WO2017051831A1

WO2017051831A1 - Gel for producing low-refractive-index film, production method for gel for producing low-refractive-index film, coating material for producing low-refractive-index film, production method for coating material for producing low-refractive-index film, production method for laminate film, and production method for image display device

Info

Publication number: WO2017051831A1
Application number: PCT/JP2016/077903
Authority: WO
Inventors: 大輔服部; 裕宗春田; 細川　和人
Original assignee: 日東電工株式会社
Priority date: 2015-09-24
Filing date: 2016-09-21
Publication date: 2017-03-30
Also published as: CN108027454A; JP2017061604A

Abstract

The purpose of the present invention is to provide a gel that is for producing a low-refractive-index film, that retains little of a solvent that is used to produce the gel, and that can be used to produce a film that has a low refractive index. In order to achieve said purpose, this gel for producing a low-refractive-index film is characterized in that the gel retains 0.5 g/ml or less of a solvent that is used to produce the gel and in that the low-refractive-index film produced from the gel has a refractive index of 1.25 or less.

Description

Low refractive index film manufacturing gel, low refractive index film manufacturing method, low refractive index film manufacturing paint, low refractive index film manufacturing method, laminated film manufacturing method, and image display device manufacturing method

The present invention relates to a gel for producing a low refractive index film, a method for producing a gel for producing a low refractive index film, a paint for producing a low refractive index film, a method for producing a paint for producing a low refractive index film, a method for producing a laminated film, and an image display. The present invention relates to a device manufacturing method.

Various studies have been conducted on silanol porous body sol solutions that can form void structures using silica compound materials (silicon compound materials) as raw materials. The point common to them is that after the silica compound is once gelled, a pulverized sol solution prepared by pulverizing the gelled silica compound is prepared and coated to form a void structure. . However, when trying to obtain a higher porosity, there is a problem that the film strength of the silanol porous body is remarkably lowered, and it is difficult to easily obtain the silanol porous body industrially. As an example of achieving both high porosity and strength, there is an application example to a lens antireflection layer (see, for example, Patent Documents 1 to 4). In this method, after a void layer is formed on the lens, a high temperature of 150 ° C. or higher is baked for a long time. However, since a gel using tetraethoxysilane (TEOS) as a raw material is inferior in flexibility, There was a problem that a porous body could not be formed on a soft substrate. On the other hand, there is an application example of a void layer in which no firing treatment is performed (for example, see Non-Patent Document 1). However, in this method, the silanol pulverized sol still contains a large amount of residual silanol groups, and no firing treatment is performed after the formation of the void layer, so that the resulting porous body has poor film strength and cannot impart impact resistance. There was a problem.

In order to solve such problems, an attempt has been made to develop a film that replaces the air layer formed by the gaps between the members.

JP 2006-297329 A JP 2006-221144 A JP 2006-011175 A JP 2008-040171 A

In particular, in order to be used for applications such as optical films, it is necessary that the refractive index of the void layer is as low as possible, and specifically, it is desirable that it is 1.25 or less.

On the other hand, as described above, the sol solution for producing the void layer (low refractive index film) is produced using, for example, a gel obtained by gelling a silica compound as a raw material. The solvent for producing this gel is preferably a high boiling point solvent for the progress of the gelation reaction. However, if a high boiling point solvent remains in a large amount in the sol solution, it is difficult to remove the high boiling point solvent when the void layer (low refractive index film) is produced by coating and drying the sol solution thereafter. If a high boiling point solvent remains in the void layer (low refractive index film), it is difficult to develop a low refractive index. The same problem is not limited to gels of silica compounds, but also exists in gels of other materials.

Therefore, the present invention is a low refractive index film manufacturing gel capable of manufacturing a low refractive index film with a small residual amount of the gel manufacturing solvent in the gel, a method for producing a low refractive index film manufacturing gel, An object of the present invention is to provide a coating material for producing a low refractive index film, a method for producing a coating material for producing a low refractive index film, a method for producing a laminated film, and a method for producing an image display device.

In order to achieve the above object, the gel for producing a low refractive index film of the present invention is a gel for use in producing a low refractive index film, and the residual amount of the solvent for producing the gel in the gel is 0.5 g. / Ml or less, and the refractive index of the manufactured low refractive index film is 1.25 or less.

The method for producing a gel for producing a low refractive index film of the present invention comprises a gelation step of gelling the gel raw material in the gel production solvent, and the gel production solvent in the gel as another solvent. It is a manufacturing method of the said gel for low refractive index film | membrane manufacture of this invention including the solvent substitution process to substitute.

The paint for producing a low refractive index film of the present invention is characterized by comprising a pulverized product of the gel for producing a low refractive index film of the present invention and a solvent for producing a low refractive index film.

The method for producing a coating material for producing a low refractive index film according to the present invention comprises: It is a manufacturing method of the coating material for low-refractive-index film manufacture of invention.

The method for producing a laminated film of the present invention is a method for producing a laminated film including a step of forming a low refractive index film on a substrate, and the step of forming the low refractive index film comprises the step of forming the low refractive index film of the present invention. A coating step for coating the coating material for producing a refractive index film on a substrate; and a drying step for drying the coated coating material for producing a low refractive index film.

The method for producing an image display device of the present invention is a method for producing an image display device including a laminated film as an optical member, wherein the laminated film is produced by the method for producing a laminated film of the present invention. To do.

The gel for producing a low refractive index film of the present invention produces a low refractive index film having a refractive index of 1.25 or less because the residual amount of the gel production solvent in the gel is as low as 0.5 g / ml or less. It is possible. Such a gel for producing a low refractive index film of the present invention can be produced, for example, by the method for producing a gel for producing a low refractive index film of the present invention. The gel for producing a low refractive index film of the present invention is produced, for example, by using the gel for producing a low refractive index film of the present invention by using the method for producing the paint for producing a low refractive index film of the present invention. Can do. And it is possible to manufacture a film having a low refractive index of 1.25 or less using the coating material for manufacturing a low refractive index film of the present invention. The use of the coating material for producing a low refractive index film of the present invention is not particularly limited. For example, it can be used in the method for producing a laminated film and the method for producing an image display device of the present invention. The low refractive index film produced using the gel for producing the low refractive index film of the present invention or the coating material for producing the low refractive index film of the present invention may be hereinafter referred to as “low refractive index film of the present invention”. . In addition, the low refractive index film of the present invention can realize a low refractive index of 1.25 or less by having voids. Therefore, hereinafter, the low refractive index film of the present invention may be referred to as “the void layer of the present invention” or simply “the void layer”.

FIG. 1 is a process cross-sectional view schematically showing an example of a method for forming a void layer (low refractive index film) 20 on a substrate 10 using the coating material of the present invention. FIG. 2 is a diagram schematically showing a part of a process for producing a void layer using the coating material of the present invention and an example of an apparatus used therefor. FIG. 3 is a diagram schematically showing a part of a process for producing a void layer using the coating material of the present invention and another example of an apparatus used therefor.

Hereinafter, the present invention will be described more specifically with examples. However, the present invention is not limited or restricted by the following description.

The inventors of the present invention have studied various methods for producing a low refractive index film having a refractive index of 1.25 or less. As a result, the final amount of the solvent for gel production in the gel as a raw material is very small. It has been found that this greatly affects the refractive index of the low refractive index film obtained. In addition, in order to produce a low refractive index film having a refractive index of 1.25 or less, the inventors of the present invention have extremely set the residual amount of the gel production solvent in the gel to 0.5 g / ml or less. The inventors have found that it is effective and have reached the present invention. So far, the low refractive index film has been formed by high-temperature baking treatment at 200 ° C. or higher in order to increase the film strength, and thus the above problem has not been recognized. However, it is very important for the inventors to focus on the remaining amount of the solvent for gel production in order to form a low refractive index film having a film strength under relatively mild conditions of, for example, 200 ° C. or less. I found out. This knowledge is not shown in the prior art including the patent document and the non-patent document, and is a knowledge that the present inventors have found uniquely.

As described above, the reason (mechanism) for producing a film having a low refractive index by reducing the residual amount of the solvent for gel production in the gel is unknown, but for example, it is presumed as follows. That is, as described above, the solvent for gel production is preferably a high boiling point solvent (for example, DMSO [dimethyl sulfoxide] or the like) for the progress of the gelation reaction. Then, when a low refractive index film is produced by applying and drying the sol solution produced from the gel, at a normal drying temperature and drying time (not particularly limited, for example, at 100 ° C. for 1 minute, etc.) It is difficult to completely remove the high boiling solvent. This is because if the drying temperature is too high or the drying time is too long, problems such as deterioration of the substrate may occur. And the said high boiling point solvent remaining at the time of the said coating drying enters between the pulverized products of the gel, the crushed products are slid, and the pulverized products are densely deposited to reduce the porosity. For this reason, it is presumed that a low refractive index is hardly expressed. That is, conversely, if the residual amount of the high boiling point solvent is reduced, such a phenomenon can be suppressed and a low refractive index can be expressed. However, these are examples of the mechanism which is estimated and does not limit this invention at all.

As described above, the residual amount of the solvent for producing the gel in the gel is 0.5 g / ml or less, for example, 0.2 g / ml or less, 0.15 g / ml or less, 0.05 g / ml or less. 0.03 g / ml or less, or 0.02 g / ml or less. The lower limit value of the remaining amount of the solvent for gel production in the gel is not particularly limited, and is, for example, a value exceeding 0, but ideally 0.

The residual amount of the solvent for gel production in the gel can be measured, for example, as follows.

(Method for measuring residual amount of solvent for gel production in gel)
The gel containing the solvent for gel production is immersed in another solvent that can be mixed with the solvent for gel production at an arbitrary ratio for 3 hours or more. Thereafter, the content (g / ml) of the solvent for gel production in the other solvent is measured by gas chromatography. The measured value is estimated to be equal to the remaining amount of the solvent for gel production in the gel at that time. That is, by immersing the gel in another solvent that can be mixed with the gel production solvent in an arbitrary ratio for 3 hours or more, the remaining amount of the gel production solvent in the gel and the other solvent It is presumed that the content of the solvent for gel production in it reached equilibrium and became equal.

In the present invention, the “solvent” (for example, a solvent for producing a gel, a solvent for producing a low refractive index film, etc.) may not dissolve the gel or a pulverized product thereof. Etc. may be dispersed or precipitated in the solvent.

The gel production solvent has a boiling point of 130 ° C. or higher, for example.

The gel production solvent is, for example, a water-soluble solvent. In the present invention, the “water-soluble solvent” refers to a solvent that can be mixed with water at an arbitrary ratio.

In the gel for producing a low refractive index film of the present invention, the gel may be, for example, an inorganic gel. The gel may contain at least one element selected from the group consisting of Si, Mg, Al, Ti, Zn, and Zr, for example. The gel may be, for example, a gel silicon compound. Further, the gel silicon compound may be a gel silicon compound obtained from a silicon compound containing at least a trifunctional or lower saturated bond functional group.

The low refractive index film production gel of the present invention may be, for example, a low refractive index film production gel for producing the low refractive index film on a substrate. The substrate may be, for example, a resin film.

As described above, the method for producing a gel for producing a low refractive index film according to the present invention comprises a gelation step of gelling the gel raw material in the gel production solvent, and a gel production solvent in the gel. And a solvent substitution step of substituting with another solvent. In the solvent replacement step, the other solvent is, for example, the low refractive index film manufacturing solvent. The other solvent is, for example, a solvent capable of dissolving the solvent for gel production. The other solvent is more preferably a solvent that can be mixed with the solvent for gel production at an arbitrary ratio.

The method for producing a gel for producing a low refractive index film of the present invention preferably further includes a gel dividing step of dividing the gel lump into a plurality of pieces prior to the solvent replacement step. In the gel dividing step, the gel is more preferably divided into a three-dimensional structure having a long side of 15 cm or less.

The method for producing a gel for producing a low refractive index film of the present invention may further include an aging step for aging the gel in the solvent for gel production prior to the solvent replacement step. Moreover, you may perform the said gel division | segmentation process after the said aging process. In the aging step, for example, the gel may be aged by incubating in the gel production solvent at 30 ° C. or higher.

As described above, the coating material for producing a low refractive index film of the present invention is characterized by containing the pulverized product of the gel for producing a low refractive index film of the present invention and a solvent for producing a low refractive index film. The solvent for producing the low refractive index film may be, for example, a catalyst capable of dissolving a gel production catalyst, an alcohol component produced by a condensation reaction, water, etc., and an arbitrary ratio with the gel production solvent. Or a solvent that can be mixed in the above.

In the coating material for producing a low refractive index film of the present invention, the gel may be, for example, a gel silicon compound obtained from a silicon compound containing at least a trifunctional or lower saturated bond functional group. Moreover, the pulverized product of the gel may contain residual silanol groups. The paint for producing a low refractive index film of the present invention may be, for example, a silicone sol paint for chemically bonding the pulverized products. The silicon compound may be, for example, a compound represented by the following formula (2).
In formula (2),
X is 2 or 3,
R ¹ and R ² are each a linear or branched alkyl group,
R ¹ and R ² may be the same or different,
R ^{1 s} may be the same as or different from each other when X is 2.
R ² may be the same as or different from each other.

In the coating material for producing a low refractive index film of the present invention, the volume average particle diameter of the gel pulverized product may be, for example, 0.05 to 2.00 μm.

The paint for producing a low refractive index film of the present invention may contain, for example, a catalyst for chemically bonding the pulverized products.

The method for producing a coating material for producing a low refractive index film according to the present invention comprises, as described above, a grinding step for grinding the gel, and a mixing step for mixing the ground product of the gel and the solvent for producing the low refractive index film. Including. The pulverization step of pulverizing the gel may be performed, for example, in the low refractive index film manufacturing solvent. The low refractive index film-producing solvent is, for example, a solvent capable of dissolving the gel-producing catalyst, the alcohol component produced by the condensation reaction, water, etc., and is mixed with the gel-producing solvent at an arbitrary ratio. Possible solvents are more preferred.

As described above, the method for producing a laminated film of the present invention comprises: a coating process for coating the coating material for producing a low refractive index film of the present invention on a substrate; and the coated coating material for producing a low refractive index film. And a drying step for drying. The method for producing a laminated film of the present invention may further include a crosslinking reaction step in which the pulverized product is subjected to a crosslinking reaction. Further, the coating material for producing a low refractive index film may contain a catalyst for chemically bonding the pulverized products, and the crosslinking reaction may be a crosslinking reaction by the catalyst. In addition, the low refractive index film (void layer) formed by the method for producing a laminated film of the present invention has a chemical structure in which one type or plural types of structural units forming a fine void structure are chemically coupled to each other. It may be combined with.

In the laminated film of the present invention, for example, the bonds between the constituent units constituting the low refractive index film (void layer) may include hydrogen bonds or covalent bonds. The structural unit forming the void layer may have a structure having at least one of a particle shape, a fiber shape, and a flat plate shape, for example. The particulate and flat structural units may be made of an inorganic substance, for example. In addition, the constituent element of the particulate structural unit may include at least one element selected from the group consisting of Si, Mg, Al, Ti, Zn, and Zr, for example. The structure (constituent unit) forming the particulate form may be a real particle or a hollow particle. Specific examples include silicone particles, silicone particles having fine pores, silica hollow nanoparticles, silica hollow nanoballoons, and the like. The fibrous structural unit is, for example, a nanofiber having a diameter of nano-size, and specifically includes cellulose nanofiber and alumina nanofiber. Examples of the plate-like structural unit include nanoclay, and specifically, nano-sized bentonite (for example, Kunipia F [trade name]) and the like. The fibrous structural unit is not particularly limited, but for example, from the group consisting of carbon nanofiber, cellulose nanofiber, alumina nanofiber, chitin nanofiber, chitosan nanofiber, polymer nanofiber, glass nanofiber, and silica nanofiber. It may be at least one fibrous material selected. Moreover, in the laminated film of the present invention, one type or a plurality of types of structural units forming the fine void structure are chemically bonded directly or indirectly through catalytic action as described above. It may contain the part which is. In the void layer in the laminated film of the present invention, for example, as described above, at least a part of the one type or a plurality of types of structural units may be chemically bonded via a catalytic action. In this case, for example, even if the structural units are in contact with each other, there may be a portion that is not chemically bonded. Further, in the present invention, the structural units are “indirectly bonded” means that the structural units are bonded to each other through a small amount of a binder component equal to or less than the structural unit amount. The structural units are “directly bonded” means that the structural units are directly bonded without using a binder component or the like.

In the present invention, the shape of “particles” (for example, particles of the pulverized product) is not particularly limited, and may be, for example, spherical or non-spherical. In the present invention, the pulverized particles may be, for example, sol-gel bead-like particles, or may be nanoparticles (hollow nanosilica / nanoballoon particles), nanofibers, or the like as described above.

Hereinafter, regarding the present invention, the material for the low refractive index film-producing gel of the present invention (hereinafter sometimes referred to as “the gel of the present invention” or simply “gel”) and the pulverized product thereof are gel-like. Description will be made mainly on the case of a silicon compound (typically silica). In the following, when the material of the low refractive index film (void layer) of the present invention is a silicon compound (typically silica), it is referred to as “silicone porous body of the present invention” or simply “silicone porous body”. There is a case. However, as described above, the material for the low refractive index film manufacturing gel, the low refractive index film manufacturing paint, and the low refractive index film (void layer) of the present invention is arbitrary and is not limited to the silicon compound alone. When the material is other than a silicon compound, the following explanation of the silicon compound can be cited unless there is a particular circumstance.

[1. Low Refractive Index Film Manufacturing Paint, Low Refractive Index Film Manufacturing Gel, and Their Manufacturing Method]
The material of the coating material for producing a low refractive index film of the present invention (hereinafter sometimes simply referred to as “the coating material of the present invention”) is not particularly limited as described above, but is optional. A paint containing a pulverized product of a gel-like silicon compound obtained from a silicon compound containing a saturated bond functional group, a solvent, the pulverized product containing residual silanol groups, and chemically bonding the pulverized products to each other It may be. Hereinafter, such a paint may be referred to as “the silicone sol paint of the present invention” or simply “silicone sol paint”. In addition, “including a saturated bond functional group of 3 functional groups or less” means that the silicon compound has 3 or less functional groups, and these functional groups are saturated bonded to silicon (Si). Means that.

The method for producing a coating material of the present invention is, for example, the method for producing the silicone sol coating material of the present invention, in which a pulverized product and dispersion of a gel-like silicon compound obtained from a silicon compound containing a saturated bond functional group having at least three functional groups or less. The process of mixing with a medium may be included.

The paint of the present invention can be used for the production of the low refractive index film (void layer, typically a silicone porous body) of the present invention having the same function (low refractive property) as the air layer. The paint of the present invention includes, for example, a pulverized product of the gel-like silicon compound, and the pulverized product has the three-dimensional structure of the uncrushed gel-like silicon compound destroyed, and the uncrushed gel-like silicon compound. A new three-dimensional structure different from that can be formed. For this reason, for example, the coating film (silicone porous body precursor) formed using the coating material has a new pore structure (newly formed) that cannot be obtained by the layer formed using the unground gelatinous silicon compound. A layer in which a void structure is formed. Thereby, the layer can exhibit the same function as the air layer (for example, the same low refractive index). In the paint of the present invention, for example, since the pulverized product contains residual silanol groups, the pulverized product is formed after a new three-dimensional structure is formed as the coating film (precursor of silicone porous material). Can be chemically coupled. Thereby, although the formed porous silicon body has a structure having voids, sufficient strength and flexibility can be maintained. For this reason, according to this invention, a silicone porous body can be easily and simply provided to various objects. The coating material of the present invention is very useful, for example, in the production of the low refractive index film (porous structure) that can be used as a substitute for the air layer. Further, in the case of the air layer, for example, it is necessary to form an air layer between the members by stacking the members with a gap provided therebetween via a spacer or the like. However, the silicone porous body formed using the coating material of the present invention can exhibit the same function as the air layer only by disposing it at the target site. Therefore, as described above, functions similar to the air layer can be imparted to various objects more easily and simply than forming the air layer.

The paint of the present invention can also be referred to as, for example, a paint for forming a low refractive index film or a paint for forming a low refractive layer. The paint of the present invention contains a pulverized product of the gel of the present invention.

In the paint of the present invention, the volume average particle diameter of the pulverized product is not particularly limited, and the lower limit thereof is, for example, 0.05 μm or more, 0.10 μm or more, 0.20 μm or more, 0.40 μm or more, The upper limit is, for example, 2.00 μm or less, 1.50 μm or less, 1.00 μm or less, and the ranges thereof are, for example, 0.05 μm to 2.00 μm, 0.20 μm to 1.50 μm, 0.40 μm to 1. 00 μm. The volume average particle diameter indicates a particle size variation of the pulverized product in the paint of the present invention. The particle size distribution can be measured by, for example, a particle size distribution evaluation apparatus such as a dynamic light scattering method or a laser diffraction method, and an electron microscope such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). .

In the paint of the present invention, the particle size distribution of the pulverized product is not particularly limited. For example, particles having a particle size of 0.4 μm to 1 μm are 50 to 99.9 wt%, 80 to 99.8 wt%, It is 90 to 99.7% by weight, or particles having a particle size of 1 μm to 2 μm are 0.1 to 50% by weight, 0.2 to 20% by weight, and 0.3 to 10% by weight. The said particle size distribution shows the particle size variation of the said ground material in the coating material of this invention. The particle size distribution can be measured by, for example, a particle size distribution evaluation apparatus or an electron microscope.

In the paint of the present invention, the silicon compound is, for example, a compound represented by the following formula (2).

In the formula (2), for example, X is 2, 3 or 4,
R ¹ and R ² are each a linear or branched alkyl group,
R ¹ and R ² may be the same or different,
R ^{1 s} may be the same as or different from each other when X is 2.
R ² may be the same as or different from each other.

The X and R ¹ are, for example, the same as X and R ¹ in the formula (1) described later. In addition, the ^{R 2} is, for example, can be exemplified for ^{R 1} is incorporated in the formula (1) described later.

Specific examples of the silicon compound represented by the formula (2) include a compound represented by the following formula (2 ′) in which X is 3. In the following formula (2 ′), R ¹ and R ² are the same as those in the formula (2), respectively. When R ¹ and R ² are methyl groups, the silicon compound is trimethoxy (methyl) silane (hereinafter also referred to as “MTMS”).

In the paint of the present invention, the concentration of the pulverized product of the gel of the present invention in the solvent (dispersion medium) is not particularly limited, and is, for example, 0.3 to 50% (v / v), 0.5 to 30%. (V / v), 1.0 to 10% (v / v). When the concentration of the pulverized product is too high, for example, the fluidity of the sol solution is remarkably lowered, and there is a possibility of generating aggregates and coating streaks during coating. On the other hand, if the concentration of the pulverized product is too low, for example, not only does it take a considerable time to dry the solvent, but also the residual solvent immediately after drying increases, so the porosity may decrease. . In the coating material of the present invention, for example, the silicon atoms contained are preferably siloxane bonded. As a specific example, the proportion of unbonded silicon atoms (that is, residual silanol) in the total silicon atoms contained in the paint is, for example, less than 50%, 30% or less, or 15% or less.

The physical properties of the paint of the present invention are not particularly limited. The shear viscosity of the paint is, for example, a viscosity of 100 cPa · s or less, a viscosity of 10 cPa · s or less, and a viscosity of 1 cPa · s or less at a shear rate of 10001 / s. If the shear viscosity is too high, for example, coating streaks may occur, and problems such as a decrease in the transfer rate of gravure coating may be observed. On the other hand, when the shear viscosity is too low, for example, the wet coating thickness at the time of coating cannot be increased, and a desired thickness may not be obtained after drying.

In the paint of the present invention, the solvent for producing the low refractive index film (hereinafter also referred to as “coating solvent”) is not particularly limited, and examples thereof include a grinding solvent described later. Examples of the coating solvent include organic solvents having a boiling point of 130 ° C. or lower. Specific examples include IPA [isopropyl alcohol], ethanol, methanol, n-butanol, 2-butanol, isobutyl alcohol and the like.

Since the paint of the present invention is, for example, the sol-like pulverized material dispersed in the solvent, it is also referred to as “sol particle liquid”, for example. The coating material of the present invention can continuously form a void layer having a film strength of a certain level or more by performing chemical crosslinking by a bonding step after coating and drying on a substrate, for example. . In the present invention, “sol” means that the three-dimensional structure of the gel is pulverized so that the pulverized product (that is, silica sol particles having a nano three-dimensional structure retaining a part of the void structure) is dispersed in the solvent. The state which shows fluidity.

Hereinafter, examples of the method for producing the paint of the present invention will be described, but the following explanation can be used for the paint of the present invention.

As described above, the method for producing a paint of the present invention includes a step of mixing the pulverized product of the gel for producing a low refractive index film of the present invention and the solvent for producing a low refractive index film. The mixing step may be, for example, a step of mixing a pulverized product of a gel-like silicon compound obtained from a silicon compound containing a saturated bond functional group having at least three functional groups and a dispersion medium. In the present invention, the pulverized product of the gel-like silicon compound can be obtained from the gel-like silicon compound by, for example, a pulverization step described later. For this reason, the said gel-like silicon compound can also be called the 1st coating material raw material of the coating material of this invention, for example. Moreover, the pulverized product of the gel-like silicon compound can be obtained, for example, from the gel-like silicon compound after the aging treatment in which the aging step described later is performed by a pulverizing step described later. For this reason, the said gel-like silicon compound after the said aging treatment can also be called the 2nd coating material raw material of the coating material of this invention, for example.

In the method for producing a paint of the present invention, the gelation step includes, for example, gelling a silicon compound containing at least a trifunctional or lower saturated bond functional group in a solvent to obtain a gel silicon compound (first paint raw material). It may be a process of generating. The gelation step is, for example, a step of gelling the monomer silicon compound by a dehydration condensation reaction in the presence of a dehydration condensation catalyst, whereby a gel-like silicon compound is obtained. As described above, the gel-like silicon compound has a residual silanol group, and the residual silanol group is appropriately adjusted according to a chemical bond between pulverized products of the gel-like silicon compound described later. Is preferred.

In the gelation step, the silicon compound is not particularly limited as long as it is gelled by a dehydration condensation reaction. By the dehydration condensation, for example, the silicon compounds are bonded. The bond between the silicon compounds is, for example, a hydrogen bond or an intermolecular force bond.

Examples of the silicon compound include a silicon compound represented by the following formula (1). Since the silicon compound of the following formula (1) has a hydroxyl group, between the silicon compounds of the following formula (1), for example, a hydrogen bond or an intermolecular force bond is possible via each hydroxyl group.

In the formula (1), for example, X is 2, 3 or 4, and R ¹ is a linear or branched alkyl group. The carbon number of R ¹ is, for example, 1-6, 1-4, 1-2. Examples of the linear alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, and a hexyl group. Examples of the branched alkyl group include an isopropyl group and an isobutyl group. X is, for example, 3 or 4.

Specific examples of the silicon compound represented by the formula (1) include a compound represented by the following formula (1 ′) in which X is 3. In the following formula (1 ′), R ¹ is the same as in the above formula (1), and is, for example, a methyl group. When R ¹ is a methyl group, the silicon compound is tris (hydroxy) methylsilane. When X is 3, the silicon compound is, for example, a trifunctional silane having three functional groups.

Further, specific examples of the silicon compound represented by the formula (1) include a compound in which X is 4. In this case, the silicon compound is, for example, a tetrafunctional silane having four functional groups.

The silicon compound may be, for example, a precursor that forms the silicon compound of the formula (1) by hydrolysis. The precursor is not particularly limited as long as it can generate the silicon compound by hydrolysis, and specific examples thereof include a compound represented by the formula (2).

When the silicon compound is a precursor represented by the formula (2), the production method of the present invention may include, for example, a step of hydrolyzing the precursor prior to the gelation step.

The hydrolysis method is not particularly limited, and can be performed, for example, by a chemical reaction in the presence of a catalyst. Examples of the catalyst include acids such as oxalic acid and acetic acid. The hydrolysis reaction can be performed, for example, by slowly dropping an aqueous solution of oxalic acid into the dimethyl sulfoxide solution of the silicon compound precursor in a room temperature environment and then stirring the mixture for about 30 minutes. When hydrolyzing the silicon compound precursor, for example, by completely hydrolyzing the alkoxy group of the silicon compound precursor, further heating and immobilization after gelation / aging / void structure formation, It can be expressed efficiently.

In the present invention, examples of the silicon compound include a hydrolyzate of trimethoxy (methyl) silane.

The silicon compound of the monomer is not particularly limited, and can be appropriately selected according to, for example, the use of the silicone porous body to be produced. In the production of the silicone porous body, for example, when importance is attached to low refractive index, the silicon compound is preferably the trifunctional silane from the viewpoint of excellent low refractive index, and also has strength (for example, scratch resistance). When importance is attached to the above, the tetrafunctional silane is preferred from the viewpoint of excellent scratch resistance. Moreover, the said silicon compound used as the raw material of the said gel-like silicon compound may use only 1 type, for example, and may use 2 or more types together. As a specific example, the silicon compound may include, for example, only the trifunctional silane, may include only the tetrafunctional silane, may include both the trifunctional silane and the tetrafunctional silane, Furthermore, other silicon compounds may be included. When two or more types of silicon compounds are used as the silicon compound, the ratio is not particularly limited and can be set as appropriate.

Then, the gel of the present invention is produced by a gelation step of gelling the silicon compound in the gel production solvent and a solvent substitution step of substituting the solvent for gel production in the gel with another solvent. can do. The raw material of the gel of the present invention is not limited to the silicon compound as described above and is arbitrary, but the silicon compound will be described as a representative example.

The gelation of the silicon compound can be performed, for example, by a dehydration condensation reaction between the silicon compounds. The dehydration condensation reaction is preferably performed, for example, in the presence of a catalyst. Examples of the catalyst include acid catalysts such as hydrochloric acid, oxalic acid, and sulfuric acid, and ammonia, potassium hydroxide, sodium hydroxide, ammonium hydroxide, and the like. And a dehydration condensation catalyst such as a base catalyst. The dehydration condensation catalyst may be an acid catalyst or a base catalyst, but a base catalyst is preferred. In the dehydration condensation reaction, the amount of the catalyst added to the silicon compound is not particularly limited, and the catalyst is, for example, 0.01 to 10 mol, 0.05 to 7 mol, relative to 1 mol of the silicon compound, 0.1 to 5 moles.

Gelation of the raw material (typically silicon compound) of the gel of the present invention is performed, for example, in the gel production solvent as described above. The gel production solvent may be, for example, one type or a combination of two or more types. The ratio of the gel raw material in the solvent is not particularly limited. Examples of the solvent for gel production include dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), N, N-dimethylacetamide (DMAc), dimethylformamide (DMF), γ-butyllactone (GBL), acetonitrile (MeCN). ), Ethylene glycol monoethyl ether (EGEE), and the like. Further, for example, a mixed solvent obtained by mixing an alcohol solvent (for example, isopropyl alcohol, isobutyl alcohol, n-butyl alcohol, pentanol [n-pentyl alcohol], etc.) with one or more of these solvents, You may use as said solvent for gel manufacture. The gel production solvent is particularly preferably one or more of N-methylpyrrolidone, dimethyl sulfoxide, dimethylformamide (DMF), γ-butyrolactone, and N, N-dimethylacetamide.

The gelation conditions are not particularly limited. The gelation conditions vary depending on the type of gel raw material and the like. For example, in the case of the silicon compound, the treatment temperature for the gel production solvent containing the gel raw material is, for example, 20 to 30 ° C., 22 The processing time is, for example, 1 to 60 minutes, 5 to 40 minutes, and 10 to 30 minutes. When performing the said dehydration condensation reaction, the process conditions in particular are not restrict | limited, These illustrations can be used. By performing the gelation, for example, a siloxane bond grows, primary particles of the silicon compound are formed, and further the reaction proceeds, whereby the primary particles are linked in a bead shape to form a three-dimensional gel. Generated.

The gel form of the gel silicon compound obtained in the gelation step is not particularly limited. “Gel” generally refers to a solidified state in which a solute has a structure in which it loses independent motility due to interaction and aggregates. In addition, among gels, in general, a wet gel is one in which the solute constituting the skeleton of the gel is integrated in a form containing a solvent, and the surface of the solute is moistened by the solvent. Xerogel refers to a solvent in which the solute has a network structure with voids. In the present invention, for example, wet gel is preferably used as the gel silicon compound. The remaining silanol group of the gel-like silicon compound is not particularly limited, and for example, the ranges described later can be exemplified similarly.

The gel-like silicon compound obtained by the gelation may be subjected to, for example, the solvent replacement step and the pulverization step as it is, but may be subjected to an aging treatment in the aging step before the pulverization step. In the aging step, the conditions for the aging treatment are not particularly limited. For example, the gel-like silicon compound may be incubated in a solvent at a predetermined temperature. According to the aging treatment, for example, the gel-like silicon compound having a three-dimensional structure obtained by gelation can further grow the primary particles, thereby increasing the size of the particles themselves. It is. As a result, the contact state of the neck portion where the particles are in contact can be increased from point contact to surface contact, for example. The gel-like silicon compound subjected to the aging treatment as described above, for example, increases the strength of the gel itself, and as a result, further improves the strength of the three-dimensional basic structure of the pulverized product after pulverization. it can. Thereby, when a coating film is formed using the coating material of the present invention, for example, even in the drying step after coating, the pore size of the void structure in which the three-dimensional basic structure is deposited is in the drying step. Shrinkage can be suppressed as the solvent in the resulting coating film volatilizes.

The lower limit of the temperature of the aging treatment is, for example, 30 ° C. or more, 35 ° C. or more, 40 ° C. or more, and the upper limit thereof is, for example, 80 ° C. or less, 75 ° C. or less, 70 ° C. or less. For example, 30 to 80 ° C, 35 to 75 ° C, 40 to 70 ° C. The predetermined time is not particularly limited, and the lower limit thereof is, for example, 5 hours or more, 10 hours or more, 15 hours or more, and the upper limit thereof is, for example, 50 hours or less, 40 hours or less, 30 hours or less. The range is, for example, 5 to 50 hours, 10 to 40 hours, 15 to 30 hours. The optimum conditions for aging can be set, for example, as described above, such that the gel-like silicon compound can increase the size of the primary particles and increase the contact area of the neck portion. preferable. In the aging step, the temperature of the aging treatment preferably takes into account, for example, the boiling point of the solvent used. In the aging treatment, for example, if the aging temperature is too high, the solvent is excessively volatilized, and there is a possibility that problems such as closing of the pores of the three-dimensional void structure occur due to the concentration of the coating solution. is there. On the other hand, in the aging treatment, for example, if the aging temperature is too low, the effect due to the aging is not sufficiently obtained, temperature variation with time of the mass production process increases, and a product with poor quality may be produced. There is.

In the aging treatment, for example, the same solvent as in the gelation step can be used. Specifically, the aging treatment is performed as it is on the reaction product after gelation (that is, the gel production solvent containing the gel). Is preferred. The number of moles of residual silanol groups contained in the gelled silicon compound that has been subjected to aging treatment after gelation is, for example, the number of moles of alkoxy groups in the raw material used for gelation (for example, the silicon compound or its precursor). Is the ratio of residual silanol groups when the value is 100, the lower limit is, for example, 1% or more, 3% or more, 5% or more, and the upper limit is, for example, 50% or less, 40% or less, 30% The range is, for example, 1 to 50%, 3 to 40%, and 5 to 30%. For the purpose of increasing the hardness of the gel silicon compound, for example, the lower the number of moles of residual silanol groups, the better. If the number of residual silanol groups is too high, for example, in the formation of the silicone porous body, there is a possibility that the void structure cannot be retained before the precursor of the silicone porous body is crosslinked. On the other hand, if the number of moles of residual silanol groups is too low, for example, in the bonding step, the precursor of the silicone porous body cannot be crosslinked, and sufficient film strength may not be imparted. The above is an example of residual silanol groups. For example, when the silicon compound modified with various reactive functional groups is used as the raw material of the gel silicon compound, However, the same phenomenon can be applied.

Next, a solvent replacement step is performed in which the solvent for gel production in the gel of the present invention is replaced with another solvent. As described above, the other solvent is preferably the solvent for producing the low refractive index film (coating solvent). The method of the solvent replacement step is not particularly limited, and can be performed as follows, for example. That is, first, the gel of the present invention is immersed or brought into contact with the other solvent, and the gel production catalyst, the alcohol component produced by the condensation reaction, water, etc. in the gel are dissolved in the other solvent. . Thereafter, the solvent in which the gel is immersed or contacted is discarded, and the gel is immersed or contacted again in a new solvent. This is repeated until the remaining amount of the solvent for gel production in the gel reaches a desired amount (the upper limit is 0.5 g / ml). The immersion time per time is, for example, 0.5 hours or more, 1 hour or more, or 1.5 hours or more, and the upper limit is not particularly limited, but is, for example, 10 hours or less. Further, the immersion of the solvent may be supported by continuous contact of the solvent with the gel. The temperature during the immersion is not particularly limited, and may be, for example, 20 to 70 ° C., 25 to 65 ° C., or 30 to 60 ° C. When heating is performed, the solvent replacement proceeds quickly, and the amount of solvent necessary for the replacement may be small. However, the solvent replacement may be simply performed at room temperature.

Further, as described above, it is preferable to perform a gel dividing step of dividing the gel lump into a plurality of pieces prior to the solvent replacement step. In the gel dividing step, the gel is more preferably divided into a three-dimensional structure having a long side of 15 cm or less. Thereby, the solvent for gel production in the gel is easily eluted in the other solvent, and the residual amount of the solvent for gel production in the gel is easily lowered. The method for dividing the gel lump into a plurality of pieces is not particularly limited, and for example, general pulverization, cutting, or the like may be used. Further, the “long side” refers to the length of the portion having the largest length in the three-dimensional structure. The long side is, for example, 15 cm or less, 10 cm or less, or 5 cm or less, and the lower limit is, for example, 0.005 cm or more, 0.01 cm or more, or 0.02 cm or more.

Thus, after producing the gel for producing a low refractive index film of the present invention, a pulverizing step for pulverizing the gel, and a mixing step for mixing the pulverized product of the gel and the solvent for producing the low refractive index film. The coating material for producing a low refractive index film of the present invention can be produced. The pulverization may be performed, for example, on the gel after the gelation step (typically a gel-like silicon compound, the first coating material raw material), and further after the aging treatment, the gel after the aging (Typically, it may be applied to a gel-like silicon compound, a second paint raw material).

The pulverization step can be performed, for example, in a pulverizing solvent. The pulverizing solvent may be the same as the low refractive index film manufacturing solvent (coating solvent), for example. The grinding solvent is not particularly limited, and for example, an organic solvent can be used. Examples of the organic solvent include solvents having a boiling point of 130 ° C. or lower. Specific examples include isopropyl alcohol (IPA), ethanol, methanol, n-butanol, 2-butanol, isobutyl alcohol, pentyl alcohol, propylene glycol monomethyl ether (PGME), methyl cellosolve, acetone and the like. The pulverizing solvent may be, for example, one type or a combination of two or more types. In particular, isopropyl alcohol (IPA), ethanol, n-butanol, 2-butanol, isobutyl alcohol, pentyl alcohol, propylene glycol monomethyl ether (PGME), and methyl cellosolve are preferable from the viewpoint of low volatility at room temperature.

The combination of the gelling solvent and the grinding solvent is not particularly limited. For example, a combination of DMSO and IPA, a combination of DMSO and ethanol, a combination of DMSO and isobutyl alcohol, DMSO and n-butanol and the like. And the like. Thus, by replacing the gelling solvent with the grinding solvent (coating solvent), for example, a more uniform coating film can be formed in the coating film formation described below.

The method for pulverizing the gel is not particularly limited, and can be performed by, for example, an ultrasonic homogenizer, a high-speed rotation homogenizer, a pulverizer using other cavitation phenomenon, or a wet atomizer that obliquely collides liquids at high pressure. . A device for performing media grinding such as a ball mill physically destroys the void structure of the gel at the time of grinding, whereas a cavitation type grinding device preferable for the present invention such as a homogenizer is, for example, a gel-less system. The relatively weakly bonded silica particle bonding surface already contained in the three-dimensional structure is peeled off with a high shear force. Thus, by pulverizing the gel-like silicon compound, a new sol three-dimensional structure is obtained, and the three-dimensional structure has, for example, a void structure having a certain range of particle size distribution in the formation of a coating film. It can be retained, and the void structure can be re-formed by deposition during coating and drying. The conditions for the pulverization are not particularly limited. For example, it is preferable that the gel can be pulverized without volatilizing the solvent by instantaneously applying a high-speed flow. For example, it is preferable to grind so as to obtain a pulverized product having a particle size variation as described above (for example, a volume average particle size or a particle size distribution). If the amount of work such as pulverization time and strength is insufficient, for example, coarse particles remain, and fine pores cannot be formed, appearance defects increase, and high quality may not be obtained. is there. On the other hand, when the work amount is excessive, for example, the sol particles are finer than the desired particle size distribution, and the void size deposited after coating / drying may become fine and may not satisfy the desired porosity. .

The ratio of residual silanol groups contained in the pulverized product after the pulverization step is not particularly limited, and is, for example, the same as the range exemplified for the gel silicon compound after the aging treatment.

After the pulverization step, the ratio of the pulverized product in the solvent containing the pulverized product is not particularly limited, and examples thereof include the conditions for the paint of the present invention described above. The ratio may be, for example, a condition of the solvent itself containing the pulverized product after the pulverization step, or may be a condition adjusted after the pulverization step and before being used as the paint.

The coating material of the present invention can be produced, for example, using the first coating material or the second coating material as described above. As described above, the first coating material raw material may contain, for example, a gel-like silicon compound obtained from a silicon compound containing at least a trifunctional or lower saturated bond functional group. The method for producing the first coating material raw material includes, for example, a gelation step in which the silicon compound is gelled in a solvent to produce a gel silicon compound. For example, the gel state after the gelation step described above The description of silicon compounds can be incorporated. As described above, the second coating material raw material includes, for example, a gel-like material obtained from a silicon compound containing a saturated bond functional group having at least three functional groups and a gel-like silicon compound subjected to aging treatment. May be. The method for producing the second coating material raw material includes, for example, an aging step of aging a gel-like silicon compound obtained from the silicon compound in a solvent. For example, the gel-like silicon compound after the aging step described above The description can be incorporated.

As described above, the low refractive index film-producing gel of the present invention can be produced, and the low refractive index film-producing paint of the present invention containing the pulverized product and a solvent (for example, a dispersion medium) can be produced. it can. Furthermore, a catalyst for chemically bonding the pulverized products may be added to the paint of the present invention during or after each of the production steps. With this catalyst, for example, the pulverized products can be chemically bonded in a bonding step described later. The catalyst may be, for example, a catalyst that promotes cross-linking between the pulverized products. As a chemical reaction for chemically bonding the pulverized products, for example, it is preferable to use a dehydration condensation reaction of residual silanol groups contained in silica sol molecules. By promoting the reaction between the hydroxyl groups of the silanol group with the catalyst, for example, continuous film formation that cures the void structure in a short time is possible. Examples of the catalyst include a photoactive catalyst and a thermally active catalyst. According to the photoactive catalyst, for example, the pulverized products can be chemically bonded (for example, crosslinked) without being heated. According to this, for example, since shrinkage due to heating hardly occurs, a higher porosity can be maintained. In addition to or instead of the catalyst, a substance that generates a catalyst (catalyst generator) may be used. For example, the catalyst may be a crosslinking reaction accelerator, and the catalyst generator may be a substance that generates the crosslinking reaction accelerator. For example, in addition to or instead of the photoactive catalyst, a substance that generates a catalyst by light (photocatalyst generator) may be used, or in addition to or instead of the thermally active catalyst A substance that generates water (thermal catalyst generator) may be used. The photocatalyst generator is not particularly limited, and examples thereof include a photobase generator (a catalyst that generates a basic catalyst by light irradiation), a photoacid generator (a substance that generates an acidic catalyst by light irradiation), and the like. A photobase generator is preferred. Examples of the photobase generator include 9-anthrylmethyl N, N-diethylcarbamate (trade name WPBG-018), (E) -1- [3- (2- Hydroxyphenyl) -2-propenoyl] piperidine ((E) -1- [3- (2-hydroxyphenyl) -2-propenoyl] piperidine, trade name WPBG-027), 1- (anthraquinone-2-yl) ethyl imidazolecarboxy Rate (1- (anthraquinon-2-yl) ethyl imidazolecarboxylate, trade name WPBG-140), 2-nitrophenylmethyl 4-methacryloyloxypiperidine-1-carboxylate (trade name WPBG-165), 1,2-diisopropyl- 3- [bis (dimethylamino) methylene] guanidium 2- (3-benzoylphenyl) propionate (trade name WPBG-266), 1 , 2-dicyclohexyl-4,4,5,5-tetramethylbiguanidinium n-butyltriphenylborate (trade name WPBG-300) and 2- (9-oxoxanthen-2-yl) propionic acid 1, 5,7-triazabicyclo [4.4.0] dec-5-ene (Tokyo Chemical Industry Co., Ltd.), a compound containing 4-piperidinemethanol (trade name HDPD-PB100: manufactured by Heraeus), and the like. The trade names including “WPBG” are trade names of Wako Pure Chemical Industries, Ltd. Examples of the photoacid generator include aromatic sulfonium salts (trade name SP-170: ADEKA), triarylsulfonium salts (trade name CPI101A: San Apro), and aromatic iodonium salts (trade name Irgacure 250: Ciba Japan). Company). The catalyst for chemically bonding the fine pore particles is not limited to the photoactive catalyst and the photocatalyst generator, and may be a thermal catalyst or a thermal catalyst generator such as urea. Examples of the catalyst for chemically bonding the pulverized materials include basic catalysts such as potassium hydroxide, sodium hydroxide and ammonium hydroxide, and acid catalysts such as hydrochloric acid, acetic acid and oxalic acid. Of these, base catalysts are preferred. The catalyst for chemically bonding the pulverized materials is used, for example, by adding to the sol particle liquid (for example, suspension) containing the pulverized material immediately before coating, or mixing the catalyst in a solvent. It can be used as a liquid. The mixed liquid may be, for example, a coating liquid that is directly added and dissolved in the sol particle liquid, a solution in which the catalyst is dissolved in a solvent, or a dispersion liquid in which the catalyst is dispersed in a solvent. The solvent is not particularly limited, and examples thereof include various organic solvents, water, and a buffer solution.

[2. Usage of paint for manufacturing low refractive index film]
Examples of the method of using the coating material of the present invention will exemplify a method for producing a low refractive index film (silicone porous material of the present invention) mainly formed of a silicone porous material, but the present invention is not limited thereto. . As described above, the material of the low refractive index film of the present invention is arbitrary. In the case where the material is other than the porous silicone material, the following description of the porous silicone material can be used unless there are special circumstances.

In the method for producing a low refractive index film (void layer, typically a porous silicone body) of the present invention, for example, the precursor of the low refractive index film (void layer) is formed using the paint of the present invention. A precursor forming step, and a bonding step of chemically bonding the pulverized materials of the paint contained in the precursor. The precursor can also be referred to as a coating film, for example.

According to the method for producing the low refractive index film (void layer), for example, a porous structure having the same function as the air layer is formed. The reason is estimated as follows, for example, but the present invention is not limited to this estimation.

Since the paint of the present invention used in the method for producing the low refractive index film (void layer) contains a pulverized product of the gel of the present invention (for example, a gel-like silicon compound), the three-dimensional structure of the gel is It is in a state of being distributed in a three-dimensional basic structure. For this reason, in the manufacturing method of the low refractive index film, for example, when the precursor (for example, coating film) is formed using the paint, the three-dimensional basic structure is deposited, and based on the three-dimensional basic structure. A void structure is formed. That is, according to the manufacturing method of the low refractive index film, a new three-dimensional structure formed from the pulverized product of the three-dimensional basic structure, which is different from the three-dimensional structure of the gel silicon compound, is formed. In the method for producing the low refractive index film (void layer), the new three-dimensional structure is fixed in order to chemically bond the pulverized products. For this reason, although the said low refractive index film | membrane obtained by the manufacturing method of the said low refractive index film | membrane is a structure which has a space | gap, it can maintain sufficient intensity | strength and flexibility. The low refractive index film of the present invention can be used for products in a wide range of fields such as a heat insulating material, a sound absorbing material, an optical member, an ink image receiving layer, etc. A laminated film can be produced.

The production method of the low refractive index film (void layer, typically silicone porous body) of the present invention can be referred to the description of the paint of the present invention unless otherwise specified.

In the step of forming the precursor of the low refractive index film, for example, the paint of the present invention is applied onto the substrate. The coating material of the present invention is, for example, coated on a base material, dried the coated film, and then chemically bonded (for example, cross-linked) between the pulverized products by the bonding step, thereby achieving a certain level or more. It is possible to continuously form a void layer having a film strength of 10 nm.

The coating amount of the coating material on the substrate is not particularly limited, and can be appropriately set according to, for example, the desired thickness of the low refractive index film. As a specific example, when the low refractive index film having a thickness of 0.1 to 1000 μm is formed, the coating amount of the paint on the base material is, for example, 0.01% of the pulverized product per 1 m ^{2 of the} base material area. -60000 μg, 0.1-5000 μg, 1-50 μg. The preferable coating amount of the paint is, for example, related to the concentration of the liquid, the coating method, etc., and thus it is difficult to define it uniquely. However, in consideration of productivity, it is preferable to apply as thin a layer as possible. . When there is too much application quantity, possibility that it will be dried with a drying furnace before a solvent volatilizes will become high, for example. As a result, the nano-ground sol particles settle and deposit in the solvent, and the solvent is dried before the void structure is formed, so that void formation may be hindered and the porosity may be greatly reduced. On the other hand, if the coating amount is too thin, there is a possibility that the risk of occurrence of coating repellency may increase due to unevenness of the base material, variation in hydrophilicity / hydrophobicity, or the like.

After the coating material is applied to the substrate, the porous body precursor (coating film) may be dried. By the drying treatment, for example, not only the solvent (the solvent contained in the paint) in the precursor of the porous body is removed, but also the sol particles are settled and deposited to form a void structure during the drying treatment. The purpose is that. The drying treatment temperature is, for example, 50 to 250 ° C., 60 to 150 ° C., 70 to 130 ° C., and the drying treatment time is, for example, 0.1 to 30 minutes, 0.2 to 10 minutes, 0 .3-3 minutes. The drying process temperature and time are preferably lower and shorter in relation to, for example, continuous productivity and high porosity. If the conditions are too strict, for example, when the substrate is a resin film, the substrate is extended in a drying furnace by being close to the glass transition temperature of the substrate, and formed immediately after coating. Defects such as cracks may occur in the void structure. On the other hand, if the conditions are too loose, for example, since the residual solvent is included at the time of leaving the drying furnace, there is a possibility that defects in appearance such as scratches will occur when rubbing with the roll in the next process. is there.

The drying treatment may be, for example, natural drying, heat drying, or vacuum drying. The drying method is not particularly limited, and for example, a general heating means can be used. Examples of the heating means include a hot air fan, a heating roll, and a far infrared heater. Above all, when it is premised on industrial continuous production, it is preferable to use heat drying. As the solvent used, a solvent having a low surface tension is preferable for the purpose of suppressing the generation of shrinkage stress accompanying the solvent volatilization during drying and the cracking phenomenon of the void layer (the silicone porous body). Examples of the solvent include, but are not limited to, lower alcohols typified by isopropyl alcohol (IPA), hexane, perfluorohexane, and the like. Further, for example, a small amount of perfluoro-based surfactant or silicon-based surfactant may be added to the IPA or the like to reduce the surface tension.

The substrate is not particularly limited, and for example, a thermoplastic resin substrate, a plastic molded with a thermosetting resin, a carbon fiber material typified by a carbon nanotube, and the like can be preferably used. It is not limited. Examples of the form of the substrate include a film and a plate. Examples of the thermoplastic resin include polyethylene terephthalate (PET), acrylic, cellulose acetate propionate (CAP), cycloolefin polymer (COP), triacetate (TAC), polyethylene naphthalate (PEN), polyethylene (PE), and polypropylene. (PP) etc. are mentioned.

In the method for producing a low refractive index film, the bonding step is a step of chemically bonding the pulverized materials included in the porous body precursor (coating film). By the bonding step, for example, the three-dimensional structure of the pulverized material in the precursor of the porous body is fixed. When fixing by conventional sintering, for example, high temperature treatment at 200 ° C. or higher induces dehydration condensation of silanol groups and formation of siloxane bonds. In the bonding step of the present invention, by reacting various additives that catalyze the above dehydration condensation reaction, for example, when the substrate is a resin film, the substrate is not damaged, and the temperature is around 100 ° C. The void structure can be continuously formed and fixed at a relatively low drying temperature and a short processing time of less than a few minutes. In the bonding step, a method for chemically bonding the pulverized materials to each other is not particularly limited, and for example, cross-linking by a catalytic reaction using the catalyst may be used. Further, for example, the pulverized product may be chemically bonded by a method such as simply heating the porous body precursor (coating film) without using the catalyst.

As described above, the low refractive index film (void layer) of the present invention can be manufactured, but the manufacturing method of the present invention is not limited to this.

The thus obtained low refractive index film (void layer) of the present invention may be laminated with another film (layer) to form a laminated structure including the porous structure. In this case, in the laminated structure, each component may be laminated via, for example, a pressure-sensitive adhesive or an adhesive.

For example, since the lamination of each component is efficient, the lamination may be performed by continuous processing using a long film (so-called Roll to Roll, etc.). May be laminated with batch processing.

Hereinafter, a method for forming the low refractive index film (void layer, typically a silicone porous body) on a substrate using the paint of the present invention will be described with reference to FIGS. explain. About FIG. 2, after forming the said low-refractive-index film (void layer), it has shown the process of bonding and winding up a protective film, but when laminating | stacking on another functional film, A technique may be used, and after coating and drying another functional film, the low-refractive-index film (void layer) on which the film has been formed can be bonded immediately before winding. The illustrated film forming method is merely an example, and the present invention is not limited thereto.

1 schematically shows an example of a process in the method of forming the low refractive index film (void layer) on the base material. In FIG. 1, the low refractive index film (void layer) is formed by applying a coating process (1) for applying the coating material 20 ″ of the present invention onto the substrate 10, and drying the coating material 20 ″. Then, a coating film forming step (drying step) (2) for forming the coating film 20 ′, which is a precursor layer of the low refractive index film (void layer), and chemical treatment (for example, A chemical treatment step (for example, a cross-linking treatment step) (3) for forming a low refractive index film (void layer) 20 by performing a cross-linking treatment). Thus, the low refractive index film | membrane (gap layer) 20 can be formed on the base material 10 as shown in the figure. The method for forming the low refractive index film (void layer) may or may not include steps other than the steps (1) to (3) as appropriate. Further, for example, the low refractive index film (void layer) is formed only by the coating process (1) and the coating film forming process (drying process) (2) without performing the chemical treatment process (for example, the crosslinking process) (3). ) 20 can also be formed.

In the coating step (1), the coating method of the paint 20 ″ is not particularly limited, and a general coating method can be adopted. Examples of the coating method include a slot die method, a reverse gravure coating method, a micro gravure method (micro gravure coating method), a dip method (dip coating method), a spin coating method, a brush coating method, a roll coating method, and flexographic printing. Method, wire bar coating method, spray coating method, extrusion coating method, curtain coating method, reverse coating method and the like. Among these, the extrusion coating method, the curtain coating method, the roll coating method, the micro gravure coating method and the like are preferable from the viewpoints of productivity, coating film smoothness, and the like. The coating amount of the paint 20 ″ is not particularly limited, and can be appropriately set so that, for example, the thickness of the low refractive index film (void layer) 20 is appropriate. The thickness of the low refractive index film (void layer) 20 is not particularly limited, and is as described above, for example.

In the drying step (2), the coating material 20 ″ is dried (that is, the dispersion medium contained in the coating material 20 ″ is removed) to form a coating film (precursor layer) 20 ′. The conditions for the drying treatment are not particularly limited and are as described above.

Further, in the chemical treatment step (3), the coating film 20 ′ containing the catalyst (for example, a photoactive catalyst or a thermally active catalyst such as KOH) added before coating is irradiated with light or heated to be applied. The pulverized material in the processed film (precursor) 20 ′ is chemically bonded (for example, crosslinked) to form the low refractive index film (void layer) 20. The light irradiation or heating conditions in the chemical treatment step (3) are not particularly limited and are as described above.

Next, FIG. 2 schematically shows an example of a slot die coating apparatus and a method for forming the low refractive index film (void layer) using the same. Although FIG. 2 is a cross-sectional view, hatching is omitted for easy viewing.

As shown in the figure, each step in the method using this apparatus is performed while the substrate 10 is conveyed in one direction by a roller. The conveyance speed is not particularly limited, and is, for example, 1 to 100 m / min, 3 to 50 m / min, or 5 to 30 m / min.

First, a coating process (1) is performed in which the coating roll 102 is coated with the coating material 20 ″ of the present invention on the coating roll 102 while the substrate 10 is fed out and conveyed from the feed roller 101, and then the oven zone. In 110, the process proceeds to the drying step (2). In the coating apparatus of FIG. 2, a preliminary drying process is performed after a coating process (1) and prior to a drying process (2). The preliminary drying step can be performed at room temperature without heating. In the drying step (2), the heating means 111 is used. As the heating means 111, as described above, a hot air fan, a heating roll, a far infrared heater, or the like can be used as appropriate. Further, for example, the drying step (2) may be divided into a plurality of steps, and the drying temperature may be increased as the subsequent drying step is performed.

After the drying step (2), the chemical treatment step (3) is performed in the chemical treatment zone 120. In the chemical treatment step (3), for example, when the dried coating film 20 ′ includes a photoactive catalyst, light irradiation is performed by lamps (light irradiation means) 121 disposed above and below the base material 10. Alternatively, for example, when the coating film 20 ′ after drying contains a thermally active catalyst, a hot air fan 121 disposed above and below the substrate 10 using a hot air fan (heating means) instead of the lamp (light irradiation device) 121. To heat the substrate 10. By this crosslinking treatment, the pulverized material in the coating film 20 ′ is chemically bonded to each other, and the low refractive index film (void layer) 20 is cured and strengthened. Then, after the chemical treatment step (3), the laminate in which the low refractive index film (void layer) 20 is formed on the substrate 10 is wound up by the winding roll 105. In FIG. 2, the low refractive index film (gap layer) 20 of the laminate is covered and protected by a protective sheet fed from the roll 106. Here, instead of the protective sheet, another layer formed of a long film may be laminated on the low refractive index film (void layer) 20.

FIG. 3 schematically shows an example of a micro gravure method (micro gravure coating method) coating apparatus and a method for forming the low refractive index film (void layer) using the same. In addition, although the figure is sectional drawing, the hatch is abbreviate | omitted for legibility.

As shown in the figure, each step in the method using this apparatus is performed while the substrate 10 is conveyed in one direction by a roller, as in FIG. The conveyance speed is not particularly limited, and is, for example, 1 to 100 m / min, 3 to 50 m / min, or 5 to 30 m / min.

First, a coating process (1) for coating the base material 10 with the coating material 20 ″ of the present invention is performed while the base material 10 is fed out and conveyed from the feed roller 201. The coating material 20 ″ is applied using a liquid reservoir 202, a doctor (doctor knife) 203, and a micro gravure 204 as shown in the figure. Specifically, the coating material 20 ″ stored in the liquid reservoir 202 is attached to the surface of the microgravure 204, and further controlled to a predetermined thickness by the doctor 203 while being applied to the surface of the substrate 10 by the microgravure 204. Apply. The microgravure 204 is merely an example, and the present invention is not limited to this, and any other coating means may be used.

Next, a drying step (2) is performed. Specifically, as shown in the drawing, the base material 10 coated with the coating material 20 ″ is transported into the oven zone 210, heated by the heating means 211 in the oven zone 210, and dried. The heating means 211 may be the same as that shown in FIG. Further, for example, by dividing the oven zone 210 into a plurality of sections, the drying step (2) may be divided into a plurality of steps, and the drying temperature may be increased as the subsequent drying step is performed. After the drying step (2), the chemical treatment step (3) is performed in the chemical treatment zone 220. In the chemical treatment step (3), for example, when the dried coating film 20 ′ includes a photoactive catalyst, light irradiation is performed by lamps (light irradiation means) 221 disposed above and below the substrate 10. Alternatively, for example, when the coating film 20 ′ after drying contains a thermally active catalyst, a hot air fan (heating means) is used instead of the lamp (light irradiation device) 221 and is arranged below the base material 10 ( The substrate 10 is heated by the heating means 221. By this crosslinking treatment, the pulverized material in the coating film 20 ′ is chemically bonded to each other, and a low refractive index film (void layer) 20 is formed.

Then, after the chemical treatment step (3), the laminated body in which the low refractive index film (void layer) 20 is formed on the substrate 10 is wound up by the winding roll 251. Thereafter, for example, another layer may be laminated on the laminate. Further, before the laminate is taken up by the take-up roll 251, for example, another layer may be laminated on the laminate.

[3. Low refractive index film (void layer)]
As described above, the low refractive index film (void layer) of the present invention has a low refractive index of 1.25 or less.

The low refractive index film (void layer) of the present invention has, for example, a scratch resistance of 60-100% by Bencot (registered trademark) indicating film strength, and the number of foldings by the MIT test indicating flexibility is as follows: It may be 100 times or more.

The material of the low refractive index film (void layer) of the present invention is not particularly limited as described above, but is, for example, a silicone porous body. Since the porous silicon body uses a pulverized product of the gel silicon compound, the three-dimensional structure of the gel silicon compound is destroyed and a new three-dimensional structure different from the gel silicon compound is formed. Has been. Thus, the silicone porous body of the present invention is a layer in which a new pore structure (new void structure) that cannot be obtained by the layer formed from the gel-like silicon compound is formed, so that the porosity is reduced. High nanoscale silicone porous bodies can be formed. Moreover, the silicone porous body of the present invention chemically bonds the pulverized products to each other while adjusting the number of siloxane bond functional groups of the gel silicon compound, for example. In addition, since a new three-dimensional structure is formed as a precursor of the silicone porous body and then chemically bonded (for example, crosslinked) in the bonding step, the silicone porous body of the present invention has a structure having voids. Sufficient strength and flexibility can be maintained. Therefore, according to this invention, a silicone porous body can be provided to various objects easily and simply. Specifically, the silicone porous body of the present invention can be used as an optical member or the like instead of an air layer, for example.

The porous silicone material of the present invention includes, for example, a pulverized product of a gel-like silicon compound as described above, and the pulverized product is chemically bonded to each other. In the silicone porous body of the present invention, the form of chemical bonding (chemical bonding) between the pulverized products is not particularly limited, and specific examples of the chemical bonding include, for example, cross-linking. The method for chemically bonding the pulverized products will be described in detail in the method for producing the silicone porous body described later.

The cross-linking is, for example, a siloxane bond. Examples of the siloxane bond include T2 bond, T3 bond, and T4 bond shown below. When the silicone porous body of the present invention has a siloxane bond, for example, it may have any one kind of bond, any two kinds of bonds, or all three kinds of bonds. Also good. Among the siloxane bonds, the greater the ratio of T2 and T3, the more flexible and the expected properties of the gel can be expected, but the film strength becomes weaker. On the other hand, when the T4 ratio in the siloxane bond is large, the film strength is easily developed, but the void size becomes small and the flexibility becomes brittle. For this reason, for example, it is preferable to change the ratio of T2, T3, and T4 according to the application.

When the silicone porous body of the present invention has the siloxane bond, the ratio of T2, T3, and T4 is, for example, when T2 is expressed as “1”, and T2: T3: T4 = 1: [1 to 100 ]: [0-50], 1: [1-80]: [1-40], 1: [5-60]: [1-30].

Moreover, in the silicone porous body of the present invention, for example, the silicon atoms contained are preferably bonded with siloxane bonds. As a specific example, the proportion of unbonded silicon atoms (that is, residual silanol) in the total silicon atoms contained in the porous silicone material is, for example, less than 50%, 30% or less, or 15% or less.

The low refractive index film (void layer, typically a silicone porous body) of the present invention has, for example, a pore structure. The pore size of the hole refers to the diameter of the major axis among the major axis diameter and minor axis diameter of the void (hole). A preferable pore size is, for example, 5 nm to 200 nm. The lower limit of the void size is, for example, 5 nm or more, 10 nm or more, 20 nm or more, and the upper limit thereof is, for example, 1000 μm or less, 500 μm or less, 100 μm or less, and the range thereof is, for example, 5 nm to 1000 μm, 10 nm. ˜500 μm, 20 nm˜100 μm. Since a preferable void size is determined depending on the use of the void structure, it is necessary to adjust the void size to a desired void size according to the purpose, for example. The void size can be evaluated by the following method, for example.

(Evaluation of gap size)
In the present invention, the void size can be quantified by a BET test method. Specifically, 0.1 g of a sample (low refractive index film of the present invention) was put into a capillary of a specific surface area measuring device (Micromeritic: ASAP2020), and then dried under reduced pressure at room temperature for 24 hours. Degas the gas in the void structure. The adsorption isotherm is drawn by adsorbing nitrogen gas to the sample, and the pore distribution is obtained. Thereby, the gap size can be evaluated.

As described above, the low refractive index film (void layer) of the present invention has, for example, a scratch resistance of 60 to 100% due to Bencot (registered trademark) indicating film strength. Since the present invention has such a film strength, for example, it is excellent in scratch resistance in various processes. The present invention has, for example, scratch resistance in a production process when handling a product film after winding the product after forming the low refractive index film (void layer). On the other hand, the low refractive index film (void layer) of the present invention uses, for example, a catalytic reaction in the heating step described later, instead of reducing the void ratio, to thereby reduce the particle size of the pulverized product of the gel silicon compound. , And the binding strength of the neck portion where the pulverized materials are bonded to each other. Thereby, the low refractive index film | membrane (gap layer) of this invention can provide a certain level of intensity | strength, for example to the void structure which is inherently weak.

The lower limit of the scratch resistance is, for example, 60% or more, 80% or more, 90% or more, and the upper limit thereof is, for example, 100% or less, 99% or less, 98% or less, and the range is For example, they are 60 to 100%, 80 to 99%, 90 to 98%.

The scratch resistance can be measured by, for example, the following method.

(Evaluation of scratch resistance)
(1) A void layer (low refractive index film of the present invention) coated and formed on an acrylic film is sampled in a circular shape having a diameter of about 15 mm.
(2) Next, with respect to the sample, silicon is identified with fluorescent X-rays (manufactured by Shimadzu Corporation: ZSX Primus II), and the Si coating amount (Si ₀ ) is measured. Next, with respect to the gap layer on the acrylic film, the gap layer is cut to 50 mm × 100 mm from the vicinity sampled, and fixed to a glass plate (thickness 3 mm). Perform dynamic tests. The sliding condition is a weight of 100 g and 10 reciprocations.
(3) The residual amount of Si (Si ₁ ) after the scratch test is measured by sampling and fluorescent X-ray measurement in the same manner as in (1) from the gap layer after sliding. The scratch resistance is defined by the Si residual ratio (%) before and after the Bencot (registered trademark) test, and is represented by the following formula.
Scratch resistance (%) = [remaining Si amount (Si ₁ ) / Si coating amount (Si ₀ )] × 100 (%)

For example, the low refractive index film (void layer) of the present invention has a folding resistance of 100 times or more by an MIT test showing flexibility. Since the present invention has such flexibility, for example, it is excellent in handleability during winding or use during production.

The lower limit of the folding endurance number is, for example, 100 times or more, 500 times or more, 1000 times or more, and the upper limit is not particularly limited, for example, 10,000 times or less, and the range is, for example, 100 10000 times, 500 times to 10000 times, 1000 times to 10000 times.

The flexibility means, for example, ease of deformation of the substance. The folding endurance by the MIT test can be measured by the following method, for example.

(Evaluation of folding test)
The void layer (low refractive index film of the present invention) is cut into a 20 mm × 80 mm strip and then attached to an MIT folding tester (manufactured by Tester Sangyo Co., Ltd .: BE-202), and a load of 1.0 N is applied. . The chuck part that embeds the gap layer uses R 2.0 mm, performs the folding endurance up to 10,000 times, and sets the number of times when the gap layer is broken as the number of folding endurances.

In the low refractive index film (void layer) of the present invention, the film density showing the porosity is not particularly limited, and the lower limit thereof is, for example, 1 g / cm ³ or more, 10 g / cm ³ or more, 15 g / cm ³ or more. The upper limit is, for example, 50 g / cm ³ or less, 40 g / cm ³ or less, 30 g / cm ³ or less, 2.1 g / cm ³ or less, and the range thereof is, for example, 5 to 50 g / cm ³ , 10 ^{^{~ 40g / cm 3, 15 ~}} 30g / cm 3, a 1 ~ 2.1g / cm ^3.

The film density can be measured by the following method, for example.

(Evaluation of film density)
After forming a void layer (low refractive index film of the present invention) on the acrylic film, the X-ray reflectivity of the total reflection region is measured using an X-ray diffractometer (RIGAKU: RINT-2000). After performing Intensity and 2θ fitting, the porosity (P%) is calculated from the total reflection critical angle of the void layer / base material. The film density can be expressed by the following formula.
Film density (%) = 100 (%)-Porosity (P%)

The low refractive index film (void layer) of the present invention may have a pore structure (porous structure) as described above, and may be, for example, an open cell structure in which the pore structure is continuous. The open cell structure means, for example, that the low refractive index film (void layer) has a three-dimensional pore structure, and the internal voids of the pore structure are continuous. I can say that. When the porous body has an open cell structure, it is possible to increase the porosity occupied in the bulk. However, when closed cells such as hollow silica are used, the open cell structure cannot be formed. In contrast, the low refractive index film (void layer, typically a silicone porous body) of the present invention has, for example, a silica sol particle (a crushed product of a gel-like silicon compound forming a sol) having a three-dimensional dendritic structure. Therefore, the dendritic particles settle and deposit in a coating film (a sol coating film containing a pulverized product of the gel-like silicon compound), so that an open cell structure can be easily formed. Is possible. Further, the low refractive index film (void layer) of the present invention more preferably forms a monolith structure in which the open cell structure has a plurality of pore distributions. The monolith structure refers to, for example, a structure in which nano-sized fine voids exist and a hierarchical structure in which the nano-voids are gathered as an open cell structure. In the case of forming the monolith structure, for example, while providing film strength with fine voids, high porosity can be imparted with coarse open-cell voids, and both film strength and high porosity can be achieved. In order to form these monolithic structures, for example, it is important to first control the pore distribution of the generated void structure in the gel-like silicon compound before pulverization into the pulverized product. For example, when the gel-like silicon compound is pulverized, the monolith structure can be formed by controlling the particle size distribution of the pulverized product to a desired size.

In the low refractive index film (gap layer) of the present invention, the tear crack generation elongation rate showing flexibility is not particularly limited, and the lower limit thereof is, for example, 0.1% or more, 0.5% or more, 1% or more. The upper limit is, for example, 3% or less. The range of the tear crack occurrence elongation is, for example, 0.1 to 3%, 0.5 to 3%, and 1 to 3%.

The tear crack elongation rate can be measured, for example, by the following method.

(Evaluation of tear crack growth rate)
After forming a void layer (low refractive index film of the present invention) on the acrylic film, sampling is performed in a strip shape of 5 mm × 140 mm. Next, the sample is chucked on a tensile tester (manufactured by Shimadzu Corporation: AG-Xplus) so that the distance between chucks is 100 mm, and then a tensile test is performed at a tensile speed of 0.1 mm / s. The sample under test is carefully observed, the test is terminated when a part of the sample has cracks, and the elongation (%) at the point of time when the cracks are taken is the tear crack generation elongation.

In the low refractive index film (void layer) of the present invention, the haze showing transparency is not particularly limited, and the lower limit thereof is, for example, 0.1% or more, 0.2% or more, 0.3% or more. The upper limit is, for example, 10% or less, 5% or less, 3% or less, and the range thereof is, for example, 0.1 to 10%, 0.2 to 5%, or 0.3 to 3%.

The haze can be measured by, for example, the following method.

(Evaluation of haze)
The void layer (low refractive index film of the present invention) is cut into a size of 50 mm × 50 mm, and set in a haze meter (manufactured by Murakami Color Research Laboratory Co., Ltd .: HM-150) to measure haze. The haze value is calculated from the following formula.
Haze (%) = [diffuse transmittance (%) / total light transmittance (%)] × 100 (%)

The refractive index is generally the ratio of the transmission speed of the wavefront of light in a vacuum to the propagation speed in the medium is called the refractive index of the medium. The refractive index of the low refractive index film (void layer) of the present invention is not particularly limited, and the upper limit thereof is, for example, 1.3 or less, less than 1.3, 1.25 or less, 1.2 or less, 1.15. The lower limit is, for example, 1.05 or more, 1.06 or more, 1.07 or more, and the range thereof is, for example, 1.05 or more and 1.3 or less, 1.05 or more and less than 1.3. 1.05 to 1.25, 1.06 to less than 1.2, and 1.07 to 1.15.

In the present invention, the refractive index means a refractive index measured at a wavelength of 550 nm unless otherwise specified. Moreover, the measuring method of a refractive index is not specifically limited, For example, it can measure with the following method.

(Evaluation of refractive index)
After forming a void layer (low refractive index film of the present invention) on an acrylic film, it is cut into a size of 50 mm × 50 mm, and this is bonded to the surface of a glass plate (thickness: 3 mm) with an adhesive layer. The back surface central part (diameter of about 20 mm) of the glass plate is painted with black magic to prepare a sample that does not reflect on the back surface of the glass plate. The sample is set in an ellipsometer (manufactured by JA Woollam Japan: VASE), the refractive index is measured under the conditions of a wavelength of 500 nm and an incident angle of 50 to 80 degrees, and the average value is taken as the refractive index.

The thickness of the low refractive index film (void layer) of the present invention is not particularly limited, and the lower limit thereof is, for example, 0.05 μm or more and 0.1 μm or more, and the upper limit thereof is, for example, 1000 μm or less, 100 μm or less. The ranges are, for example, 0.05 to 1000 μm and 0.1 to 100 μm.

The form of the low refractive index film (void layer) of the present invention is not particularly limited, and may be, for example, a film shape or a block shape.

The application of the low refractive index film (void layer) of the present invention is not particularly limited, but is as follows, for example.

[4. Application of low refractive index film (void layer)]
Since the low refractive index film (gap layer) produced using the paint of the present invention has the same function as the air layer as described above, for the object having the air layer, It can be used instead of the air layer. The low refractive index film (void layer) of the present invention can be used, for example, as an optical member. Specifically, as described above, it can be used for the laminated film and the image display device of the present invention. However, the use of the low refractive index film (void layer) of the present invention is not limited to this.

Next, examples of the present invention will be described. However, the present invention is not limited to the following examples.

[Example 1]
In the following manner, the gel for producing a low refractive index film of the present invention was produced, and a coating liquid (the coating material for producing a low refractive index film of the present invention) was obtained using the gel. Furthermore, using the coating liquid, a laminated film of the present invention in which the low refractive index film of the present invention was laminated on a substrate was obtained.

(1) 1.9 g of methyltrimethoxysilane (trade name KBM-13: manufactured by Shin-Etsu Chemical Co., Ltd.) was added to 4.4 g of DMSO and stirred. To the mixture, 1.0 g of 0.01 mol / l oxalic acid aqueous solution was added dropwise. Further, this was stirred at room temperature for 30 minutes to hydrolyze the methyltrimethoxysilane.
(2) A solution obtained by separately mixing 15.42 g of DMSO, 0.4 g of water, and 0.76 g of 28% NH ₃ aqueous solution was added to the hydrolysis solution obtained in (1) to perform gelation (gelation). Process).
(3) After the gelation step (2), the mixture was stirred at room temperature for 15 minutes and then aged at 40 ° C. for 20 hours (aging step) to obtain a gel silicon compound.
(4) The gel-like silicon compound obtained in (3) was pulverized into a dice having a long side of 15 cm or less (dividing step).
(5) After (4), IPA was added, and solvent substitution from DMSO to IPA was performed (solvent substitution step). For the solvent replacement, the step of allowing to stand at room temperature for 6 hours after IPA addition was repeated 4 times, and the IPA was replaced each time. After repeating the above four times, the amount of DMSO remaining in the gel washing solvent became 0.014 g / ml, and the solvent replacement was completed at that point. In this way, a gel for producing a low refractive index film was obtained. Furthermore, after solvent replacement, high-pressure medialess pulverization was performed in IPA to liquefy the sol particles of the gel. In this way, a coating liquid (a coating material for producing a low refractive index film) containing sol particles as the pulverized product of the gel and the IPA (coating solvent) was obtained.

Furthermore, using the coating liquid, a laminated film of the present invention in which the low refractive index film of the present invention was laminated on a substrate was obtained. That is, the coating liquid (paint for producing a low refractive index film) obtained in this example was coated on an acrylic substrate by a bar coating method, and dried at 100 ° C. for 1 min to form a coating film having a thickness of 1 μm. Formed. Thereafter, heat aging at 60 ° C. was performed for 20 hours to obtain a low refractive index film (void layer). The refractive index of this low refractive index film was 1.127.

[Example 2]
The gel and coating for producing a low refractive index film in the same manner as in Example 1 except that the solvent replacement step in (5) was performed until the residual DMSO amount in the gel washing solvent became 0.007 g / ml. A liquid (liquid for manufacturing a low refractive index film) was obtained.

Furthermore, it was carried out except that the coating solution (low refractive index film production liquid) of this example (Example 2) was used instead of the coating liquid (low refractive index film production liquid) of Example 1. In the same manner as in Example 1, a low refractive index film (void layer) was obtained. The refractive index of this low refractive index film was 1.127.

[Example 3]
The gel and coating for low refractive index film production were performed in the same manner as in Example 1 except that the solvent replacement step in (5) was performed until the amount of DMSO remaining in the gel washing solvent was 0.048 g / ml. A liquid (liquid for manufacturing a low refractive index film) was obtained.

Furthermore, it was carried out except that the coating solution (low refractive index film production liquid) of this example (Example 3) was used instead of the coating liquid (low refractive index film production liquid) of Example 1. In the same manner as in Example 1, a low refractive index film (void layer) was obtained. The refractive index of this low refractive index film was 1.137.

[Example 4]
The gel and coating for producing a low refractive index film were performed in the same manner as in Example 1 except that the solvent replacement step in (5) was performed until the residual DMSO amount in the gel washing solvent became 0.074 g / ml. A liquid (liquid for manufacturing a low refractive index film) was obtained.

Furthermore, it was carried out except that the coating liquid of this example (Example 4) (liquid for manufacturing a low refractive index film) was used in place of the coating liquid of Example 1 (liquid for manufacturing a low refractive index film). In the same manner as in Example 1, a low refractive index film (void layer) was obtained. The refractive index of this low refractive index film was 1.146.

[Example 5]
The gel and coating for producing a low refractive index film were performed in the same manner as in Example 1 except that the solvent replacement step in (5) was performed until the residual DMSO amount in the gel washing solvent became 0.139 g / ml. A liquid (liquid for manufacturing a low refractive index film) was obtained.

Furthermore, it was carried out except that the coating liquid of this example (Example 5) (liquid for manufacturing low refractive index film) was used instead of the coating liquid of Example 1 (liquid for manufacturing low refractive index film). In the same manner as in Example 1, a low refractive index film (void layer) was obtained. The refractive index of this low refractive index film was 1.227.

[Example 6]
A photobase generator and bis (trimethoxysilyl) ethane were further added to the sol particle liquid (coating liquid) obtained in (5) of Example 1, and the coating liquid (low refractive index) of this example was added. Coating for film production). More specifically, an IPA solution of 1.5% by weight of a photobase generator (WPBG266: manufactured by Wako Pure Chemical Industries, Ltd.) is prepared, 0.031 g is added to 0.75 g of the sol particle liquid, and 5 Similarly, 0.018 g of bis (trimethoxysilyl) ethane IPA solution in weight% was added to 0.75 g of the sol particle solution to obtain a coating solution of this example (paint for producing a low refractive index film).

Furthermore, instead of the coating liquid of Example 1 (paint for manufacturing a low refractive index film), the coating liquid of this example (Example 6) (paint for manufacturing a low refractive index film) was used. After drying at 1 ° C. for 1 min to form a coating film having a thickness of 1 μm, prior to heat aging, the coating film was irradiated with 300 mJ / cm ² (@ 360 nm) of UV as in Example 1. Thus, a low refractive index film (void layer) was obtained. The refractive index of this low refractive index film was 1.15.

[Example 7]
A void layer was obtained in the same manner as in Example 1 except that the solvent for gel production described in Example 1 was changed from DMSO to DMF (N, N-dimethylformamide). The refractive index of this low refractive index film was 1.120.

[Example 8]
A void layer was obtained in the same manner as in Example 1 except that the gel production solvent described in Example 1 was changed from DMSO to γ-butyrolactone. The refractive index of this low refractive index film was 1.125.

[Comparative Example 1]
The gel and coating for producing a low refractive index film were performed in the same manner as in Example 1 except that the solvent replacement step in (5) was performed until the amount of residual DMSO in the gel washing solvent became 0.55 g / ml. A liquid (liquid for manufacturing a low refractive index film) was obtained.

Further, a film (void layer) was obtained in the same manner as in Example 1 except that the coating liquid of this comparative example was used instead of the coating liquid of Example 1 (liquid for manufacturing a low refractive index film). The refractive index of this film was 1.301.

Table 1 below summarizes the amount of DMSO remaining in the gel and the refractive index of the film (void layer) in Examples 1 to 8 and Comparative Example 1.

As shown in Table 1 above, in Examples 1 to 8, the residual amount of the gel production solvent (DMSO, DMF or γ-butyrolactone) in the low refractive index film production gel was 0.5 g / ml or less. Thus, a low refractive index film having a refractive index of 1.25 or less could be obtained. On the other hand, in Comparative Example 1 where the residual amount of DMSO (gel production solvent) in the low refractive index film production gel exceeds 0.5 g / ml, a low refractive index film having a refractive index of 1.25 or less is obtained. I couldn't.

This application claims priority based on Japanese Patent Application No. 2015-187456 filed on September 24, 2015, the entire disclosure of which is incorporated herein.

As described above, the low refractive index film production gel of the present invention has a low refractive index of 1.25 or less because the residual amount of the gel production solvent in the gel is as small as 0.5 g / ml or less. Rate membranes can be produced. The low refractive index film | membrane of this invention obtained using this can show | play the function similar to an air layer, for example. For this reason, the low refractive index film | membrane of this invention can be used as an optical member etc. instead of an air layer, for example. Therefore, the production method of the present invention and the paint obtained thereby are useful, for example, in the production of the porous structure as described above.

10 Substrate 20 Low refractive index film (void layer)
20 'coating film (precursor layer)
20 '' paint 101 delivery roller 102 coating roll 110 oven zone 111 hot air (heating means)
120 Chemical treatment zone 121 Lamp (light irradiation means) or hot air device (heating means)
105 Winding Roll 106 Roll 201 Feeding Roller 202 Liquid Reservoir 203 Doctor (Doctor Knife)
204 Microgravure 210 Oven zone 211 Heating means 220 Chemical treatment zone 221 Lamp (light irradiation means) or hot air blower (heating means)

Claims

A gel for use in the production of a low refractive index film,
The residual amount of the solvent for gel production in the gel is 0.5 g / ml or less,
The gel for producing a low refractive index film, wherein the produced low refractive index film has a refractive index of 1.25 or less.
The gel for producing a low refractive index film according to claim 1, wherein the solvent for producing the gel has a boiling point of 130 ° C. or higher.
The gel for producing a low refractive index film according to claim 1, wherein the gel production solvent is a water-soluble solvent.
The gel for producing a low refractive index film according to any one of claims 1 to 3, wherein the gel is an inorganic gel.
The gel for producing a low refractive index film according to any one of claims 1 to 4, wherein the gel contains at least one element selected from the group consisting of Si, Mg, Al, Ti, Zn, and Zr.
The gel for producing a low refractive index film according to any one of claims 1 to 5, wherein the gel is a gel-like silicon compound.
The gel for producing a low refractive index film according to claim 6, wherein the gel-like silicon compound is a gel-like silicon compound obtained from a silicon compound containing at least a trifunctional or lower saturated bond functional group.
The gel for producing a low refractive index film according to any one of claims 1 to 7, for producing the low refractive index film on a substrate.
The gel for producing a low refractive index film according to claim 8, wherein the substrate is a resin film.
A gelling step of gelling the raw material of the gel in the solvent for gel production;
The manufacturing method of the gel for low refractive index film | membrane manufacture as described in any one of Claim 1 to 9 including the solvent substitution process which substitutes the solvent for gel manufacture in the said gel with another solvent.
The manufacturing method according to claim 10, wherein in the solvent replacement step, the other solvent is a solvent for manufacturing the low refractive index film.
The production method according to claim 10 or 11, wherein the other solvent is a solvent capable of dissolving the catalyst for gel production.
Furthermore, the manufacturing method as described in any one of Claims 10-12 including the gel division | segmentation process which divides | segments the said lump of gel into plurality prior to the said solvent substitution process.
The manufacturing method according to claim 13, wherein in the gel dividing step, the gel is divided into a three-dimensional structure having a long side of 15 cm or less.
Furthermore, the manufacturing method as described in any one of Claims 10-14 including the aging process which ripens the said gel in the said solvent for gel manufacture prior to the said solvent substitution process.
Furthermore, the manufacturing method of Claim 13 or 14 including the aging process which ripens the said gel in the said solvent for gel manufacture prior to the said solvent substitution process, and performing the said gel division | segmentation process after the said aging process.
The production method according to claim 15 or 16, wherein, in the aging step, the gel is aged by incubating the gel in the solvent for gel production at 30 ° C or higher.
A pulverized product of the gel for producing a low refractive index film according to any one of claims 1 to 9,
A solvent for producing a low refractive index film;
A paint for producing a low refractive index film, comprising:
The paint for producing a low refractive index film according to claim 18, wherein the solvent for producing the low refractive index film is a solvent capable of dissolving the catalyst for producing the gel.
As an optical member, a manufacturing method of an image display device including a laminated film,
The method for producing a laminated film includes a step of forming a low refractive index film on a substrate,
Forming the low refractive index film comprises:
A coating process for coating the base material with the paint for producing a low refractive index film according to claim 18 or 19,
A drying step of drying the applied coating for producing the low refractive index film;
A method for manufacturing an image display device, comprising: