JP2730185B2 - Coating composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a composition for coating a transparent resin molded product suitable for optical use such as a plastic lens. Further, the present invention provides a coating material that can suppress surface reflection of a transparent resin molded product, can be dyed with a disperse dye, and can maintain a high surface hardness.

[Summary of the Invention]

The present invention relates to a coating composition for providing a coating film having a low refractive index, a fine particle comprising magnesium fluoride, or calcium fluoride, or a mixture of magnesium fluoride and calcium fluoride, and an organic binder polymerized and cured by light. Is a composition comprising a polymerizable organic compound and photopolymerization initiator fine particles.

[Conventional technology]

Conventionally, a vacuum deposition method is generally used as an antireflection method. In addition to inorganic glass, oxide materials such as silicon oxide and zirconium oxide have been applied to plastic materials.

Japanese Patent Application Laid-Open No. 61-18901 discloses a coating composition containing a bissilane compound having a fluoroalkyl group as a component. It describes that this can be applied to plastic lenses and the like.

In addition, a method of converting the surface into a perfluoropolymer is known (functional fluorine-containing polymer, P79, Nikkan Kogyo Shimbun, published in 1980).

On the other hand, a hard coat is generally used as a method for forming a film having a high surface hardness. As an example, for example,
20968, 57-128755 and the like disclose a photopolymerizable hard coat paint, which is intended to improve chemical resistance and abrasion resistance.

[Problems to be solved by the invention]

However, a coating material suitable for antireflection of a transparent material has the following problems.

That is, among the conventional techniques, the method of forming a thin film by vacuum evaporation, which is most practically used, requires I high vacuum, and II it is difficult to uniformly coat a large area.

III Due to industrial problems, such as the high cost of equipment, it is difficult to commercialize panels and parts for low-cost optical applications.

Furthermore, the resulting coating film is an inorganic thin film having a dense structure, but is inferior in flexibility,
Insufficient adhesion to plastic substrates and the like. And it has the disadvantage that post-processing such as dyeing is also impossible.

Furthermore, the obtained molded article has a problem that the impact resistance is inferior and the advantages of plastic cannot be used.

Furthermore, magnesium fluoride and calcium fluoride are
Although it is interesting because of its low refractive index optically, it is necessary to perform coating under very high temperature conditions in vapor deposition, and when vapor deposition is performed under the conditions possible for plastic materials, the film is brittle and only poor adhesion can be achieved It was a situation.

Also, ion plating and CVD methods have been studied, but are not yet practical.

Next, a coating composition containing a fluoroalkyl-based silane compound disclosed in JP-A-61-18901 can obtain a relatively low refractive index, but is practical in terms of hardness, dyeability, and the like. Insufficient.

Also, in the method of fluorinating the surface, characteristics of hardness and dyeability cannot be obtained.

On the other hand, Japanese Unexamined Patent Publication No.
In the examples of the photopolymerizable hard coat of 57-20968 and 57-128755, improvement of chemical resistance and improvement of scratch resistance are possible, but this material has a refractive index of almost 1.5, No anti-reflection effect is obtained.

The present invention relates to a composition which has been obtained as a result of intensive studies to solve these problems and which provides a coating film having a low refractive index of 1.30 to 1.45.

[Means for solving the problem]

That is, the present invention relates to an active energy ray-curable coating composition, which comprises 10 to 70% by weight of A and 90 to 30% by weight of B in the total solid content.

Here, A is fine particles of magnesium fluoride and / or calcium fluoride having a particle size of 1 to 50 millimicrons,
B is a polymerizable organic compound and a photopolymerization initiator.

 Hereinafter, the present invention will be described in more detail.

Magnesium fluoride and calcium fluoride of component A have a refractive index in the bulk state of magnesium fluoride (Mg
F ₂ ) is 1.38 and calcium fluoride (CaF ₂ ) is as low as 1.25, which is a material suitable for obtaining a refractive index of 1.20 to 1.45 as a coating film.

Here, A is fine particles of magnesium fluoride and / or calcium fluoride having a particle size of 1 to 50 millimicrons,
B is a polymerizable organic compound and a photopolymerization initiator.

 Hereinafter, the present invention will be described in more detail.

Magnesium fluoride component A (MgF ₂₎ and calcium fluoride (CaF _2), the refractive index in the bulk state, MgF ₂ is 1.
38, CaF ₂ is as low as 1.25, as a coating film, the refractive index from 1.20
It is a suitable material for obtaining 1.45.

However, in the past, it was difficult to form fine particles and there was no sufficient dispersion, but in recent years, highly miniaturized dispersions by the gas phase method and the liquid phase method have been obtained (for example, Nihon Keizai Sangyo Shimbun) , March 31, 1987). With these triggers, there have been some developments of metal compound fine particles, and materials that can be used for both fluorides can be selected.

The size of the particles is limited because it is essential that the particles be optically transparent when the film is formed. That is, fine particles having a particle diameter of 1 to 50 millimicrons are preferable so as not to cause light scattering and to be able to mix well with the binder.

If the particle size is 50 millimicrons or more, the coating film becomes cloudy. If the particle size is 1 millimeter or less, the particle properties decrease and the properties of the polyacid become strong.

The fine particles of A are preferably prepared by using a sol dispersed in a solvent or by dispersing the fine particles in a coating solution.

Next, the polymerizable organic compound as the component B and the photopolymerization initiator will be described.

As the polymerizable organic compound, a polyfunctional monomer or prepolymer having two or more (meth) acryloyl groups in one molecule is used. Examples of these compounds include di- or meta- (meth) acrylates such as (poly) ethylene glycol, (poly) propylene glycol, hexanediol, glycerin, trimethylolpropane, etc., pentaerythritol, dipentaerythritol, sorbitol, etc. Of tri, tetra or hexa (meth) acrylate. In addition, spirane (meth) acrylate in which a polymerizable unsaturated group such as 2-hydroethyl (meth) acrylate is introduced into an unsaturated cycloacetal compound such as diarylidenepentaerythritol also improves the adhesiveness to the substrate. It is effective for In order to increase the hardness of the cured film,
It is effective to increase the number of the reactive functional groups having a large number or to use bisphenol A or di (meth) acrylate of a polyhydric alcohol in which ethylene oxide is added to a hydroquinone skeleton. In addition, in order to improve the adhesiveness, polyacrylates in which the reactive groups in the resin such as polybutadiene are acrylated are used. Silicon acrylates having an acrylic group at the end of a silicon oligomer, methylolmelamine and 2-hydroxyethyl By using melamine acrylate or the like derived from (meth) acrylate, the heat resistance and chemical resistance of the coating film can be improved. In addition, di (meth) acrylate or polyurethane acrylate of a polyester derived from a polyhydric alcohol such as ethylene glycol and a polybasic acid such as phthalic acid can also be used.

These polyhydric (meth) acrylates may be used in combination of one or more kinds, and the amount used should be 30 to 90% by weight of the total composition. That is, if it is less than 30% by weight, the hardness is not sufficient even after photopolymerization, and if it is more than 90% by weight, the refractive index is not lowered and the antireflection properties are insufficient. These polyacrylates can also be used as oligomers.

However, the amount of the polyfunctional monomer or prepolymer having two or more (meth) acryloyl groups in one molecule relative to the reactive monomer for dilution is at least 40% by weight in the total polymerizable organic compound. is necessary.
If it is less than 40% by weight, the chemical resistance and hardness are poor, which is not preferable. It is also useful to add the following reactive monomers other than these.

Examples of reactive monomers for dilution include methyl (meth) acrylate, ethyl (meth) acrylate, 2-ethylhexyl acrylate, butyl (meth) acrylate, glycidyl (meth) acrylate, (meth) acrylonitrile, hydroxyethyl (meth) acrylate, and hydroxy. Propyl (meth) acrylate, vinyl acetate, styrene, α-methylstyrene, α-chlorostyrene, (meth) acrylamide, N, N-dimethyl (meth) acrylamide vinylnaphthalene, vinylcarbazole, γ-methacryloyloxypropyltrimethoxysilane, β-acryloyloxyethyltrimethoxysilane, and the like are used. This purpose of use is necessary to lower the viscosity of the polyfunctional monomer component of the component B to improve the coating workability and to give the coating film an appropriate elasticity and adhesion when polymerized. In other words, when a composition that produces moderate elasticity and rigidity with only the polyfunctional monomer component is combined, the reaction diluting component may not be necessary, but generally, the more uniform the cured film, the more it is used in a double amount part. Is obtained. If the reaction diluent is used in an amount of 60% by weight or more of the total polymerizable organic compound, the cured film has insufficient chemical resistance and hardness.

Subsequently, the photopolymerization initiator in the B component is benzoin,
Benzoin ethers such as benzoin methyl ether and benzoin ethyl ether, benzophenone, benzophenones, acetophenones, butyroin, anthraquinone, diphenyl disulphide, benzyl dimethyl acetal, azoisobutyronitrile, etc. Mix and use more than one species. The amount used is
The curing component is suitably used in an amount of 0.01 to 5 parts by weight. If the amount is 0.01 part by weight or less, the polymerization does not sufficiently proceed, and even if 5 parts by weight or more is added, the effect is not improved. In addition, it is also effective to use a photosensitizer in combination with the photopolymerization initiator. Examples of such compounds include n-butylamine, di-n-butylamine, tri-n-butylphosphine allylthiourea, diethylaminoethyl methacrylate, triethylenetetramine, and the like.

Although the main components are as described above, it is also useful to add general additives other than these. Among them, silane materials have many advantages. That is, as the silica fine particles, colloidal silica having a particle diameter of 1 to 100 μm is commercially available, such as a solvent-dispersed silica sol of alcohol or the like, or a hydrous silica sol, and is suitable. This component is effective in imparting some rigidity and chemical resistance to the cured resin layer. The effect of this silica component is from 1% by weight to 10% in the effect coating.
It can be added in the range of weight percent. If it exceeds 10% by weight, the hardness and elasticity of the cured film become insufficient,
It is not useful because it causes cracks.

The coating composition thus obtained can be used after being diluted with a solvent, if necessary. As the solvent, alcohols, esters, ketones, and ethers are used. In addition, in order to improve defects on the coated surface, silicone surfactants, fluorine surfactants, ionic surfactants such as cations and anions, and nonionic surfactants, as well as thixotropic agents and slip agents It is also useful to add silicone oil or the like. In addition, a storage stabilizer such as benzyltrimethylammonium chloride, benzothiazole, or hydroquinone can be added to suppress thermal polymerization and stabilize the coating solution.

Some methods of applying the present invention will be described. The light source used may be a light beam of 200 to 400 nm for one second to several minutes. As the lamp, a quinocene lamp, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, or an ultra-high-pressure mercury lamp is used. The atmosphere at this time is performed in air or an inert gas.

The coating can be performed to form a cured coating film having a predetermined thickness by an immersion method, a spray method, a roll coating method, a spin coating method, a flow coating method, or the like.

Further, it is desirable that the film thickness be such that the reflection becomes the lowest, but in this case, if the design wavelength of the light is about 500 nm, it is 0.1 μm or less. When aiming for a hard coat by a coating film, it is of course possible to apply the film to a thickness of 1 to 30 μm. The ideal refractive index of the film for obtaining this anti-reflection function is as follows, assuming that the refractive indices of air and the coating film base (or cured film layer) according to the present invention are n ₀ , n ₁ and n ₂ , respectively Is the one with the least reflection.

In some cases, the treatment of the base material can be improved by adhesion cleaning by performing etching cleaning with an alkali or an acid or surface treatment with a gas plasma of oxygen, argon, or the like. As the substrate, a transparent plastic material is suitable. For example, it is effective to process inorganic glass in addition to polycarbonate, polystyrene, polyallyl carbonate, polyacryl, polyester, polyether, silicone resin, and fluorine-based optical resin.

Hereinafter, the present invention will be described in more detail with reference to examples. In addition, the part in an Example shows a weight part.

〔Example〕

Example 1 3.0 parts of pentaerythritol tetraacrylate, 2.0 parts of trimethylolpropane triacrylate, 3.0 parts of perfluoroisopropyl methacrylate, and 40 parts of magnesium fluoride sol (particle size: 10 to 20 millimicrons, solid content: 20%) dispersed in ethanol in water After mixing, ethyl acetate 50
Part of the solution, 0.1 part of benzoin methyl ether and a silicone surfactant (manufactured by Nippon Unicar Co., Ltd.
The coating film was prepared by adding 300 ppm of trade name “Y7002”). Apply this coating to CR-39 lens (trade name "Seiko Plux")
(Seiko Epson Co., Ltd.)
By rotating the lens, the excess liquid was shaken off. After air-drying this at 40 ° C for 20 minutes, using a 4KW high-pressure mercury lamp,
Both surfaces were each placed 15 cm below the light source and irradiated for 3.0 seconds. The thickness of the cured film thus obtained is about 0.1
μ, and both hardness and gloss were excellent.

<Test and results> The obtained lens is tested by the following method.
The results are shown in Table 1.

a) Refractive index: The refractive index of the coating film was measured with an ellipsometer on a coating film formed on a silicon wafer under the same conditions.

b) Anti-reflection property: The surface reflectance of one side was expressed in percent.

c) Abrasion resistance: A load of 1 kg was applied with # 0000 steel wool, the surface was rubbed for 10 reciprocations, and the degree of scratching was visually evaluated in the following stages.

A: There is no scratch on the area of 1cm x 3cm.

B: 1 to 10 scratches are made in the above range.

C: 10 to 100 scratches are made in the above range.

D: Countless scratches are present, but a smooth surface remains.

E: No smooth surface remains due to scratches on the surface.

d) Water resistance and chemical resistance: The samples were immersed in water, alcohol, and kerosene for 48 hours to examine the surface condition.

e) Acid resistance and detergent resistance: The surface state was examined by immersing in an aqueous solution of 0.1N hydrochloric acid and 1% mama lemon (manufactured by Lion Oil & Fat Co., Ltd.) for 12 hours.

f) Weather resistance: The surface condition after exposure to a sunshine weather meter using a xenon lamp for 100 hours was examined.

g) Adhesion: The adhesion between the cured film or the anti-reflection coating thin film and the lens was measured by a cross-cut tape test according to JISD-0202. That is, 100 squares of 1 mm ² are formed on the lens surface using a knife. Next, a cellophane adhesive tape (Nitto Scientific Co., Ltd. "Cellophane") was strongly applied on the surface, and then the film was rapidly peeled off from the surface in a 90-degree direction. And

h) Dyeing property: The obtained sample was immersed in a plastic lens dyeing solution (Amber, a Plux dyeing agent of Seiko Epson Corporation) at 90 ° C. for 5 minutes, and a sample having a dyeing concentration of 30% or more was evaluated as good.

Example 2 25 parts of dipentaerythritol hexaacrylate, 25 parts of pentaerythritol triacrylate, and 5 parts of tetrahydrofurfuryl acrylate were added to an acrylate ester of diarylidene pentaerythritol (trade name “Spirak T-500, manufactured by Showa Polymer Co., Ltd.). ") 30 parts, perfluorohexylethyl dimethacrylate 10 parts, butyl acetate
50 parts were added, and while mixing and stirring, 400 parts of magnesium fluoride of Example 1 and 0.3 part of a fluorinated surfactant were added to obtain a coating liquid. To this coating solution, polymethyl methacrylate was added to 1400
After injection molding at a pressure of kg / cm ² , a 75 mmφ sunglass lens whose distortion was corrected by annealing was immersed, and applied and cured in the same manner as in Example 1. This cured film is 0.5
With μ, the scratching strength was strong.

 The evaluation results are shown in Table 1 as in Example 1.

Example 3 30 parts of dipeterythritol hexaacrylate, 20 parts of dipentaerythritol pentaacrylate, 5 parts of dipentaerythritol tetraacrylate, 15 parts of perfluoroisopropyl methacrylate, 2,2-bis- (4-
Acryloyloxydiethoxyhexyl) propane 20
Parts, γ-methacryloxypropyltrimethoxysilane 15
Parts, 10 parts of isopropyl alcohol, and 30 parts of methyl acetate while mixing and stirring, and water-dispersed calcium fluoride sol (particle size: 5 to 5 parts).
Slowly add 300 parts of 10 millimicron, solid content 30%)
A homogeneous solution was obtained. Add the above-mentioned silicone surfactant
0.3 part was added to obtain a coating liquid. A high refractive index lens (trade name “Seiko High Road” non-coated lens, manufactured by Seiko Epson Corporation) is immersed in this coating solution, and the lifting speed is 30 cm.
It was applied by pulling up at / min. 20 at 40 ° C
After air-drying for 20 minutes, a 20 W low-pressure mercury lamp was used in a nitrogen atmosphere, and both sides were placed at a distance of 2 cm directly below the light source, and irradiated for 60 seconds to obtain a cured film. At this time, the film thickness was 2.5 μ, which was excellent in transparency.

 The evaluation results are shown in Table 1 as in Example 1.

Example 4 Preparation, application and curing of a coating solution were performed in the same manner as in Example 2, and instead of polymethyl methacrylate, a bisphenol A type polycarbonate resin (trade name “NOVAREX” manufactured by Mitsubishi Kasei Co., Ltd.) was injected. After molding, a lens having a high refractive index and a high impact resistance was obtained by using a 75 mmφ plano lens whose distortion was corrected by annealing. Table 1 shows the evaluation test results of the lens thus obtained.

Comparative Example 1 Table 1 shows the evaluation test results of the lens obtained in the same manner as in Example 1 except that a composition excluding the magnesium sol dispersed in aqueous methanol was used when preparing the coating film of Example 1. Shown in

Comparative Example 2 In Example 2, γ-glycidoxypropyltrimethoxysilane 12 parts, methanol-dispersed colloidal silica 19 parts, methyltrimethoxysilane 29 parts, acetic acid
After 0.1 part and 20 parts of 0.05N hydrochloric acid were mixed and reacted at 80 ° C. for 2 hours, 16 parts of ethyl cellosolve and 0.3 part of ammonium chloride were added to prepare a coating solution. This coating liquid was used and cured in the same manner as in Example 2 except that the coating liquid was cured at 100 ° C. for 1 hour. The results of the evaluation test are shown in Table 1.

Comparative Example 3 In Example 1, instead of forming a cured film by coating, an inorganic hard coat layer made of SiO ₂ was provided at 1 μm to produce a lens. Table 1 shows the evaluation results.

[Action] The coating composition uses magnesium fluoride (refractive index: 1.25) having a low refractive index per se, and as a binder component, a polymerizable organic compound capable of reacting and acting with these inorganic particles to form a strong hard film. As a result, a film obtained by coating and curing forms a uniform, strong film having a low refractive index. Therefore, surface reflection (gamma) is the Fresnel equations (1), r = (n 1 2 -n 0 n 3) 2 / (n 1 2 + n 0 n 3) 2 ...... (1) (where Where n ₀ is the refractive index of air, n ₁ is the refractive index of the base material, and n ₃ is the refractive index of the present coating film.) The above minimum value can be obtained when the film thickness is an odd multiple of 1/4. . Ideally, for example, the refractive index
For a 1.6 substrate, a quarter of a thin film with a refractive index of 1.26
The light reflection of a wavelength having a film thickness that is an odd multiple of the above becomes zero. By such an effect, the present coating composition can make use of the effect of reducing reflection. That is, in the present invention, the refractive index of the coating film can be selected from 1.30 to 1.45, and the reflection is suppressed to 0.2 to 3%.

〔The invention's effect〕

The effect of the present invention is as a plastic lens material,
Applied to resins with various functions, such as (meth) acrylic resin, styrene resin, carbonate resin, allyl resin, allyl carbonate resin, vinyl resin, polyester resin, polyether resin, and new monomer and comonomer polymers. can get. That is, it is possible to obtain an antireflection functional thin film that can be dyed, can be manufactured in a large area at low cost, and has excellent scratch resistance and good adhesion. Therefore, it can be widely applied to consumer or industrial use as an optical lens such as a spectacle lens, a camera lens, a light beam, a condenser lens, and a light diffusion lens. Further, the effect of the present invention can be applied to transparent glass such as watch glass and cover glass for displays, and transparent plastics for optical use such as cover glass, and the obtained effect is enormous.

Claims (3)

(57) [Claims] 1. An active energy ray-curable coating composition, wherein A is 10 to 70% by weight in the total solid content.
B. A coating composition comprising 90 to 30% by weight. A, Fine particles of magnesium fluoride and / or calcium fluoride having a particle size of 1 to 50 mm. B, a polymerizable organic compound and a photopolymerization initiator. 2. The polymerizable organic compound according to claim 2, wherein at least 40% by weight of the polymerizable organic compound comprises a polyfunctional monomer or prepolymer having two or more (meth) acryloyl groups in one molecule. The coating composition of claim 1. 3. The coating composition according to claim 1, wherein a refractive index of a coating film obtained from the coating composition is from 1.30 to 1.45.