JP5061967B2 - Curable composition, cured film and method for producing cured film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a curable composition that provides a cured film with a lower refractive index, good appearance, and good strength, and a method for producing a cured film. <P>SOLUTION: The curable composition containing (A) a compound having 2 or more (meth)acryloyl groups, (B) a compound that generates an active species via radiation, and (C) a compound having a structure represented by general formula (1). <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a curable composition. More specifically, the present invention relates to a curable composition that provides a cured film having a low refractive index and excellent appearance and strength.

  In various display panels such as liquid crystal display panels, cold cathode ray tube panels, plasma displays, etc., in order to prevent reflection of external light and improve image quality, it has low refractive index, scratch resistance, coatability, and durability. There is a demand for an antireflection film including a low refractive index layer made of an excellent cured film.

  The antireflection film generally has at least a high refractive index layer and a low refractive index layer as the outermost layer on a transparent substrate. Here, the greater the difference in refractive index between the high refractive index layer and the low refractive index layer, the better the antireflection performance. Therefore, it is necessary to lower the refractive index of the low refractive index layer.

  Various methods have been proposed to further reduce the refractive index of the transparent material. However, even if a fluorine-containing polymer or fine particles having a low refractive index are contained, the refractive index is different from that of the matrix material. Only intermediate values of the refractive index can be taken. Therefore, an optical material having a refractive index lower than that of the matrix material has been proposed by dispersing minute holes made of a gas such as vacuum, air, or nitrogen instead of fine particles in the matrix material (Patent Document 1). . This optical material uses a polymerization initiating member that generates nitrogen gas when irradiated with ultraviolet light or heated, a foamed member that decomposes and foams when irradiated with ultraviolet light, and the like.

Japanese Patent Laid-Open No. 06-003501

  An object of the present invention is to provide a curable composition that gives a cured film having a lower refractive index and an excellent appearance and strength, and a method for producing the cured film.

  In order to achieve the above-mentioned object, the present inventors have conducted intensive research and decomposed by acid and / or heat in the coating film to release carbon dioxide and volatile alcohol. The present inventors have found that a curable composition containing a compound that generates bubbles can provide a cured film having a low refractive index and excellent strength, thereby completing the present invention.

That is, this invention provides the following curable composition, a cured film, the manufacturing method of a cured film, and an antireflection film.
1. The following components (A) to (C):
(A) Compound having two or more (meth) acryloyl groups (B) Compound that generates active species upon irradiation with radiation (C) The following general formula (1)
(Wherein R ^{1 to} R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, R ⁵ and R ⁶ are a hydrogen atom or a methyl group, and R ⁷ is an alkylidene having 1 to 6 carbon atoms or A curable composition containing a compound having a structure represented by the following formula: alkylene having 2 to 6 carbon atoms and n being an integer of 1 to 6.
2. Furthermore, (D-1) The curable composition of said 1 containing a photo-acid generator.
3. Furthermore, (D-2) The curable composition of said 1 or 2 containing a thermal acid generator.
4). Curing in any one of said 1-3 whose said component (C) is either one or both of the compound shown by the following formula (1-1), and the compound shown by the following formula (1-2). Sex composition.
(In Formula (1-2), m is an integer of 1-100.)
5. Furthermore, (E) The curable composition in any one of said 1-4 containing the silica particle which has a number average particle diameter in the range of 1-100 nm.
6). The cured film formed by hardening the curable composition in any one of said 1-5.
7). The manufacturing method of the cured film including the process of apply | coating the curable composition in any one of said 1 and 3-5 to a base material, photocuring, and the process of heating.
8). The manufacturing method of the cured film including the process of apply | coating the curable composition in any one of said 2-5 to a base material, and making it photocure.
9. 8. The method for producing a cured film as described in 7 above, which comprises a heating step after the photocuring step.
10. 6. An antireflection film comprising the cured film as described in 5 above as a low refractive index layer.

According to the present invention, it is possible to provide a curable composition that gives a cured film having a lower refractive index and an excellent appearance and strength.
ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the cured film which is lower in refractive index and excellent in the external appearance and intensity | strength can be provided using the curable composition of this invention.

Hereinafter, the present invention will be specifically described.
I. Curable composition The curable composition of the present invention (hereinafter referred to as the composition of the present invention) may contain the following components (A) to (F). Among the following components, components (A) to (C) are essential components, and components (D) to (H) are components that can be contained as necessary.
(A) Compound having two or more (meth) acryloyl groups (B) Compound that generates active species upon irradiation with radiation (C) The following general formula (1)
(Wherein R ^{1 to} R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, R ⁵ and R ⁶ are a hydrogen atom or a methyl group, and R ⁷ is an alkylidene having 1 to 6 carbon atoms or A compound having a structure represented by the formula (D-1) a photoacid generator (D-2) a thermal acid generator (E), which is an alkylene having 2 to 6 carbon atoms and n is an integer of 1 to 6. Silica particles having a number average particle diameter in the range of 1 to 100 nm (F) Polydimethylsiloxane compound (G) Organic solvent (H) and other additives Hereinafter, each component will be described.

(A) Compound having two or more (meth) acryloyl groups Compounds having two or more (meth) acryloyl groups (hereinafter sometimes referred to as compound (A)) form a matrix of the resulting cured film. It is an ingredient. The compound (A) is not particularly limited as long as it has two or more (meth) acryloyl groups, and may be a polyfunctional (meth) acryl monomer, or two or more (meth) acryloyl groups. In addition, a monomer or a polymer containing a fluorine atom or a silicon atom may be used.

Examples of the polyfunctional (meth) acrylic monomer include ethylene glycol di (meth) acrylate, dicyclopentenyl di (meth) acrylate, triethylene glycol diacrylate, tetraethylene glycol di (meth) acrylate, and bis ((meth) acryloyl). Oxymethyl) tricyclo [5.2.1.0 ^2,6 ] decane (also referred to as “tricyclodecanediyldimethylene di (meth) acrylate”), tris (2-hydroxyethyl) isocyanurate di (meth) acrylate, Tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, caprolactone-modified tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene oxide (Hereinafter referred to as “EO”) modified trimethylolpropane tri (meth) acrylate, propylene oxide (hereinafter referred to as “PO”) modified trimethylolpropane tri (meth) acrylate, tripropylene glycol di (meth) acrylate, neopentyl Glycol di (meth) acrylate, bisphenol A diglycidyl ether end (meth) acrylic acid adduct, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, pentaerythritol tris (Meth) acrylate, pentaerythritol tetra (meth) acrylate, polyester di (meth) acrylate, polyethylene glycol di (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipenta Rithritol penta (meth) acrylate, dipentaerythritol tetra (meth) acrylate, caprolactone modified dipentaerythritol hexa (meth) acrylate, caprolactone modified dipentaerythritol penta (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, EO modified Bisphenol A di (meth) acrylate, PO modified bisphenol A di (meth) acrylate, EO modified hydrogenated bisphenol A di (meth) acrylate, PO modified hydrogenated bisphenol A di (meth) acrylate, EO modified bisphenol F di (meth) In addition to acrylate, (meth) acrylate of phenol novolac polyglycidyl ether, etc., a compound represented by the following formula (14) can be exemplified.

[In the formula (14), “Acryl” represents an acryloyl group or a methacryloyl group. ]

  Commercially available products of these polyfunctional (meth) acrylic monomers include, for example, SA1002 (manufactured by Mitsubishi Chemical Corporation), biscoat 195, biscoat 230, biscoat 260, biscoat 215, biscoat 310, biscoat 214HP, biscoat 295, Biscoat 300, Biscoat 360, Biscoat GPT, Biscoat 400, Biscoat 700, Biscoat 540, Biscoat 3000, Biscoat 3700 (manufactured by Osaka Organic Chemical Industry Co., Ltd.), Kayarad R-526, HDDA, NPGDA, TPGDA, MANDA, R -551, R-712, R-604, R-684, PET-30, GPO-303, TMPTA, THE-330, DPHA, DPHA-2H, DPHA-2C, DPHA-2I, D-310, D-3 0, DPCA-20, DPCA-30, DPCA-60, DPCA-120, DN-0075, DN-2475, T-1420, T-2020, T-2040, TPA-320, TPA-330, RP-1040, RP-2040, R-011, R-300, R-205 (manufactured by Nippon Kayaku Co., Ltd.), Aronix M-210, M-220, M-233, M-240, M-215, M- 305, M-309, M-310, M-315, M-325, M-400, M-6200, M-6400 (above, manufactured by Toagosei Co., Ltd.), light acrylate BP-4EA, BP-4PA, BP-2EA, BP-2PA, DCP-A (above, manufactured by Kyoeisha Chemical Co., Ltd.), New Frontier BPE-4, BR-42M, GX-8345 (above, Daiichi Kogyo Seiyaku Co., Ltd.) Manufactured), ASF-400 (above, manufactured by Nippon Steel Chemical Co., Ltd.), lipoxy SP-1506, SP-1507, SP-1509, VR-77, SP-4010, SP-4060 (above, Showa Polymer ( And NK ester A-BPE-4 (manufactured by Shin-Nakamura Chemical Co., Ltd.).

  In addition, the compound which has a 3 or more (meth) acryloyl group in a molecule | numerator among these is preferable for the composition of this invention. Examples of the compound having 3 or more (meth) acryloyl groups include tri (meth) acrylate compounds, tetra (meth) acrylate compounds, penta (meth) acrylate compounds, hexa (meth) acrylate compounds and the like exemplified above. Among these, among them, trimethylolpropane tri (meth) acrylate, EO-modified trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) acrylate, ditri Methylolpropane tetra (meth) acrylate is particularly preferred. Each of the above compounds can be used alone or in combination of two or more.

The polyfunctional (meth) acrylic monomer may have a fluorine atom. By having a fluorine atom, the refractive index of the cured film obtained can be reduced. Examples of the polyfunctional (meth) acrylic monomer having a fluorine atom include triacryloylheptadecafluorononenylpentaerythritol, perfluoro-1,6-hexanediol di (meth) acrylate, octafluorooctane-1,6-di One kind of adduct of (meth) acrylate, octafluorooctanediol and 2- (meth) acryloyloxyethyl isocyanate, 2- (meth) acryloyloxypropyl isocyanate, 1,1- (bisacryloyloxymethyl) ethyl isocyanate Or the combination of 2 or more types is mentioned. Etc.
As a commercial item of the polyfunctional (meth) acryl monomer having a fluorine atom, for example,
Examples include LINC-3A manufactured by Kyoeisha Chemical Co., Ltd.

In addition, the compound (A) may be a known polymer having two or more (meth) acryloyl groups, and may further contain a fluorine atom, a silicon atom, or the like. By having a fluorine atom, the refractive index of the cured film obtained can be reduced. By having a silicon atom, improvement in thermal stability and mechanical strength can be expected.
Examples of such a polymer include polymers described in JP-A No. 2003-183322.

  The amount of compound (A) to be added is not particularly limited, but is usually in the range of 20 to 80% by weight, preferably 25 to 70% when the total amount of the composition other than the organic solvent is 100% by weight. Within the weight percent range. This is because the scratch resistance of the cured film may not be obtained when the amount of the compound (A) added is less than 20% by weight. On the other hand, when the amount exceeds 80% by weight, the refractive index of the cured film increases. This is because a sufficient antireflection effect may not be obtained.

(B) Compound that generates active species upon irradiation with radiation A compound that generates active species upon irradiation with radiation (hereinafter referred to as “photopolymerization initiator (B)”) is an optical radical that generates radicals as active species. Examples include generators. Radiation is defined as energy rays that can decompose active compounds to generate active species. Examples of such radiation include optical energy rays such as visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, and γ rays. However, it is preferable to use ultraviolet rays from the viewpoint of having a certain energy level, a high curing speed, and a relatively inexpensive irradiation apparatus, and a small size.

  Examples of the photopolymerization initiator (B) include, for example, acetophenone, acetophenone benzyl ketal, anthraquinone, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, carbazole, xanthone, 4-chloro Benzophenone, 4,4′-diaminobenzophenone, 1,1-dimethoxydeoxybenzoin, 3,3′-dimethyl-4-methoxybenzophenone, thioxanthone, 2,2-dimethoxy-2-phenylacetophenone, 1- (4-dodecylphenyl) ) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, triphenylamine, 2,4,6- Trimethylbenzoyldiphenylphosphine oxide, 1- Droxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, fluorenone, fluorene, benzaldehyde, benzoin ethyl ether, benzoin propyl ether, benzophenone, Michler ketone, 3-methylacetophenone, 3,3 ′ , 4,4′-tetra (tert-butylperoxycarbonyl) benzophenone (BTTB), 2- (dimethylamino) -1- [4- (morpholinyl) phenyl] -2-phenylmethyl) -1-butanone, 4- Examples include benzoyl-4′-methyldiphenyl sulfide, benzyl, or combinations of BTTB and xanthene, thioxanthene, coumarin, ketocoumarin, a compound represented by formula (16), and other dye sensitizers.

Among these photopolymerization initiators, 2,2-dimethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexyl phenyl ketone, 2,4,6- Trimethylbenzoyldiphenylphosphine oxide, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one, 2- (dimethylamino) -1- [4- (morpholinyl) phenyl] -2 -Phenylmethyl) -1-butanone, a compound represented by the formula (16), and the like are preferable, and 1-hydroxycyclohexyl phenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholine are more preferable. Linopropan-1-one, 2- (dimethylamino) -1- [4- (morpholinyl) Eniru] -2-phenyl-methyl) -1-butanone, can be exemplified compounds represented by the formula (16).
The photopolymerization initiator represented by the formula (16) is Irgacure 127 manufactured by Ciba Specialty Chemicals. Even when this initiator is used alone or in combination with another polymerization initiator, it is excellent in a cured product obtained by curing the composition of the present invention with a low irradiation light amount of 0.2 J / cm ² or less. High scratch resistance can be exhibited.

  The addition amount of the photopolymerization initiator (B) is not particularly limited, but is usually within the range of 1 to 10% by weight, preferably 1 to 10% when the total amount of the composition other than the organic solvent is 100% by weight. It is in the range of 5% by weight, more preferably in the range of 2 to 5% by weight. When the addition amount of the photopolymerization initiator (B) is less than 1% by weight, the curing reaction is insufficient and the scratch resistance may be lowered. On the other hand, if it exceeds 10% by weight, the refractive index of the cured film may increase and the antireflection effect may decrease.

(C) Compound having the structure represented by the general formula (1) The compound (C) having the structure represented by the following general formula (1) is decomposed by an acid and / or heat to cause carbon dioxide and volatility. It is a compound that liberates alcohol and can produce fine bubbles in the cured coating film. When this compound (C) is decomposed in the coating film, bubbles having a refractive index lower than that of the matrix are formed, and the refractive index of the obtained cured film can be reduced.

That is, when the composition of the present invention contains neither a photoacid generator nor a thermal acid generator, the photocured cured coating is heated to decompose the compound (C), and the cured coating Bubbles are formed.
When the composition of the present invention does not contain a photoacid generator and contains a thermal acid generator, an acid is generated by heating the photocured cured coating, and the compound ( C) is decomposed.
When the composition of the present invention contains a photoacid generator, an acid is generated by light irradiation, and the compound (C) is decomposed by this acid.

In formula, R < ¹ > -R < ⁴ > is respectively independently a C1-C6 alkyl group, and it is preferable that they are a methyl group or an ethyl group. R ⁵ and R ⁶ are a hydrogen atom or a methyl group, preferably a hydrogen atom. R ⁷ is alkylidene having 1 to 6 carbon atoms or alkylene having 2 to 6 carbon atoms, n is an integer of 1 to 6, and preferably 2 to 3.

Specific examples of the compound having a structure represented by the general formula (1) include compounds represented by the following formulas (1-1) and (1-2).
In formula (1-2), m is an integer of 1 to 100, and preferably an integer of 1 to 50.

The mechanism by which the compound (C) is decomposed by acid or heat to produce carbon dioxide and volatile alcohol is represented by the following reaction formula, taking the above formula (1-1) as an example.
Cleavage occurs at the location indicated by the dotted line in the above formula (1-1).

The amount of compound (C) added is usually in the range of 10 to 70% by weight when the total amount of the composition other than the organic solvent is 100% by weight. When the amount of compound (C) added is less than 10% by weight,
This is because sufficient bubbles cannot be present inside the coating film, and the refractive index may not decrease. On the other hand, if the weight exceeds 70%, the strength of the coating film may be reduced. For this reason, the amount of compound (C) added is preferably in the range of 10 to 60% by weight relative to the total amount of the composition other than the organic solvent, and in the range of 20 to 50% by weight. More preferably.

(D-1) Photoacid generator (D-2) Thermal acid generator In the composition of this invention, either one of a photoacid generator (D-1) and a thermal acid generator (D-2) or Both can be added.
The photoacid generator (D-1) refers to a compound that generates an acid upon irradiation, and the thermal acid generator (D-2) refers to a compound that generates an acid by heating.
As described above, when the photoacid generator (D-1) is added to the composition of the present invention, the compound (C) is decomposed by the acid generated by light irradiation, and bubbles are formed in the cured coating film. The refractive index of the cured coating film is reduced.
If the thermal acid generator (D-2) is added, the compound (C) is decomposed by the acid and heat generated by heating by irradiating the coating with light and then heating.

  The photoacid generator generates acid upon irradiation with active light such as visible light, ultraviolet light, electron beam, X-ray or the like. Onium salts, halogen-containing compounds, quinonediazide compounds, sulfonic acid ester compounds, and the like can be used. Specific examples thereof include diaryl iodonium salts, triarylphosphonium salts, trialkylsulfonium salts, diarylsulfonium salts, triarylsulfonium salts, dialkylphenacylsulfonium salts, diaryleudonium salts, aryldiazonium salts, trichloromethyl. Triazine, bromoacetylbenzene, diazoquinone compound, diazonaphthoquinone compound, phenol, resorcinol, pyrogallol, 1,2-dihydroxynaphthalene, 1,3-dihydroxynaphthalene, methanesulfonic acid, ethanesulfonic acid, propanesulfonic acid, butylsulfonic acid, camphor Sulfonic acid, benzene sulfonic acid, naphthyl sulfonic acid, aromatic tetracarboxylic acid ester, aromatic sulfonic acid ester, nitrobenzyl ester , Oxime sulfonic acid ester, aromatic N-oxyimide sulfonate, aromatic sulfamide, haloalkyl group-containing hydrocarbon compound, haloalkyl group-containing heterocyclic compound, naphthoquinone diazide 4-sulfonic acid ester, and the like. .

  The thermal acid generator (D-2) is generally a salt or ester compound of various acids, and decomposes by heating to become an acidic compound. The thermal acid generator is a substance that can accelerate the curing reaction when the coating film made of the curable composition is heated and cured, and the heating condition is improved to be milder. It is a substance that can do. There is no restriction | limiting in particular as this thermal acid generator, The various acids currently used as a hardening | curing agent for general urea resin, melamine resin, etc. and its salt can be utilized. Specific examples of acidic compounds and thermal acid generators include, for example, various aliphatic sulfonic acids and salts thereof, various aliphatic carboxylic acids and salts thereof such as citric acid, acetic acid, and maleic acid, and various types such as benzoic acid and phthalic acid. Examples thereof include aromatic carboxylic acids and salts thereof, various alkylbenzene sulfonic acids such as p-toluenesulfonic acid and dodecylbenzenesulfonic acid and ammonium salts thereof, various metal salts, phosphoric acid and organic acid phosphates, and the like.

  The total addition amount of the photoacid generator (D-1) and the thermal acid generator (D-2) is usually 0.1 to 20% by weight when the total amount of the composition excluding the organic solvent is 100% by weight. In the range of 0.5 to 10% by weight, more preferably in the range of 1 to 10% by weight. When the total addition amount of the photoacid generator (D-1) and the thermal acid generator (D-2) is less than 0.1% by weight, the decomposition of the component (C) may not sufficiently proceed, and the weight is 20%. If it exceeds%, the refractive index may increase and the mechanical strength may decrease.

(E) Silica particles having a number average particle diameter in the range of 1 to 100 nm Silica particles having a number average particle diameter in the range of 1 to 100 nm are cured films obtained by curing the curable composition of the present invention. It is preferably added in order to improve the scratch resistance, particularly steel wool resistance.
The number average particle diameter of the silica particles is measured with a transmission electron microscope. The number average particle diameter of the silica particles (E) is preferably 5 to 80 nm, and more preferably 10 to 60 nm.
As a silica particle (E), a well-known thing can be used and the shape is not specifically limited, either. As long as it is spherical, it is not limited to ordinary colloidal silica, and may be solid particles, hollow particles, porous particles, core-shell type particles, or the like. Moreover, it is not limited to a spherical shape, and may be an irregularly shaped particle. Colloidal silica having a solid content of 10 to 40% by weight is preferred. In order to further reduce the refractive index of the obtained cured film, it is preferable to use hollow silica particles.

The dispersion medium is preferably water or an organic solvent. Examples of organic solvents include alcohols such as methanol, isopropyl alcohol, ethylene glycol, butanol and ethylene glycol monopropyl ether; ketones such as methyl ethyl ketone and methyl isobutyl ketone; aromatic hydrocarbons such as toluene and xylene; dimethylformamide and dimethyl Examples include amides such as acetamide and N-methylpyrrolidone; esters such as ethyl acetate, butyl acetate and γ-butyrolactone; and organic solvents such as ethers such as tetrahydrofuran and 1,4-dioxane. Of these, alcohols and ketones are preferred. These organic solvents can be used alone or in combination of two or more as a dispersion medium.
As a commercial item of the particle | grains which have a silica as a main component, as a colloidal silica, for example, Nissan Chemical Industries Ltd. brand name: Methanol silica sol, IPA-ST, MEK-ST, MEK-ST-S, MEK-ST- L, IPA-ZL, NBA-ST, XBA-ST, DMAC-ST, ST-UP, ST-OUP, ST-20, ST-40, ST-C, ST-N, ST-O, ST-50, ST-OL etc. can be mentioned.

Moreover, what carried out surface treatments, such as chemical modification, on the colloidal silica surface can be used, for example, a hydrolyzable silicon compound having one or more alkyl groups in the molecule or one containing a hydrolyzate thereof. Can be reacted. Such hydrolyzable silicon compounds include trimethylmethoxysilane, tributylmethoxysilane, dimethyldimethoxysilane, dibutyldimethoxysilane, methyltrimethoxysilane, butyltrimethoxysilane, octyltrimethoxysilane, dodecyltrimethoxysilane, 1,1. , 1-trimethoxy-2,2,2-trimethyl-disilane, hexamethyl-1,3-disiloxane, 1,1,1-trimethoxy-3,3,3-trimethyl-1,3-disiloxane, α-trimethylsilyl -Ω-dimethylmethoxysilyl-polydimethylsiloxane, α-trimethylsilyl-ω-trimethoxysilyl-polydimethylsiloxane hexamethyl-1,3-disilazane, and the like. A hydrolyzable silicon compound having one or more reactive groups in the molecule can also be used. Hydrolyzable silicon compounds having one or more reactive groups in the molecule are, for example, urea propyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropyl having NH ₂ groups as reactive groups. Trimethoxysilane and the like having an OH group, bis (2-hydroxyethyl) -3aminotripropylmethoxysilane and the like having an isocyanate group, 3-isocyanatopropyltrimethoxysilane and the like having a thiocyanate group 3 As thiocyanate propyltrimethoxysilane and the like having an epoxy group (3-glycidoxypropyl) trimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane and the like having a thiol group 3 -Mercaptopropyltrimethoxy Sisilane etc. can be mentioned. A preferred compound is 3-mercaptopropyltrimethoxysilane.

  Further, the silica particles (E) may be subjected to a surface treatment with an organic compound containing a polymerizable unsaturated group. By such surface treatment, it can be co-crosslinked with the UV curable acrylic monomer, and the scratch resistance is further improved.

  The addition amount of the silica particles (E) is usually in the range of 1 to 65% by weight, and 10 to 60% by weight, with or without surface treatment, when the total amount of the composition other than the organic solvent is 100% by weight. % Is preferable. If the added amount of silica particles (E) is less than 1% by weight, the added effect may not be exhibited. If the added amount exceeds 65% by weight, the surface slipperiness of the coating film may be lowered and mechanical strength may be caused. The amount of particles means solid content, and when the particles are used in the form of a solvent dispersion sol, the amount added does not include the amount of dispersion medium.

(F) Polydimethylsiloxane compound The polydimethylsiloxane compound (F) is a compound having a polydimethylsiloxane skeleton, which improves surface slipperiness and is effective in improving the scratch resistance of the resulting cured film, Since antifouling property can be provided, it is preferably used.
The polydimethylsiloxane compound (F) may be a compound having no reactive group, but preferably has a reactive group such as a (meth) acryloyl group or a hydroxyl group. Specific examples of the polydimethylsiloxane compound having a reactive group include Silaplane FM-4411, FM-4421, FM-4425, FM-7711, FM-7721, FM-7725, FM-0411, FM-0421, FM. -4425, FM-DA11, FM-DA21, FM-DA26, FM0711, FM0721, FM-0725, TM-0701, TM-0701T (manufactured by Chisso Corporation), UV3500, UV3510, UV3530 (Bicchemy Japan Corporation) Product), BY16-004, SF8428 (manufactured by Toray Dow Corning Silicone Co., Ltd.), VPS-1001 (manufactured by Wako Pure Chemical Industries), and the like. Silaplane FM-7711, FM-7721, FM-7725, FM-0411, FM-0421, FM-0425, FM0711, FM0721, FM-0725, VPS-1001 are particularly preferable.

  The addition amount of the polydimethylsiloxane compound (F) is not particularly limited, but is preferably in the range of 0.1 to 10% by weight with respect to the total amount of the composition other than the organic solvent, and is 1 to 10% by weight. % Is more preferable. If the amount of the polydimethylsiloxane compound (F) is less than 0.1% by weight, the resulting cured film may have insufficient antifouling properties and scratch resistance, which exceeds 10% by weight. This is because problems such as whitening of the coating film and peeling of the silicon compound from the surface of the cured film may occur.

(G) Organic solvent It is preferable to add an organic solvent to the composition of the present invention. By adding the organic solvent in this way, the low refractive index layer of the antireflection film that is a thin film can be formed uniformly, and as a result, the thickness of the antireflection film can be formed uniformly. As such an organic solvent, one type of methyl isobutyl ketone, methyl ethyl ketone, methanol, ethanol, t-butanol, isopropanol, or a combination of two or more types can be given.

  The addition amount of the organic solvent is not particularly limited, but is preferably 100 to 100,000 parts by weight when the total of components other than the organic solvent is 100 parts by weight. This is because when the amount added is less than 100 parts by weight, it may be difficult to adjust the viscosity of the composition. On the other hand, when the amount added exceeds 100,000 parts by weight, the storage stability of the composition decreases. This is because the viscosity may be too low and handling may be difficult.

(H) Other additives The composition of the present invention includes a photosensitizer, a polymerization inhibitor, a polymerization initiation assistant, an ultraviolet absorber, an antioxidant, and an antistatic agent within the range not impairing the object and effect of the present invention. It is also preferable to further contain an additive such as an inorganic filler other than the agent and the component (E), a pigment, and a dye.

  The composition of this invention can be manufactured by mixing said component (A)-(C) and component (D)-(H) as needed.

II. Cured film The cured film of the present invention is characterized by curing the composition of the present invention.
Since the cured film of the present invention has a low refractive index and is excellent in appearance and strength, it is useful as a low refractive index layer for an antireflection film.

III. Method for Producing Cured Film (1) When Using the Composition of the Present Invention That Does Not Contain Photoacid Generator (D-1) (hereinafter referred to as Composition 1 of the Present Invention) Method 1) is characterized in that it comprises a step of applying the composition 1 of the present invention containing no photoacid generator (D-1) to a substrate, photocuring, and heating.
As described above, even when the composition 1 of the present invention containing no photoacid generator (D-1) is photocured, no acid is generated and the compound (C) is not decomposed. Therefore, in order to reduce the refractive index of the cured film by generating bubbles in the cured coating film, the compound (C) is decomposed by heat itself, or an acid is generated from the thermal acid generator by heating. It is necessary to decompose the compound (C).

  Example 8 and Example 9 described later are the same as the composition, but in Example 8, a cured film was produced only by photocuring the coating film, and the refractive index was 1.42. On the other hand, the refractive index of the cured film of Example 9 in which the cured coating film was heated after photocuring was reduced to 1.36, indicating that the strength was also improved.

(2) When using the composition of the present invention containing the photoacid generator (D-1) (hereinafter referred to as composition 2 of the present invention) The method for producing a cured film of the present invention (hereinafter referred to as method 2) is as follows. The composition 2 of the present invention containing a photoacid generator (D-1) is applied to a substrate and photocured.
As described above, in the composition 2 of the present invention containing the photoacid generator (D-1), an acid is generated only by light irradiation, the acid decomposes the compound (C), and the cured coating film contains Bubbles can be generated.
Furthermore, by providing a step of heating the cured coating film after photocuring, the compound (C) is decomposed by heat, more bubbles are generated, and the refractive index of the cured film can be further reduced.

  Example 10 and Example 11 which will be described later are the same as the composition, but in Example 10, a cured film was produced only by photocuring the coating film, and the refractive index was 1.36. In contrast, it can be seen that the refractive index of the cured film of Example 11 in which the cured coating film was heated after photocuring was reduced to 1.35.

The structure of the cured film obtained by the method 2 will be described with reference to FIG.
FIG. 1 is a schematic diagram showing how bubbles are generated in a cured coating film by the method 1 of the present invention using the composition 2 of the present invention containing a photoacid generator (D-1).
On the base material 10, the composition 2 of this invention is apply | coated, and the coating film 20 is formed. Next, when the coating film 20 is irradiated with light, the coating film 20 is cured and bubbles 30 are generated inside the cured coating film 20. When the cured coating film 20 is further heated, more bubbles 30 are generated. Thereby, the refractive index of the cured film obtained is reduced.
Moreover, in the case of the said method 1, the bubble 30 does not generate | occur | produce by light irradiation, but the bubble 30 generate | occur | produces in the cured coating film 20 by heating.

IV. Antireflective film The antireflective film of the present invention comprises the cured film of the present invention as a low refractive index layer. Hereinafter, each layer included in the antireflection film of the present invention will be described.

(1) Low refractive index layer A low refractive index layer is comprised from the cured film obtained by hardening | curing the composition of this invention. Since the composition and the like of the composition are as described above, a specific description thereof will be omitted, and the refractive index and thickness of the low refractive index layer will be described below.

The refractive index of the cured film obtained by curing the composition of the present invention (the refractive index of Na-D line, measurement temperature 25 ° C.), that is, the refractive index of the low refractive index film should be 1.42 or less. Preferably, it is 1.40 or less. This is because if the refractive index of the low refractive index film exceeds 1.42, effective antireflection performance may not be achieved when combined with a high refractive index film.
In the case where a plurality of low refractive index films are provided, it is sufficient that at least one of the low refractive index films has a refractive index value within the above-mentioned range. Therefore, the other low refractive index films exceed 1.42. It may be a value.

The thickness of the low refractive index layer is not particularly limited, but is preferably 50 to 300 nm, for example. The reason for this is that when the thickness of the low refractive index layer is less than 50 nm, the adhesion to the high refractive index film as the base may be reduced. On the other hand, when the thickness exceeds 300 nm, optical interference occurs. This is because the antireflection effect may be reduced.
Therefore, the thickness of the low refractive index layer is more preferably 50 to 250 nm, and further preferably 60 to 200 nm. In order to obtain higher antireflection properties, when a plurality of low refractive index layers are provided to form a multilayer structure, the total thickness may be set to 50 to 300 nm.

(2) High refractive index layer The curable composition for forming the high refractive index layer is not particularly limited, but as a film forming component, an epoxy resin, a phenol resin, a melamine resin, an alkyd resin, a cyanate. It is preferable to include one kind alone or a combination of two or more kinds of resin, acrylic resin, polyester resin, urethane resin, siloxane resin and the like. If these resins are used, a strong thin film can be formed as the high refractive index layer, and as a result, the scratch resistance of the antireflection film can be remarkably improved.
However, the refractive index of these resins alone is usually 1.45 to 1.62, which may not be sufficient to obtain high antireflection performance. Therefore, it is more preferable to blend high refractive index inorganic particles, for example, metal oxide particles. Moreover, as a hardening form, although the curable composition which can be thermosetting, ultraviolet curing, and electron beam curing can be used, the ultraviolet curable composition with favorable productivity is used more suitably.

Further, the difference in refractive index between the low refractive index layer and the high refractive index layer is preferably 0.05 or more. If the difference in refractive index between the low refractive index layer and the high refractive index layer is less than 0.05, a synergistic effect in these antireflection film layers cannot be obtained, and the antireflection effect may decrease instead. It is.
Therefore, it is more preferable to set the refractive index difference between the low refractive index layer and the high refractive index layer to a value within the range of 0.1 to 0.5, and within the range of 0.15 to 0.5. More preferably, it is a value.

The thickness of the high refractive index layer is not particularly limited, but is preferably 50 to 30,000 nm, for example. The reason for this is that when the thickness of the high refractive index layer is less than 50 nm, the antireflection effect and adhesion to the substrate may be reduced when combined with the low refractive index layer, while the thickness is If the thickness exceeds 30,000 nm, optical interference may occur, and the antireflection effect may be reduced.
Therefore, the thickness of the high refractive index layer is more preferably 50 to 1,000 nm, and further preferably 60 to 500 nm. Further, in order to obtain higher antireflection properties, when a plurality of high refractive index layers are provided to form a multilayer structure, the total thickness may be set to 50 to 30,000 nm.
In addition, when providing a hard-coat layer between a high refractive index layer and a base material, the thickness of a high refractive index layer can be 50-300 nm.

(3) Hard coat layer Although the constituent material of the hard coat layer used for the antireflection film of the present invention is not particularly limited, for example, one kind or two or more kinds of siloxane resin, acrylic resin, melamine resin, epoxy resin, etc. Can be mentioned.

  Moreover, although it does not restrict | limit especially also about the thickness of a hard-coat layer, it is preferable to set it as 1-50 micrometers, and it is more preferable to set it as 5-10 micrometers. The reason for this is that when the thickness of the hard coat layer is less than 1 μm, the adhesion of the antireflection film to the substrate may not be improved. On the other hand, when the thickness exceeds 50 μm, it is uniform. This is because it may be difficult to form.

(4) Substrate The type of the substrate used for the antireflection film of the present invention is not particularly limited. For example, glass, polycarbonate resin, polyester resin, acrylic resin, triacetyl cellulose resin (TAC) The base material which consists of etc. can be mentioned. By using an antireflection film containing these base materials, excellent reflection can be achieved in a wide range of application areas of antireflection films such as camera lens parts, television (CRT) screen display parts, and color filters in liquid crystal display devices. The prevention effect can be obtained.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

Production Example 1
Synthesis of fluoropolymer A-1 (methacryl-modified fluoropolymer) having an ethylenically unsaturated group First, a hydroxyl group-containing fluoropolymer was synthesized. A 2.0-liter stainless steel autoclave with a magnetic stirrer was sufficiently replaced with nitrogen gas, and then 400 g of ethyl acetate, 53.2 g of perfluoro (propyl vinyl ether), 36.1 g of ethyl vinyl ether, 44.0 g of hydroxyethyl vinyl ether, Lauroyl oxide 1.00 g, azo group-containing polydimethylsiloxane (VPS1001 (trade name), Wako Pure Chemical Industries, Ltd.) 6.0 g and nonionic reactive emulsifier (NE-30 (trade name), Asahi Denka Kogyo ( 20.0 g) was charged, cooled to −50 ° C. with dry ice-methanol, and oxygen in the system was removed again with nitrogen gas.

Next, 120.0 g of hexafluoropropylene was charged, and the temperature increase was started. The pressure when the temperature in the autoclave reached 60 ° C. was 5.3 × 10 ⁵ Pa. Thereafter, the reaction was continued with stirring at 70 ° C. for 20 hours. When the pressure dropped to 1.7 × 10 ⁵ Pa, the autoclave was cooled with water to stop the reaction. After reaching room temperature, unreacted monomers were released and the autoclave was opened to obtain a polymer solution having a solid content concentration of 26.4%. The obtained polymer solution was put into methanol to precipitate a polymer, washed with methanol, and vacuum dried at 50 ° C. to obtain 220 g of a hydroxyl group-containing fluoropolymer. This is referred to as a hydroxyl group-containing fluoropolymer. Table 1 shows the monomers and solvents used.

It attached to the obtained hydroxyl-containing fluoropolymer, and measured the polystyrene conversion number average molecular weight by gel permeation chromatography. Moreover, the ratio of each monomer component which comprises a hydroxyl-containing fluoropolymer was determined from both NMR analysis results and elemental analysis results of ¹ H-NMR and ¹³ C-NMR. The results are shown in Table 2.

VPS1001 is an azo group-containing polydimethylsiloxane represented by the following formula (7) having a number average molecular weight of about 60,000 and a polysiloxane portion having a molecular weight of about 10,000.

NE-30 is a nonionic reactive emulsifier in which n is 9, m is 1, and u is 30 in the following formula (10).

Furthermore, in Table 2, the correspondence between the monomer and the structural unit is as follows.
Monomer Structural unit Hexafluoropropylene (a)
Perfluoro (propyl vinyl ether) (a)
Ethyl vinyl ether (b)
Hydroxyethyl vinyl ether (c)
NE-30 (f)
Polydimethylsiloxane skeleton (d)

Then, ethylenically unsaturated group containing fluoropolymer A-1 was synthesize | combined using the obtained hydroxyl group containing fluoropolymer. In a 1-liter separable flask equipped with a magnetic stirrer, a glass cooling tube and a thermometer, 50.0 g of the hydroxyl group-containing fluoropolymer obtained in Production Example 1 was used as a polymerization inhibitor and 2,6-di- 0.01 g of t-butylmethylphenol and 370 g of methyl isobutyl ketone (MIBK) were charged and stirred at 20 ° C. until the hydroxyl group-containing fluoropolymer was dissolved in MIBK and the solution became transparent and uniform.
Next, 15.1 g of 2-methacryloyloxyethyl isocyanate was added to this system and stirred until the solution became homogeneous, then 0.1 g of dibutyltin dilaurate was added to start the reaction, and the temperature of the system was changed to 55 to 55. The MIBK solution of fluoropolymer A-1 having an ethylenically unsaturated group was obtained by maintaining the temperature at 65 ° C. and continuing stirring for 5 hours.
2 g of this solution was weighed in an aluminum dish, dried on a hot plate at 150 ° C. for 5 minutes, and weighed to determine the solid content, which was 15.2% by weight. The compounds used, solvent and solid content are shown in Table 3.

Production Example 2
Production of compound represented by formula (1-1) In a three-necked flask previously dried and purged with nitrogen, 4 g (27.4 mmol) of 2,5-dimethyl-2,5-hexanediol (Wako Pure Chemical) and 0.1 g of potassium And vacuum-nitrogen injection was repeated three times. 40 mL of dehydrated THF was injected, and the mixture was heated to reflux until potassium was dissolved. After confirming that potassium was dissolved, the mixture was allowed to cool to 30 ° C., and dehydrated 8.86 g (54.7 mmol) of 1,1′-carbonylbis-1H-imidazole (Wako Pure Chemical Industries, Ltd.) prepared in another three-necked flask. Dropped into a THF (20 mL) solution. After completion of dropping, the mixture was heated and stirred at 65 ° C. for 2 hours. After the reaction solution was extracted with ethyl acetate-water, the ethyl acetate solution was dried over anhydrous magnesium sulfate, and the solvent was distilled off to obtain a crude product (7.49 g). The crude product was recrystallized with ethyl acetate to obtain a white crystalline solid (a).
The intermediate (a) 1.5 g (4.49 mmol), potassium carbonate 3.2 g, and 18-crown-6 (Wako Pure Chemical Industries, Ltd.) 0.08 g were put in a three-necked flask that had been dried and purged with nitrogen in advance. Nitrogen injection was repeated three times. After injecting 5 mL of dehydrated THF and 4.1 mL (45 mmol) of dehydrated n-butanol (Wako Pure Chemical Industries), the mixture was heated and heated to reflux with vigorous stirring for 5 hours. The disappearance of the raw materials was confirmed by TLC, and the heating was stopped. The reaction solution was cooled to room temperature, diluted with dichloromethane, insoluble matters were filtered off, the filtrate was extracted with dichloromethane-water, the dichloromethane solution was taken out, and dried over anhydrous magnesium sulfate. The product was purified by silica gel column chromatography to obtain the compound represented by the formula (1-1).

Production Example 3
Production of compound represented by formula (1-2) In Production Example 1, 4.2 mL (45 mmol) of dehydrated butanediol was used instead of 4.1 mL of dehydrated n-butanol, and methanol was used instead of purification by silica gel column chromatography. The compound shown by Formula (1-2) was obtained by performing the same operation except performing reprecipitation.

Production Example 4
Preparation of composition for hard coat layer In a container shielded from ultraviolet rays, 95 parts by weight of pentaerythritol hydroxytriacrylate, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one 5 By stirring 2 parts by weight and 100 parts by weight of MIBK at 50 ° C. for 2 hours, a uniform hard coat layer composition was obtained. 2 g of this composition was weighed in an aluminum dish, dried on a hot plate at 120 ° C. for 1 hour, and weighed to determine the solid content, which was 50% by weight.

Production Example 5
Preparation of substrate for coating curable composition On the TAC film (thickness 50 μm), the composition for hard coat layer prepared in Production Example 4 was coated with a wire bar coater to a film thickness of 6 μm, and in the oven And dried at 80 ° C. for 1 minute to form a coating film. Next, ultraviolet rays were irradiated under a light irradiation condition of 300 mJ / cm ² using a high-pressure mercury lamp in the air to prepare a curable composition coating substrate.

Example 1
(1) Production of curable composition 80 g of dipentaerythritol hexaacrylate, 20 g of the compound of formula (1-1), 2-hydroxy-1- {4- [4- (2-hydroxy-) as a photopolymerization initiator 2-methyl-propionyl) -benzyl] -phenyl} -2-methyl-propan-1-one (Irgacure 127, manufactured by Ciba Specialty Chemicals), and tris (4-methylphenyl) sulfonium tri as a photoacid generator 3 g of fluorometasulfonate (TS-01, manufactured by Sanwa Chemical Co., Ltd.) and 2922 g of MIBK were charged into a glass separable flask equipped with a stirrer and stirred at room temperature for 1 hour to obtain a uniform curable composition. Moreover, it was 3.5 weight% when solid content concentration was calculated | required.

(2) Production of cured film A curable composition was applied on a hard coat of a curable composition coating substrate obtained in Production Example 5 using a wire bar coater so as to have a film thickness of 0.1 μm. And dried at 80 ° C. for 1 minute to form a coating film. Subsequently, ultraviolet rays were irradiated with an irradiation light amount of 300 mJ / cm ² using a high-pressure mercury lamp under a nitrogen stream, and then heated in an oven at 100 ° C. for 2 minutes in the atmosphere to obtain a cured film.

Examples 2 to 16 and Comparative Examples 1 to 3
(1) Manufacture of curable composition Each curable composition was manufactured similarly to Example 1 except having set it as the composition shown to following Table 4-1 and 4-2.

(2) Production of cured film Each curing was carried out in the same manner as in Example 1 except that each curable composition obtained in (1) was used and the post-exposure heating conditions shown in Tables 4-1 and 4-2 were used. A membrane was produced.

<Characteristic evaluation of cured film>
About the cured film obtained by the Example and the comparative example, the following characteristic was measured and evaluated, and a result is shown to Table 4-1 and 4-2.

(1) Refractive index Each curable composition was applied onto a silicon wafer by a spin coater so that the thickness after drying was about 0.1 μm, and then 0.3 J / mm using a high-pressure mercury lamp under nitrogen. Curing was performed by irradiating with ultraviolet rays under light irradiation conditions of cm ² . The obtained cured film was measured refractive index at a wavelength of 589nm at 25 ° C. using an ellipsometer to ^{_(n D 25).}

(2) Appearance The produced cured film was visually observed and evaluated according to the following criteria.
(Evaluation criteria)
○: No application unevenness ×: Application unevenness

(3) Strength The prepared cured film was attached with steel wool (Bonster No. 0000, manufactured by Nippon Steel Wool Co., Ltd.) to a Gakushoku-type friction fastness tester (AB-301, manufactured by Tester Sangyo Co., Ltd.) The surface of the cured film was repeatedly rubbed three times under the condition of a load of 100 g, the presence or absence of scratches on the surface of the cured film was visually confirmed, and evaluated according to the following criteria.
(Evaluation criteria)
◎: No scratch ○: Slight scratch ×: Scratch on the entire surface

The components in Tables 4-1 and 4-2 represent the following.
Dipentaerythritol hexaacrylate: Nippon Kayaku Kayrad DPHA
Ethylenically unsaturated group-containing fluoropolymer A-1: synthesized in Production Example 1 Triacryloylheptadecafluorononenylpentaerythritol: manufactured by Kyoeisha Chemical Co., Ltd., LINC-3A
Irgacure 127: Photopolymerization initiator manufactured by Ciba Specialty Chemicals Co., Ltd., compound represented by the above formula (16) Compound of formula (1-1): synthesized in Production Example 2 Compound of formula (1-2): Production Example 3 Hollow silica particles: manufactured by Catalyst Kasei Co., Ltd., MIBK sol, number average particle size 50 nm
Solid silica particles: Nissan Chemical Co., Ltd. MEK sol, number average particle size 50 nm
Photoacid generator: Tris (4-methylphenyl) sulfonium trifluorometasulfonate, manufactured by Sanwa Chemical Co., Ltd., TS-01
Thermal acid generator: p-toluenesulfonic acid amine salt, manufactured by Nippon Cytec Co., Ltd., Catalyst 4050
Polydimethylsiloxane: manufactured by Chisso Corporation (trade name) FM0725, molecular weight 10,000

From the result of Table 4, the cured film formed by photocuring the curable composition of the Example containing the compound (C) and the photo-acid generator (D-1) has a low refractive index and excellent strength. It turns out that it has a good balance.
Furthermore, it can be seen that the refractive index is further reduced and the strength is improved by heating the cured film after photocuring.

  The curable composition of the present invention is useful for forming a low-refractive index layer of an antireflective film, because the refractive index is lower than before and a cured film excellent in appearance and strength can be provided. It is.

It is a schematic diagram which shows a mode that a bubble generate | occur | produces in a cured coating film by the method 1 of this invention using the composition 2 of this invention containing a photo-acid generator (D-1).

Explanation of symbols

10 Substrate 20 Coating 30 Bubble

Claims (5)

The following components (A) to (C):
(A) Compound having two or more (meth) acryloyl groups (B) Compound that generates active species upon irradiation with radiation (C) The following general formula (1)
(Wherein R ^{1 to} R ⁴ are each independently an alkyl group having 1 to 6 carbon atoms, R ⁵ and R ⁶ are a hydrogen atom or a methyl group, and R ⁷ is an alkylidene having 1 to 6 carbon atoms or A cured film formed by curing a curable composition containing a compound having a structure represented by (C2-6 alkylene, n is an integer of 1-6). Antireflection film . The antireflection film according to claim 1, wherein the curable composition further contains (D-1) a photoacid generator. The antireflection film according to claim 1, wherein the curable composition further contains (D-2) a thermal acid generator. The component (C) is any one or both of a compound represented by the following formula (1-1) and a compound represented by the following formula (1-2). The antireflection film as described.
(In Formula (1-2), m is an integer of 1-100.) The antireflection film according to any one of claims 1 to 4, wherein the curable composition further contains (E) silica particles having a number average particle diameter in the range of 1 to 100 nm .