JPH036265A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain a coating composition which gives a film having a refractive index as low as 1.30 to 1.45 by mixing fine particles of magnesium fluoride or calcium fluoride, a polymerizable organic compound, and a photopolymerization initiator as solid matter of a coating film. CONSTITUTION:A coating composition curable by actinic radiation, which consists of 10-70wt.% fine particles (A) of magnesium fluoride and/or calcium fluoride, having a particle diameter of 1-50mum, and 90-30wt.% component (B) consisting of a polymerizable organic compound and a photopolymerization initiator. It is necessary that at least 40wt.% of said polymerizable organic compound comprises a polyfundtional monomer or prepolymer having at least two (meth)acryloyl groups in the molecule. The coating composition thus obtained gives a transparent resin molding with low surface reflectance, can be dyed with a disperse dye, and can retain high surface hardness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a composition for coating transparent resin molded products suitable for optical applications such as plastic lenses. Furthermore, it is an object of the present invention to provide a coating material that can suppress the surface reflection of a transparent resin molded product, can be dyed with a disperse dye, and can maintain high surface hardness.

[Summary of the invention]

The present invention is a coating composition for providing a coating film with a low refractive index, comprising fine particles of magnesium fluoride, calcium fluoride, or a mixture of magnesium fluoride and calcium fluoride, and an organic binder that is polymerized and cured by light. It is a composition consisting of a polymerizable organic compound and photopolymerization initiator fine particles.

[Conventional technology]

Vacuum deposition has conventionally been a common method for antireflection, and has been applied not only to inorganic glasses but also to oxide materials such as silicon oxide and zirconium oxide, and to plastic materials.

Further, JP-A-61-18901 discloses a coating composition containing a bikusilane compound having a fluoroalkyl group as a component. It is stated that this can be applied to plastic lenses, etc.

Furthermore, a method of perfluoropolymerizing the surface is known (Functional Dental Fluorescent Polymer, P79, Nikkan Kogyo Shimbun, published in 1980).

On the other hand, as an example of a common method of forming a film with high surface hardness by hard coating, for example, JP-A-57-
No. 20968, No. 57-128755, etc., disclose photopolymerizable hard coat paints, which are intended to improve chemical resistance and scratch resistance.

[Problem to be solved by the invention]

However, coating materials suitable for antireflection of transparent materials have the following problems.

That is, among the conventional techniques, the method of forming a thin film by vacuum evaporation, which is the most widely used method, has the following drawbacks: (1) High vacuum is required; and (1) It is difficult to uniformly coat a large area.

Due to industrial problems such as the high cost of equipment, it is difficult to put it into practical use in panels and low-cost optical parts.

Furthermore, although the resulting coating film is an inorganic thin film with a dense structure, it has poor flexibility and insufficient adhesion to plastic substrates and the like. and,
It has the disadvantage that post-processing such as dyeing is not possible.

Furthermore, the resulting molded article has poor impact resistance, and there is also the problem that the advantages of plastic cannot be utilized.

Furthermore, although magnesium fluoride and calcium fluoride are interesting because they have a low optical refractive index, they must be coated under extremely high temperature conditions during vapor deposition, and if they are vapor deposited under conditions that are possible on plastic materials, the film will not form. The situation was such that only products that were brittle and had insufficient adhesion could be produced.

Further, although ion brating and CVD methods are being studied, they are not yet practical.

Next, although the coating composition containing a fluoroalkyl silane compound disclosed in JP-A No. 61-18901 can obtain a relatively low refractive index, it has a high hardness and
Practically unsatisfactory in terms of dyeability, etc.

Further, even in the method of fluorinating the surface, properties such as hardness and dyeability cannot be obtained.

On the other hand, JP-A No. 5, which is disclosed as a film with high surface hardness,
7-20968 and 57-128755, it is possible to improve chemical resistance and scratch resistance, but most of these materials have a refractive index of 1.
．． 5, and no anti-reflection effect can be obtained.

The present invention was achieved as a result of intensive studies to solve these problems, and has a refractive index of 1.30 to 1.45.
The invention relates to a composition that provides a coating film with a low refractive index.

[Means to solve the problem]

That is, the present invention is an active energy ray-curable coating composition characterized in that A is 10 to 70% by weight and B is 90 to 30% by weight based on the total solid content. .

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

The present invention will be explained in more detail below.

Component A, magnesium fluoride and calcium fluoride, has a refractive index in the bulk state of magnesium fluoride (Mg
Fa) is 1.38, calcium fluoride (CaF2)
The refractive index is as low as 1.25, and as a coating film, the refractive index is 1.20 to 1.
, 45.

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

The present invention will be explained in more detail below.

Component A, magnesium fluoride (MgF2) and calcium fluoride (CaFp), has a refractive index in the bulk state of M
It has a low g F t of 1□38 and a low CaF2 of 1.25, making it a material suitable for obtaining a coating film with a refractive index of 1.20 to 1°45.

However, in the past, it was difficult to make fine particles and there was no sufficient dispersion, but in recent years it has become possible to obtain highly fine dispersions using gas phase and liquid phase methods (for example, Nihon Keizai Shimbun , March 31, 1986 edition), these developments have led to the development of several metal compound fine particles, and materials that can be used with both fluorides can be selected.

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

If the particle size is 50 millimicrons or more, the coating film becomes cloudy, and if it is less than 1 millimicron, the particle size decreases and the polyacid properties become strong, resulting in insufficient strength of the obtained film, which is not suitable.

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 liquid.

Next, the polymerizable organic compound and photopolymerization initiator, which are component B, will be explained.

Polymerizable organic compounds are two or more (meta) molecules in one molecule.
A polyfunctional monomer or prepolymer having an acryloyl group is used. Examples of these compounds include di- or tri(meth)acrylates such as (poly)ethylene glycol, (poly)propylene glycol, hexanediol, glycerin, trimedylolpropane, pentaerythritol, dipentaerythritol, sorbitol, Examples include tri, tetra, or hexa(meth)acrylates such as. In addition, spiran (meth)acrylate, which is obtained by adding a polymerizable unsaturated group such as 2-hydroethyl (meth)acrylate to an unsaturated cycloacecool compound such as diarylidenepentaerythritol, also has good adhesion to the substrate. It is effective for improving To increase the hardness of the cured film,
It is effective to increase the number of the above-mentioned reactive functional groups, or to use di(meth)acrylate of a polyhydric alcohol with ethylene oxide added to bisphenol A or hydroquinone skeleton. In addition, in order to improve adhesiveness, polyvalent acrylates such as polybutadiene, which are made by acrylating reactive groups in resins, are used, silicone acrylates with acrylic groups at the terminals of silicone oligomers, methylolmelamine and 2-hydroxyethyl (meta)
Melamine acrylate derived from acrylate can be used to improve the heat resistance and chemical resistance of the coating film. In addition, polyester di(
Meta)acrylates and polyurethane acrylates can also be used.

It is best to use one or more of these polyvalent (meth)acrylates in combination, and the amount of m used is 30 to 90% of the total composition.
It is necessary to have a heavy plate percentage. i.e. 30
If it is less than the heavy plate percentage, the hardness will not be sufficient even after photopolymerization,
If the ratio is more than 90%, the refractive index will not be lowered and the antireflection properties will be insufficient. Moreover, these polyvalent acrylates can also be used as oligomers.

However, with respect to these reactive monomers for dilution, one of the polyfunctional monomers or prepolymers having two or more (meth)acryloyl groups in one molecule accounts for at least 40 percent of the total polymerizable organic compounds. is necessary.

If it is less than 40 fifi percent, the chemical resistance and hardness will be poor and it is not preferable, and it is 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, and hydroxyethyl (meth)acrylate. , hydroxypropyl (meth)acrylate, vinyl acetate, styrene, α-methylstyrene, α-chlorostyrene, (meth)acrylamide, N, N-dimethyl (meth)acrylamide vinylnaphthalene, vinylcarbazole, γ-methacryloyloxypropyltrimethoxy Silane, β-acryloyloxyethyltrimethoxysilane, etc. are used. This purpose is necessary to lower the viscosity of the polyfunctional monomer component of component B and improve coating workability, and to impart appropriate elasticity and adhesion to the coating film when polymerized. In other words, when combining a composition that produces appropriate elasticity and stiffness with only the polyfunctional 7-mer component, this reaction diluent component may be omitted, but generally it is better to use 1 part or more of the 7-mer component to achieve a homogeneous result. A cured film is obtained. Furthermore, if this reaction diluent component is used in an amount of 60% or more based on the total polymerizable organic compounds, the chemical resistance and hardness of the cured film will be insufficient.

Subsequently, the photopolymerization initiator in component B is benzoin, benzoin ethers and benzophenone, such as benzoin methyl ether, benzoin ethyl ether, benzophenones, acetophenones, butyroin, anthraquinone, diphenyl disulfide, and benzyl dimethyl. Acetals, azoisobutyronitrile, etc. may be used alone or in combination of two or more. The appropriate amount to use is 0.01 to 5 parts by weight of the curing component; if the amount is less than 0°O, polymerization will not proceed sufficiently, and if more than 5 parts by weight is added, the effect will not improve. In conjunction with the 1st initiator,
It is also effective to use a photosensitizer together. Examples of such compounds include n-butylamine, di-n-butylamine, tri-n-butylphosphine allylthiourea, diethylaminoethyl methacrylate triethylenetetramine, and the like.

The main ingredients are listed above, but it is also useful to add general additive ingredients in addition to these. Among them, silane materials have a number of advantages, namely, as fine silica particles, colloidal silica with a particle size of 1 to 100 μm is commercially available as solvent-dispersed silica sol such as alcohol, hydrous acid silica sol, etc., and is suitable. The components are effective in imparting some stiffness and chemical resistance to the cured resin layer. The effect of this silica component is 1fflJ! in the cured film! It can be added in a range of 1% to 10% by weight.

If it exceeds 10% by weight, the hardness and elasticity of the cured film will be insufficient and cracks will occur, so it is not useful.

The film composition obtained in this way may be
It can be used after being diluted with a solvent. 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 cationic and anionic surfactants, nonionic surfactants, chicken tropic agents, slip agents, etc. It is also useful to add silicone oil or the like. In addition,
In order to suppress thermal polymerization and stabilize the coating solution, a storage stabilizer such as benzyltrimethylammonium chloride, benzothiazole, or hydroquinone can be added.

Some details will be given on how to apply and implement the present invention. The light source to be used may irradiate a light beam of 200 to 400 nm for one second to several minutes, and the lamp used may be a xenon lamp, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, or an ultra-high-pressure mercury lamp. The cloud enclosure at this time is performed in air or in an inert gas.

Application methods include dipping, spraying, roll coating,
A cured coating film of a predetermined thickness can be produced by a spin code method, a flow coat method, or the like.

Further, it is desirable that the film thickness has the lowest reflection, but in that case, if the design wavelength of light is about 500 nm, it will be 0.1 μm or less. When aiming at a hard coat using a coating film, it is of course possible to apply the coating to a thickness of 1 to 30 μm. The ideal refractive index of the film for this anti-reflection function is nil n+, nil n+,
When ``t'' is nl2f'r]i, there is the least reflection.

In addition, adhesion can sometimes be improved by etching cleaning with alkali or acid or surface treatment with gas plasma such as oxygen or argon, and it is preferable to select the appropriate treatment for the base material. Examples of suitable transparent plastic materials include polycarbonate, polystyrene, polyallyl carbonate,
In addition to polyacrylic, polyester, polyether, silicone resin, fluorine-based optical resin, etc., processing into inorganic glasses is also effective.

Hereinafter, it will be explained in more detail with reference to Examples. In addition, parts in Examples indicate parts by weight.

〔Example〕

Example 1 3.0 parts of pentaerythritol tetraacrylate, 2.0 parts of trimethylolpropane triacrylate, 3.0 parts of perfluoroisopropyl methacrylate, ethanol water-dispersed magnesium fluoride sol (particle size 10-20
After mixing 40 parts of millimicrons (solid content 20%),
A coating solution was prepared by adding 0.1 part of benzoin methyl ether and 300 ppm of a silicone surfactant (manufactured by Nippon Unicar, trade name: rY7002J) to a solution containing 50 parts of ethyl acetate. Apply this coating liquid to the CR-39 lens (product name °° Seiko Blacks” Seiko Epson @￥g
1) was applied, and the lens was rotated at 3000 revolutions per minute to shake off the remaining liquid. This is 406C for 20
After air-drying for a minute, both surfaces were placed 15 cm directly below the light source and irradiated for 3.0 seconds using a 4KW high-pressure mercury lamp. The thickness of the cured film thus obtained was approximately 0. 1μ
It had excellent hardness and gloss.

Tests and Results The obtained lenses were tested in the following manner, and the results are shown in Table 1.

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

b) Antireflection properties: The surface reflectance of one side is expressed as a percentage.

C) Abrasion resistance: 1kg with #0000 steel wool
The surface was rubbed 10 times with a load of

A: There was no damage at all within a 1cm x 3cm area.

B: 1 to 10 scratches within the above range.

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

D = Countless scratches, but a smooth surface remains.

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

d) Water resistance/chemical resistance: The surface condition was examined by immersing it in water, alcohol, and kerosene for 48 hours.

e) Acid/detergent resistance: 0. It was immersed in an aqueous solution of IN hydrochloric acid and 1% Mama Lemon (manufactured by Lion Oil and Fat Field) for 12 hours, and the surface condition was examined.

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

g) Adhesion: The adhesion between the cured film or the antireflection coat thin film and the lens was determined by a crocut tape test according to JI3D-0202.

That is, first, use a knife to form 100 squares of 1 mm on the lens surface, then firmly press cellophane adhesive tape (Cellotape' manufactured by Nitto Kagaku Kiku) on the lens surface, and then apply it in a 90° direction from the surface. After the film was suddenly pulled off and peeled off, the remaining squares of the coat film were used as an index of adhesion.

h) Dyeability: The obtained sample was immersed in a plastic lens dyeing solution (Blacks dyeing agent Amber manufactured by Seiko Epson ■) for 90@05 minutes, and those with a dyeing concentration of 30% or more were judged as good.

Example 2 Acrylate ester of diarylidene pentaerythritol (Showa Kobunshi ■
Add 30 parts of product part name "Subirak T-500"), 10 parts of perfluorohexylethyl dimethacrylate, and 50 parts of butyl acetate, and while stirring, add 400 parts of magnesium fluoride of Example 1 and the fluorine-based surfactant. 3 parts of 0° was added to prepare a coating liquid. Polymethyl methacrylate was injection molded at a pressure of 1400 kg/cm'' and a 75 mm diameter sunglass lens whose distortion was corrected by annealing was immersed in this coating solution, and the coating and curing were performed in the same manner as in Example 1. The film had a high scratch strength of 0.5μ.

The evaluation results are shown in Table 1 in the same manner as in Example 1.

Example 3 30 parts of dibetaerythritol hexaacrylate, 20 parts of dipentaerythritol pentaacrylate, 5 parts of dipentaerythritol tetraacrylate, 15 parts of perfluoroisopropyl methacrylate, 2.2-bis-
While stirring 20 parts of (4-acryloyloxyjetoxyhexyl)propane, 15 parts of γ-methacryloxypropyltrimethoxysilane, 10 parts of isopropyl alcohol, and 30 parts of methyl acetate, water-dispersed calcium fluoride sol (particle size 5-10 millimicrons, solid content 30%) 30
0 part was slowly added to form a homogeneous solution. 0.3 parts of the silicone surfactant described above was added to this to prepare a coating liquid. A high refractive index lens (trade name: "Seiko High Road °° Non-Coated Lens, manufactured by Seiko Epson Field") was immersed in this coating solution and applied by pulling it up at a pulling speed of 30 cm/min. This was applied at 40"C for 20 minutes. After air drying, both surfaces were placed 2 cm directly below the light source and irradiated for 60 seconds using a 20 W low pressure mercury lamp in a nitrogen atmosphere to obtain a cured film. The film thickness at this time was 2.5 μm and had excellent transparency.

The evaluation results are shown in Table 1 in the same manner as in Example 1.

Example 4 The preparation, application, and curing of the coating liquid were carried out in the same manner as in Example 2, and instead of polymethyl methacrylate, bisphenol A polycarbonate resin (manufactured by Mitsubishi Kasei ■, trade name "
By injection molding "N0VAREX" and then using a 75 mm diameter prairens whose distortion was corrected by annealing, a lens with a high refractive index and high impact resistance was obtained. Table 1 shows the evaluation test results for the lenses thus obtained.

Comparative Example 1 The results of the evaluation test of a lens obtained in the same manner as in Example 1 except that the composition excluding the methanol-water-dispersed magnesium fluoride sol was used when preparing the coating film in Example 1 were evaluated.
Shown in the table.

Comparative Example 2 In Example 2, the coating liquid contained 12 parts of γ-glycidoxypropyltrimethoxysilane, 19 parts of methanol fraction colloidal silica, 29 parts of methyltrimethoxysilane,
After mixing 0.1 part of acetic acid and 20 parts of 0.05N hydrochloric acid and reacting at 80°C for 2 hours, ethyl cellosolve 1
6 parts, ammonium chloride 0. A coating solution was prepared by adding 3 parts. Using this coating liquid, after coating, 100°
The evaluation test results are shown in Table 1. The evaluation test results are shown in Table 1. The evaluation test results are shown in Table 1.

Comparative Example 3 In Example 1, instead of forming a cured film by coating, a 1 μm inorganic hard coat layer made of SiO2 was applied.
He made some money and made lenses. The evaluation results are shown in Table 1.

[Effect]

This coating composition uses magnesium fluoride (refractive index 1.25), which itself has a low refractive index, and contains a polymerizable organic compound that reacts and acts with these inorganic particles to form a strong, hard film as a binder component. Because it was used, it was applied and
The cured film forms a homogeneous, strong film with a low refractive index.

Therefore, the surface reflection (r) is expressed by Fresnel's formula (1) (% formula %) ... Formula (1) (where nl is the refractive index of air, nl is the refractive index of the base material, n
3 is the refractive index of the actual coating film. ) The above minimum value can be achieved when the film thickness is an odd multiple of 1/4. Ideally, for example, in the case of a base material with a refractive index of 1.6, the light reflection of a wavelength that is an odd multiple of a quarter of the thickness of a thin film with a refractive index of 1°26 will be zero. Due to this action, the present coaching composition can effectively reduce reflection. That is, in the present invention, the refractive index of the coating film is 1.30 to 1.30.
45, and reflections are kept between 0.2 and 3 percent.

〔Effect of the invention〕

The effect of the present invention is that as a plastic lens material, (
Including meth)acrylic resin, styrene resin, carbonate resin, allyl resin, allyl carbonate resin,
It can be applied to resins with various functions such as vinyl resin, polyester resin, polyether resin, and polymers of new monomers and comonomers. i.e. dyeable,
It is possible to obtain an antireflection functional thin film that can be produced in a large area at low cost and has excellent scratch resistance and good adhesion.

Therefore, it can be widely applied not only to eyeglass lenses but also as optical lenses such as camera lenses, light beam lenses, condensing lenses, and light diffusion lenses for consumer and industrial purposes. Furthermore, the effects of the present invention can be applied to transparent glasses such as watch glasses and display cover glasses;
Furthermore, it can be applied to all transparent plastics for optical applications, such as cover glasses, and the effects that can be obtained are great.

Claims (3)

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