JPH09251670A - Optical information desk - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deformation of a disk, such as warpage, by a temp. changely using a UV curing adhesive having the coefft. of thermal expansion of a specific value and specifying the thickness of the adhesive layer. SOLUTION: This optical information disk has a metal hub adhered by the UV curing adhesive. The UV curing adhesive of the optical information disk contains one or plural kinds of monomers and/or oligomers having (meth) acrylate structures and at least one kind of photoinitiators. The coefft. of thermal expansion of the cured matter of the UV curing adhesive is 2x10<-5> to2x10<-4> /k. The thickness after curing of the adhesive layer interposed between the disk and the metal hub is >=5μm.

Description

Detailed Description of the Invention

[0001]

[0001] The present invention relates to a magneto-optical disk,
The present invention relates to an optical information disc that records, reproduces, or erases information by using light from an optical disc or the like, and particularly relates to improvement of an optical information disc having a metal hub bonded with an ultraviolet curable adhesive.

[0002]

2. Description of the Related Art A magnet clamp method is widely used as a method for loading an optical information disk for recording, reproducing or erasing information using light from a magneto-optical disk, an optical disk or the like into a drive device.

In this system, a center hub is provided at the center of the disk, and the center hub is attracted and held by a permanent magnet provided on the drive unit side.

Attempts have been made to use a metal hub made of only metal as the center hub. However, due to the difference in coefficient of thermal expansion between the substrate material resin such as polycarbonate and the metal, the temperature within the operating environment temperature of the optical information disk is considered. Even in the difference, there was a defect that the warp of the disk occurred.

In order to solve the above problems, a metal insert hub in which a part of a metal plate is embedded in a resin and integrally molded is generally used as a center hub.

However, the metal insert hub has a problem that the process is complicated and the manufacturing cost is high because it is necessary to process a metal plate in advance into a shape suitable for embedding and integrally mold this with resin. There is.

[0007]

The present invention pays attention to such a problem, reduces the generation of stress due to the temperature change due to the difference in the thermal expansion coefficient between the resin substrate and the metal hub, and reduces the disk temperature within the operating environment temperature. The objective is to develop an optical information disc that does not warp.

[0008]

In order to solve the above problems, the present inventor has conducted diligent studies and, as a result, found that an ultraviolet curable adhesive for adhering a disk and a metal hub is The coefficient of thermal expansion of
2 × 10 ^-5 / K or more and 2 × 10 ^-4 / K or less so that it is larger than the coefficient of thermal expansion of stainless steel used as a metal hub and smaller than the coefficient of thermal expansion of polycarbonate and polymethylmethacrylate which are substrate materials. By using the adhesive of which the thickness is 5 μm or more, the stress caused by the temperature change caused by the difference in the thermal expansion coefficient between the resin substrate and the metal hub is relaxed, and the warp of the disk is prevented. They have found that they can be suppressed, and have completed the present invention.

That is, the optical information disk of the present invention is an optical information disk having a metal hub adhered by an ultraviolet curable adhesive, wherein the ultraviolet curable adhesive is 1
One or more kinds of monomers and / or oligomers having a (meth) acrylate structure and at least one photoinitiator, and the cured product thereof has a thermal expansion coefficient of 2 × 10.
⁻⁵ / K or more and 2 × 10 ⁻⁴ / K or less, and the cured adhesive layer interposed between the disc and the metal hub has a thickness of 5 μm or more. The coefficient of thermal expansion referred to in the present specification indicates a coefficient of linear expansion.

The thermal expansion coefficient of the cured product is 2 × 10 ^-5 /
Ultraviolet rays in the present invention which are not less than K and not more than 2 × 10 ⁻⁴ / K, and which contain one or more kinds of monomers and / or oligomers having a (meth) acrylate structure and at least one kind of photoinitiator. The curable adhesive is a hydroxyl group, a carboxylic acid group, for the purpose of improving the adhesiveness with a metal.
It is preferable to contain at least one kind of (meth) acrylate or metal (meth) acrylate having a phosphoric acid group, a phosphoric acid ester group or a sulfonic acid group.

The reason why the thickness of the adhesive layer after curing is 5 μm or more is to allow the stress due to thermal expansion to be sufficiently relaxed, but in order to obtain a more sufficient effect, the adhesive layer is cured. It is further preferable that the subsequent thickness is 10 μm or more.

As a method for increasing the thickness of the adhesive layer to 5 μm or more, a method achieved by adjusting the amount of adhesive applied and the pressure of the metal hub can be used. It is also possible to use a method of maintaining the thickness of the adhesive by forming a void having a predetermined thickness in the bonded portion.

Examples of the resin substrate material in the present invention include polycarbonate, polymethylmethacrylate and amorphous polyolefin.

Further, as the metal hub in the present invention, stainless steel SU specified in JIS G4303 is used.
Any material having S430 or magnetic characteristics equivalent to S430 can be used without any problem.

As the (meth) acrylate having a hydroxyl group in the present invention, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, triethylene glycol monoacrylate, triethylene glycol monomethacrylate,
Tetraethylene glycol monoacrylate, tetraethylene glycol monomethacrylate, pentaethylene glycol monoacrylate, pentaethylene glycol monomethacrylate, hexaethylene glycol monoacrylate, hexaethylene glycol monomethacrylate, heptaethylene glycol monoacrylate,
Heptaethylene glycol monomethacrylate, octaethylene glycol monoacrylate, octaethylene glycol monomethacrylate, nonaethylene glycol monoacrylate, nonaethylene glycol monomethacrylate, 2-hydroxypropyl acrylate, 2
-Hydroxypropyl methacrylate, dipropylene glycol monoacrylate, dipropylene glycol monomethacrylate, tripropylene glycol monoacrylate, tripropylene glycol monomethacrylate, tetrapropylene glycol monoacrylate, tetrapropylene glycol monomethacrylate, pentapropylene glycol monoacrylate, pentapropylene glycol Monomethacrylate, 2-hydroxy-
Examples include 3-phenoxypropyl acrylate and 2-hydroxybutyl acrylate.

As the (meth) acrylate having a carboxylic acid group in the present invention, 2-acryloyloxyethyl malonic acid, 2-methacryloyloxyethyl malonic acid, 2-acryloyloxyethyl succinic acid, 2-methacryloyloxyethyl succinic acid, 2-acryloyloxyethyl glutaric acid, 2-methacryloyloxyethyl glutaric acid, 2-acryloyloxyethyl phthalic acid, 2-methacryloyloxyethyl phthalic acid, 2-acryloyloxypropyl phthalic acid, 2-methacryloyloxypropyl phthalic acid, 2- Acryloyloxypropyl hexahydrophthalic acid, 2-acryloyloxypropyl tetrahydrophthalic acid and the like are exemplified.

The (meth) acrylate having a phosphoric acid group or a phosphoric acid ester group in the present invention includes mono (2
-Acryloyloxyethyl) acid phosphate, mono (2-methacryloyloxyethyl) acid phosphate, di (2-acryloyloxyethyl)
Examples include acid phosphate, diphenyl (2-acryloyloxyethyl) phosphate, diphenyl (2-methacryloyloxyethyl) phosphate, phenyl (2-acryloxyethyl) phosphate.

Examples of the (meth) acrylate having a sulfonic acid group in the present invention include 2-sulfoethyl acrylate, 2-sulfoethyl methacrylate, 3-sulfopropyl acrylate and 3-sulfopropyl methacrylate.

Further, the metal (meta) used in the present invention
Examples of the acrylate include acrylates and methacrylates of metals such as lithium, sodium, potassium, magnesium, calcium, strontium, barium, manganese, iron, cobalt, nickel, copper, silver, zinc, aluminum, tin and lead.

These (meth) acrylates added for the purpose of improving the adhesiveness with the metal hub may be used alone or as a mixture of two or more kinds as long as the compatibility of the resins is not impaired. good.

The amount of the (meth) acrylate added for the purpose of improving the adhesiveness with the metal hub is preferably 10% by weight or more in order to obtain a sufficient improvement in the adhesive strength with the metal, and the curing is performed. It is preferably 80% by weight or less so as to maintain the toughness of the subsequent resin and prevent the resin from becoming brittle and failing to satisfy the properties as the adhesive for a metal hub.

The UV curable adhesive in the present invention includes
In addition to the above-mentioned (meth) acrylate for improving the adhesiveness with a metal, a monofunctional or polyfunctional (meth) acrylate may be mixed for the purpose of improving the adhesiveness with a resin substrate. A crosslinkable (meth) acrylate oligomer may be mixed for the purpose of improving

The monofunctional or polyfunctional (meth) acrylates added for the purpose of improving the adhesiveness to the resin substrate in the present invention include isoamyl acrylate, isoamyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, Isooctyl acrylate, isooctyl methacrylate, benzyl acrylate, benzyl methacrylate, butoxyethyl acrylate, butoxyethyl methacrylate, phenoxyethyl acrylate,
Phenoxyethyl methacrylate, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, ethoxydiethylene glycol acrylate, methoxytriethylene glycol acrylate, triethylene glycol diacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate ,
1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, ethylene oxide modified trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol trimethacrylate, dipentaerythritol hexaacrylate, pentaerythritol tetraacrylate , Neopentyl glycol acrylate benzoate, trimethylolpropane acrylate benzoate, and the like.

This monofunctional or polyfunctional (meth) acrylate may be used alone or in combination of two or more.

In order to obtain the required adhesive strength with the metal, in order to secure the addition amount of the above-mentioned (meth) acrylate of 10% by weight or more for the purpose of improving the adhesiveness with the metal, the above monofunctional Alternatively, the amount of polyfunctional (meth) acrylate added is preferably 90% by weight or less.

Further, typical examples of the crosslinkable (meth) acrylic oligomer added for the purpose of improving toughness in the present invention include polyester (meth) acrylate, polyether (meth) acrylate, polyurethane (meth) acrylate, Examples thereof include epoxy (meth) acrylate, and more specifically, polyurethane diacrylate, polyurethane dimethacrylate, spiroglycol urethane diacrylate, spiroglycol urethane dimethacrylate, bisphenol A type epoxy acrylate, bisphenol A type epoxy methacrylate, Bisphenol F type epoxy acrylate,
Examples thereof include bisphenol F type epoxy methacrylate, phenol novolac type epoxy acrylate, phenol novolac type epoxy methacrylate, cresol novolac type epoxy acrylate, and cresol novolac type epoxy methacrylate.

These (meth) acrylates are useful as crosslinkable oligomers having high practicality, but in addition to these, resins such as unsaturated polyester, polysulfone, polyethersulfone and polyphenylene oxide are modified with (meth) acrylic acid ester. You can also use the ones you used.

The molecular weight of the crosslinkable oligomer used in the present invention can be used in a fairly wide range, but a molecular weight of 200 to 50,000 is preferable.

These crosslinkable oligomers may be used alone or in combination of two or more.

The addition amount of the crosslinkable oligomer in the present invention is 50% by weight so that the resin does not become too viscous by the addition and it becomes difficult to quantitatively discharge the resin necessary for attaching the hub. The following is preferable.

The light-curable monomers and oligomers used in the present invention may be acrylates or methacrylates to form the ultraviolet-curable adhesive in the present invention, but the acrylates have different curing speeds due to ultraviolet rays. It is more practical to be composed of monomers and oligomers.

It is necessary to add at least one kind of photoinitiator to the ultraviolet curable adhesive in the present invention in order to cure it by ultraviolet rays.

As the photoinitiator in the present invention, 1-hydroxycyclohexyl phenyl ketone, benzophenone, thioxanthone, alkylthioxanthone, 2,2
-Dimethoxy-2-phenylacetophenone, 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butan-1-one, 2,2-dimethoxy-
1,2-diphenylethan-1-one, diethoxyacetophenone, 4-dimethylaminoacetophenone, 4-
Diethylaminobenzophenone, 4,4'-tetramethylaminobenzophenone, 4,4'-tetraethylaminobenzophenone, methylbenzoyl formate, 4
Examples include ethyl dimethylaminobenzoate, propyl 4-dimethylaminobenzoate, isoamyl 4-dimethylaminobenzoate, ethyl 4-diethylaminobenzoate, propyl 4-diethylaminobenzoate, isoamyl 4-diethylaminobenzoate, and the like. These photoinitiators can be used alone or in combination.

The amount of the photoinitiator added in the present invention is preferably 0.1% by weight or more in order to obtain an effective photoinitiating effect, and the adhesive due to the decrease in the three-dimensional crosslink density of the adhesive after curing is used. 10 not to cause insufficient strength
% By weight or less.

The UV-curable adhesive in the present invention contains hydroquinone monomethyl ether, t-butyl catechol, p-benzoquinone and 2,5-t-butyl in order to prevent thermal polymerization during production and dark reaction during storage. It is preferable to add a known thermal polymerization inhibitor such as hydroquinone or phenithiazine.

Further, at least one kind of leveling agent may be added to the adhesive for the purpose of imparting a uniform coating property and suppressing the occurrence of coating defects. Silicone-based surfactants and fluorine-based surfactants are generally known as the leveling agents, and the addition amount thereof is usually 0.01 to 3% by weight based on the adhesive.

Further, a coupling agent such as a silane-based coupling agent, a titanium-based coupling agent, an indium-based coupling agent, or an aluminum-based coupling agent may be added alone or in combination for the purpose of further improving the adhesiveness to the metal hub.

The above-mentioned UV-curable adhesive containing these (meth) acrylate and a photoinitiator has a thermal expansion coefficient of 2 × 10 ⁻⁵ / K or more and 2 × when the cured product cured by irradiation with ultraviolet rays. It must be less than 10 ^-4 / K.

[0039]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

(Example 1) 15 g of 2-hydroxyethyl acrylate, 10 g of di (2-acryloyloxyethyl) acid phosphate, 20 g of tetrahydrofurfuryl acrylate, 5 g of 1,6-hexanediol diacrylate and 20 g of trimethylolpropane triacrylate , Spiroglycol urethane acrylate 20
g and 10 g of zinc diacrylate were mixed to prepare an adhesive base resin.

5 g of 4-dimethylaminoacetophenone and 5 g of benzophenone based on the total amount of this base resin
Was added and mixed well to prepare an ultraviolet curable adhesive.

10 g of this UV-curable adhesive was applied on a Teflon plate, and an integrated irradiation dose of 7,000 mJ / c was applied from above.
After curing by irradiation with ultraviolet rays of m ² (λ = 365 nm), the cured product was removed from the Teflon plate, cut into a predetermined shape, and the thermal expansion coefficient of the cured product was measured. Table 1 shows the measurement results
Shown in

A diameter of 8 g of 1.5 g of this UV-curable adhesive was used.
Apply to a 6 mm polycarbonate magneto-optical disk,
Metal hub for magneto-optical disk made by Kato Spring (SUS
430) was adhered by UV irradiation. The cumulative irradiation dose of ultraviolet rays at this irradiation is 7,000 mJ / cm ² (λ = 36
5 nm).

With respect to the magneto-optical disk with a metal hub thus manufactured, a mechanical property measuring device manufactured by Ono Sokki Co., Ltd. under the trade name of "LM-" at 23 ° C and 60 ° C.
The warp angle of the disk was measured using "100". The measurement results are also shown in Table 1.

Then, the disc after the measurement was cut, and the thickness of the adhesive layer between the metal hub and the substrate was measured using a scanning electron microscope. The measurement results are also shown in Table 1.

[0046]

[Table 1]

(Embodiment 2) A magneto-optical disk with a metal hub was prepared in the same manner as in Embodiment 1 except that 2.0 g of the ultraviolet curable adhesive prepared in Embodiment 1 was used to bond the metal hub to the magneto-optical disk. A disk was prepared and the warp angle of the disk and the thickness of the adhesive layer were measured in the same manner as in Example 1. The measurement results are also shown in Table 1.

Example 3 15 g of 2-hydroxyethyl acrylate, 10 g of 2-acryloyloxyethyl phthalic acid, 20 g of tetrahydrofurfuryl acrylate,
Adhesive base resin was prepared by mixing 5 g of 1,6-hexanediol diacrylate, 20 g of pentaerythritol tetraacrylate, 20 g of polyurethane diacrylate and 10 g of zinc diacrylate.

To the total amount of this base resin, 5 g of methylbenzoyl formate and 5 g of benzophenone were added and mixed well to prepare an ultraviolet-curable adhesive.

With respect to the ultraviolet-curable adhesive thus prepared, the thermal expansion coefficient of the cured product was measured in the same manner as in Example 1. Table 1 shows the measurement results.

A magneto-optical disk with a metal hub was produced in the same manner as in Example 1 except that 1.5 g of this ultraviolet-curable adhesive was used, and the warp angle of the disk and the adhesive layer were prepared in the same manner as in Example 1. Was measured. Table 1 shows the measurement results
Shown along with.

(Example 4) A magneto-optical disk with a metal hub was prepared in the same manner as in Example 1 except that 2.0 g of the ultraviolet curable adhesive prepared in Example 3 was used. Then, the warp angle of the disk and the thickness of the adhesive layer were measured. The measurement results are also shown in Table 1.

Example 5 15 g of 2-hydroxyethyl acrylate, 10 g of 2-acryloyloxyethyl malonic acid, 20 g of tetrahydrofurfuryl acrylate,
10 g of neopentyl glycol diacrylate, 15 g of trimethylolpropane triacrylate, 20 g of spiroglycol urethane diacrylate and 10 g of aluminum triacrylate were mixed to prepare an adhesive base resin.

Based on the total amount of this base resin, 5 g of methylbenzoyl formate, 5 g of benzophenone and γ
-2 g of methacryloxypropyltrimethoxysilane was added and mixed well to prepare a UV-curable adhesive.

With respect to the ultraviolet curable adhesive thus prepared, the thermal expansion coefficient of the cured product was measured in the same manner as in Example 1. Table 1 shows the measurement results.

A magneto-optical disk with a metal hub was prepared in the same manner as in Example 1 except that 1.5 g of this ultraviolet-curable adhesive was used, and the warp angle of the disk and the adhesive layer were prepared in the same manner as in Example 1. Was measured. Table 1 shows the measurement results
Shown along with.

(Example 6) 15 g of 2-hydroxyethyl acrylate, 10 g of 2-acryloyloxyethyl malonic acid, 20 g of tetrahydrofurfuryl acrylate,
10 g of neopentyl glycol diacrylate, 15 g of trimethylolpropane triacrylate, 20 g of spiroglycol urethane diacrylate and 10 g of aluminum triacrylate were mixed to prepare an adhesive base resin.

5 g of methylbenzoyl formate, 5 g of benzophenone and 2 g of tetraisopropyl titanate were added to the total amount of the base resin and mixed well,
A UV curable adhesive was prepared.

With respect to the ultraviolet curable adhesive thus prepared, the thermal expansion coefficient of the cured product was measured in the same manner as in Example 1. Table 1 shows the measurement results.

A magneto-optical disk with a metal hub was prepared in the same manner as in Example 1 except that 1.5 g of this ultraviolet-curable adhesive was used, and the warp angle of the disk and the adhesive layer were prepared in the same manner as in Example 1. Was measured. Table 1 shows the measurement results
Shown along with.

Comparative Example 1 25 g of 2-hydroxyethyl acrylate, 10 g of 2-acryloyloxyethyl phthalic acid, 20 g of tetrahydrofurfuryl acrylate,
An adhesive base resin was prepared by mixing 5 g of 1,6-hexanediol diacrylate, 20 g of pentaerythritol tetraacrylate and 20 g of polyurethane diacrylate.

5 g of 4-dimethylaminoacetophenone and 5 g of benzophenone based on the total amount of this base resin
Was added and mixed well to prepare an ultraviolet curable adhesive.

With respect to the ultraviolet-curable adhesive thus prepared, the thermal expansion coefficient of the cured product was measured in the same manner as in Example 1. Table 1 shows the measurement results.

A magneto-optical disk with a metal hub was prepared in the same manner as in Example 1 except that 0.2 g of this ultraviolet-curable adhesive was used, and the warp angle of the disk and the adhesive layer were prepared in the same manner as in Example 1. Was measured. Table 1 shows the measurement results
Shown along with.

(Comparative Example 2) 15 g of 2-hydroxyethyl acrylate, 10 g of 2-acryloyloxyethyl phthalic acid, 20 g of tetrahydrofurfuryl acrylate,
Adhesive base resin was prepared by mixing 5 g of 1,6-hexanediol diacrylate, 20 g of pentaerythritol tetraacrylate, 20 g of polyurethane diacrylate and 10 g of zinc diacrylate.

To the total amount of this base resin, 5 g of methylbenzoyl formate and 5 g of benzophenone were added and mixed well to prepare an ultraviolet-curable adhesive.

With respect to the ultraviolet-curable adhesive thus prepared, the thermal expansion coefficient of the cured product was measured in the same manner as in Example 1. Table 1 shows the measurement results.

A magneto-optical disk with a metal hub was produced in the same manner as in Example 1 except that 0.2 g of this ultraviolet-curable adhesive was used, and the warp angle of the disk and the adhesive layer were prepared in the same manner as in Example 1. Was measured. Table 1 shows the measurement results
Shown along with.

[0069]

The optical information disk of the present invention contains the monomer and / or oligomer having the (meth) acrylate structure and the photoinitiator as described above, and the thermal expansion coefficient of the cured product thereof is that of the metal hub. Since a UV curable adhesive that is larger and smaller than the thermal expansion coefficient of the resin substrate is used, the adhesiveness between the adhesive and the metal hub or the disk is excellent. In particular, by using the adhesive with a thickness of 5 μm or more, It is possible to prevent deformation of the disk such as warpage due to temperature change, and it is possible to put the metal hub into practical use.

Claims (6)

[Claims] 1. An optical information disk having a metal hub bonded by an ultraviolet curable adhesive, wherein the ultraviolet curable adhesive comprises one or more kinds of monomers and / or oligomers having a (meth) acrylate structure,
Adhesion containing at least one photoinitiator, the cured product of which has a thermal expansion coefficient of 2 × 10 ⁻⁵ / K or more and 2 × 10 ⁻⁴ / K or less, and which is interposed between the disc and the metal hub. An optical information disc, wherein the thickness of the agent layer after curing is 5 μm or more. 2. The ultraviolet-curable adhesive contains a (meth) acrylate having a hydroxyl group.
Optical information disc described in. 3. The optical information disc according to claim 1, wherein the ultraviolet curable adhesive contains (meth) acrylate having a carboxylic acid group. 4. The optical information disc according to claim 1, wherein the ultraviolet-curable adhesive contains a (meth) acrylate having a phosphoric acid group or a phosphoric acid ester group. 5. The optical information disc according to claim 1, wherein the ultraviolet curable adhesive contains a (meth) acrylate having a sulfonic acid group. 6. The optical information disc according to claim 1, wherein the ultraviolet curable adhesive contains a metal (meth) acrylate.