JP4266790B2 - Antireflection film - Google Patents

Description

  The present invention relates to an antireflection film used by sticking to the front surface of a liquid crystal display, a CRT display, a plasma display or the like or a transparent cover substrate.

  When viewing exhibits, scenery, etc. through a transparent substrate such as a showcase, window, display, etc., it may be very difficult to see due to the reflection of external light or itself. Therefore, an antireflection film that suppresses reflection is laminated on a transparent substrate.

Conventionally, the antireflective film has a single layer of a low refractive index layer made of an inorganic compound or an organic fluorine compound on a transparent plastic film, or two or more layers of a low refractive index layer and a high refractive index layer. An antireflection film in which an antireflection layer having a laminated structure is laminated is used. These antireflection layers are usually inorganic compounds such as metal oxides, and wet coating, various vacuum processes, and the like are used as the formation method.
Japanese Patent Laid-Open No. 10-182558

  As a material used as a low refractive index layer in the antireflection layer, silicon oxide and a fluorine-based polymer are typical, but a film containing silicon oxide as a main component may be preferable from the viewpoint of balance with coating film strength. is there. However, the antireflection film tends to cause color unevenness due to slight film thickness fluctuation. In particular, wet coating tends to cause film thickness unevenness due to application, and thus it has been difficult to avoid color unevenness.

  An object of the present invention is to provide an antireflection film that does not cause color unevenness while using a film mainly composed of silicon oxide as an antireflection layer.

That is, the present invention relates to a silicon oxide obtained by hydrolyzing and polymerizing a silicon alkoxide containing a fluorine-based copolymer (meth) acrylate having the following monomers A and B as copolymerization components on at least one surface of a transparent substrate film. The antireflection film has a content of the fluorine copolymer (meth) acrylate of 0.01 to 0.5% by weight with respect to 100% by weight of the film made of silicon oxide .
Monomer A: Acrylic acid ester or methacrylic acid ester having a fluoroalkyl group
Monomer B: polyalkylene glycol acrylate or polyalkylene glycol methacrylate

  ADVANTAGE OF THE INVENTION According to this invention, the antireflection film which does not produce color nonuniformity can be provided, using the film | membrane which has silicon oxide formed by wet coating as a main component as an antireflection layer.

Hereinafter, the present invention will be described in detail.
[Transparent substrate film]
In the present invention, a polyester film is used as the transparent substrate film. As the polyester constituting the transparent substrate film, a linear saturated polyester composed of an aromatic dicarboxylic acid component and a diol component is used, and preferably polyethylene terephthalate or polyethylene naphthalate is used. As the transparent substrate, it is preferable to use a film in which the polyester is oriented by uniaxial or biaxial stretching. The thickness of the polyester substrate is preferably 5 to 500 μm from the viewpoint of processability and flexibility.

[Hard coat layer]
The transparent base material is preferably provided with an easy-adhesion layer for enhancing adhesion with the layer provided thereon. In order to improve the winding property, a filler or the like may be added to the easy adhesion layer. When the easy-adhesion layer is provided, the transparent substrate with the easy-adhesion layer is simply referred to as “transparent substrate”.

  When providing an easily bonding layer, as a material which comprises an easily bonding layer, resin, such as polyester, an acryl, and urethane, can be used, for example. The easy-adhesion layer is preferably formed in-line when the polyester substrate is formed.

  The hardness of the hard coat layer is preferably 2H or more, more preferably 3H or more, and it is desirable that optical properties are also taken into consideration. By applying this hard coat layer, it is possible to provide an effect such that it is difficult to be scratched even when used on the screen.

  The hard cord layer is usually made of an ionizing radiation curable resin or a photopolymerizable polymer. The ionizing radiation curable resin is formed from a paint containing at least a resin that is cured by electron beam or ultraviolet irradiation. Specifically, it contains a photopolymerizable prepolymer, a photopolymerizable monomer, and a photopolymerization initiator, and further contains additives such as a sensitizer, a non-reactive resin, a leveling agent, and a solvent as necessary. In order to cure the ionizing radiation curable coating material, an electron beam or an ultraviolet ray is irradiated. When irradiating an electron beam, a scanning or curtain type electron beam accelerator is used to irradiate an electron beam having an acceleration voltage of 1000 keV or less, preferably 100 to 300 keV and having a wavelength region of 100 nm or less. it can. In the case of irradiating ultraviolet rays, an ultra high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp, a carbon arc, a metal halide lamp, etc. are used, and ultraviolet rays having an energy of 50 to 300 kcal / mol in a wavelength region of 100 to 400 nm, preferably 200 to 400 nm. Irradiate.

  The structure and molecular weight of the photopolymerizable prepolymer are related to the curing of the ionizing radiation curable coating material, and determine the properties such as adhesion, hardness, and crack resistance of the ionizing radiation curable resin. The photopolymerizable prepolymer undergoes radical polymerization when the acryloyl group introduced into the skeleton is irradiated with ionizing radiation. Those that are cured by radical polymerization are particularly preferred because they have a high curing rate and a high degree of freedom in resin design.

  As the photopolymerizable prepolymer, an acrylic prepolymer having an acryloyl group is particularly preferable, and it has two or more acryloyl groups in one molecule and has a three-dimensional network structure. As the acrylic prepolymer, urethane acrylate, epoxy acrylate, melamine acrylate, polyester acrylate and the like can be used.

  The photopolymerizable monomer is used for diluting a high-viscosity photopolymerizable prepolymer to lower the viscosity and improving workability, and to impart coating strength as a crosslinking agent. Examples of the photopolymerizable monomer include monofunctional acrylic monomers such as 2-ethylhexyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, and butoxyethyl acrylate, 1,6-hexadiol acrylate, neopentyl glycol diacrylate, One type or two or more types of bifunctional acrylic monomers such as bilinic acid ester neopentyl glycol acrylate, polyfunctional acrylic monomers such as dipentaerythritol hexaacrylate, trimethylpropane triacrylate, and pentaerythritol triacrylate are used.

  Further, since the coating film becomes harder than necessary when the amount of the photopolymerizable monomer is increased, the mixing ratio may be appropriately selected so that the desired hardness or the desired flexibility can be obtained. For example, when used for bending the transparent hard coat film of the present invention, the hardness is adjusted by mixing non-reactive resins such as thermosetting, thermoplastic acrylic resin, and epoxy resin with excellent flexibility. can do.

  The photopolymerization initiator is added to start the reaction of the acryloyl group in a short time by irradiating with ionizing radiation and promote the reaction, and has a catalytic action. The photopolymerization initiator is particularly required when curing is performed by ultraviolet irradiation, and may not be required when irradiating a high energy electron beam. As types of photopolymerization initiators, there are those that undergo radical polymerization by cleavage, those that undergo radical polymerization by extracting hydrogen, and those that undergo cationic polymerization by generating ions.

  As a photoinitiator, it can select suitably. Examples include radical photopolymerization initiators such as benzoin ether, ketal, acetophenone, and thioxanthone, diazonium salts, diaryliodonium salts, triarylsulfonium salts, and complex cationic photopolymerization initiators. These may be used alone or in combination of two or more. The photopolymerization initiator is used in a mixture of 2 to 10% by weight, preferably 3 to 6% by weight based on the resin solid content. The most preferable material for the hard coat layer is an ultraviolet curable acrylic resin.

[Film mainly composed of silicon oxide]
The film | membrane which consists of silicon oxide containing the fluorine-type copolymerization (meth) acrylate in this invention is demonstrated.

  The film made of silicon oxide is usually formed by hydrolyzing and polymerizing an alkoxide of silicon. As the silicon alkoxide, tetraethyl silicate, tetramethyl silicate, tetraisopropoxy silicate, tetrabutoxy silicate may be used, and a multimer thereof may be used.

  This film made of silicon oxide contains fluorine-based copolymerized (meth) acrylate, and preferably fluorine-based copolymerized (meth) acrylate is 0.01 to 0 with respect to 100% by weight of the film mainly composed of silicon oxide. 0.5% by weight is contained. If it is less than 0.01% by weight, there is no effect of inclusion, and if it exceeds 0.5% by weight, the film strength is undesirably lowered.

As the fluorine-based copolymerized (meth) acrylate, specifically, a copolymerized methacrylate obtained by copolymerizing any of the following monomers can be used.
A: Acrylic acid ester or methacrylic acid ester having a fluoroalkyl group B: Polyalkylene glycol acrylate or polyalkylene glycol methacrylate The compound of A has the following formula: RfROCOR ¹ C = CH ₂
It is a compound represented by these.

In the formula, Rf is a linear or branched perfluoroalkyl group having 3 to 20 carbon atoms, R ¹ is a hydrogen atom or a methyl group, and R is a straight chain having 1 to 10 carbon atoms or A branched alkylene group, —SO ₂ N (R ² ) R ³ — group (R ² is an alkyl group having 1 to 10 carbon atoms, R ³ is a straight chain having 1 to 10 carbon atoms, or Represents a branched alkylene group) or —CH ₂ CH (OR ⁴ ) CH ₂ — group (R ⁴ represents a hydrogen atom or an acyl group having 1 to 10 carbon atoms).

Specific examples of the compound A are given below.
CF ₃ (CF ₂ ) ₇ (CH ₂ ) ₁₀ OCOCH = CH _2,
CF ₃ (CF ₂ ) ₆ CH ₂ OCOC (CH ₃ ) = CH ₂ ,
(CF ₃ ) ₂ CF (CF ₂ ) ₈ (CH ₂ ) ₂ OCOCH = CH _2,
CF ₃ CF ₂ (CF ₂ ) ₆ (CH ₂ ) ₂ OCOC (CH ₃ ) = CH _2,
CF ₃ CF ₂ (CF ₂ ) ₆ (CH ₂ ) ₂ OCOCH = CH _2,
CF ₃ (CF ₂ ) ₇ SO ₂ N (CH ₃ ) (CH ₂ ) ₂ OCOCH = CH _2,
CF ₃ (CF ₂ ) ₇ SO ₂ N (C ₂ H ₅ ) (CH ₂ ) ₂ OCOC (CH ₃ ) = CH ₂ ,
(CF ₃ ) ₂ CF (CF ₂ ) ₈ CH ₂ CH (OCOCH ₃ ) CH ₂ OCOC (CH ₃ ) = CH _2,
(CF ₃ ) ₂ CF (CF ₂ ) ₈ CH ₂ CH (OH) CH ₂ OCOCH = CH _2,

The compound of B has the following formula: CH ₂ ═CR ⁵ COO— (R ⁶ O) _n —R ⁷
It is a compound represented by these.

In the formula, R ⁵ and R ⁷ represent a hydrogen atom or a methyl group, R ⁶ represents an alkylene group having 2 to ⁶ carbon atoms, and n represents an integer of 3 to 50.

R ⁶ is generally preferably —CH ₂ CH ₂ —, but may be —CH (CH ₃ ) CH ₂ —, —CH (C ₂ H ₅ ) CH ₂ — or the like. That is, in the present invention, polyethylene glycol acrylate or methacrylate in which R ⁶ is —CH ₂ CH ₂ — can be used particularly preferably. In addition, n is selected from an integer of 3 to 50. However, particularly good results are obtained when n is selected from an integer of 9 to 25. Of course, it may be in the form of a mixture of two or more different types of R ⁶ or n.

Specific examples of the compound B Ru listed below.
C H ₂ = C (CH ₃ ) COO (CH ₂ CH ₂ O) ₉ H,
_{CH 2 = C (CH 3)} COO (CH 2 CH 2 O) 6 H,
_{CH 2 = CHCOO (CH 2 CH} (CH 3) O) 11 CH 3,
_{CH 2 = C (CH 3)} COO (CH 2 CH 2 O) 9 H,
_{CH 2 = C (CH 3)} COO (CH 2 CH 2 O) 5 (CH 2 CH (CH 3) O) 3 H,
_{CH 2 = C (CH 3)} COO (CH 2 CH 2 O) 9 CH 3,
_{CH 2 = C (CH 3)} COO (CH 2 CH 2 O) 23 CH 3,
_{CH 2 = C (CH 3)} COO (CH 2 CH 2 O) 40 H

  In the fluorinated copolymer (meth) acrylate used in the present invention, when an acrylic ester or methacrylic ester (monomer A) having a fluoroalkyl group is used as a copolymerization component, the copolymerization ratio is at least 5% by weight. , Preferably 10 to 30% by weight. If it is less than 5% by weight, the effect of leveling is not sufficient.

  In the copolymerized (meth) acrylate used in the present invention, when polyalkylene glycol (meth) acrylate (monomer B) is used as a copolymerization component, the copolymerization ratio is at least 60% by weight, preferably 65 to 90% by weight. %. If it is less than 60% by weight, dispersibility is not good, and defects such as cissing tend to occur.

  The molecular weight of the fluorinated copolymer (meth) acrylate used in the present invention is preferably 1000 to 500000, more preferably 5000 to 200000. If it is less than 1000, the durability is not sufficient, and if it is 500,000 or more, the viscosity of the treatment solution is too high, and the workability is unfavorable. The molecular weight is a value determined by gel permeation chromatography in terms of polystyrene. The fluorine-based copolymer (meth) acrylate used in the present invention may be a random copolymer or a block copolymer.

  In order to obtain the fluorine-based copolymerized (meth) acrylate used in the present invention, various polymerization reaction methods and conditions can be arbitrarily selected, and various polymerizations such as bulk polymerization, solution polymerization, emulsion polymerization, and radiation polymerization are performed. Any of the methods can be employed. For example, a method may be employed in which a mixture of compounds to be copolymerized is emulsified in water in the presence of a surfactant and copolymerized with stirring.

  As the polymerization initiator in the reaction system, various compounds of peroxide, azo or persulfuric acid can be used. If the surfactant contains polyethylene glycol acrylate or methacrylate as a constituent unit, it does not need to be added separately because it functions, but any anionic, cationic or nonionic emulsifier can be used. You may add to. It is also possible to dissolve a raw material polymerizable compound in an appropriate organic solvent and perform solution polymerization by the action of a polymerization initiation source (peroxide, azo compound, ionizing radiation or the like soluble in the organic solvent to be used).

In order to adjust the hardness, flexibility, and surface property of the film, an organosilicon compound represented by the following general formula may be appropriately blended.
R _a ¹ R _b ² SiX _{4- (a + b)}
(Wherein R ¹ and R ² are each an alkyl group, an alkenyl group, an allyl group, or a hydrocarbon group having a halogen group, an epoxy group, an amino group, a mercapto group, a methacryl group, a fluoro group or a cyano group; Is an alkoxyl group having 1 to 8 carbon atoms, a and b are 0, 1 or 2, respectively, and a + b is 2 or less.)

  In order to form a silicon oxide film from a silicon alkoxide, a silicon alkoxide is hydrolyzed to prepare a sol, which is applied to a transparent substrate film, dried and cured.

  The sol is prepared by dissolving an alkoxide of silicon and, if necessary, an organosilicon compound of the above formula in an appropriate solvent and hydrolyzing it. Examples of the solvent include alcohols such as methyl ethyl ketone, isopropyl alcohol, methanol, ethanol, methyl isobutyl ketone, ethyl acetate, and butyl acetate, and ketones, esters, halogenated hydrocarbons, aromatic hydrocarbons such as toluene and xylene. be able to. Mixtures of these may be used.

  The organosilicon compound is dissolved in a solvent so that the silicon compound is 0.1% by weight or more, preferably 0.1 to 10% by weight in terms of silicon oxide generated as a result of 100% hydrolysis and condensation of the silicon compound. If the concentration of the silicon oxide sol is less than 0.1% by weight, the formed sol film cannot sufficiently exhibit the desired characteristics, while if it exceeds 10% by weight, it becomes difficult to form a transparent homogeneous film. . Moreover, in this invention, if it is in the range of the above solid content, you may use together an organic substance and an inorganic substance binder.

  More water than necessary for hydrolysis is added to this solution, and preferably stirred at a temperature of 15 to 35 ° C., more preferably 22 to 28 ° C., preferably 0.5 to 48 hours, more preferably 2 to 35 hours. The hydrolysis is performed by Hydrolysis is preferably carried out using a catalyst, which is preferably an acid such as hydrochloric acid, nitric acid, sulfuric acid or acetic acid, and these acids are usually added in an aqueous solution of 0.0001N to 12N, preferably 0.0005N to 5N. It is hydrolyzed by water in the aqueous solution. When using an acid as a catalyst, it is preferable to add so that the pH of the whole solution may be 4-10. The catalyst is not necessarily an acid, and a base such as ammonia may be used.

  The silicon oxide sol can be applied by a method used in a normal coating operation. For example, a spin coat method, a dip method, a spray method, a roll coater method, a meniscus coater method, a flexographic printing method, a screen printing method, a beat coater method, and a micro gravure coater method can be used.

  A sol obtained by hydrolyzing silicon alkoxide is coated on a transparent substrate film and then polymerized to form a gel film. This polymerization is performed by heat-treating the coating layer after coating the sol on the transparent substrate film. This heat treatment is performed at a temperature not higher than the heat deformation temperature of the transparent substrate film. For example, when the transparent base material is a polyethylene terephthalate film, a silicon oxide gel film can be formed by performing a heat treatment at a temperature of about 80 to 150 ° C. for about 30 seconds to 5 minutes. Such heat treatment conditions vary depending on the type and thickness of the transparent film substrate to be used, and may be determined according to the type of transparent film substrate to be used.

In order to describe the present invention in detail, the following examples will be described.
Evaluation and adjustment of the fluorinated copolymer (meth) acrylate were performed as follows.
1. Application spots The back of the sample was applied with a black paint, and the antireflection surface was visually observed with natural light to confirm whether or not the appearance had mottled spots.
○: No mottled spots.
X: There are mottled spots.

2. Preparation of fluorine copolymer (meth) acrylate Fluorine copolymer acrylate 1
_{CF 3 CF 2 (CF 2 CF} 2) 6 CH 2 CH 2 OCOC (CH 3) = CH 2 to _{5g, CH 2 = C (CH} 3) CO (OC 2 H 4) 1 (O C 3 H 6) 9 OH (manufactured by NOF: Blemmer PEP series 10PEP-550B) 1.5 g, CH ₂ = C (CH ₃ ) CO (OC ₂ H ₄ ) ₉ OMe (Nippon Yushi: Blemmer PME-200) 23.5 g, isopropanol 60 g Was placed in a four-necked flask, and oxygen in the system was sufficiently replaced with nitrogen. Then, 0.1 g of azobisisobutyronitrile was added, and a copolymerization reaction was carried out with stirring at 70 ° C. for 10 hours. Gas chromatography showed that the conversion of the copolymerization reaction was 97% or more. From this conversion rate, it was found that the proportion of each structural unit in the obtained copolymer almost coincided with the proportion of the charged monomer. When the polymerization reaction was completed, 100 g of isopropanol was further added and diluted. The resulting copolymer solution contained 19.5% copolymer solids. The molecular weight of the copolymer was 17000 (in terms of styrene) according to gel permeation chromatography.

[Example 1]
A UV curable acrylic resin (Desolite, Z7501 manufactured by JSR Co., Ltd.) was coated on a polyethylene terephthalate film (OFW manufactured by Teijin DuPont Films Co., Ltd., 100 μm) with a bar coater, dried at 70 ° C. for 2 minutes, and then a high pressure mercury lamp Were irradiated with ultraviolet rays of 100 mJ / cm ² to form a hard coat layer so as to have a film thickness of 5 μm. Further, as a high refractive index layer, titanium alkoxide (manufactured by Nippon Soda TBT B-4) was dissolved in butanol, and the coating solution was applied with a bar coater and dried at 150 ° C. for 1 minute to form a thin film having a thickness of 100 nm. Further, 25 parts of tetraethyl silicate, 37.5 parts of ethanol, 23.5 parts of water and 0.2 part of hydrochloric acid were added, and 100 parts of ethanol and fluorinated co-polymer were added to the mixture after 24 hours at 23 ° C. 0.2 g of polymerized acrylate 1 was added, and this coating solution was applied with a bar coater and dried at 150 ° C. for 1 minute to form a thin film of about 100 nm.

[Comparative Example 1]
It carried out like Example 1 except not having added fluorine system copolymerization acrylate. The evaluation results are summarized in Table 1.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used as an antireflection film that is used by being attached to the front surface of a liquid crystal display, a CRT display, a plasma display or the like or a transparent cover substrate.

Claims (2)

A film made of silicon oxide formed by hydrolyzing and polymerizing a silicon alkoxide containing a fluorine-based copolymer (meth) acrylate having the following monomers A and B as copolymerization components is formed on at least one surface of a transparent substrate film. An antireflection film, wherein the content of the fluorine-based copolymer (meth) acrylate is 0.01 to 0.5% by weight with respect to 100% by weight of the film made of silicon oxide .
Monomer A: Acrylic acid ester or methacrylic acid ester having a fluoroalkyl group
Monomer B: polyalkylene glycol acrylate or polyalkylene glycol methacrylate 2. The antireflection film according to claim 1 , wherein the copolymerization ratio of the monomer A of the fluorine-based copolymerized (meth) acrylate is at least 5% by weight and the copolymerization ratio of the monomer B is at least 60% by weight .