JPWO2004046057A1 - Thermal shielding plate, method for producing the same, and liquid composition used therefor - Google Patents

Abstract

According to the present invention, there is provided a heat shielding plate in which a heat shielding film in which ITO fine particles are dispersed is formed on a substrate such as a glass plate. This film contains silicon oxide and at least two kinds of alkali metal oxides together with ITO fine particles, is excellent in oxygen shielding ability, and is suitable for maintaining and enhancing the heat ray shielding ability by ITO fine particles. This heat shielding film can be mass-produced by applying a liquid composition containing at least two kinds of alkali silicate, a solvent and ITO fine particles on a substrate and drying it.

Description

  The present invention relates to a heat shield plate that is particularly useful as a window glass for vehicles and buildings. The present invention further relates to a method for producing the heat shielding plate and a liquid composition used therefor.

A film in which ITO (indium tin oxide) fine particles are dispersed shields light in the infrared region while transmitting light in the visible region. The glass plate on which this film is formed has desirable characteristics as a window glass for vehicles and buildings. This glass plate is also used as a transparent electrode, a touch panel, etc. based on the conductivity derived from the ITO fine particles.
The oxygen defect of ITO contributes to the conductivity and heat ray shielding ability (heat shielding property) of the ITO fine particles. For this reason, as disclosed in JP-A-7-21831, if heat treatment is performed in a pressurized inert gas atmosphere, the ITO fine particles have a low resistance.
Japanese Patent Laid-Open No. 7-70363 discloses an organic resin film in which ITO fine particles are dispersed. Examples of the organic resin film include polyvinyl chloride resin and acrylic resin. However, since the organic resin film is inferior in weather resistance and wear resistance, it is not suitable for use in a form in which the film is exposed, for example, as a window glass.
JP-A-8-199096 discloses an ITO fine particle-containing film formed from a liquid composition containing no binder such as an organic resin. This liquid composition contains a coupling agent in order to disperse the ITO fine particles. This film has a low haze ratio and a low surface resistance value (10 ¹ to 10 ² Ω / square order) and is suitable for use as a touch panel or the like. However, since this film must be baked in an inert or reducing atmosphere, a special apparatus is required for its formation. For this reason, this film | membrane is not suitable for the formation on the glass plate large to such an extent that it can be used as a window glass.
JP-A-8-259279 discloses a laminated glass using an intermediate film in which ITO fine particles are dispersed. Examples of the intermediate film include a polyvinyl butyral film and an ethylene-vinyl acetate copolymer film. When used as a laminated glass, the low weather resistance of the intermediate film made of an organic resin does not cause a problem in practice. However, this technique cannot be applied to film formation on a single plate that does not use an intermediate film.
JP-A-9-176527 discloses an ITO fine particle-containing film formed from a two-component liquid composition. This film is formed by applying silica sol as the second liquid on the powder layer (first layer) formed from the first liquid not containing the binder. The silica sol is impregnated in the powder layer to become a binder for the ITO fine particles, and forms a silica layer (second layer) on the powder layer. According to the above publication, since the first layer is formed from a liquid composition not containing a binder, the dispersion density of the fine particles is increased, and as a result, a high heat ray shielding ability is obtained. However, this technique requires at least two film forming steps.
As described above, as a film other than the organic resin for dispersing the ITO fine particles, a film formed from a liquid composition containing no binder has been proposed. However, when a liquid composition containing no binder is used, it is impossible to form a heat-shielding film that can be used practically by a single film formation in the atmosphere by any technique.
On the other hand, although it is not a liquid composition for forming an ITO fine particle-containing film, JP-A-2002-29782 discloses a transparent coloring liquid for glass containing sodium silicate, lithium silicate and a colorant. An inorganic pigment or a gold or silver colloidal solution is added to the coloring liquid as a coloring agent. This publication discloses a colored film having a thickness of about 300 nm formed by dip coating.

In order to disperse ITO fine particles necessary for imparting a desired heat shielding property, a certain degree of thickness is required for the film serving as a dispersion medium. However, for example, a non-organic dispersion medium disclosed in the above-mentioned JP-A-9-176527, that is, a silica film by a sol-gel method as an inorganic binder, tends to cause cracks when a thick film is formed in one film formation process. Become. A fine crack is likely to occur in a silica film formed to a film thickness exceeding 200 nm by the sol-gel method. This crack becomes an oxygen supply path to the ITO fine particles in the film, and deteriorates the ITO fine particles even in the heating step essential for the sol-gel method that does not reach a high temperature. In this case, it cannot be used for a process involving heating to a higher temperature such as bending, which may be required for a window glass.
In a film formed from an alkali silicate such as sodium silicate, the transparency of the film is impaired when the alkali component is combined with carbon dioxide in the air. Because of this so-called efflorescence, coating technology using alkali silicate has been applied only in limited fields such as the formation of colored films. However, although not paid attention in the past, according to this coating technique, a film having excellent oxygen shielding ability can be provided. Therefore, if this technique is applied, a liquid composition containing ITO fine particles is used, and in a single film-forming process in an oxygen-containing atmosphere, for example, the thickness exceeds 0.3 μm, and further increases to 0.4 μm or more. Even if formed, the deterioration of the ITO fine particles can be suppressed to such an extent that it does not cause a problem in practice. The white flower phenomenon, which has been regarded as a problem in the past, can be improved by appropriately selecting the film composition, production method and the like.
Based on the above, the present invention includes a substrate and a heat shielding film formed on the substrate, and the heat shielding film includes a silicon oxide, at least two alkali metal oxides, and ITO fine particles. A shielding film is provided.
Another aspect of the present invention is a method for producing a heat shielding plate including a substrate and a heat shielding film formed on the substrate, wherein at least two kinds of alkali silicate, a solvent, and Provided is a production method for forming a heat shielding film by applying a liquid composition containing ITO fine particles and removing the solvent from the liquid composition.
From another aspect, the present invention provides a liquid composition for forming a heat shielding film comprising at least two alkali metal oxides, a solvent, and ITO fine particles.
According to the present invention, it is possible to manufacture a heat shielding plate provided with heat shielding properties by the heat ray shielding ability of ITO fine particles using existing mass production equipment. Moreover, according to the present invention, it is also possible to provide a heat shielding plate in which the heat shielding property due to the ITO fine particles does not deteriorate even when heated in the atmosphere at a high temperature, for example, 500 ° C. or higher, which is necessary when the glass plate is bent. Is possible.

FIG. 1 is a cross-sectional view showing one embodiment of a heat shield plate according to the present invention.
FIG. 2 is a cross-sectional view showing an embodiment of the heat shielding plate according to the present invention, in which a glass plate serving as a substrate is bent.
FIG. 3 is a cross-sectional view showing an example of a bent laminated glass including a heat shielding plate according to the present invention.
FIG. 4 is a cross-sectional view showing another example of a bent laminated glass including a heat shielding plate according to the present invention.
FIG. 5 is a diagram illustrating the relationship between the light transmittance at a wavelength of 1500 nm (hereinafter referred to as “T1500”) and the heat treatment temperature of the heat shielding plate according to the present invention.
FIG. 6 is a diagram showing a relationship between T1500 of a glass plate having a film formed only from an ITO fine particle aqueous dispersion and a heat treatment temperature.

The heat shielding film according to the present invention can exhibit an excellent oxygen shielding ability. This oxygen shielding ability suggests that this film is a dense glassy film. With this function, even if the heat shielding film in which ITO fine particles are dispersed is heated in an oxygen-containing atmosphere such as the air, deterioration of the ITO fine particles due to reduction of oxygen defects can be suppressed.
As confirmed by experiments, ITO fine particles deteriorate significantly when heated to a temperature exceeding 100 ° C. However, according to the oxygen shielding ability, for example, when a heat shielding plate including a glass plate as a substrate is left in the atmosphere at 250 ° C. for 60 minutes, the light transmittance at a wavelength of 1500 nm is, for example, 3%, preferably 1%. Deterioration of the ITO fine particles can be suppressed to such an extent that it does not increase.
The degree of heat shielding by the ITO fine particles can be evaluated by T1500 or solar transmittance (Tg). When the substrate is a glass plate, T1500 in the heat shielding plate of the present invention is, for example, 40% or less, preferably 30% or less, more preferably 20% or less. The solar transmittance is, for example, 60% or less, preferably 50% or less, and more preferably 45% or less.
The heat shielding plate of the present invention can have a high light transmittance in the visible region at the same time while exhibiting the above-described heat shielding properties. When the substrate is a glass plate, this transmittance is expressed by visible light transmittance (Ya), and is preferably 70% or more. Such high visible light transmittance exceeds the standard required for a part of window glass for automobiles. When legal regulations require a higher visible light transmittance, for example, 75% or more, it is also possible to provide a heat shielding plate having a visible light transmittance that satisfies this standard.
The thickness of the heat shielding film according to the present invention preferably exceeds 0.3 μm, more preferably 0.4 μm or more, and particularly preferably 0.5 μm or more. If the film thickness is too thin, it is difficult to disperse a sufficient amount of ITO fine particles, and high heat ray shielding ability cannot be obtained. Unlike a colored film that disperses an inorganic pigment or the like, it is desirable that the heat shielding film that disperses the ITO fine particles is formed to such a thickness. Even a thick film of the above degree can be formed by a single application and drying of the liquid composition if an appropriate application method is employed.
Although there is no restriction | limiting in the upper limit of the film thickness of a heat-shielding film | membrane, when a too thick film | membrane is heated rapidly, foaming and a crack may arise. The preferable film thickness of the heat shielding film is more than 0.3 μm and not more than 3 μm.
As disclosed in JP-A-8-199096, when formed from a liquid composition not containing a binder, the dispersion density of ITO fine particles in the film increases. However, if a heat shielding plate having a reduced surface resistance value that is closely packed with ITO fine particles is used as a window glass, there is a risk of hindering transmission of radio waves into the room. Considering this, the surface resistance value of the heat shielding film is preferably 10 ⁶ Ω / square (Ω / □) or more, particularly preferably 20 × 10 ⁶ Ω / square or more. If the thickness of the heat shielding film is appropriately adjusted to the above level, it is possible to obtain a sufficient heat ray shielding ability while maintaining a high surface resistance value.
The composition of the heat-shielding film is not limited as long as preferable characteristics are obtained, but usually expressed in terms of mass%, 30 to 70% silicon oxide, 5 to 30% alkali metal oxide, and 1 to 50% ITO. A film containing fine particles is preferable.
Silicon oxide (SiO ₂ ) forms a glass skeleton. If the silicon oxide is less than 30% by mass, the film strength is insufficient. On the other hand, when the silicon oxide exceeds 70% by mass, the film formability is lowered, or the oxygen shielding ability of the film is lowered. A more preferable content of silicon oxide is 32 to 66% by mass. A high ratio of silicon oxide is effective in suppressing the white flower phenomenon.
Alkali metal oxides (R ₂ O; R is preferably at least two selected from Na, K and Li) together with silicon oxide form a dense glassy film. If the alkali metal oxide is less than 5% by mass, the film formability is lowered, or the thermal expansion coefficient of the film is too small compared to soda lime silica glass which is a general-purpose substrate. On the other hand, when the alkali metal oxide exceeds 30% by mass, the thermal expansion coefficient of the film becomes too larger than that of soda lime silica glass. If the difference in thermal expansion coefficient is too large, the film strength is lowered. The more preferable content of the alkali metal oxide is 8 to 16% by mass.
The dispersion amount of the ITO fine particles is 1 to 50% by mass, particularly 10 to 50% by mass. If the ITO fine particles are less than 1% by mass, the heat shielding property of the film is too low. On the other hand, if the ITO fine particles exceed 50% by mass, the fine particles are hardly retained in the film, and the film strength is also lowered. A more preferable content of the ITO fine particles is 20 to 40% by mass.
The ITO fine particles have an absorption edge at 700 to 900 nm, have a characteristic of reflecting or absorbing infrared light having a wavelength longer than that, and are suitable for both high visible light transmittance and high heat shielding properties. In order to realize preferable optical characteristics, the average primary particle size of the ITO fine particles is preferably 100 nm or less, for example, 10 nm to 100 nm. In the film, the ITO fine particles are preferably in a monodispersed state. If the particle size of the ITO fine particles is too large or the ITO fine particles are aggregated, the film is clouded and becomes a factor of increasing the haze ratio.
In the heat shielding film according to the present invention, the presence of the two alkali metal oxides provides the heat shielding film with improved moisture resistance and chemical durability. For this reason, this heat shielding film is more suitable for outdoor use than a film containing only one kind of alkali metal oxide. The heat shielding film preferably contains sodium oxide and at least one selected from lithium oxide and potassium oxide as the at least two kinds of alkali metal oxides, and more preferably contains sodium oxide and lithium oxide.
In order to suppress the white flower phenomenon, it is preferable to relatively increase the ratio of lithium oxide in the alkali metal oxide. Considering this, the mass of lithium oxide in the film is appropriately 33 to 90%, more preferably 60 to 90% of the mass of the alkali metal oxide. In the above Japanese Patent Laid-Open No. 2002-29782, the lithium ratio is disclosed by silicate, but the upper limit of this ratio (lithium silicate / sodium silicate = 8/2) is assumed to use the most general-purpose silicate. In terms of oxide, it corresponds to a lithium oxide ratio of about 55%.
The substrate is not particularly limited, but a glass plate is preferable. A substrate having a base film previously formed on the surface of the glass plate may be used. According to the present invention, it is possible to provide a heat shield plate in which the substrate includes a glass plate, the visible light transmittance (Ya) is 70% or more, the solar radiation transmittance (Tg) is 50% or less, and T1500 is 20% or less. This heat shielding plate has high heat shielding properties and high visibility, and is suitable for use as a window glass. Similarly, according to this invention, the board | substrate contains a glass plate and can provide the heat shielding board whose haze rate is 5% or less. When used as a window glass for automobiles, the haze ratio of the heat shielding plate is preferably 2% or less, more preferably 1% or less.
When a communication function using an optical beacon is mounted on an automobile, the communication is performed through the window glass (mainly windshield) of the automobile. In this case, the light transmittance (hereinafter referred to as “T850”) at a wavelength of 850 nm considering the communication wavelength range (800 to 900 nm) by the optical beacon is preferably 30% or more. In order to realize this, the composition and thickness of the heat shielding film may be appropriately adjusted according to the thickness and optical characteristics of the glass plate serving as the substrate.
Unlike a colored film, light absorption in the visible region by dispersed fine particles is rather undesirable in a heat shielding film. The heat shielding film is preferably substantially colorless. Here, “substantially colorless” means that the chromaticity of the transmission color of the heat shielding plate and the chromaticity of the transmission color of the substrate used are displayed by a and b in the Hunter color system. And at least one digit after the decimal point. The heat shielding film according to the present invention may be substantially free of inorganic pigments and metal colorants. Here, the inorganic pigment and the metal colorant refer to materials exemplified in the above Japanese Patent Application Laid-Open No. 2002-29782, and in detail, the content is less than 0.1% by mass. Say something.
The heat shielding film can be formed, for example, by applying a liquid composition on a substrate and removing the solvent from the liquid composition. The liquid composition preferably contains at least two types of alkali silicate (alkali metal silicate), a solvent, and ITO fine particles. Specifically, water glass, that is, a concentrated aqueous solution of alkali silicate may be added to the liquid composition. A typical water glass can be represented by Na ₂ O · nSiO ₂ (n: any positive number, for example, 0.5 to 4.0). When water glass or an ITO fine particle aqueous dispersion described later is used, the liquid composition contains water as a solvent. However, the solvent is not limited to this, and includes, for example, ethyl alcohol, isopropyl alcohol and the like together with water. You may go out.
Potassium oxide and lithium oxide are also preferably supplied from an aqueous solution of alkali silicate. These other alkali metals are, for example, Li ₂ O · nSiO ₂ (n: any positive number, for example, 3.5 to 7.5), K ₂ O · nSiO ₂ (n: any positive number, for example, 2.9-3.3) can be supplied from an aqueous solution of alkali silicate.
Alkali silicate is a raw material that supplies both alkali metal oxides and silicon oxides. However, the liquid composition may further include alkali silicates and silicon oxides as necessary so as to have an appropriate composition range. Add an appropriate amount. In this case, the silicon oxide can be added as silicon oxide fine particles, for example. The silicon oxide fine particles may be supplied from, for example, colloidal silica. Also for silicon oxide fine particles, if the particle size is too large, the film becomes cloudy, so the primary particle size is preferably 200 nm or less. The particle diameter of the silicon oxide fine particles may be reduced by dissolving with an alkali component contained in the liquid composition.
In particular, when the heat shielding film is heated to a high temperature, the colloidal silica is preferably free from an organic dispersion. This is because if the decomposed organic residue remains in the film, the transparency of the heat shielding film may be impaired.
The ITO fine particles may be added to the liquid composition as an aqueous dispersion, for example. In this aqueous dispersion, the solid content mass ratio of the ITO fine particles is preferably 5% or more. When the solid content mass ratio is less than 5%, it may be difficult to disperse a sufficient amount of ITO fine particles. In this aqueous dispersion, the mass of the dispersant with respect to the mass of the ITO fine particles is preferably 40% or less, particularly preferably 20% or less. When this mass ratio exceeds 40%, the fastness of the film may be impaired. The lower limit of the mass ratio is not particularly limited, but may be an amount sufficient to uniformly disperse the ITO fine particles in the dispersion.
The liquid composition may be adjusted in its component ratio so that the heat shielding film has the above-mentioned proper composition. Specifically, the solid content of the silicon oxide in terms of 30% to 70% expressed in mass% is converted. It is preferable to contain 5 to 30% converted alkali metal oxide and 1 to 50% ITO fine particles. The solid content concentration of the liquid composition may be appropriately determined according to the coating method or the like, but is preferably 30% or less. If this concentration exceeds 30%, uniform coating becomes difficult and cracks are likely to occur in the film due to stress during drying.
The liquid composition may be applied using various conventionally known methods such as bar coating, spin coating, spray coating, flow coating, roll coating, dip coating, brush coating, screen printing, and inkjet coating. That's fine.
After application, a drying step is performed to remove the solvent from the liquid composition. This step may be performed at room temperature or under heating, but after drying at room temperature, it is preferable to heat and further dry. This is because if the removal of the solvent is not sufficient, white heat is likely to occur in the heat shielding film.
Heating in the drying step is not particularly limited. However, when a film is formed from an alkali silicate such as water glass, the liquid composition is heated to 100 ° C. or higher, more preferably 120 ° C. or higher in consideration of the durability of the film. It is preferable to heat. When heated to such a temperature, the film becomes dense. There is no upper limit to this temperature, but if it is too high, the solvent may be rapidly removed depending on the rate of temperature rise, and foaming may occur or cracks may occur in the film. For this reason, in a drying process, it is good to limit heating to 300 degrees C or less. The heating time may be a time sufficient to sufficiently remove the solvent from the liquid composition, depending on the heating temperature, the amount of the applied liquid composition, and the like, for example, at least 10 minutes. Thus, a heat shielding film is formed on the substrate, and a heat shielding plate is obtained.
The heat shield plate may be further heated to a temperature above the temperature in the drying step. In particular, when the substrate includes a glass plate, heating to a high temperature may be required for processing the glass plate. For example, in this heating step, the glass plate is subjected to at least one process selected from a strengthening process and a bending process, for example, a simultaneous bending and strengthening process. For this treatment, the glass plate is indicated by the temperature of the glass plate and preferably heated to 500 ° C. to 730 ° C. Thus, a tempered glass, a bent glass or a bent tempered glass having a heat shielding film can be obtained.
According to the present invention, deterioration of the ITO fine particles can be suppressed even when the above-described series of steps, that is, application of the liquid composition, drying, and heating to a higher temperature are all performed in the air. Moreover, even if the liquid composition is supplied so that the film thickness exceeds 0.3 μm, for example, more than 0.3 μm and not more than 3.0 μm by a single application, deterioration of the ITO fine particles is suppressed. A heat shielding film can be formed. Each of the above steps does not require a special device for adjusting the atmosphere, and can basically be implemented using existing mass production equipment.
Surprisingly, it was confirmed that when the heat shielding film according to the present invention is heated, the heat ray shielding ability of the ITO fine particles may be improved even when it is heated in the atmosphere. This means that the same effect as that of the reduction treatment (see the above-mentioned JP-A-7-21831) can be obtained only by dispersing ITO fine particles in a dense glassy film and performing a heat treatment. This effect can be confirmed, for example, as a decrease in T1500 and / or a decrease in solar transmittance when the substrate is a glass plate. The improvement of the characteristics of the ITO fine particles may be performed by heating in an atmosphere of 350 ° C. or higher. For example, when it is left in the atmosphere at 720 ° C. for 120 seconds, the characteristic improvement effect of the ITO fine particles is recognized due to the decrease in T1500.
Therefore, it is preferable to further heat at least one selected from T1500 of the heat shielding plate and solar transmittance by heating the heat shielding plate after forming the film, as compared to before heating. According to this, it is possible to improve the properties of ITO without requiring an inert gas atmosphere. Although there is no upper limit to the heating temperature, it is preferably 730 ° C. or lower in consideration of the heat resistance temperature of the film or substrate. The heating for improving the characteristics may be performed simultaneously with the heating for processing the glass plate.
Hereinafter, specific examples of the heat shielding plate of the present invention will be described with reference to the drawings.
In the heat shielding plate shown in FIG. 1, a heat shielding film 1 is formed on a glass plate 2 serving as a substrate. In this heat shielding film 1, ITO fine particles 3 are dispersed. The heat shielding plate 4 shown in FIG. 2 is bent so that the glass plate 2 has a convex surface and a concave surface, and the heat shielding film 3 is formed on the concave surface of the glass plate 2. This heat shielding plate 4 is suitable for a side window of an automobile, for example. In order to use for a side window, it is good to give a strengthening process with a bending process to a glass plate.
As shown in FIG. 3, the heat shielding plate according to the present invention may be used as a glass plate constituting the laminated glass. A laminated glass 5 shown in FIG. 3 includes a heat shielding plate 52 according to the present invention. In this laminated glass 5, the heat shielding plate 52 is used as a glass plate on the indoor side, and is composed of another glass plate 51 disposed on the outdoor side and a resin intermediate film 53 such as a polyvinyl butyral (PVB) film. It is joined. The heat shielding film 1 is formed on a so-called third surface (the third glass surface counted from the outdoor side). This bent laminated glass is suitable for a windshield of an automobile.
As shown in the figure, when the heat shielding film is formed on the second or third surface of the laminated glass, that is, the surface that is not exposed to the atmosphere, the film does not come into direct contact with carbon dioxide in the atmosphere, so that the white flower phenomenon hardly occurs. Become. For this reason, when arrange | positioning a heat shielding film in the surface which is not exposed to air | atmosphere, the necessity of the process of heating the apply | coated liquid composition and fully removing a solvent prior to a matching process becomes comparatively small. However, as shown in FIG. 4, the heat shielding film 1 may be formed on the first surface or the fourth surface (the fourth surface in FIG. 4) of the laminated glass 5.
The glass plate may be a colorless glass plate or a colored glass plate. Examples of the colored glass plate include a green color tone glass plate, a bronze color tone glass plate, a green color tone glass plate having an ultraviolet absorption function, and a bronze color tone glass plate having an ultraviolet absorption function. If a laminated glass in which these are appropriately combined, desired optical characteristics can be easily realized.
In the case of forming a heat shielding film on bent glass, it is preferable to first form a heat shielding film on a flat glass plate according to the above steps, and then bend the glass plate. Application of the liquid composition to a flat surface is advantageous for forming a uniform and thick film. However, the liquid composition may be applied to a glass plate that has been previously bent and heated to form a heat shielding film. The substrate (glass plate) as a target to which the liquid composition is applied preferably has a flat surface, but is not limited thereto.

Hereinafter, all the percentages indicating the component ratios are mass%. The following operations were all performed in the atmosphere. The main evaluation method of the characteristic of the glass plate with a heat shielding film obtained in the following examples is shown below.
-Transparency The haze rate was measured using a haze meter (turbidimeter, Suga Test Instruments, HGM-2DP).
Light transmittance Using a spectrophotometer (manufactured by Shimadzu Corporation, UV-3000PC), transmittance at wavelengths of 850 nm and 1500 nm (T850 nm, T1500 nm) and visible light transmittance calculated according to Japanese Industrial Standards (JIS (Japan Industrial Standard) R3106) The rate (Ya) and solar transmittance (Tg) were measured.
-Film thickness The film thickness of the heat shielding film was measured using a surface shape measuring device (manufactured by TENCOR INSTRUMENTS, ALPHA-STEP 200).

Sodium silicate aqueous solution (water glass No. 3, manufactured by Kishida Chemical), potassium silicate aqueous solution (Snowtex K, manufactured by Nissan Chemical Industries), water-dispersed colloidal silica (KE-W10, particle size 110 nm, manufactured by Nippon Shokubai), ITO fine particle aqueous dispersion A liquid composition for forming a heat shielding film was obtained by weighing a predetermined amount of the body (particle size: 50 nm, manufactured by Sumitomo Metal Mining Co., Ltd.) and purified water, and mixing and stirring.
About 0.2 mL of this liquid is dropped on a washed float glass plate (100 × 100 × 3.4 mm), spread and coated by a bar coater, dried at room temperature, and further in a 250 ° C. drying oven for 10 minutes. Dried.
The colloidal silica contained 15% by mass of SiO _2, and the ITO fine particle aqueous dispersion contained 20% by mass of ITO fine particles. The optical properties of the glass plate were Ya: 83%, Tg: 63%, T1500 nm: 59%, T850 nm: 47%, and haze ratio: 0%.
Various characteristics of the glass plate with the heat shielding film thus obtained were measured. Table 1 shows the amount of each component contained in the liquid composition, the solid mass ratio of each component, the application method and conditions of the liquid composition, the temperature and time of the drying step, together with the properties measured above. Tables 1 and 2 show the production conditions and characteristics of the following examples and comparative examples.

A glass plate with a heat shielding film was obtained in the same manner as in Example 1 except that a spin coater was used instead of the bar coater. Spin coating was performed at 16.6 revolutions per second (= 1000 rpm) for 5 seconds.
Compared to Example 1, film formation by spin coating is more suitable for thick film formation than bar coating, and even if a liquid composition having the same ITO concentration is used by adjusting the film thickness, Ya or Tg It can be confirmed that the optical characteristics such as can be adjusted.

Examples 3-5

A glass plate with a heat shielding film was obtained in the same manner as in Example 1 except that a lithium silicate aqueous solution (LSS35, manufactured by Nissan Chemical Industries, Ltd.) was used instead of the potassium silicate aqueous solution, and the component ratio was appropriately changed.
If the amount of ITO fine particles is increased, the heat shielding property is improved, but Ya is slightly lowered, and the haze ratio is slightly increased.

Examples 6-7

The glass plate with a heat shielding film obtained in Examples 3 to 4 was heated in a baking furnace at 720 ° C. for 120 seconds. By this heating, the temperature of the glass plate rose to 650 ° C. Table 1 shows the characteristics of the glass plate with the heat shielding film after heating.
Comparing Examples 3 and 6 and Examples 4 and 7, respectively, it can be confirmed that T1500 and the solar radiation shielding rate were lowered despite being heated in the atmosphere.

In this example, a laminated glass was produced. First, a glass plate with a heat shielding film was obtained in the same manner as in Example 3. However, the thickness of the glass plate was changed to 2.1 mm, and the coating method of the liquid composition was spin coating under the same conditions as in Example 2. Moreover, after apply | coating the liquid composition dried at room temperature, the drying by heating was not performed but it was set as the single plate glass for laminated glasses as it was.
The combining step was performed by joining a glass plate with a heat shielding film and the same float glass used for applying the liquid composition with a PVB film. Specifically, first, temporary adhesion was performed by heating to 70 ° C. under reduced pressure, and then main bonding was performed using an autoclave under the conditions of 140 ° C. and 14 kg / cm ² . The heat shielding film was disposed in contact with the PVB film. Table 1 shows the optical characteristics of the obtained laminated glass with a heat shielding film.
The size of the glass plate used in Example 8 is 100 × 100 × 2.1 mm, and its optical characteristics are Ya: 84%, Tg: 69%, T1550 nm: 66%, T850 nm: 60%, haze ratio : 0%.

Implemented except that the component ratio in the liquid composition was changed to increase the ratio of lithium oxide in the film, and the coating method was spin coating under conditions of 10 seconds at 5 revolutions per second (= 300 rpm) and the drying time was 1 hour. In the same manner as in Example 3, a glass plate with a heat shielding film was obtained. The glass temperature in the drying process reached 250 ° C.
The optical properties of the glass plate used in Example 9 were Ya: 73%, Tg: 45%, T1500 nm: 38%, T850 nm: 27%, and haze ratio: 0%, and transmitted light by the Hunter color system. The chromaticity was a: -8.0, b: 3.3.

Examples 10-14

A glass plate with a heat-shielding film was prepared in the same manner as in Example 9 except that the water-dispersed colloidal silica was not added to the liquid composition and the component ratio was adjusted so that the ratio of lithium oxide in the alkali metal oxide was sequentially reduced. Obtained. In these examples, the haze rate after each glass plate with a heat shielding film was left in a room at 30 to 35 ° C. for one month was also measured.
If the ratio of lithium oxide in the alkali metal oxide is increased, the white flower phenomenon that proceeds after the production can be suppressed to some extent.

A glass plate with a heat shielding film was obtained in the same manner as in Example 10. However, in this example, the liquid composition was dried only at room temperature, and drying by heating was not performed.
As compared with Example 10, it can be confirmed that even when heated at 250 ° C. for drying, the heat ray shielding ability by the ITO fine particles is not substantially affected.
In addition, the transmitted color of the heat shielding plate obtained in Examples 10 and 15 was the same as the glass plate used (a: -8.0, b: 3.3). This confirmed that the heat shielding film was substantially colorless.
Furthermore, when the surface resistance value of the heat shielding film according to Examples 6 and 10 was measured using a four-terminal type resistivity meter (manufactured by Mitsubishi Chemical Corporation), all of the values were 20 × 10 ⁶ Ω / square or more. And it exceeded the measurement limit of the resistivity meter.
(Comparative Example 1)
A sol obtained by hydrolysis of tetraethoxysilane and the ITO fine particle aqueous dispersion used in Example 1 were mixed to obtain a liquid composition. This liquid composition was applied onto a glass plate by spin coating, dried at room temperature, and further dried in a drying oven at 250 ° C. for 10 minutes. Subsequently, the glass plate with a heat ray shielding film was heated in a baking furnace at 720 ° C. for 120 seconds. It can be confirmed that the ITO fine particles were deteriorated by the value of T1500. The film formed by the sol-gel method is glassy but has a high porosity and is not dense.
(Comparative Example 2)
A liquid composition was obtained by mixing the commercially available ethyl silicate hydrolyzate (HAS10, manufactured by Colcoat Co.) and the ITO fine particle aqueous dispersion used in Example 9. This liquid composition was applied by flow coating onto the glass plate used in Example 9, and dried at room temperature to obtain a glass plate with a heat shielding film.
(Comparative Example 3)
The glass plate with a heat shielding film obtained in the same manner as in Comparative Example 2 was further heated in a drying furnace at 250 ° C. for 1 hour. Comparing Comparative Examples 2 and 3, it can be confirmed that T1500 increased by 6% by heating at 250 ° C. If the film is not dense, the ITO fine particles deteriorate even at this temperature.
[Relationship between heat treatment temperature and ITO fine particle properties]

From the above, it was confirmed that when the heat shielding film of the present invention is heat-treated, the heat ray shielding ability of the ITO fine particles may be improved. Therefore, in order to clarify the relationship between the improvement and the temperature, a glass plate with a heat shielding film produced in the same manner as in the above example under the conditions shown in Table 1 was placed in a furnace set at 500 ° C. The substrate was left until the substrate temperature reached a predetermined temperature (250, 300, 350, 400 ° C.), and then T1500 was measured. The heating up to 250 ° C. required 70 seconds, and 400 ° C. required 277 seconds. The results are shown in FIG.
T1500 slightly exceeded (16%) the value from drying at room temperature (15%) by heating to 250 ° C. However, heating up to 300 ° C. was 15%, which is the same as room temperature, 12% at 350 ° C., 11% at 400 ° C., and lower than the value at room temperature at heating above 350 ° C. The influence of the drying temperature on Ya, Tg, and haze ratio was 1% or less.
(Comparative Example 4)
For comparison, a change in T1500 depending on the drying temperature was measured for a glass plate on which a film was formed only from the ITO fine particle aqueous dispersion. The results are shown in FIG. As shown in FIG. 6, the heat ray shielding ability of the ITO fine particles was lowered by heating in the air at 100 ° C. or higher.
Even in the heat shielding film according to the present invention, when heated at about 100 to 250 ° C., the ITO fine particles dispersed in the outermost layer of the film are likely to deteriorate. However, as is apparent from FIG. 5, in the heat shielding film according to the present invention, this deterioration is suppressed to such a degree that it can be sufficiently canceled by the effect of improving the properties of the ITO fine particles by heating at 350 ° C. or higher.

  As described above, according to the present invention, a heat shielding plate provided with heat shielding properties by ITO fine particles is provided. The heat shielding film according to the present invention maintains a high oxygen shielding ability even if it is formed thick in a single film formation step in the atmosphere, and is extremely suitable for maintaining and enhancing the heat ray shielding ability by ITO fine particles. By utilizing this oxygen shielding ability, the heat shielding property of the heat shielding plate can be maintained even when heated to a high temperature. The heat shielding plate provided by the present invention has a great utility value especially as a window glass for vehicles and buildings.

Claims (20)

A substrate, and a heat shielding film formed on the substrate,
The heat shielding plate, wherein the heat shielding film contains silicon oxide, at least two alkali metal oxides, and ITO fine particles. The substrate is a glass plate;
The heat shielding film has an oxygen shielding ability, and the oxygen shielding ability prevents a light transmittance at a wavelength of 1500 nm from exceeding 3% when the heat shielding plate is left in an atmosphere of 250 ° C. for 60 minutes. The heat shielding plate according to claim 1, wherein deterioration of the ITO fine particles is suppressed. The heat shielding plate according to claim 1, wherein the thickness of the heat shielding film is more than 0.3 μm and not more than 3 μm. The heat shielding plate according to claim 1, wherein a surface resistance value of the heat shielding film is 10 ⁶ Ω / square or more. 2. The heat shielding film according to claim 1, comprising 30 to 70% of the silicon oxide, 5 to 30% of the alkali metal oxide, and 1 to 50% of the ITO fine particles, expressed in mass%. Heat shield plate. The heat shielding plate according to claim 1, wherein the at least two alkali metal oxides include sodium oxide and at least one selected from lithium oxide and potassium oxide. The heat shielding plate according to claim 6, wherein the at least two alkali metal oxides include sodium oxide and lithium oxide. The heat shielding plate according to claim 7, wherein a mass of the lithium oxide is 33 to 90% of a mass of the at least two kinds of alkali metal oxides. The heat shielding plate according to claim 8, wherein a mass of the lithium oxide is 60 to 90% of a mass of the at least two kinds of alkali metal oxides. The substrate includes a glass plate;
The heat shielding plate according to claim 1, wherein the visible light transmittance is 70% or more, the solar radiation transmittance is 50% or less, and the light transmittance at a wavelength of 1500 nm is 20% or less. The substrate includes a glass plate;
The heat shielding plate according to claim 1, wherein the haze ratio is 5% or less. The substrate includes a glass plate;
The heat shielding plate according to claim 1, wherein the glass plate is subjected to at least one treatment selected from a bending treatment and a strengthening treatment. A laminated glass comprising the heat shielding plate according to claim 1. A manufacturing method of a heat shielding plate including a substrate and a heat shielding film formed on the substrate,
On the substrate, a liquid composition containing at least two kinds of alkali silicates, a solvent and ITO fine particles is applied,
The manufacturing method of the heat shielding board which forms a heat shielding film by removing the said solvent from the said liquid composition. The manufacturing method of the heat shielding board of Claim 14 which apply | coats the said liquid composition so that the film thickness of the said heat shielding film may be more than 0.3 micrometer and 3 micrometers or less. The substrate includes a glass plate;
The method for manufacturing a heat shielding plate according to claim 14, further comprising a step of performing at least one treatment selected from a strengthening treatment and a bending treatment on the glass plate after forming the heat shielding film. The substrate includes a glass plate;
After forming the heat shielding film, heating the heat shielding plate reduces at least one selected from the light transmittance and the solar radiation transmittance at a wavelength of 1500 nm of the heat shielding plate as compared to before heating. The manufacturing method of the heat shielding board of Claim 14. A liquid composition for forming a heat shielding film, comprising at least two types of alkali silicate, a solvent, and ITO fine particles. The liquid composition according to claim 18, further comprising silicon oxide fine particles. The liquid according to claim 18, which contains 30 to 70% converted silicon oxide, 5 to 30% converted alkali metal oxide, and 1 to 50% ITO fine particles expressed as mass% in terms of solid content. Composition.

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