JP2016212326A - Optical Reflection Film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical reflection film that suppresses red coloration in an initial stage and is less likely to cause changes in a hue even exposed to sun rays for a long time.SOLUTION: An optical reflection film includes at least one laminated unit having a low refractive index layer and a high refractive index layer on a substrate. The high refractive index layer comprises a water-soluble resin, titanium oxide particles and a nitrogen-containing heteroaromatic compound; and the heteroaromatic compound is included by over 0 mass% and less than 20 mass% with respect to the titanium oxide particles.SELECTED DRAWING: None

Description

  The present invention relates to an optical reflection film.

  In general, it is known that a multilayer film in which a high refractive index layer and a low refractive index layer are laminated on the surface of a substrate by adjusting the optical film thickness selectively reflects light of a specific wavelength. ing. Such a multilayer film is used as, for example, an optical reflection film installed on a window of a building, a member for a vehicle, or the like. Such an optical reflection film can control the reflection wavelength only by adjusting the film thickness and refractive index of each layer, and can reflect various light such as infrared rays, ultraviolet rays, and visible light.

  In recent years, interest in energy-saving measures has increased, and heat insulation glass with infrared shielding properties for the purpose of shielding the solar radiation energy entering the interior or interior of a building glass or vehicle glass and reducing the temperature rise and cooling load. Is adopted. On the other hand, an infrared shielding film formed by laminating layers having different refractive indexes is conventionally known, and a method of blocking transmission of heat rays in sunlight by pasting this infrared shielding film on glass However, it is attracting attention as a simpler method.

  As an infrared shielding film, there is a method in which a laminated film in which a high refractive index layer and a low refractive index layer are alternately laminated is produced by a vapor deposition method such as vapor deposition or sputtering. However, the vapor deposition method has problems such as high manufacturing cost, difficulty in increasing the area, and limitation to heat-resistant materials.

  Therefore, when manufacturing an infrared shielding film, it is more advantageous to use a liquid phase film forming method (wet) from the viewpoint that the manufacturing cost is low, the area can be increased, and the selection range of the substrate is wide. . As a technique using a liquid phase film formation method, for example, Patent Document 1 is manufactured by applying and laminating a coating solution containing a mixture of a water-soluble polymer and metal oxide fine particles by a wet coating method. An optical reflection film (near infrared reflection film) is disclosed.

  However, as described above, the optical reflection film formed of the coating liquid containing metal oxide fine particles (mainly titanium oxide) may change color (change the color tone) when exposed to sunlight for a long time. The problem became clear. Various studies have been made on such problems, and as one of them, Patent Document 2 proposes a dispersion containing a cobalt complex together with titanium oxide-containing particles. A technique for producing a substrate with a transparent film (film) using a coating composition containing a resin as a matrix-forming component has been proposed.

International Publication No. 2012/014607 JP 2014-38293 A

  According to the technique of Patent Document 2, excitation of titanium oxide by ultraviolet rays is suppressed by the cobalt complex, and a change in color tone due to bluening of titanium oxide and occurrence of cracks (film cracks) in the coating film are prevented. However, the present inventors have a problem that the optical reflective film produced using the technique of Patent Document 2 is reddish even at the initial stage (immediately after production), and the use of the optical reflective film is limited. Found that there is. Further, the present inventors have found that even with the technique of Patent Document 2, there is a problem that the color tone of the optical reflection film varies when exposed to sunlight for a long time. Furthermore, when the optical reflection film manufactured using the technique of patent document 2 is exposed to sunlight for a long time, it turned out that there exists a problem that a crack arises.

  Accordingly, an object of the present invention is made in view of the above circumstances, and provides an optical reflective film that suppresses the initial red coloration and is less likely to cause color tone fluctuations even when exposed to sunlight for a long time. There is to do. Another object of the present invention is to provide a highly durable optical reflective film in which the occurrence of cracks is suppressed.

  The present inventors have conducted intensive studies in view of the above problems. As a result, in the optical reflective film including at least one unit in which the low refractive index layer and the high refractive index layer are laminated, the above problem is solved by forming the high refractive index layer having the following configuration. As a result, the present invention has been completed.

  That is, the above object is achieved by at least one of the following means.

1. An optical reflective film comprising at least one unit obtained by laminating a low refractive index layer and a high refractive index layer on a substrate, wherein the high refractive index layer comprises a water-soluble resin, titanium oxide particles, and nitrogen-containing An optical reflective film comprising a heteroaromatic compound, wherein the nitrogen-containing heteroaromatic compound is contained in the high refractive index layer in an amount of more than 0% by mass and less than 20% by mass with respect to the titanium oxide particles;
2. 1. The nitrogen-containing heteroaromatic compound contains an imidazole skeleton. An optical reflective film according to claim 1;
3. 1. The nitrogen-containing heteroaromatic compound comprising a benzimidazole skeleton. Or 2. An optical reflective film according to claim 1;
4). 1. The nitrogen-containing heteroaromatic compound having an amino group, a monoalkylamino group or a dialkylamino group. ~ 3. An optical reflective film according to any one of
5. In the high refractive index layer, the nitrogen-containing heteroaromatic compound is contained in an amount of 1 to 15% by mass with respect to the titanium oxide particles. ~ 4. An optical reflective film according to any one of
6). The titanium oxide particles include rutile-type titanium oxide. ~ 5. An optical reflective film according to any one of
7). The titanium oxide particles include titanium oxide that is silica-modified. ~ 6. The optical reflecting film according to any one of the above.

  The optical reflective film of the present invention contains the specific nitrogen-containing heteroaromatic compound together with the titanium oxide particles in the high refractive index layer, thereby suppressing the initial red coloration of the film and being long to sunlight. Even when exposed to time, the color tone is less likely to fluctuate. Furthermore, according to the present invention, it is possible to obtain an optical reflective film which is suppressed in the occurrence of cracks and excellent in durability by adopting the above configuration.

  According to one aspect of the present invention, the optical reflective film includes at least one unit in which a low refractive index layer and a high refractive index layer are laminated on a substrate, and the high refractive index layer is a water-soluble resin. And the titanium oxide particles and the nitrogen-containing heteroaromatic compound, and the nitrogen-containing heteroaromatic compound in the high refractive index layer is more than 0% by mass and less than 20% by mass with respect to the titanium oxide particles. An optical reflective film is provided.

  The optical reflective film according to the present invention has a structure in which a low refractive index layer and a high refractive index layer are laminated. In the examination of such a film, the present inventors applied the technique of Patent Document 2, and when the obtained optical reflection film is reddish even in the initial stage and further exposed to sunlight for a long time. , Found that there is a problem that the color tone fluctuates.

  Regarding the red coloration as described above, the present inventors have conducted various studies on compounds in which redness at an early stage is not a problem and the bluening of titanium oxide can be suppressed. As a result, it has been surprisingly found that the above object can be achieved by adding a predetermined amount of a nitrogen-containing heteroaromatic compound. The mechanism is presumed as follows.

  The present inventors paid attention to the coloring of the titanium oxide itself contained in the high refractive index layer as the cause of the change in the color tone of the optical reflection film when exposed to sunlight for a long time. And titanium oxide (especially rutile type titanium oxide), when exposed to ultraviolet rays, the titanium oxide particles themselves turn blue, and various studies were conducted from the viewpoint of suppressing this.

When the surface of the titanium oxide particles is irradiated with ultraviolet rays, oxygen atoms are desorbed by a reduction reaction, and the titanium in the titanium oxide is changed from “Ti ⁴⁺ (that is, tetravalent state, colorless state)” to “Ti ³⁺ ”. (That is, a trivalent state and a blue state). Thus, the coloring of the titanium oxide particles is considered to be caused by the change of the electronic state of titanium (oxidation-reduction reaction) due to ultraviolet irradiation.

  According to Patent Document 2, it is considered that a certain degree of coloring suppression effect is obtained by the cobalt complex used together with the titanium oxide-containing particles. However, the present inventors have found that the optical reflection film according to the technique of Patent Document 2 changes in color tone when exposed to sunlight for a long time, even if a cobalt complex is added. This was thought to be due to insufficient suppression of coloring (blue coloration).

In contrast to such a conventional technique, the optical reflective film according to the present invention contains a nitrogen-containing heteroaromatic compound together with titanium oxide particles in the high refractive index layer. This nitrogen-containing heteroaromatic compound is more likely to contribute to the oxidation of titanium than cobalt because the nitrogen-containing heteroaromatic ring tends to be stabilized by delocalizing electrons in addition to being easily adsorbed to the titanium oxide particles. It is expected that the effect of suppressing coloring of titanium oxide particles is extremely high. Specifically, in order to suppress the blue color of titanium oxide, it is necessary to return from the “Ti ³⁺ ” state that exhibits blue color to the colorless “Ti ⁴⁺ ” state (that is, to release electrons from titanium). However, since the nitrogen-containing heteroaromatic compound in the present invention is easily adsorbed to the titanium oxide particles as described above, the nitrogen-containing heteroaromatic compound is likely to be present in the vicinity of the titanium oxide particles. As a result, the state of “Ti ³⁺ ” It is easy to receive electrons from titanium. In addition, the nitrogen-containing heteroaromatic ring tends to stabilize by delocalizing the received electrons. Therefore, the nitrogen-containing heteroaromatic compound can easily proceed the process of returning titanium from the blue “Ti ³⁺ ” state to the colorless “Ti ⁴⁺ ” state, and the electron delocalization It can be said that it is easy to hold electrons by stabilization. Therefore, it is estimated that the nitrogen-containing heteroaromatic compound in this invention can suppress the coloring of a titanium oxide particle effectively.

  In addition, as described above, the optical reflective film of the present invention uses a nitrogen-containing heteroaromatic compound. However, unlike the cobalt complex used in Patent Document 2, the compound is an organic oxidant, mainly carbon. And a compound consisting of nitrogen. By using such a compound, it is possible not only to suppress reddish coloration, which becomes a problem when using a cobalt complex, but also to suppress color tone fluctuations as described above.

  Thus, according to the above mechanism, the initial redness of the optical reflective film according to the present invention is extremely reduced, and variation in color tone is suppressed.

  The optical reflective film of the present invention is also excellent in terms of durability. In the optical reflective film according to the present invention, the high refractive index layer contains a water-soluble resin, but the water-soluble resin is in an environment where the decomposition reaction is easily promoted by the photocatalytic action of the titanium oxide particles contained together. On the other hand, it is thought that by adding a nitrogen-containing heteroaromatic compound, the photocatalytic action of titanium oxide is also suppressed, so that decomposition of the water-soluble resin is suppressed.

  Furthermore, in this invention, it is estimated that the effect which improves durability is acquired also by coloring of a titanium oxide particle being suppressed by the following mechanisms.

  Here, as described above, the durability is improved by suppressing the decomposition of the water-soluble resin, but the relationship between the suppression of coloring of the titanium oxide particles and the effect of improving the durability will be outlined. The state in which titanium oxide is blue (colored) is a state in which light in the near-infrared region is absorbed (complementary color relationship). In such a state, the high refractive index layer containing titanium oxide accumulates heat and becomes high temperature, and as a result, the water-soluble resin deteriorates. However, in the present invention, as described above, since the bluening of the titanium oxide particles is suppressed, the temperature increase of the high refractive index layer is suppressed and prevented, and deterioration of the water-soluble resin is effectively suppressed. It is thought that you can.

  In addition, in the optical reflective film according to the present invention, the content of the nitrogen-containing heteroaromatic compound in the high refractive index layer is more than 0% by mass and less than 20% by mass with respect to the titanium oxide particles. As described above, since the nitrogen-containing heteroaromatic compound exhibits a high coloring suppression effect, the coloring of the titanium oxide particles can be sufficiently suppressed even in such a small amount. If it does so, since the quantity of the water-soluble resin which comprises a high refractive index layer can be made relatively large, a film | membrane crack can be suppressed and sufficient durability is acquired.

  As described above, the optical reflecting film of the present invention is considered to exhibit the effect that the initial redness is extremely reduced by the above-described mechanism, and not only the change in color tone is small, but also the durability is excellent. In addition, in a unit in which a high refractive index layer and a low refractive index layer are stacked, as will be described later, many layers may be stacked in order to control optical characteristics (mainly light reflectance). In particular, the problem of color tone is likely to occur. However, according to the present invention, since the problem of color tone is solved as described above, the problem of color tone is further solved while achieving good optical characteristics. Note that the mechanism for exerting the operational effects of the configuration of the present invention described above is speculation, and the present invention is not limited by the above speculation.

  Hereinafter, the components of the optical reflecting film of the present invention will be described in detail. In this specification, “X to Y” indicating a range means “X or more and Y or less”. Unless otherwise specified, measurement of operation and physical properties is performed under conditions of room temperature (20 to 25 ° C.) / Relative humidity 40 to 50%.

[Optical reflection film]
The optical reflective film according to the present invention includes at least one unit in which a low refractive index layer and a high refractive index layer are laminated on a substrate. In this specification, the terms “high refractive index layer” and “low refractive index layer” refer to the refractive index layer having a higher refractive index when the refractive index difference between two adjacent layers is compared. This means that the lower refractive index layer is the lower refractive index layer. In the present invention, since the “high refractive index layer” includes titanium oxide particles, the refractive index layer adjacent to the “high refractive index layer” is designed to have a refractive index lower than that of the “high refractive index layer”. Refractive index layer ".

  Moreover, in this specification, when not distinguishing a low refractive index layer and a high refractive index layer, it may be called a "refractive index layer" as a concept containing both. Further, in the present specification, a portion where a plurality of units each including a low refractive index layer and a high refractive index layer are stacked may be simply referred to as an “optical reflection layer” or “reflection layer”.

  The optical reflection film has a base material and an optical reflection layer in this order, and the optical reflection layer is preferably disposed on a surface on which light is incident. Furthermore, the optical reflection layer may be disposed adjacent to the base material, or another layer may be interposed between the base material and the optical reflection layer.

  In the optical reflective film of the present invention, the high refractive index layer constituting the optical reflective layer contains a water-soluble resin, titanium oxide particles, and a nitrogen-containing heteroaromatic compound. Below, each component contained in a high refractive index layer is explained in full detail first.

<Nitrogen-containing heteroaromatic compound (oxidant)>
In the optical reflective film according to the present invention, the high refractive index layer is a nitrogen-containing heteroaromatic compound (referred to as “oxidation” in this specification) in order to suppress blueening (coloring) of the titanium oxide particles and discoloration of the water-soluble resin. Sometimes referred to as "agent"). In the present invention, the nitrogen-containing heteroaromatic compound used is a compound containing a heteroaromatic group containing a nitrogen atom as an essential structure. In one high refractive index layer, the nitrogen-containing heteroaromatic compound may be used singly or in combination of two or more.

As described above, the nitrogen-containing heteroaromatic compound according to the present invention is titanium of titanium oxide particles contained in the high refractive index layer, more specifically, “Ti ³⁺ ” which is trivalent titanium exhibiting blue. It is a compound that can easily receive electrons from. Therefore, by adding the nitrogen-containing heteroaromatic compound, an oxidation reaction from “Ti ³⁺ ” to colorless “Ti ⁴⁺ ” (reaction to return to Ti ⁴⁺ ) easily occurs, and coloring of titanium oxide particles is effectively performed. Can be suppressed. As a result, even when exposed to sunlight (mainly ultraviolet rays), the color tone variation due to the coloring of the titanium oxide particles is effectively suppressed. Furthermore, the addition of these nitrogen-containing heteroaromatic compounds suppresses the photocatalytic action of titanium oxide particles, and also suppresses the bluening of titanium oxide, so that the water-soluble resin contained in the high refractive index layer is decomposed and deteriorated. Is also suppressed. As a result, the effect of suppressing color tone variation is further improved.

  Content of nitrogen-containing heteroaromatic compound (oxidant; hereinafter sometimes abbreviated as “Ox”) in the high refractive index layer (when two or more nitrogen-containing heteroaromatic compounds are included, the total amount thereof) ) In addition to the purpose of effectively suppressing the coloring of the titanium oxide particles, and for the purpose of obtaining practical optical properties, the amount of the titanium oxide particles in the high refractive index layer exceeds 20% by mass and exceeds 20% by mass. %. Thus, the nitrogen-containing heteroaromatic compound according to the present invention can obtain a sufficient coloring suppression effect even in a very small amount.

  In addition, since the content of the water-soluble resin constituting the high refractive index layer can be relatively increased by setting the content of the nitrogen-containing heteroaromatic compound in the high refractive index layer in the above range, high durability Sex is also obtained.

  Furthermore, when a large amount of a nitrogen-containing heteroaromatic compound (oxidant) is added to the high refractive index layer, interfacial mixing with the adjacent low refractive index layer is easily promoted, and haze tends to be a problem. As described above, by setting the nitrogen-containing heteroaromatic compound to less than 20% by mass with respect to the titanium oxide particles, the above haze problem can be suppressed.

  From the viewpoint of effectively suppressing the coloring of the titanium oxide particles and reducing haze, the nitrogen-containing heteroaromatic compound (oxidant) is 1 to 15 masses with respect to the titanium oxide particles in the high refractive index layer. % Is preferable. Furthermore, from the viewpoint that it is easy to achieve both the effect of suppressing coloring and durability, the content of the nitrogen-containing heteroaromatic compound (oxidant) (when two or more nitrogen-containing heteroaromatic compounds are included, the total The amount is more preferably from 3 to 15% by mass, even more preferably from 5 to 12% by mass, particularly preferably from 5% to 10% by mass with respect to the titanium oxide particles. As will be described in detail below, when silica-modified titanium oxide particles are used as the titanium oxide particles, the mass of the silica-modified titanium oxide particles is referred to as “mass of titanium oxide particles”.

Here, the content of the nitrogen-containing heteroaromatic compound in the high refractive index layer, and the mass ratio of the nitrogen-containing heteroaromatic compound (Ox) to the titanium oxide particles (TiO ₂ particles) (Ox / TiO _2). Particles) are measured by performing the following analysis on the high refractive index layer.

  First, the content (number of moles) of the nitrogen-containing heteroaromatic compound (Ox) in the high refractive index layer is measured by analyzing it using FT-IR (Fourier transform infrared spectroscopy) of the optical reflection film. can do. Then, from the number of moles of the obtained nitrogen-containing heteroaromatic compound (Ox), based on the molecular weight of the nitrogen-containing heteroaromatic compound obtained in advance, the nitrogen-containing heteroaromatic compound (Ox) contained in the high refractive index layer ) Is calculated. The measurement at this time is preferably performed after drying for 1 to 60 minutes at a temperature equal to or lower than the melting temperature of the base material in order to reduce the influence due to absorption of water molecules.

  Next, the content of titanium oxide particles in the high refractive index layer is measured as follows. That is, in the present invention, based on the particle size, the amount of titanium in the high refractive index layer (further, titanium oxide) is obtained by a method (STEM-EDX) that combines a scanning transmission electron microscope and energy dispersive X-ray spectroscopic analysis. Particle amount). For example, the composition distribution measurement between particles using STEM-EDX is specifically performed by the following procedure.

  First, a cross-section slice of the optical reflection layer is prepared by an ultramicrotome, collected on a microgrid, and used as a sample. The thickness of the ultrathin section is preferably 100 nm or less, and in the present invention, an ultrathin section having a thickness of 80 nm is prepared.

  The measurement is performed using a transmission electron microscope (JEM2010F manufactured by JEOL Ltd.) and an energy dispersive X-ray spectroscopic analyzer (a PIONEER type detector and a VANTAGE digital microanalysis system manufactured by NORAN). The accelerating voltage of the transmission electron microscope is preferably 200 kV, and the magnification can be adjusted as appropriate. In this invention, it measures by 50,000 times. After adjusting the axis of the electron microscope, observe in the scanning transmission mode, confirm the high refractive index layer containing titanium oxide, and then detect the element (ie, Ti) to be detected using software (VISTA manufactured by NORAN). Get element map. The resolution of the element map can be adjusted as appropriate, but is set to 256 × 256 pixels or more. The measurement time is integrated until the X-ray peak of the minor component element reaches 200 counts or more.

  The content of titanium (number of moles of Ti) in the high refractive index layer can be calculated using the X-ray intensity and the sensitivity coefficient obtained in advance from the standard sample. Then, the mass of the titanium oxide particles can be calculated from the obtained titanium content (number of moles of Ti). When the titanium oxide particles are silica-modified (coated with silicon-containing hydrated oxide), the silicon content (number of moles of Si) is determined in the same manner as described above. Based on this, the mass of silicon coated on titanium oxide can be calculated. Then, the sum of the mass of the titanium oxide and the mass of the silicon-containing hydrated oxide coated on the particles is calculated to obtain the mass of the titanium oxide particles.

Then, using the content (mass) of the nitrogen-containing heteroaromatic compound (Ox) in the high refractive index layer calculated as described above and the content (mass) of the titanium oxide particles, The mass ratio (Ox / TiO ₂ particles) of the group compound (Ox) to the titanium oxide particles (TiO ₂ particles) can be calculated.

  The nitrogen-containing heteroaromatic compound used in the present invention is not particularly limited as long as it can promote the oxidation reaction of titanium oxide as described above (that is, suppress the bluening of titanium oxide). Nitrogen-containing heteroaromatic compounds may be used, and examples thereof include benzimidazole compounds, imidazole compounds, pyridine compounds, pyrazine compounds, pyrazole compounds, quinoline compounds, and the like.

  These nitrogen-containing heteroaromatic compounds preferably have a group that is easily adsorbed to the titanium oxide particles (also referred to as “adsorbing group”). The nitrogen-containing heteroaromatic compound having an adsorbing group is likely to be present in the vicinity of the titanium oxide particles. As a result, the nitrogen-containing heteroaromatic compound is likely to contribute to the oxidation reaction of titanium oxide, and as a result, a higher coloring suppression effect can be obtained.

The nitrogen-containing heteroaromatic compound preferably has at least one cationic group as the adsorbing group. The cationic group is easily adsorbed on the surface of anionic titanium oxide (more specifically, oxygen), and the nitrogen-containing heteroaromatic compound and titanium oxide are very likely to interact with each other. Examples of the cationic group include an amino group (—NH ₂ ); a monoalkylamino group such as a methylamino group and an ethylamino group; a dialkylamino group such as a dimethylamino group and a diethylamino group; an imino group; a guanidino group and the like. It is done. The amino group may be —NH ₃ ⁺ in which a proton is coordinated.

  Among the above, the adsorbing group is preferably an amino group, a monoalkylamino group or a dialkylamino group from the viewpoint that the stability of the compound is high and the coloration suppressing effect is easily maintained over a long period of time (note that the monoalkyl group and Details of the alkyl group contained in the dialkylamino group will be described in detail below). That is, the nitrogen-containing heteroaromatic compound used in the present invention preferably has an amino group, a monoalkylamino group or a dialkylamino group. Furthermore, considering the availability of nitrogen-containing heteroaromatic compounds, the nitrogen-containing heteroaromatic compounds are more preferably those having an amino group.

  Hereinafter, examples of the nitrogen-containing heteroaromatic compound that are particularly effective in suppressing the coloring of the film will be described, but the present invention is not limited thereto.

  The nitrogen-containing heteroaromatic compound used in the present invention is a benzimidazole compound, an imidazole compound, a pyridine compound, or a pyrazine compound among the above compound groups from the viewpoints of film coloring suppression effect, durability improvement, and the like. A compound is preferred. Hereinafter, each compound will be described in detail.

(Benzimidazole compounds)
In the present invention, the benzimidazole compound used as the nitrogen-containing heteroaromatic compound is a compound having a benzimidazole skeleton. The benzimidazole compound naturally includes an imidazole skeleton.

  Here, the benzimidazole compound is preferably a compound represented by the following general formula (I). That is, the nitrogen-containing heteroaromatic compound has the following general formula (I):

In the general formula (I),
R ¹¹ each independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms. Group, substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted aryl group having 6 to 30 carbon atoms, substituted or unsubstituted carbon An aryloxy group having 6 to 20 amino acids, an amino group (—NH ₂ ), a substituted or unsubstituted monoalkylamino group having 1 to 20 carbon atoms, a substituted or unsubstituted dialkylamino group having 2 to 20 carbon atoms, and a thiol group (—SH) or a carboxyl group (—COOH),
R ¹² and R ¹³ each independently represent a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted carbon, An alkenyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, Substituted or unsubstituted aryloxy group having 6 to 20 carbon atoms, amino group, substituted or unsubstituted monoalkylamino group having 1 to 20 carbon atoms, substituted or unsubstituted dialkylamino group having 2 to 20 carbon atoms, thiol Group or carboxyl group,
m is an integer from 0 to 4,
It is preferable that it is the benzimidazole compound shown by these.

  In the present specification, “substituted or unsubstituted” means that a hydrogen atom of a certain group may be substituted or not substituted with another group. Here, the substituent that can be substituted is not particularly limited as long as the effect of the present invention is obtained. Further, the number of substituents that are further substituted with respect to one substituent is not particularly limited. In the above, they are not substituted with the same substituent. That is, an alkyl group as a substituent is not substituted with an alkyl group.

  The alkyl group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Group, n-pentyl group, isopentyl, neopentyl, tert-pentyl group, n-hexyl group, n-heptyl group, n-octyl group, 2-ethylhexyl group, n-nonyl group, n-decyl group, n-undecyl group Linear or branched alkyl groups such as n-dodecyl group, n-tridecyl group, n-tetradecyl group, 2-tetraoctyl group, n-pentadecyl group, n-hexadecyl group, 2-hexyldecyl group. . Here, each layer of the optical reflection film is formed using an aqueous solvent since a water-soluble resin is used as will be described later. Also, from the viewpoint of improving productivity and the like, a method of applying using an aqueous solvent is preferably used as a method of forming each layer. Therefore, the productivity of the optical reflective film can be improved by improving the water solubility of the nitrogen-containing heteroaromatic compound contained in the high refractive index layer and dissolving it in an aqueous solvent. Therefore, from the viewpoint of improving the water solubility of the nitrogen-containing heteroaromatic compound, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkyl group having 1 to 5 carbon atoms is more preferable.

  Although there is no restriction | limiting in particular as said C3-C20 cycloalkyl group, For example, a cyclopropyl group, a cyclopentyl group, a cyclohexyl group, a norbornyl group, an adamantyl group etc. are mentioned. Among these, like the above, it is preferable that it is a C3-C8 cycloalkyl group from a viewpoint of improving water solubility.

  Although there is no restriction | limiting in particular as said C2-C20 alkenyl group, For example, a vinyl group, 1-propenyl group, 2-propenyl group (allyl group), isopropenyl group, 1-butenyl group, 2-butenyl group , 3-butenyl group, 1-pentenyl group, 2-pentenyl group, 3-pentenyl group, 1-hexenyl group, 2-hexenyl group and the like. Similarly to the above, from the viewpoint of improving water solubility, an alkenyl group having 2 to 10 carbon atoms is preferable.

  The alkynyl group having 2 to 20 carbon atoms is not particularly limited, and examples thereof include acetylenyl group, 1-propynyl group, 2-propynyl group (propargyl group), 1-butynyl group, 2-butynyl group, and 3-butynyl. Group, 1-pentynyl group, 2-pentynyl group, 3-pentynyl group, 1-hexynyl group, 2-hexynyl group and the like. Similarly to the above, an alkynyl group having 2 to 10 carbon atoms is preferable from the viewpoint of improving water solubility.

  The alkoxy group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a methoxy group, an ethoxy group, an isopropoxy group, a tert-butoxy group, an n-octyloxy group, an n-decyloxy group, and an n-dodecyloxy group. Group, n-hexadecyloxy group, 2-ethylhexyloxy group, 2-hexyldecyloxy group, 2-decyltetradecyloxy group and the like. Similarly to the above, from the viewpoint of improving water solubility, an alkoxy group having 1 to 10 carbon atoms is preferable.

  The aryl group having 6 to 30 carbon atoms is not particularly limited, and examples thereof include non-condensed hydrocarbon groups such as a phenyl group, a biphenyl group, and a terphenyl group; a pentarenyl group, an indenyl group, a naphthyl group, an azulenyl group, and a heptaenyl group. Groups, biphenylenyl groups, fluorenyl groups, acenaphthylenyl groups, preadenenyl groups, acenaphthenyl groups, phenalenyl groups, phenanthryl groups, anthryl groups, and the like. Similarly to the above, from the viewpoint of improving water solubility, an aryl group having 6 to 10 carbon atoms is preferable.

  The aryloxy group having 6 to 20 carbon atoms is not particularly limited, and examples thereof include phenyloxy and 2-naphthyloxy. Similarly to the above, from the viewpoint of improving water solubility, an aryloxy group having 6 to 10 carbon atoms is preferable.

  The monoalkylamino group having 1 to 20 carbon atoms is a substituent represented by —NHR, where R represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms. Since the alkyl group is the same as described above, details are omitted. The monoalkylamino group is not particularly limited, and examples thereof include a methylamino group and an ethylamino group. Similarly to the above, from the viewpoint of improving water solubility, a monoalkylamino group having 1 to 10 carbon atoms is preferable, and a monoalkylamino group having 1 to 5 carbon atoms is more preferable.

  The dialkylamino group having 2 to 20 carbon atoms is a substituent represented by —NR′R ″, wherein R ′ and R ″ are each independently a substituted or unsubstituted carbon atom having 1 to 20 carbon atoms. Represents an alkyl group. Since the alkyl group is the same as described above, details are omitted. The dialkylamino group is not particularly limited, and examples thereof include a dimethylamino group and a diethylamino group. Similarly to the above, a dialkylamino group having 2 to 10 carbon atoms is preferable from the viewpoint of improving water solubility.

In the above formula (I), m represents the number of R ¹¹ substituted on the benzene ring of the benzimidazole skeleton, if it is an integer of 0 to 4 preferred. Similarly to the above, m is preferably a carbon number of 0 to 2 from the viewpoint of improving water solubility or improving electron acceptability. In addition, when m is 2 or more, R ¹¹ may be the same or different.

Among the forms described above, the benzimidazole-based compound as the nitrogen-containing heteroaromatic compound according to the present invention, in the general formula (I), each R ¹¹ is independently a substituted or unsubstituted carbon number of 1 to 10 alkyl group, amino group, monoalkylamino group or dialkylamino group, R ¹² and R ¹³ each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, or a thiol. And m is preferably a benzimidazole compound represented by the following formula:

  Examples of the benzimidazole compound preferably used in the present invention include benzimidazole, 5-methylbenzimidazole, 2-aminobenzimidazole, 5,6-dimethylbenzimidazole, 1-methylbenzimidazole, 2-methylbenzimidazole, Examples include 2- (methylthio) benzimidazole, 2-mercaptobenzimidazole, 5-benzimidazolecarboxylic acid, and 5-amino-2-mercaptobenzimidazole. Among them, 5-amino-2-mercaptobenzimidazole (compound represented by the following chemical formula 1), 2-methylbenzimidazole (compound represented by the following chemical formula 2), 5-methylbenzimidazole (expressed by the following chemical formula 3). And the like.

  The said benzimidazole type compound may be used individually by 1 type, and may use 2 or more types together.

(Imidazole compounds)
In the present invention, the imidazole compound used as the nitrogen-containing heteroaromatic compound is a compound having an imidazole skeleton.

  Here, the imidazole compound is preferably a compound represented by the following general formula (II). That is, the nitrogen-containing heteroaromatic compound has the following general formula (II):

In the general formula (II),
R ²¹ each independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms. Group, substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted aryl group having 6 to 30 carbon atoms, substituted or unsubstituted carbon An aryloxy group having 6 to 20 amino acids, a substituted or unsubstituted monoalkylamino group having 1 to 20 carbon atoms, a substituted or unsubstituted dialkylamino group having 2 to 20 carbon atoms, a thiol group, or a carboxyl group; ,
R ²² represents a hydrogen atom, a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms, A substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, a substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, a substituted or unsubstituted aryl group having 6 to 30 carbon atoms, a substituted or unsubstituted carbon number 6 An aryloxy group of -20, an amino group, a substituted or unsubstituted monoalkylamino group having 1 to 20 carbon atoms, a substituted or unsubstituted dialkylamino group having 2 to 20 carbon atoms, a thiol group, or a carboxyl group,
n is an integer of 0 to 3,
It is preferable in it being an imidazole compound shown by these.

Since each said substituent is the same as that of what was demonstrated by the term of the above-mentioned (benzimidazole type compound), detailed description and illustration are abbreviate | omitted. In addition, when n is 2 or more, R ²¹ may be the same or different.

Among the forms described above, the imidazole compound as the nitrogen-containing heteroaromatic compound according to the present invention is the above-mentioned general formula (II), wherein R ²¹ is independently substituted or unsubstituted 1 to 10 carbon atoms. An alkyl group, an amino group, a monoalkylamino group, a dialkylamino group, a thiol group or a carboxyl group, R ²² is a hydrogen atom, or a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and n is And an imidazole compound represented by the following formula:

  Examples of the imidazole compound preferably used in the present invention include 1-methylimidazole, 1-butylimidazole, 2-methylimidazole, 2-ethylimidazole, 1-methyl-4-phenylimidazole, 4-methyl-2-phenyl. Examples include imidazole, 2-aminoimidazole, 2-mercapto-1-methylimidazole, 2-ethyl-4-methylimidazole, 4-imidazolecarboxylic acid and the like. Among them, 1-methylimidazole (compound represented by the following chemical formula 4), 2-aminoimidazole (compound represented by the following chemical formula 5), 2-mercapto-1-methylimidazole (compound represented by the following chemical formula 6). ), 2-ethyl-4-methylimidazole (compound represented by the following chemical formula 7), 4-imidazolecarboxylic acid (compound represented by the following chemical formula 8), and the like are preferable.

  The said imidazole type compound may be used individually by 1 type, and may use 2 or more types together.

(Pyridine compound)
In the present invention, the pyridine compound used as the nitrogen-containing heteroaromatic compound is a compound having a pyridine skeleton.

  Here, the pyridine-based compound is preferably a compound represented by the following general formula (III). That is, the nitrogen-containing heteroaromatic compound has the following general formula (III):

In the general formula (III),
R ³¹ each independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms. Group, substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted aryl group having 6 to 30 carbon atoms, substituted or unsubstituted carbon An aryloxy group having 6 to 20 amino acids, a substituted or unsubstituted monoalkylamino group having 1 to 20 carbon atoms, a substituted or unsubstituted dialkylamino group having 2 to 20 carbon atoms, a thiol group (-SH) or A carboxyl group,
p is an integer of 0 to 4,
It is preferable in it being a pyridine compound shown by these.

Since each said substituent is the same as that of what was demonstrated by the term of the above-mentioned (benzimidazole type compound), detailed description and illustration are abbreviate | omitted. When p is 2 or more, R ³¹ may be the same or different.

Among the above-mentioned embodiment also, pyridine compound as a nitrogen-containing heteroaromatic compound according to the present invention, in the general formula (III), R ³¹ are each independently a substituted or unsubstituted C 1-10 And an alkyl group, amino group, monoalkylamino group or dialkylamino group, and p is preferably a pyridine compound represented by the formula:

  Pyridine compounds preferably used in the present invention include, for example, 2-methylpyridine, 4-methylpyridine, 2-aminopyridine, 2,3-diaminopyridine, 2,6-diaminopyridine, 3,4-diaminopyridine, 3,5-diaminopyridine and the like can be mentioned. Of these, 2-methylpyridine (a compound represented by the following chemical formula 9), 2-aminopyridine (a compound represented by the following chemical formula 10), and the like are preferable.

  The said pyridine type compound may be used individually by 1 type, and may use 2 or more types together.

(Pyrazine compounds)
In the present invention, the pyrazine compound used as the nitrogen-containing heteroaromatic compound is a compound having a pyrazine skeleton.

  Here, the pyrazine-based compound is preferably a compound represented by the following general formula (IV). That is, the nitrogen-containing heteroaromatic compound has the following general formula (IV):

In the general formula (IV),
R ⁴¹ each independently represents a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, a substituted or unsubstituted cycloalkyl group having 3 to 20 carbon atoms, or a substituted or unsubstituted alkenyl group having 2 to 20 carbon atoms. Group, substituted or unsubstituted alkynyl group having 2 to 20 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 20 carbon atoms, substituted or unsubstituted aryl group having 6 to 30 carbon atoms, substituted or unsubstituted carbon An aryloxy group having 6 to 20 amino acids, a substituted or unsubstituted monoalkylamino group having 1 to 20 carbon atoms, a substituted or unsubstituted dialkylamino group having 2 to 20 carbon atoms, a thiol group (-SH) or A carboxyl group,
q is an integer of 0 to 4,
It is preferable that it is the pyrazine compound shown by these.

Since each said substituent is the same as that of what was demonstrated by the term of the above-mentioned (benzimidazole type compound), detailed description and illustration are abbreviate | omitted. When q is 2 or more, R ⁴¹ may be the same or different.

Among the forms described above, the pyrazine-based compound as the nitrogen-containing heteroaromatic compound according to the present invention is the above general formula (IV), wherein R ⁴¹ is independently a substituted or unsubstituted C 1-10. It is preferable that it is the pyrazine compound shown by these which are the alkyl group of this, an amino group, a monoalkylamino group, or a dialkylamino group, and q is an integer of 1-2.

  Examples of the pyrazine compound preferably used in the present invention include 2-methylpyrazine, 2-ethylpyrazine, 2-aminopyrazine, 2,6-dimethylpyrazine, 2,3-diaminopyrazine, 2,5-diaminopyrazine, 2,6-diaminopyrazine and the like can be mentioned. Of these, 2,6-dimethylpyrazine (a compound represented by the following chemical formula 11), 2-aminopyrazine (a compound represented by the following chemical formula 12), and the like are preferable.

  The said pyrazine type compound may be used individually by 1 type, and may use 2 or more types together.

  As mentioned above, although what was preferable as a nitrogen-containing heteroaromatic compound used in this invention was demonstrated, in this invention, a nitrogen-containing heteroaromatic compound is selected from the group which consists of a compound shown by the following Chemical formula 1-12, for example It is particularly preferable to include any one of the above.

  Among the nitrogen-containing heteroaromatic compounds, those containing an imidazole skeleton are particularly preferable from the viewpoint that the effect of suppressing color tone fluctuation is high. Since the compound having an imidazole skeleton is polarized, it is presumed that the compound easily receives electrons from the titanium oxide particles and has a high effect of suppressing coloring (color tone fluctuation) of the titanium oxide particles. In the present specification, a form in which a certain compound “includes an imidazole skeleton” may further include a form “including a benzimidazole skeleton” or a form in which the main skeleton includes another imidazole skeleton.

  Furthermore, the nitrogen-containing heteroaromatic compound preferably contains a benzimidazole skeleton. Since the benzimidazole skeleton is a skeleton in which a benzene ring is condensed to the imidazole skeleton, polarization is further increased as compared with an imidazole skeleton in which a benzene ring is not condensed. In addition, when the benzimidazole skeleton receives electrons, the electrons are likely to be resonantly stabilized by the benzene ring. Therefore, the benzimidazole compound can easily receive electrons from the titanium oxide particles, and thus can more effectively suppress coloring (color tone fluctuation).

  Specific examples of the nitrogen-containing heteroaromatic compound suitably used in the present invention include the compounds of the above chemical formulas 1 to 12, but from the viewpoint of availability, the effect of suppressing color fluctuation, and water solubility. In particular, the compounds represented by the chemical formulas 1 to 8 are preferable. In addition, the said compound may be used individually by 1 type, and may use 2 or more types together.

<Water-soluble resin>
In the optical reflective film of the present invention, the high refractive index layer contains a water-soluble resin as a binder together with the titanium oxide particles and the nitrogen-containing heteroaromatic compound. Further, it is preferable that the low refractive index layer contains a water-soluble resin. The water-soluble resin contained in the low refractive index layer is not particularly limited, and examples thereof include water-soluble resins, silicone resins, olefin resins, vinyl chloride resins, fluorine-containing polymers, and the like. Can be used, which is preferable in that it does not cause corrosion, dissolution, or permeation of the base material described later. In addition, the water-soluble resin is preferable because it has high flexibility and thus improves the durability of the optical reflection layer when bent. Further, from the viewpoint of production efficiency and the like, it is preferable that the low refractive index layer contains a water-soluble resin as well as the high refractive index layer. The water-soluble resin contained in the high refractive index layer may be the same as or different from the resin contained in the low refractive index layer. Hereinafter, the water-soluble resin will be described.

  In the present invention, the water-soluble resin is not particularly limited, and examples thereof include synthetic water-soluble resins such as polyvinyl alcohols and polyvinyl pyrrolidones; natural water-soluble resins such as gelatin and thickening polysaccharides. Among these, it is preferable to use polyvinyl alcohols from the viewpoint of low oxygen permeability and suppressing the photocatalytic action of titanium oxide contained in the high refractive index layer.

  Polyvinyl alcohols include, in addition to ordinary polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol having an anionic group such as a carboxyl group, nonionic group Also included are modified polyvinyl alcohols such as nonionic modified polyvinyl alcohol having a silyl group and silyl modified polyvinyl alcohol having a silyl group.

  The polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate preferably has an average polymerization degree of 200 or more, more preferably 1,000 or more, and an average polymerization degree of 1,500 to 5,000. More preferably, those of 2,000 to 5,000 are particularly preferably used. This is because when the polymerization degree of polyvinyl alcohol is 200 or more, the coating film does not crack, and when it is 5,000 or less, the coating solution is stabilized. In addition, that the coating solution is stable means that the coating solution is stabilized over time. The same applies hereinafter.

  The saponification degree is preferably 70 to 100%, more preferably 80 to 99.5% in view of solubility in water.

  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 a 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. Block copolymer of vinyl compound having a hydrophobic group and vinyl alcohol, silanol-modified polyvinyl alcohol having silanol group, reactive group modification having reactive group such as acetoacetyl group, carbonyl group, carboxyl group Polyvinyl alcohol etc. are mentioned.

  These polyvinyl alcohols may be used alone or in combination of two or more such as the degree of polymerization and the type of modification. As the polyvinyl alcohols, commercially available products or synthetic products may be used. Examples of commercially available products include, for example, PVA-102, PVA-103, PVA-105, PVA-110, PVA-117, PVA-120, PVA-124, PVA-135, PVA-203, PVA-205, PVA -210, PVA-217, PVA-220, PVA-224, PVA-235, etc. Poval (registered trademark, manufactured by Kuraray Co., Ltd.), EXEVAL (registered trademark, manufactured by Kuraray Co., Ltd.), Nichigo G polymer (registered trademark, Japan) Synthetic Chemical Industry Co., Ltd.).

  The content of polyvinyl alcohol in the refractive index layer is preferably from 3 to 70% by mass, more preferably from 5 to 60% by mass, even more preferably from 10 to 50% by mass, particularly preferably based on the total solid content of the refractive index layer. Is 13-45 mass%.

(Curing agent)
In the present invention, the refractive index layer may use a curing agent. When polyvinyl alcohol is used as the binder resin, the effect can be exhibited particularly.

  The curing agent that can be used with polyvinyl alcohol is not particularly limited as long as it causes a curing reaction with polyvinyl alcohol, but boric acid and its salts, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether. 1,6-diglycidylcyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.), aldehyde-based curing agents (formaldehyde, glycoxal, etc.), active halogen-based curing agents ( 2,4-dichloro-4-hydroxy-1,3,5, -s-triazine, etc.), active vinyl compounds (1,3,5-trisacryloyl-hexahydro-s-triazine, bisvinylsulfonylmethyl ether, etc.) A Miniumu alum, borax, and the like.

  The total amount of the curing agent used is preferably 10 to 600 mg per 1 g of polyvinyl alcohol (the total amount when polyvinyl alcohol is used), and more preferably 20 to 500 mg.

(Surfactant)
The high refractive index layer and the low refractive index layer according to the present invention preferably contain a surfactant from the viewpoint of coatability.

  Anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like can be used as the surfactant used for adjusting the surface tension during coating, but amphoteric surfactants are more preferable.

  Examples of amphoteric surfactants preferably used in the present invention include admisulfobetaine type, carboxybetaine type, sulfobetaine type, and imidazolium type. Specific examples of the amphoteric surfactant preferably used in the present invention are shown below. In the present invention, the sulfobetaine type is preferable from the viewpoint of coating unevenness, and examples of the product include LSB-R, LSB (manufactured by Kawaken Fine Chemical Co., Ltd.), and Amphitol 20HD (manufactured by Kao Corporation).

  The content of the surfactant in the refractive index layer according to the present invention is preferably 0.001 to 1% by mass, and 0.005 to 0.50% by mass with respect to the total solid content of the refractive index layer. More preferably.

(Other additives)
Examples of the high refractive index layer or the low refractive index layer according to the present invention include ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476. 57-74192, 57-87989, 60-72785, 61-14659, JP-A-1-95091, JP-A-3-13376, and the like Fluorescent whitening agents and sulfuric acid described in JP-A-59-42993, JP-A-59-52689, JP-A-62-280069, JP-A-61-228771 and JP-A-4-219266 PH adjusters such as phosphoric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, lubricants such as diethylene glycol, preservatives, Antistatic agents, may contain various known additives such as a matting agent.

(Titanium oxide particles used for high refractive index layer)
In the optical reflective film of the present invention, the high refractive index layer contains titanium oxide particles. Thus, the high refractive index layer containing titanium oxide particles is transparent and can express a higher refractive index. In the present invention, titanium oxide means titanium dioxide (TiO ₂ ).

  Titanium oxide contained in the titanium oxide particles includes those having a crystal structure such as rutile type (tetragonal type), anatase type, brookite type, etc., but the rutile type shows a particularly high refractive index. In addition, particles containing rutile titanium oxide have low photocatalytic activity compared to particles containing anatase or brookite type titanium oxide, so the weather resistance of the high refractive index layer and the adjacent low refractive index layer is high. Further, there is an advantage that the refractive index becomes higher. Therefore, it is preferable that a titanium oxide contains a rutile type titanium oxide. On the other hand, rutile-type titanium oxide is more prominently bluish by ultraviolet irradiation than other crystal structures, but according to the present invention, such rutile-type titanium oxide is also effectively suppressed from bluing. can do.

  The size of the titanium oxide particles contained in the high refractive index layer is not particularly limited, but can be determined by the volume average particle size or the primary average particle size. The volume average particle diameter of the titanium oxide particles used in the high refractive index layer is preferably 100 nm or less, more preferably 1 to 100 nm, and further preferably 3 to 50 nm. The primary average particle diameter of the titanium oxide particles used in the high refractive index layer is preferably 100 nm or less, more preferably 1 to 100 nm, and further preferably 3 to 50 nm. A volume average particle size or primary average particle size of 1 nm or more and 100 nm or less is preferred from the viewpoint of low haze and excellent visible light transmittance.

  In addition, the volume average particle size referred to in this specification is a method of observing the particles themselves using a laser diffraction scattering method, a dynamic light scattering method, or an electron microscope, or particles appearing on the cross section or surface of the refractive index layer. The particle diameter of 1,000 arbitrary particles is measured by a method of observing an image with an electron microscope, and particles having particle diameters of d1, d2,. Ni: In a group of nk particles, when the volume per particle is vi, the volume average particle diameter mv = {Σ (vi · di)} / {Σ (vi)} The average particle size weighted by the volume to be calculated is calculated.

  In the present specification, the primary average particle diameter can be measured from an electron micrograph taken with a transmission electron microscope (TEM) or the like. You may measure by the particle size distribution meter etc. which utilize a dynamic light scattering method, a static light scattering method, etc.

  When obtained from a transmission electron microscope, the primary average particle diameter of the particles is observed with an electron microscope on the particles themselves or the cross section or surface of the refractive index layer, and the particle diameter of 1000 arbitrary particles is measured. It is obtained as its 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.

  Further, as the titanium oxide particles, it is preferable to use particles obtained by modifying the surface of an aqueous titanium oxide sol so that it can be dispersed in an organic solvent or the like.

  As a method for preparing the aqueous titanium oxide sol, any conventionally known method can be used. For example, JP-A-63-17221, JP-A-7-819, JP-A-9-165218, Refer to the matters described in Kaihei 11-43327, JP-A-63-17221, JP-A-7-819, JP-A-9-165218, JP-A-11-43327, etc. it can.

  As for other methods for producing titanium oxide particles, for example, “Titanium oxide—physical properties and applied technology”, Kiyono Manabu, p. 255-258 (2000), Gihodo Publishing Co., Ltd., or paragraph number “0011” of WO2007 / 039953. The method of the step (2) described in “˜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.

Furthermore, as another method for producing inorganic oxide particles including titanium oxide particles, JP-A-2000-053421 (in which alkyl silicate is blended as a dispersion stabilizer, silicon in the alkyl silicate is changed to SiO _{2 is used.} Weight ratio (SiO ₂ / TiO ₂ ) of the amount converted to TiO ₂ and the amount converted to TiO ₂ in the titanium oxide is 0.7 to 10), JP 2000-063119 A (TiO ₂ -ZrO ₂ -SnO ₂ composite colloidal particles as the core, and the surface thereof coated with the composite oxide colloidal particles of WO ₃ -SnO ₂ -SiO ₂ ) can be referred to. .

  Furthermore, a form of core-shell particles in which titanium oxide particles are coated with a silicon-containing hydrated oxide is preferable. Here, “coating” means a state in which a silicon-containing hydrated oxide is attached to at least a part of the surface of the titanium oxide particles. In this specification, “silica-attached titanium dioxide” or “ Also referred to as “silica-coated titanium oxide”. That is, the surface of the titanium oxide particles may be completely covered with the silicon-containing hydrated oxide, or a part of the surface of the titanium oxide particles may be covered with the silicon-containing hydrated oxide. From the viewpoint that the refractive index of the coated titanium oxide particles is controlled by the coating amount of the silicon-containing hydrated oxide, it is preferable that a part of the surface of the titanium oxide particles is coated with the silicon-containing hydrated oxide. . By containing the core-shell particles in the high refractive index layer, the high refractive index layer is obtained by the interaction between the silicon-containing hydrated oxide of the shell layer and the resin (preferably polyvinyl alcohol) constituting the high refractive index layer. There is an effect of suppressing interlayer mixing between the low refractive index layer and the low refractive index layer.

  The titanium oxide of the titanium oxide particles coated with the silicon-containing hydrated oxide may be a rutile type, an anatase type, or a brookite type. The titanium oxide particles coated with a silicon-containing hydrated oxide are more preferably rutile-type titanium oxide particles coated with a silicon-containing hydrated oxide. This is because the rutile type titanium oxide particles have lower photocatalytic activity than the anatase type titanium oxide particles, so that the weather resistance of the high refractive index layer and the adjacent low refractive index layer is increased, and the refractive index is further increased. Because. In the present specification, the “silicon-containing hydrated oxide” may be any of a hydrate of an inorganic silicon compound, a hydrolyzate and / or a condensate of an organosilicon compound, and in order to reduce photocatalytic activity, silanol It is more preferable to have a group. Therefore, in the present invention, the high refractive index metal oxide fine particles are preferably silica-modified (silanol-modified) titanium oxide particles in which the titanium oxide particles are silica-modified. That is, in the present invention, the high refractive index layer preferably contains a water-soluble resin such as polyvinyl alcohol, silica-modified (silanol-modified) titanium oxide particles, and a nitrogen-containing heteroaromatic compound.

  On the other hand, the present inventors have also found that when silica-modified titanium oxide particles are used, bluening due to ultraviolet irradiation is more likely to occur when silica-modified titanium oxide particles are used. Therefore, for the purpose of suppressing bluening, it can be said that the titanium oxide particles are preferably not coated with a silicon-containing hydrated oxide. According to the present invention, the silica-modified titanium oxide particles as described above are used. Even if it is a case where blue is used, blueening can be suppressed effectively. And since the silica modified titanium oxide particle has low photocatalytic activity, an optical reflective film excellent in durability can be obtained. Therefore, in the present invention, it is preferable to use silica-modified titanium oxide particles as the titanium oxide particles in order to achieve both the effect of improving the durability and suppressing the color tone fluctuation.

  The coating amount of the silicon-containing hydrated oxide is 3 to 30% by mass, preferably 3 to 10% by mass, and more preferably 3 to 8% by mass with respect to the total amount of titanium oxide serving as the core. When the coating amount is 30% by mass or less, the desired refractive index of the high refractive index layer can be obtained. On the other hand, if the coating amount is 3% by mass or more, not only can the particles be stably formed, but also the surface of the titanium oxide is suppressed from being in physical contact with the resin contained in the high refractive index layer. The deterioration of the resin can be suppressed.

  As a method of coating the titanium oxide particles with a silicon-containing hydrated oxide, it can be produced by a conventionally known method. For example, JP-A-10-158015, JP-A-2000-204301, JP-A-2007 In addition, a compound having a complexing action with respect to organoalkoxysilane or titanium oxide of No. 246351 is added, and it is added to a sodium silicate or silica sol solution in an alkaline region. Reference can be made to the matters described in, for example, the method for producing a coated titanium oxide hydrosol.

  The core-shell particle according to the present invention may be one in which the entire surface of the titanium oxide particle as the core is coated with a silicon-containing hydrated oxide, and a part of the surface of the titanium oxide particle as the core is covered with a silicon-containing water. What coated with the sum oxide may be used.

  At this time, the size of the titanium oxide particles coated with the silicon-containing hydrated oxide is not particularly limited, but is in the same range as the volume average particle size and primary average particle size of the titanium oxide particles. And preferred. That is, the volume average particle diameter of the silica-modified (silanol-modified) titanium oxide particles contained in the high refractive index layer is preferably 100 nm or less, more preferably 1 to 100 nm, and further preferably 3 to 50 nm. The primary average particle diameter of the titanium oxide particles used in the high refractive index layer is preferably 100 nm or less, more preferably 1 to 100 nm, and further preferably 3 to 50 nm. Here, in the case of the titanium oxide particles coated with the silicon-containing hydrated oxide, the volume average particle size or primary average particle size is that of the titanium oxide particles (not coated with the silicon-containing hydrated oxide). Volume average particle diameter or primary average particle diameter is indicated respectively.

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

  The content of the titanium oxide particles in the high refractive index layer is not particularly limited, but is preferably 15 to 95% by mass and more preferably 20 to 90% by mass with respect to the total solid content of the high refractive index layer. Preferably, it is further more preferable in it being 30-90 mass%. By setting it as the said range, it can be set as a favorable optical reflection characteristic.

(Inorganic oxide particles used in the high refractive index layer)
In the optical reflective film according to the present invention, in order to form a high refractive index layer having a high refractive index, in addition to titanium oxide particles, the high refractive index layer includes zirconia, tin oxide, zinc oxide, alumina, colloidal. Inorganic oxide particles (high refractive index metal oxide fine particles) such as alumina, niobium oxide, europium oxide and zircon may be contained. Of these, the inorganic oxide particles contained in addition to the titanium oxide particles preferably contain zirconia. In addition, the high refractive index metal oxide fine particles other than the titanium oxide may be used alone or in combination of two or more kinds in order to adjust the refractive index. The size of the high refractive index metal oxide fine particles other than the titanium oxide is not particularly limited, but the volume average particle size is preferably 1 to 100 nm or less, and more preferably 3 to 50 nm. The primary average particle size is preferably 1 to 100 nm or less, and more preferably 3 to 50 nm. The content of the high refractive index metal oxide fine particles in the high refractive index layer is not particularly limited, but the sum of the content of titanium oxide particles and the content of high refractive index metal oxide fine particles is the high refractive index. It is preferably adjusted to 15 to 85% by mass relative to the total solid content of the layer, more preferably 20 to 80% by mass, and even more preferably 30 to 80% by mass.

(Inorganic oxide particles in the low refractive index layer)
In the optical reflective film of the present invention, the low refractive index layer preferably contains inorganic oxide particles. Silica (silicon dioxide) is preferably used as the inorganic oxide particles, and specific examples include synthetic amorphous silica, colloidal silica, zinc oxide, alumina, colloidal alumina, and the like. Of these, colloidal silica sol, particularly acidic colloidal silica sol is more preferably used, and colloidal silica dispersed in water or an aqueous solvent is particularly preferably used. In order to further reduce the refractive index, hollow fine particles having pores inside the particles may be used as the inorganic oxide particles of the low refractive index layer, and silica (silicon dioxide) hollow fine particles are particularly preferable. Moreover, well-known inorganic oxide particles other than a silica can also be used. In order to adjust the refractive index, the inorganic oxide particles contained in the low refractive index layer may be used singly or in combination of two or more.

  The average particle size of primary particles of silicon dioxide dispersed in a primary particle state (particle size in a dispersion state before coating) is more preferably 1 to 50 nm, and further preferably 3 to 40 nm. 3 to 20 nm is particularly preferable, and 4 to 10 nm is most preferable. Moreover, as an average particle diameter of secondary particle | grains, it is preferable from a viewpoint with few hazes and excellent visible light transmittance | permeability that it is 30 nm or less.

  Moreover, the particle diameter of the inorganic oxide particles of the low refractive index layer can be determined by the volume average particle diameter in addition to the primary average particle diameter.

  The colloidal silica used in the present invention is obtained by heating and aging a silica sol obtained by metathesis with an acid of sodium silicate or the like and passing through an ion exchange resin layer. For example, JP-A-57-14091, JP-A-60-219083, JP-A-60-219084, JP-A-61-20792, JP-A-61-188183, JP-A-63-17807, JP-A-4-93284 No. 5, JP-A-5-278324, JP-A-6-92011, JP-A-6-183134, JP-A-6-297830, JP-A-7-81214, JP-A-7-101142. Disclosed in JP-A-7-179029, JP-A-7-137431, and International Publication No. 94/26530. It is.

  Such colloidal silica may be a synthetic product or a commercially available product. Examples of commercially available products include the Snowtex series (Snowtex OS, OXS, S, OS, 20, 30, 40, O, N, C, etc.) sold by Nissan Chemical Industries.

  The surface of the colloidal silica may be cation-modified, or may be treated with Al, Ca, Mg, Ba or the like.

  The content of the inorganic oxide particles in the low refractive index layer is preferably 20 to 90 mass%, more preferably 30 to 85 mass%, based on the total solid content of the low refractive index layer. More preferably, it is -80 mass%. When it is 20% by mass or more, a desired refractive index is obtained, and when it is 90% by mass or less, the coatability is good, which is preferable.

  The inorganic oxide particles of the low refractive index layer may be contained in at least one layer when a plurality of low refractive index layers are present.

(Base material)
The optical reflective film according to the present invention includes a base material for supporting the high refractive index layer and the low refractive index layer. As the substrate of the optical reflection film, various resin films can be used. Polyolefin film (polyethylene, polypropylene, etc.), polyester film (polyethylene terephthalate (PET), polyethylene naphthalate, etc.), polyvinyl chloride, cellulose acetate Etc., and a polyester film is preferable. 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 thickness of the base material used in the present invention is preferably 10 to 300 μm, particularly 20 to 150 μm. In addition, two substrates may be stacked, and in this case, the type may be the same or different.

  The base material preferably has a visible light region transmittance of 85% or more as shown in JIS R3106 (1998), particularly preferably 90% or more. It is advantageous in that the transmittance in the visible light region shown in JIS R3106 (1998) is 50% or more (upper limit: 100%) when the base material is at least the above transmittance. It is preferable.

[Method for producing optical reflective film]
The method for producing an optical reflective film of the present invention can be used by any method as long as at least one unit composed of the high refractive index layer and the low refractive index layer can be formed on the substrate. Can be.

  In the method for producing an optical 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 substrate.

  Specifically, it is preferable to form a laminate by alternately applying and drying a high refractive index layer and a low refractive index layer. Specific examples include the following: (1) A high refractive index layer coating solution is applied onto a substrate and dried to form a high refractive index layer, and then a low refractive index layer coating solution is applied and dried. Forming a low refractive index layer and forming an optical reflective film; (2) applying a low refractive index layer coating solution on a substrate and drying to form a low refractive index layer; A method of forming a high refractive index layer by applying a layer coating solution and drying to form an optical reflective film; (3) alternating a high refractive index layer coating solution and a low refractive index layer coating solution on a substrate A method of forming an optical reflective film comprising a high refractive index layer and a low refractive index layer; (4) a high refractive index layer coating solution and a low refractive index layer; A method of forming an optical reflective film including a high refractive index layer and a low refractive index layer by simultaneously applying a coating layer with a coating solution and drying;Among these, the method (4), which is a simpler manufacturing process, is preferable. That is, it is preferable that the method for producing an optical reflective film of the present invention includes laminating the high refractive index layer and the low refractive index layer by an aqueous simultaneous multilayer coating method.

  In the present invention, in order to form a high refractive index layer, the high refractive index layer coating solution contains the water-soluble resin, titanium oxide particles, and a nitrogen-containing heteroaromatic compound. Therefore, the method for producing an optical reflective film is a method for producing an optical reflective film comprising at least one unit in which a low refractive index layer and a high refractive index layer are laminated on a substrate, comprising a water-soluble resin, titanium oxide Applying a coating solution prepared by adding particles and a nitrogen-containing heteroaromatic compound.

  Further, when preparing the coating solution, the nitrogen-containing heteroaromatic compound may be added in the form of a solid or in the form of a solution. In addition, since a nitrogen-containing heteroaromatic compound was mentioned above, detailed description is abbreviate | omitted here.

  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.

  The solvent for preparing the high refractive index layer coating solution and the low refractive index layer coating solution is not particularly limited, but water, an organic solvent, or a mixed solvent thereof is preferable. In the present invention, it is preferable to mainly use polyvinyl alcohol as the resin binder, but by using polyvinyl alcohol as described above, application with an aqueous solvent becomes possible. Furthermore, in the present invention, a nitrogen-containing heteroaromatic compound is added to the coating solution in order to suppress color tone fluctuations and cracks, but it is also preferable to use a nitrogen-containing heteroaromatic compound having high water solubility. Compared to the case where an organic solvent is used, the aqueous solvent does not require a large-scale production facility, so that it is preferable in terms of productivity and also in terms of environmental conservation.

  Examples of the organic solvent include alcohols such as methanol and ethanol, esters such as ethyl acetate, butyl acetate and propylene glycol monomethyl ether acetate, ethers such as diethyl ether and propylene glycol monomethyl ether, and amides such as dimethylformamide. , Ketones such as acetone and methyl ethyl ketone. These organic solvents may be used alone or in combination of two or more. From the viewpoint of environment and simplicity of operation, the solvent of the coating solution is preferably an aqueous solvent, more preferably water or a mixed solvent of water and methanol, ethanol, or ethyl acetate, and water is particularly preferable.

  When using a mixed solvent of water and a small amount of organic solvent, the content of water in the mixed solvent is preferably 80 to 99.9% by mass, based on 100% by mass of the entire mixed solvent, and is preferably 85 to 99%. More preferably, it is 5 mass%. Here, by setting it to 80% by mass or more, volume fluctuation due to solvent volatilization can be reduced, handling is improved, and by setting it to 99.9% by mass or less, homogeneity at the time of liquid addition is increased and stable. This is because the obtained liquid properties can be obtained.

The concentration of the water-soluble resin in the high refractive index layer coating solution (when using a plurality of types of resins, the total concentration) is preferably 0.5 to 10% by mass. Moreover, it is preferable that the density | concentration of the inorganic oxide particle (a titanium oxide particle is included) in a high refractive index layer coating liquid is 1-50 mass%. Furthermore, the concentration of the nitrogen-containing heteroaromatic compound in the high refractive index layer coating solution is preferably 1 × 10 ^{−3 to} 5% by mass, and more preferably 5 × 10 ^{−3 to} 3% by mass. .

  The concentration of the resin in the low refractive index layer coating solution is preferably 0.5 to 10% by mass. Moreover, it is preferable that the density | concentration of the inorganic oxide particle in a low refractive index layer coating liquid is 1-50 mass%.

  The method for preparing the high refractive index layer coating solution and the low refractive index layer coating solution is not particularly limited. For example, inorganic oxide particles containing titanium oxide particles, water-soluble resin, nitrogen-containing heteroaromatic compound, and further if necessary The other additive added by adding and stirring and mixing may be mentioned. At this time, the order of addition of the respective components is not particularly limited, and the respective components may be sequentially added and mixed while stirring, or may be added and mixed at one time while stirring.

  In the present invention, when simultaneous multilayer coating is performed, it is preferable that the saponification degree of polyvinyl alcohol used in the high refractive index layer coating solution and the low refractive index layer coating solution is different. Due to the different saponification degrees, mixing of layers can be suppressed in each step of coating and drying. Although this mechanism is not yet clear, it is thought that mixing is suppressed by the difference in surface tension derived from the difference in saponification degree. In the present invention, the difference in the degree of saponification of the polyvinyl alcohol used in the high refractive index layer coating solution and the low refractive index layer coating solution is preferably 3 mol% or more, more preferably 8 mol% or more. That is, the difference between the saponification degree of the high refractive index layer and the saponification degree of the low refractive index layer is preferably 3 mol% or more, and more preferably 8 mol% or more. The upper limit of the difference between the saponification degree of the high refractive index layer and the saponification degree of the low refractive index layer is preferably as high as possible in view of the effect of suppressing / preventing interlayer mixing between the high refractive index layer and the low refractive index layer. Although not limited, it is preferably 20 mol% or less, and more preferably 15 mol% or less.

  When comparing the difference in saponification degree in each refractive index layer, when each refractive index layer contains a plurality of polyvinyl alcohols (different in saponification degree and polymerization degree), the highest content of polyvinyl alcohol in the refractive index layer Compare alcohol. Here, when the phrase “polyvinyl alcohol having the highest content in the refractive index layer” is used, the degree of polymerization is calculated assuming that the polyvinyl alcohol having a saponification degree difference of 3 mol% or less is the same polyvinyl alcohol. Specifically, when polyvinyl alcohol having a saponification degree of 90 mol%, a saponification degree of 91 mol%, and a saponification degree of 93 mol% is contained in the same layer by 10 mass%, 40 mass%, and 50 mass%, respectively. These three polyvinyl alcohols are the same polyvinyl alcohol, and the mixture of these three is polyvinyl alcohol (A) or (B). The saponification degree of this polyvinyl alcohol (A) / (B) is (90 × 0 1 + 91 × 0.4 + 93 × 0.5) /1=91.9 mol%. The “polyvinyl alcohol having a saponification degree difference of 3 mol% or less” is not more than 3 mol% when attention is paid to any polyvinyl alcohol. For example, 90, 91, 92, 94 mol% In the case where the vinyl alcohol is included, since all the polyvinyl alcohols are within 3 mol% when focusing on 91 mol% vinyl alcohol, the same polyvinyl alcohol is obtained.

  When polyvinyl alcohol having a saponification degree different by 3 mol% or more is contained in the same layer, it is regarded as a mixture of different polyvinyl alcohols, and the polymerization degree and the saponification degree are respectively calculated.

  For example, PVA203: 5% by mass, PVA117: 25% by mass, PVA217: 10% by mass, PVA220: 10% by mass, PVA224: 10% by mass, PVA235: 20% by mass, PVA245: 20% by mass, most contained A large amount of PVA is a mixture of PVA 217 to 245 (the difference in the degree of saponification of PVA 217 to 245 is within 3 mol%, which is the same polyvinyl alcohol), and this mixture becomes polyvinyl alcohol (A) or (B). In the mixture of PVA 217 to 245 (polyvinyl alcohol (A) / (B)), the degree of polymerization is (1700 × 0.1 + 2000 × 0.1 + 2400 × 0.1 + 3500 × 0.2 + 4500 × 0.2) / 0. .7 = 3200, and the degree of saponification is 88%.

  The viscosities of the high refractive index layer coating solution and the low refractive index layer coating solution when performing simultaneous multilayer coating are not particularly limited. However, when the slide bead coating method is used, the preferable temperature range of the coating liquid is preferably in the range of 5 to 160 mPa · s, more preferably in the range of 60 to 140 mPa · s. Moreover, when using a curtain application | coating system, in the preferable temperature range of said coating liquid, the range of 5-1200 mPa * s is preferable, More preferably, it is the range of 25-500 mPa * s. If it is the range of such a viscosity, simultaneous multilayer coating can be performed efficiently.

  The conditions for the coating and drying method are not particularly limited. For example, in the case of a sequential coating method, first, either one of a high refractive index layer coating solution and a low refractive index layer coating solution heated to 30 to 60 ° C. is used. After coating and drying on a substrate to form a layer, the other coating solution is coated on this layer and dried to form a laminated film precursor (unit). Next, the number of units necessary for expressing the desired shielding performance is successively applied and dried by the above method to obtain a laminated film precursor. When drying, it is preferable to dry the formed coating film at 30 ° C. or higher. For example, it is preferable to dry in the range of 5-50 ° C. wet bulb temperature and 5-100 ° C. (preferably 10-50 ° C.) film surface temperature. For example, warm air of 40-60 ° C. is blown for 1-5 seconds. dry. As a drying method, warm air drying, infrared drying, and microwave drying are used. Further, drying in a multi-stage process is preferable to drying in a single process, and it is more preferable to set the temperature of the constant rate drying section <the temperature of the rate-decreasing drying section. In this case, the temperature range of the constant rate drying part is preferably 30 to 60 ° C., and the temperature range of the decreasing rate drying part is preferably 50 to 100 ° C.

  Moreover, the conditions of the coating and drying method when performing simultaneous multilayer coating are as follows: the high refractive index layer coating solution and the low refractive index layer coating solution are heated to 30 to 60 ° C., and the high refractive index layer coating is applied on the substrate. After the simultaneous multi-layer coating of the liquid and the low refractive index layer coating liquid, the temperature of the formed coating film is preferably cooled (set) preferably to 1 to 15 ° C. and then dried at 10 ° C. or higher. More preferable drying conditions are a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10 to 50 ° C. For example, 40-80 degreeC warm air is sprayed for 1 to 5 seconds, and it dries. 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 uniformity improvement of the formed coating film.

  Here, the set means that the viscosity of the coating composition is increased by means such as lowering the temperature by applying cold air or the like to the coating film, the fluidity of the substances in each layer and in each layer is reduced, or the gel It means the process of converting. A state in which the cold air is applied to the coating film from the surface and the finger is pressed against the surface of the coating film is defined as a set completion state.

  The time (setting time) from the time of application to the completion of setting by applying cold air is preferably within 5 minutes, and more preferably within 2 minutes. Further, the lower limit time is not particularly limited, but it is preferable to take 45 seconds or more.

  The adjustment of the set time is such as adjusting the concentration of polyvinyl alcohol, the concentration of inorganic oxide particles and nitrogen-containing heteroaromatic compounds, various known gelling agents such as gelatin, pectin, agar, carrageenan, gellan gum, It can be adjusted by adding other components.

  What is necessary is just to apply | coat so that the coating thickness of a high refractive index layer coating liquid and a low refractive index layer coating liquid may become the thickness at the time of preferable drying as shown above.

[Membrane design]
The optical reflective film of the present invention includes at least one unit in which a high refractive index layer and a low refractive index layer are laminated. Preferably, it has a multilayer optical interference film in which a high refractive index layer and a low refractive index layer are alternately laminated on one side or both sides of a substrate. From the viewpoint of productivity, the range of the total number of high refractive index layers and low refractive index layers per side of the substrate is preferably 100 layers or less, more preferably 45 layers or less. The lower limit of the range of the total number of high refractive index layers and low refractive index layers per side of the substrate is not particularly limited, but is preferably 5 layers or more. As described above, when a plurality of units each including a plurality of high refractive index layers are stacked, a plurality of layers containing titanium oxide (high refractive index layers) are present, and thus the problem of coloring tends to be particularly noticeable. However, according to the present invention, since coloring of the high refractive index layer is effectively suppressed, even when a plurality of high refractive index layers and low refractive index layers are stacked as described above, the change in color tone is effective. Is suppressed. Furthermore, the optical reflective film of the present invention has a configuration in which high refractive index layers and low refractive index layers are alternately laminated. As described above, the result is that bluening of titanium oxide is suppressed in the high refractive index layer. The heat storage in the optical reflection layer is reduced. As a result, not only in the high refractive index layer but also in the adjacent low refractive index layer, color tone fluctuations and cracks due to resin deterioration are suppressed.

  The preferred range of the total number of high refractive index layers and low refractive index layers is applicable even when laminated on only one side of the substrate, and when laminated simultaneously on both sides of the substrate. Is also applicable. When laminated on both surfaces of the substrate, the total number of high refractive index layers and low refractive index layers on one surface of the substrate and the other surface may be the same or different. In the optical reflective film of the present invention, the lowermost layer (layer in contact with the substrate) and the outermost layer may be either a high refractive index layer or a low refractive index layer.

  In general, in an optical reflection film, it is preferable to design a large difference in refractive index between a high refractive index layer and a low refractive index layer from the viewpoint that the reflectance for a desired light beam can be increased with a small number of layers. . In the present invention, the difference in refractive index between at least two adjacent layers (high refractive index layer and low refractive index layer) is preferably 0.25 or more, more preferably 0.3 or more, and most preferably 0. .33 or more. The upper limit is not particularly limited, but is usually 1.4 or less.

  The refractive index difference and the required number of layers can be calculated using commercially available optical design software.

  The low refractive index layer preferably has a refractive index of 1.10 to 1.60, more preferably 1.30 to 1.50. The high refractive index layer preferably has a refractive index of 1.70 to 2.50, more preferably 1.80 to 1.90.

  The thickness (thickness after drying) per layer (excluding the lowermost layer and the outermost layer) of the refractive index layer is preferably 20 to 1000 nm, more preferably 50 to 500 nm, and more preferably 50 to 350 nm. It is more preferable. Moreover, it is preferable that the thickness (thickness after drying) of the refractive index layer of the lowest layer is 100-3000 nm, It is more preferable that it is 500-2000 nm, It is more preferable that it is 1000-1800 nm. The thickness of the outermost refractive index layer (thickness after drying) is preferably 1 to 100 nm, more preferably 5 to 50 nm, and more preferably 8 to 30 nm.

  The total thickness (including the substrate) of the optical reflective film of the present invention is preferably 12 μm to 315 μm, more preferably 15 μm to 200 μm, and still more preferably 20 μm to 100 μm.

One feature of the optical reflective film of the present invention is that the coloration of redness in the initial stage is small, and even when exposed to sunlight for a long time, the color tone hardly changes. Therefore, the color tone of the optical reflection film is preferably such that the value of a ^* in the L ^* a ^* b ^* color system is negative, more preferably −20 or more and less than −0.2, and −10 or more and 0 or less. Is particularly preferred. Further, the degree of change in color tone (ΔE) before and after exposure to light is preferably closer to 0, more preferably 0 or more and 6 or less, and even more preferably 0 or more and 3.5 or less. Furthermore, from the viewpoint of durability, it is preferable that film cracking and peeling after exposure are suppressed. In addition, said a ^* and (DELTA) E shall point out the value measured by the method of the Example.

[Layer structure of optical reflection film]
The optical reflection film includes at least one unit in which a high refractive index layer and a low refractive index layer are laminated on a base material. The unit may be formed only on one side of the substrate, or may be formed on both sides. Since the reflectance of a specific wavelength improves, it is preferable that this unit is formed on both surfaces of a base material.

  The optical reflective film is a conductive layer, an antistatic layer, a gas barrier layer, an easy-adhesion layer (adhesion layer) for the purpose of adding further functions under the base material or on the outermost surface layer opposite to the base material. Antifouling layer, deodorant layer, droplet layer, slippery layer, hard coat layer, abrasion resistant layer, antireflection layer, electromagnetic wave shielding layer, ultraviolet absorbing layer, infrared absorbing layer, printed layer, fluorescent light emitting layer, hologram layer , Peeling layer, adhesive layer, adhesive layer, infrared cut layer (metal layer, liquid crystal layer) other than the above high refractive index layer and low refractive index layer, colored layer (visible light absorbing layer), intermediate film used for laminated glass One or more functional layers such as layers may be included.

  The stacking order of the various functional layers described above in the reflective film is not particularly limited.

  For example, in the specification of attaching an optical reflection film to the indoor side of a window glass (internal bonding), an optical reflection layer and an adhesive layer including at least one unit in which the high refractive index layer and the low refractive index layer are laminated on the substrate surface A preferred example is a form in which a hard coat layer is coated on the base material surface on the side opposite to the side on which these layers are laminated. Moreover, the order may be an adhesive layer, a base material, an optical reflection layer, and a hard coat layer, and may further have another functional layer, a base material, or an infrared absorber. Moreover, if a preferable example is given also in the specification which affixes the optical reflection film of this invention on the outdoor side of a window glass (outside sticking), it will laminate | stack in order of an optical reflection layer and an adhesion layer on the base-material surface, and also these layers will be laminated | stacked. In this configuration, a hard coat layer is applied to the surface of the base material on the side opposite to the side. As in the case of the internal bonding, the order may be an adhesive layer, a base material, an optical reflection layer, and a hard coat layer, and may further have another functional layer base material or an infrared absorber. .

[Application of optical reflective film: Optical reflector]
The optical reflective film of the present invention can be applied to a wide range of fields. That is, according to another aspect of the present invention, there is provided an optical reflector in which the above-mentioned optical reflection film is provided on at least one surface of a substrate. For example, film for window pasting such as heat ray reflecting film that gives heat ray reflection effect, film for agricultural greenhouses, etc. Etc., mainly for the purpose of improving the weather resistance. In particular, it is suitable for a member in which the optical reflective film according to the present invention is bonded to a substrate such as glass or a glass substitute resin directly or via an adhesive.

  Specific examples of the substrate include, for example, glass, polycarbonate resin, polysulfone resin, acrylic resin, polyolefin resin, polyether resin, polyester resin, polyamide resin, polysulfide resin, unsaturated polyester resin, epoxy resin, melamine resin, and phenol. Examples thereof include resins, diallyl phthalate resins, polyimide resins, urethane resins, polyvinyl acetate resins, polyvinyl alcohol resins, styrene resins, vinyl chloride resins, metal plates, and ceramics. The type of resin may be any of a thermoplastic resin, a thermosetting resin, and an ionizing radiation curable resin, and two or more of these may be used in combination. The substrate can be produced by a known method such as extrusion molding, calendar molding, injection molding, hollow molding, compression molding or the like. The thickness of the substrate is not particularly limited, but is usually 0.1 mm to 5 cm.

  It is preferable that the adhesive layer or the adhesive layer that bonds the optical reflection film and the substrate is disposed on the sunlight (heat ray) incident surface side. Further, it is preferable to sandwich the optical reflection film between the window glass and the substrate because it can be sealed from surrounding gas such as moisture and has excellent durability. Even if the infrared shielding film according to the present invention is installed outdoors or outside a car (for external application), it is preferable because of environmental durability.

  It is preferable that the adhesive layer or the adhesive layer that bonds the optical reflection film and the substrate is installed so that the optical reflection film is on the sunlight (heat ray) incident surface side when bonded to a window glass or the like. Further, when the optical reflection film is sandwiched between the window glass and the base material, it can be sealed from ambient gas such as moisture, which is preferable for durability. Even if the optical reflective film of the present invention is installed outdoors or on the outside of a 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.

  The heat insulating performance and solar heat shielding performance of the optical reflecting film or optical reflector are generally JIS R 3209 (1998) (multi-layer glass), JIS R 3106 (1998) (transmittance / reflectance / emissivity of sheet glass). -Test method of solar heat gain rate), JIS R 3107 (1998) (calculation method of thermal resistance of plate glass and heat transmissivity in architecture).

  The solar transmittance, solar reflectance, emissivity, and visible light transmittance are measured by (1) using a spectrophotometer having a wavelength (300 to 2500 nm) to measure the spectral transmittance and spectral reflectance of various single plate glasses. Further, the emissivity is measured using a spectrophotometer having a wavelength of 5.5 to 50 μm. In addition, a predetermined value is used for the emissivity of float plate glass, polished plate glass, mold plate glass, and heat ray absorbing plate glass. (2) The solar transmittance, solar reflectance, solar absorption rate, and modified emissivity are calculated according to JIS R 3106 (1998) by calculating solar transmittance, solar reflectance, solar absorption rate, and vertical emissivity. The corrected emissivity is obtained by multiplying the coefficient shown in JIS R 3107 (1998) by the vertical emissivity. The heat insulation and solar heat shielding properties are calculated by (1) calculating the thermal resistance of the multilayer glass according to JIS R 3209 (1998) using the measured thickness value and the corrected emissivity. However, when the hollow layer exceeds 2 mm, the gas thermal conductance of the hollow layer is determined according to JIS R 3107 (1998). (2) The heat insulation is obtained by adding a heat transfer resistance to the heat resistance of the double-glazed glass and calculating the heat flow resistance. (3) The solar heat shielding property is calculated by calculating the solar heat acquisition rate according to JIS R 3106 (1998) and subtracting it from 1.

  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, "mass part" or "mass%" is represented. Unless otherwise specified, each operation is performed at room temperature (25 ° C.).

[Production Example 1: Production of high refractive index layer coating solution 1]
First, a titanium oxide sol dispersion containing rutile type titanium oxide was prepared.

(Preparation of silica-modified titanium oxide particle dispersion)
A dispersion of silica-modified titanium oxide particles (rutile type) was prepared as follows.

The titanium sulfate aqueous solution was thermally hydrolyzed by a known method to obtain titanium oxide hydrate. The obtained titanium oxide hydrate was suspended in water to obtain 10 L of an aqueous suspension of titanium oxide hydrate (TiO ₂ concentration: 100 g / L). To this, 30 L of an aqueous sodium hydroxide solution (concentration 10 mol / L) was added with stirring, the temperature was raised to 90 ° C., and the mixture was aged for 5 hours. The obtained solution was neutralized with hydrochloric acid, filtered and washed with water to obtain a base-treated titanium compound.

Next, the base-treated titanium compound was suspended in pure water and stirred so that the TiO ₂ concentration was 20 g / L. Under stirring, it was added citric acid in an amount of 0.4 mol% with respect to TiO ₂ weight. The temperature was raised to 95 ° C., concentrated hydrochloric acid was added so that the hydrochloric acid concentration was 30 g / L, and the solution temperature was maintained, followed by stirring for 3 hours. Here, when the pH and zeta potential of the obtained mixed liquid were measured, the pH at 25 ° C. was 1.4, and the zeta potential was +40 mV. Further, when the particle size was measured by Zetasizer Nano (manufactured by Malvern), the volume average particle size was 35 nm and the monodispersity was 16%. Further, the titanium oxide sol solution was dried at 105 ° C. for 3 hours to obtain a particle powder, and X-ray diffraction measurement was performed using JDX-3530 type manufactured by JEOL Datum Co., Ltd. to confirm that the particles were rutile type particles. did.

  1 kg of pure water was added to 1 kg of a 20.0 mass% titanium oxide sol aqueous dispersion containing the rutile-type titanium oxide particles to prepare a 10.0 mass% titanium oxide sol aqueous dispersion.

2 kg of pure water was added to 0.5 kg of the 10.0 mass% titanium oxide sol aqueous dispersion, followed by heating to 90 ° C. Thereafter, 0.1 kg of an aqueous silicic acid solution having a SiO ₂ concentration of 2.0 mass% was gradually added. The resulting dispersion is subjected to heat treatment at 175 ° C. for 18 hours in an autoclave, desalted using ultrafiltration, and further concentrated to contain titanium oxide having a rutile structure coated with SiO ₂ . A dispersion (sol water dispersion) of silica-modified titanium oxide particles of 20 mass% (mass ratio of titanium oxide excluding coated SiO ₂ ) was obtained. At this time, the coating amount of silica was 4% by mass with respect to the titanium oxide particles. Further, when the particle size of silica-modified titanium oxide particles (rutile type) was measured using Zetasizer Nano (manufactured by Malvern), the volume average particle size was 35 nm and the monodispersity was 16%.

(Preparation of high refractive index layer coating solution 1)
8 mass% of 5-amino-2-mercaptobenzimidazole (represented by the above chemical formula 1) with respect to 400 mass parts of the dispersion of 20 mass% of silica-modified titanium oxide particles (rutile type) obtained as described above. 50 parts by mass of an aqueous solution of the compound (the mass ratio of the oxidant to the titanium oxide particles (Ox / Ti) is 5% by mass), 8% by mass of a polyvinyl alcohol solution (PVA-110, polymerization degree 1000). 135 parts by mass of a saponification degree of 99 mol%, manufactured by Kuraray Co., Ltd., 135 parts by mass of a 6 mass% polyvinyl alcohol solution (PVA-120, polymerization degree of 2000, saponification degree of 99 mol%, manufactured by Kuraray Co., Ltd.), and 5 3% by mass of a surfactant solution (Amthal HD, manufactured by Kao Corporation) in mass% is added in order at 45 ° C., and finally 1000 parts by mass with pure water. The coating solution 1 was prepared. The refractive index of the high refractive index layer obtained by applying and drying the high refractive index layer coating solution 1 was 1.82. In addition, the measuring method of a refractive index is as follows (hereinafter the same).

(Measurement of single film refractive index of each layer)
In order to measure the refractive index, a sample in which the high refractive index layer coating solution 1 was applied as a single layer on a substrate was prepared, and this sample was cut into 10 cm × 10 cm, and then the refractive index was determined according to the following method. . Using Hitachi spectrophotometer U-4100 (solid sample measurement system), the surface opposite to the measurement surface (back surface) of each sample is roughened and then light absorption is performed with a black spray. Then, reflection of light on the back surface was prevented, the reflectance in the visible light region (400 nm to 700 nm) was measured under the condition of regular reflection at 5 degrees, and the refractive index was obtained from the result.

[Production Examples 2 to 7: Production of coating solutions 2 to 7 having a high refractive index layer]
In Production Example 1, the amount of the aqueous solution of the added nitrogen-containing heteroaromatic compound (oxidant) was changed, and the same procedure as in Production Example 1 was carried out except that the amount of oxidant added was changed as shown in Table 1 below. Thus, high refractive index layer coating solutions 2 to 7 were prepared. The refractive index of the high refractive index layer obtained by applying and drying the coating solutions 2 to 7 for the high refractive index layer was 1.82.

[Production Examples 8 to 18: Production of high refractive index layer coating solutions 8 to 18]
In Production Example 1, the type of the aqueous solution of the added nitrogen-containing heteroaromatic compound (oxidant) was changed. In each Production Example, an aqueous solution of 2-methylbenzimidazole (compound represented by the above chemical formula 2), 5- An aqueous solution of methylbenzimidazole (compound represented by Chemical Formula 3), an aqueous solution of 1-methylimidazole (Compound represented by Chemical Formula 4), an aqueous solution of 2-aminoimidazole (Compound represented by Chemical Formula 5), An aqueous solution of 2-mercapto-1-methylimidazole (compound represented by the above chemical formula 6), an aqueous solution of 2-ethyl-4-methylimidazole (compound represented by the above chemical formula 7), 4-imidazolecarboxylic acid (the above chemical formula) 8), an aqueous solution of 2-methylpyridine (a compound represented by the above chemical formula 9), 2-aminopyri An aqueous solution of 2,6-dimethylpyrazine (a compound represented by the above chemical formula 11), and an aqueous solution of 2-aminopyrazine (a compound represented by the above chemical formula 12). High refractive index layer coating liquids 8 to 18 were produced in the same manner as in Production Example 1 except that each was changed. The refractive indexes of the high refractive index layers obtained by applying and drying the coating solutions 8 to 18 for the high refractive index layer were 1.82.

[Production Example 19: Preparation of coating solution 19 for high refractive index layer]
A high refractive index layer coating solution 19 was produced in the same manner as in Production Example 1 except that the aqueous solution of the nitrogen-containing heteroaromatic compound (oxidant) in Production Example 1 was not added. The refractive index of the high refractive index layer obtained by applying and drying the coating solution 19 for high refractive index layer was 1.82.

[Production Example 20: Production of high refractive index layer coating solution 20]
A high refractive index layer coating solution except that 25 parts by mass of an 8% by mass cobalt chloride (CoCl ₃ ) aqueous solution and 100 parts by mass of a 2% by mass acetylacetone aqueous solution were added in place of the oxidizing agent aqueous solution in Production Example 1. 20 was produced. The refractive index of the high refractive index layer obtained by applying the coating liquid 20 for high refractive index layer and drying was 1.82. In the above, by adding an aqueous cobalt chloride solution and an aqueous acetylacetone solution, acetylacetone undergoes a chelate reaction with respect to the total amount of cobalt chloride, so that a chelate compound in which acetylacetone is coordinated to cobalt is generated. Therefore, the mass ratio of the cobalt complex (acetylacetone cobalt) to the titanium oxide particles in the high refractive index layer coating solution 20 is 5% by mass.

[Production Example 21: Production of coating solution 1 for low refractive index layer]
10 mass% acidic colloidal silica aqueous solution (Snowtex OXS, average primary particle size: 4 to 6 nm, manufactured by Nissan Chemical Industries, Ltd.) 430 mass parts, 3 mass% boric acid aqueous solution 85 mass parts, pure water 182 mass parts , 300 parts by weight of a 4% by weight aqueous solution of polyvinyl alcohol (PVA-220, degree of polymerization: 2000, degree of saponification: 87 mol%, manufactured by Kuraray Co., Ltd.) and a solution of 5% by weight of a surfactant (Amphitol HD, Kao Corporation) 3 parts by mass) were added and mixed at 45 ° C. in this order to prepare a low refractive index layer coating solution 1. The refractive index of the low refractive index layer obtained by applying and drying the coating solution 1 for low refractive index layer was 1.48.

<Example 1>
Using a slide bead (slide hopper) coating apparatus capable of coating 15 layers, the high refractive index layer coating solution 1 produced in Production Example 1 and the low refractive index layer coating solution 1 produced in Production Example 21 The film was laminated on a 50 μm-thick polyethylene terephthalate film (A4300 manufactured by Toyobo Co., Ltd., double-sided easy-adhesive layer, length 200 m × width 210 mm) while keeping the temperature at 0 ° C. At this time, a total of 15 layers were simultaneously applied so that the lowermost layer and the uppermost layer (the outermost layer) were low refractive index layers, and the high refractive index layers and the low refractive index layers were otherwise alternated. . At this time, the film thickness at the time of drying is adjusted so that the lowermost layer is 1510 nm, the outermost layer is 10 nm, the lower refractive index layers other than the lowermost layer and the uppermost layer are 150 nm, and the high refractive index layers are 150 nm. did.

  Immediately after the application, 5 ° C. cold air was blown to increase the viscosity. After thickening, hot air of 80 ° C. was blown and dried to prepare an optical reflection film 1 having a total of 15 layers.

<Examples 2-18 and Comparative Examples 1-2>
In Example 1, except that the coating liquid used for forming the high refractive index layer was changed to the high refractive index layer coating liquids 2 to 20 shown in Table 1, respectively, in the same manner as in Example 1, the optical reflective film 2-18 and the comparative optical reflection films 1-2 were produced, respectively.

[Evaluation]
The optical reflection films 1 to 18 and the comparative optical reflection films 1 to 2 obtained in the above examples and comparative examples were evaluated for the color tone (a ^* ), color difference (ΔE), haze and appearance of the reflective layer according to the following methods. (Durability evaluation) was performed. The following evaluations were performed independently.

(Color evaluation)
By measuring the transmittance in the visible light region (360 to 740 nm) using a spectrophotometer U-4100 (manufactured by Shimadzu Corporation) for the optical reflective films produced in Examples and Comparative Examples, The value of a ^* in the L ^* a ^* b ^* color system of the reflective film was measured. A smaller a ^* value means that the redness of the film is suppressed.

(Color difference evaluation)
The following evaluation was performed about the optical reflective film obtained by the said Example and comparative example, respectively.

Each of the optical reflection film samples produced above was attached to blue glass having a thickness of 3 mm via an adhesive layer. Using a sunshine weather meter using a carbon arc lamp, the sample was exposed for 2000 hours at an illuminance of 250 W / cm ² , a temperature of 40 ° C., and a humidity of 50% RH, and the color difference ( ΔE) was calculated. In addition, the transmitted light of the sample before and after exposure was evaluated by the transmittance in a 200 to 2000 nm region of a spectrophotometer U-4000 type (using an integrating sphere, manufactured by Hitachi, Ltd.). A smaller value of ΔE means that the degree of coloring due to light exposure by the carbon arc lamp is smaller.

(Measure haze)
About the optical reflection film obtained by the said Example and each comparative example, it exposed on the conditions similar to the said (color difference evaluation), and measured the haze with the haze meter (Nippon Denshoku Industries Co., Ltd. make, NDH2000). The light source of the haze meter was a 5V9W halogen sphere, and a silicon photocell (with a relative visibility filter) was used as the light receiving part. The haze was measured at 23 ° C. and 55% RH.

(Appearance (durability) evaluation)
About the optical reflection film obtained by the said Example and each comparative example, it exposed on the conditions similar to the said (color-difference evaluation), the bending test was performed as follows, and the external appearance evaluation (durability evaluation) was performed.

  The bending test was performed by an IPC bending test according to the IPC standard TM-650. This is sandwiched between the fixed plate and the movable plate so that the surface of the laminated film is convex, and the movable plate is repeatedly moved. The R of the film was set to 10 mm, the stroke was set to 60 mm, and the number of repetitions was 30.

  The evaluation criteria are as follows.

◎: There is no crack or peeling on the surface, and no streak is visible even with an optical microscope. The peeling is visible.

  The results of the various evaluations are shown in Table 1 below. In Comparative Example 2, since the metal chelate compound was added instead of the oxidant in the present invention, the item regarding “oxidant” was described with respect to the metal chelate compound.

  From Table 1 above, when a specific nitrogen-containing heteroaromatic compound (oxidant) coexists with titanium oxide particles, an optical reflective film excellent in color tone (redness reduction), color difference, haze, and durability is obtained. It was shown that

  When Examples 1-18 were compared, it became clear that the oxidizing agent which has a benzimidazole frame | skeleton and an imidazole frame | skeleton exhibits the outstanding discoloration inhibitory effect compared with others. In particular, it has also been found that an oxidizing agent having a benzimidazole skeleton has a high discoloration suppressing effect.

  Further, comparing Examples 1, 8 and 9, it was shown that the optical reflective film of Example 1 (ie, the embodiment in which the oxidizing agent is a compound having an amino group) has a high effect of suppressing discoloration. . Such a tendency was the same in the comparison of Examples 10 to 14, the comparison of Examples 15 and 16, and the comparison of Examples 17 and 18. From the above, it was shown that when the oxidizing agent is a compound having an amino group, the discoloration suppressing effect is particularly high.

  On the other hand, the optical reflective film added with the cobalt chelate complex as in Comparative Example 2 has an initial color tone (redness) that is not good, and has a color change (ΔE) as compared with the optical reflective film according to the present invention. The result was that it was large and was not good in terms of durability.

  Moreover, when Examples 1-18 were compared with the comparative example 2, in the optical reflection film which concerns on this invention, the initial redness was reduced effectively.

Claims (7)

An optical reflection film comprising at least one unit obtained by laminating a low refractive index layer and a high refractive index layer on a substrate,
The high refractive index layer includes a water-soluble resin, titanium oxide particles, and a nitrogen-containing heteroaromatic compound,
The optical reflective film in which the nitrogen-containing heteroaromatic compound is contained in the high refractive index layer in an amount of more than 0% by mass and less than 20% by mass with respect to the titanium oxide particles.   The optical reflective film according to claim 1, wherein the nitrogen-containing heteroaromatic compound includes an imidazole skeleton.   The optical reflective film according to claim 1, wherein the nitrogen-containing heteroaromatic compound includes a benzimidazole skeleton.   The optical reflective film according to any one of claims 1 to 3, wherein the nitrogen-containing heteroaromatic compound has an amino group, a monoalkylamino group, or a dialkylamino group.   5. The optical reflective film according to claim 1, wherein the nitrogen-containing heteroaromatic compound is contained in the high refractive index layer in an amount of 1 to 15 mass% with respect to the titanium oxide particles.   The optical reflective film according to any one of claims 1 to 5, wherein the titanium oxide particles include rutile-type titanium oxide.   The optical reflective film according to any one of claims 1 to 6, wherein the titanium oxide particles contain titanium oxide modified with silica.