JPH0770219A - Curing of ultraviolet-curing composition - Google Patents

Abstract

PURPOSE:To carry out the curing of an ultraviolet-curing composition giving a coating film having excellent durability and capable of keeping its low friction coefficient even by leaving standing in hot and humid atmosphere and useful as coating materials, etc., by irradiating a specific ultraviolet-curable composition with ultraviolet rays having respective specific wavelength and intensity. CONSTITUTION:An ultraviolet-curing composition containing (A) 100 pts.wt. of an ultraviolet-curing compound such as polyester (meth)acrylate and (B) preferably 0.3-5 pts.wt. of a silicone oil is cured by irradiating the composition with ultraviolet rays at prescribed radiation dose. The ultraviolet rays consist of a mixture of ultraviolet rays of >300nm wavelength and ultraviolet rays of <=300nm wavelength or exclusively ultraviolet rays having wavelength of >300nm. In the case of using a mixture of ultraviolet rays, the intensity of the ultraviolet rays of <=300nm wavelength corresponds to <=45% of the intensity of the ultraviolet rays of >300nm wavelength.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for curing an ultraviolet curable composition.

[0002]

2. Description of the Related Art In recent years, ultraviolet curable resins have been widely applied to the fields of inks, paints, adhesives and the like because of their advantages such as shortening of curing time, saving of energy and reduction of air pollution.

A protective coat composition used for protecting the recording layer of an optical card such as a compact disc and an optical card used for a hospital medical care card, etc., and also used for protecting a recording surface and a reading surface of a magneto-optical disk. Also in the protective coating composition, the application of the ultraviolet curable resin is being promoted.

In order to impart a low friction property to the recording surface protective film,
It is known to add silicone oil or the like to an ultraviolet curable resin (JP-A-4-306266, JP-A-3-118199, JP-A-3-119531).

[0005]

However, in the field where durability under high temperature and high humidity is required, there is a problem that the low friction property deteriorates in the high temperature and high humidity durability test with the above composition. Has become. In particular, in magnetic field modulation type magneto-optical discs, mini discs, etc., the magnetic head comes into contact with the recording protection film, and it is required to maintain not only the initial low friction property, but also the low friction property even after durability at high temperature and high humidity. There is.

According to the present invention, a cured product of an ultraviolet-curable composition having a low friction property imparted with silicone oil for protecting the surface of a plastic or the like has a low friction property of a coating film even when left under high temperature and high humidity. An object of the present invention is to provide an ultraviolet curing method for an ultraviolet curable composition, which can be maintained at a level almost equal to the initial level.

[0007]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that in curing a conventional ultraviolet curable composition containing an ultraviolet curable compound and a silicone oil, By using the ultraviolet light of the specific wavelength range, the drawbacks of the cured coating film when the composition is cured by conventional ultraviolet light containing a large amount of wavelengths of the specific wavelength range or less are eliminated, and even under conditions of high temperature and high humidity. The inventors have found that the low friction property continues for a long time without deterioration, and have completed the present invention.

That is, the present invention provides a method for curing an ultraviolet curable composition, which comprises curing an ultraviolet curable composition containing a silicone oil and an ultraviolet curable compound by irradiating a predetermined amount of ultraviolet light to the ultraviolet curable composition. Ultraviolet ray having a wavelength of more than 50 nm is used, and a method for curing an ultraviolet curable composition (hereinafter referred to as the first invention) and an ultraviolet curable composition containing a silicone oil and an ultraviolet curable compound are used. In the method for curing an ultraviolet curable composition, which comprises irradiating a predetermined amount of light to cure the ultraviolet curable composition, the ultraviolet rays having a wavelength of more than 300 nm and 300
Using ultraviolet rays mixed with ultraviolet rays having a wavelength of nm or less, 3
A method for curing an ultraviolet-curable composition, which is adjusted such that the intensity of ultraviolet rays having a wavelength of 00 nm or less is 45% or less of the intensity of ultraviolet rays having a wavelength of more than 300 nm (hereinafter referred to as the second invention. .) Is provided.

The ultraviolet-curable composition of the present invention comprises an ultraviolet-curable compound and a silicone oil as essential components, which are usually (A) an ultraviolet-curable prepolymer component and (B). ) It can be prepared by appropriately mixing an ultraviolet curable diluent component, (C) photopolymerization initiator component, (D) silicone oil component, and (E) organic amine compound component, if necessary. The ratio of the components (A) and (B) used alone or in combination thereof is determined by the physical properties of the cured product required for the composition.

The UV-curable compound is a known compound having an ethylenically unsaturated double bond, such as (meth)
The compound which has an acryloyl group is mentioned.

As the component (A), any known and commonly used UV-curable compound can be used. For example, polyester (meth) acrylate, polyurethane (meth) acrylate, epoxy (meth) acrylate, polyether (meth) acrylate, etc. However, the acrylate-based prepolymer having two or more (meth) acryloyl groups in the molecule is preferable.

The component (B) is conveniently classified into a component for increasing the cured coating film strength of the composition (hereinafter referred to as B1 component) and a diluting component for decreasing the viscosity of the composition (hereinafter referred to as B2 component). Yes, any of them can be used.

Classified as the component B1 used in the present invention are liquid compounds having two or more (meth) acryloyl groups in the molecule, and liquid compounds having three or more (meth) acryloyl groups. Compounds of are especially preferred.

Examples of the liquid compound having two (meth) acryloyl groups in the molecule include dicyclopentanyl di (meth) acrylate and ethylene oxide-modified bisphenol A di (meth) acrylate. Examples of the liquid compound having three or more (meth) acryloyl groups in the molecule include trimethylolpropane tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, dipentaerythritol monohydroxypenta (meth) acrylate, Alkyl-modified dipentaerythritol penta (meth) acrylate, alkyl-modified dipentaerythritol tetra (meth) acrylate, pentaerythritol tri (meth) acrylate
Acrylate, pentaerythritol tetra (meth) acrylate, tris [(meth) acryloxyethyl] isocyanurate, caprolactone-modified tris [(meth)]
Acryloxyethyl] isocyanurate and the like. These may be used alone or in combination of two or more.

Among these, it is particularly preferable to use trimethylolpropane tri (meth) acrylate in an amount of 30 to 75% by weight based on the total weight of the ultraviolet curable compound, from the viewpoint of viscosity and hardness of the obtained coating film.

Liquid compounds having 2 or less (meth) acryloyl groups in the molecule are classified as the B2 component used in the present invention. 2 (meta) in the molecule
Examples of the compound having an acryloyl group include tripropylene glycol di (meth) acrylate and 1,6-
Hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate and the like can be mentioned.
Examples of the compound having one (meth) acryloyl group in the molecule include 2- (2-ethoxyethoxy) ethyl (meth) acrylate, tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate and isobornyl ( (Meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentanyl (meth)
Acrylate etc. are mentioned.

As the UV-curable compound, those having a methacryloyl group and those having an acryloyl group are collectively shown as "(meth) acrylate" and exemplified, but the UV curability and the transparency of the cured product are taken into consideration. Then, it is preferable to use an acrylate compound.

The proportions of UV-curable compounds such as A, B1 and B2 components used are determined by the desired coating strength. When any of the components A, B1 and B2 is used, the viscosity of the composition of the present invention decreases as the proportion of the component B2 increases, but the coating film strength tends to weaken.

A in the total of A, B1 and B2 components
Ingredients and B1 component total usage ratio is 40-90% by weight in total
Is preferred. When the proportion of the component (A + B1) used is within the above range, the strength of the coating film obtained is high and the viscosity of the composition tends to be relatively low, which is preferable.

On the other hand, the proportion of the B2 component used in the total of the A, B1 and B2 components is preferably in the range of 5 to 40% by weight. When the use ratio of the B2 component is within the above range,
It is preferable because the dilution effect is large and the strength of the coating film obtained is large.

As the component (C), any of various photopolymerization initiators and photopolymerization sensitizers used in general UV-curable resins can be used. However, it is not preferable to use a hydrogen abstraction type photopolymerization initiator, and it is preferable to use a cleavage type photopolymerization initiator, from the viewpoint of preventing deterioration of the low friction property. For example, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isobutyl ether, 2-methylbenzoin, benzyl dimethyl ketal, 1- (4-isopropyl) -2-
Hydroxy-2-methylpropan-1-one, 1- (4
-Dodecylphenyl) -2-hydroxy-2-methylpropan-1-one, 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2,4,6- Examples thereof include trimethylbenzoyldiphenylphosphine oxide.

The above-mentioned photopolymerization initiator may be used in an amount sufficient to polymerize the UV-curable compound constituting the composition of the present invention, and usually the above-mentioned component (A).
When the total of (D) to (D) is 100, 1 to 10% by weight is selected and used.

Component (D) is a silicone oil,
Any known and conventional one can be used. Examples of the silicone oil include dimethyl polysiloxane, hydromethyl polysiloxane, methylphenyl polysiloxane,
Although various modified silicone oils can be mentioned, it is preferable to use a (poly) alkylene oxide modified silicone oil from the viewpoint that compatibility with the above-mentioned ultraviolet-curable compound and high low-friction property of the cured film can be combined.

Examples of the silicone oil include "Y-7006", "FZ-2164" and "FZ-216" manufactured by Nippon Unicar Co., Ltd.
1 "," L-7602 "," L-7001 "," L-7002 "," KF-341 "," KF-352 (A) "," SP-397 "manufactured by Shin-Etsu Chemical Co., Ltd.
0 "," SP-3711 "," KP-3O6 ", Toshiba Silicone Co., Ltd.
"TSF-4300", "TSF-4452", "TSF-4460", Toray Dow Corning Co., Ltd. "SH29PA", "ST94PA",
Commercially available products such as "ST96PA", "SH3749", "SH8410", "SH8700", and "Granol 410" manufactured by Kyoeisha Oil and Fat Chemical Co., Ltd. may be mentioned.

The amount of the silicone oil used is not particularly limited as long as the coating film exhibits a desired level of low friction property, but it is usually used per 100 parts by weight of the ultraviolet curable compound. It is 0.3 to 5 parts by weight. Further, when it is expressed as a usage ratio when the total of the components (A) to (D) is 100, it is selected and used so as to be 0.3 to 5% by weight.

The organic amine compound in the present invention is a component used as necessary, but it is the most important component for preventing the deterioration of the low friction property due to the above-mentioned silicone oil. As the organic amine compound, those having a functional group capable of reacting with the above-mentioned ultraviolet curable compound or silicone oil can be used, and those having no functional group can be used.

Examples of the organic amine compound include aliphatic amines such as triethylamine, methyldiethanolamine and triethanolamine, bis (N-methyl-2,
HALS (hindered amine) such as 2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, phenyl-4-piperidinyl carbonate, 2 -Dimethylaminoethyl benzoate, dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, p-
Aromatic amines such as isoamyl dimethylaminobenzoate are mentioned.

As the organic amine compound, those which can be copolymerized with the above-mentioned UV-curable compound can also be used.
Examples thereof include organic amine compounds having a morpholino skeleton or an alkyl-substituted amide skeleton, such as N,
N, -diethylaminoethyl (meth) acrylate,
Amino (meth) acrylates such as (meth) acrylmorpholine, N-isopropyl (meth) acrylamide,
N, N-dimethyl (meth) acrylamide, N, N,-
Examples include amino (meth) acrylamides such as dimethylaminopropyl (meth) acrylamide.

As the organic amine compound, those having the ability to photopolymerize the above-mentioned ultraviolet-curable compound can also be used. Examples thereof include 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1,2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone- 1 is mentioned.

As the organic amine compound used in the present invention, it is preferable to use one which does not inhibit the polymerization of the ultraviolet-curable compound itself by a Michael addition reaction or the like. As such a compound, it is preferable to use an organic amine compound which is inactive to an ethylenically unsaturated double bond.

When a high degree of adhesion to an aluminum base material is required and the coating film is required to have a low frictional holding force for a very long period of time under high temperature and high humidity conditions, an organic amine compound is used. It is preferable to use those which can be copolymerized with the above-mentioned UV-curable compound and those which have the ability to photopolymerize the above-mentioned UV-curable compound.
The field in which the above performance is required is, for example, the field of recording surface protective coating of an optical information recording medium.

As the organic amine compound copolymerizable with the UV-curable compound or the organic amine compound having the ability to photopolymerize the UV-curable compound, one having a morpholino skeleton in the molecule is used under high temperature and high humidity conditions. Is excellent in low-friction long-term holding power of the coating film, and in particular, an organic amine compound having a morpholino skeleton in the molecule and having an ability to photopolymerize an ultraviolet-curable compound can be used under high temperature and high humidity conditions. Not only the low friction long-term holding power of the coating film, but also the absolute value of the friction coefficient is excellent.

The amount of the organic amine used in the present invention is not particularly limited as long as it can maintain a low friction property, but is preferably 1 to 10 parts by weight per 1 part by weight of the silicone oil. In addition, the component (A) ~
If it is expressed as a usage ratio when the total of (D) is 100, it is selected and used so as to be 1 to 10% by weight.

When an organic amine compound copolymerizable with the above-mentioned UV-curable compound is used as the organic amine compound, physical properties of the coating film other than the adhesion to the substrate and the friction coefficient obtained from the UV-curable compound. It is better to determine the amount used in consideration of the above, on the other hand, when using an organic amine compound having the ability to photopolymerize the ultraviolet-curable compound, the amount of the photopolymerization initiator described above as a guideline Of course, it is good to determine the usage amount.

The composition of the present invention comprises, for example, polyolefin, polycarbonate, polyethylene terephthalate,
Synthetic resins such as polyphenylene sulfide, polyacetal, polyvinyl chloride, ABS, aluminum, titanium,
It can be applied to the surface of various base materials such as metals such as copper, silver, gold and stainless steel.

The composition of the present invention is applied to the surface of various base materials so as to obtain a desired cured film thickness, and then, if necessary, irradiated with ultraviolet rays in a nitrogen atmosphere to cure the composition. Good. The composition of the present invention can be applied to a substrate by using an apparatus such as an air sprayer, an airless sprayer, a dipping machine, a roll coater, a bar coater or a spin coater.

The composition of the present invention can be used not only as a coating material for an optical transmission medium such as an optical fiber or an optical waveguide or as a coating material for an optical information recording medium such as a CD, MD or an optical disk, but also as an electric material such as an IC chip or a light emitting diode. Electronic parts, magnetic tape,
Binder for magnetic materials of magnetic recording media such as floppy disks, surface protection and anti-scattering agent for window glass, incandescent lamps, glass bottles, metal foil, metal coating for beverage cans, abrasion resistance of plastic home appliances It can be used in various fields such as a coating agent, a release paper, and a paper treatment agent such as a decorative paper.

The composition of the present invention includes, for example, a silane coupling agent, a flame retardant, an antistatic agent, an antifogging agent, a coloring agent, and a leveling agent in addition to the above-mentioned ultraviolet curable compound, silicone oil and organic amine compound. If desired, various additives such as organic solvents can also be used.

When the composition of the present invention is used as a protective coating material for an optical information recording medium, especially for a protective coating of a recording layer, in order to further enhance the adhesion to the recording layer, The composition of the present invention includes, as an adhesion promoter, a carboxyl group or phosphoric acid such as ethylene oxide-modified succinic acid (meth) acrylate, ethylene oxide-modified phthalic acid (meth) acrylate, and ethylene oxide-modified phosphoric acid (meth) acrylate. It is also possible to add and use a (meth) acrylate having a group in the molecule. Generally, since the recording layer of an optical disk is formed of an inorganic thin film such as Al or Au, it is extremely effective to adopt the above means.

In order to prevent thermal polymerization during production and dark reaction during storage, the composition of the present invention contains hydroquinone monomethyl ether, t-butylcatechol, p-benzoquinone and 2,5-t-butyl. It is preferable to add a known thermal polymerization inhibitor such as hydroquinone or phenothiazine.

Further, a surfactant may be added to the composition of the present invention in order to improve the coatability. Examples of the surfactant include Dainippon Ink and Chemicals, Inc.
"Megafuck F-142D", "Megafuck F-144"
"D", "Megafuck F-150", "Megafuck F-17"
1 "," Megafuck F-173 "," Megafuck F-17 "
Fluorine-based nonionic surfactants such as "7" and "Megafuck F-183" can be mentioned.

In the present invention, the use of specific ultraviolet rays is particularly important. According to the knowledge of the present inventor, 3
Ultraviolet rays having a wavelength of 00 nm or less can cure the ultraviolet-curable composition by irradiating a predetermined amount of light. On the other hand, the cured coating film obtained by the irradiation of ultraviolet rays having this wavelength has a high degree of flexibility. It was found that the low frictional property was significantly reduced after passing through the conditions of high temperature and high humidity. However,
It was found that when a predetermined amount of light was irradiated using ultraviolet rays having a wavelength of more than 300 nm, such a phenomenon did not occur, and the high low friction property was retained even after the conditions of high temperature and high humidity. It was

Even for ultraviolet rays having a wavelength of 300 nm or less, the smaller the emission intensity / amount of light at that wavelength is, the smaller the emission intensity / amount of light at a wavelength exceeding 300 nm is.
It was found that the high degree of low-friction deterioration of the cured coating film becomes smaller even after the high temperature and high humidity condition.

The present invention is based on the above findings and uses ultraviolet rays as follows. (1) By using only ultraviolet rays having a wavelength exceeding 300 nm,
The ultraviolet curable composition is irradiated with a predetermined amount of light sufficient for curing to cure (the method of the first invention). (2) 300 n is used by using a mixture of ultraviolet rays having a wavelength exceeding 300 nm and ultraviolet rays having a wavelength of 300 nm or less.
They are used by adjusting them so that the ultraviolet emission intensity at a wavelength of m or less becomes 45% or less of the ultraviolet emission intensity at a wavelength of more than 300 nm, and the ultraviolet curable composition is irradiated with a predetermined amount of light and cured. (The method of the second invention).

Of the above two methods, the former method of the first invention is presumed to be due to deterioration of the cured coating film.
It is preferable because it does not use ultraviolet rays having a wavelength of 0 nm or less and can maintain a high degree of low friction.

Ultraviolet light means light having a short wavelength of about 390 nm (photon energy 3.2 eV), which is a short wavelength limit of visible light ["Chemical Dictionary", Shoji Shida, Editor-in-Chief,
Morikita Publishing Co., Ltd.]. Therefore, even if it is simply referred to as ultraviolet rays, there are various wavelengths of ultraviolet rays.

The light source used in the present invention is 300 nm.
A light source that emits only ultraviolet light having a wavelength of over 300 nm, a known light source that emits both ultraviolet light having a wavelength of more than 300 nm and ultraviolet light having a wavelength of 300 nm or less can be used.
When the latter light source is used, a light source having a light emission intensity / content rate of ultraviolet rays having a wavelength of 300 nm or less is used as little as possible, or ultraviolet rays having a wavelength of 300 nm or less emitted from the light source is cut and used. 30 emitted from the light source
The method of cutting and using ultraviolet rays having a wavelength of 0 nm or less is preferable in that the conventional light source can be used as it is.

As a method for cutting ultraviolet rays having a wavelength of 300 nm or less, an object capable of absorbing ultraviolet rays having a wavelength of 300 nm or less is allowed to pass therethrough to selectively separate ultraviolet rays having a wavelength of more than 300 nm, which is then used. do it. As a substance capable of absorbing ultraviolet rays having a wavelength of 300 nm or less, for example, a colored glass filter using an organic dye film, a non-alkali glass plate, a polyolefin film having a polar group in the molecule, or the like can be used.

It is difficult to apply a colored glass filter to a place where an ultraviolet light source always emits light in a production apparatus in view of the problem of deterioration of pigment (durability) and high cost (economical). From the viewpoint of poor durability but excellent durability, a non-alkali glass plate [eg HO Co., Ltd.
YA NANA-45] can be used as a filter. Polyolefin film having a polar group in the molecule [such as ARTO manufactured by Nippon Synthetic Rubber Co., Ltd.] can be used as a substitute for a filter that has poor durability but is economical.
N], which is very convenient because it can be used as a consumable item.

Further, as a light source having a low ultraviolet emission intensity of a wavelength of 300 nm or less, for example, an ozone-free type lamp or a metal halide lamp is preferably used.

When curing is performed by cutting ultraviolet rays having a wavelength of 300 nm or less, depending on the type and sensitivity of the photopolymerization initiator,
Although the curability may decrease, at this time, it is preferable to carry out the curing by irradiating with ultraviolet rays in an atmosphere of an inert gas that does not inhibit the curing of the ultraviolet curable compound. As the inert gas at this time, for example, nitrogen, helium, argon or the like can be used.

[0052]

The present invention will be described in detail below. First of all,
An ultraviolet curable composition having the following composition was prepared.

FA-731A: 15 parts by weight [Tris (acryloxy) isocyanurate] TMP3A: 61 parts by weight (trimethylolpropane triacrylate) 230: 15 parts by weight (1,6-hexanediol diacrylate) 184: 8 parts by weight (1-Hydroxycyclohexyl phenyl ketone) L-7001: 1 part by weight [Silicone oil manufactured by Nippon Unicar Co., Ltd.] F-173: 1 part by weight [Fluorine-based surfactant manufactured by Dainippon Ink and Chemicals, Inc.] EPA: 1 part by weight (ethyl p-dimethylaminobenzoate)

Next, a cured film having a thickness of 7 was formed on a polycarbonate substrate ["EC-100" manufactured by Chunchu Plastic Co., Ltd.].
The above composition is applied so as to have a thickness of ~ 8 μm, and a concentrating high-pressure mercury lamp (120 W / cm) and, if necessary, HOY CO., LTD.
NA-45 made by A [alkali-free glass plate (filter)]
By using a curing device (manufactured by Eye Graphics Co., Ltd.) in which it was set, the coating surface was irradiated with a predetermined amount of ultraviolet rays to be cured.

The ultraviolet light radiated on the coated surface is 30
In order to investigate how much ultraviolet light having a wavelength exceeding 0 nm and a wavelength less than 300 nm is contained, an ultraviolet illuminance meter UV-M01 manufactured by Oak Manufacturing Co., Ltd. was used to measure 365n.
UV light intensity around m (using UV-35) and 2
While measuring the amount of ultraviolet light around 54 nm, the amount of ultraviolet irradiation light at least 360 nm is 6
The coated surface was cured by irradiating the coated surface with ultraviolet rays at a dose of 00 mJ / cm ² .

As the light source, an ozone-free condensing type high-pressure mercury lamp (120 W / cm) whose emission intensity at a wavelength of 300 nm or less is much smaller than that at a wavelength of 300 nm or less, and a wavelength of 300 nm or less are used. And a high pressure mercury lamp with ozone (120 W / cm) including a wavelength exceeding that was used.

Comparative Example 1 Concentration type high pressure mercury lamp with ozone (120 W / cm)
Is used as it is and the irradiation light amount at 360 nm is 60
A cured film was obtained by irradiating with ultraviolet light in the air so as to obtain 0 mJ / cm ² . At the same time, the ultraviolet irradiation light amount of 254 nm was also measured, and the value is shown in Table 1. The obtained cured film was evaluated for the change in friction coefficient before and after the high temperature and high humidity test according to the method described below, and the results are shown in Table 1.

(1) High temperature and high humidity test A test piece was put in a constant temperature and humidity tester at 85 ° C. and 95% RH for 100 hours. (2) Friction coefficient According to ASTM-D-1894-63, the frictional force between the cured film formed on the PC substrate and the 200 g of the stainless slide piece was measured at a pulling speed of 100 mm / min.

Example 1 Concentration type high pressure mercury lamp with ozone (120 W / cm)
The same operation as in Comparative Example 1 was performed except that an ozone-free type high-pressure mercury lamp (120 W / cm) was used instead of. The change in the friction coefficient before and after the high temperature and high humidity test of the obtained cured film was evaluated by irradiating the 254 nm ultraviolet light.
The results are shown in Table 1.

Example 2 Concentration type high pressure mercury lamp with ozone (120 W / cm)
And NA-45 manufactured by HOYA Co., Ltd.
so that the irradiation light amount at m is 600 mJ / cm ² ,
Ultraviolet rays were irradiated in nitrogen to obtain a cured film. 254 nm
The amount of UV irradiation light and the change in friction coefficient of the obtained cured film before and after the high temperature and high humidity test were evaluated, and the results are shown in Table 1.

[0061]

[Table 1]

As can be seen from Table 1, as the amount of ultraviolet light at a wavelength of 300 nm or less decreases, the degree of deterioration of the friction coefficient in the high temperature and high humidity endurance test decreases, and the low level in a severe environment. It is clear that the friction durability is high.

Comparative Example 2 The same operation as in Comparative Example 1 was performed except that the irradiation of ultraviolet rays was performed in a nitrogen atmosphere. The amount of UV irradiation at 254 nm is 4
At 20 mJ / cm ² , the coefficient of friction of the obtained cured film before the high temperature and high humidity test was 0.11, and the friction coefficient after the high temperature and high humidity test was 0.57.

[0064]

According to the ultraviolet curing method of the present invention, 300 n
Since the ultraviolet curable composition containing the silicone oil is cured exclusively by using the ultraviolet rays having a wavelength exceeding m, a particularly remarkable effect that a surface having an excellent low friction property which is not deteriorated even in a harsh environment is obtained. Play. Therefore, the curing method of the present invention is particularly useful for forming a protective coat film used for protecting the recording layer of an optical disc such as a mini disc or a magnetic field modulation type magneto-optical disc, or a protective coat film for a reading surface of a magneto-optical disc or the like. It is extremely useful as a curing method for

Claims (8)

[Claims] 1. A method for curing an ultraviolet curable composition, which comprises curing an ultraviolet curable composition containing a silicone oil and an ultraviolet curable compound by irradiating a predetermined amount of ultraviolet light to the ultraviolet curable composition, wherein the ultraviolet ray has a wavelength of more than 300 nm. Of ultraviolet light having a wavelength of 300 nm or less is used.
A method for curing an ultraviolet-curable composition, which is adjusted to 45% or less of the intensity of ultraviolet light having a wavelength of more than nm and used, or only ultraviolet light having a wavelength of more than 300 nm is used. 2. A method for curing an ultraviolet curable composition, which comprises curing an ultraviolet curable composition containing a silicone oil and an ultraviolet curable compound by irradiating a predetermined amount of ultraviolet light on the ultraviolet curable composition, wherein the ultraviolet ray has a wavelength of more than 300 nm. 2. A method for curing an ultraviolet curable composition, which comprises using only the ultraviolet ray of 1. 3. A method for curing an ultraviolet curable composition, which comprises irradiating an ultraviolet curable composition containing a silicone oil and an ultraviolet curable compound with a predetermined amount of ultraviolet light to cure the composition, wherein the ultraviolet ray has a wavelength of more than 300 nm. Of ultraviolet light having a wavelength of 300 nm or less is used.
A method for curing an ultraviolet-curable composition, which comprises adjusting and using them so that they have an intensity of 45% or less of an ultraviolet intensity of a wavelength exceeding nm. 4. A non-alkali glass plate or a polyolefin film having a polar group in the molecule is used as a filter,
The curing method according to claim 1, wherein only ultraviolet rays having a wavelength exceeding 300 nm obtained by passing the ultraviolet rays are used. 5. The curing method according to claim 1, wherein the curing is performed in an atmosphere of an inert gas that does not inhibit the curing of the ultraviolet curable compound. 6. A non-alkali glass plate or a polyolefin film having a polar group in the molecule is used as a filter,
The curing method according to claim 1, wherein the curing is performed in an atmosphere of an inert gas that does not inhibit the curing of the ultraviolet curable compound, using only ultraviolet rays having a wavelength of more than 300 nm obtained by passing the ultraviolet ray. 7. The curing method according to claim 1, wherein the ultraviolet curable composition comprises a silicone oil, an ultraviolet curable compound and an organic amine compound. 8. The curing method according to claim 1, wherein the ultraviolet curable compound is an ultraviolet curable compound having two or more (meth) acryloyl groups in the molecule.