JPH09169956A - UV curable composition - Google Patents

Abstract

(57) Abstract: When an ultraviolet curable composition is used as an adhesive used when two discs having an information recording layer are bonded to at least one disc, the information recording layer and the like are transmitted. Provided is an ultraviolet curable composition which can be cured in a short time even with attenuated ultraviolet rays and has excellent curability. A photopolymerization initiator having an absorption wavelength in a region of 370 nm or more, preferably a wavelength region 3
The molar extinction coefficient is 50 from 70 nm to 450 nm.
An ultraviolet-curable composition characterized in that it has a point of (l / mol cm) or more.

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 In recent years, a digital video disk (DVD) has come into the limelight as a high density information recording medium, and a method of adhering two disks each having an information recording layer has been proposed as a method for increasing the density. The use of an ultraviolet-curable adhesive has been proposed as a method of bonding two disks together, and is being actively studied.

If at least one of the disks to be laminated is UV-transparent, the UV-curable composition conventionally used as a protective coating agent for an optical disk will be cured within a few seconds even if it is used as an adhesive. Moreover, since the protective coating agent for optical disks has an excellent metal thin film protective function, it can be suitably used as an adhesive agent for a DVD of a bonding system.

However, in the case where both the two discs have a thin film made of metal or a layer which does not transmit much ultraviolet rays,
By the time the ultraviolet rays reach the adhesive layer, the strength is greatly attenuated by the information recording layer, and there is a problem that efficient curing and adhesion cannot be performed.

In the case of a read-only DVD, a polycarbonate substrate is provided with irregularities corresponding to recorded information on one side thereof, and a layer of, for example, aluminum is formed as a metal thin film. Usually, this aluminum thin film layer has a thickness of several hundred angstroms so that visible rays used for reading recorded information can be reflected at a high rate and the irregularities can be confirmed. When the film thickness of aluminum is 500 angstroms, the ultraviolet rays transmitted through this layer are only in the region of about 360 nm or more, and the transmittance is only about 0.3%. When the above-mentioned optical disk protective coating agent is used for laminating such disks, it cannot be practically cured because it is not cured at all even by ultraviolet irradiation or irradiation time is several tens of seconds or more. It was

In the read-only DVD, there is a case where a polycarbonate substrate having no recording information is used for one of the two disks to be bonded. Although this polycarbonate substrate transmits ultraviolet rays, it has 360
Since the transmittance sharply decreases from about 90% to almost 0% from nm to 280 nm, efficient curing cannot be achieved when the above-mentioned optical disk protective coating agent is used.

Therefore, when two discs having an information recording layer are attached to at least one disc by using the ultraviolet curable composition, the photopolymerization initiator contained in the composition also penetrates the thin film and the like. In order to react sensitively to ultraviolet rays, it is necessary to select ultraviolet rays and absorption wavelengths so that they overlap in as many regions as possible.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is ultraviolet curing as an adhesive used when two discs having an information recording layer are attached to at least one disc. An object of the present invention is to provide an ultraviolet curable composition having excellent curability that can be cured in a short time even with ultraviolet rays that have been transmitted through an information recording layer and attenuated when the mold composition is used.

[0009]

DISCLOSURE OF THE INVENTION As a result of intensive studies for solving the above problems, the present inventors have found that an ultraviolet curable composition using a photopolymerization initiator having absorption up to a wavelength range of 370 nm or more. It was found that the above problem can be solved by using. Furthermore, in the wavelength region of 370 nm to 450 nm of the photopolymerization initiator,
It has been found that the problem can be more effectively solved by using a substance having a molar extinction coefficient of 50 (l / mol cm) or more.

That is, in the present invention, the adhesive used for bonding two discs having an information recording layer to at least one disc is an ultraviolet curable composition, and a region of 370 nm or more as a photopolymerization initiator. To provide an ultraviolet-curable composition characterized by using a compound having an absorption wavelength in the wavelength region 370.
From 50 nm to 450 nm, the molar extinction coefficient is 50 (l
/ mol cm) or more, and to provide an ultraviolet-curable composition.

The photopolymerization initiator used in the present invention includes:
For example, benzophenone, benzoin isobutyl ether, 2,4-diethylthioxanthone, 2-isopropylthioxanthone, 2-chlorothioxanthone, benzyl, 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 can be mentioned.
Among these photopolymerization initiators, 2,4-diethylthioxanthone, 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 particularly preferable when used for this purpose because of their excellent curability.

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 is the ultraviolet curable composition 1
It is used in an amount of 0.1 to 10 parts by weight, preferably 2 to 7 parts by weight, per 100 parts by weight. If the amount is less than 0.1 parts by weight, sufficient curability cannot be obtained, and if the amount is more than 10 parts by weight, the amount remaining as an uncured component in the cured coating film increases, which is not preferable from the viewpoint of long-term reliability.

As a sensitizer for the above photopolymerization initiator, for example, triethylamine, methyldiethanolamine, triethanolamine, diethylaminoacetophenone, p-dimethylaminoacetophenone, ethyl p-dimethylaminobenzoate, 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.

When 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, nonylphenoxyethyl tetrahydrofurfuryl, caprolactone-modified tetrahydrofurfuryl, isobornyl, dicyclopentanyl, dicyclopentenyl, dicyclopentenyloxyethyl, etc. ) 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, polypropylene glycol, etc. Diacrylate, tris (2-hydroxyethyl)
Di (meth) acrylate of isocyanurate, di (meth) acrylate of diol obtained by adding at least 4 mol of ethylene oxide or propylene oxide to 1 mol of neopentyl glycol, 2 mol of ethylene oxide or propylene oxide to 1 mol of bisphenol A Of triol obtained by adding 3 moles or more of ethylene oxide or propylene oxide to 1 mole of diol di (meth) acrylate obtained by the addition of trimethylolpropane, and 4 moles per 1 mole of bisphenol A. Di (meth) acrylate / tris (2-hydroxyethyl) isocyanurate tri (meth) acrylate of diol obtained by adding at least mole of ethylene oxide or propylene oxide, trimethylol Propane tri (meth) acrylate, pentaerythritol tri (meth) acrylate /
Dipentaerythritol poly (meth) acrylate /
Caprolactone-modified tris [(meth) acryloxyethyl] isocyanurate, alkyl-modified dipentaerythritol poly (meth) acrylate, caprolactone-modified dipentaerythritol poly (meth) acrylate / hydroxypivalic acid neopentyl glycol diacrylate, caprolactone-modified hydroxy Pivalic acid neopentyl glycol diacrylate / ethylene oxide modified phosphoric acid (meth) acrylate, ethylene oxide modified alkylated phosphoric acid (meth) acrylate and the like can be mentioned.

Further, N-vinyl-2-pyrrolidone, acryloylmorpholine, vinylimidazole, N-vinylcaprolactam, vinyl acetate, (meth) acrylic acid,
(Meth) acrylamide, N-hydroxymethyl acrylamide or N-hydroxyethyl acrylamide, and their alkyl ether compounds can also be used. Further, as the one which can be used in the same manner as the polymerizable monomer,
Examples of the polymerizable oligomer include polyester acrylate, polyether acrylate, epoxy acrylate, urethane acrylate and the like.

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 its derivative is included in the composition to improve the hardness. To get more
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 UV curable composition is 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 layer side is adhered to each other, but the exposed information recording layer may be adhered directly, or a protective coat layer for protecting the exposed surface of the information recording layer may be provided thereon. Alternatively, the protective coat layers may be adhered 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 ultraviolet curable composition for the protective coat layer is preferably prepared so as to have excellent adhesiveness to both the exposed surface of the information recording layer and the cured product of the ultraviolet curable composition for adhering the discs to each other. .

In the composition of the present invention, if necessary, other additives such as thermal polymerization inhibitors, antioxidants represented by hindered phenols, hindered amines, phosphites, plasticizers and 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 standard in this case, it is premised that the alteration of the information recorded in the information recording layer, that is, no abnormalities in the pits are generated. For example, the components in the composition are crystallized under the application temperature condition. That it does not undergo phase separation or has a very high wettability for both of the two surfaces to be bonded, and has a leveling property that gives a smooth and uniform wet surface in a short time, The two surfaces to be bonded do not contain substances or ions that cause corrosion or deterioration as much as possible, the composition before curing has a certain degree of viscous adhesiveness even in a liquid state, and a gas that contributes to curing inhibition The solubility of the composition is as small as possible, the composition has transparency to transmit ultraviolet rays as much as possible before and after curing, and between the cured adhesive layer 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 uses a continuous light irradiation, which is generally widely used, as an ultraviolet irradiation method for curing, in addition to the amount of irradiation light required for curing by conventional continuous light irradiation. The same or smaller amount of light, 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 surface of the opposed disk, but it may be performed from both surfaces.

The composition of the present invention is used in a method for producing a digital video disk, such as DVD-5 and 10, in which two thin film substrates of a disk substrate having an information recording thin film laminated on a heat-resistant thermoplastic resin are used. It is particularly effective for adhesion, or for adhesion between a disk substrate in which a heat-resistant thermoplastic resin is laminated with an information recording thin film and a disk substrate in which a heat-resistant thermoplastic resin is laminated with a designable metal thin film. .

In this case, after the substrates are opposed to each other,
Usually, ultraviolet rays are irradiated from the heat-resistant thermoplastic resin side of the disk substrate in which the information recording thin film is laminated on the heat-resistant thermoplastic resin to cure and bond the composition of the present invention between the thin films.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described. First, two disk-shaped plastic substrates having metal thin films of 400 to 600 angstrom laminated are prepared.

Then, a polyfunctional (meth) acrylate having two or more (meth) acryloyl groups is used as an essential component and a main component, and if necessary, a polymerizable monomer is also used, and a region of 370 nm or more as a photopolymerization initiator is used. Has an absorption wavelength in the wavelength range from 370 nm to 450 nm,
A composition having a molar extinction coefficient of 50 (l / mol cm) or more is used in an amount of 2 to 7 parts by weight based on 100 parts by weight of the liquid ultraviolet-curable composition.

The composition is applied to the metal thin film surface of the substrate, the metal thin film surfaces are bonded to each other, and then ultraviolet rays are radiated from the plastic substrate surface to bond the two to form a DVD.

[0032]

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 Obtained by reacting 40 parts of neopentyl glycol diacrylate, 30 parts of trimethylolpropane triacrylate, 1 mol of polytetramethylene glycol (molecular weight 850) with 2 mol of tolylene diisocyanate and 2 mol of hydroxyethyl acrylate. Urethane acrylate 2
6 parts, 4 parts of 2,4,6-trimethylbenzoyldiphenylphosphine oxide as a photopolymerization initiator at 60 ° C.
After mixing and dissolving for a period of time, a light yellow transparent UV-curable composition was prepared. Using this composition, the curability was evaluated by the following test method. As a result, the composition was cured at a conveyor speed of 3 m / min (irradiation light amount of about 230 mJ / cm ² ).

<Test method> Aluminum having a thickness of 500 angstroms was formed as a metal thin film, and the diameter was 12c.
Two disc-shaped polycarbonate substrates of m were prepared, 1
The above composition was applied to one sheet with a dispenser, and then another substrate was overlaid. The coating amount is such that when the composition is pushed and spread only by the weight of the substrate, the film thickness of the composition is 20 to
It was set to 50 μm. Next, irradiation intensity 55mW / c
The curability was evaluated using a belt conveyor type ultraviolet irradiation device equipped with a concentrating metal halide lamp (with a cold mirror, lamp output 80 W / cm) adjusted to m ² .

Example 2 The polymerizable component was the same as in Example 1 above, and bis (2,6-dimethoxybenzoyl) -2,4 as a photopolymerization initiator.
4 parts of a mixture of 4-trimethylpentylphosphine oxide and 1-hydroxy-cyclohexyl-phenyl ketone (CGI-1800 manufactured by Ciba-Geigy) was mixed and dissolved at 60 ° C. for 1 hour to prepare a light yellow transparent UV-curable composition. The curability was evaluated by the same test method as in Example 1, and as a result, the conveyor speed was 3 m / min (irradiation light amount was about 23
It was cured at 0 mJ / cm ² ).

Example 3 The polymerizable component was the same as in Example 1 above, and 4 parts of 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 was used as a photopolymerization initiator. The mixture was mixed and melted at 0 ° C. for 1 hour to prepare a light yellow transparent UV-curable composition. Curability was evaluated by the same test method as in Example 1, and as a result, curing was performed at a conveyor speed of 6 m / min (irradiation light amount of about 110 mJ / cm ² ).

The photopolymerization initiators of Examples 1 to 3 all have an absorption wavelength in the region of 370 nm or more and have a molar absorption coefficient of 500 (l / mo) at 370 to 450 nm.
l cm) or more.

Comparative Example 1 The polymerizable component was the same as in Example 1 above, and 4 parts of 1-hydroxy-cyclohexyl-phenylketone as a photopolymerization initiator was mixed and dissolved at 60 ° C. for 1 hour to obtain a light yellow transparent UV curing. A mold composition was prepared.

The curability was evaluated by the same test method as in Example 1. As a result, it was not cured although it was irradiated with 2 passes (irradiation light amount of about 1300 mJ / cm ² ) at a conveyor speed of 1 m / min.

Comparative Example 2 The polymerizable component was the same as in Example 1 above, and 2,2-dimethoxy-1,2-diphenylethane- was used as a photopolymerization initiator.
4 parts of 1-one was mixed and dissolved at 60 ° C. for 1 hour to prepare a pale yellow transparent UV-curable composition.

The curability was evaluated by the same test method as in Example 1. As a result, it was not cured even though it was irradiated with 2 passes (irradiation light amount of about 1300 mJ / cm ² ) at a conveyor speed of 1 m / min.

The compositions of Examples 1 to 3 were all suitable as an ultraviolet curable composition used as a bonding type adhesive for DVD.

[0043]

By using the composition of the present invention,
Even if the two discs both have a metal thin film or a layer that does not transmit ultraviolet rays very much, efficient curing and adhesion can be performed, and a significant increase in the productivity of a DVD using the laminating method can be realized.

Claims (5)

[Claims] 1. An ultraviolet-curable composition is used as an adhesive for bonding two discs each having an information recording layer to at least one disc, and 3 is used as a photopolymerization initiator.
An ultraviolet-curable composition, characterized in that one having an absorption wavelength in a region of 70 nm or more is used. 2. The molar extinction coefficient is 50 (l / mol c in the wavelength region of 370 nm to 450 nm of the photopolymerization initiator).
The ultraviolet-curable composition according to claim 1, which has a point of m) or more. 3. The molar extinction coefficient is 500 (l / mol) in the wavelength region of 370 nm to 450 nm of the photopolymerization initiator.
cm) or more.
The ultraviolet curable composition as described above. 4. An ultraviolet-curable composition comprising 0.1 to 10 parts of the photopolymerization initiator according to claim 1, 2 or 3. 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.