JPH03100944A - Production of optical recording medium - Google Patents

Abstract

PURPOSE:To prevent swelling and distortion of a medium by using a reactive hotmelt adhesive which can be cured with moisture, allowing the substrate surface before applying the adhesive or the adhesive surface after applied to contact to a supersaturated vapor atmosphere, and sticking substrates together. CONSTITUTION:Two substrates each having a recording layer, reflecting layer, protective layer, etc., are adhered with a moisture-curing type hotmelt adhesive. The moisture-curing hotmelt adhesive consists of urethane prepolymers containing isocyanate groups at the end of the molecule and tackifier resin. On adhering the substrates, the surface to be coated is priorly humidified before applying the adhesive on the substrate surface with a coater, or otherwise, the surface of the adhesive layer after applied on is humidified. By this method, production of amines in the adhesive applied can be promoted before sticking the two substrates, which allows carbon dioxide gas to escape into air. By sticking the two substrates then, swelling of the medium can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing an optical recording medium. Specifically, the present invention relates to a method for manufacturing an optical recording medium without deformation by preventing deformation of the medium caused by an adhesive when manufacturing an optical recording medium by bonding transparent substrates together.

[Conventional technology]

Optical video disc, optical audio disc, D
An optical recording medium, which is an optical recording disk called a RAW disk, has a metal recording layer 1 on a plastic substrate.
There are types with a dye recording layer, a magneto-optical recording layer, etc., a type that utilizes melting and sublimation of the recording film by a light beam, a type that utilizes phase transition between crystal and amorphous, and a type that utilizes the magneto-optical effect. A magneto-optical type that utilizes is known.

In either type, dust usually adheres to the recording layer,
A light-transmissive substrate (transparent substrate) to prevent scratches etc.
A recording layer is formed along with other auxiliary layers, and these layers are bonded to face each other inwardly. During reproduction, recording and reproduction are performed through the substrate. Hot-melt adhesives are often used, which do not contain solvents that have a negative effect on substrates, recording layers, etc., and are easy to process. However, conventional true-melt adhesives require high temperatures during application, which can have an adverse effect on the recording layer and substrate, and the media after adhesion does not have sufficient heat resistance or durability, making it difficult to use in high-temperature environments. At the bottom, the bonded disks may shift or peel due to softening of the adhesive.

In order to solve these problems, it has been proposed to use a moisture-hardening reactive real-melt adhesive to improve peelability, durability, and moisture resistance (Japanese Patent Laid-Open No. 62-264).
456).

Moisture-curing reactive hot melts generally undergo a molecular chain extension reaction with moisture in the air and isocyanate groups in the adhesive, resulting in a zero reaction in which the urethane prepolymer has a high molecular weight and strengthens the cohesive force of the adhesive. The reaction proceeds as described below, and as the reaction hardens, carbon dioxide gas is produced as a by-product.

0CN-R-NCO+H*0+0CN-R'-NCO
When this adhesive is used, swelling is often observed on the substrate. The reason for this is that because the reaction progresses after the substrates are bonded together, hardening begins at the edges of the medium, which are more likely to come into contact with moisture in the air, and carbon dioxide accumulates in the middle of the substrate, where hardening is slowest. This is thought to be due to swelling. It is also believed that the difference in curing time causes a difference in shrinkage rate, causing distortion in the intermediate portion of the substrate.

[Problem to be solved by the invention]

The object of the present invention is to solve the above-mentioned problems in a bonding process using a moisture-curable reactive real-melt adhesive.

[Means to solve the problem]

As a result of intensive studies to solve the above-mentioned problems with optical recording media, the inventors of the present invention formed an optical recording layer on a substrate, or applied a moisture-curing reaction to the surface on which a recording layer and a protective layer, etc. were formed. The present inventors have discovered that the above-mentioned problems can be solved by applying a special treatment when applying a polyurethane true melt adhesive using a roll coater, and have completed the present invention.

That is, the gist of the present invention is to manufacture an optical recording medium in which two substrates, at least one of which has a recording layer, are bonded together with the recording layer inside, using a moisture-curable reactive hot melt as an adhesive. An optical recording medium characterized by using an adhesive, bringing the surface of the substrate before applying the adhesive or the surface of the adhesive after applying the adhesive into contact with a saturated water vapor atmosphere, and bonding the substrates facing each other. It consists in the manufacturing method.

In the present invention, one substrate is polycarbonate resin,
A resin substrate such as acrylic resin is used.

As the recording layer, one having a layer structure used for optical recording, such as a generally known perforated type, phase change type, or magneto-optical type, can be used.

In the case of the magneto-optical recording layer, a layer structure of a known magneto-optical recording layer is used. For example, TbFe', TbFeCo,
, amorphous magnetic alloys of rare earth elements and transition metals such as TbCo and DyFeCo, MnB1. A polycrystalline perpendicular magnetization film such as MnCuB1 is used.

As the magneto-optical recording layer, a single layer may be used, or a GdT layer may be used.
Two or more recording layers may be stacked, such as bFe/TbFa.

An interference layer can also be provided between the substrate and the recording layer.

This layer uses the light interference effect of a transparent film with a high refractive index.
This is to lower the nozzle size and improve the C/N ratio by lowering the reflectance.

Metal oxides and metal nitrides are used as the interference layer.

As a metal oxide, A1. O,,Ta,O,.

Stow; Oxide such as SigITiO, AJ-T
Complex oxides such as a-0 are typical, but Ti +
Composite oxides of Aj and Ta containing Zr*W#Mo*Yb, etc. can also be used.

Examples of metal nitrides include silicon nitride and aluminum nitride, but metal oxides are preferably used from the viewpoint of interference effects, stability, etc.

The thickness of the interference layer is about 400 to 1,500, preferably about 500 to 1,000.

It is desirable to provide a dielectric layer selected from the same material as the interference layer on the side of the recording layer opposite to the interference layer. Highly reflective metal (e.g. Al, Cu
AJ or an alloy thereof is preferable from the viewpoint of cost etc., and AJ or an alloy thereof is preferable from the viewpoint of cost, etc.) or an alloy thereof as a reflective layer.
The thickness of the zero-reflection layer, which preferably uses V, Cr, Pd, etc. as alloy components, is about 100 to 1000.

It is also possible to provide an organic protective film on the outer layer of the reflective layer to prevent scratches and oxidation. This organic protective film contains a compound with multiple acrylate or methacrylate groups that is cured by radiation such as ultraviolet rays or electron beams, and can be applied uniformly by coating methods such as spin coater spray application, roll coater, flow coater, etc. Just apply it.

Examples of the radiation irradiated to the coating include ultraviolet rays and electron beams, but ultraviolet rays are preferable.

The method of the present invention involves bonding two substrates each having a reflective layer, an organic protective layer, etc. on the recording layer using a special method using a moisture-curing reactive real-melt adhesive. configured.

The moisture-curable reactive hot melt adhesive is composed of a urethane prepolymer having incyanate groups at both ends and a tackifier resin, and it is also possible to adjust the viscosity by adding an aromatic oil if necessary.

The urethane prepolymer used in the present invention is, for example, 2,4-tolylene diisocyanate.

A diisocyanate compound consisting of a single substance such as 2,6-tolylene diisocyanate, hexamethylene diisocyanate, 1,5-naphthylene diisocyanate, or a mixture thereof, and ethylene glycol, propylene glycol, 1,4-butanediol, 1,4- Monomers or polymers of butyne diol and polytetramethylene ether.

A prepolymer obtained by addition polymerization with a diol compound consisting of a single substance such as glycine or a mixture thereof can be mentioned.

It is desirable that the NCO equivalent of the prepolymer is 5% by weight or less; if a prepolymer with a content exceeding 5% by weight is used,
This is because the adhesive tends to become brittle.

If the amount of urethane prepolymer is too small, the reaction with moisture in the air will be insufficient, and sufficient heat resistance strength will not be developed.
The adhesive becomes hard and brittle after bonding between boards. On the other hand, if the amount is too large, the initial cohesive force will be weak, so it is preferable that the urethane prepolymer is contained in the adhesive in an amount of 30 to 75% by weight, more preferably 45 to 70% by weight.

The tackifier resin used in the present invention is completely inert 60
Preferably, it has a softening temperature of ~140°C.

For example, coumaron resin, coumaron-indene resin, terpene-phenolic resin.

These include rosin derivatives or styrene-based low molecular weight resins.

If the content of these tackifying resins is too low, it will not be possible to impart strong adhesive cohesive force to the urethane prepolymer.
Instant adhesion will be weakened, and if it is too high, the adhesive will become brittle and strong adhesive strength will not be obtained.
The content is preferably 50% by weight.

In addition, aromatic oils are generally used as rubber softeners.
Process oil, extension oil.

It refers to aromatic components in oils that are widely known as softners, etc., and has 2 to 3 carbon atoms in the hydrocarbon residue with 2 to 6 carbon atoms.
It is desirable that benzene rings or alkylbenzene rings are bonded together.

In addition to the above-mentioned urethane prepolymer, tackifying resin, and aromatic oil, adhesives used in the present invention include polyethylene, ethylene-vinyl acetate copolymer, ethylene-ethylene acrylate copolymer, atactic polypropylene, etc. Base resin in general hot melt adhesives,
Waxes such as polymerized wax, dioctyl phthalate,
Plasticizers such as dibutyl phthalate and TPP may be contained in the adhesive used in the present invention.

Moisture-curing reactive true melt adhesive has a rating of 70 to 100
Although it can be applied at a low temperature below .degree. C., it may be heated up to about 120.degree. C. in some cases.

As the coating device, various hot melt coaters and real melt applicators can be employed, and a roll coater is particularly preferred and used. When coating with a roll coater, the film thickness is preferably 10 to 100 μm, particularly 10 μm.
~60μ is preferred.

Usually, 10 to 6
When applied in the range of 0 μ and bonded, after 2 to 3 days, swelling occurs inside the bonded disk, the flatness changes, and warpage occurs, and in extreme cases, recording This phenomenon of not being able to be used as a medium is thought to be due to the fact that carbon dioxide gas is produced as a by-product during the reaction of the moisture-curing reactive hot melt adhesive with moisture. To be more specific, it is thought that adsorbed moisture on the substrate and moisture in the air are involved in the reaction as moisture sources for the reaction, but after bonding, the moisture in the air flows through the inner periphery of the bonded disks rather than penetrating from the surface of the disks. A larger amount permeates from the adhesive exposed portions on the side surfaces of the outer periphery, and the reaction from this portion takes precedence, gradually progressing from the outer and inner edges to the middle portion of the disk.

On the other hand, carbon dioxide gas generated until the reaction curing is completed escapes into the outside air mainly from the bonded side surfaces of the substrates. However, the carbon dioxide produced as a by-product in the middle of the disk cannot escape from the sides because the reaction is completed and hardened at the outer and inner edges, and it accumulates inside, causing a swelling phenomenon. Presumed. In addition, shrinkage due to curing of the adhesive is delayed in the intermediate portion, so this may also have an effect.

As a result of studying the reaction process between a moisture-curing reactive hot-melt adhesive and water, the inventors of the present invention noticed that high polymerization occurs through urea bonds via amines as described below.

1) Aminated -RNCO+Hm O→ -RNHC0H--'RNHz +COt? 1 2) Highly polymerized -R-NH, +0CN-R, -→ R-NHCNH-Rt - 1 In other words, before applying the adhesive to the surface of the substrate with a coater, the coated surface is pre-humidified, or By humidifying the surface of the adhesive after applying the adhesive, the adhesive applied before bonding the two substrates is aminated, allowing carbon dioxide gas to escape, and then bonding the two substrates together. By combining these, it is possible to prevent the swelling phenomenon. The humidifier used to humidify the above-mentioned coated surface may be either a spray type humidifier or a heating evaporation type humidifier, as long as the surface to be humidified is brought into contact with the humidified atmosphere. If the adhesive is bonded within the open time of the adhesive after humidification in this manner, a disk that does not swell can be obtained.

As a humidifying method, it is possible to immerse the surface to be humidified in water, but from the viewpoint of uniform humidification and ease of handling, a method of bringing the surface into contact with water vapor is used.

That is, this is a method in which supersaturated water vapor is generated using a suitable humidifier, and the surface to be humidified is exposed to this.

Specifically, for example, expose the surface to be humidified for several seconds to a few seconds to the steam generation port of a humidifier with a humidification rate of Q, 51/Hr, or pour water onto a hot plate and generate steam by heating. Possible methods include exposing the surface to be humidified to this steam. The temperature of the water vapor may be at room temperature or above, but is approximately 30 to 70 degrees Celsius, preferably 35 to 60 degrees Celsius.
℃ is good.

Humidification with water vapor may be performed on either the substrate surface before the adhesive is applied or the adhesive surface after the adhesive is applied, but both may be treated.

〔Example〕

Examples are shown below, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

[Example 1] A circular flat polycarbonate injection molded substrate with a guide groove of 130 mm in diameter and 1.2 mm in thickness with a 15 mm hole in the center was used as the substrate, and the following was placed on it as a magneto-optical recording medium. A film with the following layer structure was formed using a continuous sputtering device.

stN, (750 people)/TbFeCo (300 people)
/An! St (400 people) / SiNyo (3,50
After spraying heated steam for 5 seconds on the recording film forming side of this substrate, a moisture-reactive hot melt adhesive was immediately applied to the recording film side using a roll coater to a thickness of 30 μm. The adhesive is the product name “Nisdyne 9606J”
(manufactured by Tanemizu Kagaku Kogyo ■), and the coating roller temperature was 120°C. The two substrates that had been humidified and coated with adhesive in this way were placed so that they faced each other with the adhesive coated surfaces facing inside, and were pressed together using a press machine.

The obtained optical recording medium of the present invention was examined for swelling and distortion by irradiating it with a condensing mercury lamp for a microscope and observing the reflected image, but no swelling or distortion was observed.

In order to check the changes in this bonded medium over time, it was left in the air for 7 days and then observed again using a condensing mercury lamp for a microscope, but no changes such as swelling or distortion were observed.

[Example-2] A recording layer and the like were formed on a polycarbonate substrate in the same manner as in Example-1. A moisture-curable reactive true melt adhesive was applied to the side of the substrate on which the recording film was attached to a thickness of 35 μm. The adhesive used was the product name "Hibon 4810J" (manufactured by Hitachi Chemical Polymers), and the application roller temperature was 1.
The temperature was 20°C.

After applying the adhesive, water vapor was sprayed onto the surface of the adhesive for 5 seconds using a humidifier that releases water in the form of a spray. Thereafter, the two substrates were quickly pressed and bonded together. Similarly, only the adhesive-coated surface of one substrate was subjected to humidification treatment and bonded to an unhumidified adhesive-coated substrate.

Even after 3 days, no swelling or distortion was observed in the two optical recording media bonded together.

[Comparative Example-1] A recording layer was formed on a polycarbonate substrate in the same manner as in Example-1, and a moisture-curable reactive hot melt adhesive was applied to a thickness of 28 μm on the recording layer side of this substrate. The adhesive used was Nisdyne 9606 (Tanezu Chemical Industry ■).
The coating roller temperature was 120°C. After applying the adhesive, the two substrates were pressed together using a press machine without performing any humidification treatment. Immediately after bonding, no swelling was observed in the reflected image of the obtained optical recording medium when irradiated with a mercury lamp, but when it was similarly observed with a mercury lamp three days later, swelling was observed in the center of the recording area. It could not be used as an optical recording medium.

〔Effect of the invention〕

According to the method of the present invention, it is possible to produce a stable optical recording medium that does not swell or distort when it is bonded together using a moisture-curable reactive hot melt adhesive. .

Claims (1)

[Claims] (1) Two substrates, at least one of which has a recording layer,
When manufacturing an optical recording medium that is bonded with the recording layer on the inside, a moisture-curing reactive hot melt adhesive is used as the adhesive, and the substrate surface before or after the adhesive is applied. A method for producing an optical recording medium, which comprises bringing the surface of an adhesive into contact with a supersaturated water vapor atmosphere and bonding substrates facing each other.