JPH09203801A - Optical thin film and antireflection article using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical thin film which is easily predicable, has excellent flawing resistance and has an antireflection property and an antireflective article formed by using the film. SOLUTION: This thin film is formed by curing a compsn. consisting essentially of the compd. expressed by the general formula A<1> -O(CH2 )n -RF-(CH2 )n O-A<2> , (where A<1> , A<2> are selected from an acryloyl group, methacryloyl group, α- fluoroalkyl group, trifluoromethacryloyl group and vinyl group, Rf is perfluoroalkyl group, (n) is an integer from 0 to 3) and the refractive index in D rays is <=1.45. This antireflective article is constituted by applying the optical thin film described above on a base material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical thin film having excellent scratch resistance and an antireflection article using the same, and particularly to an antireflection film for a cathode ray tube of a television or a liquid crystal display device, and an antireflection film for a CRT monitor. Not only for anti-reflection of various display devices such as filters, but also for optical thin film and anti-reflection property that are suitable for anti-reflection of cases, show windows, picture frames, window glass, optical lenses, eyeglass lenses, etc. Regarding goods.

[0002]

2. Description of the Related Art An antireflection article such as an antireflection filter used for a display device or the like has a low refractive index optical thin film provided on a substrate in a single layer, or a high refractive index and low refractive index optical thin film. In many cases, the anti-reflection layer is formed by alternately providing multiple layers.

A method for obtaining such an optical thin film is as follows.
In general, an inorganic substance is laminated on a substrate by vapor deposition, sputtering, or the like, and the antireflection film thus obtained has low reflection and excellent scratch resistance. However, in the method of performing antireflection treatment by vapor deposition or sputtering of an inorganic substance, although a high-performance antireflection layer can be obtained, productivity is poor because a large-scale apparatus requiring vacuum is used, and the production cost is high.
Further, in these methods, the substrate is heated to 80 ° C. or more during vapor deposition or sputtering, so that the usable substrates are limited in terms of heat resistance and the like.

Recently, there has been known a method of dissolving a low-refractive-index organic substance in a solvent, coating the substrate with a low-refractive-index organic substance to form a low-refractive-index organic thin film to form an antireflection film. It became so. Such a solution coating method is disclosed, for example, in JP-A-4-355401 and JP-A-6-355601.
No. -18705. The low refractive index material used in these solution coating methods is a resin having a high fluorine content having a lower refractive index than the magnesium fluoride thin film having the lowest refractive index among inorganic thin films, and exhibits excellent antireflection properties. In addition, since these form a thin film by solution coating, it is possible to form an anti-reflection film with high productivity, unlike the method of performing anti-reflection treatment by vapor deposition or sputtering of an inorganic substance.

However, the organic thin film made of a fluorine-containing resin described in JP-A-4-355401 or JP-A-6-18705 has a high productivity because it can be solution-coated, and has an excellent reflection due to a low refractive index. Although they exhibit prevention properties, these cured fluorine-containing resins have low cross-linking densities and thus have low surface hardness and poor abrasion resistance. Furthermore, since heat curing is required after coating, usable substrates are limited in terms of heat resistance and the like.

As a fluorine-containing resin having a high surface hardness and a high crosslinking density, a cured product of perfluorodivinyl ether disclosed in US Pat. No. 3,310,606 is mentioned. An optical thin film cannot be obtained because it is insoluble in a solvent and must be molded under high temperature and high pressure.

Further, in Japanese Patent Application Laid-Open No. 8-239430, a repellent containing 10 to 90 parts by weight of a polyfunctional (meth) acrylate based on 100 parts by weight of the fluorine-containing di (meth) acrylate represented by the general formula in the present invention. Disclosed is a fluorine-containing curable composition having water / oil repellency and scratch resistance. However, in the technique described in JP-A-8-239430, the blending amount of polyfunctional (meth) acrylate is too large, and the refractive index at D line tends to exceed 1.45. There is a problem that it is difficult to obtain prevention performance.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides an antireflection optical thin film having low reflectance and excellent scratch resistance and capable of easily obtaining an optical thin film, and an antireflection article using the same. The purpose is to

[0009]

The present invention has the following constitution in order to achieve the above object.

"(1) General formula A ¹ -O (CH ₂ ) _n -Rf
_{- (CH 2) n O-} A 2 ( wherein A ^1, A ² is an acryloyl group, a methacryloyl group, alpha-fluoro acryloyl group, selected from trifluoromethyl methacryloyloxy group and vinyl group, Rf is a perfluoroalkyl group , N is an integer of 0 to 3), which is obtained by curing a composition containing a compound represented by the formula as a main component, and has a refractive index at D line of 1.45 or less.

(2) An antireflection article, characterized in that the substrate is coated with the optical thin film described in (1) above. "

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the optical thin film means a thin film in which, when a light beam is incident on a base material having a thin film above, the light beam crosses at a boundary having a different refractive index to cause interference. In an optical thin film, reflected light appears as interference light of incident light.
For example, when a transparent optical thin film is provided on a transparent substrate, part of the incident reflected light is reflected at the boundary between air and the thin film,
Part of the light is reflected by the boundary surface between the thin film and the substrate, and the reflected light becomes interference light between them as a whole. The interference light results in a reduction or increase in the reflectivity of the substrate. The optical thin film is thin enough to cause interference of light, and the reflectance of the substrate depends on the refractive index and the thickness of the optical thin film.

The present invention provides an optical thin film having a low refractive index for the purpose of reducing the reflectance, and the thickness of the optical thin film is preferably an odd multiple of λ / 4. Here, λ indicates the wavelength of the light in the thin film, and when the wavelength of the light exists in a certain width, λ indicates the central wavelength of the light. In many cases, the wavelength of the light of interest in the present invention is visible light, and the center wavelength is preferably set to 500 to 550 nm, which is usually sensitive to humans.

The thickness of the optical thin film of the present invention depends on the refractive index of the thin film, but is preferably 30 to 700 nm, more preferably 40 to 120 nm. Optical thin film thickness is 3
If the thickness is less than 0 nm, the reflectance may not be sufficiently reduced due to optical interference with visible light. Also, when the film thickness of the optical thin film exceeds 700 nm, the reflectance almost depends only on the reflection at the interface between air and the thin film, so that the reduction of the reflectance due to the light interference in visible light tends to be insufficient.

When a low-refractive index film is provided on the surface of an article thicker than the optical film thickness to provide antireflection, there is no effect of reducing the reflectivity due to light interference, and the reflection due to the low refractive index of the substrate surface. Since only the reduction of the reflectance is achieved, the reflectance is higher and the antireflection effect is inferior as compared with the case where the optical thin film is provided.
For example, when a thin film having a refractive index of 1.38 is provided on a substrate having a refractive index of 1.6, the reflectance is 1 when the film thickness is an optimal optical film thickness.
% Or less, but when the film thickness is several μ or more, the reflectance is about 3%. The optical thin film has a refractive index of 1.45.
If higher than, polymethylmethacrylate (hereinafter,
The antireflection treatment effect on a substrate having a relatively low refractive index such as PMMA) or glass is not significantly recognized.

In the optical thin film of the present invention, the surface hardness after curing is preferably pencil hardness H or more. This is because when the surface hardness is low, the scratch resistance is poor and the durability is low.

In the present invention, the general formula A ¹ -O (CH ₂ ) _{n
-Rf- (CH 2) n O-} A compound represented by ² is used. Here, A ¹ and A ² are selected from an acryloyl group, a methacryloyl group, an α-fluoroacryloyl group, a trifluoromethacryloyl group, and a vinyl group, preferably an acryloyl group and a methacryloyl group.
Rf is a perfluoroalkyl group, and (C
F ₂ ) m (m is an integer of 2 or more, more preferably 4 to 16)
Is preferably an integer). Furthermore, n is an integer of 0-3.

Examples of the fluorine-containing compound having two such unsaturated double bonds include the following compounds.

[0019]

Embedded image In addition to the above-mentioned fluorine-containing compound having two unsaturated double bonds, in the present invention, for the purpose of adjusting hardness, adhesion with upper and lower layers, adjustment of refractive index and performance improvement, Other polyfunctional monomers may be used as the fluorine-containing compound 100 of the present invention.
It is contained in an amount of less than 10 parts by weight, preferably 9 parts by weight or less, based on parts by weight. When the polyfunctional monomer contains 10 parts by weight or more,
The refractive index at the D line exceeds 1.45, and the antireflection performance targeted by the present invention cannot be obtained.

Examples of other polyfunctional monomers included in the present invention include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate,
Neopentyl glycol di (meth) acrylate, 1,
6-hexanediol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol penta (meth) ) Acrylate, dipentaerythritol tetra (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, 1,1,1-tris [(meth) acryloyloxyethoxyethoxy]
Examples include propane, tris (hydroxyethyl) isocyanurate tri (meth) acrylate, and tris (hydroxyethyl) isocyanurate di (meth) acrylate. Among these polyfunctional monomers, trifunctional or higher (meth) acrylates added for the purpose of improving the hardness of the optical thin film are particularly preferably used in the present invention. used.

In addition to the above, a compound containing one unsaturated double bond (monofunctional monomer) and a polymerization initiator can be added to the composition, if necessary. These monomers and compounds are appropriately added for adjustment of hardness, refractive index, coating property, and the like, and can be cured to form an optical thin film.

Examples of such a fluorine-containing monofunctional monomer containing one unsaturated double bond include, for example, 2,2,2-trifluoroethyl methacrylate, 2,2,3,3-tetrafluoropropyl methacrylate and 2 , 2, 3, 4,
4,4-hexafluorobutyl methacrylate, 1H, 1
H, 3H, 2H-perfurodecanol acrylate, β
-(Perfluorooctyl) ethylmethacrylate etc. are mentioned. In order to lower the refractive index of the optical thin film, it is preferable to add a compound having a high fluorine content containing one unsaturated double bond. Further, the hardness of the optical thin film can be increased by adding a small amount of a difluorovinyl compound.

Further, examples of monofunctional monomers containing no fluorine include methyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl ( Examples thereof include (meth) acrylate, but there is no limitation as long as the compatibility is good and a cured product having a refractive index of 1.45 or less can be obtained.

A leveling agent may be added in order to further improve the coating property, and the addition amount is preferably 0.05 to 5% by weight, more preferably 0.1 to 5% by weight based on the whole cured product.
2% by weight.

In the optical thin film of the present invention, a curing method such as a thermal polymerization method, an electron beam polymerization method or a photopolymerization method (UV polymerization method) is not particularly limited, but preferably, the light is not affected by the heat resistance of the substrate. It is cured by a polymerization method. Examples of the photopolymerization initiator include 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholino. Examples include propanone-1 and the like, but are not particularly limited. The amount of the photopolymerization initiator added is 0.1 to 20% by weight, preferably 0.1 to 10% by weight, based on the entire cured product composition.

In the present invention, a polyfunctional monomer, a polymerization initiator,
A composition containing a monofunctional monomer, a leveling agent or the like is applied as it is or after being diluted with a suitable solvent and applied on a substrate,
Antireflection property can be imparted. The application method is
The method is not particularly limited as long as it can be uniformly applied to the substrate,
For example, spin coat, dip coat, die coat,
Examples of application methods include spray coating, bar coater coating, roll coating, and curtain flow coating.

The composition to be the optical thin film of the present invention can be preferably applied uniformly to the optical film thickness and then cured by ultraviolet irradiation using a low pressure or high pressure mercury lamp, a xenon lamp or the like. The substrate provided with antireflection properties by the optical thin film of the present invention is not particularly limited, but for example, ordinary glass, thin glass having a thickness of 1 mm or less, resin transparent substrate such as acrylic resin such as polycarbonate and PMMA, polyethylene terephthalate film. Films and the like.

When the optical thin film of the present invention is formed on a substrate, the substrate may be surface-treated or an intermediate layer may be provided, if necessary, for the purpose of improving the adhesiveness or coating property. it can. When an optical thin film having a high refractive index is used for the intermediate film, the antireflection effect is enhanced.Furthermore, by alternately stacking a large number of the high refractive index thin films and the optical thin film of the present invention, a more excellent antireflection film is obtained. be able to. In order to enhance the antireflection effect, the high refractive index film needs to have a refractive index equal to or higher than that of the substrate, and the refractive index is preferably 1.58 or more, more preferably 1. It is 6 or more, and more preferably 1.7 or more.

Further, the optical thin film of the present invention has a water repellent effect due to the effect of elemental fluorine in addition to the antireflection property, and when the optical thin film of the present invention is applied to a porous substrate such as silicon oxide, only low reflectivity is obtained. However, water repellency can be imparted.

[0030]

EXAMPLES The present invention will be specifically described with reference to examples, but the invention is not limited thereto. Example 1 Fluorine-containing diacrylate below _{CH 2 = CH-COO-CH} 2 (CF 2) 8 CH 2 -O
CO-CH = CH ₂ 10 parts by weight, as a photoinitiator 2-hydroxy-2-methyl-0.4 parts by weight,
180 parts by weight of isopropyl alcohol were mixed and stirred to prepare a coating liquid. The coating solution was applied to a polycarbonate substrate which was hard-coated by dip coating to give a film thickness of 10
After coating to 0 nm, 3 using a high pressure mercury lamp
It was cured by irradiating with 5000 mJ / cm ² UV for a minute.

Table 1 shows the reflectance of the optical thin film substrate at 540 nm, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

The obtained optical thin film substrate had low reflection and excellent scratch resistance.

The resistance of the thin film to the poppy rubber is LION,
No. 50 eraser was used to observe and evaluate the occurrence of scratches after reciprocating 5 times under a load of 1 kg.

Example 2 The following fluorine-containing diacrylate CH ₂ = CH-COO-CH ₂ (CF ₂ ) ₈ CH ₂ -O
CO-CH = CH ₂ 80 and the parts, IH, IH, 3H, 2H-Perfluoro octadecanol acrylate 15 parts by weight of trimethylolpropane triacrylate, 5 parts by weight of isobutyl alcohol 9
00 parts by weight and 1 part by weight of 1-hydroxycyclohexyl phenyl ketone as an initiator were mixed and stirred to prepare a coating liquid. A coating solution was applied onto a hard-coated polycarbonate substrate by a spin coating method so as to have a film thickness of 100 nm, and then 50 minutes in 3 minutes using a high pressure mercury lamp.
It was irradiated with 00 mJ / cm ² UV and cured.

Table 1 shows the reflectance at 540 nm of the optical thin film substrate, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

The obtained optical thin film substrate had low reflection and excellent scratch resistance.

Example 3 The following fluorine-containing diacrylate CH ₂ = CH-COO-CH ₂ (CF ₂ ) ₁₀ CH ₂ -O
CO-CH = CH ₂ 42 parts by weight of pentaerythritol triacrylate 3
Parts by weight, and 2-methyl-1- [4- as a photoinitiator
(Methylthio) phenyl] -2-morpholinopropanone-1 (1 part by weight), and SH19 as a leveling agent.
0 (manufactured by Toray Tau Corning Silicone) was mixed with 0.3 part by weight, and 450 parts by weight of acetic acid-n-butyl as a solvent were mixed,
The coating liquid was prepared by stirring. A hard coat having a thickness of 150 nm and made of a mixture of antimony oxide sol and pentaerythritol triacrylate is formed on a polycarbonate substrate, and a hard coat having a refractive index of 1.7 is formed on the polycarbonate substrate. After applying so that it becomes 5000 m in 3 minutes using a high pressure mercury lamp.
J / cm ² UV irradiation was carried out to cure, and a two-layer film of a high refractive index thin film and a low refractive index thin film was provided on a polycarbonate substrate.

Table 1 shows the reflectance at 540 nm of the optical thin film substrate, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

The obtained optical thin film substrate had low reflection and excellent scratch resistance.

Example 4 An optical thin film substrate was prepared in the same manner as in Example 1 except that PMMA was used as the coating material coated substrate.

Table 1 shows the reflectance at 540 nm of the optical thin film substrate, the pencil hardness of the cured product, the refractive index at D line, and the poppy rubber resistance of the thin film.

The obtained optical thin film substrate had low reflection and excellent scratch resistance.

Example 5 The following fluorine-containing diacrylate CH ₂ ═CH—COO—CH ₂ (CF ₂ ) ₁₀ CH ₂ —O
CO-CH = CH ₂ 93 parts by weight of pentaerythritol triacrylate 7
By weight, 850 parts by weight of isopropyl alcohol and 1 part by weight of 1-hydroxycyclohexyl phenyl ketone as an initiator were mixed and stirred to prepare a coating liquid. A coating solution was applied onto a hard-coated polycarbonate substrate by a spin coating method so as to have a film thickness of 100 nm, and then 5000 mJ / cm ² for 3 minutes using a high pressure mercury lamp.
It was irradiated with UV and cured.

Table 1 shows the reflectance at 540 nm of the optical thin film substrate, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

The obtained optical thin film substrate had low reflection and excellent scratch resistance.

Comparative Example 1 5 parts of neopentyl glycol diacrylate, 0.4 part of 2-hydroxy-2-methyl-1-phenylpropan-1-one as a photoinitiator, 9 parts of isopropyl alcohol
0 parts were mixed and stirred to prepare a coating solution. The coating solution was applied to a hard-coated polycarbonate substrate by a dip coating method so as to have a film thickness of 100 nm, and then 5000 mJ / cm ² UV was applied for 3 minutes using a high pressure mercury lamp.
Irradiated and cured.

Table 1 shows the reflectance at 540 nm of the optical thin film substrate, the pencil hardness of the cured product, the refractive index at D line, and the poppy rubber resistance of the thin film.

The antireflection effect of the obtained thin film was low.

Comparative Example 2 A thin film was formed on a PMMA substrate in the same manner as in Comparative Example 1 except that PMMA was used as the substrate.

Table 1 shows the reflectance at 540 nm, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

The antireflection effect of the obtained thin film was low.

Comparative Example 3 The following chemical formula

Embedded image A 2% solution of a commercially available fluorine-containing resin (manufactured by Asahi Glass Co., Ltd., Cytop) represented by the following formula is applied to a hard-coated polycarbonate substrate by a dip coating method so as to have a film thickness of 100 nm. After drying for an hour, an optical thin film was obtained.

Table 1 shows the reflectance at 540 nm, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

It became a soft cured product and was damaged by poppy rubber.

Comparative Example 4 The following chemical formula

Embedded image Commercially available fluorine-containing resin (Mitsubishi Rayon Co., Ltd.)
3% solution obtained by dissolving 3 parts by weight of FM17) in 97 parts by weight of perfluoro-2-butyltetrahydrofuran was applied to a hard-coated polycarbonate substrate with a film thickness of 1%.
After applying by the dip coating method to become 00 nm,
After drying at 80 ° C. for 1 hour, an optical thin film was obtained.

Table 1 shows the reflectance at 540 nm, the pencil hardness of the cured product, the refractive index at the D line, and the poppy rubber resistance of the thin film.

A soft cured product was obtained and scratches were generated by the poppy rubber.

[0058]

[Table 1]

[0059]

According to the present invention, it is possible to provide an antireflection optical thin film which is excellent in abrasion resistance, weather resistance and heat resistance and which is easy to apply.

Further, an antireflection article using the optical thin film of the present invention is an antireflection film for televisions such as a cathode ray tube or a liquid crystal display device, an antireflection filter for a CRT monitor or the like, and an exhibit. It can be suitably used as a case, show window, picture frame, window glass, optical lens, eyeglass lens, and the like.

Claims (10)

[Claims] 1. A general formula A ¹ -O (CH ₂ ) _n -Rf- (C
H ₂ ) _n O-A ² (wherein A ¹ and A ² are selected from an acryloyl group, a methacryloyl group, an α-fluoroacryloyl group, a trifluoromethacryloyl group and a vinyl group, and Rf is a perfluoroalkyl group, n Is an integer of 0 to 3), which is obtained by curing a composition containing a compound represented by the formula as a main component, and has a refractive index at D line of 1.45 or less. 2. The optical thin film according to claim 1, which has a film thickness of 30 to 700 nm. 3. In the general formula, Rf is (CF ₂ )
_{The method according} to claim 1, wherein m is _m (m is an integer of 2 or more).
Alternatively, the optical thin film described in 2. 4. In the general formula, Rf is (CF ₂ )
_{It is m} (m is an integer greater than or equal to 6), The optical thin film in any one of Claims 1-3 characterized by the above-mentioned. 5. The optical thin film according to claim ¹ , wherein A ¹ and A ² in the general formula are acryloyl groups. 6. The optical thin film according to claim ¹ , wherein A ¹ and A ² in the general formula are methacryloyl groups. 7. The optical element according to claim 1, which contains less than 10 parts by weight of a polyfunctional (meth) acrylate with respect to 100 parts by weight of the compound represented by the general formula. Thin film. 8. The optical thin film according to claim 1, which is cured by light. 9. An antireflective article, characterized in that the substrate is coated with the optical thin film according to any one of claims 1 to 8. 10. The antireflection article according to claim 9, wherein the optical thin film is applied to a base material provided with a film having a refractive index of 1.58 or more.