JPS6057552A - Laser recording medium - Google Patents

Abstract

PURPOSE:To obtain a laser recording medium of which the surface of the base plate is resistant to scratching by subjecting the surface of the base plate to an electric discharge treatment then providing a layer consisting of a radiation curable resin. CONSTITUTION:The active group generated on the surface of a base plate by an electric discharge treatment reacts with a radiation curable resin and forms a secure bond when radiations are irradiated thereto. A plastic base plate such as polymethyl methacrylate, polycarbonate, etc., glass base plate and a metallic base plate such as aluminum, etc. are used as the base plate. A glow discharge treatment, corona discharge treatment, UV irradiation treatment, etc. are enumerated as the high and preferable discharge treatment method. As monofunctional compd. acryalic acid ester, methacrylic acid ester and acrylamide and their derivs. methacrylamide thereof and the deriv. thereof are used as the radiation curable resin.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to laser recording media that are recorded or read by laser light, and more particularly to improving the scratch resistance of laser recording media.

In recent years, optical discs that are recorded using laser light,
It has come to be used for text files, still image files, and computer output. This optical disk medium has a recording layer made of a thin film of camphor or chalcogenide compound formed on the surface of a transparent substrate, which is rotated.

The recording layer is melted, deformed, and phase-transformed into a spot with a diameter of about lμ by a laser beam emitted according to a signal, and information is recorded by this spot.

In conventional optical discs, dust adheres to the recording layer and scratches occur during handling, resulting in failures such as bit error rate, dropouts, etc.

Therefore, two supports with records are placed with the recording layer inside,
A so-called air sand inch structure in which the materials are bonded together via a spacer was proposed by Japanese Patent Publication Sho Tough-32≠73 and others. The so-called glued structure, which is glued together using adhesive, is special! 2-3273"J.

In such an air sandwich structure or a bonded structure, since the recording layer is located on the inside, dust and rocks on the recording layer can be prevented from being scratched. Since recording by the cut laser beam is performed through the transparent substrate, there is an advantage that it is not affected by dust, scratches, etc. on the surface of the substrate away from the focus of the laser beam.

As mentioned above, the air sandwich structure or bonded structure makes it less susceptible to dust, scratches, etc. on the surface of the substrate, but even so, if a large amount of sunlight occurs on the surface of the substrate, it will adversely affect the laser beam during recording or reading. .

To impart scratch resistance, use JP-A-7-3634'! It has been proposed to provide an inorganic film, particularly an inorganic oxide film, as described in JP-A No. 7-IA and others.

However, in order to provide an inorganic film, a vacuum deposition method must be used, which is difficult to operate and increases costs.

Furthermore, the resulting inorganic film is hard but brittle and cannot provide sufficient scratch resistance.

On the other hand, it is known from Japanese Patent Laid-Open No. 57-60337 that the surface of the substrate is protected by coating the entire surface of the substrate with a synthetic resin, and it has also been proposed to use an ultraviolet curing resin. However, in order to provide scratch resistance, the formed film must be hard, but the harder it is, the worse the adhesion between the layer and the substrate becomes, making it easier to peel off during handling. As a result, the function of aφ cannot be fulfilled.

Therefore, the problem cannot be solved simply by using an ultraviolet curing resin. The present invention solves the above-mentioned drawbacks, improves the adhesion between the scratch-resistant layer and the substrate, and makes it practical.

That is, the first object of the present invention is to provide a laser recording medium that is resistant to scratches on the substrate surface.

The first objective is to provide a laser recording medium in which a strong substrate and a scratch-resistant layer have sufficient adhesive strength.

Thirdly, it prevents deformation of the substrate due to moisture absorption and provides a laser recording medium with less deformation such as waviness and warpage.

The first object is to provide a laser recording medium that prevents deterioration of the recording layer due to moisture and has excellent storage stability.

The object of the present invention is to provide a layer made of a radiation-cured resin after discharging the surface of the substrate, so that the Tg of the radiation-cured resin after radiation curing is 0°C or higher. The effect will be greater if the edges are sharper than the above.

Electric discharge treatment is already known as one of the general surface treatment methods for supports, and is known to be effective in improving adhesive strength. However, as in the present invention, electric discharge treatment was performed. It is not known that irradiation with a radiation-cured resin can dramatically improve adhesive strength or prevent hygroscopicity, and the present invention takes advantage of this property in a laser disc. be. It is presumed that these properties are improved because the active groups generated on the substrate surface by the release treatment react with the radiation-cured resin during radiation irradiation to form a strong bond.

Substrates according to the invention include polymethyl methacrylate;
Plastic substrates such as polycarbonate.

7"5 using a glass substrate or a metal substrate such as aluminum
I can do it. Of these, polymethyl methacrylate)
LIT is inexpensive and easy to break.It also has low optical anisotropy and particularly has high adhesion to radiation-cured resins.The discharge treatment methods used in the present invention include goo-discharge treatment, corona discharge treatment, Examples include ultraviolet irradiation treatment.

Although the effect on adhesion can be obtained with either method, glow discharge treatment is preferred because it can be treated in a vacuum because it is free from the influence of dust.

The conditions for glow discharge treatment are that the degree of vacuum is θ.

Preferably, θ~/θTorr. Even more preferably the voltage! Oθ to joθθV is preferable. More preferably, the frequency used can be direct current, current, or high frequency. The IB during processing is preferably from /second to 10 minutes; if the processing is carried out for a longer time than 70 minutes, the acrylic substrate will be colored. Not preferred.The same effect on adhesive strength can be obtained in any of the discharge atmospheres, such as air, nitrogen, oxygen, and argon.

The radiation-curable resins used in the present invention include the following: Monofunctional compounds include acrylic esters, methacrylic esters, acrylamide and its derivatives methacrylamide and its derivatives 2 acrylic acid, methacrylic acid , acrylonitrile vinyl sulfonic acid, allyl ester, crotonic acid, styrene and its derivatives, vinyl ester,
vinyl ether, etc.

Trifunctional or higher functional compounds include an acryloyl group at the end,
It has two or more methacryloyl groups and vinyl groups, and the molecule h1
- is 10,000 or less, preferably acrylic esters and methacrylic esters of polyhydric alcohols, such as trimethylolpropane triacrylate. Further, compounds described in "Oligomer Handbook" (by Junji Furukawa, Kagaku Kogyo Nipposha IP, 241.j-, 210) may be mentioned.

In order to make the Tg of the radiation-curable resin ro 0c or more, the molecular weight of the above-mentioned compounds should be io and oo.

The proportions of the following compounds need to be o -t O%.

The coating amount of these resins is 0. j~200μ, preferably 30-100μ.

The radiation for curing the above compounds includes ultraviolet rays, 'd
Examples include +' and -f' lines. Of these, the scale of the equipment.

Ultraviolet rays are preferable in terms of cost and safety. As for processing.

It is preferable to skewer under vacuum or nitrogen atmosphere. This is because if the ultraviolet curable monomer is anaerobic, when it is exposed to radiation in the atmosphere, it generates ozone, which prevents the curing of the radiation curable resin.

The recording layer material used in the present invention includes fully reduced B1,
Sn, 1゛e, etc. or chalcogenide materials such as total fluoride, metal sulfide, Se, Ge, etc. are used. These recording layer materials are provided as a thin film with a thickness of several 700 to several 1 OOOA by a vacuum evaporation method or a sloping method.

The vapor deposition process may be carried out either before or after applying the radiation-cured resin to the substrate, but in view of the ease with which the vapor-deposited layer is damaged, it is preferable to first apply the radiation-cured resin (σ1 resin) and then vapor-deposit it.

The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Cell cast polymethyl methacrylate substrate (thickness '-
JmM) into a donut shape with an outer diameter of 3007n7n and an inner diameter of 3j and m, and 0.0! Under pressure of Torr, 20
Glow discharge treatment was performed for 30 seconds at a voltage of 0.theta.■, and then the following compositions (1) to (4) were applied to a thickness of about jO.mu., and then ultraviolet rays were irradiated in a nitrogen gas atmosphere to cure them. The Tg of the cured product at this time is /, 200C,
go'C, Rio'C,/As a comparative example, one type of t1 without glow discharge treatment was also prepared.

Mylar tape (
3MiJ,] was used to perform a peel test on the cross-cut surface and show it in an interview at a distance of 1. If it did not peel off at all, it was graded A, and if it peeled off, it was graded B, and if it peeled off more than 1 ton, it was graded 6.

When subjected to glow discharge treatment according to the present invention, compositions (1) to (
4) were all grade A. In addition, when no glow awakening treatment was performed, compositions (1) to (4) were all grade 0.

By performing the 5-glow discharge treatment in this way, the adhesion between the substrate and the radiation-cured resin layer was greatly improved.

Incidentally, the scratch resistance of the image retention film itself using the compositions (11 to (4)) was at a level that could be used for practical purposes, but the comparative example that was not subjected to glow discharge treatment was
This is because the protective layer will fall off due to rubbing.

It had substantially no ability to maintain the axis of the substrate surface.

In and GeS were co-deposited as a recording layer on the surface of the female substrate on which no protective layer was provided in a weight ratio of t.

The thickness of the recording layer at this time was about ≠00.

The above-described recording layer was placed on a spacer made by punching out a cell-cast acrylic plate, and a Buhi substrate was bonded to the spacer with the recording layer facing inside using an ultraviolet curing adhesive to obtain a laser recording medium. Go 0c, seed laser recording media to these,
When exposed for 3 days under conditions of humidity 906j) R1-T, the laser recording medium of the present invention, which had been subjected to glow discharge treatment, showed almost no deformation, and there was no deterioration of the remaining 26 layers. Ta.

On the other hand, in the comparison U recording medium that was not subjected to glow discharge treatment, when 2θ0 (2, However, warpage occurred and it could not be put into practical use.

Claims (2)

[Claims] (1) In an information recording medium having a recording layer on which information can be written and/or read by a laser on a transparent plastic substrate, the surface opposite to the surface on which the recording layer is provided is treated with a radiation-cured resin after discharge treatment. 1. A laser recording medium characterized by comprising a layer consisting of: (2) The Tg of the radiation-cured resin layer after radiation irradiation is s
'o ', a of a patent claim characterized in that it is 0c or more
The laser recording medium described in item 1 of the article.