JP2000000910A - Optically functional film and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To maintain a high function, high quality characteristics and productivity in an optically functional film and to put it into a practical use by forming a low refractive index layer directly or via other layer on a surface of a base material film, and forming the index layer as an SiO2 gel layer obtained by gelling an SiO2 sol having a molecular weight of a specific range. SOLUTION: A low refractive index layer 2 is formed on a surface of a base material film 1. An SiO2 gel layer is made of an SiO2 gel obtained by gelling an SiO2 sol having a molecular weight of 10,000 to 100,000 or preferably 20,000 to 50,000. When the molecular weight of the sol is smaller than this range, adhesive properties to the film is low and cannot be put into a practical use. When the molecular weight is larger than this range, an insoluble gel of a large quantity is generated, hence its solubility in a solvent is remarkably lowered and not preferable. Thus, the sol having the high molecular weight for improving the adhesive properties to the film while holding optical characteristics as they are can be sufficiently gelled at a temperature of the degree for not damaging the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to an ultraviolet shielding effect,
The present invention relates to an optically functional film excellent in heat ray reflection effect, antireflection effect and the like, and a method for manufacturing the same.

[0002]

2. Description of the Related Art Conventionally, an ultraviolet blocking effect, a heat ray reflecting effect,
Methods for forming an optically functional film having an anti-reflection effect and the like are generally roughly classified into a gas phase method and a solution method. The former method for producing an optically functional film by a gas phase method includes a vacuum deposition method,
There are a physical method such as a sputtering method and a chemical method such as a CVD method. In addition, the latter solution method includes a spray method,
There are an immersion method and a screen printing method.

[0003]

The method for producing an optically functional film by a vapor phase method has an advantage that a high-performance and high-quality thin film can be obtained. However, there is a problem that precise atmosphere control in a high vacuum system is required.
Further, a special heating or ion generation accelerating device is required, and there is a problem that the manufacturing cost is inevitably increased because the manufacturing device is complicated and large. Further, there is a problem that it is difficult to increase the area of the thin film or to manufacture a thin film having a complicated shape.

On the other hand, among the methods for producing an optical functional film by a coating method, those using a spray method have problems such as poor utilization efficiency of a coating liquid to be applied and difficulty in controlling film forming conditions. . Also, among the methods for producing an optical functional film by the coating method, the dipping method and the screen printing method are more efficient in using the film forming material than the spraying method, and are advantageous in mass production and equipment cost. There is. However, the optical functional film obtained by these coating methods has a problem that the function and quality are inferior to the film obtained by the gas phase method.

In recent years, as a method for obtaining a thin film of excellent quality by a coating method, a method has been proposed in which a dispersion of inorganic or organic ultrafine particles dispersed in an acidic or alkaline aqueous solution is coated on a substrate and baked. . According to this manufacturing method, there is an advantage that it is advantageous in terms of mass production and equipment costs. However, since a firing process at a high temperature is required during the manufacturing process, there is a drawback that a film cannot be formed on a plastic substrate film. Further, there is also a problem that the uniformity of the thin film is not sufficient due to a difference in the degree of shrinkage between the substrate and the coating film, and the performance is still inferior when compared with a thin film obtained by a gas phase method. Further, the heat treatment requires a long time, for example, several tens minutes or more, and has a disadvantage that productivity is poor.

[0006] In order to solve such problems, the present inventors have already reported the general formula R _m Si (OR ') _n (where R represents an alkyl group having 1 to 10 carbon atoms, a vinyl group, ) Acryloyl, epoxy, amide, sulfonyl, hydroxyl,
A reactive group such as a carboxyl group or a group containing these groups, R 'represents an alkyl group having 1 to 10 carbon atoms, m represents an integer of 0 to 3, n represents an integer of 1 to 4, and m + n represents an integer of 4; It is an integer. The SiO ₂ sol prepared by hydrolyzing the silicon alkoxide represented by the formula (1) is applied directly or via another layer on the base film, and the formed coating layer does not damage the base film. A method for efficiently producing a desired high-quality functional thin film without damaging the substrate film by heating or irradiating an active energy ray to form a SiO ₂ gel layer was proposed. However, the SiO ₂ sol obtained by an ordinary method has a practical problem that it easily peels off from the substrate film because of its poor adhesion to the substrate film when formed into a gel film.

In view of the above situation, the present inventors have conducted intensive studies, and as a result, the adhesion of the SiO ₂ gel layer to the base film is determined by using a SiO ₂ gel obtained by gelling a high molecular weight SiO ₂ sol. It was clarified that the optical functional film was able to maintain high performance and high quality characteristics and productivity, and was able to withstand practical use, and a method for producing the same.

[0008]

That is, according to the present invention, a low refractive index layer is formed directly or via another layer on the surface of a substrate film, and the low refractive index layer has a molecular weight of 10, 000-1
An optically functional film, which is a SiO ₂ gel layer obtained by gelling an SiO ₂ sol of 00000, and a method for producing the same.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in more detail with reference to preferred embodiments. The optical functional film of the present invention is obtained by imparting various optical functional characteristics to a base film. Specifically, for example, the optical functional film of the present invention is used for various displays such as word processors, computers, and televisions, the surface of polarizing plates used for liquid crystal display elements, sunglass lenses, prescription eyeglass lenses, and optical lenses such as camera finder lenses. This is useful for the purpose of providing a function required for a cover of various instruments, a window glass of a car, a train, and the like, for example, an antireflection function.

The structure of the optical functional film of the present invention will be described with reference to the drawings. FIG. 1 schematically illustrates a cross section of an embodiment in which a low refractive index layer 2 is formed on the surface of a base film 1. FIG. 2 shows that the low refractive index layer 2 is a hard coat layer 3.
FIG. 1 is a diagram schematically illustrating a cross section of an embodiment formed on a base material film 1 through a substrate. In FIG. 2, the low refractive index layer 2 is formed via the hard coat layer 3, but if necessary, a hard coat layer may be provided between the base film 1 and the low refractive index layer 2. In addition to or in place of 3, it is also possible to interpose another layer such as a transparent conductive layer, an adhesive layer, and a primer layer.

Examples of the film which can be preferably used as the base film constituting the optical functional film of the present invention include, for example, acetate butyrate cellulose film, polyether sulfone film, polyacrylic resin film, polyurethane resin film, polyester resin Transparent resin films such as films, polycarbonate films, polysulfone films, polyether films, trimethylpentene films, polyetherketone films, and (meth) acrylonitrile films. Among them, particularly, a uniaxially stretched polyester film is preferably used because it is excellent in transparency and has no optical anisotropy. Although the thickness of the base film is not particularly limited, it is usually 8 to 1,
Those having a size of about 000 μm are preferably used.

The SiO ₂ gel layer forming the low refractive index layer of the optically functional film of the present invention has a molecular weight of 10,000 to 10.
0000, preferably with a molecular weight of 20,000 to 50,
It is made of a SiO ₂ gel obtained by gelling a SiO ₂ sol of 000. When the molecular weight of the SiO ₂ sol is smaller than this range,
When the SiO ₂ gel layer is formed, the adhesion to the substrate film is poor, and the optical functional film as a product cannot withstand practical use. On the other hand, those having a molecular weight larger than this range are not preferable in that a large amount of insoluble gel is formed, and the solubility in a solvent is significantly reduced. The method for obtaining the above high molecular weight SiO ₂ sol is not particularly limited, but is most preferably prepared by hydrolyzing a silicon alkoxide as follows.

The silicon alkoxide preferably used as a raw material of the high molecular weight SiO ₂ sol has a general formula of R _m Si
(OR ') _n . However, R in the formula has 1 to 1 carbon atoms.
0 alkyl group, vinyl group, (meth) acryloyl group,
A reactive group such as an epoxy group, an amide group, a sulfonyl group, a hydroxyl group, a carboxyl group or a group containing these groups; R ′ represents an alkyl group having 1 to 10 carbon atoms;
Represents an integer of 0 to 3, n represents an integer of 1 to 4, and m + n is 4.

Specific examples of such compounds include, for example, tetramethoxysilane, tetraethoxysilane, tetraiso-propoxysilane, tetra-n-propoxysilane, tetra-n-butoxysilane, tetra-s
tetraalkoxysilanes such as ec-butoxysilane and tetratert-butoxysilane; tetrapentaethoxysilane, tetrapenta-iso-propoxysilane,
Tetrapenta-n-propoxysilane, tetrapenta-
n-butoxysilane, tetrapenta-sec-butoxysilane, tetrapenta-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, methyltributoxysilane,
Alkylalkoxysilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, hexyltrimethoxysilane; dimethyldiethoxysilane, dimethyldimethoxysilane, dimethyldipropoxysilane, dimethyldibutoxysilane, vinyltriethoxysilane, γ-methacryloxypropyltrisilane Examples include methoxysilane, γ-glycidoxypropyltrimethoxysilane, and 3-(-2-aminoethylaminopropyl) trimethoxysilane.

By hydrolyzing the silicon alkoxide,
An SiO ₂ sol can be obtained. The hydrolysis may be performed by dissolving the silicon alkoxide in a suitable solvent. Examples of usable solvents include ketones such as acetone, methyl ethyl ketone, and methyl isobutyl ketone;
Alcohols such as methanol, ethanol and isopropyl alcohol; esters such as ethyl acetate and butyl acetate; halogenated hydrocarbons such as carbon tetrachloride, chloroform and methylene chloride; aromatic hydrocarbons such as toluene and xylene; or mixtures thereof. Can be

The silicon alkoxide is preferably 0.1% in terms of SiO _2, which is assumed to be 100% hydrolyzed and condensed in the solvent.
It is dissolved so as to be at least 0.1% by weight, more preferably 0.1 to 10% by weight. This is because if the concentration of silicon alkoxide in the solvent in terms of SiO ₂ is too small, the characteristics of the optically functional film finally formed may not be sufficiently exhibited, while if the concentration is too large. This is because it may be difficult to form a transparent and homogeneous film. Further, in the solvent in which the silicon alkoxide is dissolved, Si
An organic or inorganic binder can be added as long as it does not hinder the preparation of the O ₂ sol.

In the hydrolysis of the silicon alkoxide, the amount of water required for the hydrolysis or more is added to the solvent in which the silicon alkoxide is dissolved as described above.
The stirring may be performed at a temperature of 5 to 35 ° C, more preferably 22 to 28 ° C, preferably for 5 to 30 hours, more preferably for 12 to 16 hours. In the hydrolysis, it is preferable to use a catalyst. As a catalyst that can be preferably used,
For example, acids such as hydrochloric acid, nitric acid, sulfuric acid, phosphoric acid and acetic acid can be mentioned. These acids are preferably from about 0.001-2.
An aqueous solution of 0.0N, more preferably about 0.005 to 5.0N, may be added to the solution in which the silicon alkoxide is dissolved. The water in the added aqueous solution can be used as water for hydrolysis.

The molecular weight of the SiO ₂ sol thus obtained is usually about 6,000 to 90,000.
For example, Technical report of IEICE.OME 97-4,1
By controlling the reaction using the method described in No. 9 (1997), a high molecular weight compound having a molecular weight of 10,000 or more can be obtained. That is, the general formula R _m Si (O
R ′) When hydrolysis and polycondensation are carried out by an acid catalyst while flowing a silicon alkoxide represented by _n at a predetermined flow rate of N ₂ , the amount of water used for hydrolysis and the removal amount of alcohol generated by hydrolysis. By appropriately controlling the amount, the acid hydrolysis component becomes a high molecular weight. SiO obtained as described above
₂ sol is a clear, colorless liquid, pot life is about 1
It is a stable solution for months. Therefore, it is most preferably used for forming the SiO ₂ gel layer of the optically functional film of the present invention, because it has good leakage property to the base film and excellent application suitability.

Various additives can be added to the SiO ₂ sol. Most preferred additives include curing agents that promote film formation. Examples of such a curing agent include an organic acid solution such as acetic acid and formic acid of an organic acid metal salt such as sodium acetate and lithium acetate. The concentration of the organic acid solution is preferably about 0.01 to 0.1% by weight. Further, the addition amount relative to the SiO ₂ sol is from about 0.1 to 1 parts by weight of the organic acid salt is preferred for SiO ₂ 100 parts by weight present in the sol.

Further, when the finally obtained optical functional film of the present invention is used for, for example, an antireflection film, a heat ray reflection film, a scattering film, or the like, the low refractive index formed by the SiO ₂ gel layer is used. It is preferable to adjust the refractive index of the refractive index layer to about 1.38 to 1.46. Specifically, a fluorine-based organic silicon compound or the like may be added to lower the refractive index of the layer, and an organic silicon compound or the like may be added to increase the refractive index of the layer. Compounds that can be added include, for example, tetraethoxysilane, tetramethoxysilane, tetrapropoxysilane, tetrabutoxysilane, alkyltrialkoxysilane, Corocoat 40 (manufactured by Colcoat), MS51 (manufactured by Mitsubishi Chemical), Snowtex (manufactured by Nissan Chemical) Organic silicon compounds such as Zafflon FC-110, 220, 250 (manufactured by Toa Gosei Chemical), sexual coat A-402B (manufactured by Central Glass), heptadecafluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, trifluoro Fluorinated organic silicon compounds such as propyltrimethoxysilane; and boron-based compounds such as triethyl borate, trimethyl borate, tripropyl borate, and tributyl borate.

[0021] These additives may be added during the preparation of the SiO ₂ sol may be added after preparation of the SiO ₂ sol. When these additives are used, the additives react with silanol groups during or after hydrolysis of the silicon alkoxide to obtain a more uniform and transparent SiO ₂ sol solution, and the refraction of the formed SiO ₂ gel layer. The rate can be adjusted to some extent.

The low-refractive-index layer of the optically functional film of the present invention may comprise the SiO ₂ film directly or through another layer on the base film.
It is preferable that the sol is applied by a coating method, and then, the coated material is formed as a SiO ₂ gel layer by heating or irradiation with active energy rays. Examples of the method of applying the SiO ₂ sol to the base film include spin coating, dipping, spraying, roll coating, meniscus coating, flexographic printing, screen printing, and bead coating. No.

As a method for gelling the SiO ₂ sol applied to the substrate film, for example, a method such as heating or active energy ray irradiation treatment may be mentioned. The gelation by heating is preferably performed at 150 ° C. or lower, more preferably 120 ° C. or lower, since the damage to the base film must be considered.

When the active energy ray irradiation treatment is used as a method for gelling the SiO ₂ sol, the active energy rays include, for example, electron beams or ultraviolet rays.
In particular, it is preferable to perform gelation with an electron beam. In the case of performing gelation with an electron beam, for example, it is released from various electron beam accelerators such as Cockloft-Walton type, Bande graph type, Resonant transformation type, Insulating core transformer type, Linear type, Dynamitron type and High frequency type. 50 to 1,000 KeV,
Preferably, an electron beam having an energy of about 100 to 300 KeV is used.

On the other hand, when gelling is performed by ultraviolet rays, for example, an ultra-high pressure mercury lamp, a high pressure mercury lamp, a low pressure mercury lamp,
It is preferable to use ultraviolet rays emitted from a light source such as a carbon arc, a xenon arc, and a metal halide lamp. When the active energy ray is an electron beam, the total irradiation amount of the active energy ray such as an electron beam or an ultraviolet ray is preferably 2 Mrad or more, more preferably 2 to 50 Mrad.

The electron beam irradiation on the SiO ₂ sol is preferably performed while replacing air with oxygen or in a sufficient oxygen atmosphere.
Formation, polymerization and condensation of ₂ , etc. are promoted, and a more uniform and high quality SiO ₂ gel layer can be formed. The thickness of the SiO ₂ sol layer thus formed is 0.001 to 1
0 μm, and preferably 0.01 to 1.0 μm.

In the present invention, the low refractive index layer can be formed on the base film via another layer. As the other layer, various layers are possible as described above. Hereinafter, a case where the other layer is the hard coat layer 3 as shown in FIG. 2 will be described as a typical example. In the present invention, the term “hard coat layer” refers to a layer showing a hardness of H or more in a pencil hardness test shown in JIS-K5400.

The hard coat layer is preferably formed using a reaction curable resin. The curable resin has good adhesion to the substrate film, has scratch resistance, hardness, light resistance, and moisture resistance, and has good adhesion to the low refractive index layer formed on the hard coat layer. If it is, there is no particular limitation. As such a reaction curable resin, for example, a (meth) acrylate of a polyfunctional compound such as an alkyd resin and a polyhydric alcohol (hereinafter, in the present specification, both acrylate and methacrylate are referred to as (meth) acrylate). And ionizing radiation-curable resins (including their precursors) such as those containing relatively large amounts of oligomers or prepolymers and reactive diluents.

The reactive diluent includes monofunctional monomers such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, vinyltoluene and N-vinylpyrrolidone, and polyfunctional monomers such as trimethylolpropane. Tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6- Hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate and the like can be mentioned.

Further, when the above-mentioned ionizing radiation-curable resin is used as an ultraviolet-curable resin, among these, as a photopolymerization initiator, for example, acetophenones, benzophenones, Michler benzoyl benzoate, α-amilo Xime esters, thioxanthones, and as a photosensitizer, for example, n-butylamine, triethylamine,
A mixture of tri-n-butylphosphine and the like is used.

A reactive organic silicon compound may be used in combination with the ionizing radiation-curable resin. The reactive organic silicon compound is used in a range of 10 to 100% by weight based on the total amount of the ionizing radiation-curable resin and the reactive organic silicon compound. In particular, when an ionizing radiation-curable organic silicon compound is used, it is possible to form a hard coat layer using only this as a resin component. Examples of such an ionizing radiation-curable silicon compound include an organic silicon compound having a molecular weight of 5,000 or less and having a plurality of groups capable of reacting and crosslinking by ionizing radiation, for example, a polymerizable double bond group. Such a reactive organosilicon compound may be a vinyl functional polysilane at one end, a vinyl functional polysilane at both ends, a vinyl functional polysiloxane at one end, a vinyl functional polysiloxane at both ends, or a vinyl functional compound obtained by reacting these compounds. Examples include polysilane or vinyl-functional polysiloxane.

Further, by setting the refractive index of the hard coat layer to be higher than that of the low refractive index layer, the low reflectivity of the optical functional film of the present invention can be further improved. The refractive index of a normal hard coat layer is 1.48 to
Although it is about 1.52, the preferable refractive index of the hard coat layer in the present invention is about 1.55 to 2.50.

In order to make the hard coat layer have a high refractive index,
Ultrafine particles of a metal or metal oxide having a high refractive index can be added to the layer-forming resin component. The ultrafine particles having a high refractive index used in the present invention have a particle diameter of 1 to 50.
nm and a refractive index of about 1.60 to 2.70 are preferable, and specifically, for example, ZnO (refractive index 1.9)
0), TiO ₂ (refractive index 2.3~2.7), CeO ₂ (refractive index 1.95), Sb ₂ O ₅ (refractive index 1.71), SnO
₂ , ITO (refractive index: 1.95), Y ₂ O ₃ (refractive index: 1.8)
7), fine powders such as La ₂ O ₃ (refractive index: 1.95), ZrO ₂ (refractive index: 2.05), Al ₂ O ₃ (refractive index: 1.63).

In order to form a hard coat layer using the reaction curable resin composition comprising the above components, the above components are dissolved or dispersed in an appropriate solvent to form a coating solution. Apply directly on the substrate film and cure, or
Alternatively, it can also be formed by applying the composition to a release film and curing it, and then transferring it to a base film using an appropriate adhesive. When the transfer method is used, the transfer may be performed after the low refractive index layer is formed on the hard coat layer. The thickness of the hard coat layer thus formed is usually about 1 to 50 μm, preferably 3 to 20 μm.
It is about μm.

The other layer may be formed by directly or indirectly applying a desired coating liquid on the transparent substrate film as described above. When a hard coat layer is formed by transfer on a hard coat layer previously formed on a release film, a coating liquid to be another layer (such as an adhesive layer) is applied, and then each layer is laminated. The above-described layers may be transferred to the transparent substrate film by laminating the release film and the transparent substrate film with the laminated surface of the release film facing inside, and then peeling the release film.

As described above, the optical functional film of the present invention
It can be used as a single-layer antireflection film or as a multilayer antireflection film. Further, in the method for producing an optical functional film of the present invention, another optical functional film having a desired function can be obtained by selecting a coating material to be used.

[0037]

The present invention will be described below more specifically with reference to examples and comparative examples. Example 1 (Two-Layer Antireflection Film) Preparation of SiO ₂ Sol for Forming Low Refractive Index Layer Methyltrimethoxysilane (METOS) was placed in a four-necked flask equipped with a stirrer, nitrogen inlet tube and outlet tube.
7 g (0.17 mol) and 14 ml of methanol were added, mixed, and cooled to 0 ° C. Water / hydrochloric acid was added thereto in a weight ratio of water / METOS = 1.30, hydrochloric acid / METOS =
0.105, and the mixture was stirred at room temperature for 10 minutes.

Next, at 70 ° C. while introducing dry nitrogen,
After stirring at a speed of 150 rpm for 3 hours, the solvent was distilled off under reduced pressure to obtain a highly viscous polymer. When the molecular weight of this highly viscous polymer was measured using GPC, the weight average molecular weight was 4 with respect to the polystyrene standard sample.
It was 2,000. This high molecular weight product is CH ₃ SiO _1.5
The high molecular weight METOS was dissolved in methyl ethyl ketone to obtain a high molecular weight SiO ₂ sol solution so that the solid content concentration assuming hydrolysis and condensation was 1.5% by weight.

Formation of High Refractive Index Hard Coat Layer A PET film (A-4350: trade name, manufactured by Toyobo) having a thickness of 100 μm was prepared as a base film. On the other hand, ZrO ₂ ultrafine particles having a refractive index of 1.9 (No. 1275)
A: Trade name, manufactured by Sumitomo Osaka Cement) and ionizing radiation-curable resin (X-12-2400-6: trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed at a weight ratio of 2: 1. The obtained resin composition was coated on the PET film with a thickness of 7 μm / dry.
Was applied by gravure reverse coating so that the solvent was removed by drying. After that, the electron beam was 5M at 175kv.
The coating was cured by rad irradiation to form a high refractive index hard coat layer (refractive index = 1.75).

On the high refractive index hard coat layer obtained in the preparation of the low refractive index layer,
The iO ₂ sol was applied so as to be 0.1 μm / dry. The following two methods were used for gelation conditions. That is, (1) when heat treatment is performed at 120 ° C. for 1 hour,
(2) The optical functional film (anti-reflective film) of the present invention was obtained by using an electron beam irradiation apparatus at 180 kv, 20 mA and irradiating 20 times with a single irradiation amount of 20 Mrad. In each case, the refractive index of the formed low refractive index layer was 1.42 to 1.46.

Embodiments 2 to 5 In place of METOS in Embodiment 1 above,
Using tetramethoxysilane, tetraethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane, respective optical functional films were obtained by heating and electron beam irradiation in the same manner as in Example 1 below.

Example 6 An optical functional film (antireflection film) of the present invention was obtained in the same manner as in Example 1 except that the low refractive index layer was formed directly on the substrate film. In each case, the refractive index of the formed low refractive index layer was the same as that of Example 1.

Evaluation of Characteristics of Antireflection Film The optical characteristics of the optical functional films of the present invention obtained in Examples 1 to 6 in total were 124.0% in total light transmittance and 0 in haze value. 0.5, the lowest reflectance in the visible light wavelength region was 1.2, and the antireflection performance was excellent. In addition, for the hard coat layer or the base film,
The evaluation of the adhesion of the O ₂ gel layer by a tape peeling test was 100% in both cases, and the adhesion to the hard coat layer or the substrate film was also good.

Comparative Example 1 An SiO ₂ sol was obtained under the same reaction conditions, except that the same materials as in Example 1 were used and nitrogen was not introduced. The molecular weight of the obtained SiO ₂ sol was 6,000. This SiO ₂ sol was applied on the high refractive index hard coat layer prepared in Example 1 so as to have a thickness of 0.1 μm / dry, and heat-treated at 120 ° C. for 1 hour to obtain an optical functional film for comparison. I got The refractive index of the low refractive index layer of this optical functional film was 1.42.

The optical characteristics of the optical functional film for comparison are as follows:
The total light transmittance was 94.0%, the haze value was 0.5, and the minimum reflectance in the wavelength region of visible light was 1.2, indicating antireflection performance equivalent to that of the optical functional film of the present invention. However, in the evaluation of the adhesion of the SiO ₂ gel layer to the hard coat layer by a tape peel test, partial peeling of the coating film was observed.

[0046]

As described above, according to the present invention, SiO 2 having a molecular weight of 10,000 to 100,000 is used as the low refractive index layer.
By using the SiO ₂ gel layer obtained by gelling the ₂ sol, it was possible to improve the adhesion to the hard coat layer or the base film while maintaining the optical characteristics. Such a high molecular weight SiO ₂ sol sufficiently gels at a temperature at which the base film is not damaged, and a gel layer having the same characteristics can be obtained by irradiation with active energy rays. The optical functional film of the present invention using these gel layers has various optical functions such as an excellent antireflection effect.

[Brief description of the drawings]

FIG. 1 is a diagram schematically illustrating a cross section of an optical functional film of the present invention.

FIG. 2 is a diagram schematically illustrating a cross section of the optical functional film of the present invention.

[Explanation of symbols]

 1: base film 2: low refractive index layer 3: hard coat layer

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Nobuko Takahashi 1-1-1 Ichigaya-Kaga-cho, Shinjuku-ku, Tokyo F-term in Dai Nippon Printing Co., Ltd. (reference) 2H091 FA37X FA37Z FB02 FB06 FC01 FC08 FC22 FC23 GA01 GA16 KA01 LA02 LA03 LA12 2K009 AA02 BB24 CC09 CC42 DD02 DD06 EE00 4F100 AA20B AA27 AH06B AK01C AK41A AK42 AR00C AT00A BA02 BA03 BA07 BA10A BA10B EH462 EJ37A EJ422 EJ522 JA07B JB14C JK06 JK12C JM01B JM10B JN00 JN01A JN02 JN06 JN18B YY00B 4G072 AA28 BB09 CC10 FF07 GG01 GG03 HH30 JJ11 LL06 MM01 NN21 PP03 RR05 UU30

Claims (8)

[Claims] 1. An SiO ₂ sol having a low refractive index layer formed directly or through another layer on the surface of a substrate film, wherein the low refractive index layer has a molecular weight of 10,000 to 100,000. An optically functional film characterized by being a SiO ₂ gel layer obtained by gelling 2. The method according to claim 1, wherein the SiO ₂ sol has the general formula R _m Si (OR ′)
_n (where R represents an alkyl group having 1 to 10 carbon atoms, a vinyl group, a (meth) acryloyl group, an epoxy group, an amide group, a sulfonyl group, a hydroxyl group, a carboxyl group or a group containing these groups, etc.) R ′ represents an alkyl group having 1 to 10 carbon atoms, m represents 0 to 3, and n represents 1 to
Represents an integer of 4 and m + n is 4. The optical functional film according to claim 1, which is a SiO ₂ sol prepared by hydrolyzing a silicon alkoxide represented by the formula (1). 3. The molecular weight is from 20,000 to 50,000.
The optical functional film according to claim 1, wherein 4. The low refractive index layer has a refractive index of 1.38 to 1.4.
The optical functional film according to any one of claims 1 to 3, which is 6. 5. The optical functional film according to claim 1, wherein the base film is a uniaxially stretched transparent polyester film. 6. The method according to claim 1, wherein the other layer is a hard coat layer.
The optical functional film according to any one of Items 1 to 5, wherein 7. An antireflection film comprising the optical functional film according to claim 1. Description: 8. A SiO ₂ sol, is applied to the surface of the hard coat layer on the surface or the base film of the base film, then gelled by heating or active energy ray irradiation treatment, SiO ₂ gel layer The method for producing an optically functional film according to any one of claims 1 to 6, wherein