JP5703855B2 - Near-infrared reflective film, method for producing near-infrared reflective film, and near-infrared reflector - Google Patents

Description

  The present invention relates to a near-infrared reflective film excellent in near-infrared reflectivity, visible light transmittance and durability (film flexibility), a method for producing a near-infrared reflective film, and a near-red color provided with a near-infrared reflective film It relates to an external reflector.

  In recent years, as part of energy conservation measures, from the viewpoint of reducing the load on cooling equipment, there has been an increasing demand for a near-infrared reflective film that can be attached to a window glass of a building or vehicle to block the transmission of solar heat rays. Yes.

  As a method for forming a near-infrared reflective film, a laminate unit comprising a structure in which a high refractive index layer and a low refractive index layer are alternately laminated is formed by a dry film forming method such as a vapor deposition method or a sputtering method. There has been proposed a method of forming the film by using. However, in the dry film forming method, the vacuum apparatus used for the formation becomes large, the manufacturing cost increases, the enlargement of the area is difficult, and the applicable base material is limited to a heat resistant material. I have a problem.

  In recent years, in place of the dry film-forming method having the above-described problems, a method for forming a near-infrared reflective film using a wet coating method has been actively studied.

  For example, a high refractive index layer coating liquid in which a metal oxide, a thermosetting silicone resin containing metal compound fine particles, an ultraviolet curable acrylic resin, etc. are dispersed in an organic solvent is applied to a substrate by a wet coating method using a bar coater. It is composed of a method for forming a transparent laminate by coating on the surface (for example, see Patent Document 1), a rutile type titanium oxide, a heterocyclic nitrogen compound (for example, pyridine), an ultraviolet curable binder, and an organic solvent. A method for forming a transparent laminate by applying a composition for forming a high refractive index coating film on a substrate by a wet coating method using a bar coater (for example, see Patent Document 2) is disclosed.

  On the other hand, a method of alternately laminating methanol dispersion slurry of spherical rutile-type titanium oxide particles and methanol silica sol (see, for example, Patent Document 3) is also disclosed.

JP-A-8-110401 JP 2004-123766 A Japanese Patent Laid-Open No. 2003-266577

  However, in the methods disclosed in Patent Document 1 and Patent Document 2, since the medium of the coating liquid for forming a high refractive index layer is mainly formed of an organic solvent, a large amount is required during the formation of the high refractive index layer and drying. As a result, the organic solvent is scattered, which has environmental problems. Furthermore, in the method disclosed above, the high refractive index layer is formed using an ultraviolet curable binder or a thermosetting binder as a binder, and then cured by ultraviolet rays or heat. ing. Furthermore, since a slurry in which rutile titanium oxide particles are dispersed in an organic solvent using a surface treatment agent is used, the particle size distribution of the titanium particles is wide, and the refractive index in the coating film becomes uneven in the plane. There was a problem that the coating film was discolored in the process of long-term storage due to the problem and the influence of the surface treatment agent.

  Further, in the method described in Patent Document 3, since the film is formed by binding particles, the resulting film is brittle, and in the high refractive index layer formed by binding rutile titanium oxide particles, There is a problem that the haze is high due to voids generated at the particle interface.

  The present invention has been made in view of the above problems, and its purpose is that it can be manufactured using a water-based coating solution for forming a refractive index, the manufacturing cost is low, the area can be increased, and the film flexibility is excellent. An object of the present invention is to provide a near-infrared reflective film having a high visible light transmittance, excellent near-infrared reflectivity and durability, a method for producing the same, and a near-infrared reflector provided with the near-infrared reflective film.

  The above object of the present invention is achieved by the following configurations.

  1. The substrate has at least one unit composed of a high refractive index layer and a low refractive index layer, and the refractive index difference between the high refractive index layer and the low refractive index layer is 0.1 or more. In the near-infrared reflective film, at least one of the high refractive index layer and the low refractive index layer contains metal oxide particles, gelatin or collagen peptide, and an acid or a salt thereof, and the film surface pH of the unit Is a near-infrared reflective film, characterized in that it is 4.0 or more and 6.0 or less.

  2. 2. The near-infrared reflective film as described in 1 above, wherein the acid or a salt thereof is a salt of a carboxylic acid having a molecular weight of 300 or less and an alkali metal or an alkaline earth metal.

  3. At least one of the high refractive index layer and the low refractive index layer is 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, and 2) a high molecular weight gelatin having a weight average molecular weight of 100,000 or more. 3. The near-infrared reflective film as described in 1 or 2 above, comprising:

  4). The high refractive index layer contains metal oxide particles, and the metal oxide particles are rutile titanium oxide particles having a volume average particle size of 100 nm or less. The near-infrared reflective film as described.

  5. At least one of the high refractive index layer and the low refractive index layer contains at least one water-soluble polymer selected from celluloses, thickening polysaccharides and polymers having a reactive functional group. 5. The near-infrared reflective film according to any one of 1 to 4 above.

  6). The substrate has at least one unit composed of a high refractive index layer and a low refractive index layer, and a difference in refractive index between the high refractive index layer and the low refractive index layer is 0.1 or more. In the method for producing a near-infrared reflective film for producing a near-infrared reflective film, at least one of the high refractive index layer and the low refractive index layer includes at least metal oxide particles, gelatin or collagen peptide, and acid or A method for producing a near-infrared reflective film, characterized in that it is formed using an aqueous coating solution containing the salt, and the film surface pH of the formed unit is 4.0 or more and 6.0 or less.

  7). 7. The method for producing a near-infrared reflective film as described in 6 above, wherein the acid or a salt thereof is a salt of a carboxylic acid having a molecular weight of 300 or less and an alkali metal or an alkaline earth metal.

  8). 8. The near red as described in 6 or 7 above, wherein the aqueous coating solution forming at least one of the high refractive index layer and the low refractive index layer has a pH of 3.8 or more and 5.8 or less. A method for producing an external reflection film.

  9. The gelatin or collagen peptide contained in the aqueous coating solution forming at least one of the high refractive index layer and the low refractive index layer is 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, 2) The method for producing a near-infrared reflective film as described in any one of 6 to 8 above, wherein the gelatin is a high molecular weight gelatin having a weight average molecular weight of 100,000 or more.

  10. An aqueous coating solution for forming at least one of the high refractive index layer and the low refractive index layer is formed on the surface of the metal oxide particles, and 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less. 10. The method for producing a near-infrared reflective film as described in 9 above, which is prepared by adding 2) a high molecular weight gelatin having a weight average molecular weight of 100,000 or more after coating.

  11. 6. A near-infrared reflector having the near-infrared reflective film according to any one of 1 to 5 on at least one surface side of a substrate.

  According to the present invention, a water-based refractive index forming coating solution is used, the manufacturing cost is low, the area can be increased, the film flexibility is excellent, the visible light transmittance is high, and the near-infrared reflectivity and durability are achieved. An excellent near-infrared reflective film, a production method thereof, and a near-infrared reflector provided with the near-infrared reflective film could be provided.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor has at least one unit composed of a high refractive index layer and a low refractive index layer on a base material. In the near-infrared reflective film having a refractive index difference of 0.1 or more with respect to the low refractive index layer, at least one of the high refractive index layer and the low refractive index layer includes metal oxide particles, gelatin or collagen peptide, And an acid or a salt thereof, and the near-infrared reflective film is characterized in that the unit has a film surface pH of 4.0 or more and 6.0 or less. It is possible to realize a near-infrared reflective film with excellent film flexibility, high visible light transmittance, excellent near-infrared reflectivity and durability, and a high refractive index layer and low refraction on the substrate. Having at least one unit composed of an index layer and the high refraction In the method for producing a near-infrared reflective film in which a difference in refractive index between the layer and the low-refractive index layer is 0.1 or more, at least one of the high-refractive index layer and the low-refractive index layer One layer is formed using an aqueous coating solution containing at least metal oxide particles, gelatin or collagen peptide, and an acid or a salt thereof, and the formed film has a film surface pH of 4.0 or more and 6.0 or less. The near-infrared reflective film manufacturing method is characterized by the fact that it uses a water-based coating solution for forming a refractive index, can be manufactured at low cost, has a large area, has excellent film flexibility, and transmits visible light. It has been found that a method for producing a near-infrared reflective film capable of obtaining a near-infrared reflective film having a high rate and excellent near-infrared reflectivity and durability can be realized, and the present invention has been achieved.

  That is, in a conventional method for producing a near-infrared reflective film, a method for forming a high refractive index layer in which metal oxide particles are dispersed in a resin binder is mainly a high refractive index layer using an organic solvent as a medium. Although it was formed by the coating solution, it had a problem with the uniformity of the coating film or environmental suitability.

  In the conventional method, the reason why the high refractive index layer coating solution containing resin polymer and metal oxide particles, for example, titanium oxide particles has not been applied as an aqueous coating solution is that an aqueous high refractive index layer coating solution is used. When the coating film is formed by using the dry air, ripples (this phenomenon is also referred to as “blowing unevenness”) occur on the surface of the coating film until the coating film solidifies during the drying process. It is thought that the actual situation is that the flatness of the titanium oxide particles is impaired, or that it is difficult to stably disperse the titanium oxide particles in the water-soluble polymer solution that is an aqueous medium.

  As a result of diligent investigations on the above problems, the present inventor, as a coating liquid for forming an aqueous refractive index control layer (unit composed of a high refractive index layer and a low refractive index layer), metal oxide particles, gelatin or By using a coating solution containing a collagen peptide and an acid or a salt thereof, the metal oxide, which is the main component for controlling the refractive index, can be stably dispersed at a high concentration in an aqueous medium. As well as being able to ensure thickening in a low-temperature environment as a coating solution, the coating film formed at the time of coating and drying is blown and does not cause unevenness, and a uniform coating film is obtained by a manufacturing method excellent in environmental suitability. In addition, the quality of the formed coating film was such that a near-infrared reflective film excellent in optical property quality and storage stability could be obtained.

  In the present invention, a high refractive index layer and a low refractive index layer are formed by using a coating solution containing metal oxide particles, gelatin or collagen peptide and an acid or a salt thereof, and coating and drying. It is necessary to form a coating film so that the film surface pH of the unit is 4.0 or more and 6.0 or less.

  As a more preferred embodiment in the present invention, as the near-infrared reflective film, at least one of the high refractive index layer and the low refractive index layer according to the present invention is 1) a low molecular weight having a weight average molecular weight of 50,000 or less. Containing gelatin or collagen peptide and 2) high molecular weight gelatin having a weight average molecular weight of 100,000 or more, or the high refractive index layer according to the present invention contains metal oxide particles, Rutile-type titanium oxide particles having a volume average particle size of 100 nm or less are preferable.

  Further, as a more preferable embodiment as a method for producing a near-infrared reflective film, the pH of the aqueous coating solution for forming at least one of the high refractive index layer and the low refractive index layer according to the present invention is 3.8 or more, The gelatin or collagen peptide contained in the aqueous coating solution forming at least one of the high refractive index layer and the low refractive index layer according to the present invention is 1) The weight average molecular weight is 50,000. A low molecular weight gelatin or collagen peptide which is the following: 2) a high molecular weight gelatin having a weight average molecular weight of 100,000 or more, an aqueous system forming at least one of the high refractive index layer and the low refractive index layer according to the present invention After coating the surface of the metal oxide particles with 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, 2) a weight average molecular weight of 100,000 or more It is a preferred embodiment which is prepared by adding a high molecular weight gelatin.

  The present inventors presume as follows as a technical mechanism by which the objective effect of this invention is acquired by taking said each structure prescribed | regulated by this invention.

  In the present invention, the film surface pH of the unit film surface is controlled to be 4.0 or more and 6.0 or less using an acid or a salt thereof. At this time, when the film surface pH of the unit film surface exceeds 6.0, in many cases, the pH of the coating solution used for forming the refractive index layer exceeds 5.8. In this way, in a coating solution having a pH value exceeding 5.8, the pH environment is close to the isoelectric point of gelatin or collagen peptide, and the repulsive force of the molecular chain constituting gelatin or collagen peptide is reduced. The protective colloid properties for the oxide particles are lowered, and the stable dispersibility of the metal oxide particles cannot be maintained. As a result, the metal oxide particles are aggregated, and the transparency of the refractive index layer coating film is lowered. In addition, the aggregation of the metal oxide particles causes a decrease in interlayer mixing between the high refractive index layer and the low refractive index layer, and as a result, the heat ray acquisition rate (near infrared reflectivity) deteriorates. become.

  On the other hand, when the film surface pH of the film surface of the unit is less than 4.0, the pH of the coating solution used for forming the refractive index layer is often less than 3.8. In a coating solution having a pH value of less than 3.8, the mixing property of titanium oxide particles and silicon oxide particles is deteriorated, and the haze of the formed refractive index layer is lowered. Moreover, when the pH of the coating solution becomes too low, the low temperature setting property at the time of coating film formation is lowered, and the interlayer mixing property between the high refractive index layer and the low refractive index layer is deteriorated. The external reflectivity will decrease. In addition, if the pH of the coating solution becomes too low, the reactivity of the hardener to gelatin or collagen peptide decreases, resulting in insufficient film hardness, and durability of the coating film when stored in a high temperature and high humidity environment Decreases.

  Hereinafter, the component of the near-infrared reflective film of this invention, the form for implementing this invention, etc. are demonstrated in detail.

《Near-infrared reflective film》
The near-infrared reflective film of the present invention has at least one unit composed of a high refractive index layer and a low refractive index layer on a substrate, and the adjacent high refractive index layer and low refractive index layer One of the characteristics is that the difference in refractive index is 0.1 or more. Further, as the optical characteristics of the near-infrared reflective film of the present invention, the transmittance in the visible light region shown in JIS R3106-1998 is 50% or more, and the reflectance is 50% in the wavelength region of 900 nm to 1400 nm. It is preferable to have a region exceeding.

  In general, in the near-infrared reflective film, it is preferable to design a large difference in refractive index between the high refractive index layer and the low refractive index layer from the viewpoint of increasing the infrared reflectance with a small number of layers, In the present invention, in at least one unit composed of a high refractive index layer and a low refractive index layer, a difference in refractive index between the adjacent high refractive index layer and low refractive index layer is 0.1 or more. It is characterized, Preferably it is 0.3 or more, More preferably, it is 0.4 or more.

  The reflectance in the specific wavelength region is determined by the difference in refractive index between two adjacent layers and the number of stacked layers, and the larger the difference in refractive index, the same reflectance can be obtained with a smaller number of layers. The refractive index difference and the required number of layers can be calculated using commercially available optical design software. For example, in order to obtain an infrared reflectance of 90% or more, if the difference in refractive index is less than 0.1, it is necessary to laminate 20 or more layers, which not only lowers productivity but also scatters at the lamination interface. Becomes larger, the transparency is lowered, and it becomes very difficult to manufacture without failure. From the viewpoint of improving reflectivity and reducing the number of layers, there is no upper limit to the difference in refractive index, but the limit is substantially about 1.40.

  Next, the basic configuration outline of the high refractive index layer and the low refractive index layer in the near-infrared reflective film of the present invention will be described.

  In the near-infrared reflective film of the present invention, it is sufficient that at least one unit composed of a high refractive index layer and a low refractive index layer is laminated on a substrate, but a preferable high refractive index layer and low As the number of refractive index layers, from the above viewpoint, the range of the total number of layers is 100 layers or less, that is, 50 units or less, more preferably 40 layers (20 units) or less, and even more preferably 20 Layer (10 units) or less.

  In the near-infrared reflective film of the present invention, the difference in refractive index between the adjacent high refractive index layer and low refractive index layer is 0.1 or more. When there are a plurality of refractive index layers as described above, it is preferable that all refractive index layers satisfy the requirements defined in the present invention. However, the outermost layer and the lowermost layer may be configured outside the requirements defined in the present invention.

  Moreover, in the near-infrared reflective film of this invention, as a preferable refractive index of a high refractive index layer, it is 1.80-2.50, More preferably, it is 1.90-2.20. Moreover, as a preferable refractive index of a low-refractive-index layer, it is 1.10-1.60, More preferably, it is 1.30-1.50.

  In the near-infrared reflective film of the present invention, it is preferable to add rutile type titanium oxide having a volume average particle size of 100 nm or less as a metal oxide to the high refractive index layer, and the metal oxide and the high refractive index layer. It is more preferable to add to both layers of the low refractive index layer. In the present invention, the content of the metal oxide in the high refractive index layer is preferably 15% by mass or more and 50% by mass or less, more preferably 20% by mass or more, based on the total mass of the high refractive index layer. It is 40 mass% or less.

  In addition, at least one of the high refractive index layer and the low refractive index layer according to the present invention is gelatin or collagen peptide, and the weight average molecular weight is 100,000 or less and the weight average molecular weight is 100,000 or less. It is one of the preferred embodiments that the above high molecular weight gelatin is contained. In the present invention, the content of low molecular weight gelatin or collagen peptide in the high refractive index layer or the low refractive index layer is 10% by mass or more and 50% by mass or less of the total mass of the high refractive index layer or the low refractive index layer. It is preferable that the content is 15% by mass or more and 30% by mass or less. Further, the content of high molecular weight gelatin in the high refractive index layer or the low refractive index layer is preferably 10% by mass or more and 50% by mass or less of the total mass of the high refractive index layer or the low refractive index layer. More preferably, it is 20 mass% or more and 40 mass% or less.

  In the present invention, each refractive index of the high refractive index layer and the low refractive index layer can be determined according to the following method.

  A sample in which a refractive index layer to be measured for refractive index is coated as a single layer on a substrate is prepared, and the sample is cut into 10 cm × 10 cm, and then the refractive index is determined according to the following method. Using a U-4000 type (manufactured by Hitachi, Ltd.) as a spectrophotometer, the surface opposite to the measurement surface of the sample (back surface) is roughened and then subjected to light absorption treatment with a black spray. Light reflection on the back surface is prevented, and the reflectance in the visible light region (400 nm to 700 nm) is measured at 25 points under the condition of regular reflection at 5 degrees, the average value is obtained, and this is used as the refractive index of the refractive index layer. Ask.

(High refractive index layer)
As one embodiment of the high refractive index layer according to the present invention, it is preferable to contain metal oxide particles, gelatin or collagen peptide, and acid or a salt thereof, and 1) the weight average molecular weight is 50,000 or less. It preferably contains low molecular weight gelatin or collagen peptide, 2) high molecular weight gelatin having a weight average molecular weight of 100,000 or more, 3) metal oxide particles, and 4) acid or a salt thereof.

(Metal oxide particles)
As the metal oxide particles used in the high refractive index layer according to the present invention, it is preferable to use metal oxide particles having a refractive index of 2.0 or more and a volume average particle size of 100 nm or less, such as zirconium oxide, Examples thereof include cerium oxide and titanium oxide, but it is particularly preferable to use rutile type titanium oxide particles having a volume average particle size of 100 nm or less.

<Rutyl type titanium oxide>
In general, titanium oxide particles are often used in a surface-treated state for the purpose of suppressing photocatalytic activity on the particle surface and improving dispersibility in a solvent or the like. For example, titanium oxide particles Known are those in which the surface is covered with a coating layer made of silica and the particle surface is negatively charged, and in which the coating layer made of aluminum oxide is formed and the surface is positively charged at pH 8-10. .

  In the present invention, the metal oxide particles are preferably rutile (tetragonal) titanium oxide particles having a volume average particle diameter of 100 nm or less.

  The volume average particle diameter of the rutile-type titanium oxide particles according to the present invention is preferably 100 nm or less, more preferably 4 nm or more and 50 nm or less, and further preferably 4 nm or more and 30 nm or less. A volume average particle diameter of 100 nm or less is preferable from the viewpoint of low haze and excellent visible light transmittance. Titanium oxide particles having a volume average particle diameter exceeding 100 nm are not limited to be used in the high refractive index layer, not limited to the present invention.

The volume average particle diameter of the rutile-type titanium oxide particles according to the present invention means that the particles themselves or particles appearing on the cross section or surface of the refractive index layer are observed with an electron microscope, and the particle diameter of 1,000 arbitrary particles is determined. measured in a population of each of _{d 1, d 2 ··· d i} · d respectively particles _n 1 having a particle size of _{k, n 2 ··· n i ·} n k pieces existing metal oxide particles, particles When the surface area per piece is a _i and the volume is v _i , the volume average particle size mv = weighted by the volume represented by {Σ (v _i · d _i )} / {Σ (v _i )}. Average particle size.

  On the other hand, the average particle size of the primary particles or secondary particles dispersed in the medium is an average particle size weighted by the volume measured by the method shown below. Laser diffraction / scattering method, dynamic light scattering method It can be calculated as an average particle size weighted by the volume measured by the above method.

  Furthermore, the titanium oxide particles according to the present invention are preferably monodispersed. The monodispersion here means that the monodispersity obtained by the following formula is 40% or less. The particles are more preferably 30% or less, and particularly preferably 0.1 to 20%.

Monodispersity = (standard deviation of particle size) / (average value of particle size) × 100
<Method for producing rutile type titanium oxide sol>
In the method for producing a near-infrared reflective film of the present invention, when preparing a water-based high refractive index layer coating solution, the rutile-type titanium oxide has a pH of 1.0 or more and 3.0 or less, and the titanium particles It is preferable to use an aqueous titanium oxide sol having a positive zeta potential.

  In general, titanium oxide particles are often used in a state in which surface treatment is performed for the purpose of suppressing the photocatalytic activity on the particle surface or improving dispersibility in a solvent or the like. It is known that the particle surface is negatively charged, or the surface of the particle is positively charged at pH 8 to 10 where the aluminum oxide coating layer is formed. In this case, it is preferable to use an aqueous sol of rutile-type titanium oxide that has a pH of 1.0 to 3.0 and has a positive zeta potential without any surface treatment.

  Examples of a method for preparing a rutile type titanium oxide sol that can be used in the present invention include, for example, JP-A-63-17221, JP-A-7-819, JP-A-9-165218, and JP-A-11-43327. Reference can be made to the methods described in JP-A 63-17221, JP-A 7-819, JP-A 9-165218, JP-A 11-43327, and the like.

  In addition, as another method for producing the rutile type titanium oxide according to the present invention, for example, “Titanium oxide-physical properties and applied technology” Manabu Seino p255-258 (2000) Gihodo Publishing Co., Ltd. or WO2007 / 039953 The manufacturing method of the step (2) described in paragraph Nos. 0011 to 0023 can be referred to.

  In the production method according to the above step (2), titanium dioxide hydrate is treated with at least one basic compound selected from the group consisting of alkali metal hydroxides or alkaline earth metal hydroxides. After the step (1), the titanium dioxide dispersion obtained comprises a step (2) of treating with a carboxylic acid group-containing compound and an inorganic acid. In the present invention, an aqueous sol of rutile-type titanium oxide having a pH adjusted to 1.0 to 3.0 with the inorganic acid obtained in the step (2) can be used.

(Low refractive index layer)
In this invention, it has a low refractive index layer whose refractive index is lower by at least 0.1 or more than the above-mentioned high refractive index layer. The low refractive index layer preferably has a refractive index of 1.6 or less. Furthermore, it is 1.30-1.50.

  In the low refractive index layer according to the present invention, a material in which metal oxide particles are dispersed in a water-soluble polymer is used. The water-soluble polymer compound used in the low refractive index layer is the same as the water-soluble polymer described later that can be used in the high refractive index layer, that is, celluloses, thickening polysaccharides, reactive functional groups. Polymers having various properties and various gelatins can be used. The water-soluble polymer used in the high-refractive index layer and the low-refractive index layer may be the same or different, but the same is preferable in carrying out simultaneous multilayer coating.

  In the low refractive index layer according to the present invention, it is preferable to use silicon dioxide as the metal oxide particles, and it is particularly preferable to use acidic colloidal silica sol.

  In the present invention, the silicon dioxide preferably has a volume average particle size of 100 nm or less. The volume average particle diameter of silicon dioxide according to the present invention can be measured by the same method as the measurement of the volume average particle diameter of the rutile titanium oxide particles.

  In order to satisfy the preferred volume average particle size in the unit of the present invention, the average particle size of primary particles of silicon dioxide dispersed in the state of primary particles (particle size in the dispersion state before coating) is: The thing of 20 nm or less is preferable, More preferably, it is 10 nm or less. In addition, the average particle size of the secondary particles is preferably 30 nm or less from the viewpoint of low haze and excellent visible light transmittance.

  The average particle diameter of the metal oxide according to the present invention is such that the particle itself or particles appearing on the cross section or surface of the refractive index layer are observed with an electron microscope, and the particle diameter of 1,000 arbitrary particles is measured. It is obtained as a simple average value (number average). Here, the particle diameter of each particle is represented by a diameter assuming a circle equal to the projected area.

  Next, details of main components of the high refractive index layer and the low refractive index layer according to the present invention will be further described.

[Gelatin, collagen peptide]
In the present invention, at least one of the high refractive index layer and the low refractive index layer according to the present invention is characterized by containing gelatin or a collagen peptide together with metal oxide particles and an acid or a salt thereof, more preferably And at least one of the high refractive index layer and the low refractive index layer according to the present invention is 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, and 2) a high weight average molecular weight of 100,000 or more. Containing molecular weight gelatin.

  As the gelatin applicable to the present invention, various gelatins that have been widely used in the field of silver halide photographic light-sensitive materials can be applied. For example, in addition to acid-processed gelatin and alkali-processed gelatin, production of gelatin is possible. Enzyme-treated gelatin and gelatin derivatives that undergo enzyme treatment in the process, that is, modified by treatment with a reagent that has an amino group, imino group, hydroxyl group, carboxyl group as a functional group in the molecule and a group obtained by reaction with it. You may have done. The general method for producing gelatin is well known and is described, for example, in T.W. H. James: The Theory of Photographic Process 4th. ed. Reference can be made to descriptions such as 1977 (Machillan) 55, Science Photo Handbook (above) 72-75 (Maruzen), Fundamentals of Photographic Engineering-Silver Salt Photographs 119-124 (Corona). Also, Research Disclosure Magazine Vol. 176, No. And gelatin described in Section IX of 17643 (December, 1978).

<Low molecular weight gelatin>
The low molecular weight gelatin or collagen peptide according to the present invention preferably has a weight average molecular weight of 50,000 or less, and further, the content of a high molecular weight gelatin component having a molecular weight of 100,000 or more is 1.0% by mass or less. Is preferred.

  The collagen peptide as used in the present invention is defined as a protein obtained by subjecting gelatin to low molecular weight treatment so that sol-gel change is not expressed.

  The low molecular weight gelatin or collagen peptide according to the present invention preferably has a weight average molecular weight of 50,000 or less, more preferably 2,000 to 30,000, particularly preferably 5,000 to 25, 000.

  The weight average molecular weight of low molecular weight gelatin or collagen peptide can be measured using gel filtration chromatography. Low molecular weight gelatin or collagen peptides are hydrolyzed by adding gelatin-degrading enzyme to an aqueous solution of high molecular weight gelatin having a weight average molecular weight of about 100,000, or hydrolyzing by adding acid or alkali, It can be obtained by thermal decomposition by heating under or under pressure, decomposition by ultrasonic irradiation, or a combination of these methods.

  More specifically, the low molecular weight gelatin and collagen peptide according to the present invention can be prepared as follows.

  As a commonly used method, gelatin molecules are enzymatically decomposed by dissolving gelatin having a weight average molecular weight of 100,000 or more in water and adding gelatinolytic enzyme. For this method, see R.A. J. et al. Cox. Reference can be made to the description of Photographic Gelatin II, Academic Press, London, 1976, P233-251, P335-P346. In this case, since the binding position where the enzyme decomposes is determined, low molecular weight gelatin having a relatively narrow molecular weight distribution can be obtained, which is preferable. In this case, the longer the enzymatic decomposition time, the lower the molecular weight.

  In addition, there is a method of heating in a low pH (pH 1 to 3) or high pH (pH 10 to 12) atmosphere for hydrolysis. When the weight average molecular weight exceeds 50,000, the effect of the present invention is reduced. If the weight average molecular weight is less than 2000, there are difficulties in the production of gelatin and collagen peptides.

  In the low molecular gelatin and collagen peptide according to the present invention, the high molecular weight gelatin having a weight average molecular weight of 100,000 or more used as a raw material is sufficiently decomposed in the above low molecular gelatin or collagen peptide preparation step, and the content thereof is determined. Appropriately set conditions such as the type and amount of gelatinolytic enzyme, temperature and time during enzymatic degradation, so that the enzymatic degradation of high molecular weight gelatin molecules is optimally performed so that the amount is 1.0% by mass or less. Is preferred.

<High molecular weight gelatin>
In the present invention, at least one of the high refractive index layer and the low refractive index layer preferably contains a high molecular weight gelatin having a weight average molecular weight of 100,000 or more. The weight average molecular weight of the high molecular weight gelatin is 100,000. As mentioned above, it is more preferable that it exists in the range of 200,000 or less.

  In the present invention, the weight average molecular weight of the high molecular weight gelatin used can be measured, for example, by gel permeation chromatography. The molecular weight distribution and the weight average molecular weight of gelatin can also be measured by a gel permeation chromatograph method (GPC method) which is a generally known method.

  Regarding the molecular weight of gelatin, see D.C. Lory and M.M. Vedrines, Proceedings of the 4th IAG Conference, Sept. 1983, p. 35, as described in Takashi Ohno, Hiroyuki Kobayashi, Shinya Mizusawa, Journal of the Japan Photography Society, 47, 237 (1984), etc., the α component (molecular weight of about 100,000), which is a structural unit of collagen, and its dimer In general, it comprises a β-component, a γ-component that is a trimer, a high-molecular amphoteric component that is a monomer, and a low-molecular-weight component obtained by irregularly cutting these components.

  As the high molecular weight gelatin having a weight average molecular weight of 100,000 or more according to the present invention, among the above components, α component (molecular weight of about 100,000), which is a structural unit of collagen, and dimer and trimer thereof. Gelatin mainly composed of β component and γ component.

  The measurement of gelatin molecular weight distribution is described in the above-mentioned documents and JP-A-60-80838, JP-A-62-87952, JP-A-62-265645, JP-A-62-279329, and JP-A-64-46742. The gel permeation chromatographic method is used.

  In the present invention, the ratio of each molecular weight component of gelatin can be determined by the GPC method under the following conditions.

a) Column: Asahipak, GS-620 (Asahi Kasei Kogyo Co., Ltd.)
Two connected in series Column temperature 50 ℃
b) Eluent: Equal volume mixed solution of 0.1 mol / L KH ₂ PO ₄ and 0.1 mol / L Na ₂ HPO ₄ pH 6.8 Flow rate 1.0 ml / min
c) Sample: 0.2% eluent solution of gelatin Injection volume 100 μl
d) Detection: UV absorption spectrophotometer (UV wavelength 230 nm)
Looking at the change in absorption at 230 nm due to the retention time, first the peak at the exclusion limit appears, then the peaks due to the γ component, β component, and α component of gelatin in turn, and as the retention time becomes longer, The shape will gradually decay. The molecular weight can be determined from the retention time of the outflow curve calibrated with a standard sample.

  The α component is composed of a polypeptide chain having a molecular weight of about 100,000. Gelatin such as α chain dimer (β component) and trimer (γ component) is an aggregate of gelatin molecules having various molecular weights. In addition, gelatin having a predetermined weight average molecular weight can be obtained from a gelatin manufacturer.

  Moreover, as a manufacturing method of the high molecular weight gelatin whose weight average molecular weight which concerns on this invention is 100,000 or more, the following method etc. are mentioned, for example.

  1) In the extraction operation during the production of gelatin, an extract in the early stage of extraction (low molecular weight component) is excluded by using an extract in the later stage of extraction.

  2) In the said manufacturing method, process temperature shall be less than 40 degreeC in the process from extraction to drying.

  3) The gelatin is dialyzed in cold water (15 ° C.).

  By using the above methods alone or in combination, a high molecular weight gelatin having a weight average molecular weight of 100,000 or more can be obtained.

  In the present invention, at least one of the high refractive index layer and the low refractive index layer according to the present invention is 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, and 2) a weight average molecular weight of 100,000. Although it is one of the preferable aspects to contain the above high molecular weight gelatin, it is confirmed by the following method whether the high refractive index layer or the low refractive index layer satisfies the requirements defined in the present invention. be able to.

  After isolating the high refractive index layer or low refractive index layer constituting the near-infrared reflective film, after measuring the molecular weight distribution of gelatin by the gel permeation chromatograph method (GPC method), the horizontal axis indicates the molecular weight of gelatin. After plotting the content on the vertical axis and preparing a molecular weight distribution curve, the molecular weight is determined to be 50,000 or less and the maximum peaks of two contents appearing when the molecular weight is 100,000 or more.

[Hardener for gelatin]
In the high refractive index layer coating solution or the low refractive index layer coating solution according to the present invention, after the high refractive index layer or the low refractive index layer is formed, the gelatin coating film is hardened. It can also be added.

  As the hardener that can be used, known compounds conventionally used as hardeners for photographic emulsion layers constituting silver halide photographic light-sensitive materials can be used, such as vinylsulfone compounds and urea-formalin condensation. Products, melanin-formalin condensates, epoxy compounds, aziridine compounds, active olefins, organic hardeners such as isocyanate compounds, and inorganic polyvalent metal salts such as chromium, aluminum and zirconium.

[Acid or its salt]
Next, the acid or salt thereof according to the present invention will be described.

  The present invention is characterized in that at least one of the high refractive index layer and the low refractive index layer according to the present invention contains an acid or a salt thereof together with metal oxide particles and gelatin or a collagen peptide.

  The acid or a salt thereof according to the present invention is particularly preferably an acid that easily volatilizes with moisture and volatilizes without being decomposed at normal pressure. Here, when volatilizing easily, in the manufacturing process of the near-infrared reflective film, after coating the coating liquid on the substrate, with the decrease in the water content of the high refractive index layer coating film or low refractive index layer coating film, It means that the volatility can be confirmed significantly. In the coating and drying process when producing the near-infrared reflective film, the drying temperature can be selected in accordance with desired properties such as the material used and the material of the base material. It is preferable to use an acid exhibiting volatility in the range of. The volatility of the acid can be determined, for example, by performing quantitative analysis of the acid remaining in the near-infrared reflective film.

  Specific examples of the acid that can be used in the present invention include lower fatty acids having 10 or less carbon atoms such as hydrochloric acid, nitric acid, hydrofluoric acid, carbonic acid, and acetic acid. Among these, it is preferable to use carbonic acid, acetic acid, or a salt thereof from the viewpoints of acidity, handleability, and the like.

  In the present invention, the acid is also preferably used in the form of a salt with a cationic compound. Specific examples include salts with alkali metal ions such as sodium ion, potassium ion and lithium ion, salts with alkaline earth metal ions such as magnesium ion, calcium ion and barium ion, aluminum ion, zirconium ion and zinc ion. Salts with metal ions and complex ions containing these metal ions, salts with inorganic or organic ammonium ions such as triethanolammonium ion and pyridinium ion, salts with other organic compounds and polymers having a cationic group, etc. Is mentioned.

  The acid or salt thereof according to the present invention is particularly preferably a salt of a carboxylic acid having a molecular weight of 300 or less and an alkali metal or alkaline earth metal, particularly preferably sodium acetate.

  The acid or salt thereof according to the present invention preferably has a function of increasing the pH value of the coating film formed by drying with respect to the pH value of the coating solution contained in the acid or salt thereof. More preferably, the acid or salt thereof has a function of increasing the film surface pH value by 0.2 or more with respect to the coating solution pH value.

  As the characteristics of the acid or its salt according to the present invention, it is preferable that the film surface pH of the refractive index layer constituting the near-infrared reflective film rises after volatilization of the acid. Those having properties such as low basicity and higher basicity of the cationic compound than acidity of the acid are preferably used. Specific examples of preferred cationic compounds include sodium ion, potassium ion, lithium ion, etc., but various combinations depending on the volatility and acidity of the acid used, the manufacturing process temperature, humidity and manufacturing time of the applied material, etc. Can be used.

[Coating solution pH]
In the method for producing a near-infrared reflective film of the present invention, the pH of the aqueous coating solution forming at least one of the high refractive index layer and the low refractive index layer according to the present invention is 3.8 or more and 5.8 or less. It is preferable that

  In the present invention, the pH of the coating solution refers to the pH of the high refractive index layer coating solution or the low refractive index layer coating solution that is actually coated on the substrate. When a plurality of refractive index layer coating liquids are applied, the pH of the liquid obtained by mixing all the refractive index layer coating liquids is defined as the pH of the refractive index layer coating liquid. Accordingly, when coating is performed by adding some compound by in-line addition, the pH after the in-line addition is set as the pH of the refractive index layer coating solution in the present invention.

[Membrane surface pH]
The present invention is characterized in that the film surface pH in a unit composed of a high refractive index layer and a low refractive index layer is 4.0 or more and 6.0 or less.

  The film surface pH in the unit composed of the high refractive index layer and the low refractive index layer in the present invention can be determined by the following method.

  That is, J. et al. TAPPI paper pulp test method no. According to the method described in No. 49, 50 μl of distilled water is used, and measurement can be performed 30 seconds after the electrode is brought into contact with the wet film surface of the near-infrared reflective layer. Even if the unit composed of the high refractive index layer and the low refractive index layer is one unit, or the case where the unit is composed of two or more units, the final form of the near-infrared reflective film Measurement is performed by applying 50 μl of distilled water to the refractive index layer forming surface. The measurement temperature is 25 ° C. As a specific method for measuring the membrane surface pH, a digital pH meter HM-18B manufactured by Toa Denpa Kogyo Co., Ltd. is used as a measuring device, and after standardizing the pH meter, 50 μl of distilled water is measured with a micropipette and measured. It is dropped on the formation surface of the refractive index layer unit of the near-infrared reflective film, the measurement electrode of the pH meter is lowered perpendicularly to the water drop and placed on the film surface, and the measured value after 30 seconds is taken as the film surface pH. Can be sought.

(Water-soluble polymer)
In the near-infrared reflective film of the present invention, the high refractive index layer or the low refractive index layer preferably contains a water-soluble polymer such as celluloses, thickening polysaccharides and polymers having reactive functional groups. . The water-soluble polymer referred to in the present invention is a temperature at which the water-soluble polymer is most dissolved, and is a G2 glass filter (maximum pores 40 to 50 μm) when dissolved in water at a concentration of 0.5% by mass. The mass of the insoluble matter that is filtered off when filtered is within 50 mass% of the added water-soluble polymer.

<Cellulose>
As the celluloses that can be used in the present invention, a water-soluble cellulose derivative can be preferably used. For example, water-soluble cellulose derivatives such as carboxymethyl cellulose (cellulose carboxymethyl ether), methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose. Examples thereof include cellulose derivatives, carboxymethyl cellulose (cellulose carboxymethyl ether) and carboxyethyl cellulose which are carboxylic acid group-containing celluloses. Other examples include cellulose derivatives such as nitrocellulose, cellulose acetate propionate, cellulose acetate, and cellulose sulfate.

<Thickening polysaccharide>
The thickening polysaccharide that can be used in the present invention is not particularly limited, and examples thereof include generally known natural simple polysaccharides, natural complex polysaccharides, synthetic simple polysaccharides, and synthetic complex polysaccharides. The details of these polysaccharides can be referred to “Biochemical Encyclopedia (2nd edition), Tokyo Chemical Doujinshi”, “Food Industry”, Vol. 31 (1988), p.

  The thickening polysaccharide referred to in the present invention is a polymer of saccharides and has many hydrogen bonding groups in the molecule, and the viscosity at low temperature and the viscosity at high temperature due to the difference in hydrogen bonding force between molecules depending on the temperature. It is a polysaccharide with a large difference in characteristics, and when adding metal oxide fine particles, it causes a viscosity increase that seems to be due to hydrogen bonding with the metal oxide fine particles at a low temperature. When added, it is a polysaccharide that increases its viscosity at 15 ° C. by 1.0 mPa · s or more, preferably 5.0 mPa · s or more, more preferably 10.0 mPa · s or more. Polysaccharides.

  Examples of the thickening polysaccharide applicable to the present invention include galactan (eg, agarose, agaropectin, etc.), galactomannoglycan (eg, locust bean gum, guaran, etc.), xyloglucan (eg, tamarind gum, etc.), Glucomannoglycan (eg, salmon mannan, wood-derived glucomannan, xanthan gum, etc.), galactoglucomannoglycan (eg, softwood-derived glycan), arabinogalactoglycan (eg, soybean-derived glycan, microorganism-derived glycan, etc.), Red algae such as glucuronoglycan (eg, gellan gum), glycosaminoglycan (eg, hyaluronic acid, keratan sulfate, etc.), alginic acid and alginate, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan Derived from Natural polymeric polysaccharides and the like, from the viewpoint of not lowering the dispersion stability of the metal oxide fine particles coexisting in the coating solution, preferably, those whose structural unit has no carboxyl group or sulfonic acid group. Such polysaccharides include, for example, pentoses such as L-arabitose, D-ribose, 2-deoxyribose and D-xylose, and hexoses such as D-glucose, D-fructose, D-mannose and D-galactose only. It is preferable that it is a polysaccharide. Specifically, tamarind seed gum known as xyloglucan whose main chain is glucose and side chain is glucose, guar gum known as galactomannan whose main chain is mannose and side chain is glucose, cationized guar gum, Hydroxypropyl guar gum, locust bean gum, tara gum, and arabinogalactan whose main chain is galactose and whose side chain is arabinose can be preferably used. In the present invention, tamarind, guar gum, cationized guar gum, and hydroxypropyl guar gum are particularly preferable.

  In the present invention, it is further preferable to use two or more thickening polysaccharides in combination.

<Polymers having reactive functional groups>
Examples of water-soluble polymers applicable to the present invention include polymers having reactive functional groups, such as polyvinyl alcohols, polyvinyl pyrrolidones, polyacrylic acid, acrylic acid-acrylonitrile copolymers, acrylic acid. Acrylic resins such as potassium-acrylonitrile copolymer, vinyl acetate-acrylic acid ester copolymer, or acrylic acid-acrylic acid ester copolymer, styrene-acrylic acid copolymer, styrene-methacrylic acid copolymer, Styrene acrylic acid resin such as styrene-methacrylic acid-acrylic acid ester copolymer, styrene-α-methylstyrene-acrylic acid copolymer, or styrene-α-methylstyrene-acrylic acid-acrylic acid ester copolymer, styrene -Sodium styrene sulfonate copolymer, steel Len-2-hydroxyethyl acrylate copolymer, styrene-2-hydroxyethyl acrylate-potassium styrene sulfonate copolymer, styrene-maleic acid copolymer, styrene-maleic anhydride copolymer, vinyl naphthalene-acrylic acid copolymer Vinyl acetate copolymers such as polymers, vinyl naphthalene-maleic acid copolymers, vinyl acetate-maleic acid ester copolymers, vinyl acetate-crotonic acid copolymers, vinyl acetate-acrylic acid copolymers, and the like Salt. Among these, particularly preferable examples include polyvinyl alcohol, polyvinyl pyrrolidones, and copolymers containing the same.

  The weight average molecular weight of the water-soluble polymer is preferably 1,000 or more and 200,000 or less. Furthermore, 3,000 or more and 40,000 or less are more preferable.

  The polyvinyl alcohol preferably used in the present invention includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal and anion-modified polyvinyl alcohol having an anionic group. Alcohol is also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The degree of saponification is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  Examples of the cation-modified polyvinyl alcohol include primary to tertiary amino groups and quaternary ammonium groups, as described in JP-A No. 61-10383, in the main chain or side chain of the polyvinyl alcohol. It is obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide and the like. The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Anion-modified polyvinyl alcohol is described in, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-206088, JP-A-61-237681 and JP-A-63-307979. Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol includes, for example, a polyvinyl alcohol derivative in which a polyalkylene oxide group as described in JP-A-7-9758 is added to a part of vinyl alcohol, and JP-A-8-25795. The block copolymer of the vinyl compound and vinyl alcohol which have the described hydrophobic group is mentioned. Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification.

  In the present invention, a curing agent may be used when a polymer having a reactive functional group is used. When the polymer having a reactive functional group is polyvinyl alcohol, boric acid and a salt thereof and an epoxy curing agent are preferable.

  In the present invention, each of the water-soluble polymers is preferably contained in a range of 5.0% by mass or more and 50% by mass or less with respect to the total mass of the refractive index layer, and is 10% by mass or more and 40% by mass. The following is more preferable. However, when using together with water-soluble polymer, for example, emulsion resin, it may contain 3.0 mass% or more. If the amount of water-soluble polymer is small, the film surface is disturbed and the transparency tends to deteriorate during drying after coating the refractive index layer. On the other hand, if the content is 50% by mass or less, the relative content of the metal oxide becomes appropriate, and it becomes easy to increase the difference in refractive index between the high refractive index layer and the low refractive index layer.

[Other additives]
In the high refractive index layer and the low refractive index layer according to the present invention, various additives can be used as necessary. For example, in the present invention, an emulsion resin can be used to add an amino acid for imparting dispersion stability of a metal oxide or to modify the brittleness of a coating film.

<Amino acids with an isoelectric point of 6.5 or less>
The amino acid referred to in the present invention is a compound having an amino group and a carboxyl group in the same molecule and may be any type of amino acid such as α-amino acid, β-amino acid, γ-amino acid, etc., but has an isoelectric point of 6 The amino acid is preferably 5 or less. In general, some amino acids have optical isomers, but in the present invention, there is no difference in the effect of optical isomers, and any isomer can be used alone or in racemic form.

  For a detailed explanation of amino acids applicable to the present invention, reference can be made to the descriptions on pages 268 to 270 of the Chemical Dictionary 1 Reprint (Kyoritsu Shuppan; published in 1960).

  Specific examples of preferable amino acids include aspartic acid, glutamic acid, glycine, serine, and the like, and glycine and serine are particularly preferable.

  The isoelectric point of an amino acid is that an amino acid balances positive and negative charges in a molecule at a specific pH, and the overall charge is 0. Therefore, this pH value is called an isoelectric point. In the present invention, amino acids having an isoelectric point of 6.5 or less can be used, but the isoelectric point of each amino acid can be determined by isoelectric focusing at a low ionic strength.

<Emulsion resin>
In the present invention, the high refractive index layer or the low refractive index layer according to the present invention preferably further contains an emulsion resin.

  The emulsion resin referred to in the present invention is resin fine particles obtained by emulsion-polymerizing an oil-soluble monomer in an aqueous solution containing a dispersant and using an initiator.

  As the dispersant used in the polymerization of the emulsion resin, generally, in addition to a low molecular weight dispersant such as alkyl sulfonate, alkyl benzene sulfonate, diethylamine, ethylenediamine, quaternary ammonium salt, polyoxy Examples thereof include polymer dispersants such as ethylene nonyl phenyl ether, polyethylene ethylene laurate ether, hydroxyethyl cellulose, and polyvinyl pyrrolidone.

  The emulsion resin is a resin in which fine resin particles having an average particle diameter of about 0.01 to 2.0 μm, for example, are dispersed in an emulsion state in an aqueous medium, and an oil-soluble monomer having a high hydroxyl group. Obtained by emulsion polymerization using a molecular dispersant. There is no fundamental difference in the polymer component of the resulting emulsion resin depending on the type of dispersant used, but when emulsion polymerization is performed using a polymer dispersant having a hydroxyl group, the presence of hydroxyl groups is present on at least the surface of fine particles. It is estimated that the emulsion resin particles are different in chemical and physical properties from the emulsion resin polymerized with other dispersants.

  The polymer dispersant containing a hydroxyl group is a polymer dispersant having a weight average molecular weight of 10,000 or more, and has a side chain or a terminal substituted with a hydroxyl group, such as polyacrylic acid soda and polyacrylamide. Examples of the acrylic polymer include 2-ethylhexyl acrylate copolymerized, polyethers such as polyethylene glycol and polypropylene glycol, and polyvinyl alcohol. Polyvinyl alcohol is particularly preferable.

  Polyvinyl alcohol used as a polymer dispersant is an anion-modified polyvinyl alcohol having an anionic group such as a cation-modified polyvinyl alcohol or a carboxyl group in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate. Further, modified polyvinyl alcohol such as silyl-modified polyvinyl alcohol having a silyl group is also included. Polyvinyl alcohol has a higher effect of suppressing the occurrence of cracks when forming the ink absorbing layer when the average degree of polymerization is higher, but when the average degree of polymerization is within 5000, the viscosity of the emulsion resin is not high, and at the time of production Easy to handle. Accordingly, the average degree of polymerization is preferably 300 to 5000, more preferably 1500 to 5000, and particularly preferably 3000 to 4500. The saponification degree of polyvinyl alcohol is preferably 70 to 100 mol%, more preferably 80 to 99.5 mol%.

  Examples of the resin that is emulsion-polymerized with the above polymer dispersant include homopolymers or copolymers of ethylene monomers such as acrylic acid esters, methacrylic acid esters, vinyl compounds, and styrene compounds, and diene compounds such as butadiene and isoprene. Examples of the polymer include acrylic resins, styrene-butadiene resins, and ethylene-vinyl acetate resins.

<Other additives for each refractive index layer>
Various additives applicable to the high refractive index layer and the low refractive index layer according to the present invention 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-57-87989, and JP-A-60-72785. No. 61-146591, JP-A-1-95091, JP-A-3-13376, etc., various surfactants of anion, cation or nonion, JP-A-59- 42993, 59-52689, 62-280069, 61-242871, and JP-A-4-219266, etc., whitening agents such as sulfuric acid, phosphoric acid, acetic acid, PH adjusters such as citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, lubricants such as diethylene glycol, preservatives, Antistatic agents, can also contain various known additives such as a matting agent.

〔Base material〕
The substrate applied to the near-infrared reflective film of the present invention is preferably a film support, and the film support may be transparent or opaque, and various resin films may be used. Polyolefin films (polyethylene, polypropylene, etc.), polyester films (polyethylene terephthalate, polyethylene naphthalate, etc.), polyvinyl chloride, cellulose acetate, etc. can be used, and polyester films are preferred. Although it does not specifically limit as a polyester film (henceforth polyester), It is preferable that it is polyester which has the film formation property which has a dicarboxylic acid component and a diol component as main structural 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 constituent components, from the viewpoint of transparency, mechanical strength, dimensional stability, etc., as dicarboxylic acid components, terephthalic acid, 2,6-naphthalenedicarboxylic acid, diol components as ethylene glycol, Polyester having 1,4-cyclohexanedimethanol as a 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.

  The thickness of the film support according to the present invention is preferably 10 to 300 μm, more preferably 20 to 150 μm. The film support of the present invention may be a laminate of two sheets, and in this case, the type may be the same or different.

<< Method for producing near-infrared reflective film >>
In the method for producing a near-infrared reflective film of the present invention, the substrate has at least one unit composed of a high refractive index layer and a low refractive index layer, and the high refractive index layer and the low refractive index layer have a low refractive index layer. The difference in refractive index from the refractive index layer is 0.1 or more, and at least one of the high refractive index layer and the low refractive index layer is at least metal oxide particles, gelatin or collagen peptide, acid or salt thereof The film surface pH of the formed unit is 4.0 or more and 6.0 or less.

As a more preferred embodiment,
(1) The pH of the aqueous coating solution forming at least one of the high refractive index layer and the low refractive index layer according to the present invention is 3.8 or more and 5.8 or less,
(2) The gelatin or collagen peptide contained in the aqueous coating solution forming at least one of the high refractive index layer and the low refractive index layer according to the present invention is 1) a low molecular weight gelatin having a weight average molecular weight of 50,000 or less Or collagen peptide and 2) high molecular weight gelatin having a weight average molecular weight of 100,000 or more,
(3) A water-based coating liquid that forms at least one of the high refractive index layer and the low refractive index layer according to the present invention has a surface of metal oxide particles. 1) Low molecular weight having a weight average molecular weight of 50,000 or less. After coating with gelatin or collagen peptide, 2) It is prepared by adding high molecular weight gelatin having a weight average molecular weight of 100,000 or more.

  In preparing the high refractive index layer coating solution or the low refractive index layer coating solution according to the present invention, the acid or the salt thereof according to the present invention can be added at any stage during preparation, In the process described in 3), the surface of the metal oxide particles is coated with the low molecular gelatin or collagen peptide, and after adding high molecular weight gelatin, an acid or a salt thereof is added, or high molecular weight gelatin and an acid or a mixture thereof are added. It is preferable to add a mixture of salts.

  In the method for producing a near-infrared reflective film of the present invention, a unit composed of a high refractive index layer and a low refractive index layer is laminated on a base material. Specifically, the high refractive index layer and the low refractive index are formed. It is preferable to form a laminate by alternately applying and drying the rate layer.

  Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or US Pat. Nos. 2,761,419 and 2,761,791. A slide bead coating method using an hopper, an extrusion coating method, or the like is preferably used.

  When the slide bead coating method is used, the viscosity of the high refractive index layer coating solution and the low refractive index layer coating solution in simultaneous multilayer coating is preferably in the range of 5 to 100 mPa · s, more preferably 10 to 10 mPa · s. The range is 50 mPa · s. Moreover, when using a curtain application | coating system, the range of 5-1200 mPa * s is preferable, More preferably, it is the range of 25-500 mPa * s.

  Further, the viscosity at 15 ° C. of the coating solution is preferably 100 mPa · s or more, more preferably 100 to 30,000 mPa · s, further preferably 3,000 to 30,000 mPa · s, and most preferably 10 , 30,000 to 30,000 mPa · s.

  As a coating and drying method, the high refractive index layer coating solution and the low refractive index layer coating solution are heated to 30 ° C. or more, and after coating, the temperature of the formed coating film is once cooled to 1 to 15 ° C. The drying is preferably performed at 10 ° C. or more, and more preferably, the drying conditions are wet bulb temperature 5 to 50 ° C. and film surface temperature 10 to 50 ° C. Moreover, as a cooling method immediately after application | coating, it is preferable to carry out by a horizontal set system from a viewpoint of the formed coating-film uniformity.

  In the present invention, when preparing the above-mentioned high refractive index layer coating solution, using an aqueous high refractive index layer coating solution prepared by adding and dispersing rutile type titanium oxide having a volume average particle size of 100 nm or less, It is preferable to form a high refractive index layer. At this time, the rutile type titanium oxide is added to the high refractive index layer coating solution as an aqueous titanium oxide sol having a pH of 1.0 or more and 3.0 or less and a positive zeta potential of the titanium particles. It is preferable to prepare.

<Application of near-infrared reflective film>
The near-infrared reflective film of the present invention can be applied to a wide range of fields. For example, pasting to facilities exposed to sunlight for a long time such as outdoor windows of buildings and automobile windows, film for window pasting such as heat ray reflecting film to give heat ray reflecting effect, film for agricultural greenhouse, etc. Used mainly for the purpose of improving weather resistance.

  In particular, it is suitable for a member in which the near-infrared reflective film of the present invention is bonded to glass or a glass substitute resin base material directly or via an adhesive.

  The adhesive is placed so that the near-infrared reflective film is on the sunlight (heat ray) incident surface side when bonded to a window glass or the like. Moreover, when a near-infrared reflective film is pinched | interposed between a window glass and a base material, it can seal from surrounding gas, such as a water | moisture content, and is preferable for durability. Even if the near-infrared reflective film of the present invention is installed outdoors or outside the vehicle (for external application), it is preferable because of environmental durability.

  As an adhesive applicable to the present invention, an adhesive mainly composed of a photocurable or thermosetting resin can be used.

  The adhesive preferably has durability against ultraviolet rays, and is preferably an acrylic adhesive or a silicone adhesive. Furthermore, an acrylic adhesive is preferable from the viewpoint of adhesive properties and cost. In particular, since the peel strength can be easily controlled, a solvent system is preferable among the solvent system and the emulsion system in the acrylic adhesive. When a solution polymerization polymer is used as the acrylic solvent-based pressure-sensitive adhesive, known monomers can be used as the monomer.

  Moreover, you may use the polyvinyl butyral resin used as an intermediate | middle layer of a laminated glass, or ethylene-vinyl acetate copolymer type resin. Specifically, plastic polyvinyl butyral (manufactured by Sekisui Chemical Co., Ltd., Mitsubishi Monsanto Co., Ltd.), ethylene-vinyl acetate copolymer (manufactured by DuPont, Takeda Pharmaceutical Co., Ltd., duramin), modified ethylene-vinyl acetate copolymer (Mersen G, manufactured by Tosoh Corporation). In addition, you may add and mix | blend an ultraviolet absorber, an antioxidant, an antistatic agent, a heat stabilizer, a lubricant, a filler, coloring, an adhesion adjusting agent etc. suitably in a contact bonding layer.

  EXAMPLES 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, "part by mass" or "mass%" is represented.

Example 1
<Production of near-infrared reflective film>
[Preparation of near-infrared reflective film sample 101]
(Preparation of high refractive index layer coating solution H1)
The following additives 1) to 6) were added and mixed in this order to prepare a high refractive index layer coating solution H1.

  First, in order to coat the surface of titanium oxide particles with low molecular gelatin, the following 1) the temperature of titanium oxide particle sol was raised to 50 ° C. with stirring, and then 2) low molecular gelatin was added and stirred for 30 minutes. A mixed liquid of titanium oxide particle sol and low molecular weight gelatin was prepared. Next, the following 3) high molecular weight gelatin and 4) pure water were added and stirred and mixed for 90 minutes. Then, 5) surfactant and 6) hardener were added, and high refractive index layer coating solution H1 was added. Was prepared. As a result of measuring the pH at 40 ° C. of the prepared high refractive index layer coating solution H1 using a digital pH meter HM-30S manufactured by Toa Denpa Kogyo Co., Ltd., it was 3.5.

1) 20% by mass of titanium oxide particle sol (volume average particle size 35 nm, rutile titanium oxide particles) 60 g
2) 125% 5.0% by weight low molecular weight gelatin (Gel _L1 ) aqueous solution
3) 5.0 mass% high molecular weight gelatin (Gel _H1 ) aqueous solution 100 g
4) 150g of pure water
5) 5.0% by mass surfactant aqueous solution (Nissan Cation-2-DB-500E, quaternary ammonium salt cationic surfactant, manufactured by NOF Corporation) 0.45 g
6) 12 g of 5.0 mass% hardening agent A aqueous solution
<Preparation of aqueous solution of 5.0% by weight of hardener A>
50 g of the following hardener A and 2.4 g of β-alanine were dissolved in an appropriate amount of pure water at 60 ° C. for 90 minutes, finished to 1 L, and an aqueous solution of hardener A was prepared.

Gel _L1 used in 2) is a low molecular weight gelatin having a weight average molecular weight of 20,000 hydrolyzed by alkali treatment, and Gel _H1 used in 3) is an acid-treated gelatin having a weight average molecular weight of 130,000 (high molecular weight gelatin). It is.

(Preparation of low refractive index layer coating liquid L1)
The following additives 1) to 6) were added and mixed in this order to prepare a low refractive index layer coating solution L1.

  First, after the following 1) the temperature was raised to 40 ° C. while stirring the colloidal silica, the following 2) the low molecular gelatin was added and stirred for 10 minutes to prepare a mixed liquid of colloidal silica and low molecular gelatin. Next, after adding 3) high molecular weight gelatin and 4) pure water below, and stirring and mixing for 10 minutes, a low refractive index layer is applied in a preparation pattern in which 5) surfactant and 6) hardener are added. Liquid L1 was prepared. It was 3.7 as a result of measuring pH at 40 degreeC of the low refractive index layer coating liquid L1 prepared above using the digital pH meter HM-30S of Toa Denpa Kogyo Co., Ltd.

1) 20% by mass colloidal silica (silica doll 20P, cationic chemical colloidal silica manufactured by Nippon Chemical Industry Co., Ltd., volume average particle size 4 to 6 nm) 68 g
2) 5.0% by weight low molecular weight gelatin (Gel _L1 ) aqueous solution (supra) 180 g
3) 5.0% by weight high molecular weight gelatin (Gel _H1 ) aqueous solution (supra) 100 g
4) 240g of pure water
5) 5.0% by mass aqueous surfactant solution (Nissan Cation-2-DB-500E, quaternary ammonium salt cationic surfactant, manufactured by NOF Corporation) 0.64 g
6) 14 g of an aqueous solution of 5.0% by weight hardener A (supra)
(Formation of laminate)
<Formation of High Refractive Index Layer HA1>
While maintaining the above-prepared coating solution H1 for the high refractive index layer at 45 ° C., it was applied onto a polyethylene terephthalate film having a thickness of 35 μm heated to 45 ° C. under the condition that the dry film thickness was 135 nm, and then the film The coating film was cooled by blowing cold air for 1 minute under the condition that the surface was 15 ° C. or lower, and then dried by blowing hot air of 80 ° C. to form the high refractive index layer HA1.

<Formation of Low Refractive Index Layer LA1>
Next, while keeping the coating liquid L1 for low refractive index layer at 45 ° C., it was applied on the high refractive index layer HA1 of the polyethylene terephthalate film heated to 45 ° C. under the condition that the dry film thickness was 175 nm, The film surface was cooled by blowing cold air for 1 minute under conditions of 15 ° C. or lower, and then dried by blowing hot air of 80 ° C. to form the low refractive index layer LA1.

<Lamination of units>
On the low-refractive index layer 1 formed above, five units composed of the high-refractive index layer HA1 / the low-refractive index layer LA1 are laminated in the same manner. Sample 101, which is a near-infrared reflective film composed of (total 12 layers), was produced.

<< Production of Near-Infrared Reflective Film Samples 102-108 >>
In the preparation of the high refractive index layer coating liquid H1 and the low refractive index layer coating liquid L1 used for the preparation of the sample 101, the weight average molecular weight of the low molecular weight gelatin used for the preparation of the high refractive index layer coating liquid, each refractive index layer Each refractive index layer coating solution was prepared in the same manner except that an aqueous sodium acetate solution was added to the high molecular weight gelatin solution so that the pH of the coating solution was as shown in Table 1. Sample 102 -108 were produced.

Note that Gel _L2 used for the preparation of the high refractive index layer coating solution H3 of the sample 104 is a collagen peptide having a weight average molecular weight of 16,000, and was used for the preparation of the high refractive index layer coating solution H4 of the sample 105. Gel _L3 is acid-treated gelatin having a weight average molecular weight of 60,000. The amount of low molecular weight gelatin (Gel _L1 ) in the high refractive index layer coating solution H5 used for the preparation of the sample 107 is the same as that of the high molecular weight gelatin (Gel _H1 ) and low molecular weight gelatin in the high refractive index layer coating solution H1 of the sample 101. The amount was the same as the total amount of (Gel _L1 ).

<Measurement of characteristic values>
(Measurement of coating solution pH)
The pH at 40 ° C. of each of the high refractive index layer coating solution and the low refractive index coating solution used for preparing Samples 101 to 108 was measured using a digital pH meter HM-30S manufactured by Toa Denpa Kogyo Co., Ltd.

(Measurement of membrane surface pH)
The film surface pH of the surface of the samples 101 to 108 on which the refractive index layer unit was provided was measured by the following method.

  Using a digital pH meter HM-18B from Toa Denpa Kogyo Co., Ltd., standardize the pH meter, measure 50 μl of distilled water with a micropipette, and drop it on the surface of the refractive index layer unit of the near-infrared reflective film to be measured Then, the measurement electrode of the pH meter was lowered perpendicularly to the water drop and placed on the membrane surface, and the measured value after 30 seconds was read, and this was taken as the membrane surface pH.

(Measurement of refractive index of each layer)
Samples each having a single layer of a target layer (high refractive index layer, low refractive index layer) whose refractive index is to be measured are prepared on a base material, and each high refractive index layer and low refractive index layer are formed according to the following method. The refractive index of was determined.

  Using a U-4000 type (manufactured by Hitachi, Ltd.) as a spectrophotometer, the back side on the measurement side of each sample is roughened, and then light absorption is performed with a black spray to reflect light on the back side. The refractive index was obtained from the measurement result of the reflectance in the visible light region (400 nm to 700 nm) under the condition of regular reflection at 5 degrees.

  As a result of measuring the refractive index of each layer according to the above method, it was confirmed that the refractive index difference between the high refractive index layer and the low refractive index layer was 0.1 or more.

<< Evaluation of near-infrared reflective film >>
The following performance evaluation was performed about each produced said near-infrared reflective film.

(Evaluation of visible light transmission)
Using a spectrophotometer (using an integrating sphere, manufactured by Hitachi, Ltd., U-4000 type), the transmittance of each near-infrared reflective film in the region of 300 nm to 2000 nm is measured, and the transmittance value at 550 nm is transmitted through visible light. The visible light transmission was evaluated according to the following criteria.

A: Visible light transmittance is 85% or more. B: Visible light transmittance is 75% or more and less than 85%. Δ: Visible light transmittance is 50% or more and less than 70%. Light transmittance is less than 50% (Evaluation of near infrared transmittance)
Using a spectrophotometer (using an integrating sphere, manufactured by Hitachi, Ltd., U-4000 type), the transmittance of each near-infrared reflective film in the region of 300 nm to 2000 nm was measured, and the transmittance value at 1200 nm was determined as the near infrared. It calculated | required as the transmittance | permeability and evaluated the near-infrared transmittance according to the following reference | standard.

A: Near-infrared transmittance is less than 35% B: Near-infrared transmittance is 35% or more and less than 45% Δ: Near-infrared transmittance is 45% or more and less than 60% X: Near-infrared transmittance is 60% or more (durability evaluation)
Each of the prepared near-infrared reflective films is stored at 40 ° C. in a high-temperature and high-humidity environment of 80% RH for 72 hours, and then the near-infrared reflective film is folded and opened with the refractive index layer unit forming surface facing outside. After repeating 5 times, the formation surface of the refractive index layer unit was visually observed, and durability (high temperature and high humidity storage stability) was evaluated according to the following criteria.

◎: No folding marks or cracks are observed on the near-infrared reflective film surface ○: Slight folding marks are observed on the near-infrared reflective film surface, but no cracks are observed △: Near Small cracks are observed on the surface of the infrared reflecting film, but the quality is acceptable for practical use. ×: Many obvious cracks are generated on the surface of the near infrared reflecting film. Table 2 shows the measurement results and evaluation results obtained as described above.

  As is clear from the results shown in Table 2, the near-infrared reflective film of the present invention can reduce the near-infrared transmittance without reducing the visible light transmittance, and has a durability ( It can be seen that the high temperature and high humidity storage property is excellent.

Example 2
<Production of near-infrared reflective film>
[Production of Sample 201]
In the preparation of the sample 103 described in Example 1, the following high refractive index layer coating liquid H21 and low refractive index layer coating liquid L21 were used instead of the high refractive index layer coating liquid H2 and the low refractive index layer coating liquid L2, respectively. Sample 201 which is a near-infrared reflective film was produced in the same manner except that.

(Preparation of high refractive index layer coating solution H21)
The following additives 1) to 8) were added and mixed in this order to prepare a high refractive index layer coating solution H21.

  First, in order to coat the surface of titanium oxide particles with low molecular gelatin, the following 1) the temperature of titanium oxide particle sol was raised to 50 ° C. with stirring, and then 2) low molecular gelatin was added and stirred for 30 minutes. A mixed liquid of titanium oxide particle sol and low molecular weight gelatin was prepared. Next, after adding 3) high molecular weight gelatin and 4) pure water and stirring and mixing for 90 minutes, 5) water-soluble polymer (hydroxyethylcellulose), 6) sodium acetate, 7) surfactant, 8) A hardener was added to prepare a high refractive index layer coating solution H21.

1) 20% by mass of titanium oxide particle sol (volume average particle size 35 nm, rutile titanium oxide particles) 60 g
2) 5.0% by weight low molecular weight gelatin (Gel _L1 ) aqueous solution (supra) 125 g
3) 5.0% by weight high molecular weight gelatin (Gel _H1 ) aqueous solution (supra) 100 g
4) 37g of pure water
5) 1.0 mass% hydroxyethyl cellulose (abbreviated as HEC in Table 3) aqueous solution
113g
6) 3.3 mass% sodium acetate aqueous solution 16g
7) 5.0% by mass surfactant aqueous solution (Nissan Cation-2-DB-500E, quaternary ammonium salt cationic surfactant, manufactured by NOF Corporation) 0.45 g
8) 5.0 mass% hardener A aqueous solution (supra) 12 g
(Preparation of low refractive index layer coating liquid L21)
The following additives 1) to 8) were added and mixed in this order to prepare a low refractive index layer coating solution L21.

  First, the following 1) the temperature was raised to 40 ° C. while stirring the colloidal silica, and then the following 2) low molecular gelatin was added and stirred for 10 minutes to prepare a mixed solution of titanium oxide particle sol and low molecular gelatin. Next, after adding 3) high molecular weight gelatin and 4) pure water and stirring and mixing for 10 minutes, 5) water-soluble polymer (hydroxyethylcellulose), 6) sodium acetate, 7) surfactant, 8) A low refractive index layer coating solution L21 was prepared with a preparation pattern in which a hardener was added.

1) 20% by mass of colloidal silica 68 g
2) 5.0% by weight low molecular weight gelatin (Gel _L1 ) aqueous solution (supra) 180 g
3) 5.0% by weight high molecular weight gelatin (Gel _H1 ) aqueous solution (supra) 100 g
4) 110 g of pure water
5) 1.0 mass% hydroxyethyl cellulose (abbreviated as HEC in Table 3) aqueous solution
130g
6) 5.0 mass% sodium acetate aqueous solution 10g
7) 5.0% by mass surfactant aqueous solution (Nissan Cation-2-DB-500E, quaternary ammonium salt cationic surfactant, manufactured by NOF Corporation) 0.64 g
8) 14 g of a hardener A aqueous solution of 5.0% by mass (supra)
[Preparation of Sample 202]
In the preparation of the sample 201, hydroxyethyl cellulose (HEC) used for preparing each of the high refractive index layer coating liquid H21 and the low refractive index layer coating liquid L21 was replaced with tamarin seed gum having the same solid content (Table 3 shows polysaccharides). Sample 202 was prepared in the same manner except that the sample was changed to 1).

[Production of Sample 203]
In the preparation of the sample 201, hydroxyethyl cellulose (HEC) used for the preparation of each of the high refractive index layer coating liquid H21 and the low refractive index layer coating liquid L21 was replaced with the same amount of roast bin gum (Table 3 shows polysaccharide 2 A sample 203 was prepared in the same manner except that the sample 203 was changed.

[Measurement of each characteristic value]
The pH of each refractive index layer coating solution used for the preparation of each sample and the film surface pH of each sample were measured in the same manner as described in Example 1.

<< Evaluation of near-infrared reflective film >>
About each produced said near-infrared reflective film, it carried out similarly to the method as described in Example 1, and evaluated visible-light transmittance, near-infrared transmittance, and durability, and Table 4 shows the obtained result. .

  As is clear from the results shown in Table 4, the near-infrared reflective film of the present invention has excellent visible light transmittance and near-field by adding a water-soluble polymer to the high refractive index layer and the low refractive index layer. It can be seen that the durability is further improved while maintaining the infrared transmittance.

Example 3
In the preparation of the high refractive index layer coating solution H2 and the low refractive index layer coating solution L2 used in the preparation of the sample 103 described in Example 1, sodium carbonate and triethanolamine were used instead of sodium acetate, respectively. In the same manner except that it was added so as to be 4.8, each of the high refractive index layer coating solution and the low refractive index layer coating solution was prepared, and the sample 103 described in Example 1 was used except that they were used. Sample 301 and sample 302 were manufactured in the same manner as the manufacture.

  Next, as to the samples 301 and 302 that are the produced near-infrared reflective films, the results of evaluating visible light transmittance, near-infrared transmittance, and durability in the same manner as in the method described in Example 1, It was confirmed that the same effect as the sample 103 described in Example 1 was obtained.

Example 4
[Preparation of near-infrared reflectors 401 to 406]
Near-infrared reflectors 401 to 406 were produced using the near-infrared reflective films of Samples 102 to 107 produced in Example 1. Near-infrared reflectors 401 to 406 were prepared by adhering the near-infrared reflective films of Samples 102 to 107 with an acrylic adhesive on a transparent acrylic resin plate having a thickness of 5 mm and 20 cm × 20 cm, respectively.

[Evaluation]
The produced near-infrared reflectors 401 to 406 of the present invention can be easily used although the size of the near-infrared reflector is large, and the near-infrared reflective film of the present invention is used. As a result, excellent near-infrared reflectivity could be confirmed.

Claims (11)

The substrate has at least one unit composed of a high refractive index layer and a low refractive index layer, and the refractive index difference between the high refractive index layer and the low refractive index layer is 0.1 or more. In the near-infrared reflective film, at least one of the high refractive index layer and the low refractive index layer contains metal oxide particles, gelatin or collagen peptide, and an acid or a salt thereof, and the film surface pH of the unit but 4.0 or higher state, and are 6.0 or less,
At least one of the high refractive index layer and the low refractive index layer is 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, and 2) a high molecular weight gelatin having a weight average molecular weight of 100,000 or more. infrared reflective film characterized by containing a.   The near-infrared reflective film according to claim 1, wherein the acid or a salt thereof is a salt of a carboxylic acid having a molecular weight of 300 or less and an alkali metal or an alkaline earth metal. The high refractive index layer contains metal oxide particles, the metal oxide particles, the near of claim 1 or 2, characterized in that the following rutile-type titanium oxide particles having a volume average particle diameter of 100nm External reflection film. At least one of the high refractive index layer and the low refractive index layer contains at least one water-soluble polymer selected from celluloses, thickening polysaccharides and polymers having a reactive functional group. The near-infrared reflective film according to any one of claims 1 to 3 .   The high refractive index layer and the low refractive index layer contain 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, and 2) a high molecular weight gelatin having a weight average molecular weight of 100,000 or more. The near-infrared reflective film according to any one of claims 1 to 4, wherein: The substrate has at least one unit composed of a high refractive index layer and a low refractive index layer, and a difference in refractive index between the high refractive index layer and the low refractive index layer is 0.1 or more. In the method for producing a near-infrared reflective film for producing a near-infrared reflective film, at least one of the high refractive index layer and the low refractive index layer includes at least metal oxide particles, gelatin or collagen peptide, and acid or formed using an aqueous coating solution containing a salt thereof, formed film surface pH of the unit of 4.0 or more state, and are 6.0 or less,
The gelatin or collagen peptide contained in the aqueous coating liquid forming at least one of the high refractive index layer and the low refractive index layer is 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, 2) A method for producing a near-infrared reflective film, which is a high molecular weight gelatin having a weight average molecular weight of 100,000 or more .   The method for producing a near-infrared reflective film according to claim 6, wherein the acid or a salt thereof is a salt of a carboxylic acid having a molecular weight of 300 or less and an alkali metal or an alkaline earth metal. PH of the aqueous coating liquid for forming at least one layer of the high refractive index layer and the low refractive index layer is 3.8 or more, close according to claim 6 or 7, characterized in that at 5.8 or less A method for producing an infrared reflective film. Water-based coating liquid for forming at least one layer of the high refractive index layer and the low refractive index layer, the surface of the metal oxide particles, wherein 1) the low molecular weight gelatin or collagen peptide is a weight average molecular weight of 50,000 or less The near-infrared reflective film according to any one of claims 6 to 8, which is prepared by adding 2) a high molecular weight gelatin having a weight average molecular weight of 100,000 or more after coating. Production method.   The aqueous coating solution for forming the high refractive index layer and the low refractive index layer includes 1) a low molecular weight gelatin or collagen peptide having a weight average molecular weight of 50,000 or less, and 2) a weight average molecular weight of 100,000 or more. The method for producing a near-infrared reflective film according to any one of claims 6 to 9, comprising high molecular weight gelatin.   A near-infrared reflector having the near-infrared reflective film according to any one of claims 1 to 5 on at least one surface side of a substrate.