JPH01276447A - Optical recording medium - Google Patents

Abstract

PURPOSE:To increase recording sensitivity and to obtain high reliability over a long period of time by joining plural substrates having recording films on the surface via a self-adhesive agent. CONSTITUTION:The recording films 11 are formed on two sheets of the substrates 10 and the recording layers 11 are stuck to each other via a self-adhesive agent layer 30. Polyester, polyimide, aluminum foil, etc., are used for the substrates 10. While self-adhesive agents of a silicone system, rubber system, acrylic system, etc., are preferable as the self-adhesive agent. Recording is executed by the change in the shape of the recording films by laser light.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an optical recording medium such as an optical disk or an optical card that records and/or reproduces information using a laser.

[Prior Art] Conventionally, as a method for protecting the recording film of an optical recording medium, (
b) A method of forming an air sandwich structure, ([+) A method of forming a protective layer of organic or inorganic material, or a method of bonding multiple substrates with the recording film inside (hereinafter referred to as multilayer type), etc. have been proposed. ing. However, in the case of the former (a), the interior is hollow, so the mechanical strength is low, and
If a large temperature change is applied, warping occurs or moisture condenses in the hollow portion, making it difficult to record and reproduce well.

The latter (rl) multilayer optical recording medium has a structure as shown in the cross-sectional schematic diagrams of FIGS. 4 and 5.

Here, the protective layer 12 needs to have good adhesive strength to the recording film 11. Epoxy resins, thermosetting resins, thermoplastic resins, photocurable resins, and the like are known as such protective films. However, the above-mentioned resin is (a) rigid, and in the case of a recording medium whose shape is changed by irradiation with laser light, it can interfere with the formation of recording bits, and as a result, high laser power is required for recording. (l)) There are problems such as long curing time and low productivity.

Therefore, for the purpose of particularly improving the decrease in recording sensitivity, for example, Japanese Patent Laid-Open No. 58-203095 discloses a technique of providing a rubber elastic polymer layer such as silicone rubber.

[Problems to be Solved by the Invention] The present invention has been made in view of the above-mentioned problems. The aim is to provide it at a low price.

[Means for Solving the Problems] The above object of the present invention is achieved by bonding a plurality of substrates made of synthetic resin substrates or films having a recording film on at least one surface via an adhesive. be done.

Here, the adhesive refers to an adhesive that sensitively adheres to an object with pressure similar to finger pressure, and is also called a pressure-sensitive adhesive. The adhesive is a viscoelastic material and has dual properties of solid and liquid, flows under pressure and comes into contact with the surface to which it is adhered, and exhibits the necessary adhesive strength without a solidification process. (For example, "Adhesive Handbook (
(edited by Japan Adhesive Association). ) The adhesive consists of a rubber elastic body and a tackifying resin or plasticizer that is compatible with the rubber elastic body. Depending on the type of elastic body that is the main component,
They are classified into silicone-based, rubber-based, acrylic-based, and other types (polyvinyl ether-based, etc.).

A wide range of these methods can be applied to the present invention. Among them, a silicone adhesive is most preferably used because it provides high recording sensitivity.

The silicone-based adhesive preferably used in the present invention is one that contains at least linear silicone raw rubber with a skeleton of siloxane bonds as an elastomer component, and has a highly crosslinked network structure with a skeleton of siloxane bonds. This adhesive contains silicone resin as a tackifier component. The degree of recording is largely related to the compatibility and dispersion state of the elastomer component and tackifier component of the silicone adhesive.
00000 more preferably 250000 to 80000
A pressure-sensitive adhesive in which 0.0 silicone raw rubber is mixed with silicone resin in a weight ratio of 0.5 to 2.0, more preferably 0.8 to 1.4 is preferable. In addition, the silicone adhesive has properties such as cohesive strength by mixing organic peroxides such as benzoyl peroxide and causing a crosslinking reaction using highly active free radicals that are decomposed and generated by heating as an initiator. It is more preferable to improve. Note that it is desirable that the peroxide be added in a weight ratio of 0.1 or less, more preferably 0.05 or less, to the adhesive. If a large amount is added, the adhesive may become hard and the recording sensitivity may decrease.

The advantages of the silicone adhesive having the above-mentioned composition are (a) excellent weather resistance, water resistance, and chemical resistance, and these properties do not change for a long period of time; (o) -5
It exhibits good adhesive strength over a wide temperature range from about 0°C to 250°C, and (8) has low irritation to living organisms.

Specific examples of silicone adhesives used in the present invention are K R-101-10, K R-130 (Shin-Etsu Chemical Co., Ltd.'m); S H-42130, S D-4570.
(Manufactured by Torre Silicone): Y R-3340
, YR-32H (manufactured by Toshiba Silicone Corporation), and the like. These can be more easily applied by methods such as bar code method, dip method, spin code method, etc. Furthermore, unlike silicone-based adhesives that harden through chemical reactions, curing time is not required, so productivity is improved.

Examples of the elastic body of the rubber adhesive include natural rubber, synthetic rubber such as synthetic in-prene rubber, and butadiene-styrene rubber. In addition, tackifying resins that impart desirable effects and adhesive properties include natural rosins and their derivatives, terpene-based resins, and petroleum-based tackifiers such as C6-based, C9-based, and C9-based tackifiers.
Examples include copolymerization systems of 3 and C0. Further, examples of modified adhesive properties include #813, #821W (manufactured by Dainippon Ink & Chemicals): No., 513 (manufactured by Nitto Electric Industries, Ltd.), etc.

In addition, the acrylic polymer used in the acrylic adhesive used in the present invention is mainly composed of monomers that form adhesive, low glass transition temperature polymers such as butyl acrylate and 2-ethylhexyl acrylate, and has a high cohesive force. Components that improve adhesion include motsuma-1, which forms polymers with high glass transition temperatures, such as methyl methacrylate, methyl acrylate, and vinyl acetate, and functional groups that can improve adhesive strength and serve as crosslinking starting points, such as acrylic acid and 2-hydroxyethyl acrylate. Examples include polymers formed by blending monomers having the following properties. In addition, as crosslinking agents that improve cohesive force, incyanate compounds, metal ions, metal chelates,
Examples include epoxy, melamine, and urea compounds. Furthermore, examples of the tackifying resin include rosin-based, terpene-based, C3-based, and copolymerized petroleum resins of C6 and CO, xylene-based resins, phenol-based resins, and modified resins thereof. Furthermore, for the purpose of improving the properties of the adhesive, plasticizers, anti-aging agents, etc. may be added. A specific example of the acrylic adhesive is M C-,1
000, MC-2000, No. 532, No.
535A, No., 537 (manufactured by Nitto Electric Industry Co., Ltd.)
, DF715, DF 8320, DF8515S (manufactured by Toyo Ink Manufacturing Co., Ltd.); #8625PW, #86250
AW (manufactured by Dainippon Ink Chemical Co., Ltd.); T4090, NP
308 (manufactured by Sony Chemical Company), etc.

1 to 3 are schematic cross-sectional views showing examples of optical recording media according to the present invention. If the substrate such as a synthetic resin and the recording film are stable to the solvent (for example, toluene, xylene) contained in the preparation of the adhesive, the adhesive 30 is compatible with the substrate 10.
Also, it can be applied directly to the recording film 11 in a state containing a solvent. If it is not stable, conventionally known epoxy resins and the like can no longer be used, but the adhesive of the present invention can be used. For example, polyester film, polyimide film, tetrafluoroethylene film, aluminum foil,
Materials such as silicon glass cloth (hereinafter referred to as base material 40)
After applying the adhesive 30 to the substrate, it may be bonded to the recording film 11 as shown in the partial cross-sectional views of FIGS. 2 and 3. The substrate can also be provided with scratch resistance and bend resistance functions for optical recording media. Furthermore, when the base material is in the form of a tape, productivity can be further improved by applying a pressure-sensitive adhesive on one or both sides of the base material and sequentially passing it through the process of laminating optical recording media.

The adhesive used in the present invention is applicable not only to write-once optical recording media that cause shape changes or optical changes in the recording film due to heat generated by the irradiation of the recording reluzer, but also to It can also be used in rewritable optical recording media, such as a magneto-optical method that detects a signal, or a phase change method that detects the presence or absence of a signal based on a change in optical properties such as refractive index. In particular, if the adhesive according to the present invention is used for a recording medium whose shape is changed by irradiation with laser light, recording pits can be easily formed, so high recording sensitivity can be obtained, making it particularly suitable. Can be used. Note that an auxiliary layer may be provided on one or both sides of the recording film for the purpose of improving the performance of the optical recording medium.

[Example] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 Two disc-shaped polycarbonate substrates obtained by injection molding were prepared, and Pt-5e was coated on the surface of the peak substrate with the guide groove.
-A recording layer made of Bi was formed. With both recording layers facing inside, the two substrates were bonded using rubber-based double-sided adhesive tape #821 manufactured by Dainippon Ink & Chemicals Co., Ltd. to obtain an optical recording medium having the structure shown in FIG. 3. When single frequency information of IMHz was recorded and reproduced using the optical recording medium, recording pits were easily formed and good characteristics of CNR=48 dB were exhibited. Further, no deterioration of the characteristics was observed even when the optical recording medium was left in an atmosphere of 70° C. and 80% R)I for 1000 hours.

Example 2 In place of the adhesive tape of Example 1, a third acrylic double-sided adhesive tape MC-2000 manufactured by Nitto Electric Industries, Ltd. was used.
The optical recording medium having the structure shown in the figure showed good characteristics of CNR=49 dB in the recording and reproducing operation of single frequency information of IMHz. Further, the optical recording medium is 70'C, 80%
R) No deterioration of characteristics was observed even after being left in an I atmosphere for 1000 hours.

Example 3 Silicone rubber with a molecular weight of 500,000 and molecular weight 2
A toluene/xylene mixed solution of a silicone adhesive consisting of 000 silicone resin was coated on one side of a 100 μm thick polyester film (substrate) by a bar coating method. This film was baked at 150°C for 3 minutes to produce an adhesive film with an adhesive thickness of 100 μm. Next, instead of using the adhesive tape of Example 1, the adhesive side of the silicone-based adhesive film was gradually pressed to prevent air bubbles from entering the recording layer, thereby obtaining an optical recording medium having the structure shown in Fig. 2. . When information was recorded and reproduced using the optical recording medium, the laser power required for recording was 1/2 that of Examples 1 and 2, and CNR = 52 dB.

In addition, even when left in an atmosphere of 185% R1 at 70° C. for 1000 hours, the characteristics did not deteriorate.

Example 4 A material obtained by adding 2% by weight of benzoyl peroxide based on the non-volatile components to the toluene/xylene mixed solution of the silicone adhesive described in Example 3 was coated on one side of a 100 μm thick polyester film by the barcode method. did. This film was heated to 130°C for 3 minutes, then heated to 180°C.
By baking for 3 minutes at C, the glue thickness is 100 μm.
An adhesive film was prepared. The optical recording medium having the structure shown in FIG. 2 using this adhesive film exhibited extremely good recording/reproducing characteristics and stability over time, as in Example 3.

Comparative Examples In place of the silicone-based adhesive in Example 2, it was not possible to record information using a two-liquid Tosho.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an optical recording medium with good recording and reproducing characteristics and high reliability over a long period of time with good productivity. In particular, high recording sensitivity can be obtained in optical recording media in which recording is performed by changing the shape of the recording film caused by laser light.

[Brief explanation of the drawing]

1 to 3 are schematic cross-sectional views showing examples of optical recording media according to the present invention, and FIGS. 4 and 5 are schematic cross-sectional views showing conventional examples of optical recording media. lO・・・・・・・・・・・・・・・Substrate, 11・
・・・・・・・・・・・・・・・Recording film, 12...
・・・・・・・・・・・・-Protective film, 30・・・・・・
......Adhesive layer, 40...
··········Base material. Patent applicant Rira Co., Ltd. Attorney Kendai Honda Figure 1/-10 Figure 2 Figure 6 ρ10

Claims (3)

[Claims] (1) An optical recording medium formed by bonding a plurality of substrates each having a recording film on at least one surface via an adhesive. (2) The optical recording medium according to claim 1, wherein the adhesive is a silicone adhesive. (3) The optical recording medium according to claim 1 or 2, wherein recording is performed by changing the shape of the recording film by laser light.