JP2005352121A - Anti-reflection film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an anti-reflection film having excellent anti-reflection effect and high film strength. <P>SOLUTION: The anti-reflection film contains (1) fibrous inorganic particulates having void parts and (2) at least one kind selected from among hydrolyzable group-containing silane, its hydrolyzate and polycondensation product therefrom in a low refractive index layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an antireflection film in which a low refractive index layer is composed of fibrous inorganic fine particles having voids.

Conventionally, a technique for forming an antireflection film from hollow spherical silica particles is known (Patent Documents 1 and 2).
In order to form an antireflection film from hollow spherical silica particles, a binder for binding the particles is required. High temperature heat-resistant substrates such as glass can be heated at high temperatures, so no binder is required or the amount of binder is small. However, depending on the substrate, curing by high-temperature heating may be difficult. In this case, in order to give the antireflection film the necessary film strength and adhesion, a large amount of binder is used on the particles, and an overcoat is used. Etc. are required. However, since the refractive index of the film increases as the amount of binder or overcoat increases, there is a problem that the reflectance of the antireflection film increases.

  Patent Documents 3 and 4 disclose a method for producing inorganic porous fine particles and a method for forming a film by adding an organic binder to inorganic porous fine particles. According to this disclosed method, when an antireflection film including a low refractive index layer composed of inorganic porous fine particles was formed, a low refractive index layer having many voids and a low refractive index was obtained. The reflectance of the film was high, and the film strength was insufficient practically.

JP 2001-233611 A JP 2002-79616 A International Publication No. 02/000550 Pamphlet International Publication No. 03/055599 Pamphlet

  An object of the present invention is to provide an antireflection film having an excellent antireflection effect and high film strength.

As a result of intensive studies to solve the above problems, the present inventors have found that an antireflective film containing fibrous inorganic fine particles having voids and a specific silane compound in a low refractive index layer has a low reflectance and a high film. It has been found that it has strength, and the present invention has been completed.
That is, the present invention is as follows.

[1] In the low refractive index layer, (1) fibrous inorganic fine particles having voids, and (2) at least one selected from hydrolyzable group-containing silane, hydrolyzate and polycondensate thereof, An antireflective film comprising:
[2] The antireflective film according to [1], wherein the fibrous inorganic fine particles have a void portion having a diameter of 1 nm to 100 nm.
[3] The antireflection film as described in [1], wherein the volume of the voids of the fibrous inorganic fine particles is 5% or more of the volume of the fibrous inorganic fine particles.
[4] The antireflection film as described in [1], wherein the voids of the fibrous inorganic fine particles are through holes.
[5] The antireflection film as described in [1], wherein the voids of the fibrous inorganic fine particles are independent pores.
[6] The antireflection film as described in [1], wherein the voids of the fibrous inorganic fine particles are communication holes.
[7] The antireflection film as described in [1], wherein the average particle diameter of the fibrous inorganic fine particles measured by a dynamic light scattering method is 5 nm or more and 400 nm or less.
[8] The antireflection film as described in [1], wherein the primary particles have an average aspect ratio of 2 or more.
[9] The antireflection film as described in [1], wherein the low refractive index layer contains 5 to 95% by weight of fibrous inorganic fine particles.
[10] The antireflection film as described in [1], wherein a plurality of fibrous inorganic fine particles having voids are connected.
[11] A method for producing a composition for a low refractive index layer, comprising mixing fibrous inorganic fine particles having voids and a hydrolyzable group-containing silane, followed by hydrolysis and dehydration condensation in the presence of both.
[12] The method for producing an antireflection film according to [1], comprising a step of applying the composition for a low refractive index layer according to [11] to a substrate.

  According to the present invention, an antireflection film having an excellent antireflection effect and mechanical strength can be provided.

The present invention will be described in detail below.
In the present specification, the “low refractive index layer” refers to one layer provided to exhibit an antireflection effect. When the low refractive index layer is a single layer in which a plurality of layers are stacked on the substrate, the low refractive index layer has a lower refractive index than the lower layer, and when the low refractive index layer exists as a single layer on the substrate, Lower refractive index.
In this specification, the “antireflection film” refers to a single layer or a laminate containing at least one low refractive index layer.
The low refractive index layer contains fibrous inorganic fine particles having voids, and at least one selected from hydrolyzable group-containing silanes, hydrolysates thereof and polycondensates thereof.

The elements constituting the fibrous inorganic fine particles include silicon, alkaline earth metals such as group 2 magnesium and calcium, zinc, group 3 aluminum, gallium, rare earth, group 4 titanium, zirconium and the like, group 5 phosphorus , Vanadium, Group 7 manganese, tellurium, Group 8 iron, cobalt and the like.
The fibrous form in the fibrous inorganic particles used in the present invention means that the length of the primary particles in the extension direction is larger than the length in the direction perpendicular to the extension direction. The shape of the fibrous inorganic fine particles is represented by an aspect ratio obtained by dividing the average length in the extension direction of the primary particles by the average length in the direction perpendicular to the extension direction. Since the length of the particles in the extending direction is different for each particle, it has a certain range of distribution as a whole. The average length in the extension direction of particles refers to the average value of the distribution. The same applies to the average length in the direction perpendicular to the extension direction.

The average aspect ratio of the fibrous inorganic fine particles of the present invention is preferably 2 or more, more preferably 2.5 or more. Particles having an average aspect ratio of 2 or more are preferable because the filling of the particles becomes rough microscopically, and the refractive index of the film becomes further lower.
The length in the extension direction of the primary particles and the length in the direction perpendicular to the extension direction can be obtained by observation with an electron microscope. For the branched particles, the longest particle size of several primary particles in the extending direction is defined as the length of the particles in the extending direction.
As the shape of the fibrous inorganic fine particles, needle-like, rod-like, needle-like and stick-like shapes with sticking ends (doughnut-like), a plurality of fibrous inorganic fine particles connected to each other, chain-like, pearl like (pearl necklace-like) A shape having a shape is preferable, and a needle shape and a rod shape are more preferable.

The voids of the fibrous inorganic fine particles refer to pores present on the surface or inside of the fibrous inorganic fine particles. When an antireflection layer is formed by applying a dispersion of fibrous inorganic fine particles, the voids are usually filled with a solvent in the dispersion, and air is used in the antireflection film. Or it is filled with solvent.
The void volume of the fibrous inorganic fine particles used in the low refractive index layer is preferably 5% or more of the volume of the fibrous inorganic fine particles. The volume of the voids of the fibrous inorganic fine particles can be obtained as a pore volume by a nitrogen adsorption method. The volume of the void is preferably 0.025 mL / g or more, more preferably 0.1 mL / g or more. When the volume of the void is 0.025 mL / g or more, the volume of the void of the fibrous inorganic fine particles is 5% or more of the volume of the fibrous inorganic fine particles. The voids can also be confirmed by observation with an electron microscope.

There are various structures of the voids of the fibrous inorganic fine particles, and preferred forms used in the present invention are through-holes, independent holes and communication holes. In the through hole, the pore penetrates in the extending direction of the particle, and the opening of the pore is at both ends of the particle. Independent pores are those in which voids are present independently inside the particles. A communication hole means what the two or more independent holes exist. In the case where the voids of the fibrous inorganic fine particles are through holes, the transparency of the antireflection film is increased, which is particularly preferable. One fibrous inorganic fine particle may have a plurality of voids having different structures. It is also possible to use a plurality of fibrous inorganic fine particles having voids having different structures. ,
By changing the preparation conditions of the fibrous inorganic fine particles, the structure of the voids can be made differently or a plurality of types of voids can be provided.

The diameter of the voids of the fibrous inorganic fine particles can be obtained as the pore diameter by the nitrogen adsorption method. The diameter of the void is preferably 1 nm or more and 100 nm or less, and more preferably 2 nm or more and 50 nm or less. When the diameter of the gap is less than 1 nm, since the volume of the gap is small, the refractive index of the low refractive index layer is increased, and the reflectance of the antireflection film may be increased. When the diameter of the void is larger than 100 nm, the strength of the particles may be insufficient, and the strength of the antireflection film may not be sufficiently improved. The diameter of the void is determined by a nitrogen adsorption method or electron microscope observation.
It is preferable that the voids of the fibrous inorganic fine particles extend in the particle extension direction because the transparency of the film increases.

The low refractive index layer preferably contains 5 to 95% by weight of fibrous inorganic fine particles, more preferably 10 to 90% by weight. If the content is less than 5% by weight, the refractive index of the low refractive index layer may be large and the reflectance of the antireflection film may be high. If it is more than 95% by weight, the film strength of the antireflection film is sufficiently improved. May not.
The average particle diameter of the fibrous inorganic fine particles measured by the dynamic light scattering method is preferably 5 nm to 400 nm, more preferably 10 nm to 300 nm, and still more preferably 10 nm to 200 nm. When the fibrous inorganic fine particles are dispersed in a solvent or a binder, a more transparent film can be obtained when the particle diameter is 200 nm or less.

The fibrous inorganic fine particles having voids may or may not be substantially secondary aggregated. Secondary aggregation is a state in which primary particles are connected and / or strongly aggregated and cannot be easily dispersed in primary particles. The presence or absence of secondary aggregation can be determined by spraying a sufficiently diluted sol and observing with an electron microscope. If the number of primary particles / total number of particles is 0.5 or more, it can be said that substantially no secondary aggregation occurs.
The fibrous inorganic fine particles having voids are formed by preparing the fibrous inorganic fine particles using a surfactant or the like as a template, and then removing the template by extraction, baking, etc., or around the core fine particles. It can be formed by forming an inorganic outer shell to form a core-shell structure, and then removing the core fine particles using acid, alkali, or the like. When a void is made using a surfactant or the like as a template, a void having a uniform diameter is formed, and thus the resulting film has high transparency, which is preferable.

The hydrolyzable group-containing silane in the present invention refers to a hydrolyzable group-containing silane represented by the following general formula (1) and a hydrolyzable group-containing silane represented by the following general formula (2). The hydrolyzable group may be a group that generates a hydroxyl group by hydrolysis, and examples thereof include a halogen atom, an alkoxy group, an acyloxy group, an amino group, an enoxy group, and an oxime group.
R ¹ _n SiX _4-n (1)
(Wherein R ¹ represents hydrogen or an alkyl group having 1 to 10 carbon atoms, an alkenyl group, an alkynyl group or an aryl group. Further, a halogen group, a hydroxy group, a mercapto group, an amino group, ( It may have a functional group such as a (meth) acryloyl group, an epoxy group, etc. X represents a hydrolyzable group, and n is an integer of 0 to 3.)
X ₃ Si—R ² _n —SiX ₃ (2)
(Wherein X represents a hydrolyzable group, R ² represents an alkylene group having 1 to 6 carbon atoms or a phenylene group, and n is 0 or 1)

  Specific examples of the hydrolyzable group-containing silane include tetramethoxysilane, tetraethoxysilane, tetra (n-propoxy) silane, tetra (i-propoxy) silane, tetra (n-butoxy) silane, tetra (i- Butoxy) silane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, trimethoxysilane, triethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane , Propyltriethoxysilane, isobutyltriethoxysilane, cyclohexyltrimethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxysilane, diethoxysilane, methyldimethoxysilane, Tildiethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, bis (trimethoxysilyl) methane, bis (triethoxysilyl) methane, bis (triphenoxysilyl) methane, bis (trimethoxysilyl) ethane, bis (triethoxy Silyl) ethane, bis (triphenoxysilyl) ethane, 1,3-bis (trimethoxysilyl) propane, 1,3-bis (triethoxysilyl) propane, 1,3-bis (triphenoxysilyl) propane, 1, 4-bis (trimethoxysilyl) benzene, 1,4-bis (triethoxysilyl) benzene, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyl Triethoxysilane, -Mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltri Ethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, tetraacetoxysilane, tetrakis (trichloroacetoxy) silane, tetrakis (trifluoroacetoxy) silane, triacetoxysilane, tris (trichloroacetoxy) silane , Tris (trifluoroacetoxy) silane, methyltriacetoxysilane, methyltris (trichloroacetoxy) silane, tetrachlorosilane, tetrabromo Lan, tetrafluorosilane, trichlorosilane, tribromosilane, trifluorosilane, methyltrichlorosilane, methyltribromosilane, methyltrifluorosilane, tetrakis (methylethylketoxime) silane, tris (methylethylketoxime) silane, methyltris (methylethylketoxime) Silane, phenyltris (methylethylketoxime) silane, bis (methylethylketoxime) silane, methylbis (methylethylketoxime) silane, hexamethyldisilazane, hexamethylcyclotrisilazane, bis (dimethylamino) dimethylsilane, bis (diethylamino) dimethylsilane, Examples thereof include bis (dimethylamino) methylsilane and bis (diethylamino) methylsilane.

Further, for example, a hydrolyzable group-containing silane represented by the following general formula (3) represented by methyl silicate 51, ethyl silicate 40, ethyl silicate 48 (both manufactured by Colcoat Co., Ltd.) and the like is also preferably used. Can do.
R ³ — (O—Si (OR ³ ) ₂ ) _n —OR ³ (3)
(In the formula, ^{R 3} .n it represents an alkyl group having 1 to 6 carbon atoms is an integer of 2-8.)
The hydrolyzable group-containing silane can be used alone or as a mixture of two or more.
Among the hydrolyzable group-containing silanes, tetramethoxysilane and tetraethoxysilane are preferably used.

The hydrolyzate of a hydrolyzable group-containing silane refers to a product in which the hydrolyzable group is hydrolyzed to a silanol group.
The polycondensate of a hydrolyzable group-containing silane refers to a polycondensate produced by condensing a silanol group produced by hydrolysis of a hydrolyzable group or by polymerizing a polymerizable functional group of a hydrolyzable group-containing silane. .
As described later, these hydrolyzable group-containing silanes may be partly or wholly converted into silanol groups in the coating composition for an antireflection film by a hydrolysis reaction. A silane containing a silanol group may be used instead of a part or all of the decomposition group-containing silane. Examples of such silanes include the following.

Silanes such as silicic acid, trimethylsilanol, triphenylsilanol, dimethylsilanediol, diphenylsilanediol, or polysiloxane having a hydroxyl group at the terminal or side chain. Also, sodium orthosilicate, potassium orthosilicate, lithium orthosilicate, sodium metasilicate, potassium metasilicate, lithium metasilicate, tetramethylammonium orthosilicate, tetrapropylammonium orthosilicate, tetramethylammonium metasilicate, tetrapropylammonium metasilicate, etc. Silanes, and silanes such as activated silica obtained by contacting them with an acid or ion exchange resin.
In the present invention, the fibrous inorganic fine particles are dispersed and dissolved in the dispersion medium, and further mixed with the hydrolyzable group-containing silane and other additives to produce a coating composition for a low refractive index layer. It is preferable to prepare the fibrous inorganic fine particles as a sol from the beginning without going through a step of forming a powder by drying because the haze of the coating film is reduced.

  Hydrolyzable silanes can be used in the form of monomers, but it is preferable to partially hydrolyze and dehydrate in advance in the low refractive index layer coating composition. Partial hydrolysis and dehydration condensation reactions are carried out by reacting hydrolyzable silane with water, but as catalysts, acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, boric acid, formic acid, acetic acid, ammonia, trialkylamine Alkalis such as sodium hydroxide, potassium hydroxide, choline and tetraalkylammonium hydroxide, and tin compounds such as dibutyltin dilaurate may be used. The hydrolyzable silanes may be mixed with silica particles after partial hydrolysis / dehydration condensation in advance, or the hydrolysis / dehydration condensation reaction may be performed in the presence of silica particles.

  The hydrolyzable group-containing silane may be mixed with the above silica after previously undergoing hydrolysis / dehydration condensation reaction, but is preferably represented by the above silica and general formulas (1) to (3). It is preferable to perform the hydrolysis / dehydration condensation reaction in the presence of the hydrolyzable group-containing silane because an antireflection film having more excellent mechanical strength can be obtained. Specifically, a dispersion of silica containing fibrous inorganic fine particles and a hydrolyzable group-containing silane represented by the general formulas (1) to (3) are mixed, and water, a catalyst, or the like is mixed as necessary. An additive is added to hydrolyze / dehydrate and condense the hydrolyzable group-containing silane in the presence of silica and the hydrolyzable group-containing silane represented by the general formulas (1) to (3).

  In the present invention, the silica containing the fibrous inorganic fine particles and the hydrolyzable group-containing silane undergo hydrolysis and dehydration condensation in the coexistence, so that the surface of the silica is modified with the hydrolyzable group-containing silane and the strength of the silica is improved. In addition, since the fibrous inorganic fine particles are bonded to each other by the silanol bond derived from the hydrolyzable group-containing silane during the formation of the coating film, the adhesive strength between the fibrous inorganic fine particles can be improved. It is done. Therefore, it is possible to obtain a higher-strength antireflection film as compared with a case where a hydrolyzable group-containing silane is previously hydrolyzed and dehydrated and condensed to form a polysiloxane and silica containing fibrous inorganic fine particles is mixed. .

In the fibrous inorganic fine particles of the present invention, for the purpose other than the binder described later, for example, for the purpose of increasing dispersion stability, the reflectance and the film strength of the antireflection film are within the practical range. Compounds containing chains can be attached.
Examples of the compound containing an organic chain include a silane coupling agent. By adding a silane coupling agent, the bond and adhesion with an organic medium can be improved. In addition, particles having excellent chemical resistance such as alkali resistance can be obtained. Furthermore, even when acidified or a cationic substance or an organic solvent is added, a sol that is stable and can withstand long-term storage can be produced.

The silane coupling agent used is preferably represented by the following general formula (4).
X _n Si (OR) _4-n (4)
(In the formula, X is a hydrocarbon group having 1 to 12 carbon atoms, a quaternary ammonium group and / or a hydrocarbon group having 1 to 12 carbon atoms substituted with an amino group, or a quaternary ammonium group, and And / or a group in which a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with an amino group is connected by one or more nitrogen atoms, R is a hydrogen atom or a hydrocarbon group having 1 to 12 carbon atoms And n is an integer of 1 to 3.)
Specific examples of R include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tertiary butyl group, pentyl group, isopentyl group, neopentyl group, hexyl group, isohexyl group, cyclohexyl group, and benzyl group. An alkyl group having 1 to 3 carbon atoms is preferable, and a methyl group and an ethyl group are most preferable.

Specific examples of the hydrocarbon having 1 to 12 carbon atoms in X include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a cyclohexyl group, a benzyl group, and the like. An ethyl group, a propyl group, a butyl group, a cyclohexyl group, and a benzyl group are preferable.
Furthermore, specific examples of the hydrocarbon group having 1 to 12 carbon atoms substituted with a quaternary ammonium group and / or an amino group in X include an aminomethyl group, an aminoethyl group, an aminopropyl group, an amino group. Examples include isopropyl group, aminobutyl group, aminoisobutyl group, aminocyclohexyl group, aminobenzyl group and the like, and aminoethyl group, aminopropyl group, aminocyclohexyl group, and aminobenzyl group are preferable.

In X, a group in which a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a quaternary ammonium group and / or an amino group is linked with one or more nitrogen atoms, a carbon atom in the group The hydrocarbon group of 1 to 12 is the same as above. The number of nitrogen atoms connecting these quaternary ammonium groups and / or hydrocarbon groups optionally substituted with amino groups is preferably 1 to 4.
Specific examples of the compound represented by the general formula (4) include aminopropyltrimethoxysilane, (aminoethyl) aminopropyltrimethoxysilane, aminopropyltriethoxysilane, aminopropyldimethylethoxysilane, aminopropylmethyldiethoxy. Examples thereof include silane, aminobutyltriethoxysilane, 3- (N-styrylmethyl-2-aminoethylamino) -propyltrimethoxysilane hydrochloride, and the like.

  Such hydrolysis of the silane coupling agent is performed in the presence of water, an organic solvent and a catalyst. Examples of the organic solvent include alcohols, ketones, ethers, esters and the like, more specifically, alcohols such as methanol, ethanol, propanol and butanol, ketones such as methyl ethyl ketone and methyl isobutyl ketone, Glycol ethers such as methyl cellosolve, ethyl cellosolve and propylene glycol monopropyl ether, glycols such as ethylene glycol, propylene glycol and hexylene glycol, and esters such as methyl acetate, ethyl acetate, methyl lactate and ethyl lactate are used.

The addition amount of the silane coupling agent is preferably 0.1 to 10%, more preferably 0.3, as the weight ratio of nitrogen atoms (hereinafter referred to as content) in the dry weight of the fibrous inorganic fine particles. ~ 6%. If the content is too low, the effects of the present invention may not be sufficiently exhibited. If the content exceeds 10%, workability and other industrialization may be insufficient.
As the catalyst, inorganic acids such as hydrochloric acid, nitric acid and sulfuric acid, organic acids such as acetic acid, oxalic acid and toluenesulfonic acid, and basic compounds such as ammonia, amines and alkali metal hydroxides are used.
The amount of water necessary for hydrolysis of the silane coupling agent is preferably 0.5 to 50 mol, more preferably 1 to 25 mol, per 1 mol of Si-OR groups constituting the silane coupling agent. The catalyst is preferably 0.01 to 1 mol, more preferably 0.05 to 0.8 mol, per mol of the silane coupling agent.

Hydrolysis of the silane coupling agent is usually carried out under normal pressure at a temperature not higher than the boiling point of the solvent used, preferably at a temperature lower by about 5 to 10 ° C. than the boiling point. However, when using a heat and pressure resistant vessel such as an autoclave. Can also be carried out at a temperature higher than this temperature.
Hydrous metal oxides such as hydrous aluminum oxide, hydrous zirconium oxide and hydrous tin oxide, and basic metal chlorides such as basic aluminum chloride can be added to the fibrous inorganic fine particles of the present invention. By adding the above compound, it is possible to produce a sol that is stable and can withstand long-term storage even when acidified, a cationic substance or an organic solvent is added, or concentrated. The weight ratio of the compound to the fibrous inorganic fine particles (the compound / fibrous inorganic fine particles) is preferably in the range of 1/99 to 50/50, more preferably in the range of 5/95 to 30/70. is there.

The zeta potential of the fibrous inorganic fine particles is preferably +10 mV or more or −10 mV or less. When the zeta potential of the particles is out of the above range, the electrical repulsion between the particles becomes small, so that the dispersibility may be reduced, and sedimentation or aggregation may easily occur. The zeta potential also varies with pH. Depending on the metal source and solvent, a sol that is stable even with the addition of charged additives by using surface modification with a silane coupling agent, etc., or controlling the pH, and withstands long-term storage. Can be manufactured.
By mixing the fibrous inorganic fine particles having a positive zeta potential and the fibrous inorganic fine particles having a negative zeta potential, those in which the fibrous inorganic fine particles are connected and / or branched in a bead shape can be obtained. Depending on the application, particles connected and / or branched in a beaded manner are preferable because the filling of the particles becomes microscopic and the refractive index of the film becomes low.

By adding a calcium salt, a magnesium salt, or a mixture thereof to the fibrous inorganic fine particles, the fibrous inorganic fine particles are aggregated and can be connected and / or branched in a bead shape. Particles connected and / or branched in a bead shape are coarsely filled with particles, so that the refractive index of the low refractive index becomes small, and the reflectance of the antireflection film can be lowered.
For example, when silica is selected as the metal source, the calcium salt, magnesium salt or a mixture thereof is preferably added as an aqueous solution. The amount of calcium salt, magnesium salt or mixture thereof added is preferably 1500 ppm or more, more preferably 1500 to 8500 ppm in terms of a weight ratio of CaO, MgO or both to SiO ₂ . This addition is preferably performed with stirring, and the mixing temperature and time are not limited, but are preferably 2 to 50 ° C. and 5 to 30 minutes.

Examples of added calcium salts and magnesium salts include calcium or magnesium chlorides, bromides, iodides, fluorides, phosphates, nitrates, sulfates, sulfamates, formates, acetates, and other inorganic acid salts. And organic acid salts. These calcium salts and magnesium salts may be used in combination. The concentration of these salts added is not limited and is preferably 2 to 20% by weight.
When the polyvalent metal component other than calcium and magnesium is contained in the above colloidal aqueous solution of silica together with this calcium salt, magnesium salt, etc., it can be more preferably produced. Examples of the polyvalent metal other than calcium and magnesium include divalent, trivalent or tetravalent metals such as barium, zinc, titanium, strontium, iron, nickel and cobalt. As the amount of these polyvalent metal components, when the amount of added calcium salt, magnesium salt or the like is converted to the amount of CaO, MgO or the like, 10 to 80 wt. % Is preferred.

In order to avoid as much as possible that the amount of pores decreases or the pore diameter changes when the fibrous inorganic fine particles of the present invention are dried at a high temperature, sodium, potassium or a mixture thereof is contained as much as possible. It may be preferable not to do so. For example, when the fibrous inorganic fine particles are silica, the amount of sodium, potassium or a mixture thereof contained is preferably 1000 ppm or less, more preferably 200 ppm as sodium, potassium or both with respect to SiO ₂ . It is as follows. Examples of sodium and potassium contained include inorganic acids such as metals, sodium or potassium chloride, bromide, iodide, fluoride, phosphate, nitrate, sulfate, sulfamate, formate, acetate, etc. Examples include salts and organic acid salts.

In order to prevent the aggregation of particles, a stabilizer such as an alkali metal hydroxide such as NaOH, an organic base, NH ₄ OH, low molecular polyvinyl alcohol (hereinafter referred to as low molecular PVA), or a surfactant is added to the sol. It is preferably contained, more preferably an alkali metal hydroxide, NH ₄ OH or an organic base. It is preferable to add a stabilizer to the sol because the fibrous inorganic fine particles can be kept stable for a long time without precipitation or gelation. The amount of the stabilizer to be added is preferably 1 × 10 ^{−4 to} 0.15, more preferably 1 × 10 ^{−3 to} 0.10, and still more preferably as a weight ratio of the stabilizer / fibrous inorganic fine particles. It is 5 * 10 < ^-3 > -0.05. When the stabilizer is less than 1 × 10 ⁻⁴ , the charge repulsion of the fibrous inorganic fine particles becomes insufficient, and it may be difficult to maintain long-term stability. On the other hand, if the stabilizer exceeds 0.15, the amount of electrolyte more than necessary may increase and gelation may occur easily.

  The metal source used in the present invention is a metal oxide and / or a precursor thereof, and as mentioned above, as mentioned above, silicon, an alkaline earth metal such as group 2 magnesium and calcium, zinc, group 3 Aluminum, gallium, rare earth, etc., Group 4 titanium, zirconium, etc., Group 5 phosphorus, vanadium, Group 7 manganese, tellurium, etc., Group 8 iron, cobalt and the like. Examples of the precursor include inorganic salts such as nitrates and hydrochlorides of these metals, organic acid salts such as acetates and naphthenates, organic metal salts such as alkylaluminums, alkoxides, and hydroxides. It is not limited to this as long as it can be synthesized by a method. These may be used alone or in combination.

When silicon is selected as the metal, it is possible to use a precursor that repeats condensation or polymerization to finally become silica, preferably tetraethoxysilane, methyltriethoxysilane, dimethyltriethoxysilane, 1,2 An alkoxide such as bis (triethoxysilyl) ethane or activated silica can be used alone or in combination.
Activated silica is particularly preferred because it is inexpensive and highly safe. The active silica used in the present invention can be prepared by extraction from water glass with an organic solvent, or ion exchange of the water glass. For example, when water glass is prepared by contacting with an H + -type cation exchanger, it is industrially preferable to use No. 3 water glass because Na is low and inexpensive. As the cation exchanger, for example, a sulfonated polystyrene divinylbenzene-based strongly acidic exchange resin (for example, Amberlite (registered trademark) IR-120B (manufactured by Rohm & Haas)) and the like are preferable, but are not limited thereto. is not.

In preparing the active silica, an alkali aluminate can be added to the water glass. By using the obtained mixture of silica and alumina, it becomes possible to produce the mixture without precipitation even if the concentration is increased. The addition amount of the alkali aluminate is such that the Si / Al element ratio of the mixture of silica and alumina is preferably 200 to 1500, more preferably 300 to 1000. If the Si / Al element ratio exceeds 1500, precipitation tends to occur when the concentration is increased. When the Si / Al element ratio is less than 200, pores may not be formed when the template is removed.
Examples of the alkali aluminate to be used include sodium aluminate, potassium aluminate, lithium aluminate, primary ammonium aluminate, guanidine aluminate and the like, and sodium aluminate is preferable. The Na / Al element ratio in sodium aluminate is preferably 1.0 to 3.0.

As the core fine particles used for forming the voids in the present invention, porous composite oxide fine particles comprising silica and an inorganic oxide other than silica are used. Examples of the inorganic oxide include Al ₂ O ₃ , B ₂ O ₃ , TiO ₂ , ZrO ₂ , SnO ₂ , Ce ₂ O ₃ , P ₂ O ₅ , Sb ₂ O ₃ , MoO ₃ , ZnO ₂ and WO ₃ . 1 type or 2 or more types can be mentioned. Examples of the two or more inorganic oxides include TiO ₂ —Al ₂ O ₃ and TiO ₂ —ZrO ₂ . These particles may have various shapes such as a spherical shape, a rod shape, and a needle shape, but are preferably a rod shape and a needle shape.
Templates used in the present invention include quaternary ammonium-based cationic, anionic, nonionic, amphoteric surfactants, amines such as dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, and amine oxides. Neutral template etc. can be used, but preferably a triblock system such as Adeka (registered trademark) Pluronic L, P, F, R series (Asahi Denka) or Adeka (registered trademark) PEG series (Asahi Denka) Nonionic surfactants such as polyethylene glycol and ethylenediamine base type such as Adeka (registered trademark) Pronic TR series (Asahi Denka) can be used.

The nonionic _{surfactant, RO (C 2 H 4 O} ) a - (C 3 H 6 O) b - (C 2 H 4 O) c R ( where, a, c are the 10 to 110, b 30 to 70, and R represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms). A triblock nonionic surfactant made of ethylene oxide or propylene oxide can be used. In particular, the structural formula _{HO (C 2 H 4 O)} a - (C 3 H 6 O) b - (C 2 H 4 O) c H ( where, a, c are the 10 to 110, b is 30 to 70 And those represented by the structural formula R (OCH ₂ CH ₂ ) _n OH (wherein R represents an alkyl group having 12 to 20 carbon atoms, and n represents 2 to 30). Specifically, Asahi Denka Ltd. Adeka (R) Pluronic _{P103 (HO (C 2 H 4} O) 17 - (C 3 H 6 O) 60 - (C 2 H 4 O) 17 H), P123 (HO ( _{C 2 H 4 O) 20 -} (C 3 H 6 O) 70 - (C 2 H 4 O) 20 H), P85 , etc. and polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether or the like Can be mentioned.

In order to change the pore diameter, as an organic auxiliary, an aromatic hydrocarbon having 6 to 20 carbon atoms, an alicyclic hydrocarbon having 5 to 20 carbon atoms, an aliphatic hydrocarbon having 3 to 16 carbon atoms and amines thereof In addition, halogen substituents such as toluene, trimethylbenzene, triisopropylbenzene and the like can be added.
Below, the manufacturing method of fibrous inorganic fine particles is demonstrated.
The reaction between the metal source and the template can be carried out, for example, by stirring and mixing a metal source dissolved or dispersed in a solvent and a template dissolved or dispersed in a solvent, but is not limited to this. Absent. As the solvent, either water or a mixed solvent of water and an organic solvent may be used, but alcohols are preferable as the organic solvent. As alcohols, lower alcohols such as ethanol and methanol are preferred.

The composition used for these reactions varies depending on the template, the metal source, and the solvent, but it is necessary to select a range in which aggregation, precipitation, etc. occur and the particle size does not increase. In order to prevent aggregation and precipitation of particles, an alkali such as NaOH or a stabilizer such as low molecular weight PVA may be added. As long as it does not cause aggregation or precipitation, a pH adjuster, metal sequestering agent, antifungal agent, surface tension adjusting agent, wetting agent, and rust inhibitor may be added to the solvent.
For example, when using active silica as a metal source, Adeka (registered trademark) Pluronic P123 as a template, and water as a solvent, the following composition can be used. The weight ratio of P123 / SiO ₂ is preferably 0.01 to 30, more preferably 0.1 to 5. The weight ratio of organic assistant / P123 is preferably 0.02 to 100, more preferably 0.05 to 35. The weight ratio of water / P123 during the reaction is preferably in the range of 10 to 1000, more preferably 20 to 500. As a stabilizer, NaOH may be added in a range of 1 × 10 ^{−4 to} 0.15 as a weight ratio of NaOH / SiO ₂ . The same composition can also be used when using ADEKA (registered trademark) Pluronic P103.

The mixing of the metal source, the template and the solvent is preferably carried out with stirring at 0 to 80 ° C, more preferably 0 to 40 ° C.
The addition time means the time required from the start to the end of the addition of the metal source to the template solution or the addition of the template solution to the metal source. The addition time is preferably 3 minutes or more, more preferably 5 minutes or more. When the addition time is less than 3 minutes, the average aspect ratio of the primary particles becomes less than 2, and when used as an ink absorption layer of an ink jet recording medium, the ink absorption amount may decrease.
The addition time can be controlled by the addition rate of the metal source or template solution. It is preferable that the addition rate is substantially constant because the reproducibility of the average aspect ratio and average particle diameter of the primary particles is good, but it is not always necessary to be constant.

Although the reaction proceeds easily even at room temperature, it can be carried out under heating up to 100 ° C. if necessary. The reaction time is 0.5 to 100 hours, preferably 3 to 50 hours. The pH during the reaction is preferably in the range of 3 to 12, more preferably 6 to 11, and further preferably 7 to 10. For example, when silicon is selected as the metal, the reaction time may be shortened by adjusting the pH to 7 to 10. In order to control the pH, an alkali such as NaOH or ammonia or an acid such as hydrochloric acid, acetic acid or sulfuric acid may be added.
When producing a sol of fibrous inorganic fine particles, an alkali aluminate can be added, but the timing may be either before or after formation of the composite or after removal of the template. When the composite contains silicon, it is possible to produce a sol that is stable and can withstand long-term storage even when acidified or a cationic substance is added by adding alkali aluminate.

Examples of the alkali aluminate to be used include sodium aluminate, potassium aluminate, lithium aluminate, primary ammonium aluminate, guanidine aluminate and the like, and sodium aluminate is preferable. The Na / Al element ratio in sodium aluminate is preferably 1.0 to 3.0.
Next, a template removal method will be described. For example, the obtained composite is separated by filtration, washed with water, dried, and then the contained template is removed by contact with a supercritical fluid or a solvent such as alcohol, or by firing. Thus, fibrous inorganic fine particles may be obtained. The baking temperature is not less than the temperature at which the template disappears, and generally not less than 500 ° C. The firing time is appropriately set in relation to the temperature, but is about 30 minutes to 6 hours. As other removal methods, a method of stirring and mixing the solvent and the composite, a method of packing the composite into a column or the like and circulating the solvent can be used.

By adding a solvent such as alcohol to the obtained reaction solution and removing the template from the composite, fibrous inorganic fine particles are obtained. At this time, it is preferable to use an ultrafiltration device because the fibrous inorganic fine particles can be handled as a sol. The ultrafiltration may be performed either under pressure or under reduced pressure in addition to atmospheric pressure.
As the material of the membrane for ultrafiltration, polysulfone, polyetherketone, polyacrylonitrile (PAN), polyolefin, cellulose, etc. can be used, and the shape is hollow fiber type, flat membrane type, spiral type, tube type Any of these may be used. The material of the ultrafiltration membrane is preferably a hydrophilic membrane such as a PAN membrane, a cellulose membrane, or a charged membrane.

Charged membranes include positively charged membranes and negatively charged membranes. Examples of positively charged membranes include organic polymers such as polysulfone, polyethersulfone, polyamide, and polyolefin, and membranes in which positively charged groups such as quaternary ammonium bases are introduced into inorganic substances. Examples of negatively charged membranes include organic polymers. And a membrane in which a negatively charged group such as a carboxyl group or a sulfonic acid group is introduced into an inorganic substance.
When performing ultrafiltration, an alkali such as NaOH or a stabilizer such as low molecular weight PVA may be added to prevent particle aggregation, such as a sodium salt such as Na ₂ SO ₃ or an ammonium salt such as NH ₃ HCO _3. A viscosity modifier may be added. The solvent used for the removal may be any solvent that dissolves the template, and may be water that is easy to handle or an organic solvent that has a high dissolving power for the template.

The pH of the sol when removing the template is preferably in the range of 7 to 12, more preferably 8 to 11. In order to control pH, an alkali such as NaOH or ammonia or an acid such as hydrochloric acid, acetic acid or sulfuric acid may be added. If the pH is too high, the structure of the fibrous inorganic fine particles may be changed, and if the pH is too low, aggregation may occur.
The removal is preferably cooled to a temperature not higher than the micelle formation temperature of the template. By cooling below the micelle formation temperature, the template is dissociated and easily passes through the filtration membrane. The micelle formation temperature here means a temperature at which the template starts to form micelles in the solution when the temperature is increased at an arbitrary concentration. The actual temperature varies depending on the solvent and template used, but is preferably 60 ° C. or lower, more preferably 0 to 20 ° C. If the temperature is too low, the solvent tends to freeze.

When the fibrous inorganic fine particles are a metal oxide, when the above-mentioned silane coupling agent is added to the obtained reaction solution, the surface hydroxyl group and the silane coupling agent react to release the template from the composite. If the pH is adjusted to near the isoelectric point (the absolute value of the difference from the isoelectric point is within 1.5), the electrical repulsion between the particles is reduced and the fibrous inorganic fine particles are aggregated and centrifuged or filtered. The template can be easily removed by, for example. When the pH is adjusted to a value far from the isoelectric point after removing the template, fibrous inorganic fine particles having an average particle diameter of 10 to 400 nm that are not substantially secondary aggregated are obtained.
As a method of concentrating the sol, for example, when the viscosity of the sol is high, distillation is more efficient and preferable than using ultrafiltration. Distillation may be performed by any method as long as it does not precipitate or gelate, but vacuum distillation is preferred from the viewpoint of sol stability and distillation efficiency. As a range of the heating temperature when performing distillation, 20-100 degreeC is preferable and 20-45 degreeC is more preferable.

  As a method of concentration, if a method of newly adding a porous material sol corresponding to the evaporated solvent and concentrating while always maintaining the liquid level constant, the drying of the sol near the liquid level can be suppressed. preferable. For example, a rotary filter, a rotary evaporator, a thin film evaporator or the like can be used. Concentration by distillation may be performed alone or in combination with ultrafiltration. When used together with ultrafiltration, it may be carried out before and / or after ultrafiltration, but it is preferred to carry out after ultrafiltration because of the advantage that less solvent is evaporated. Before the distillation, it is preferable to add a stabilizer or treat the fibrous inorganic fine particles with a silane coupling agent or the like in order to make precipitation or gelation difficult.

Next, the low refractive index layer of the present invention will be described.
The low refractive index layer of the present invention includes fibrous inorganic fine particles having at least voids, so that a gap is formed between the fibrous inorganic fine particles and adjacent fibrous inorganic fine particles. Have. Compared to the case where only monospherical silica is used, the total volume of the gaps contained in the low refractive index layer can be made larger, and therefore, it has a very low refractive index of 1.10 or more and less than 1.30. A refractive index layer can be formed.
The refractive index of the low refractive index layer of the present invention is preferably from 1.22 to less than 1.30, more preferably from 1.22 to less than 1.28. When a transparent plastic substrate having a refractive index of 1.49 to 1.67, which is widely used as an optical base material, is used, if the refractive index is as large as 1.30 or more, the reflectance is not sufficiently reduced. Moreover, even if it is smaller than 1.22, the reflectance is not sufficiently reduced, and the density is too low, so that the mechanical strength of the film may be insufficient.

  Transparent plastic substrates include, for example, cellulose acetate films such as triacetyl cellulose and cellulose acetate propionate, stretched polyethylene terephthalate, polyester films such as polyethylene naphthalate, polycarbonate films, norbornene films, polyarylate films, and the like. Examples thereof include a polysulfone film, a cellulose triacetate film, a cellulose acetate propionate film, a polycarbonate film, a stretched polyethylene terephthalate film, a sheet-like or plate-like polyalkyl methacrylate, polyalkyl acrylate, and polycarbonate.

The thickness of the low refractive index layer is usually 50 to 1000 nm, preferably 50 to 500 nm, more preferably 60 to 200 nm. If the thickness is too thin or too thick, the antireflection effect in the visible light region tends to decrease.
The inorganic fine particles contained in the low refractive index layer of the present invention may be only the above-mentioned fibrous inorganic fine particles, but for the purpose of adjusting the refractive index, controlling the surface shape, etc., inorganic fine particles other than the fibrous inorganic fine particles May be included. The inorganic fine particles are preferably silica. Specific examples include monospherical silica and / or non-spherical silica having a scale-like shape.

When the low refractive index layer of the present invention contains inorganic fine particles other than the fibrous inorganic fine particles, the number of metal atoms constituting the fibrous inorganic fine particles is preferably 15 with respect to the total number of metal atoms in the low refractive index layer. 0.0% or more, more preferably 15.0% to 99.9%, further preferably 25.0% to 99.5%, and most preferably 30.0% to 99.0%. When the number of metal atoms constituting the fibrous inorganic fine particles is less than 15.0%, the refractive index of the low refractive index layer may not be sufficiently lowered.
The above fibrous inorganic fine particles and inorganic fine particles can form a porous low-refractive index layer by bonding and crosslinking the fine particles themselves. However, in order to increase the strength of adhesion and crosslinking, hydrolysis is required. The surface of the fine particles is preferably modified in advance using a group-containing silane. The amount of the hydrolyzable group-containing silane is preferably 0.005 to 10 by molar ratio with respect to the total number of metal atoms contained in the fibrous inorganic fine particles. The hydrolyzable group-containing silane used is as described above.

It is preferable that an alkaline earth metal salt is contained in the low refractive index layer since the strength of the antireflection film can be further increased. The amount of the alkaline earth metal salt is preferably 0.001 to 0.1 in terms of a molar ratio with respect to the total number of silicon atoms contained in the silica. The alkaline earth metal salt used will be described later.
In addition to the hydrolyzable group-containing silane, the low refractive index layer may contain an organic polymer, a polymerizable monomer and / or a polycondensate thereof, and a curable resin as a binder.
Examples of organic polymers include polyethers such as polyethylene glycol, polypropylene glycol, and polytetramethylene glycol, amides such as polyacrylamide derivatives, polymethacrylamide derivatives, poly (N-vinylpyrrolidone), and poly (N-acylethyleneimine). , Polyvinyl alcohol, polyvinyl acetate, polyacrylic acid derivatives, polymethacrylic acid derivatives, esters such as polycaprolactone, polyimides, polyurethanes, polyureas, polycarbonates and the like. The organic polymer may have a polymerizable functional group at the terminal or main chain.

  Examples of the polymerizable monomer include alkyl (meth) acrylate, alkylene bis (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, and dipentaerythritol penta (meth). ) Acrylate, dipentaerythritol hexa (meth) acrylate, alkylene bisglycidyl ether, trimethylolpropane triglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether, vinylcyclohexene diepoxide and the like. Here, (meth) acrylate refers to both acrylate and methacrylate.

Examples of curable resins include (meth) acrylic UV curable resins, moisture curable silicone resins, thermosetting silicone resins, epoxy resins, phenoxy resins, novolac resins, silicone acrylate resins, melamine resins, phenol resins, and unsaturated polyesters. Examples thereof include resins, polyimide resins, urethane resins, urea resins, and the like.
When these binders have a polymerizable functional group, at least one of the hydrolyzable group-containing silanes contained in the low refractive index layer has a polymerizable functional group that can be polymerized with the polymerizable functional group of the binder. Is preferred.
Next, the coating composition for producing the low refractive index layer of the present invention will be described.

The coating composition of the present invention comprises a dispersion containing fibrous inorganic fine particles. The coating composition may contain inorganic fine particles other than the fibrous inorganic fine particles.
When the coating composition of the present invention is applied on a substrate and dried / cured, the fine particles contained in the composition form a porous low refractive index layer by bonding and crosslinking the fine particles themselves. Can do. However, in order to further increase the strength of adhesion / crosslinking, it is preferable that the coating composition contains a hydrolyzable group-containing silane.
The hydrolyzable group-containing silane is preferably in the range of 0.005 to 10, more preferably 0.01 to 5, in terms of molar ratio to all metal atoms contained in the fibrous inorganic fine particles. When the ratio of the hydrolyzable group-containing silane is less than 0.005, the effect of the hydrolyzable group-containing silane is not sufficiently exhibited, and when it is more than 10, the condensate derived from the hydrolyzable group-containing silane fills the gap between the fine particles. The refractive index may be 1.30 or more.

The coating composition of the present invention preferably contains water. The water content preferably exceeds 1.5 parts by weight with respect to 1 part by weight of the fibrous inorganic fine particles. When the water content is 1.5 parts by weight or less, in order to improve the adhesive strength between the fine particles, a heat treatment at 150 ° C. or higher may be required to obtain a high-strength antireflection film.
The coating composition of the present invention preferably contains a catalyst for the purpose of promoting the hydrolysis / dehydration condensation reaction of the hydrolyzable group-containing silane. Examples of the catalyst include an acidic catalyst, an alkaline catalyst, and an organic tin compound. In particular, an acidic catalyst is preferable, and examples thereof include mineral acids such as nitric acid and hydrochloric acid, and organic acids such as oxalic acid and acetic acid.

The amount of the catalyst is preferably a concentration of 0.0008 to 1 mol / L in the coating composition. When the amount of the catalyst is less than 0.0008 mol / L, the hydrolysis / dehydration condensation reaction of the hydrolyzable group-containing silane does not proceed sufficiently, and it may be difficult to obtain an antireflection film having sufficient strength. Conversely, if it exceeds 1 mol / L, the stability of the coating composition may be reduced.
It is preferable that the coating composition of the present invention contains an alkaline earth metal salt because the coating performance on various substrates can be improved and the strength of the antireflection film can be further increased. As the alkaline earth metal salt, for example, chlorides such as magnesium, calcium, strontium and barium, inorganic acid salts such as nitrates, sulfates, formates and acetates, and organic acid salts are preferable. Of these, inorganic salts and organic acid salts of magnesium and calcium are particularly preferable. The alkaline earth metal salts can be used alone or as a mixture of two or more.

The alkaline earth metal salt is preferably in a range of 0.001 to 0.1, more preferably 0.005 to 0.05, in terms of a molar ratio with respect to silicon atoms contained in the fibrous inorganic fine particles. .
The higher the reaction temperature for hydrolyzing / dehydrating condensation of hydrolyzable group-containing silanes, the faster the reaction, which is preferable in terms of productivity.However, if the reaction is too early, dehydration condensation proceeds too much and the viscosity of the coating composition increases. It becomes impossible to apply on the substrate in the application process. Usually, the temperature at which the viscosity of the coating composition can be easily controlled, specifically, preferably 20 to 100 ° C, more preferably 20 to 60 ° C, and still more preferably 20 to 40 ° C. When the hydrolysis / dehydration condensation is performed at the above temperature, the time required is at least 1 hour at 20 ° C., and at least 20 minutes at 60 ° C.

When performing the hydrolysis / dehydration condensation reaction, it is preferable that the catalyst and water further coexist. The kind of catalyst used and the amount of catalyst and water are as described above.
The coating composition may contain an organic polymer, a polymerizable monomer, and a curable resin.
When a component having a polymerizable functional group is contained in the coating composition, it is effective to add a polymerization initiator as an additive. As the polymerization initiator, a known one such as a thermal radical generator, a photo radical generator, a thermal acid generator, a photo acid generator or the like is selected in accordance with the reaction form of the above polymerizable functional group or polymerizable monomer. Can do.
Specific examples of the heat / photo radical generator include Irgacure (registered trademark) and Darocur (registered trademark) acetophenone-based, benzophenone-based, phosphine oxide-based, and titanocene-based commercially available from Ciba Specialty Chemicals Co., Ltd. Each polymerization initiator, a thioxanthone polymerization initiator, a diazo polymerization initiator, an o-acyloxime polymerization initiator, and the like can be mentioned. Among these, polymerization initiators having an amino group and / or a morpholino group in the molecule such as Irgacure (registered trademark) 907, Irgacure (registered trademark) 369, and Irgacure (registered trademark) 379 are particularly preferable.

Specific examples of the heat / photoacid generator include Sun Aid (trademark) SI series marketed by Sanshin Chemical Industry Co., Ltd., WPI series, WPAG series, Sigma Aldrich Japan marketed by Wako Pure Chemical Industries, Ltd. Examples thereof include sulfonium-based, iodonium-based, and diazomethane-based polymerization initiators represented by the PAGs series marketed by the corporation.
The low refractive index layer in the present invention can be obtained by coating the substrate with the fine particles, binder, additive and the like dispersed in a dispersion medium. The dispersion medium is not limited as long as the fine particles and the binder or additive are substantially stably dispersed.

  Specific examples of the dispersion medium include water, monohydric alcohols having 1 to 6 carbon atoms, dihydric alcohols having 1 to 6 carbon atoms, alcohols such as glycerin, formamide, N-methylformamide, N-ethylformamide, N, N-dimethylformamide, N, N-diethylformamide, N-methylacetamide, N-ethylacetamide, N, N-dimethylacetamide, N, N-diethylacetamide, amides such as N-methylpyrrolidone, tetrahydrofuran, diethyl ether, Ethers such as di (n-propyl) ether, diisopropyl ether, diglyme, 1,4-dioxane, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol dimethyl ether, ethylene glycol monomethyl ether, propylene Pyrene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether and other alkanol ethers, ethyl formate, methyl acetate, Ethyl acetate, ethyl lactate, ethylene glycol monomethyl ether acetate, ethylene glycol diacetate, propylene glycol monomethyl ether acetate, esters such as diethyl carbonate, ethylene carbonate, propylene carbonate, γ-butyrolactone, ethyl acetoacetate, acetone, methyl ethyl ketone, methyl propyl Ketone, methyl (n-butyl) ketone, methyl isobut Preferably used are ketones such as tilketone, methyl amyl ketone, acetylacetone, cyclopentanone and cyclohexanone, nitriles such as acetonitrile, propionitrile, n-butyronitrile and isobutyronitrile, dimethyl sulfoxide, dimethyl sulfone and sulfolane. .

  More preferable dispersion media are monohydric alcohols having 1 to 6 carbon atoms, and ethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monoethyl ether, ethylene glycol monopropyl ether, propylene glycol monopropyl Ethers, alkanol ethers such as ethylene glycol monobutyl ether, propylene glycol monobutyl ether, acetone, methyl ethyl ketone, methyl propyl ketone, methyl (n-butyl) ketone, methyl isobutyl ketone, methyl amyl ketone, acetylacetone, cyclopentanone, cyclohexanone, etc. Ketones.

These dispersion media may be mixed or other arbitrary solvents or additives may be mixed as long as the object of the present invention is not impaired.
The concentration of the silica particles in the dispersion is preferably 0.01 to 10% by weight, more preferably 0.05 to 5% by weight from the viewpoint of providing good film formability. When the concentration is below the above range, it may be difficult to obtain a film having a desired thickness. On the other hand, when the above range is exceeded, the viscosity of the coating solution becomes too high and the workability of film formation tends to deteriorate.
In applying the above dispersion to a substrate, it is also effective to add a known leveling agent or a binding aid (coupling agent) in order to increase the coating performance and the adhesion to the substrate.

The low refractive index layer in the present invention does not impair the gist of the present invention with various additives such as an antistatic agent, an ultraviolet absorber, an infrared absorber, a leveling agent, a dye, a metal salt, a surfactant, and a release agent. It is also possible to make it contain in the range.
Next, a method for manufacturing a low refractive index layer, a laminate including the low refractive index layer, and an antireflection film will be described.
The method for producing the low refractive index layer of the present invention is not limited, and when coated on an optical substrate using a coating composition, the shape, content, concentration of coating solution, binder and additives of silica particles It can be produced by any method by controlling the types and their concentrations, coating methods, coating conditions, and the like.

  Application of the coating composition is a known dipping, spin coater, knife coater, bar coater, blade coater, squeeze coater, reverse roll coater, gravure roll coater, slide coater, curtain coater, spray coater, die coater, cap coater, etc. It can be implemented using a method. Of these, knife coaters, bar coaters, blade coaters, squeeze coaters, reverse roll coaters, gravure roll coaters, slide coaters, curtain coaters, spray coaters, die coaters and cap coaters that can be continuously applied are preferably used.

  The hydrolyzable group-containing silane is preferably added in advance to the dispersion containing the fine particles described above and hydrolyzed and then applied to the base material. However, the base material contains hydrolyzable group-containing silane or hydrolyzable group-containing silane in advance. A dispersion containing fine particles may be applied after applying the solution. In this case, after applying the dispersion containing fine particles, the viscosity of the hydrolyzable group-containing silane solution and the type of fine particle dispersion medium are adjusted so that the hydrolyzable group-containing silane component penetrates into part or all of the fine particle layer. The mechanical strength of the antireflection film is improved by setting the heat treatment temperature and time after coating, or by pressing. Or conversely, after applying a dispersion containing fine particles to a substrate in advance, a hydrolyzable group-containing silane or a solution containing a hydrolyzable group-containing silane may be applied. Also in this case, after applying the hydrolyzable group-containing silane, the hydrolyzable group-containing silane component is adjusted to adjust the viscosity of the hydrolyzable group-containing silane and the type of solvent so that the hydrolyzable group-containing silane component penetrates into part or all of the fine particle layer. It is preferable to set the heat treatment temperature and time after coating, or to perform pressing.

Even if the silica particle dispersion contains a hydrolyzable group-containing silane, a binder can be separately applied. For example, a (meth) acrylic UV curable resin can be further applied after applying a fine particle dispersion containing a hydrolyzable group-containing silane.
If necessary, the above alkaline earth metal salt and various additives are added to form a coating composition. These alkaline earth metal salts and additives may be added before the hydrolysis / dehydration condensation reaction, or may be added later.

  After coating the dispersion containing the fine particles and the solution containing the binder, heating is preferably performed to volatilize the dispersion medium and to condense and crosslink between the silica particles and the binder component. The heating temperature and time are determined by the heat resistance of the substrate. For example, when a glass substrate is used as the optical substrate, heating at 500 ° C. or higher can be performed. When a plastic substrate is used as the optical substrate, the heating temperature is selected from 50 ° C to 200 ° C, and the time is selected from 1 second to 1 hour, preferably in the range of 80 ° C to 150 ° C, 10 seconds to 3 minutes. . Moreover, when the said binder has radiation curability, an ultraviolet-ray, an electron beam, etc. are irradiated by a well-known method. Microwave irradiation may be performed as a heating method.

An antireflection film is formed by forming a transfer multilayer film including a low refractive index layer and an adhesive layer on a carrier film subjected to a release treatment, and transferring the transfer multilayer film to a transparent plastic substrate using the adhesive layer It is also possible to form At this time, the multi-layer film for transfer may include a layer having other functions such as a hard coat layer and an antistatic layer.
It is preferable to provide a high refractive index layer immediately below the low refractive index layer because the antireflection effect can be further enhanced. As the high refractive index layer, for example, known inorganic fine particles such as oxides or composite oxides made of metals such as titanium, zirconium, zinc, cerium, tantalum, yttrium, hafnium, aluminum, magnesium, etc. are dispersed in a binder. Is used. Of the above metal oxides, zirconium oxide having both a high refractive index and light resistance is particularly preferable.

  As the binder, those listed as binders for the low refractive index layer can be used, and among them, a functional group capable of forming a covalent bond with a polymerizable functional group and silica particles in the same molecule is preferable. These are hydrolyzable silanes (including organic polymers having polymerizable functional groups at their side chains and terminals, polymerizable monomers, and curable resins. The types and amounts of these binders are based on the desired refractive index and strength. A known material can be used in consideration of light resistance, yellowing, etc. The refractive index of the high refractive index layer is in the range of 1.4 to 2.5, and is preferably the square of the refractive index of the low refractive index layer. The thickness of the high refractive index layer is usually set to 0.01 μm to 1 μm.

Providing an antistatic layer in the antireflection film is effective because it can prevent dust from adhering to the antireflection film. As the antistatic layer, those obtained by dispersing a known antistatic agent such as a surfactant or an ionic polymer, conductive fine particles and the like in a binder are used.
As the conductive fine particles, for example, oxide or composite oxide fine particles of indium, zinc, tin, molybdenum, antimony, gallium, etc., copper, silver, nickel, low melting point alloy (solder, etc.) metal fine particles, and metal coating Known materials such as polymer fine particles, various carbon blacks, conductive polymer particles such as polypyrrole and polyaniline, metal fibers, and carbon fibers are used. Among these, ITO (tin-containing indium oxide) particles and ATO (tin-containing antimony oxide) particles are particularly preferable because they can exhibit high transparency and conductivity.

The thickness of the antistatic layer is usually set to 0.01 to 1 μm. As the binder, those listed as binders for the low refractive index layer can be used. Among them, a functional group capable of forming a covalent bond with a polymerizable functional group and silica particles is preferable in the same molecule. These are hydrolyzable silanes, organic polymers having a polymerizable functional group at the side chain or terminal, polymerizable monomers, and curable resins.
It is preferable to provide a hard coat layer under the low refractive index layer or the antistatic layer because the pencil strength and impact resistance of the antireflection film can be improved. As the hard coat layer, a commercially available silicone hard coat, (meth) acrylic hard coat, epoxy hard coat, urethane hard coat, epoxy acrylate hard coat, urethane acrylate hard coat, etc. should be used. Can do. In addition, it can be formed by applying a coating liquid containing a polyfunctional monomer and a polymerization initiator and polymerizing the polyfunctional monomer. The thickness of the hard coat layer is usually set to 0.1 μm to 10 μm.

The high refractive index layer, the antistatic layer, and the hard coat layer may combine two or all of these functions into one layer. That is, for example, a single layer containing both a material having a high refractive index and a conductive material may be provided to form a high refractive index / antistatic layer, or a conductive material may be contained in the hard coat layer to prevent charging. A technique such as a hard coat layer may be used.
A coating layer may be provided in order to impart slipperiness or antifouling property to the antireflection film surface. The coating layer is, for example, a fluorine resin, a moisture curable silicone resin, a thermosetting silicone resin, silicon dioxide, a (meth) acrylic resin, a (meth) acrylic UV curable resin, an epoxy resin, a phenoxy resin, or a novolac resin. , Silicone acrylate resin, melamine resin, phenol resin, unsaturated polyester resin, polyimide resin, urethane resin, urea resin, and the like.
The film thickness of the coating layer is usually 50 nm or less, preferably 30 nm or less, more preferably 15 nm or less, and most preferably 6 nm or less. The coating layer may be composed of a single layer or a plurality of layers. Among these, a fluororesin, a moisture curable silicone resin, and a thermosetting silicone resin are preferable in order to exhibit an antifouling effect.

  The antireflection film is formed on the optical substrate and can be used practically. Examples of the optical base material include a glass plate, a (meth) acrylic resin plate, a (meth) acrylic resin sheet, a styrene- (meth) methyl acrylate copolymer resin plate, and a styrene- (meth) methyl acrylate copolymer. Resin sheet, polyethylene film, polypropylene film, cellulose acetate film such as triacetyl cellulose, cellulose acetate propionate, stretched polyethylene terephthalate, polyester film such as polyethylene naphthalate, polycarbonate film, norbornene film, polyarylate In addition to plastic plates such as films and polysulfone films, plastic sheets, plastic films, eyesight correction members such as eyeglass lenses, goggles and contact lenses, car windows and Automotive parts such as nemeters, navigation systems, housing and building materials such as window glass, agricultural products such as light-transmitting films and sheets of vinyl houses, battery members such as solar cells and photovoltaic cells, lasers, TV CRTs, plasma display panels, Electronic devices such as notebook computers, electronic notebooks, touch panels, liquid crystal televisions, liquid crystal displays, in-vehicle televisions, liquid crystal video, projection televisions, plasma addressed liquid crystal displays, field emission displays, organic / inorganic EL displays, light-emitting diode displays, optical fibers, and optical disks Information equipment parts, lighting gloves, fluorescent lamps, mirrors, clocks and other household items, showcases, foreheads, semiconductor lithography, photocopying and other business components, liquid crystal game machines, pachinko machine glasses, game machines, etc. Preliminary / or light-transmitting optical substrate optical transparency improving is required and the like.

The present invention will be specifically described using examples and comparative examples.
・ Polyethylene terephthalate film (hereinafter referred to as PET film)
A 188 μm-thick PET film (Cosmo Shine (registered trademark) A4300, manufactured by Toyobo Co., Ltd., heat-resistant temperature of about 150 ° C., refractive index equivalent to 1.55, pencil hardness HB) with easy adhesion treatment on both sides is used.
-Measurement of absolute reflectance and refractive index Using an FE-3000 reflection spectrometer (manufactured by Otsuka Electronics Co., Ltd.), a reflection spectrum in a wavelength range of 250 to 800 nm was measured. The minimum reflectance in the wavelength range was determined as the minimum reflectance. The refractive index at 550 nm is obtained from the reflection spectrum.

-Measurement of haze It measures by the method prescribed | regulated to JISK7361-1 using Nippon Denshoku Industries Co., Ltd. turbidimeter NDH2000.
-Measurement of water contact angle It measures using the Kyowa Interface Science Co., Ltd. CA-VE type | mold automatic solid surface energy analyzer.
-Measurement of pencil hardness Pencil hardness at 1 kg load is evaluated according to the pencil hardness evaluation method specified in JISK5400 using a test pencil specified by JIS S6006.

-Measurement of pore volume, pore distribution, and specific surface area Measurement was carried out with nitrogen using an autosorb-1 manufactured by Cantachrome. The pore distribution was calculated by the BJH method. The average pore diameter is calculated from the peak value in the mesopore region of the differential pore distribution curve obtained by the BJH method. The specific surface area is calculated by the BET method.
-Measurement of average particle diameter and zeta potential by dynamic light scattering method Measured with a laser zeta electrometer ELS-800 manufactured by Otsuka Electronics.
・ Viscosity measurement Brookfield viscometer LVDVII +, spindle is a small sample dedicated No. 21 is used and measured at a temperature of 25 ° C.
-TEM photography Photographing with acceleration voltage 125kV using Hitachi H-7100.

[Example 1]
In a dispersion of 864 g of cation exchange resin (Amberlite (registered trademark) IR-120B), which was previously made into H ⁺ , in 864 g of water, No. 3 water glass (SiO ₂ = 29 wt%, Na ₂ O = 9. 5 wt%) 288 g and sodium aluminate (Al ₂ O ₃ = 54.9 wt%) 0.228 g diluted with 576 g water were added. After sufficiently stirring this, the cation exchange resin was filtered off to obtain 1728 g of an active silica aqueous solution. The SiO ₂ concentration of this aqueous active silica solution was 5.0% by weight, and the Si / Al element ratio was 450.

104 g of Pluronic P123 manufactured by Asahi Denka Co., Ltd. was dissolved in 2296 g of water, and 1600 g of the above active silica aqueous solution was added at a constant addition rate in 10 minutes while stirring in a 35 ° C. hot water bath. The pH of this mixture was 3.5. At this time, the weight ratio of water / P123 was 38.5, and the weight ratio of P123 / SiO ₂ was 1.3. The mixture was stirred at 35 ° C. for 15 minutes, then allowed to stand at 95 ° C. and reacted for 24 hours.
This solution was filtered using PAN membrane AHP-0013 (manufactured by Asahi Kasei Co., Ltd.) as an ultrafiltration membrane to remove nonionic surfactant P123, and fibrous inorganic fine particles having a SiO ₂ concentration of about 7.3 wt% were obtained. Sol (A) was obtained. The average particle diameter of the sample in the sol (A) measured by the dynamic light scattering method was 195 nm, and the converted specific surface area was 14 m ² / g. The sol was dried at 105 ° C. to obtain fibrous inorganic fine particles. This sample had an average pore diameter of 10 nm and a pore volume of 1.06 ml / g. The nitrogen adsorption specific surface area by the BET method was 590 m ² / g, and the difference from the converted specific surface area was 576 m ² / g.

This sample was diluted 100 times with pure water, and the diluted sample was dropped on a carbon support membrane-laminated mesh, air-dried, and used as a spectroscopic sample. TEM imaging was performed by the method described above. In the obtained photograph with a magnification of 100,000, rod-like particles were observed, and it was observed that the pores were through-holes extending in the particle extension direction. The length of the 100 primary particles of the rod-like particles in the extension direction and the length in the direction perpendicular to the extension direction were measured. As a result, the average length in the extension direction was 190 nm, the average length in the direction perpendicular to the extension direction was 35 nm, and the average aspect ratio was 5.4.
While stirring 1 g of the obtained sol (A), 10.68 g of ethanol was slowly added, and then 0.63 g of tetraethoxysilane and 0.35 g of 1.64% nitric acid aqueous solution were added and stirred overnight. A coating composition (B) was obtained.

A commercially available hard coat agent (trade name: UVHC8558, manufactured by GE Toshiba Silicone Co., Ltd.) was applied to one side of the PET film from a spin coater, and then an ultraviolet curing device (trade name: UVC-2519 / manufactured by Ushio Electric Co., Ltd.). 1MNSC7-MS01) was used to form a hard coating layer having a thickness of 5 μm by irradiating with ultraviolet rays (integrated light amount 620 mJ / cm ² ) at an output of 120 W, a conveyor speed of 2 m / min, and a light source distance of 10 mm, to obtain a transparent plastic substrate . The pencil hardness of this transparent plastic substrate was 3H.
Next, the coating composition (B) is coated on the transparent plastic substrate by spin coating at room temperature, followed by drying at 120 ° C. for 2 minutes in a hot air circulating drier. A laminate composed of a low-refractive index layer made of fine inorganic particles and a transparent plastic substrate was obtained. The laminate exhibited a minimum reflectance at a wavelength of 550 nm, and was 3.5% when there was no low refractive index layer, but was suppressed to 0.10%. The refractive index n of the low refractive index layer was 1.25. The pencil strength was 2H. The haze was as good as 0.8%.

[Example 2]
While stirring 1 g of the sol (A) of Example 1, ethanol 10.68 g was slowly added, and then 3-methacryloxypropyltrimethoxysilane (trade name: Silaace S710, registered trademark, manufactured by Chisso Corporation). 15 g, Irgacure 369 (registered trademark, manufactured by Ciba Specialty Chemicals Co., Ltd.) 15 mg, and 1.64% nitric acid aqueous solution 70 mg were added to obtain a coating composition (C).
Next, using the coating composition (C), coating was performed on a transparent plastic substrate in the same manner as in Example 1, followed by drying at 120 ° C. for 2 minutes in a hot air circulating dryer. Next, ultraviolet irradiation (ultraviolet irradiation integrated light quantity 360 mJ / cm ² ) was performed at an output of 160 W, a conveyor speed of 4.6 m / min, and a light source distance of 10 mm using the ultraviolet curing device of Example 1, and from the fibrous inorganic fine particles. A laminate composed of a low refractive index layer and a transparent plastic substrate was obtained. The laminate had a minimum reflectance of 0.10% at a wavelength of 550 nm. The refractive index n of the low refractive index layer was 1.25. The pencil strength was H. The haze was as good as 0.7%.

[Example 3]
While stirring 1 g of the sol (A) of Example 1, 10.68 g of ethanol was slowly added, and then 3-methacryloxypropyltrimethoxysilane ((trade name: Silaace S710, registered trademark, manufactured by Chisso Corporation). 05 g, Irgacure 369 (manufactured by Ciba Specialty Chemicals, Inc., registered trademark) 5.0 mg, acrylic ultraviolet curable resin (trademark, Sunrad RC-600, Sanyo Chemical Industries, solid content 100% by weight) 0.10 g Then, 23 mg of a 1.64% aqueous nitric acid solution was added to obtain a coating composition (D).
Next, using the coating composition (D), a laminate composed of a low refractive index layer composed of fibrous inorganic fine particles and a transparent plastic substrate was obtained in the same manner as in Example 2. The laminate had a minimum reflectance at a wavelength of 550 nm and was 0.20%. The refractive index n of the low refractive index layer was 1.27. The pencil strength was H. The haze was as good as 0.8%.

[Comparative Example 1]
To 1 g of the sol (A) obtained in Example 1, 10 g of ethanol, 0.1 g of PVA-117 (manufactured by Kuraray), and 0.2 g of PVA-R1130 (manufactured by Kuraray) were mixed to obtain a coating composition (E). Obtained. Using this coating composition, the coating was carried out on the transparent plastic substrate at room temperature by the spin coating method in the same manner as in Example 1, followed by drying for 10 minutes at room temperature. A laminate composed of a low refractive index layer and a transparent plastic substrate was obtained. The laminate had a minimum reflectance at a wavelength of 550 nm and was 0.80%. The refractive index n of the low refractive index layer was 1.10. The pencil strength was F. The haze was as good as 0.8%.

[Comparative Example 2]
In Example 1, the coating composition (A) was prepared by dispersing an aqueous dispersion of monospherical silica having an average diameter of 12 nm (trade name: Snowtex O, registered trademark, manufactured by Nissan Chemical Industries, Ltd., silica solid content concentration 20% by weight). ) It was carried out in the same manner except that it was changed to a monospherical silica water / ethanol dispersion obtained by mixing 3 g and 37 g of ethanol. The obtained laminate had a pencil hardness of 2H, a haze of 0.8%, and a wavelength that gave the minimum reflectance was located at 550 nm, but the minimum reflectance showed a high value of 0.80%. The refractive index n of the low refractive index layer was 1.35.

  The antireflection laminate of the present invention is useful as an antireflection film.

Claims (12)

  The low refractive index layer contains (1) fibrous inorganic fine particles having voids, and (2) at least one selected from hydrolyzable group-containing silane, hydrolyzate thereof and polycondensate thereof. An antireflection film characterized by.   2. The antireflection film according to claim 1, wherein the fibrous inorganic fine particles have voids having a diameter of 1 nm to 100 nm.   2. The antireflection film according to claim 1, wherein the volume of the voids of the fibrous inorganic fine particles is 5% or more of the volume of the fibrous inorganic fine particles.   The antireflection film according to claim 1, wherein the voids of the fibrous inorganic fine particles are through holes.   The antireflection film according to claim 1, wherein the voids of the fibrous inorganic fine particles are independent holes.   2. The antireflection film according to claim 1, wherein the voids of the fibrous inorganic fine particles are communication holes.   The antireflection film according to claim 1, wherein the average particle diameter of the fibrous inorganic fine particles measured by a dynamic light scattering method is 5 nm or more and 400 nm or less.   2. The antireflection film according to claim 1, wherein the average aspect ratio of the primary particles of the fibrous inorganic fine particles is 2 or more.   2. The antireflection film according to claim 1, wherein the low refractive index layer contains 5% by weight to 95% by weight of fibrous inorganic fine particles.   The antireflection film according to claim 1, wherein a plurality of fibrous inorganic fine particles having voids are connected.   A method for producing a composition for a low refractive index layer, comprising mixing fibrous inorganic fine particles having voids and a hydrolyzable group-containing silane, followed by hydrolysis and dehydration condensation in the presence of both.   The manufacturing method of the anti-reflective film of Claim 1 including the process of apply | coating the composition for low refractive index layers of Claim 11 to a base material.