is caused by the precipitation of metal particles contained in the inner layer on the surface of the pigment of the multilayer film structure due to the heat load generated with the passage of time (Experiment I). In such a case, it becomes difficult to maintain the desired infrared reflection performance for a long period of time.

The present inventors have found that reduction in infrared reflection performance can be suppressed by annealing a multilayer film in which a metal film containing silver and a metal oxide film containing titanium dioxide are alternately laminated at a predetermined temperature. rice field. Therefore, the method of this embodiment includes a multilayer film forming step; a peeling step; a grinding step; and an annealing step. By the method of this embodiment including each of the above steps, an infrared reflective pigment capable of exhibiting desired infrared reflective performance for a long period of time can be produced.

The infrared reflection performance of the pigment of the prior art and the infrared reflective pigment of each aspect of the present invention is not limited, but for example, the reflection spectrum of the pigment or the coating film containing the pigment is measured and the infrared region (for example, 780) is measured. It can be evaluated by determining the reflectance for the irradiation light (in the wavelength region of nm or more).

[1-1. Multilayer film forming process]
In the method of this embodiment, a first metal film and a second metal oxide film are alternately formed on the surface of the base material, and the first metal film and the second metal oxidation are formed on the surface of the base material. It includes a multilayer film forming step of obtaining a multilayer film in which physical films are alternately laminated.

The first metal film contained in the multilayer film formed in this step contains one or more metals selected from the group consisting of metal materials such as silver, gold, platinum, palladium and copper. The first metal film preferably contains silver, more preferably made of silver. By containing the metal in the first metal film, the infrared reflective pigment produced by the method of this embodiment can exhibit infrared reflecting performance.

The second metal oxide film contained in the multilayer film formed in this step is selected from the group consisting of highly refractory metal oxide materials such as titanium dioxide, tantalum pentoxide, niobium pentoxide, zirconia and zinc dioxide. Contains one or more metal oxides. The second metal oxide film preferably contains titanium dioxide, and more preferably is made of titanium dioxide. By containing the oxide of the metal in the second metal oxide film, the infrared reflective pigment produced by the method of this embodiment can exhibit desired infrared reflecting performance for a long period of time.

The multilayer film formed in this step has a structure in which a first metal film and a second metal oxide film are alternately laminated. In this case, it is preferable that a layer of the second metal oxide film is arranged on both the upper surface and the lower surface of the multilayer film. With such a film structure, it is possible to substantially suppress the metal contained in the first metal film from being deposited on the surface of the pigment. As a result, the desired infrared reflection performance can be exhibited for a long period of time.

In this step, the means for obtaining a multilayer film in which the first metal film and the second metal oxide film are alternately laminated is not particularly limited, and the metal film and the metal oxide known in the art are not particularly limited. Various means for producing a multilayer film including a film can be applied. Examples of such means include sputtering methods such as reactive sputtering, high frequency sputtering, magnetron sputtering and the like using targets corresponding to the first metal and the second metal oxide.

Preferably, the process uses a first metal target containing one or more metals selected from the group consisting of metal materials such as silver, gold, platinum, palladium and copper to contain said metal. One or more metals selected from the group consisting of a metal film forming step of forming a metal film of 1 and a high-refractive metal oxide material such as titanium dioxide, tantalum pentoxide, niobium pentoxide, zirconia and zinc dioxide. Using a second metal-containing target whose surface containing an oxide is oxidized, a first dielectric film is formed on the first metal film by supplying an inert gas, and then oxygen is contained. It is carried out by alternately repeating the step of forming a second dielectric film on the first dielectric film by supplying a reactive gas. In this case, the first metal target preferably contains silver and the second metal-containing target contains titanium dioxide, the first metal target is made of silver, and the second metal-containing target is dioxide. More preferably it is made of titanium. A method for obtaining a multilayer film in which a first metal film and a second metal oxide film are alternately laminated by alternately repeating a metal film film forming step and a dielectric film forming step is described in, for example, Patent Document 2. Has been done. Therefore, when this step is carried out according to the above-described embodiment, specific reaction conditions and the like can be appropriately set by those skilled in the art by referring to, for example, Patent Document 2.

In the case of the above embodiment, the metal film forming step and the dielectric forming step can be carried out by a sputtering method such as reactive sputtering, high frequency sputtering and magnetron sputtering. The metal film forming step and the dielectric forming step are preferably carried out by reactive sputtering. In this case, the reactive gas used for the reactive sputtering is preferably oxygen, ozone, carbonic acid or a mixed gas thereof, and more preferably oxygen. By carrying out this step in the above-described embodiment, a multilayer film having a desired film structure can be easily formed.

The material and dimensions of the base material used in this step can be appropriately selected based on the types of the first metal film and the second metal oxide film, the means for obtaining the multilayer film, and the like. The material of the base material is preferably glass or resin (for example, acrylic, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyacrylate, etc.), and more preferably glass from the viewpoint of heat resistance. By using a base material having the above-mentioned characteristics, a desired multilayer film can be formed on the surface of the base material in this step.

The base material used in this step preferably has a release layer. The release layer is arranged at least on the surface on which the multilayer film is formed. The film thickness of the release layer is preferably in the range of 50 to 100 μm as the wet film thickness. By having the release layer, the multilayer film can be easily peeled from the base material in the peeling step described below.

When the base material used in this step has a release layer, the method of this embodiment further includes a release layer forming step of applying a release agent to the surface of the base material to form a release layer. Is preferable. The release agent used in the release layer forming step can be appropriately selected based on the material of the base material and the like. The release agent preferably contains a methacrylic acid ester polymer, polyvinyl butyral, polyvinyl alcohol, a polycarboxylic acid type polymer activator, or the like as a main component, and more preferably contains a methacrylic acid ester polymer as a main component. preferable. Further, the means for forming the release layer can be appropriately set based on the release agent used. For example, when a mold release agent containing a methacrylic acid ester polymer as a main component is used, the mold release agent is applied to the surface of the base material and left at room temperature for a certain period of time (for example, 24 hours) to release the mold. The agent can be cured to form a release layer. By having the release layer having the above-mentioned characteristics, the multilayer film can be easily peeled from the base material in the peeling step described below.

[1-2. Peeling process]
The method of this embodiment includes a peeling step of peeling the obtained multilayer film from the substrate.

In this step, the means for peeling the multilayer film from the substrate is not particularly limited. For example, the multilayer film can be peeled off from the substrate by immersing the substrate and the multilayer film in a liquid medium for a predetermined time (for example, 20 to 60 minutes). In this case, it is preferable to ultrasonically treat the base material and the multilayer film immersed in the liquid medium. The liquid medium used in this step is preferably water or a water-miscible organic solvent (eg, methanol, ethanol, isopropyl alcohol, etc.), or a mixture thereof.

By carrying out this step under the above conditions, the multilayer film can be peeled off from the substrate.

[1-3. Crushing process]
The method of this embodiment includes a peeling step of pulverizing the peeled multilayer film to obtain a powder of the multilayer film.

In this step, the means for pulverizing the multilayer film is not particularly limited. For example, the multilayer film can be pulverized by immersing the multilayer film in a liquid medium and performing ultrasonic treatment for a predetermined time (for example, 20 to 60 minutes). The liquid medium used in this step is preferably water or a water-miscible organic solvent (eg, methanol, ethanol, isopropyl alcohol, etc.), or a mixture thereof.

By carrying out this step under the above conditions, the multilayer film can be pulverized.

[1-4. Annealing process]
The method of this embodiment comprises an annealing step of annealing the multilayer film or its powder at a predetermined temperature.

When the annealing step is carried out after at least one step of the multilayer film forming step, the peeling step and the pulverizing step in the method of the present invention, the present inventors significantly reduce the infrared reflection performance of the resulting infrared reflective pigment. It was found that it was suppressed. This effect is contained in the inner layer of the multilayer film due to the heat load generated over time, which is confirmed by the pigment of the conventional multilayer film structure by annealing the multilayer film or its powder at a predetermined temperature. It is considered that this is because the precipitation of metal particles on the surface is remarkably suppressed (Experiment III). Therefore, the annealing step is carried out after at least one step of the multilayer film forming step, the peeling step and the grinding step, preferably after the grinding step. By carrying out the annealing steps in the above order, an infrared reflective pigment capable of exhibiting desired infrared reflective performance for a long period of time can be produced.

In this step, the multilayer film or its powder is annealed at a temperature in the range of 100 to 200 ° C. The annealing temperature of the multilayer film or its powder is preferably in the range of 150 to 200 ° C, more preferably about 150 ° C. When annealing is performed below the lower limit, it may not be possible to sufficiently suppress the reduction in the infrared reflection performance of the resulting infrared reflective pigment. When annealing exceeds the upper limit value, the metal contained in the first metal film may be deposited on the layer of the second metal oxide film on the surface, and the infrared reflection performance may be deteriorated. Therefore, by carrying out this step at a temperature in the above range, it is possible to produce an infrared reflective pigment capable of exhibiting desired infrared reflective performance for a long period of time.

In this step, the degree of vacuum when annealing the multilayer film or its powder is preferably in the range of ^{1.0 × 10 -3 to} 5.0 × 10 ^{-4 Pa.} When annealing below the lower limit, the metal contained in the first metal film and / or the second metal oxide film of the multilayer film may be oxidized. Therefore, by carrying out this step at a temperature in the above range, it is possible to produce an infrared reflective pigment capable of exhibiting desired infrared reflective performance for a long period of time.

<2. Infrared reflective pigment with a multi-layered film structure>
Another aspect of the present invention relates to an infrared reflective pigment having a multilayer structure obtained by the method of one aspect of the present invention.

The infrared reflective pigment of this embodiment has a structure of a multilayer film in which a first metal film and a second metal oxide film are alternately laminated. In the infrared reflective pigment of this embodiment, the first metal film and the second metal oxide film have the characteristics described above.

The infrared reflective pigment of this embodiment is usually in the form of a powder. The particle size of the infrared reflective pigment of this embodiment is usually in the range of 1 to 100 μm, preferably in the range of 10 to 30 μm. The particle size of the infrared reflective pigment of this embodiment is not limited, but is determined based on, for example, observing the pigment with an optical microscope or an electron microscope and measuring the particle size of a plurality of pigments in a microscope image. be able to.

In the infrared reflective pigment of this embodiment, the first metal film and the second metal oxide film are alternately laminated. In this case, it is preferable that a layer of the second metal oxide film is arranged on both the upper surface and the lower surface of the multilayer film. With such a film structure, it is possible to substantially suppress the metal contained in the first metal film from being deposited on the surface of the pigment. As a result, the desired infrared reflection performance can be exhibited for a long period of time.

In the infrared reflective pigment of this embodiment, the total number of multilayer films is preferably in the range of 2 to 10 layers, more preferably in the range of 2 to 5 layers, and particularly preferably in the range of 5 layers. In this case, the number of layers of the first metal film and the second metal oxide film is preferably in the range of 1 to 5 layers, respectively, and in the combination of the range of 1 to 2 layers and the range of 1 to 3 layers. It is more preferable that the first metal film has two layers and the second metal oxide film has three layers. In the infrared reflective pigment of this embodiment, since the first metal film and the second metal oxide film are alternately laminated, the first metal film has two layers and the second metal oxide film. When there are three layers, both the upper surface and the lower surface of the multilayer film are layers of the second metal oxide film. With such a film structure, it is possible to substantially suppress the metal contained in the first metal film from being deposited on the surface of the pigment. As a result, the desired infrared reflection performance can be exhibited for a long period of time.

Yet another aspect of the present invention relates to a coating composition comprising an infrared reflective pigment having a multilayer structure obtained by the method of one aspect of the present invention. The coating composition of this embodiment may contain one or more coating components such as a base resin, a curing agent, a pigment and a solvent in addition to the infrared reflective pigment of one aspect of the present invention.

Since the coating composition of this embodiment contains the infrared reflective pigment of one aspect of the present invention, it is possible to exhibit desired infrared reflective performance for a long period of time. Therefore, when the coating composition of this embodiment is applied to the outer panel coating of a vehicle such as an automobile, not only the heat shielding function of the vehicle can be improved, but also the improved heat shielding function is maintained for a long period of time. be able to.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the technical scope of the present invention is not limited to these examples.

<Experiment I. Deterioration of infrared reflection performance in conventional infrared reflective pigments>
A conventional infrared reflective pigment (manufactured by Dexerials) containing silver is added to a commercially available clear paint for automobiles (Kino 1209TW, manufactured by Kansai Paint Co., Ltd.) as a percentage of the weight% of the pigment component to the weight% of the total solid component of the paint (((). It was added so that the pigment weight concentration (PWC) represented by (% by weight of the pigment component) / (% by weight of all solid paint components) × 100) was 2.4 PWC. The prepared paint was applied to the surface of a commercially available glass substrate and baked at 140 ° C. for 30 minutes. By the above treatment, a test coating film having a film thickness of 6 μm was obtained. Table 1 shows the film composition of the infrared reflective pigment.

The weather resistance of the test coating film was tested by the xenon lamp type accelerated weather resistance test. In this test, a xenon lamp-type accelerated weathering test device (Ci5000, manufactured by Atlas) using a xenon lamp capable of irradiating light with a wavelength close to that of sunlight was used under the conditions shown in Table 2 below. This test was carried out by repeating the irradiation mode (102 minutes) and the irradiation + rainfall mode (18 minutes) until a predetermined time. The reflection spectra of the test coating film were measured before the start of the weathering test (0 hours) and at 997 hours, 1653 hours and 2288 hours after the start of the weathering test. Figure 1 shows the reflection spectra of the test coating film before and after the xenon lamp-type accelerated weathering test. In addition, the optical microscope images of the surface of the test coating film before the start of the weathering test and 1653 hours after the start of the weathering test are shown in FIG. SEM) Images are shown in Fig. 3, respectively. In FIG. 2, A shows an image of the surface of the test coating film before the start of the weathering test, and B shows an image of the surface of the test coating film 1653 hours after the start of the weathering test. In FIG. 3, A shows an SEM image of the surface of the test coating film 1653 hours after the start of the weathering test, and B shows a fluorescent X-ray (EDX) spectrum of the region shown in the SEM image.

As shown in FIG. 1, the reflectance of the test coating film with respect to the irradiation light in the infrared region having a wavelength of 780 nm or more decreased as the processing time by the xenon lamp type accelerated weathering test apparatus became longer. As shown in FIG. 2, at this time, in the test coating film for 1653 hours after the start of the weather resistance test, the surface of the pigment containing more particles in the test coating film than in the test coating film before the start of the weather resistance test. It was precipitated in. The particles precipitated on the surface of the pigment contained in the test coating film for 1653 hours after the start of the weather resistance test were confirmed to be silver particles based on the EDX spectrum (Fig. 3).

The heat resistance of the test coating film was tested by the heat resistance test. The test coating was treated at 200 ° C. for 5 hours. An optical microscope image of the surface of the test coating film after the heat resistance test is shown in FIG.

As shown in FIG. 4, in the test coating film after the heat resistance test was completed, many particles were precipitated on the surface of the pigment contained in the coating film, as in the test coating film for 1653 hours after the start of the weathering test. (See Figure 2B). In the weather resistance test, the black panel temperature for estimating the temperature of the test coating film was 63 ± 3 ° C. Considering the results of the weather resistance test and the heat resistance test, it is presumed that the heat load on the test coating film caused the precipitation of silver particles on the surface of the pigment contained in the coating film.

As described above, in the conventional coating film containing an infrared reflective pigment containing silver, silver particles are precipitated on the surface of the pigment contained in the coating film due to a heat load or the like generated with the passage of time, and infrared rays are emitted. It became clear that the reflection performance was reduced.

<Experiment II. Preparation of infrared reflective pigment>
[II-1. Example 1 (Pigment obtained by performing an annealing step after the multilayer film forming step)]
(Multilayer film forming process)
Based on the method described in JP-A-2016-194110, a carousel-type reactive sputtering apparatus (RAS1100, manufactured by Syncron Co., Ltd.) and an APC target (Ag / Pd / Cu (% by weight)) as the first metal target. = 97.4 / 0.91 / 1.69) (manufactured by Furuya Metals Co., Ltd.), using a TiOx target (oxygen deficiency: 0.5 to 10.0%) (manufactured by Dexerials) as the second metal-containing target, 5 layers on the surface of the glass substrate A multilayer film was formed. The conditions of the sputtering apparatus are as follows. Sputter chamber supply gas: Argon (Ar), Radical chamber supply gas: Oxygen (O ₂ ). Optimal power was supplied to each sputtering target by the LF frequency. Before forming the multilayer film, a mold release agent containing a methacrylic acid ester polymer as a main component is applied to the surface of a glass substrate and cured at room temperature for 24 hours to have a wet film thickness of 50 to 100 μm. A mold layer was formed. Table 3 shows the film composition of the multilayer film. In the table, the first layer is the film on the substrate side.

(Annealing process)
The resulting multilayer film was annealed at 150 ° C. for 4 hours in an atmosphere with a degree of vacuum in the range of ^{1.0 × 10 -3 to} 5.0 × 10 ^{-4 Pa.}

(Peeling process)
The multilayer film obtained in the annealing step is immersed in isopropyl alcohol and ultrasonically treated for 30 minutes using an ultrasonic cleaner (oscillation frequency: 40 kHz, output: 160 W, US-4R, manufactured by AS ONE). The multilayer film was peeled off from the substrate.

(Crushing process)
The multilayer film obtained in the peeling step is immersed in isopropyl alcohol and ultrasonically treated for 60 minutes using an ultrasonic cleaner (oscillation frequency: 40 kHz, output: 160 W, US-4R, manufactured by AS ONE). The multilayer film was pulverized to obtain a powder of an infrared reflective pigment.

[II-2. Example 2 (Pigment obtained by performing an annealing step after the peeling step)]
The multilayer film forming step was carried out under the same conditions as in Example 1. The peeling step was carried out under the same conditions as in Example 1, and the multilayer film obtained in the multilayer film forming step was peeled from the substrate. The dispersion liquid containing the multilayer film obtained in the peeling step was left at room temperature for 24 hours or more. The supernatant was discarded and the multilayer film residue was dried under vacuum. Then, the multilayer film was annealed at 150 ° C. for 4 hours in an atmosphere having a degree of vacuum in the range of ^{1.0 × 10 -3 to} 5.0 × 10 ^{-4 Pa (annealing step).} The multilayer film obtained in the annealing step was subjected to a pulverization step under the same conditions as in Example 1 to obtain an infrared reflective pigment powder.

[II-3. Example 3 (Pigment obtained by performing an annealing step after the pulverization step)]
The multilayer film forming step was carried out under the same conditions as in Example 1. The peeling step was carried out under the same conditions as in Example 1, and the multilayer film obtained in the multilayer film forming step was peeled from the substrate. The multilayer film obtained in the peeling step was subjected to a pulverization step under the same conditions as in Example 1 to obtain a dispersion liquid containing the powder of the multilayer film. The obtained dispersion was left at room temperature for 24 hours or more. The supernatant was discarded and the residue of the multilayer film powder was dried under vacuum. Then, the multilayer film powder was annealed at 150 ° C. for 4 hours in an atmosphere with a degree of vacuum in the range of ^{1.0 × 10 -3 to} 5.0 × 10 ^{-4 Pa (annealing step).} By the above procedure, a powder of an infrared reflective pigment was obtained.

[II-4. Comparative Example 1 (Pigment obtained without performing annealing step)]
In the multilayer film forming step of Example 1, the multilayer film was formed by the same procedure as described above except that the substrate used was changed to a resin substrate containing a methacrylic polymer as a main component. The obtained multilayer film of Comparative Example 1 was immersed in isopropyl alcohol for 20 to 60 minutes to peel off the multilayer film from the substrate (peeling step). The multilayer film obtained in the peeling step was subjected to a pulverization step under the same conditions as in Example 1 to obtain an infrared reflective pigment powder.

<Experiment III. Survey of properties of infrared reflective pigments>
An SEM image of a cross section of the infrared reflective pigment of Example 1 is shown in FIG. As shown in FIG. 5, it was confirmed that the infrared reflective pigment of Example 1 was a five-layer multilayer film (see Table 3).

The infrared reflective pigment of any of Examples 1 to 3 and Comparative Example 1 was added to a commercially available clear paint for automobiles (Kino 1209TW, manufactured by Kansai Paint Co., Ltd.) so as to have 2.4 PWC. The prepared paint was applied to the surface of a commercially available glass substrate and baked at 140 ° C. for 30 minutes. By the above treatment, a test coating film having a film thickness of 6 μm was obtained. The reflection spectra of the test coating films of Examples 1 to 3 and Comparative Example 1 were measured. The reflection spectrum of each test coating film is shown in FIG.

As shown in FIG. 6, the test coating films of Examples 1 to 3 and Comparative Example 1 all had substantially the same pattern of reflection spectra. From this result, it is suggested that the infrared reflecting pigments of Examples 1 to 3 and Comparative Example 1 have substantially the same infrared reflecting performance.

The heat resistance of the test coating films of Examples 1 to 3 and Comparative Example 1 was tested under the condition of 200 ° C. for 5 hours by the same procedure as I. Optical microscope images of the surface of each test coating film before and after the heat resistance test were obtained. The optical microscope images of the surface of the test coating film of Comparative Example 1 before and after the heat resistance test are shown in FIG. 7, and the optical microscope images of the surface of the test coating film of Examples 1 to 3 before and after the heat resistance test are shown in FIGS. 8 to 10. , Respectively. In the figure, A shows an optical microscope image of the surface of the test coating film before the heat resistance test, and B shows an optical microscope image of the surface of the test coating film after the heat resistance test (200 ° C., 5 hours). .. Using image analysis software (WinROOF, manufactured by Mitani Shoji Co., Ltd.), the obtained optical microscope image was binarized to calculate the area of the white region corresponding to the bright spot of the silver particles. Table 4 shows the area values of the white region in the optical microscope image of the surface of the test coating film of Examples 1 to 3 and Comparative Example 1 before and after the heat resistance test. In the table, the area value is shown as a relative value with respect to the area before the heat resistance test.

As shown in Table 4, in the test coating film of Comparative Example 1 after the heat resistance test, the area value of the white region corresponding to the bright spot of the silver particles is larger than that of the test coating film before the heat resistance test. Increased (Fig. 7). On the other hand, in the test coating films of Examples 1 to 3, the increase in the area value of the white region on the surface of the test coating film after the heat resistance test was remarkably suppressed (FIGS. 8 to 10). In particular, in the test coating film of Example 3, the area value of the white region on the surface of the test coating film after the heat resistance test was about the same as the area value before the heat resistance test (1.1). From this result, it was clarified that the precipitation of silver particles due to heat load and the like was remarkably suppressed in the test coating films of Examples 1 to 3, especially Example 3.

The present invention is not limited to the above-described embodiment, and includes various modifications. For example, the above-described embodiment has been described in detail in order to explain the present invention in an easy-to-understand manner, and is not necessarily limited to those having all the described configurations. In addition, it is possible to add, delete, and / or replace a part of the configuration of each embodiment with another configuration.

Claims (5)

A method for producing an infrared reflective pigment having a multilayer structure, which is as follows:
On the surface of the substrate, a first metal film containing one or more metals selected from the group consisting of silver, gold, platinum, palladium and copper, and titanium dioxide, tantalum pentoxide, niobium pentoxide, zirconia and A second metal oxide film containing one or more metal oxides selected from the group consisting of zinc dioxide is alternately formed, and the first metal film and the second metal are formed on the surface of the base material. Multilayer film forming step of obtaining a multilayer film in which oxide films are alternately laminated;
A peeling step of peeling the obtained multilayer film from the substrate;
The peeled multilayer film is crushed to obtain a multilayer film powder, a pulverization step; and the multilayer film or its powder is vacuumed in the range of 1.0 × 10 ^{-3 to} 5.0 × 10 ^-4 Pa, and 100 to 200. Annealing step, annealing at a temperature in the range of ° C;
The method, wherein the annealing step is carried out after at least one step of a multilayer film forming step, a peeling step and a grinding step. The multilayer film forming step is a metal film forming step of forming a silver-containing first metal film using a silver-containing first metal target, and a metal film forming step of forming a silver-containing first metal film, and a titanium dioxide-containing surface being oxidized. Using the metal-containing target of 2, a first dielectric film is formed on the first metal film by supplying an inert gas, and then the first dielectric is supplied by supplying an oxygen-containing reactive gas. The method according to claim 1, which is carried out by alternately repeating a dielectric film forming step of forming a second dielectric film on the body film. The method according to claim 1 or 2, wherein the first metal film contains silver and the second metal oxide film contains titanium dioxide. The method according to any one of claims 1 to 3, wherein the annealing step is carried out at a temperature in the range of 150 to 200 ° C. The method according to any one of claims 1 to 4, wherein the annealing step is carried out after the pulverization step.

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