JPS626448A - Optical memory element - Google Patents

Abstract

PURPOSE:To improve the moisture resistance of both surfaces after adhesion by using an adhesive agent to which an adhesiveness rendering agent having UV curability and thermosettability as well as water repellency is added. CONSTITUTION:Recording member layers 2 are formed on the surfaces of supporting bases 1 and after the adhesive agent 3 is coated over the entire surface having the layers 2, two sheets of the supporting base bodies are adhered in such a manner that the recording member layers face each other. UV rays are irradiated from one base side to cure and adhere a transparent buffer part 5 by the UV rays so that the recording members are adhered by the ther mosettability. The adhesive agent to which the adhesiveness rendering agent having the UV curability and thermosettability as well as the water repellency is added is used. At least one kind of the silane coupling agent or titanium coupling agent having the water repellency is isued as an additive for improving the adhesiveness preferably at 2-5pts. by the weight of the adhesive agent. The moisture resistance of the optical memory element is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to an optical memory element that records, reproduces, erases, etc. information using light such as a laser.

<Prior Art> In recent years, research and development of optical memory devices has been actively conducted as demand for memory devices capable of large capacity, high density, and high speed access has been increasing.

In optical memory devices, an optical memory medium is formed on a substrate made of synthetic resin such as glass or acrylic resin, and the medium forming surfaces are bonded together so that they face each other in order to protect them from disturbances such as scratches, dirt, and chips. , it is common to have a configuration that allows both sides to be used. Also, memory (
In some cases, a substrate on which a memory (memory) medium is formed and a substrate on which no storage medium is formed are bonded together so that the storage medium is sandwiched between the two substrates. In this case, in order to avoid oxidation and corrosion of the medium from the peripheral area exposed to the outside air, it is necessary to form a buffer section from which the medium in the peripheral area is removed.

By the way, the following two methods are widely known for forming the optical memory element. One is a method in which only the buffer section is bonded together via a spacer, and an inert gas or the like is filled between the two substrates (air sandwich structure). However, with this method, the bonding process becomes complicated, and in order to ensure mechanical strength after bonding, the area of the bonded area must be as large as possible. A reduction in storage capacity is an unavoidable drawback.

Another method is to attach the entire surface with adhesive.

With this method, the above problem can be avoided. In this case, ultraviolet curing adhesives are widely used as adhesives because they are liquid-based, require a long oven time (time from applying the adhesive to bonding), and are advantageous in terms of workability. In this case, since UV rays do not easily pass through the medium forming parts, which are mainly made of metal, it is necessary to use, for example, a thermosetting UV curing adhesive to complete the adhesive curing between the medium forming parts. be. Examples of such adhesives include, for example, those prepared by appropriately blending an acrylic urethane oligomer with a cut monomer, a photoinitiator, a stabilizer, and the like, in addition to which an organic peroxide is added as a thermosetting agent.

On the other hand, many of the materials that make up the storage medium of optical memory devices have characteristics that deteriorate due to oxidation, and corrosion is particularly likely to progress rapidly due to the presence of moisture, so improving the moisture resistance of the device is an unavoidable issue for practical application. It becomes. However, with the above-mentioned sealing technology based on conventional adhesives, depending on the storage environment such as high temperature and high humidity, the adhesive itself absorbs moisture, swells, peels from the substrate, and decreases adhesion, resulting in leakage through the interface. The problem of accelerating moisture intrusion and causing corrosion of the storage medium was unavoidable.

<Purpose> The present invention was made in order to improve the above-mentioned conventional technology, and it adds a water-repellent adhesion agent to a conventional ultraviolet curable adhesive that has been given thermosetting properties, and is particularly suitable for double-sided adhesives. It is an object of the present invention to provide an optical memory element that has enhanced moisture resistance and enhanced reliability.

<Structure> The present invention provides an optical memory element in which an optical memory medium is formed on a substrate and then the substrate and another substrate without an optical memory medium or a substrate on which an optical memory medium is formed are bonded together with an adhesive sandwiching the optical memory medium. The present invention relates to an optical memory element, characterized in that the adhesive is an adhesive having ultraviolet curability and thermosetting properties, and to which an adhesion imparting agent having water repellency is added.

The optical memory medium to which the present invention is applied is a medium that is easily corroded by the atmosphere or moisture, such as a Te thin film, a Te lower oxide thin film, a dye thin film, a rare earth-transition metal alloy amorphous thin film, and the like. Examples of rare earth-transition metal alloy amorphous thin films include GdTbFe thin films shown in Examples later, as well as T b
Examples include D yF e-based thin films. Optical memory elements constructed using these optical memory media are made up of two
Although the structure is such that an optical memory medium is sandwiched between two substrates, the optical memory medium may have two layers as in the embodiment, or may have one layer.

The adhesive used in the present invention is an ultraviolet curable adhesive that has been given thermosetting properties as described above, and further has an adhesion imparting agent added thereto.

For example, acrylic urethane oligomer is used as the adhesive. Examples of acrylic urethane oligomers include polyester urethane (meth)acrylate, polyether urethane (meth)acrylate, polybutadiene (meth)acrylate, and the like.

Polyester urethane (meth)acrylate is obtained by reacting polyester polyol and polyisocyanate, and then reacting with β-hydroxyl group-containing (meth)acrylate. Polyols used in the preparation of polyester polyols include ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol, diethylene glycol, and the like. Examples of polycarboxylic acids that react with polyols include aliphatic polycarboxylic acids such as malonic acid, adipic acid, geltanic acid, maleic acid, fumaric acid, etc.; aromatic polycarboxylic acids such as phthalic acid, terephthalic acid, etc.; Examples include sensuality and other damaged items. The hydroxyl value of the polyester polyol is usually preferably 20 to 200.

Examples of polyisocyanates that react with one hydroxyl group of a polyester polyol include trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,2-propylene diisocyanate, and 1.2-hexamethylene diisocyanate.
- Aliphatic compounds such as butylene diisocyanate, 2,3-butylene diisocyanate, 1, 3-butylene diisocyanate, ethyridine diisocyanate and butylidene diisocyanate;
Cycloalkylene compounds such as 4-cyclohexane diisocyanate and 1,2-cyclohexane diisocyanate; Aromatic compounds such as: 4,4'-diphenylenemethane diisocyanate, 2,4- or 2,6-dolylene diisocyanate, or mixtures thereof, 4,4'-toluinone diisonanate and 1,4-xylylene diisocyanate. Aliphatic-aromatic compounds such as isocyanates; or nuclear-substituted aromatic compounds such as dianisidine diisocyanate, 4'4'-diphenyl ether diisocyanate and chlorodiphenyl diisocyanate, and the like.

Although one isocyanate group is used for the urethane bond by the above reaction, the other free isocyanate group is β-hydroxy (meth)acrylate, e.g. 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate. Polyester urethane (meth)acrylate is obtained by reacting with at least one of the following.

Polyether urethane (meth)acrylate as a pace oligomer is obtained by reacting the polyisocyanate with a polyether polyol having a hydroxyl value of 20 to 200, such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc., and then reacting the aforementioned β
- Obtained by reacting with hydroxy (meth)acrylate.

Further, polybutadiene (meth)acrylate is reacted with polybutadiene having a hydroxyl value of 20 to 200, such as polybutadiene having a hydroxyl group at the end, epoxy-modified polybutadiene, hydrogenated polybutadiene, etc., with the polyisocyanate, and then the aforementioned β-hydroxyalkyl (meth)acrylate is reacted with the polyisocyanate. ) Obtained by reacting with acrylate.

Organic peroxides or azo-based thermal polymerization initiators can be added to the thermosetting agent, but azo-based polymerization initiators generate nitrogen gas when decomposed, resulting in a decrease in adhesive strength after curing. Undesirable. It is preferable that the organic peroxide has a 10-hour half-life temperature of 60° C. or higher, and if an organic peroxide is used that has a 10-hour half-life temperature of 60° C. or lower, the pot life will be shortened. Organic peroxides that meet the above conditions have a 10-hour half-life temperature of 60°C and 80°C.
Examples of C include isononanoyl peroxide, lauroyl peroxide, benzoyl peroxide, tertiary-butyl-per-2-ethylhexanoate, 9
As those from 0°C to 110°C, 1.1-bis(tert-butylperoquine) 3°3.5-trimethylcyclohexane, tert-butyl peroxyisopropyl carbonate, tert-butyl peroxybenzoate, methyl ethyl ketone peroxide. , 115°
C-130°C, dicumyl peroxide,
Examples include tertiary-butyl hydroperoxide, di-tertiary-butyl peroxide, and cumene hydroperoxide which is heated at around 100°C. It is preferable to add 0.01 part to 1 part of at least one of the above materials to 30 to 80 parts by weight of the pace oligomer.

Hydroxyalkyl (meth)acrylate, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl, is added to 30 to 80 parts of the above acrylic urethane oligomer as a cut monomer that lowers the viscosity of the adhesive and improves surface workability. (meth)acrylate, and at least one alkyl (meth)acrylate, such as 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, etc., from 20 parts to Add 70 parts and add 0.1 to 10 parts, preferably 10 parts, of at least one of dimethyl benzyl ketal, benzoin ethyl ether, benzoin isopropyl ether, benzophenone, benzyl, etc. as a photosensitizer.
Part to 3 parts may be added.

In addition, hydroquinone, methoquinone,
At least one of ditertiary-butyl-p-cresol and the like is added to 0. 1 part to 0.5 part of O may be added.

Furthermore, as an additive for improving adhesion, which is a feature of the present invention, at least one of water-repellent silane coupling agents or titanium coupling agents is added to the adhesive in an amount of 0.5 to 1 part.
0 parts, preferably 2 to 5 parts are used. Silane coupling agents include vinyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, etc., and titanium coupling agents include diisopropoxybis(acetylacetonato)titanium, Examples include dihydroxypislactatotitanium.

The use of this adhesive dramatically improves the adhesion to the substrate, and prevents moisture absorption and swelling of the bonded area, which had previously been a problem under humidified conditions.
Problems such as peeling are also eliminated, and as a result, the moisture resistance of the optical memory element itself can be significantly improved.

<Example> Hereinafter, an example of the optical memory device according to the present invention will be described.
This will be explained in detail using drawings.

FIG. 1 is an external perspective view of an optical disk as an example of an optical memory element according to the present invention, and FIG. 2 is a partial side sectional view thereof. 1 is a support base made of glass or synthetic resin such as acrylic resin, 2 is a thin film of an optical recording member, 3 is an adhesive layer, 4 is a center hole, and 5 is a buffer portion from which the recording member is removed.

After forming the recording member layer 2 on the surface of the support base l and applying the adhesive 3 to the entire surface on which the recording member layer 2 is to be formed, the two support bases are bonded together with the recording member layers facing each other. The transparent buffer portion 5 is bonded by UV curing by irradiating ultraviolet rays from one substrate side, and the recording member portion is bonded by thermosetting.

Here, the effects will be explained by taking as an example a magneto-optical storage element that allows additional recording and erasing of information.

The magneto-optical memory element is made of amorphous GdT on a glass substrate.
A bFe memory thin film, an ACN derivative film, and an A12 reflective film are successively sputtered to form a laminated structure, which is then bonded together with an adhesive with the film surfaces facing each other.

In particular, the GdTbFe film layer is susceptible to oxidative corrosion, and a reliable sealing bonding method is desired for this type of memory element. In this example as well, the above-mentioned buffer section is provided around the element.

Here, the memory elements with various adhesives were prepared and subjected to a humidity resistance test. Environmental test conditions include temperature and humidity cycle test (cycles between -20°C and 70°C, 95.6% RH1 are repeated at a rate of 4 cycles per day), constant temperature,
Constant humidity test (60°C, 195% R,
) were performed respectively.

Conventional thermosetting ultraviolet curable adhesives have a hydroxyl value l containing ethylene glycol and adipic acid as constituent components.
25 parts of hydroxypropyl methacrylate and 20 parts of 2-ethylhexyl methacrylate were added as cut monomers to 55 parts of polyester urethane methacrylate as a base obtained by reacting a polyester polyol having IO with isophorone diisocyanate and hydroxyethyl methacrylate in the above-mentioned proportions. , further 1.
1-bis(tert-butylperoxy) 3゜3.5
- A mixture prepared by adding 0.4 parts of trimethylcyclohexane as a thermosetting agent, 2 parts of benzyl dimethyl ketal as a photosensitizer, and 0.02 parts of hydroquinone as a storage stabilizer was used. The thermosetting ultraviolet curable adhesive containing the adhesion agent according to the present invention was prepared by adding 4 parts of γ-methacryloxypropyltrimethoxysilane as an adhesion agent to the above adhesive composition. .

As a result of comparing the environmental test results of memory elements using these adhesives, it was found that the former had a cycle test and a constant temperature star test 1.
After about a week, wrinkle-like peeling appeared on the adhesive surface, which was thought to be due to swelling, whereas in the latter case, no abnormality was observed even after 3 weeks. Also, pre-sharkutsuka
In the test, the time when the peeling started to be seen was 6.
In contrast, in the latter case, it took more than 40 hours.

From the above examples, it can be seen that the moisture resistance of the memory element is definitely improved.

<Effects> According to the present invention, the moisture resistance of the optical memory element is significantly enhanced, so the reliability as a memory element is greatly improved.

[Brief explanation of the drawing]

FIG. 1 is an external perspective view showing a disk as an embodiment of an optical memory element according to the present invention, and FIG. 2 is a side sectional view showing a portion thereof.

Claims (1)

[Claims] 1. An optical memory in which an optical memory medium is formed on a substrate, and then the substrate and another substrate without an optical memory medium or a substrate on which an optical memory medium is formed are bonded with an adhesive with the optical memory medium sandwiched therebetween. An optical memory element, characterized in that the adhesive is an adhesive having ultraviolet curable properties and thermosetting properties, to which an adhesion imparting agent having water repellency is added. 2. The optical memory element according to item 1, wherein the adhesion imparting agent is a silane coupling agent or a titanium coupling agent.