JP4860952B2 - Coating composition for surface protective layer and antireflection film using the same - Google Patents

Description

  The present invention relates to a surface protective layer used for an optical member and an antireflection film having the surface protective layer.

  Conventionally, an antireflection film used for enhancing the visibility of a display device such as a display device has been mainly formed by laminating a plurality of layers. This includes a low refractive index layer (fluorine-based material, silica-based material, organic polymer, etc.) having a refractive index of 1.4 to 1.6, and a high refractive index layer (metal oxide) having a refractive index of 1.6 or more. The reflectance in the visible light region is reduced by alternately laminating two or more layers of the material and the like contained therein. However, such an antireflection film composed of a plurality of layers has a complicated manufacturing process, and also has a poor uniformity of reflectance in the visible light region, and undesired hues and glare occur. There was a problem.

  In order to keep the reflectance uniformly low over the entire visible light region, the following antireflection film consisting of a single layer is suitable. That is, glass (refractive index of about 1.52), polymethyl methacrylate (refractive index of about 1.49), polyethylene terephthalate (refractive index of about 1.54 to 1.67), triacetyl cellulose (refractive index of about 1.49) A single low refractive index layer is directly provided on a substrate such as, or an organic or inorganic hard coat layer (refractive index of about 1.45 to 1.70) is laminated on a substrate. By providing a single low refractive index layer, the reflectance in the visible light region is uniformly reduced. In this case, the closer the refractive index value of the low refractive index layer is to the square root of the refractive index of the substrate to be used (hard coat layer if a hard coat layer is present), the better the antireflection film. In other words, the antireflection performance can be improved by setting the refractive index of the low refractive index layer to less than 1.40, more preferably less than 1.30.

  As such a layer having a very low refractive index, a low refractive index layer made of silica fine particles and having minute voids inside or having minute irregularities on the surface has been proposed (Patent Documents 1 to 3). . These are useful in that it is possible to easily form a layer having a refractive index of less than 1.40. However, since there are voids in the layer, stress tends to concentrate on one point, and because the surface has irregularities, there is friction. Since the coefficient is high, there is a problem that mechanical strength, particularly scratch resistance is poor. In addition, there is a problem that contaminants are easily taken into the gaps and the gaps between the projections and depressions, and the antifouling property is poor.

In order to solve these problems, it is effective to further form a surface protective layer on the low refractive index layer. However, it is very difficult to form a thinner layer on the layer having voids while maintaining the voids. For example, in Patent Document 4, when laminating a fluorine-containing polymer layer on a low refractive index layer having voids, fluorine-based fine particles are allowed to coexist, the molecular weight of the fluorine-containing polymer is controlled, A method is disclosed in which the amount of the fluoropolymer entering the voids inside the low refractive index layer is reduced by suppressing the amount to a small amount. However, even with this method, a laminate in which the refractive index of the low refractive index layer is less than 1.40 has not been obtained. This is considered to be because the substance derived from the surface protective layer has not yet been prevented from entering the voids of the low refractive index layer, that is, it cannot be said that the above problem has been solved. In addition, the fluorine fine particles alone have a problem that the surface density is insufficient, and fingerprints are attached to the layer (inferior in fingerprint resistance). Furthermore, since the fine particles have a particle size distribution, In addition, there is a problem that fine particles having a small particle size penetrate into the lower layer of the surface protective layer, that is, the low refractive index layer, and a low refractive index cannot be obtained.
As described above, the conventional technology does not provide a surface protective layer excellent in mechanical strength and antifouling property, which is formed on a low refractive index layer having a refractive index of less than 1.40.
JP 11-292568 A JP-A-8-122501 Japanese Patent Laid-Open No. 11-6902 JP 2000-75105 A

The present invention has been made in view of the above points, and a surface protective layer that can be formed on a layer having voids while maintaining the voids and has excellent mechanical strength and antifouling properties. It is an object of the present invention to provide a coating composition for a surface protective layer that can be formed, and an antireflection film excellent in antireflection performance using the composition .

The coating composition for a surface protective layer of the present invention contains a fluorine-containing polymer, inorganic fine particles, and a substance capable of generating an acid or an alkali by heating or light irradiation, and the fluorine-containing polymer and the inorganic fine particles are covalently bonded. The fluorine-containing polymer is a copolymer containing at least a repeating unit of a fluorine-containing vinyl monomer and a repeating unit of a silicon compound containing both a vinyl group and a hydrolyzable silyl group in the same molecule. It is characterized by.

In the coating composition for a surface protective layer of the present invention, the fluorinated vinyl monomer is preferably a fluoroalkyl ester of (meth) acrylic acid .

In the coating composition for a surface protective layer of the present invention, the fluoroalkyl ester of (meth) acrylic acid contains at least two or more types of fluoroalkyl esters of (meth) acrylic acid having fluoroalkyl groups having different chain lengths. It is preferable to do.

In the coating composition for a surface protective layer of the present invention, the fluoroalkyl ester of (meth) acrylic acid is preferably a fluoroalkyl ester of acrylic acid .

In the coating composition for a surface protective layer of the present invention, the inorganic fine particles are preferably silica fine particles .

The coating composition for a surface protective layer of the present invention preferably further contains a partially hydrolyzed and / or partially dehydrated condensate of alkoxysilane .

The coating composition for a surface protective layer of the present invention preferably further contains an acid, alkali, or tin compound that promotes the formation of a covalent bond between the inorganic fine particles and the fluoropolymer .

The antireflection film of the present invention is characterized in that a surface protective layer obtained by curing the coating composition for a surface protective layer is laminated on a low refractive index layer having 3 to 50% by volume of voids. .

In the antireflection film of the present invention, the low refractive index layer preferably contains silica fine particles .

In the antireflection film of the present invention, the low refractive index layer preferably contains beaded silica fine particles.

In the antireflection film of the present invention, the refractive index of the low refractive index layer is preferably less than 1.40 .

The optical member of the present invention is preferably formed by forming a single layer or a plurality of layers including the antireflection film on a transparent optical substrate .

In the optical member of the present invention, the optical substrate is preferably a transparent resin substrate .

The method for producing a coating composition for a surface protective layer of the present invention comprises a copolymer comprising at least a repeating unit of a fluorine-containing vinyl monomer and a repeating unit of a silicon compound containing both a vinyl group and a hydrolyzable silyl group in the same molecule. A step of mixing a fluorine-containing polymer, inorganic fine particles, and a solvent, a step of forming a covalent bond between the fluorine-containing polymer and the inorganic fine particles, and a substance capable of generating acid or alkali by heating or light irradiation. And a step of adding.

In the method for producing a coating composition for a surface protective layer of the present invention, an acid, an alkali, or a tin compound that promotes the formation of a covalent bond between the inorganic fine particles and the fluoropolymer is added to the fluoropolymer and the It is preferable to form a covalent bond with the inorganic fine particles .

  The surface protective layer of the present invention can be formed on a layer having voids while maintaining the voids. That is, durability and antifouling properties can be further imparted to the low refractive index layer having excellent antireflection performance without impairing the antireflection performance. Moreover, it can be applied not only to the low refractive index layer but also to various uses that require surface protection, and is very useful in industry.

  In the case where a material containing a fluorine-containing polymer and inorganic fine particles is used for the surface protective layer (overcoat layer), the inventor of the present invention has applied the fluorine-containing polymer to the base layer, for example, a low refractive index layer composed of silica fine particles. To satisfy the characteristics of sufficiently suppressing the penetration, ensuring the surface denseness of the surface protective layer, and preventing the penetration of the inorganic fine particles having a relatively small particle diameter into the underlayer. Focusing on the points that have not been made, the present inventors have found that the fluorine-containing polymer and the inorganic fine particles are bonded to each other, the fluorine-containing polymer is held by the inorganic fine particles, and the penetration of the fluorine-containing polymer into the underlayer is prevented. It came to do. Thereby, since the fluorine-containing polymer is held on the surface of the surface protective layer, surface denseness is ensured. In addition, the fluorine-containing polymer and the inorganic fine particles are combined to increase the apparent particle size of the inorganic fine particles, and even the inorganic fine particles having a relatively small particle size can prevent penetration into the underlayer. Can do. Further, when the underlayer is a low refractive index layer composed of silica fine particles, the inorganic fine particles enter the concave and convex portions of the surface composed of silica fine particles, and the surface protective layer is flattened. For this reason, the adhesiveness between a surface protective layer and a low-refractive-index layer improves, and mechanical strength improves.

  Here, the surface protective layer according to the present invention will be described with reference to FIGS. FIGS. 1A and 1B are diagrams for explaining a case where a surface protective layer is formed using the coating composition for a surface protective layer according to the present invention. FIGS. 2A and 2B are diagrams for explaining a case where a surface protective layer is formed using a conventional coating composition for a surface protective layer.

  As shown in FIG. 1A, the surface protective layer coating composition 12 according to the present invention is bonded to the fluorine-containing polymer 122 and the inorganic fine particles 121 by a covalent bond. That is, the fluorine-containing polymer 122 exists around the inorganic fine particles 121. When such a surface protective layer coating composition 12 is applied onto the low refractive index layer 11 composed of the silica fine particles 11a as the underlayer, a surface protective layer 13 as shown in FIG. 1B is formed. . Since the inorganic fine particles 121 are covalently bonded to the fluorine-containing polymer 122 and have a large particle size, the silica fine particles can be used even if the inorganic fine particles 121 have a particle size distribution and have a relatively small particle size. It can prevent entering into the clearance gap between 11a. At this time, since the fluorine-containing polymer 122 is covalently bonded to the inorganic fine particles 121, the inorganic fine particles 121 are held in the form of holding the fluorine-containing polymer 122, and the fluorine-containing polymer 122 penetrates between the silica fine particles 11a of the underlayer. Can be prevented. For this reason, since the fluoropolymer 122 remains on the surface of the low refractive index layer 11 (because the fluoropolymer layer is fixed on the surface), the surface denseness of the surface protective layer 13 can be ensured. As a result, durability and antifouling properties can be further imparted to the low refractive index layer having excellent antireflection performance without impairing the antireflection performance.

  On the other hand, as shown in FIG. 2A, the conventional surface protective layer coating composition 22 has a fluorine-containing polymer 222 and inorganic fine particles 221 individually. That is, the inorganic fine particles 221 and the fluorine-containing polymer 222 are simply mixed. When such a surface protective layer coating composition 22 is applied onto the low refractive index layer 21 composed of the silica fine particles 21a as the underlayer, a surface protective layer as shown in FIG. 2B is formed. That is, in the surface protective layer, the inorganic fine particles 221 and a small amount of the fluorine-containing polymer 222 are present on the low refractive index layer 21, and a large amount of the fluorine-containing polymer 222 'permeates between the silica fine particles 21a of the underlayer. For this reason, the denseness of the surface of the surface protective layer cannot be ensured. As a result, durability and antifouling properties cannot be imparted to the low refractive index layer having excellent antireflection performance without impairing the antireflection performance.

The present invention will be specifically described below.
The surface protective layer of the present invention is characterized in that it contains a fluorine-containing polymer and inorganic fine particles, and is composed of a material in which the fluorine-containing polymer and the inorganic fine particles are bonded through a covalent bond. Such a surface protective layer can be manufactured through a step of applying a coating composition containing a fluorine-containing polymer and inorganic fine particles bonded thereto through a covalent bond onto a substrate. Hereinafter, the coating composition will be described in detail.

  The fluorine-containing polymer is not particularly limited, and tetrafluoroethylene, trifluoroethylene, vinylidene fluoride, vinyl fluoride, hexafluoropropylene, perfluoroalkoxyethylene, perfluoroalkylethylene, tetrafluoroethylene oxide, hexafluoropropylene oxide, Examples thereof include (co) polymers of fluorine monomers such as perfluoroalkylethylene oxide, fluoroalkyl ester of (meth) acrylic acid, and fluoroalkyl ester of α-fluoro (meth) acrylic acid. Here, (meth) acrylic acid means both acrylic acid and methacrylic acid. These may be a homopolymer or two or more kinds of copolymers, or may be a copolymer with any other monomer.

  Among these, a fluoroalkyl ester of (meth) acrylic acid is preferable because the method for producing the polymer is easy and the mechanical strength and antifouling property of the resulting surface protective layer are excellent. The fluoroalkyl ester of (meth) acrylic acid is a linear or branched alcohol having a structure in which some or all of the hydrogen atoms present on the carbon atom are substituted with fluorine atoms, (meth) acrylic acid, Is an ester having a dehydrated condensation structure. The α-position, β-position and ω-position of the alcohol do not necessarily have to be fluorinated. In particular, those in which the α-position or both of the α-position and the β-position are not fluorinated are preferable because the ester has high stability. Examples of fluoroalkyl esters of (meth) acrylic acid that can be used include 2,2,2-trifluoroethyl acrylate, 2,2,2-trifluoroethyl methacrylate, 1,1,1,3,3,3 -Hexafluoro-2-propyl acrylate, 1,1,1,3,3,3-hexafluoro-2-propyl methacrylate, perfluoroethyl methyl acrylate, perfluoroethyl methyl methacrylate, perfluoropropyl methyl acrylate, perfluoropropyl Methyl methacrylate, perfluorobutyl methyl acrylate, perfluorobutyl methyl methacrylate, perfluoropentyl methyl acrylate, perfluoropentyl methyl methacrylate, perfluorohexyl methyl acrylate, perful Rohexylmethyl methacrylate, perfluoroheptylmethyl acrylate, perfluoroheptylmethyl methacrylate, perfluorooctylmethyl acrylate, perfluorooctylmethyl methacrylate, perfluorononylmethyl acrylate, perfluorononylmethyl methacrylate, perfluorodecylmethyl acrylate, perfluorodecyl Methyl methacrylate, perfluoroundecyl methyl acrylate, perfluoro undecyl methyl methacrylate, perfluoro dodecyl methyl acrylate, perfluoro dodecyl methyl methacrylate, perfluoro tridecyl methyl acrylate, perfluoro tridecyl methyl methacrylate, perfluoro tetradecyl methyl acrylate, Perfluorote Radecylmethyl methacrylate, 2- (trifluoromethyl) ethyl acrylate, 2- (trifluoromethyl) ethyl methacrylate, 2- (perfluoroethyl) ethyl acrylate, 2- (perfluoroethyl) ethyl methacrylate, 2- (perfluoro) Propyl) ethyl acrylate, 2- (perfluoropropyl) ethyl methacrylate, 2- (perfluorobutyl) ethyl acrylate, 2- (perfluorobutyl) ethyl methacrylate, 2- (perfluoropentyl) ethyl acrylate, 2- (perfluoro) Pentyl) ethyl methacrylate, 2- (perfluorohexyl) ethyl acrylate, 2- (perfluorohexyl) ethyl methacrylate, 2- (perfluoroheptyl) ethyl acrylate, 2- (perf) Fluoroheptyl) ethyl methacrylate, 2- (perfluorooctyl) ethyl acrylate, 2- (perfluorooctyl) ethyl methacrylate, 2- (perfluorononyl) ethyl acrylate, 2- (perfluorononyl) ethyl methacrylate, 2- (perfluoro (Decyl) ethyl acrylate, 2- (perfluorodecyl) ethyl methacrylate, 2- (perfluoroundecyl) ethyl acrylate, 2- (perfluoroundecyl) ethyl methacrylate, 2- (perfluorododecyl) ethyl acrylate, 2- ( Perfluorododecyl) ethyl methacrylate, 2- (perfluorotridecyl) ethyl acrylate, 2- (perfluorotridecyl) ethyl methacrylate, 2- (perfluorotetradecyl) ethyl acetate Relate, 2- (perfluoro-tetradecyl) methacrylate. Among these, 2,2,2-trifluoroethyl acrylate, 1,1,1,3,3,3-hexafluoro-2-propyl acrylate, perfluoroethyl methyl acrylate, perfluoropropyl methyl acrylate, perfluorobutyl Methyl acrylate, perfluoropentylmethyl acrylate, perfluorohexylmethyl acrylate, perfluoroheptylmethyl acrylate, perfluorooctylmethyl acrylate, perfluorononylmethyl acrylate, perfluorodecylmethyl acrylate, perfluoroundecylmethyl acrylate, perfluorododecylmethyl Acrylate, perfluorotridecylmethyl acrylate, perfluorotetradecylmethyl acrylate, 2- (trifluoromethyl E) ethyl acrylate, 2- (perfluoroethyl) ethyl acrylate, 2- (perfluoropropyl) ethyl acrylate, 2- (perfluorobutyl) ethyl acrylate, 2- (perfluoropentyl) ethyl acrylate, 2- (perfluoro) Hexyl) ethyl acrylate, 2- (perfluoroheptyl) ethyl acrylate, 2- (perfluorooctyl) ethyl acrylate, 2- (perfluorononyl) ethyl acrylate, 2- (perfluorodecyl) ethyl acrylate, 2- (perfluoro Of acrylic acid such as undecyl) ethyl acrylate, 2- (perfluorododecyl) ethyl acrylate, 2- (perfluorotridecyl) ethyl acrylate, 2- (perfluorotetradecyl) ethyl acrylate With Le Oro alkyl ester is more preferable because tractable increases the solubility of the polymer.

  The above (meth) acrylic acid ester may be used alone, but two or more, more preferably three or more, more preferably four or more (meth) acrylates having fluoroalkyl groups having different chain lengths are used. It is desirable to use it as a copolymer because the mechanical strength of the surface protective layer to be obtained may be increased.

  The fluorine-containing polymer used in the present invention may be a polymer composed only of the above-described (meth) acrylic acid fluoroalkyl ester, but is preferably a copolymer with a fluorine-free (meth) acrylic acid ester. In addition to improved solubility in various solvents, handling is facilitated, and antifouling properties may be further improved, which is preferable. This effect tends to be manifested when the fluorine-containing (meth) acrylic acid ester is a long chain ester, preferably an ester having 8 or more carbon atoms, specifically octyl (meth) acrylate, (meta ) Nonyl acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, (meth) Preferred are hexadecyl acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, and the like. The content of the (meth) acrylic acid ester not containing fluorine in the fluorine-containing polymer is 1 to 80% by weight, more preferably 5 to 50% by weight, and still more preferably 10 to 40% by weight.

  The coating composition used for producing the surface protective layer of the present invention must contain inorganic fine particles in addition to the fluorine-containing polymer, and the fluorine-containing polymer must be bonded to the inorganic fine particles via a covalent bond. It is. That is, the fluorine-containing polymer needs to have at least one functional group capable of forming a covalent bond with inorganic fine particles in the molecule. Examples of a method for introducing such a functional group into a polymer molecule include the following methods (a) to (c).

(A) a functional group capable of forming a covalent bond with a silica fine particle in a side chain, which is a copolymer of the fluorine-containing monomer and a comonomer having a functional group capable of forming a covalent bond with a silica fine particle Is introduced.
(B) It is possible to perform a polymerization reaction using a polymerization initiator having a functional group capable of forming a covalent bond with silica fine particles and / or a polymerization terminator to form a covalent bond with silica fine particles at the terminal. Introduce a functional group.
(C) The surface of the silica fine particles is modified with a functional group capable of initiating polymerization, and the fluorine-containing polymer is graft polymerized.

Among these methods, the simplest method (a) is preferable. When the method (a) is employed, the most preferred examples of the comonomer having a functional group capable of forming a covalent bond with silica fine particles include compounds represented by the following formula (1).
R ¹ SiR ² _n (OR ³ ) _3-n (1)
(In the formula, R ¹ represents an organic substituent containing a carbon-carbon double bond. R ² and R ³ each independently represents an arbitrary organic substituent. N = 0 to 2)

Specific examples of R ¹ include vinyl group, allyl group, (meth) acryloxymethyl group, (meth) acryloxyethyl group, (meth) acryloxypropyl group, etc. Specific examples of R ² Examples thereof include a methyl group, an ethyl group, and a phenyl group. Specific examples of R ³ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, and a t-butyl group. , 2-methoxyethoxy group, 2-ethoxyethoxy group and the like.

  Among the compounds represented by the formula (1), preferred are vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, acryloxymethyltrimethoxysilane, and methacryloxymethyl. Trimethoxysilane, acryloxymethyltriethoxysilane, methacryloxymethyltriethoxysilane, 2-acryloxyethyltrimethoxysilane, 2-methacryloxyethyltrimethoxysilane, 2-acryloxyethyltriethoxysilane, 2-methacryloxyethyl Triethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, 3-methacryloxypropyltriethoxy It is a run. Of these, most preferred are 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane.

  Of course, the comonomer having a functional group capable of forming a covalent bond with silica fine particles is not limited to the compound represented by the above formula (1), and has, for example, a (meth) acrylic acid ester having a hydroxyl group and an epoxy ring ( It is also possible to use (meth) acrylic acid esters, (meth) acrylic acid t-butyl esters and adamantyl esters (which are easily hydrolyzed to generate carboxyl groups).

  The molecular weight of the fluorine-containing polymer is not particularly limited, but a weight average molecular weight value in the range of 1,000 to 1,000,000, more preferably 5,000 to 100,000, and still more preferably 10,000 to 50,000 is suitable.

  The content of the fluorinated monomer unit in the fluorinated polymer is 5 to 99 mol%, preferably 10 to 90 mol%, more preferably 20 to 70 mol in terms of the ratio of the number of repeating units of the fluorinated monomer to the number of all repeating units. %, More preferably in the range of 30 to 49 mol%. The content of the comonomer unit in the fluoropolymer is 1 to 95 mol%, preferably 10 to 90 mol%, more preferably 30 to 80 mol% in terms of the ratio of the number of repeating units of the comonomer to the number of all repeating units. More preferably, it is the range of 50-70 mol%.

  As the fluorine-containing polymer, a single polymer having the same composition may be used, or a mixture of a plurality of polymers having different compositions may be used. Furthermore, you may use together other arbitrary polymers in the range which does not impair the effect of this invention.

  The surface protective layer and the coating composition of the present invention further contain inorganic fine particles. In addition to preventing the fluoropolymer from entering the inside of the voids when applying the coating composition on the low refractive index layer having voids, the inorganic fine particles increase the mechanical strength of the resulting surface protective layer itself. It also has the effect of Examples of the inorganic fine particles include silicon dioxide (silica) fine particles, titanium dioxide fine particles, aluminum oxide fine particles, zirconium oxide fine particles, calcium carbonate fine particles, barium sulfate fine particles, talc, kaolin and calcium sulfate fine particles. If the inorganic fine particles have conductivity, it is possible to impart an antistatic function. Inorganic fine particles having conductivity include inorganic oxides composed of oxides or composite oxides of at least one metal selected from zinc, tin, indium, antimony, titanium, gallium, aluminum, zirconium, molybdenum, cerium, tantalum, and yttrium. Fine particles (typically, there are ITO (tin-containing indium oxide) fine particles, ATO (tin-containing antimony oxide) fine particles), copper, silver, nickel, low melting point alloy (solder, etc.) metal fine particles, Known materials such as carbon black, metal fibers, and carbon fibers are used. Among these fine particles, silica fine particles are particularly preferable.

  The average particle size of the inorganic fine particles is preferably 0.01 to 2 μm, and more preferably 0.02 to 0.5 μm. Further, the inorganic fine particles may be used alone or as a mixture of plural kinds.

  The amount of the inorganic fine particles added is 0.001 to 100, preferably 0.01 to 10, more preferably 0.05 to 5, more preferably, in terms of (weight of inorganic fine particles) / (weight of fluoropolymer). Is in the range of 0.1 to 1, particularly preferably in the range of 0.3 to 0.8.

  As described above, in the coating composition, it is necessary that the fluorine-containing polymer and the inorganic fine particles are bonded via a covalent bond. Except when the fluorine-containing polymer is grafted from the surface of the inorganic fine particles, the fluorine-containing polymer used in the present invention is a functional group (alkoxysilyl group, hydroxyl group, epoxy group) capable of forming a covalent bond with the inorganic fine particles in the molecule. , A carboxyl group, etc.), a covalent bond is formed by reacting the functional group with inorganic fine particles. This reaction is most suitably carried out by dispersing inorganic fine particles in an organic solvent in which a fluorine-containing polymer is dissolved or a solvent such as water. The solvent is not limited, and any solvent can be used as long as it can dissolve the fluorine-containing polymer and can stably disperse the inorganic fine particles. The reaction can be accomplished by stirring for 10 minutes to 1 week in the range of room temperature to 100 ° C. In order to accelerate the reaction, it is also effective to add a catalyst such as a known acid, alkali or tin compound. The fluorine-containing polymer does not need to have all the molecules bonded to the inorganic fine particles through covalent bonds in the coating composition, and is 50% by weight or more, preferably 75% by weight or more, more preferably 90% by weight of the total amount of the fluorine-containing polymer. It is sufficient that at least wt% is bonded to the inorganic fine particles. The degree to which the fluorine-containing polymer is bonded to the inorganic fine particles can be determined by, for example, a method such as observation with an electron microscope after dispersing the coating composition using a nebulizer, or GPC (gel permeation chromatography). It can be evaluated by measuring the intensity ratio of the polymer peak before and after the reaction with the inorganic fine particles.

For the purpose of increasing the efficiency in the reaction of binding the fluoropolymer and the inorganic fine particles as described above, and further improving the crosslink density of the surface protective layer and increasing the mechanical strength and durability as described below, the following formula ( The alkoxysilanes represented by 2) are further allowed to coexist under the above reaction conditions, or the alkoxysilanes represented by the following formula (2) or a partially hydrolyzed product or partially dehydrated condensate thereof by a known method in advance. It is effective to modify the surface of the inorganic fine particles.
R ⁴ _n Si (OR ⁵ ) _4-n (2)
(In the formula, R ⁴ and R ⁵ each independently represents an arbitrary organic substituent. N = 0 to 2)

  Specific examples of the alkoxysilanes that can be suitably used include tetramethoxysilane, tetraethoxysilane, methyltrimethoxysilane, methyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, and the like. The addition amount of these alkoxysilanes is 0-100 mol% with respect to the number of metal atoms contained in inorganic fine particles, Preferably it is the range of 0-10 mol%. Of course, these alkoxysilanes may be used alone or in combination.

  Since the surface protective layer of the present invention is desirably three-dimensionally cross-linked, it is also effective to add to the coating composition a substance capable of accelerating the reaction of the fluorine-containing polymer, inorganic fine particles, etc. causing three-dimensional cross-linking after coating. is there. In particular, inorganic fine particles and the compounds represented by the above formulas (1) and (2) are accelerated in the presence of acid or alkali, so that hydrochloric acid, nitric acid, sulfuric acid, formic acid, acetic acid, lactic acid, oxalic acid, etc. Suitable are alkalis such as acids, ammonia, organic amine, organic ammonium hydroxide, caustic soda, caustic potash, sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate. In order to further improve the stability of the coating composition, it is more effective to use a substance that can generate an acid or an alkali by external stimulation such as heating or light irradiation. Specifically, sulfonium-based and iodonium-based photoacid generators such as triarylsulfonium and diaryliodonium trifluoromethanesulfonate, nonafluorobutanesulfonate, hexafluorophosphate, and hexafluoroantimonate are suitable. In addition, the use of a known photoradical generator may be effective.

  A solvent is usually used to adjust the viscosity of the coating composition. As the solvent, water, any organic solvent, and a known reactive diluent are suitable. Of course, the solvent may be a single solvent or a mixture of a plurality of solvents.

  The coating composition for the surface protective layer further includes colorants (pigments, dyes), antifoaming agents, thickeners, leveling agents, flame retardants, ultraviolet absorbers, antistatic agents, antioxidants and modifying resins. May be added.

Next, the manufacturing method of the surface protective layer of this invention is demonstrated.
The surface protective layer of the present invention can be obtained by applying the coating composition on a substrate. As the substrate, any metal, glass, ceramic, plastic, etc. having any shape can be used. Among these, transparent substrates used for display materials such as displays are particularly required to have surface protection and antifouling properties. Examples of the transparent substrate include a transparent glass plate and a transparent resin substrate, and a transparent resin substrate is more preferable. As a transparent resin substrate, a (meth) acrylic resin plate, a (meth) acrylic resin sheet, a styrene- (meth) methyl acrylate copolymer resin plate, a styrene- (meth) methyl acrylate copolymer resin sheet, a polyethylene film, Polypropylene film, cellulose acetate film such as triacetyl cellulose, cellulose acetate propionate, polyester film such as polyethylene terephthalate and polyethylene naphthalate, polycarbonate film, norbornene film, polyarylate film and polysulfone film Can be mentioned.

  The coating method is carried out using known coating methods such as dipping, spin coater, knife coater, bar coater, blade coater, squeeze coater, reverse roll coater, gravure roll coater, slide coater, curtain coater, spray coater, and die coater. can do. Among these, when the transparent resin substrate is in the form of a film, a knife coater, bar coater, blade coater, squeeze coater, reverse roll coater, gravure roll coater, slide coater, curtain coater, spray coater, die coater, etc. that can be applied continuously. The method is preferably used.

  After coating, usually, standing, blowing, microwave irradiation, etc. are performed for 5 seconds to 10 minutes in the range of room temperature to 200 ° C. in order to dry the solvent contained in the coating composition. These temperature, time, and the like are appropriately determined according to the type of base material and solvent to be used.

  The thickness of the surface protective layer of the present invention is preferably in the range of 5 nm to 15 μm, and more preferably in the range of 10 nm to 5 μm. If the thickness is less than 5 nm, the sufficient function as the surface protective layer may not be exhibited. Conversely, if the thickness exceeds 15 μm, the internal stress of the film increases, which may cause cracking or peeling.

  By performing the above steps, high mechanical strength and antifouling have a structure containing a fluorine-containing polymer and inorganic fine particles and having the fluorine-containing polymer and the inorganic fine particles bonded through a covalent bond. It is possible to produce a surface protective layer having properties.

  In order to further increase the mechanical strength and antifouling property of the surface protective layer, a fluorine-containing polymer, inorganic fine particles, or in some cases, further a formula (2 It is preferred that the alkoxysilanes represented by The three-dimensional crosslinking method is appropriately selected from heating, microwave irradiation, ultraviolet irradiation, electron beam irradiation and the like according to the mode of the three-dimensional crosslinking reaction and the type of catalyst. A plurality of these heating, microwave irradiation, ultraviolet irradiation, and electron beam irradiation may be used together, and their order is arbitrary. By this process, the functional group on the fluorine-containing polymer contained in the surface protective layer, the surface of the inorganic fine particles, and in some cases, the alkoxysilanes represented by the formula (2) are bonded to each other to form a strong three-dimensional network. It is possible to form a surface protective layer that is formed and is tough and excellent in durability.

  Since the surface protective layer of the present invention has high mechanical strength and antifouling properties, the effect can be exhibited by applying it on any substrate. Among them, it is particularly suitable for use for protecting the surface of a material having voids, and can be used very suitably for the purpose of protecting the surface of an antireflection film provided with a low refractive index layer having voids. As a method for producing such a low refractive index layer having voids, a method of removing the solvent from the gel layer containing the solvent by supercritical drying, or a chemical treatment for suppressing the shrinkage on the gel layer containing the solvent is performed. After the formation of a layer composed of a matrix in which pore assistants are dispersed, a method of removing the pore assistants, a method of introducing voids into the layers using hollow fine particles, and applying fine particles For example, a method of using a gap between the fine particles as a void is used. Among these, the method of applying fine particles and utilizing the gaps between the fine particles as voids is the simplest, and is suitable because a low refractive index layer having a low refractive index of less than 1.40 and high mechanical strength can be obtained. Yes.

  Examples of the fine particles include silicon dioxide (silica) fine particles, titanium dioxide fine particles, aluminum oxide fine particles, zirconium oxide fine particles, and organic polymer latex. Among these, silica fine particles having a low refractive index and sufficient strength are most suitable.

  The shape of the fine particles is not limited, and a spherical shape, a plate shape, a needle shape, a plurality of these shapes connected to form a chain or branched chain, and a plurality of these shapes are aggregated. Grapes tufts can be used. The “chain” includes those generally called “(short) fiber” and “pearl necklace”. The shape of these particles can be confirmed, for example, by observing with a transmission electron microscope.

  Among these, when a non-spherical material, that is, a plate shape, a needle shape, a chain shape, a branched chain shape, or a bunch of grapes is used, more voids are generated between adjacent particles, and the low refractive index is low. Since a refractive index layer can be obtained, it is preferable.

  When spherical, needle-like or plate-like fine particles are used, the average particle diameter is preferably in the range of 10 nm to 200 nm in consideration of the strength of the antireflection film, the generation of haze, the resolution of the fluoroscopic image, and the like. The average particle diameter is a value given by the formula of average particle diameter = (2720 / specific surface area) from the specific surface area (m2 / g) measured by the nitrogen adsorption method (BET method).

  What can be used in the case of using chain-like and / or branched chain-like fine particles, considers the strength and surface roughness (Ra) of the antireflection film, the occurrence of haze, the resolution of the fluoroscopic image, the visibility, and the like. Thus, a plurality of fine particles having an average particle diameter of 5 to 30 nm, more preferably 10 to 30 nm are arranged in a continuous manner and have an average length of 30 to 200 nm. The average particle diameter is a value obtained in the same manner as described above. The average length is a value measured by a dynamic light scattering method and is generally equivalent to a value called a particle diameter by a dynamic light scattering method.

  Among these fine particles, when a chain-like and / or branched chain-like one is used, more voids are generated between adjacent particles, and the refractive index is less than 1.40. In addition to being able to obtain a low refractive index layer, the number of points that come into contact with and bind to other fine particles per fine particle is increased, so that the strength of the low refractive index layer is increased, which is preferable. Of these, those having a two-dimensional or three-dimensionally curved shape are most preferable. As examples of such fine particles, for example, in the case of silica fine particles, “Snowtex (registered trademark) -OUP”, “Snowtex (registered trademark) -UP”, “Snowtex (registered)” manufactured by Nissan Chemical Industries, Ltd. Trademark) -PS-S "," Snowtex (registered trademark) -PS-SO "," Snowtex (registered trademark) -PS-M "," Snowtex (registered trademark) -PS-MO ", Nippon Shokubai Examples thereof include “Fine Cataloid F-120” manufactured by Kasei Kogyo Co., Ltd. These chain-like silica fine particles are composed of a dense silica main skeleton and have a chain-like and three-dimensionally curved shape.

  When coating on the surface of the antireflection film having voids as described above, the thickness of the surface protective layer is preferably in the range of 5 to 50 nm, considering the antireflection performance of the surface protective layer, and is preferably 10 to 30 nm. A range is more preferred.

  By the above method, even a low refractive index layer having a very low refractive index of less than 1.40 protects the surface while maintaining the refractive index of less than 1.40, and has high mechanical strength and antifouling properties. Can be granted. Further, according to the coating composition for the surface protective layer of the present invention, since the fluoropolymer and the inorganic fine particles are covalently bonded, when the film is formed, the underlayer is composed of fine particles such as silica fine particles. However, the fluorine-containing polymer does not penetrate between the fine particles, and the fluorine-containing polymer can remain in the surface layer of the surface protective layer. Thereby, the characteristics of the underlayer, for example, if the underlayer is a low refractive index layer, the refractive index can be kept low. Furthermore, since the surface protective layer according to the present invention is dense, there are few surface defects, and permeation of oil and fat components is suppressed.

  The surface protective layer of the present invention and the antireflection film provided therewith are not only for display materials such as the display as described above, but also for vision correction members such as eyeglass lenses, goggles, contact lenses, car windows and instrument panels. Automotive parts such as navigation systems, housing and building parts 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, electronic information devices such as touch panels, optical fibers, and optical disks Parts, lighting globes, fluorescent lamps, mirrors, clocks and other household items, showcases, foreheads, semiconductor lithography, copy materials, etc., pachinko table glass, game machines, etc., surface protection, antifouling, visibility It can be applied as a member in various fields that require improvement.

Examples carried out to clarify the effects of the present invention will be described below.
(1) Measurement of reflectance and refractive index Using a FE-3000 type reflection spectrometer (manufactured by Otsuka Electronics Co., Ltd.), a reflection spectrum in the wavelength range of 250 to 800 nm is measured, and the minimum value of the reflectance in the wavelength range is measured. Was defined as the minimum reflectance. Moreover, the refractive index of the low refractive index layer was calculated using software “FE-Analysis” attached to the apparatus.

(2) Scratch resistance test A surface property tester (manufactured by Imoto Seisakusho) was used. Steel wool (Bonster (registered trademark) # 0000, manufactured by Nippon Steel Wool Co., Ltd.) was attached to one end of a stainless steel column with a diameter of 15 mm, and after reciprocating 10 times on the antireflection film while applying a load of 200 g, the friction marks were visually observed. Observed at. The symbol “◯” indicates that almost no scratch is observed, “Δ” indicates that many scratches are observed, and “X” indicates that the antireflection film has almost disappeared.

(3) Pencil hardness Based on JIS K5400 description, it carried out under the load of 1 kg using the pencil of 2H hardness.

(4) Antifouling The surface protective layer was marked with a black oil pen and immediately wiped with a paper wiper. If the ink could be completely wiped off, it was marked as ◯, and if it could not be wiped off, it was marked as x.

(Synthesis Example 1)
Dipentaerythritol hexaacrylate (trade name DPE-6A, manufactured by Kyoeisha Chemical Co., Ltd.) 10 g, 1-hydroxycyclohexyl phenyl ketone (trade name Irgacure 184, manufactured by Ciba Specialty Chemicals) 0.5 g, ethanol 10 g, 3-methacryloxypropyl 1.0 g of trimethoxysilane (trade name: Sila Ace S710, manufactured by Chisso Corporation) was mixed to obtain a coating composition for a hard coat layer.

(Synthesis Example 2)
10 g of 15% by weight aqueous dispersion of beaded silica fine particles (trade name Snowtex (registered trademark) OUP, manufactured by Nissan Chemical Industries), 20 g of ethanol, 0.52 g of tetraethoxysilane, and 0.075 g of 1N nitric acid are mixed at room temperature. And stirred overnight. The reaction solution was further diluted 3.3 times with isopropyl alcohol to obtain a coating composition for a low refractive index layer.

(Synthesis Example 3)
12 g of a mixture of fluoroalkyl acrylate (trade name Cheminox FAAC-N, manufactured by NOK), 8 g of 3-methacryloxypropyltrimethoxysilane (trade name: Silaace S710, manufactured by Chisso), and 30 g of methyl ethyl ketone were placed in a flask. 0.05 g of ronitrile was added, and the mixture was stirred at 80 ° C. for 4 hours for polymerization. The reaction solution was poured into methanol, the precipitate was filtered, and vacuum dried to obtain a fluorinated copolymer. This fluorine-containing copolymer was dissolved in methyl ethyl ketone to obtain a 3% by weight solution, and a fluorine-containing copolymer solution A was obtained.

(Synthesis Example 4)
A fluorine-containing copolymer solution B was obtained in the same manner as in Synthesis Example 3 except that the amount of the mixture of fluoroalkyl acrylate was changed to 10 g and the amount of 3-methacryloxypropyltrimethoxysilane was changed to 10 g.

(Synthesis Example 5)
Except that the mixture of fluoroalkyl acrylates was changed to 2-perfluorooctylethyl acrylate (trade name Cheminox FAAC-8, manufactured by NOK), which was a single compound, the same operation as in Synthesis Example 4 was performed, and a fluorinated copolymer solution C was obtained. Obtained.

(Synthesis Example 6)
Spherical silica fine particle 20 wt% aqueous dispersion (trade name Snowtex (registered trademark) OS, manufactured by Nissan Chemical Industries) 2.5g, isopropyl alcohol 7.5g, tetraethoxysilane 0.087g, 1N nitric acid 0.025g mixed The silica fine particle dispersion D was prepared by stirring overnight at room temperature.

(Synthesis Example 7)
A silica fine particle dispersion E was prepared in the same manner as in Synthesis Example 6 except that 0.087 g of tetraethoxysilane was changed to 0.074 g of methyltriethoxysilane.

Example 1
The fluorine-containing copolymer solution A (0.33 g), propylene glycol monomethyl ether (0.67 g), the silica fine particle dispersion D (0.10 g), and 1N nitric acid (0.0003 g) were mixed and stirred overnight at room temperature for reaction. Furthermore, it diluted with propylene glycol monomethyl ether 3 times, 0.002g of photo-acid generators (triphenylsulfonium trifluoromethanesulfonate) were added, and the coating composition for surface protection layers was obtained.

  On a 125 μm-thick polyethylene terephthalate film (trade name: Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) having an easy adhesion treatment on one side, the above hard coat layer coating composition was applied to a bar coater (USA RD Specialties, Inc.). (Equipped with a # 7 rod manufactured by the company) and dried at 120 ° C. for 10 seconds, followed by an ultraviolet curing device (UVC-2519, equipped with a high-pressure mercury lamp, manufactured by USHIO INC.) With an output of 160 W The hard coat layer was formed by irradiating with ultraviolet rays at a conveyor speed of 2 m / min and a light source distance of 100 mm.

  On the hard coat layer, the above coating composition for a low refractive index layer is applied using a bar coater (equipped with a # 4 rod manufactured by RD Specialties, Inc., USA) and heated at 120 ° C. for 2 minutes. By curing, a low refractive index layer was formed.

  The surface protective layer coating composition is applied onto the low refractive index layer using a bar coater (equipped with a # 4 rod manufactured by RD Specialties, Inc., USA) and dried at 120 ° C. for 10 seconds. Subsequently, using an ultraviolet curing device (UVC-2519 type, equipped with a high-pressure mercury lamp, manufactured by USHIO INC.), UV irradiation was performed at an output of 120 W, a conveyor speed of 2 m / min, a light source distance of 100 mm, and further at 120 ° C. The surface protective layer was formed by heat-curing for minutes.

(Example 2)
Except that the amount of the silica fine particle dispersion D was changed to 0.05 g, the same operation as in Example 1 was performed to form a surface protective layer on the low refractive index layer.

(Example 3)
A surface protective layer was formed on the low refractive index layer by performing exactly the same operation as in Example 1 except that the silica fine particle dispersion D was changed to 0.10 g of the silica fine particle dispersion E.

Example 4
A surface protective layer is formed on the low refractive index layer by performing exactly the same operation as in Example 1 except that the amount of the silica fine particle dispersion D is changed to 0.05 g and the amount of 1N nitric acid is changed to 0.0010 g. did.

(Example 5)
Except that the fluorine-containing copolymer solution A was changed to the fluorine-containing copolymer solution B, the same operation as in Example 1 was performed to form a surface protective layer on the low refractive index layer.

(Example 6)
Except that the fluorine-containing copolymer solution A was changed to the fluorine-containing copolymer solution C, the same operation as in Example 1 was performed to form a surface protective layer on the low refractive index layer.

  The components for Examples 1-6 are shown in Table 1 below. Table 2 shows the evaluation results of the surface protective layers of Examples 1 to 6. As can be seen from Table 2, in the surface protective layer according to the present invention, the refractive index of the low refractive index layer is kept very low, and therefore, the antireflection performance is excellent, and the scratch resistance, pencil hardness, antifouling It was also excellent in performance.

(Comparative Example 1)
A surface protective layer was formed in the same manner as in Example 1 except that the surface protective layer was not laminated on the low refractive index layer. The surface protective layer of Comparative Example 1 was similarly evaluated. The results are also shown in Table 2. As can be seen from Table 2, the refractive index of the low refractive index layer was kept very low and the pencil hardness was good, but both the scratch resistance and antifouling properties were low.

(Comparative Example 2)
A surface protective layer was formed on the low refractive index layer by performing the same operation as in Example 1 except that the silica fine particle dispersion was not added. The components for Comparative Example 2 are also shown in Table 1 below. The surface protective layer of Comparative Example 1 was similarly evaluated. The results are also shown in Table 2. As can be seen from Table 2, the refractive index of the low refractive index layer was remarkably increased, and therefore the antireflection performance was poor.

(Comparative Example 3)
A surface protective layer was formed on the low refractive index layer by performing the same operation as in Example 1 except that 1N nitric acid was not added, stirring was not performed overnight at room temperature, and a photoacid generator was not added. The components for Comparative Example 3 are also shown in Table 1 below. The surface protective layer of Comparative Example 3 was similarly evaluated. The results are also shown in Table 2. As can be seen from Table 2, the refractive index of the low refractive index layer was increased, and therefore, the antireflection performance was poor. And it was inferior to pencil hardness and antifouling property.

  The present invention is not limited to the embodiment described above, and can be implemented with various modifications. For example, the materials, numerical values, and the like in the above embodiment are exemplifications, and can be appropriately changed and implemented without departing from the scope of the present invention.

(A), (b) is a figure for demonstrating the case where a surface protective layer is formed into a film using the coating composition for surface protective layers which concerns on this invention. (A), (b) is a figure for demonstrating the case where a surface protective layer is formed into a film using the conventional coating composition for surface protective layers.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Low refractive index layer 11a Silica fine particle 12 Coating composition for surface protective layers 121 Inorganic fine particle 122 Fluoropolymer

Claims (15)

It contains a substance capable of generating an acid or an alkali by heating or light irradiation and fluoropolymer and inorganic fine particles, and the fluorine-containing polymer and the inorganic fine particles is bonded through a covalent bond, wherein the fluoropolymer A coating composition for a surface protective layer, which is a copolymer containing at least a repeating unit of a fluorine-containing vinyl monomer and a repeating unit of a silicon compound containing both a vinyl group and a hydrolyzable silyl group in the same molecule . 2. The coating composition for a surface protective layer according to claim 1 , wherein the fluorine-containing vinyl monomer is a fluoroalkyl ester of (meth) acrylic acid. The surface according to claim 2 , wherein the fluoroalkyl ester of (meth) acrylic acid contains at least two kinds of fluoroalkyl esters of (meth) acrylic acid having fluoroalkyl groups having different chain lengths. Coating composition for protective layer. The surface protective layer coating composition according to claim 2 or 3, wherein the fluoroalkyl ester of (meth) acrylic acid is a fluoroalkyl ester of acrylic acid. Surface protective layer coating composition according to any one of claims 1 to 4, wherein the inorganic fine particles are silica fine particles. Alkoxysilane partial hydrolysis and / or partial surface protective layer coating composition according to any one of claims 1 to 5, characterized by further comprising a dehydration condensate of. The surface protective layer coating according to any one of claims 1 to 6, further comprising an acid, an alkali, or a tin compound that promotes formation of a covalent bond between the inorganic fine particles and the fluorine-containing polymer. Composition. A surface protective layer obtained by curing the coating composition for a surface protective layer according to any one of claims 1 to 7 is laminated on a low refractive index layer having 3 to 50% by volume of voids. An antireflection film characterized by. 9. The antireflection film according to claim 8, wherein the low refractive index layer contains silica fine particles. 9. The antireflection film according to claim 8, wherein the low refractive index layer contains beaded silica fine particles. The antireflective film according to any one of claims 8 to 10 , wherein a refractive index of the low refractive index layer is less than 1.40. An optical member comprising a single layer or a plurality of layers including the antireflection film according to any one of claims 8 to 11 formed on a transparent optical substrate. The optical member according to claim 12, wherein the optical substrate is a transparent resin substrate. A fluorine- containing polymer, an inorganic fine particle , and a solvent, which are a copolymer containing at least a repeating unit of a fluorine-containing vinyl monomer and a repeating unit of a silicon compound containing both a vinyl group and a hydrolyzable silyl group in the same molecule, are mixed. A surface comprising: a step; a step of forming a covalent bond between the fluoropolymer and the inorganic fine particles; and a step of adding a substance capable of generating an acid or an alkali by heating or light irradiation. The manufacturing method of the coating composition for protective layers. An acid, alkali, or tin compound that promotes formation of a covalent bond between the inorganic fine particles and the fluorine-containing polymer is added to form a covalent bond between the fluorine-containing polymer and the inorganic fine particles. The manufacturing method of the coating composition for surface protective layers of Claim 14.

Images