JPS61142545A - Information recording medium - Google Patents

Abstract

PURPOSE:To prevent the deformation of a substrate in sealing the titled discoid information recording medium by using an UV light curing adhesive contg. urethane acrylate and tetrahydrofurfuryl acrylate as the adhesive. CONSTITUTION:Substrates 1 and 1 are concentrically arranged through an inner spacer 4 and an outer spacer 5 and with a recording layer 3 directed to the inside, and a spacer 6 is formed between the surfaces of the substrates opposite to each other. Under such conditions, both substrates are bonded to each other by using an adhesive 7 to form an information recording medium 8. An UV light-curing adhesive contg. urethane acrylate and tetrahydrofurfuryl acrylate is used as the adhesive 7. Besides, >=60pts.wt., preferably >=80pts.wt., urethane acrylate and <=40pts.wt., preferably <=20pts.wt., tetrahydrofurfuryl acrylate are necessarily used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a sealed disc-shaped information recording medium in which a recording layer is provided on the surface of a disc-shaped substrate and information is recorded and reproduced optically.

[Prior art]

The adhesive used to seal disc-shaped information recording media must (1) be free of reaction by-products during curing, and (2) be free of solvents so as not to affect the encapsulated recording material. It is required that it not be included. For this reason, epoxy adhesives are usually used. However, when using an epoxy adhesive, there are problems such as the plastic substrate being deformed by heating during curing and curing taking a long time. It has also been proposed to use an epoxy adhesive that cures at room temperature, but the curing time is the same.

Therefore, in recent years, ultraviolet curing hot adhesives have been attracting attention. This is promising because it has the properties (1) and (2) above, but the drawback is that since the curing reaction is based on a radical polymerization reaction, oxygen in the atmosphere acts as a quencher for the radicals, resulting in slow surface curing. have. especially,
In a so-called air sandwich type sealed disk, the surface of the adhesive inside the seal is insufficiently cured, and unreacted p monomer components volatilize inside the seal, affecting the recording layer. As a countermeasure to this, it is possible to remove oxygen from the curing atmosphere, specifically by curing in a nitrogen atmosphere, but this method has the problem of requiring large-scale equipment for industrial production.

Therefore, the present inventors have successfully solved the above problem by first proposing the use of urethane acrylate as a sealing adhesive instead of Epo Φ cyacrylate, which is less susceptible to polymerization inhibition by oxygen. However, in recent years, it has become common to use plastic substrates such as polymethyl methacrylate (PMMA) and polycarbonate as disk substrates, and the adhesives mentioned above do not have sufficient adhesion to plastic substrates. There is a problem.

〔the purpose〕

An object of the present invention is to prevent deformation of a substrate and shorten the curing time of an adhesive when sealing a disk-shaped information recording medium.

〔composition〕

As a result of repeated studies on the above problem, the inventor found that the general formula CH2=C)1000-CH2-CI CI? )
This person.

The present inventors have discovered that furfuryl acrylate has a strong adhesive strength to plastic sticks, and that when it is combined with urethane acrylate, an ultraviolet-curing hot adhesive with excellent adhesiveness and less susceptible to oxygen inhibition can be obtained, leading to the present invention.

That is, the present invention provides an information recording medium in which a pair of disk-shaped substrates, at least one of which has a recording layer on one side, are bonded together with an adhesive so that the recording layer faces inside. As the adhesive, an ultraviolet curing hot adhesive containing urethane acrylate and tetrahydrofurfuryl acrylate is used. At this time, the two substrates can be bonded together with a space between them.

In addition, "urethane acrylate" as referred to in the present invention refers to one having an isocyanate group (-NGO) and a hydrocarbon group (-NGO).
-OH), which is obtained by reacting an acrylate having an acryloyl group (CH2=CHC) in the molecule.
Any material having a urethane bond (-NHCOO-) and a urethane bond (-NHCOO-) may be used. Generally, as shown in the example below, incyanate is placed on both ends of polyester and acrylicized.

In addition, in the ultraviolet curing hot adhesive used in the present invention, urethane acrylate is 60 parts by weight or more, preferably 80 parts by weight or more, and tetrahydrofurfuryl acrylate is 40 parts by weight or more.
It is necessary that the amount is not more than 20 parts by weight, preferably not more than 20 parts by weight.

By combining these two types of acrylates, general I
/c The disadvantage of sealing with a UV-curable hot adhesive that does not contain urethane acrylate is that it is highly anaerobic and hard to harden the protruding parts, and the UV-curable hot adhesive that does not contain tetrahydrofurfuryl acrylate has poor adhesive strength with the substrate. A method has been created that eliminates the drawbacks of conventional sealing. Although the urethane acrylate resin of the present invention can be used alone as it is, it is preferable to use it together with a photopolymerization initiator. As the photopolymerization initiator, conventionally known ones can be suitably used, such as carbonyl compounds, organic sulfur compounds, peroxides, redox compounds, azo and diazo compounds, and halogen compounds. These photopolymerization initiators are used in an amount of 11 to 20 parts, preferably 1 to 10 parts, based on 100 parts by weight of the resin.

Next, a configuration example of the information recording medium of the present invention will be explained with reference to the drawings.

The disk-shaped substrate 1.1 is made of, for example, a transparent plastic plate and has a fitting hole 2 in its center. These boards 1
, 1, a recording layer 3 is formed on one side thereof. These substrates 1.1 are arranged concentrically with the recording layer 5 inside through the inner spacer 4 and the outer spacer 5, and a space 6 is formed between the mutually opposing surfaces of each substrate. The information recording medium 8 is laminated using the adhesive 7 of the present invention.

As the recording layer 3, any known recording material for recording media can be used without being limited to a specific material. Typical examples include thin films of metals such as 'I'e and At, and thin films of organic dyes such as cyanine dyes. In addition to the above configuration example, although not shown, the recording layer 3 may be formed on both sides of the substrate 1.1. Also,
When bonding two substrates together, the substrates can be directly bonded to each other without using a spacer.

〔Example〕

Next, the present invention will be further explained with reference to Examples, but the present invention is not limited thereto. In the examples, parts are expressed in parts by weight.

Example 1 Two polymethyl methacrylate disks with a diameter of 200 mm and a thickness of 1 mm were used, and after providing a recording layer on one of the disks, a plate was inserted through a 1 mm thick splice as shown in the figure. It was sealed by pasting an adhesive on it. An ultraviolet curing resin having the following composition was used as the adhesive.

Tetrahydrofurfuryl acrylate 15 parts Benzyl dimethyl ketal 5 parts An 80 W/C1K high pressure mercury lamp was used as the ultraviolet light source, the irradiation distance was 10 cIL, and the irradiation time was 10 seconds.

The thus produced air sandwich sealed disk was subjected to a storage test at 60° C., 90% R, )1.07.

Initial values for reflectance, C/N and error rate and 10
The values after storage for 00 hours are shown in the table below.

For the recording layer, a cyanine dye shown in the following formula was used, and a dye conversion 11! film with a film thickness of 500X was obtained by spin-coding a dichloroethane solution of the dye onto a polymethyl methacrylate substrate. Examples 2 to 3 Sealed disks were prepared in the same manner as in Example 1, except that an ultraviolet curable resin having the following composition was used, and a storage test was conducted.

In Example 2: Nato 2 Human o Furfuryl Acrylate 18
part CH2CHC00-+C)12cH20+Fc0cH
c) 12 5 parts benzyl dimethyl ketal
In 2 parts Example 3: Tet''y Drofurfuryl Acrylate 1
3 parts benzophenone 2 parts Comparative Examples 1 to 5 Sealed disks were prepared in the same manner as in Example 1, except that the commercially available adhesive shown below was used, and a storage test was conducted.

Comparative Example 1 Nirickson Bond 1004 A/B (Epoxy system manufactured by Chisso) 2: 19A10 (UV curing type manufactured by Sony Chemical)? l: 19A20 (z) 4: φ350 (Loctite UV curing type) 5:
Su3001 (Three Bond UV curing type) 1000
The evaluation results after time storage are shown in the table below.

Initial value 26 58 5X10-6-Example 1 2
4 58 7X10-6 None 2 24
58 7X10”6 #5 25 58
6X10-6 #Comparative example 1 25 58
6X10""6 Peeling 2 20 54
1x10-5 Peeling 3 10 30
1x10″″2 Peeling 4 12 55 1X
10-2 Peeling 5 20 45 2x10
-5 Peeling [Effects] The recording medium of the present invention constructed as described above has less substrate deformation and better storage stability than those bonded using conventional epoxy adhesives. Moreover, the curing time during lamination can be shortened.

[Brief explanation of the drawing]

The figure is a cross-sectional view showing an example of the structure of the enclosure information recording medium according to the present invention. DESCRIPTION OF SYMBOLS 1... Substrate, 2... Fitting hole, 3... Recording layer, 4...
... Inner sweep, 5... Outer sweep, 6... Space, 7... Adhesive, 8... Information recording medium.

Claims (1)

[Claims] A sealing structure in which a pair of substrates having a recording layer on at least one side of two disk-shaped substrates are placed facing each other with the recording layer facing inside and bonded together with an adhesive with or without a space between them. An information recording medium further comprising: an ultraviolet curing hot adhesive containing urethane acrylate and tetrahydrofurfuryl acrylate.