JPH10120982A - Ultraviolet-curable composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a composition as an adhesive to be used in mutually laminating two disks on or both of which has an information-recorded layer, good in curability and causing no substrate deterioration, and affording highly reliable digital video disks in high productivity with short-time curing. SOLUTION: This ultraviolet-curable composition contains, as photopolymerization initiator, at least each one kind of compound, namely: (A) compound highly sensitive to even ultraviolet light attenuated after transmitted through an information-recorded layer and the like and having a molar extinction coefficient of >=50(l/mol cm) in the wavelength band of 370 to 450nm and (B) different compound hardly subject to oxygen inhibition and of intramolecular cleavage type or hydrogen pull-off type.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an adhesive used for bonding two disks having an information recording layer to at least one disk, and more particularly to an ultraviolet-curable composition used as an adhesive. About.

[0002]

2. Description of the Related Art A digital video disk (DVD), which is a high-density information recording medium, is manufactured by bonding two disks having an information recording layer to at least one disk and bonding an ultraviolet-curable composition to the disk. Its use as an agent has been actively studied.

In the case of a read-only type DVD, as two disks to be bonded, irregularities corresponding to recorded information are provided on one surface of a heat-resistant thermoplastic resin substrate represented by polycarbonate, and a metal thin film such as aluminum or There is a case where a layer having a layer of gold or the like is formed, or a case where a transparent heat-resistant thermoplastic resin substrate having no information recording layer is used for one sheet, and the substrate is appropriately selected according to the application. .

[0004] First, it is necessary that the two disks are securely adhered in a normal state, and the bonded disks are not deformed even after a high-temperature and high-humidity environmental test as well as in a normal state. It is required that there is no change. The properties of the adhesive used greatly affect the changes after the environmental test, and depending on the type of adhesive, pinholes may occur in the metal thin film layer provided as the information recording layer, or transparent heat resistance The thermoplastic resin substrate may be turned whitish in some cases.

It is well known that the influence of the ultraviolet-curable composition used on such alteration of the substrate or the like is great, and generally, the influence of the reactive monomer or oligomer used is great. Was thought.

However, the deterioration of the substrate or the like is not conclusively attributed to it. Even if a reactive component which is expected to have relatively little deterioration of the substrate or the information recording layer is selected, it is not included in the ultraviolet-curable composition. It has been found from the knowledge of the present inventors that the type of the photopolymerization initiator is greatly affected.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an ultraviolet curable composition which provides a cured product which does not cause deterioration of a substrate or an information recording layer even under a severe environment. It is in.

[0008]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, even when the same reactive monomer or oligomer component is used and only the photopolymerization initiator component is changed, severe strictness is required. Under the environment, the degree of deterioration of the substrate and the information recording layer is greatly different, and when using an ultraviolet curable composition as an adhesive for DVD, the selection of a photopolymerization initiator from the viewpoint of not only the curability but also the deterioration of the substrate. Have been found to be extremely important and have led to the present invention.

That is, according to the present invention, the adhesive used for bonding two disks having an information recording layer to at least one disk is selected from the following photopolymerization initiator groups (A) and (B). Further, the present invention provides an ultraviolet-curable composition characterized by containing one or more types. (A) A photopolymerization initiator having a point where the molar extinction coefficient is 50 (l / mol cm) or more in a wavelength range of 370 nm to 450 nm. (B) a photopolymerization initiator which is an intramolecular cleavage type or hydrogen abstraction type and does not belong to (A).

[0010] Among the photopolymerization initiators used in the present invention,
Examples of the photopolymerization initiator belonging to (A) include benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, benzyl, 2,4,6-trimethylbenzoyldiphenylphosphine oxide, Benzyl-2
-Dimethylamino-1- (4-morpholinophenyl)
-Butanone-1, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like. These groups (A) are sensitive to extremely attenuated weak ultraviolet rays.

Of these photopolymerization initiators, 2,4,6-
Trimethylbenzoyldiphenylphosphine oxide,
2-Benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1, bis (2,6-dimethoxybenzoyl) -2,4,4-trimethylpentylphosphine oxide and the like are ultraviolet rays transmitted through the substrate. Although it has excellent curability because it reacts sensitively to water, it tends to be susceptible to oxygen inhibition, and when used alone, there is a tendency for curing to be insufficient at the part that comes into contact with air.

As a photopolymerization initiator, a wavelength range of 370 n
m from 450 nm, the molar extinction coefficient is 50 (l / m
ol cm) or more, particularly preferably 500 (l / mol cm) or more.

The photopolymerization initiator belonging to (B) can be used in combination to solve this drawback, and benzoylethyl ether, benzyldimethylketal, 1-hydroxycyclohexylphenylketone,
2-hydroxy-2-methyl-1-phenyl-propan-1-one, 1- (4-isopropylphenyl) -2-
Examples thereof include hydroxy-2-methylpropan-1-one and 2-methyl-1- (4-methylthiophenyl) -2-morpholino-propanone-1-one.

Further, as a hydrogen extraction type, for example, 4-
Examples thereof include phenylbenzophenone, isophthalophenone, and 4-benzoyl-4'-methyl-diphenylsulfide. These groups (B) are less susceptible to polymerization inhibition by oxygen.

The combination ratio of the photopolymerization initiator groups (A) and (B) is not particularly limited, but is usually (group A) / group (B) (weight ratio) = 20 / 80-80. / 20, preferably 60/40 to 40/60.

In addition to the above photopolymerization initiator, sensitizers such as triethylamine, methyldiethanolamine, triethanolamine, diethylaminoacetophenone, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, and p-dimethylaminobenzoic acid Isoamyl, N, N-dimethylbenzylamine and 4,
An amine that does not cause an addition polymerization reaction with a polymerizable component described later, such as 4′-bis (diethylamino) benzophenone, can be used in combination. Of course, it is preferable to select and use the photopolymerization initiator and the sensitizer that have excellent solubility in the curable component and do not inhibit the ultraviolet transmittance.

In preparing the ultraviolet curable composition, a monofunctional (meth) acrylate or a polyfunctional (meth) acrylate can be used as a polymerizable monomer component. Each of these can be used alone or in combination of two or more. However, it is preferable to prepare a composition using two or more polyfunctional (meth) acrylates having two or more (meth) acryloyl groups as essential components.

Examples of the polymerizable monomer that can be used in the present invention include the following. Examples of the monofunctional (meth) acrylate include, as a substituent, methyl, ethyl, propyl, butyl, amyl, 2-ethylhexyl,
Octyl, nonyl, dodecyl, hexadecyl, octadecyl, cyclohexyl, benzyl, methoxyethyl, butoxyethyl, phenoxyethyl, nonylphenoxyethyl, tetrahydrofurfuryl, glycidyl, 2-hydroxyethyl, 2-hydroxypropyl, 3-chloro-
Having a group such as 2-hydroxypropyl, dimethylaminoethyl, diethylaminoethyl, nonylphenoxyethyltetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, etc. A) acrylate and the like.

Examples of the polyfunctional (meth) acrylate include 1,3-butylene glycol, 1,4-butanediol, 1,5-pentanediol, and 3-methyl-acrylate.
1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, tricyclodecanedimethanol, ethylene glycol, polyethylene glycol, propylene glycol, tripropylene glycol , Diacrylates such as polypropylene glycol, di (meth) acrylates of tris (2-hydroxyethyl) isocyanurate, di (meth) acrylates of diols obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol. ) Di (meth) acrylate of diol obtained by adding 2 mol of ethylene oxide or propylene oxide to 1 mol of acrylate or bisphenol A, 3 mol or more per 1 mol of trimethylolpropane Diol or tri (meth) acrylate of triol obtained by adding ethylene oxide or propylene oxide, or di (meth) acrylate / tris () of diol obtained by adding 4 mol or more of ethylene oxide or propylene oxide to 1 mol of bisphenol A 2- (hydroxyethyl) isocyanurate tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol tri (meth) acrylate / dipentaerythritol poly (meth) acrylate / caprolactone modified tris [(meth) acryloxyethyl ] Poly (meth) acrylate of isocyanurate, alkyl-modified dipentaerythritol, poly (meth) acrylate of caprolactone-modified dipentaerythritol / hydroxy Phosphoric acid neopentyl glycol diacrylate, caprolactone modified hydroxypivalic acid neopentyl glycol diacrylate / ethylene oxide-modified phosphoric acid (meth) acrylate, ethylene oxide-modified alkylated phosphoric acid (meth) acrylate and the like.

Also, N-vinyl-2-pyrrolidone, acryloylmorpholine, vinylimidazole, N-vinylcaprolactam, vinyl acetate, (meth) acrylic acid,
(Meth) acrylamide, N-hydroxymethylacrylamide or N-hydroxyethylacrylamide and their alkyl ether compounds can also be used.

Further, those which can be used in combination with the polymerizable monomer include polyester acrylate, polyether acrylate, epoxy acrylate and urethane acrylate as polymerizable oligomers.

In order to obtain higher adhesion to an information recording layer mainly composed of a metal thin film, a (meth) acrylate compound having a functional group consisting of phosphoric acid or a derivative thereof is included in the composition, and the hardness is increased. In order to increase further,
In order to include a (meth) acrylate compound having a larger number of (meth) acryloyl groups in one molecule, similarly, a larger number of the same functional groups should be included. A relatively high molecular weight polymerization component can be included.

The ultraviolet-curable composition may be used at room temperature to 40
It is preferable to use one that is liquid at a temperature of ° C. It is preferable not to use a solvent, and even if it is used, it is preferable to keep it as small as possible. When the composition is applied by a spin coater, the viscosity is preferably adjusted to 20 to 1000 centipoise, and when the composition is relatively thick, the viscosity is adjusted to 100 to 1000 centipoise. Is good.

In the present invention, the recording layers are adhered to each other, but the exposed information recording layers may be directly adhered to each other, or a protective coat layer for protecting the exposed surface of the information recording layer may be provided thereon. And the protective coat layers may be bonded to each other. In this case, this protective coat layer is also usually formed of a cured product of the ultraviolet curable composition. In this case, this protective coat layer needs to be transparent to ultraviolet rays. The UV-curable composition for the protective coat layer is preferably prepared so that the exposed surface of the information recording layer and the cured product of the UV-curable composition for bonding disks to each other have excellent adhesion. .

The composition of the present invention may further comprise, if necessary, further additives such as an antioxidant represented by a thermal polymerization inhibitor, a hindered phenol, a hindered amine, a phosphite, a plasticizer, and the like. Epoxy silane,
A silane coupling agent typified by mercaptosilane, (meth) acrylsilane and the like can be blended in a conventional amount for the purpose of improving various properties. These are selected from those having excellent solubility in the curable component and those that do not impair the ultraviolet transmittance.

In preparing the composition of the present invention,
In addition to the photopolymerization initiator, the chemical composition is appropriately selected so that the physical properties of the composition itself and the physical properties of the bonded cured layer are suitable for DVD.

As a criterion at this time, it is premised that the information recorded in the information recording layer is not deteriorated, that is, no abnormality occurs in the pits. Or have no level separation, have high wettability to both surfaces to be bonded, and have leveling property to provide a smooth and uniform wet surface in a short time. The two surfaces to be bonded should contain as little as possible substances or ions that cause corrosion or deterioration of the surface, the composition before curing has a certain degree of adhesiveness even in a liquid state, and a gas that contributes to the inhibition of curing. The solubility of the composition is as small as possible, that the composition has transparency that transmits ultraviolet rays as high as possible before and after curing, and between the adhesive layer after curing and the heat-resistant thermoplastic resin constituting the substrate. Refractive index and hardness It is as much as possible the same, the adhesion of the bonded two layers and the cured layer to such larger,
The elastic modulus of the cured layer should be within a specific range, the moisture permeability of the cured layer should be minimized, and the shrinkage of the composition before and after curing should be minimized. And that the measured value of each of these evaluation items is excellent as an absolute value, and that a change between these absolute values is as small as possible in a normal state and when exposed to high temperature and high humidity for a long time. . An ultraviolet curable composition containing a photopolymerization initiator is prepared so as to satisfy all of these criteria or as many as possible.

Further, the composition of the present invention can be used as an ultraviolet irradiation method for curing, in addition to using continuous light irradiation, which is generally widely performed, as well as the irradiation light amount required for curing by conventional continuous light irradiation. The same amount or less light amount, for example, μsec
It may be performed by a flash irradiation method in which irradiation is performed at once in a short time of the order of msec.

The light irradiation may be performed from only one side of the opposed disk, or may be performed from both sides.

The composition of the present invention can be used, for example, in a method for producing a digital video disc, by combining a disc substrate in which an information recording thin film is laminated on a heat-resistant thermoplastic resin with a substrate made of only a heat-resistant thermoplastic resin. Particularly effective for bonding. The effect of preventing white turbidity and whitening of the substrate under severe environmental conditions is remarkable when the heat-resistant thermoplastic resin constituting the substrate is polycarbonate.

In this case, after the substrates are opposed to each other,
Normally, the composition of the present invention is cured and bonded by irradiating ultraviolet rays from the side of the substrate made of only a heat-resistant thermoplastic resin.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described. First, one disc-shaped plastic substrate on which a metal thin film of 400 to 600 angstroms is laminated and one substrate made of only disc-shaped plastic are prepared.

Next, two or more polyfunctional (meth) acrylates having two or more (meth) acryloyl groups are used as an essential component and a main component, and, if necessary, a photopolymerization initiator (A) ) Has an absorption wavelength in the region of 370 nm or more, and
In nm, a photopolymerization initiator having a point where the molar extinction coefficient is 50 (l / mol cm) or more, and (B) a photopolymerization initiator which does not belong to (A) in an intramolecular cleavage type or hydrogen abstraction type, The composition is prepared using a total of 2 to 7 parts by weight per 100 parts by weight of the liquid ultraviolet curable composition. However, benzophenone is not included in this composition.

More preferred selective combinations of the photopolymerization initiator groups (A) and (B) are as follows. Photopolymerization initiator group (A): wavelength range from 370 nm to 450
Those having a point at which the molar extinction coefficient is 500 (l / molcm) or more in nm. Photopolymerization initiator group (B): benzoyl ethyl ether, benzyl dimethyl ketal, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-
Phenyl-propan-1-one, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropane-
1-one, 2-methyl-1- (4-methylthiophenyl) -2-morpholino-propanone-1-one (above,
Intramolecular cleavage type photopolymerization initiator), 4-phenylbenzophenone, isophthalophenone, 4-benzoyl-4'-methyl-diphenylsulfide (the above is a hydrogen abstraction type photopolymerization initiator).

The composition is applied to the metal thin film surface of the substrate, and the substrates are bonded to each other. Then, ultraviolet rays are irradiated from the surfaces of both plastic substrates to adhere the two to each other.
VD.

[0036]

Next, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples. Hereinafter, "parts" in the examples means "parts by weight".

Example 1 20 parts of neopentyl glycol diacrylate, 20 parts of diol diacrylate obtained by reacting 2 mol of ethylene oxide with 1 mol of bisphenol A, 30 parts of trimethylolpropane triacrylate, 1 mol of polytetramethylene glycol (molecular weight: 850) 26 parts of urethane acrylate obtained by reacting 2 mol of hydroxyethyl acrylate after reacting with 2 mol of tolylene diisocyanate and 2 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2 parts of benzyl dimethyl ketal as a photopolymerization initiator. The mixture was mixed and dissolved at a temperature of 1 ° C. for 1 hour to prepare a pale yellow transparent ultraviolet curable composition. Using this composition, a bonded disk was prepared by the following test method 1. When the disk end face was touched with finger, there was no tackiness. When the disc was observed for 96 hours in an environment of 85 ° C. and 95% RH for 96 hours, there was no change as compared with that before the environmental test.

<Test Method 1> Aluminum having a diameter of 500 Å was formed as a metal thin film.
The above composition was applied to one of the two disc-shaped polycarbonate substrates by a dispenser, and then another substrate was superposed. When the composition is pushed and spread only by the weight of the substrate, the thickness of the composition becomes 20%.
５０50 μm. Then, irradiation intensity 55mW
Conveyor speed 3 using a belt conveyor type ultraviolet irradiation device equipped with a condensing metal halide lamp (with a cold mirror, lamp output 80 W / cm) adjusted to / cm ²
The composition was cured at m / min (irradiation light amount: about 230 mJ / cm ² ). Light irradiation was performed from both surfaces of the two polycarbonate substrates.

Example 2 The polymerizable components were the same as in Example 1 above, and 2 parts of 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 were used as a photopolymerization initiator and benzyl Mix and dissolve 2 parts of dimethyl ketal at 60 ° C for 1 hour,
A pale yellow transparent ultraviolet curable composition was prepared. A bonded disk was prepared using this composition in the same manner as in Example 1, and the disk end face was touched with no tack. When the appearance was observed after a lapse of 96 hours in an environment of 85 ° C. and 95% RH, there was no change as compared with before the environmental test.

Example 3 The polymerizable components were the same as in Example 1 above, and 2 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2 parts of benzyldimethyl ketal were mixed and dissolved at 60 ° C. for 1 hour as a photopolymerization initiator. Then, a pale yellow transparent ultraviolet curable composition was prepared. Using this composition, a laminated disk was produced by the following test method 2, and the disk end face was touched with no tackiness. When the disc was observed for 96 hours in an environment of 85 ° C. and 95% RH for 96 hours, there was no change as compared with that before the environmental test. <Test Method 2> The above composition was applied by a dispenser to a 12-cm-diameter disc-shaped polycarbonate substrate formed of aluminum as a metal thin film to a thickness of 500 angstroms, and then a 12-cm-diameter transparent disc-shaped polycarbonate substrate was overlaid. When the composition is pushed and spread only by the weight of the substrate, the thickness of the composition becomes 20 to 5
The thickness was set to 0 μm. Then, irradiation intensity 55mW / cm ²
Conveyor speed 3m / using a belt conveyor type ultraviolet irradiation device equipped with a concentrating metal halide lamp (with a cold mirror, lamp output 80W / cm) adjusted to
(cured light amount of about 230 mJ / cm ² ).
In addition, light irradiation was performed from both polycarbonate substrate surfaces on which a substrate made of only polycarbonate and an aluminum thin film were laminated.

Example 4 The polymerizable components were the same as in Example 1 above, and 2 parts of 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 and 2 parts of benzyl as a photopolymerization initiator were used. Mix and dissolve 2 parts of dimethyl ketal at 60 ° C for 1 hour,
A pale yellow transparent ultraviolet curable composition was prepared. Using this composition, a bonded disk was prepared in the same manner as in Example 3, and the disk end face was touched with no tack. When the appearance was observed after a lapse of 96 hours in an environment of 85 ° C. and 95% RH, there was no change as compared with before the environmental test.

Each of the photopolymerization initiators of group (A) in Examples 1 to 4 has an absorption wavelength in the region of 370 nm or more, and has a molar extinction coefficient of 5 from 370 to 450 nm.
It had a point of not less than 00 (l / mol cm).

A DVD in which the metal thin film layers are laminated together, and a DVD in which the metal thin film layers are laminated together, and a heat resistant laminate in which the metal thin film layers are laminated are laminated with the compositions of Examples 1 to 4. DV bonded to a metal thin film layer of a heat-resistant thermoplastic resin substrate and a substrate made of only heat-resistant thermoplastic resin
D shows that in any case, for example, even in a severe environment in which the DVD is exposed to high temperature and high humidity for a long period of time, no deterioration is observed in the DVD.

In addition, the compositions of Examples 1 to 4 have the following two advantages in addition to the above-mentioned technical features. That is, it is excellent not only in terms of curability that efficient curing adhesion can be performed, but also in that tackiness is not recognized even in a portion protruding from the end face of the bonded disc.

Each of the compositions of Examples 1 to 4 was suitable as an ultraviolet-curable composition used as an adhesive for a DVD of a lamination type.

In the embodiment, the continuous illumination light, which is generally widely used as the ultraviolet irradiation method, is used, but it is a matter of course that the flash irradiation method as described above may be used.

[0047]

By using the composition of the present invention,
Even after exposure to a severe environment such as a high-temperature and high-humidity environment test, the bonded disc does not deteriorate, so that a DVD with high durability and high reliability can be produced.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C08F 20/12 C08F 20/12

Claims (5)

[Claims] An adhesive used for bonding two disks having an information recording layer to at least one disk is one selected from the following photopolymerization initiator groups (A) and (B). An ultraviolet curable composition comprising at least one kind. (A) A photopolymerization initiator having a point where the molar extinction coefficient is 50 (l / mol cm) or more in a wavelength range of 370 nm to 450 nm. (B) a photopolymerization initiator which is an intramolecular cleavage type or hydrogen abstraction type and does not belong to (A). 2. The photopolymerization initiator group (A) having a point at which a molar extinction coefficient is 500 (l / mol cm) or more in a wavelength range of 370 nm to 450 nm is used. 2. The ultraviolet-curable composition according to 1. 3. An ultraviolet-curable composition comprising 0.1 to 10 parts of the photopolymerization initiator according to claim 1 or 2. 4. The ultraviolet curable composition according to claim 1, wherein the two disks to be bonded are a disk having an information recording layer and a transparent polycarbonate substrate having no information recording layer. 5. The ultraviolet-curable composition according to claim 1, wherein the adhesive comprises two or more polyfunctional (meth) acrylates having two or more (meth) acryloyl groups as essential components.
The composition according to 2, 3 or 4.