JP2017021214A - Manufacturing method for optical films - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique for providing high-quality optical films with minimized spot defects of optical functional layers.SOLUTION: A method is disclosed for manufacturing an optical film comprising at least two different optical functional layers formed on a base material. The method includes: a control step for providing control to keep a difference in dynamic surface tension, at a surface lifetime of 500 ms, between optical functional layer-forming liquids for forming adjacent optical functional layers at a level no greater than 10 mN/m; and a step for forming two or more optical functional layers by simultaneously multilayer-coating the base material with the surface tension-controlled optical functional layer-forming liquids. The optical functional layer-forming coating liquids for forming the adjacent optical functional layers each contain a polyvinyl alcohol having a different degree of saponification.SELECTED DRAWING: None

Description

  The present invention relates to a method for producing an optical film.

  An optical film is a film that can transmit or reflect and absorb light, and can exhibit optical functions such as refraction, birefringence, antireflection, wide viewing angle, light diffusion, and brightness enhancement.

  Since an optical film has such an optical function, an infrared shielding film, an antireflection film, an alignment film, a polarizing film, a polarizing plate protective film, a retardation film, a viewing angle widening film, a brightness enhancement film, and an electromagnetic wave shielding film For example, they are used in various applications such as flat panel displays (FPD) such as liquid crystal displays (LCD) and plasma displays (PDP), and window glass of buildings and vehicles.

  In manufacturing such an optical film, it is advantageous to use a liquid phase film forming method from the viewpoint of low manufacturing cost, large area, and wide selection range of base materials.

  Among the liquid phase film forming methods, two or more kinds of laminated films are formed on a substrate by coating. Sequential coating by coating and drying one layer at a time and simultaneous multilayer coating by coating multiple layers at the same time There is. Sequential coating includes spin coating, bar coating, blade coating, gravure coating, etc., but productivity is low because the number of coating and drying increases. On the other hand, as simultaneous multilayer coating, there is a method using curtain coating, slide bead coating, or the like, which has an advantage of high productivity because a plurality of layers can be formed simultaneously.

  As a technique for manufacturing an optical film such as an infrared suppression film by simultaneous multilayer coating, for example, a technique such as Patent Document 1 is known.

  On the other hand, when the liquid phase film forming method is used, polyvinyl alcohol is preferably used as the binder, but particularly when two or more kinds of coating liquids are used for simultaneous multilayer coating, the saponification degree of the polyvinyl alcohol used may be different. It is said that. This is because the mixing between the optical functional layers providing the optical function can be suppressed in each of the coating and drying steps due to the different saponification degrees.

  In recent years, the optical functional layer is required not only to suppress mixing but also to have a higher quality, and various studies have been conducted in order to suppress various defects during film formation.

JP 2013-190635 A

  By the way, various defects such as streak failure and unevenness exist, and among them, there is a defect called point-like failure. If there is this defect, for example, when it is used for a window glass or the like, the appearance is deteriorated and the visibility is also adversely affected.

  However, among various defects, it is said that it is particularly difficult to remove point-like faults.

  Then, this invention makes it a subject to provide the technique which can manufacture the high quality optical film which suppressed the point-like failure of the optical function layer.

  The present inventors have intensively studied to solve the above problems. As a result, there is provided a method for producing an optical film in which at least two types of optical functional layers are formed on a substrate, and the application of the coating liquid for an optical functional layer, which becomes an adjacent optical functional layer, with a surface life of 500 ms. A control step of controlling the difference in surface tension to 10 mN / m or less; and forming at least two optical functional layers by simultaneously applying the controlled coating solution for the optical functional layer on the substrate. And the above-mentioned problem can be solved by a method for producing an optical film, wherein the coating solution for an optical functional layer that becomes the adjacent optical functional layer contains polyvinyl alcohols having different saponification degrees. Heading The present invention has been completed.

  ADVANTAGE OF THE INVENTION According to this invention, the high quality optical film which suppressed the point-like failure of the optical function layer can be provided.

  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% RH.

  The present invention relates to a method for producing an optical film in which at least two types of optical functional layers are formed on a substrate, and an optical functional layer coating liquid that becomes an adjacent optical functional layer can be operated with a surface life of 500 ms. A control step of controlling the difference in the surface tension to 10 mN / m or less; and applying at least two optical functional layers by simultaneously applying the controlled coating solution for the optical functional layer on the substrate. And a coating solution for an optical functional layer that becomes an adjacent optical functional layer contains polyvinyl alcohol having different saponification degrees.

  Conventionally, in order to prevent various defects, we tried to provide high-quality optical films by filtering and deaeration in order to remove foreign substances and bubbles present in the coating liquid for optical functional layers. There was also a technology. By doing so, coating failure due to foreign matter and bubbles has been reduced. However, there was a problem that the coating failure could not be completely removed.

  In the process of studying to solve such problems, the present inventors paid attention to the interface of the multilayer coating. That is, when a cross section of the coating film formed by simultaneous multilayer coating is analyzed, it has been found that there is a point-like failure that is caused by the application of the coating liquid for the optical functional layer at this interface. As a result of various studies to eliminate this point-like failure, it was found that this phenomenon is often expressed when the difference in the dynamic surface tension of the coating liquid for the optical functional layer that becomes the adjacent optical functional layer becomes large. It was done.

  In response to the discovery, when forming at least two types of optical functional layers by simultaneously applying at least two types of coating solutions for optical functional layers on a substrate, the coating for optical functional layers becomes an adjacent optical functional layer. An attempt was made in advance to control the difference in dynamic surface tension below a specific value for the liquid. Surprisingly, it succeeded in suppressing point-like failures that were difficult to remove. The present invention has been completed in this manner.

  According to the production method of the present invention, it is possible to suppress a point-like failure of the optical functional layer and to provide a high-quality optical film.

  First, an embodiment of components of the optical film will be described in detail.

  The optical film has different functions depending on the composition and configuration of the optical functional layer. Therefore, various films such as an infrared shielding film, an antireflection film, an orientation film, a polarizing film, a polarizing plate protective film, a retardation film, a viewing angle widening film, and a brightness enhancement film can be obtained by appropriately taking into account known matters. And an electromagnetic wave shielding film. Below, an infrared shielding film is demonstrated as a preferable form of an optical film.

  In general, in an infrared shielding film, it is preferable to design a large difference in refractive index between adjacent refractive index layers from the viewpoint that the infrared reflectance can be increased with a small number of layers. In the present embodiment, at least one of the refractive index differences between adjacent refractive index layers is preferably 0.1 or more, and more preferably 0.3 or more. Further, it is preferable that all refractive index differences between the refractive index layers are within the preferable range. However, even in this case, the outermost layer and the lowermost layer among the refractive index layers constituting the reflective layer may have a configuration outside the above preferred range.

  The reflectance in the specific wavelength region is determined by the difference in refractive index between two adjacent layers and the number of stacked layers, and the larger the difference in refractive index, the same reflectance can be obtained with a smaller number of layers. The refractive index difference and the required number of layers can be calculated using commercially available optical design software.

  As an optical characteristic of the infrared shielding film of this embodiment, it is preferable to have a region having a reflectance of more than 50% in a region having a wavelength of 780 nm to 2500 nm, and preferably having a region exceeding 60%.

  The infrared shielding film has a configuration in which a refractive index layer formed by applying a refractive index layer coating liquid is laminated on a substrate. The infrared shielding film exhibits an infrared shielding effect by shielding at least a part of the infrared light when irradiated with infrared light from the substrate side or the refractive index layer side. In the present invention, the “refractive index layer coating solution” corresponds to the “optical functional layer coating solution”, and the “refractive index layer” corresponds to the “optical functional layer”.

  In one embodiment of the infrared shielding film, the refractive index layer is formed by alternately stacking a high refractive index layer and a low refractive index layer. In the present invention, two types of coating solutions for the optical functional layer are used and two layers are considered as “one unit”. Therefore, in the present embodiment, “a high refractive index layer and a low refractive index layer” corresponds to “one unit”. That is, according to a preferred embodiment of the present invention, after the control, two types of coating liquids for the optical function layer are used to form one unit, and a plurality of the units are stacked. The optical functional layer coating solution is simultaneously coated on the substrate. Such a configuration improves optical characteristics (for example, infrared shielding efficiency).

  Whether the refractive index layer is classified as a high refractive index layer or a low refractive index layer is determined by comparing the refractive index with an adjacent refractive index layer. Specifically, when a refractive index layer is used as a reference layer, if the refractive index layer adjacent to the reference layer has a lower refractive index than the reference layer, the reference layer is a high refractive index layer (the adjacent layer is a low refractive index layer). It is judged to be a rate layer. On the other hand, if the refractive index of the adjacent layer is higher than that of the reference layer, it is determined that the reference layer is a low refractive index layer (the adjacent layer is a high refractive index layer).

  As described above, whether it is a high refractive index layer or a low refractive index layer is a relative one determined by the relationship with the adjacent refractive index layer, but the refractive index of the high refractive index layer is 1.60. It is preferably 2.50, more preferably 1.70 to 2.50, and even more preferably 1.80 to 2.20. On the other hand, the refractive index of the low refractive index layer is preferably 1.10 or more and less than 1.60, more preferably 1.30 to 1.55, and preferably 1.30 to 1.50. Further preferred. In addition, the value of the refractive index of each refractive index layer is based on the method described in the examples.

  In one embodiment of the infrared shielding film, the range of the total number of refractive index layers is preferably 6 to 40 layers, more preferably 10 to 30 layers, and further preferably 13 to 25 layers. . When many layers are stacked in this way, the number of interfaces increases accordingly, so that the probability of occurrence of point failures tends to increase as a matter of course. On the other hand, in the present invention, by making the process of controlling the difference in dynamic surface tension of the coating liquid for optical function layer to be an adjacent optical function layer at a surface life of 500 ms to 10 mN / m or less. Even if the number of layers increases, it is possible to provide a high-quality optical film that suppresses the point-like failure of the optical functional layer.

  In one embodiment of the infrared shielding film, the thickness (thickness after drying) per one layer (excluding the lowermost layer and the outermost layer) of the refractive index layer is preferably 20 to 1000 nm, and preferably 50 to 500 nm. It is more preferable that it is 50-350 nm. 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. Further, the thickness (thickness after drying) of the refractive index layer of the outermost layer is preferably 1 to 200 nm, more preferably 10 to 180 nm, and more preferably 30 to 160 nm.

  Then, below, an infrared shielding film is mentioned as an example and the manufacturing method of the optical film of this invention is demonstrated.

  In the production of an infrared shielding film, usually, a step (preparation step) of preparing at least two types of coating solutions for a refractive index layer, that is, a coating solution for a high refractive index layer and a coating solution for a low refractive index layer; A step (coating step) of simultaneously applying the obtained coating liquid for at least two kinds of refractive index layers on a substrate (a coating step); a step of drying a coating film applied simultaneously on the substrate (a drying step); ;including. As described above, the step of forming at least two optical functional layers by simultaneously applying the optical functional layer coating liquid (the coating liquid for the high refractive index layer and the coating liquid for the low refractive index layer) on the substrate. By including, an optical film (infrared shielding film) is manufactured.

  The present invention is characterized in that a control step is included before the coating step. By including such a control step, it is possible to obtain a high-quality optical film that suppresses the point-like failure of the optical functional layer.

  Hereinafter, preferable embodiment of each process in the manufacturing method of an infrared shielding film is described.

<Preparation process>
In the production of an infrared shielding film, at least two types of coating solutions for a refractive index layer are usually prepared as a coating solution for an optical functional layer: a coating solution for a high refractive index layer and a coating solution for a low refractive index layer.

  The method for preparing the coating solution for the high refractive index layer and the coating solution for the low refractive index layer is not particularly limited, and polyvinyl alcohol having a different saponification degree and, if necessary, a metal oxide particle, a crosslinking agent, etc. And stirring and mixing. 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 embodiment, the high refractive index layer coating liquid and the low refractive index layer coating liquid are laminated so as to be adjacent refractive index layers. In this embodiment, the refractive index layer is preferably formed by alternately laminating a plurality of high refractive index layers and low refractive index layers.

  In the present embodiment, it is premised that the coating liquid for the high refractive index layer and the coating liquid for the low refractive index layer contain polyvinyl alcohols having different saponification degrees. As described above, depending on the degree of saponification, mixing between the refractive index layers (that is, between the high refractive index layer and the low refractive index layer) is performed on the infrared shielding film in each step of coating and drying. Can be suppressed.

  However, the present inventors have found that there is a problem that a point-like failure occurs although there is an advantage that such mixing is suppressed.

  As a result of intensive studies to solve this problem, the difference in dynamic surface tension between the coating liquid for the high refractive index layer and the coating liquid for the low refractive index layer, which become adjacent refractive index layers, at a surface life of 500 ms. Has been found to provide a high-quality infrared shielding film in which a point-like failure of the refractive index layer is suppressed by controlling to 10 mN / m or less.

(Polyvinyl alcohol)
Polyvinyl alcohol may be unmodified or modified.

  The unmodified polyvinyl alcohol has an average degree of polymerization of about 200 to 2400, preferably an average degree of polymerization of about 900 to 2400, and more preferably an average degree of polymerization of about 1300 to 4000.

  Modified polyvinyl alcohol is one obtained by subjecting unmodified polyvinyl alcohol to one or more of arbitrary modification treatments. Examples thereof include amine-modified polyvinyl alcohol, ethylene-modified polyvinyl alcohol, carboxylic acid-modified polyvinyl alcohol, diacetone-modified polyvinyl alcohol, thiol-modified polyvinyl alcohol, and acetal-modified polyvinyl alcohol. As these modified polyvinyl alcohols, commercially available products may be used, or those produced by methods known in the art may be used. Further, modified polyvinyl alcohols such as polyvinyl alcohol having a cation-modified terminal, anion-modified polyvinyl alcohol having an anionic group, and nonionic modified polyvinyl alcohol may also 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 and other Poval (registered trademark, manufactured by Kuraray Co., Ltd.), RS-4104, RS-1117, RS-2117, etc. Nichigo G polymer (registered trademark, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and the like.

  The content of polyvinyl alcohol is preferably 3 to 70% by mass, more preferably 5 to 60% by mass, still more preferably 10 to 50% by mass, and particularly preferably 15 to 45% with respect to each coating solution for the refractive index layer. % By mass.

  In the present embodiment, the saponification degree of polyvinyl alcohol in the coating solution for the high refractive index layer is preferably 85 mol% or more, more preferably 90 mol% or more, and 95 mol% or more from the viewpoint of solubility in water. Further preferred. From the viewpoint of haze, the saponification degree of polyvinyl alcohol in the coating solution for the low refractive index layer is preferably 80 to 89 mol%, more preferably 83 to 89 mol%, and 85 to 89 mol%. More preferably.

  In the present embodiment, the difference in the degree of saponification of the polyvinyl alcohol used in the coating solution for the high refractive index layer and the coating solution for the low refractive index layer is preferably 4 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 4 mol% or more, and more preferably 8 mol% or more. The upper limit of the difference between the saponification degree of the coating solution for the high refractive index layer and the saponification degree of the coating solution for the low refractive index layer is, in consideration of the effect of suppressing / preventing interlayer mixing between the high refractive index layer and the low refractive index layer, Since it is more preferable as it is higher, it is not particularly limited, but it is preferably 20 mol% or less, more preferably 15 mol% or less.

  When each refractive index layer contains a plurality of polyvinyl alcohols (different saponification degrees), the polyvinyl alcohol having the highest content in the refractive index layer is used as a reference. Here, when the phrase “polyvinyl alcohol having the highest content in the refractive index layer” is used, the degree of saponification is calculated assuming that the polyvinyl alcohol having a difference in saponification degree 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 3 The two polyvinyl alcohols are the same polyvinyl alcohol, and the saponification degree of the polyvinyl alcohol is (90 × 0.1 + 91 × 0.4 + 93 × 0.5) /1=91.9 mol%. The above-mentioned “polyvinyl alcohol having a saponification degree difference of 3 mol% or less” means that it is sufficient to be within 3 mol% when attention is paid to any polyvinyl alcohol, for example, 90, 91, 92, 94 mol% of vinyl alcohol is included. In this case, when paying attention to 91 mol% of vinyl alcohol, all the polyvinyl alcohols are within 3 mol%, so that all of them have the same degree of saponification.

(Metal oxide particles)
In the present embodiment, at least one of the high refractive index layer coating solution and the low refractive index layer coating solution may include metal oxide particles.

As the metal oxide particles is not particularly limited, titanium oxide _(TiO 2), zinc oxide (ZnO), zirconium oxide _(ZrO 2), niobium oxide _{(Nb 2 O} 5), aluminum oxide _{(Al 2 O} 3), Examples thereof include silicon oxide (SiO ₂ ), calcium fluoride (CaF ₂ ), magnesium fluoride (MgF ₂ ), indium tin oxide (ITO), and antimony tin oxide (ATO).

Of these, titanium oxide (TiO ₂ ) is preferably used for the coating solution for the high refractive index layer.

Some titanium oxides (TiO ₂ ) have a rutile type (tetragonal type), anatase type, brookite type, etc., but rutile type titanium oxide particles include anatase type and brookite type titanium oxide particles. Compared with the low photocatalytic activity, there is an advantage that the weather resistance of the high refractive index layer and the adjacent low refractive index layer is high, and the refractive index is also high.

  According to a preferred embodiment of the present invention, the rutile-type titanium oxide is in a form coated with a silicon-containing hydrated oxide. Here, the term “coating” means a state in which a silicon-containing hydrated oxide is attached to at least a part of the surface of the rutile-type titanium oxide. That is, the surface of the rutile type titanium oxide may be completely covered with a silicon-containing hydrated oxide, or a part of the surface of the rutile type titanium oxide may be covered with a silicon-containing hydrated oxide. Good. From the viewpoint that the refractive index of the coated rutile type titanium oxide is controlled by the coating amount of the silicon-containing hydrated oxide, a part of the surface of the rutile type titanium oxide is coated with the silicon-containing hydrated oxide. Is preferred.

  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.

  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 rutile-type 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, when the coating amount is 3% by mass or more, the particles can be stably formed.

  As a method of coating rutile-type titanium oxide with a silicon-containing hydrated oxide, a method which is appropriately referred to or combined with the present embodiment may be applied, or a conventional method may be used. be able to. For example, the matters described in JP-A-10-158015, JP-A-2000-204301, JP-A-2007-246351, and the like can also be referred to.

  The size of rutile-type titanium oxide (rutile-type titanium oxide coated with silicon hydrated oxide) contained in the coating solution for the high refractive index layer is not particularly limited, but its volume average particle diameter is , 100 nm or less, preferably 1 to 100 nm, more preferably 3 to 50 nm. By setting it as the said range, it is preferable from a viewpoint of maintaining high transparency.

  In addition, the volume average particle diameter referred to in the present specification is calculated as follows. That is, by observing the particles themselves using a laser diffraction scattering method, dynamic light scattering method, or an electron microscope, or by observing a particle image appearing on the cross section or surface of the refractive index layer with an electron microscope, A group of particles in which the particle size of 000 arbitrary particles is measured, and there are n1, n2... Ni... Nk particles each having a particle size of d1, d2. , The average particle diameter weighted by the volume represented by the volume average particle diameter mv = {Σ (vi · di)} / {Σ (vi)} where v is the volume per particle. To do.

  The average particle diameter in terms of specific surface area of rutile titanium oxide used in the coating solution for the high refractive index layer is preferably 10 nm or less, more preferably 2 to 7 nm, and more preferably 3 to 6 nm. Further preferred. By setting it as the said range, it is preferable from a viewpoint of maintaining transparency. In addition, the specific surface area conversion average particle diameter of a rutile type titanium oxide shall point out the value measured by the following measuring methods. First, the target particles are measured using a constant volume method gas adsorption amount measuring apparatus (for example, BELSORP-mini II (manufactured by Nippon Bell Co., Ltd.)) to obtain a BET specific surface area. From the obtained BET specific surface area, the average particle diameter in terms of specific surface area can be determined by calculating the primary particle diameter using the particles as true spheres.

  Further, the rutile titanium oxide is 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 rutile-type titanium oxide in the coating solution for the high refractive index layer is not particularly limited, but is preferably 30 to 60% by mass with respect to the coating solution for the high refractive index layer, and is 35 to 55% by mass. More preferably, it is more preferably 40 to 50% by mass. By setting it as the said range, it can be set as a thing with a favorable heat ray reflective characteristic.

Silica (SiO ₂ ) is preferably used for the coating solution for the low refractive index layer.

  Specific examples include synthetic amorphous silica, colloidal silica, zinc oxide, alumina, colloidal alumina, and the like.

  As a metal oxide particle contained in the coating liquid for low refractive index layers, it may be used individually by 1 type and may use 2 or more types together.

  The average particle size (particle size in the dispersion state before coating) of the primary particles of metal oxide particles (preferably silicon dioxide) contained in the coating solution for the low refractive index layer is more preferably 1 to 50 nm. 1 to 40 nm is more preferable, 3 to 20 nm is particularly preferable, and 4 to 10 nm is most preferable. Further, the average particle diameter of the secondary particles is preferably 35 nm or less from the viewpoint of transparency.

  In addition, a primary average particle diameter can be measured from the electron micrograph by a transmission electron microscope (TEM) etc. 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 size of the particles is observed by the electron microscope, the particle itself or the particles appearing on the cross section or surface of the refractive index layer, and the particle size 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.

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

  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 metal oxide particles in the coating solution for the low refractive index layer is preferably 20 to 60% by mass and more preferably 25 to 55% by mass with respect to the coating solution for the low refractive index layer. More preferably, it is 30 to 50% by mass.

(Crosslinking agent)
In the present embodiment, at least one of the coating solution for the high refractive index layer and the coating solution for the low refractive index layer may contain a crosslinking agent.

  Cross-linking agents that can be used include boric acid and salts thereof (oxygen acid and salts thereof having a boron atom as a central atom), specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, and pentaboric acid. And octaboric acid or their salts are preferably used. Boric acid and its salt may be used alone or in admixture of two or more, and it is particularly preferable to use a mixed aqueous solution of boric acid and borax.

  The concentration of at least one crosslinking agent in the coating solution for the high refractive index layer and the coating solution for the low refractive index layer is preferably 0.001 to 20% by mass, more preferably 0.01 to 10% by mass. preferable. When the crosslinking agent is in the above range, there is an effect of reducing color unevenness during coating.

(solvent)
In the present embodiment, at least one of the coating solution for the high refractive index layer and the coating solution for the low refractive index layer may contain a solvent. Such a solvent is not particularly limited, and examples thereof include water, an organic solvent, or a mixed solvent thereof.

  Examples of the organic solvent include alcohols such as methanol, ethanol, 2-propanol, and 1-butanol; esters such as ethyl acetate, butyl acetate, propylene glycol monomethyl ether acetate, and propylene glycol monoethyl ether acetate; diethyl ether; Examples thereof include ethers such as propylene glycol monomethyl ether and ethylene glycol monoethyl ether; amides such as dimethylformamide and N-methylpyrrolidone; ketones such as acetone, methyl ethyl ketone, acetylacetone and cyclohexanone. These organic solvents may be used alone or in admixture of two or more. From the viewpoint of environment and simplicity of operation, the solvent of the coating solution is preferably water or a mixed solvent of water and methanol, ethanol, or ethyl acetate, and more preferably water.

(Other additives)
Other additives applicable to the coating solution for the high refractive index layer and the coating solution for the low refractive index layer are listed below. For example, various surfactants such as ultraviolet absorbers, anions, cations, or nonions described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, sulfuric acid, PH adjusters such as phosphoric acid, acetic acid, citric acid, sodium hydroxide, potassium hydroxide and potassium carbonate, antifoaming agents, lubricants such as diethylene glycol, preservatives, antifungal agents, antistatic agents, matting agents, antioxidants And various known additives such as additives, flame retardants, infrared absorbers, dyes and pigments.

<Control process>
In the present invention, a control step is included before the coating step. By performing the control step, the difference in the dynamic surface tension of the coating liquid for the optical functional layer that becomes the adjacent optical functional layer with a surface life of 500 ms can be controlled to 10 mN / m or less. It is possible to provide a high-quality optical film that suppresses point-like failures. The difference in dynamic surface tension at a surface lifetime of 500 ms may be 10 mN / m or less, but may be 9 mN / m or less, 7 mN / m or less, 6 mN / m or less, or 5 mN / m. Or 3 mN / m or less. However, the difference in dynamic surface tension at a surface lifetime of 500 ms is practically about 0.01 ms or more. In addition, the value of dynamic surface tension shall be the value by the method of an Example.

  As will be described below, in a preferred embodiment of the present invention, it is preferable to use a slide bead coating method in the coating step. The coating solution for the high refractive index layer and the coating solution for the low refractive index layer flow on the slide surface and are applied to the substrate in the slide bead coating method. Since the coating solution for the high refractive index layer and the coating solution for the low refractive index layer flow on the slide surface, the interface (surface) state between the coating solution for the high refractive index layer and the coating solution for the low refractive index layer Is updated from time to time before being applied to the substrate.

  In a preferred embodiment of the present invention, it is assumed that the surface renewal speed in the slide bead coating method is about 50 to 1500 ms. With such a surface renewal speed, by controlling the difference in dynamic surface tension at a surface life of 500 ms to 10 mN / m or less, a point-like shape formed by the application liquid for the optical functional layer repelling at the interface. Failures can be suppressed, and the desired effects of the present invention can be achieved. The desired surface update speed can be controlled by appropriately adjusting the viscosity of the coating liquid, the angle of the slide surface, and the like. The surface update rate can be calculated by simulation. The simulation will be described in the example section.

  In the present invention, the control process may be performed before the coating process, but in a preferred embodiment of the present invention, the control process is performed in the preparation process. In addition, as a control step, any method can be used as long as it can control the difference in dynamic surface tension of the coating liquid for an optical functional layer to be an adjacent optical functional layer at a surface life of 500 ms to 10 mN / m or less. However, some methods will be described below.

(Method using organic solvent)
According to the preferable form of the control process in this embodiment, an organic solvent having 1 to 20 carbon atoms is added to at least one of the coating solution for the high refractive index layer and the coating solution for the low refractive index layer. As a result, the difference in dynamic surface tension with a surface life of 500 ms can be easily controlled to 10 mN / m or less. That is, in a preferred embodiment of the present invention, the control step includes a step of adding an organic solvent having 1 to 20 carbon atoms to at least one kind of the coating solution for an optical function layer. By adding the organic solvent, the organic solvent is present at the interface between the coating solution for the high refractive index layer and the coating solution for the low refractive index layer in the coating step, and the surface tension is lowered.

  In the present embodiment, it is premised that the coating solution for the high refractive index layer and the coating solution for the low refractive index layer contain polyvinyl alcohols having different saponification degrees. That is, the dynamic surface tension of either the coating liquid for the high refractive index layer or the coating liquid for the low refractive index layer is increased or decreased. That is, an organic solvent may be added to either the high refractive index layer coating solution or the low refractive index layer coating solution, but the important thing is that the difference in dynamic surface tension is 10 mN / m or less. The organic solvent may be added to either or both of the high-refractive index layer coating solution and the low-refractive index layer coating solution in an adjusted amount as necessary.

  The timing of adding the organic solvent is not particularly limited, but may be sequentially added and mixed with other components constituting the coating solution for the optical function layer, or the coating solution for the optical function layer may be configured. It may be added and mixed together with the ingredients to be stirred at a time.

  The carbon number of the organic solvent is preferably 1-20, more preferably 2-10. By having such a carbon number, there is a technical effect that it is easily compatible with the coating liquid and that the dynamic surface tension can be easily controlled.

  According to a preferred embodiment of the present invention, the organic solvent is at least one selected from the group consisting of alcohol and ether.

  As alcohol and ether, respectively, Preferably it is C1-C20, More preferably, it is C2-C15, More preferably, it is C3-C10.

  Specific examples of the alcohol include, for example, methanol, ethanol, isopropyl alcohol, n-propyl alcohol, t-butyl alcohol, i-butyl alcohol, n-butyl alcohol, s-butyl alcohol, t-amyl alcohol, and 2-ethylhexanol. And cyclopentanol, cyclohexanemethanol, pentyl alcohol, heptyl alcohol, octyl alcohol, capryl alcohol, nonyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, palmityl alcohol, and stearyl alcohol.

  Specific examples of ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, tetraethylene glycol monoethyl ether, tetraethylene glycol monobutyl ether, propylene glycol mono Cyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, and alkylene glycol monoalkyl ethers such as dipropylene glycol monoethyl ether and propylene glycol monobutyl ether, and ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dibutyl ether, Diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, triethylene glycol dimethyl ether, triethylene glycol diethyl ether, triethylene glycol dibutyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, teto Ethylene glycol dibutyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, can be cited dipropylene glycol diethyl ether, and the like alkylene glycol dialkyl ethers such as polyethylene glycol dimethyl ether. These may be linear or branched, but are preferably linear.

  Of these, ethanol, isopropyl alcohol, n-propyl alcohol, propylene glycol-n-butyl ether and the like are preferable from the viewpoint of compatibility with the coating solution.

  In this embodiment, 0.01 to 10% by mass of the organic solvent is added to at least one of the high refractive index layer coating solution and the low refractive index layer coating solution. Therefore, according to a preferred embodiment of the present invention, the organic solvent is added in an amount of 0.01 to 10% by mass with respect to the coating solution for optical function layer. By doing so, the dynamic surface tension can be controlled without extremely reducing the viscosity of the coating solution. The addition amount may be adjusted so that the difference in dynamic surface tension at a surface life of 500 ms can be controlled to 10 mN / m or less.

(Method using surfactant)
According to a preferred form of the control step in the present embodiment, there is a step of adding a surfactant to at least one of the high refractive index layer coating solution and the low refractive index layer coating solution so as to exceed the critical micelle concentration. As a result, the dynamic surface tension difference at a surface lifetime of 500 ms is controlled to 10 mN / m or less. That is, according to a preferred embodiment of the present invention, the control step includes a step of adding a surfactant so as to exceed a critical micelle concentration in at least one kind of the coating solution for optical function layer.

  Considering the static surface tension, if a sufficient amount of surfactant is added, after the surfactant is oriented at the interface, the surfactant not used for the orientation remains, and these are micelles. Form. In the case of this embodiment, the interface between the coating solution for the high refractive index layer and the coating solution for the low refractive index layer changes from time to time until it is applied to the substrate, but the critical micelle concentration (that is, By adding the surfactant so that the amount exceeds the amount that the surfactant can be aligned at the interface, the probability that the surfactant is present at the interface is improved. By doing so, the dynamic surface tension can be controlled.

  According to this embodiment, a surfactant may be added to at least one of the coating solution for the high refractive index layer and the coating solution for the low refractive index layer so as to exceed the critical micelle concentration, and there is no particular upper limit. In consideration of cost, solubility in a coating solution, and a decrease in viscosity, the concentration is preferably 5 times or less, more preferably 3 times or less the critical micelle concentration. However, these numerical values are merely a guideline, and needless to say, they may vary depending on the type of surfactant (for example, molecular weight). For example, those skilled in the art can also set an amount that does not bleed out from the optical film, depending on the type of surfactant.

  As long as the type of surfactant and the composition of the coating solution for the optical function layer are determined, the critical micelle concentration is determined. Accordingly, the amount of the surfactant added may be determined accordingly.

  In the present embodiment, the surfactant to be added to the coating solution for the optical functional layer may be added so as to exceed the critical micelle concentration, and cannot be generally defined according to the composition. As, it adds 0.1-5 mass% with respect to the coating liquid for optical function layers.

  Further, similarly to the above, in this embodiment, it is premised that the coating liquid for the high refractive index layer and the coating liquid for the low refractive index layer contain polyvinyl alcohols having different saponification degrees. Since the mutual dynamic surface tension can vary depending on the degree of saponification, in this embodiment, the surfactant is added to the coating solution for the high refractive index layer and the low refractive index so that the difference in dynamic surface tension is 10 mN / m or less. This means that it may be added to at least one of the coating solutions for the refractive index layer.

  The timing for adding the surfactant is not particularly limited, but may be added and mixed with stirring together with other components constituting the coating solution for the optical functional layer, or the coating solution for the optical functional layer may be added. You may add and mix with the component to comprise at once, stirring.

  The surfactant is not particularly limited, and examples include zwitterionic surfactants, cationic surfactants, anionic surfactants, nonionic surfactants, fluorosurfactants, and silicon surfactants. .

  Zwitterionic surfactants include alkylbetaines, alkylamine oxides, cocamidopropyl betaines, lauramidopropyl betaines, palm kernel fatty acid amidopropyl betaines, cocoamphoacetic acid N, lauroamphoacetic acid Na, lauramidopropyl hydroxysultain, lauramide Examples include propylamine oxide, myristamidopropylamine oxide, and hydroxyalkyl (C12-14) hydroxyethyl sarcosine.

  Examples of the cationic surfactant include alkylamine salts and quaternary ammonium salts.

  Anionic surfactants include alkyl benzene sulfonate, alkyl naphthalene sulfonate, alkane or olefin sulfonate, alkyl sulfate ester salt, polyoxyethylene alkyl or alkyl aryl ether sulfate ester, alkyl phosphate, alkyl diphenyl ether disulfone. A surfactant selected from the group consisting of acid salts, ether carboxylates, alkylsulfosuccinic acid ester salts, α-sulfo fatty acid esters and fatty acid salts, condensates of higher fatty acids and amino acids, naphthenic acid salts, and the like can be used. . Preferred anionic surfactants are alkylbenzene sulfonates (especially those of linear alkyls), alkanes or olefin sulfonates (especially secondary alkane sulfonates, α-olefin sulfonates), alkyl sulfates Salts, polyoxyethylene alkyl or alkyl aryl ether sulfates (especially polyoxyethylene alkyl ether sulfates), alkyl phosphates (especially monoalkyl type), ether carboxylates, alkyl sulfosuccinates, α-sulfo fatty acid esters and A surfactant selected from the group consisting of fatty acid salts, and alkylsulfosuccinate is particularly preferable.

  Examples of the nonionic surfactant include polyoxyethylene alkyl ether (for example, Emulgen manufactured by Kao Corporation), polyoxyethylene sorbitan fatty acid ester (for example, Leodol TW series manufactured by Kao Corporation), glycerin fatty acid ester, polyoxyethylene fatty acid ester, poly Examples thereof include oxyethylene alkylamine and alkyl alkanolamide. Alternatively, as the polyoxyethylene alkyl ether, polyoxyethylene mono 2-ethylhexyl ether, polyoxyethylene decyl ether (for example, Neugen XL-40, XL-50, XL-60, etc., manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is used. You can also.

  Fluorosurfactants include Surflon S-211, S-221, S-231, S-241, S-242, S-243, S-420 (manufactured by AGC Seimi Chemical Co., Ltd.), Megafac F-114, F-410, F-477, F-553 (made by DIC Corporation), FC-430, FC-4430, FC-4432 (made by 3M company) are mentioned.

  Examples of the silicon surfactant include BYK-345, BYK-347, BYK-348, and BYK-349 (manufactured by BYK Japan).

<Application process>
In the coating process, at least two types of refractive index layer coating liquids (high refractive index layer coating liquid and low refractive index layer coating liquid) obtained in the preparation process and the control process are simultaneously coated on the base material. . In a preferred embodiment of the present invention, it is preferable that the high refractive index layer coating liquid and the low refractive index layer coating liquid be a single unit, and that a plurality of the above units are laminated simultaneously on the substrate.

  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. In particular, the slide beat coating method is preferable.

  According to one embodiment, the wet film thickness of the coating film (single layer) when simultaneously layered on a substrate is preferably less than 5 μm, more preferably 2 μm or more and less than 5 μm, still more preferably 2.5 to 4 μm.

  In the present specification, “wet film thickness” means the thickness of the coating film formed on the substrate before the drying step. Since this coating film is before drying, it usually contains about 60 to 95% of the solvent with respect to the mass of the coating film.

  Such a thin film thickness generally tends to cause the coating liquids to be repelled, and hence facilitates the occurrence of point failures. On the other hand, according to the present invention, the unique process of controlling the difference in dynamic surface tension of the coating liquid for the optical functional layer to be an adjacent optical functional layer at a surface life of 500 ms to 10 mN / m or less. Therefore, even when thinly applied, it is possible to provide a high-quality optical film that suppresses point-like failures.

  When the slide bead coating method is used, the temperature of the coating solution for the high refractive index layer and the coating solution for the low refractive index layer at the time of simultaneous multilayer coating is preferably 25 to 60 ° C, preferably 30 to 45 ° C. A temperature range is more preferred.

  The viscosity of the coating solution for the high refractive index layer and the coating solution for the low refractive index layer at the time of simultaneous multilayer coating is not particularly limited. However, when the slide bead coating method is used, the preferable temperature range of the coating solution is preferably in the range of 5 to 300 mPa · s, more preferably in the range of 20 to 250 mPa · s. If it is the range of such a viscosity, simultaneous multilayer coating can be performed efficiently.

(Base material)
A known resin film can be used as the substrate. Specifically, polyethylene (PE), polypropylene (PP), polystyrene (PS), polyarylate, polymethyl methacrylate, polyamide, polycarbonate (PC), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate. Examples include phthalate (PEN), polysulfone, polyethersulfone, polyetheretherketone, polyimide, aromatic polyamide, and polyetherimide. Of these, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), and the like are preferably used from the viewpoints of cost and availability.

  The thickness of the substrate according to the present invention is preferably 5 to 300 μm, and more preferably 15 to 150 μm.

  Moreover, the base material may be a laminate of two or more, and in this case, the type of the base material may be the same or different.

  The substrate according to the present invention further includes a conductive layer, an antistatic layer, a gas barrier layer, an easy adhesion layer (adhesion layer), an antifouling layer, a deodorant layer, a droplet layer, an easy slip layer, a hard coat layer, and wear resistance. May have a known functional layer such as an adhesive layer, an adhesive layer, and an interlayer film layer. That is, in this specification, the term “... Above” includes not only directly above but also the case of passing through another layer. When a base material has intermediate layers, such as a functional layer, it is preferable that the total film thickness of a base material and an intermediate layer is 5-500 micrometers, and it is more preferable that it is 25-250 micrometers.

<Drying process>
In the drying process, the coating film obtained in the coating process is dried. In this manner, an optical film (infrared shielding film) in which at least two types of optical functional layers (that is, a high refractive index layer and a low refractive index layer) are formed on a substrate can be produced.

  The drying method is not particularly limited, and may be performed by a known method. Examples of the drying method include natural drying, heat drying, a method of applying hot air, a method of applying cold air, and the like. From the viewpoint of rapid drying, it is preferable to perform drying by heat drying. At this time, the heating temperature varies depending on the composition of the formed coating film and the like, but is preferably 15 to 120 ° C, more preferably 20 to 90 ° C.

<Application>
The infrared shielding film obtained above can be applied to a wide range of fields. For example, pasting to facilities exposed to sunlight for a long time, such as outdoor windows of buildings and automobile windows, films for window pasting such as infrared shielding films that give an infrared shielding effect, films for agricultural greenhouses, etc. As, it is mainly used for the purpose of improving the weather resistance.

  In particular, the infrared shielding film can be suitably applied to a member in which the infrared shielding film according to the present invention is bonded to a substrate such as glass or a glass substitute resin directly or via an adhesive.

  That is, according to still another aspect of the present invention, there is also provided an infrared shielding body in which the above infrared shielding film is provided on at least one surface of a substrate.

  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, Examples thereof include phenol resin, diallyl phthalate resin, polyimide resin, urethane resin, polyvinyl acetate resin, polyvinyl alcohol resin, styrene resin, vinyl chloride resin, metal plate, ceramic and the like. The type of the 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 that can be used in the present invention can be produced by a known method such as extrusion molding, calendar molding, injection molding, hollow molding, compression molding and the like. The thickness of the substrate is not particularly limited, but is usually 0.1 mm to 5 cm.

  The adhesive layer or adhesive layer that bonds the infrared shielding film and the substrate is preferably provided with the infrared shielding film on the sunlight (heat ray) incident surface side. In addition, it is preferable to sandwich the infrared shielding film according to the present invention between a window glass and a 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.

  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, a solvent system is preferable in the acrylic pressure-sensitive adhesive because the peel strength can be easily controlled. When a solution polymerization polymer is used as the acrylic solvent-based pressure-sensitive adhesive, known monomers can be used as the monomer.

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

  Insulation performance and solar heat shielding performance of an infrared shielding film or an infrared shielding body are generally JIS R 3209 (multi-layer glass), JIS R 3106 (obtain transmittance, reflectance, emissivity, and solar heat of glass sheets). Rate test method) and JIS R 3107 (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 by calculating the solar transmittance, solar reflectance, solar absorption rate, and vertical emissivity. The corrected emissivity is obtained by multiplying the coefficient shown in JIS R 3107 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 R3209 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 in accordance with JIS R 3107. (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) Solar heat shielding properties are calculated by obtaining the solar heat acquisition rate according to JIS R 3106 and subtracting from 1.

  Moreover, since the infrared shielding film obtained above is thinned, it may be applied to the surface of a display panel. For example, in a plasma display panel, an infrared shielding film can be bonded to a highly transparent PET film and introduced into a display screen. This shields infrared rays radiated from the plasma display panel, which can contribute to protection of the human body, prevention of malfunction between electronic devices, prevention of malfunction of the remote control, and the like.

  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.).

<Preparation of infrared shielding film>
(Production Example 1: Preparation of silica-modified rutile titanium oxide dispersion)
A dispersion of silica-modified rutile titanium oxide 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 TiO ₂ amount to the addition of 0.4 mole% of the amount of citric acid. 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 solution 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 aqueous dispersion) of 20% by mass of silica-modified rutile-type titanium oxide was obtained. At this time, the coating amount of silica was 4 mass% with respect to the rutile type titanium oxide. Further, when the particle size of rutile-type titanium oxide was measured using Zetasizer Nano (manufactured by Malvern), the volume average particle size was 35 nm and the monodispersity was 16%.

  The sol dispersion of silica-modified titanium oxide particles obtained above was spray-dried and dried at 100 ° C. for 3 hours while flowing nitrogen to obtain a powder. The BET specific surface area of this powder was measured using BELSORP-mini II (manufactured by Nippon Bell Co., Ltd.) as a gas adsorption amount measuring device of the constant volume method. From the obtained BET specific surface area, the primary particle diameter was calculated using silica-modified titanium oxide particles as true spheres. The average particle diameter in terms of specific surface area was 5 nm.

(Production Example 2: Preparation of high refractive index layer coating solution 1)
The following constituent materials were sequentially added at 36 ° C. to the sol water dispersion (20% by mass) of silica-modified titanium oxide particles prepared in Production Example 1 above, and finally 1000 parts by mass with pure water, for a high refractive index layer. Coating solution 1 was prepared, and the solution temperature was kept at 36 ° C.

Sol dispersion of 20.0% by mass of silica-modified titanium oxide particles 320 parts As an additive, 10 parts of isopropanol (IPA) 160 parts of 2% by weight of citric acid 4% by weight of polyvinyl alcohol (RS2117, polymerization degree: 1700, Degree of saponification: 99 mol%, manufactured by Kuraray Co., Ltd.) 350 parts Accordingly, 1.0% of isopropanol is contained in the coating liquid 1 for the high refractive index layer.

  The refractive index of the high refractive index layer obtained by applying and drying the high refractive index layer coating solution 1 was 1.81. In addition, the measuring method of a refractive index is as follows (hereinafter the same).

(Production Example 3: Production of low refractive index layer coating solution 1)
430 parts by mass of 10% by mass acidic colloidal silica aqueous solution (Snowtex OXS, average primary particle size: 4-6 nm, secondary particle average particle size: 30 nm, manufactured by Nissan Chemical Industries, Ltd.) and 3% by mass boron 85 parts by mass of an acid aqueous solution, 350 parts by mass of pure water, and an 8% by mass aqueous solution of polyvinyl alcohol which is a water-soluble polymer (PVA-235, polymerization degree: 3500, saponification degree: 88 mol%, manufactured by Kuraray Co., Ltd.) 150 Mass parts were added and mixed at 36 ° C. in this order to prepare a low refractive index layer coating solution 1, and the liquid temperature was kept at 36 ° C. 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.

(Measurement of single film refractive index of each layer)
In order to measure the refractive index, a sample in which each refractive index layer coating solution was applied as a single layer on a substrate was prepared. After cutting this sample into 10 cm × 10 cm, 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.

Example 1
Using a slide hopper coating apparatus capable of coating 15 layers, the high refractive index layer coating solution 1 prepared in Production Example 2 and the low refractive index layer coating solution 1 prepared in Production Example 3 are kept at 36 ° C. (Viscosity of the high refractive index layer coating solution 1: 20 to 50 mPa · s / Viscosity of the high refractive index layer coating solution of the other examples was the same. Viscosity of the low refractive index layer coating solution 1: 150 to 250 mPa) S / Viscosity of low refractive index layer coating solutions of other examples were the same), polyethylene terephthalate film having a thickness of 50 μm (manufactured by Toyobo Co., Ltd., Cosmo Shine (registered trademark) A4300, double-sided adhesive layer, long 200 m × width 210 mm).

  At this time, the lower layer is the low refractive index layer, the uppermost layer (the outermost layer) is the low refractive index layer, and other layers are coated simultaneously so that the high refractive index layer and the low refractive index layer are alternated. (Slide bead application method). Then, it dried so that the film surface temperature might be 80 degreeC.

  In addition, since the easily bonding layer is provided on both surfaces of the said polyethylene terephthalate film, it describes as the "double-sided easily bonding layer" above. By having an easy-adhesion layer on both surfaces, the polyvinyl alcohol is easily adhered onto the base material (polyethylene terephthalate film).

  The film thickness during drying was adjusted so that the lowermost layer was 1510 nm, the outermost layer was 100 nm, the lower refractive index layers other than the lowermost layer and the uppermost layer were 150 nm, and the high refractive index layers were 150 nm.

(Examples 2-7 and Comparative Examples 1-5)
In Comparative Example 1, an infrared shielding film was produced in the same manner as in Example 1 except that the additive of the present invention was not added.

  In Examples 2 to 3 and Comparative Examples 2 and 3, infrared shielding films were produced in the same manner as in Example 1 except that the addition amount of isopropanol as an additive was changed to the addition amount shown in Table 1. .

  In Examples 4 to 7 and Comparative Examples 4 and 5, di2-ethylhexyl-sodium sulfosuccinate (Lapisol (registered trademark) A-30: manufactured by NOF Corporation) was used as an additive. An infrared shielding film was produced in the same manner as in Example 1 except that the adjustment was performed as shown in FIG. The critical micelle concentration of di-2-ethylhexyl-sodium sulfosuccinate is 1%.

<Surface update speed>
The surface update rate of the coating liquid flowing on the slide surface of the slide hopper coating apparatus was calculated by simulation. The simulation was performed by fluid simulation by the finite element method using the software name: Hyperworks. As a result, the surface update speed was 50 to 1500 ms.

<Dynamic surface tension value>
For each of the high refractive index layer coating liquid (liquid temperature 36 ° C.) and each of the low refractive index layer coating liquid (liquid temperature 36 ° C.) prepared above, before the lamination using the slide hopper coating apparatus, bubbles The dynamic surface tension value at 500 ms was evaluated by the pressure method. In addition, KRUS dynamic surface tension meter BP100 was used as a measuring device. The results are shown in Table 1.

<Infrared reflectance>
The infrared shielding films produced in the examples had a top reflectance of 70% between 780 and 2500 nm at all levels, and the TSER of the reflective layer alone was 21%.

<Spot defect evaluation results>
It was visually evaluated whether there was a point defect of 1 mm or more in the coated sample 10 m × 10 m. The results were obtained in the following three steps.

×: 3 or more △: 1-2 pieces ○: 0 pieces

<Discussion>
As shown in Table 1, using a high refractive index layer coating solution and a low refractive index layer coating solution in which the difference in dynamic surface tension at a surface lifetime of 500 ms was controlled to 10 mN / m or less, By simultaneously applying multiple layers, an optical film in which the occurrence of point failures was eliminated could be produced. On the other hand, when the difference in dynamic surface tension at a surface life of 500 ms exceeds 10 mN / m, and a high refractive index layer coating solution and a low refractive index layer coating solution are applied simultaneously on a substrate. The occurrence of point failures could not be suppressed.

  An interesting point in Table 1 is that a point-like failure occurs when the difference in dynamic surface tension at a surface lifetime of 500 ms exceeds even 10 mN / m (Comparative Example 5). In other words, it is suggested that 10 mN / m has a critical significance.

Claims (6)

A method for producing an optical film in which at least two optical functional layers are formed on a substrate,
A control step of controlling the difference in dynamic surface tension of the coating liquid for an optical functional layer to be an adjacent optical functional layer at a surface life of 500 ms to 10 mN / m or less;
A step of forming at least two optical functional layers by simultaneously applying the controlled coating solution for optical functional layers on the substrate;
Have
The manufacturing method of an optical film in which the coating liquid for optical function layers used as the said adjacent optical function layer contains polyvinyl alcohol of a saponification degree which is mutually different. Using two types of coating solutions for the optical function layer, two layers are formed as one unit,
The manufacturing method according to claim 1, wherein the controlled optical functional layer coating solution is applied simultaneously on the substrate so as to laminate a plurality of the units.   The manufacturing method according to claim 1 or 2, wherein the control step includes a step of adding an organic solvent having 1 to 20 carbon atoms to at least one kind of the coating solution for an optical function layer.   The manufacturing method of Claim 3 whose said organic solvent is at least 1 sort (s) selected from the group which consists of alcohol and ether.   The manufacturing method of Claim 3 or 4 which adds the said organic solvent 0.01-10 mass% with respect to the said coating liquid for optical function layers.   The manufacturing method according to any one of claims 1 to 5, wherein the control step includes a step of adding a surfactant to at least one kind of the coating solution for the optical functional layer so as to exceed a critical micelle concentration. .