JPS62185263A - Information recording medium - Google Patents

Abstract

PURPOSE:To maintain high sensitivity even after a titled recording medium is preserved in an unrecorded state for a long period of time under severe conditions of temp. and humidity by providing a layer consisting of chlorinated polyolefin contg. a heat stabilizer between a substrate and recording layer. CONSTITUTION:The chlorinated polyolefin layer of the information recording medium constituted by providing the recording layer which permits writing and/or reading of the information by a laser via the chlorinated polyolefin layer on the substrate is incorporated therein with the heat stabilizer for the chlorinated polyolefin. The heat stabilizer is exemplified by an epoxy compd., basic lead salt, org. tin compd., stearate, etc., which may be used either independently or in combination. The content of the heat stabilizer is preferably in a 0.01-10wt% range and more particularly preferably in a 0.5-3wt% range by the weight of the chlorinated polyolefin.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an information recording medium on which information can only be written and/or read using a high energy density laser beam.

[Technical Background of the Invention] In recent years, information recording media that use high energy density beams such as laser light have been developed and put into practical use. This information recording medium is called an optical disk, and can be used as a video disk, an audio disk, a large-capacity still image file, and a large-capacity computer disk memory.

The basic structure of an optical disk is a disc-shaped transparent substrate made of plastic, glass, etc., and a Bi
, a recording layer made of metal or semimetal such as Sn, In, Te, etc. Note that an undercoat layer made of a polymeric substance is usually applied to the surface of the substrate on which the recording layer is provided, from the viewpoint of improving the flatness of the substrate, improving the adhesion with layer B, or improving the sensitivity of the optical disc. Or an intermediate layer is provided.

Information is written on an optical disk by irradiating the optical disk with a laser beam, for example.
The irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in a physical or chemical change that changes its optical properties, thereby recording information. Information is also read from an optical disc by irradiating the optical disc with a laser beam, and the information is reproduced by detecting reflected or transmitted light depending on changes in the optical characteristics of the recording layer.

Recently, as a disk structure for protecting the recording layer, a recording layer is provided on at least one of the two disk-shaped substrates, and the recording layer is located inside the two disk-shaped substrates. Also, an air sandwich structure has been proposed in which a ring-shaped inner spacer and a ring-shaped outer spacer are joined to form a space. In an optical disc having such a structure, the following information is available. Because I is not in direct contact with the outside air, and information is recorded and reproduced using laser light that passes through the substrate, the recording layer is generally subject to physical or chemical damage, or dust may adhere to its surface. This will not interfere with recording or reproducing information.

Information recording media are extremely useful in various fields as described above, but it is desired that their sensitivity be as high as possible.

Conventionally, information recording media have been proposed in which a chlorinated polyolefin layer is provided on a substrate and a recording layer is provided on top of the chlorinated polyolefin layer for the purpose of improving recording sensitivity (Japanese Patent Publication No. 57-39
In other words, by providing a layer of chlorinated polyolefin such as chlorinated polyethylene or chlorinated polypropylene between the substrate and the recording layer, thermal energy caused by laser beam irradiation is thermally conducted from the recording layer to the substrate, etc. Techniques are already known to reduce losses due to Furthermore, when optical discs with a chlorinated polyolefin layer are used to write information by irradiating the optical disc with a laser beam, the temperature of the irradiated area of the chlorinated polyolefin layer increases locally, resulting in the generation of gas and the formation of pits. It also has the advantage of being easy.

However, chlorinated polyolefins lack thermal stability under various storage environmental conditions, especially under harsh environmental conditions such as temperature and humidity, as chlorine tends to gradually desorb over time. Therefore, information recording media with a chlorinated polyolefin layer between the substrate and the recording layer have excellent recording sensitivity at the time of manufacture, but they cannot be stored for long periods in harsh environmental conditions of temperature and humidity in an unrecorded state. After that, recording sensitivity tends to decrease.

[Object of the Invention] An object of the present invention is to provide an information recording medium with increased recording sensitivity.

A particular object of the present invention is to provide an information recording medium with stable and good recording sensitivity.

[Summary of the Invention] The present invention provides an information recording medium in which a recording layer on a substrate is provided with a recording layer on which information can be written and/or read by a laser via a chlorinated polyolefin layer. The information recording medium contains a chlorinated polyolefin heat stabilizer.

[Effects of the Invention] The information recording medium of the present invention has significantly improved recording sensitivity by providing a layer made of chlorinated polyolefin containing thermal stabilization between the substrate and the recording layer in contact with the recording layer. ,
Furthermore, even after being stored in an unrecorded state under harsh environmental conditions of temperature and humidity for a long period of time, it is highly sensitive and good recording is possible.

[Detailed Description of the Invention] The information recording medium of the present invention can be manufactured, for example, by the following method.

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. Optical properties, flatness, processability of the substrate,
In terms of ease of handling, stability over time, and manufacturing cost,
Examples of substrate materials include glass such as soda lime glass; acrylic resins such as cell cast polymethyl methacrylate and injection molded polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers; epoxy resins and polycarbonates. can be mentioned. Among these, polycarbonate is preferred in terms of dimensional stability, transparency, and flatness.

On the substrate surface on the side where the recording layer is provided, there are four planar galleries,
An undercoat layer may be provided for the purpose of improving adhesive strength and preventing deterioration of the recording layer. Examples of materials for the undercoat layer include polymethyl methacrylate, acrylic acid/methacrylic acid copolymer, styrene/maleic anhydride copolymer, polyvinyl alcohol, N-methylolacrylamide, styrene/sulfonic acid copolymer, styrene/maleic anhydride copolymer, Vinyl toluene copolymer, chlorosulfonated polyethylene, nitrocellulose, polyvinyl chloride, polyester, polyimide, vinyl acetate/vinyl chloride copolymer, ethylene/
Vinyl acetate copolymer, polyethylene, polypropylene,
Polymeric substances such as polycarbonate Organic substances such as nitrogen coupling agents: j5 and inorganic oxides (Si02.A
Examples include inorganic substances such as MgFz, inorganic fluoride (MgFz), and inorganic fluoride (MgFz).

In the case of a glass substrate, in order to prevent adverse effects on the recording layer due to alkali metal ions and alkaline earth metal ions liberated from the substrate, wood-philic groups such as styrene/maleic anhydride copolymer and/or maleic anhydride are added. Preferably, a subbing layer consisting of a polymer containing groups is provided.

The undercoat layer can be formed by, for example, dissolving or dispersing the above-mentioned substance in a suitable solvent, and then applying this coating solution to the substrate surface by a coating method such as spin cording, dip coating, or extrusion coating. The thickness of the undercoat layer is generally within the range of 0.01 to 20 gm, preferably within the range of 0.1 to 10 gm.

Alternatively, a pre-groove layer may be provided on the substrate (or undercoat layer) for the purpose of forming tracking grooves or irregularities representing information such as address signals.As the material of the pre-groove layer, acrylic A mixture of at least one type of acid monoester, diester, triester, and tetraester (or oligomer) and a photopolymerization initiator can be used.

The pre-groove layer is formed by first coating a mixture of the above acrylic ester and polymerization initiator on a precisely made matrix (stamper), then placing the substrate on top of this coating solution layer. Then, the liquid layer is cured by irradiation with ultraviolet rays through the substrate or the matrix, thereby fixing the substrate and the liquid phase.

Next, by peeling the substrate from the mother mold, a substrate provided with a pregroove layer is obtained. The layer thickness of the pre-groove layer is generally within the range of 0.05 to 10JLm, preferably within the range of 0.1 to 50JL111.

Furthermore, if the substrate material is plastic, the pregroove may be directly provided on the substrate by injection molding, extrusion molding, or the like.

A chlorinated polyolefin layer is then provided on the substrate (or on the subbing layer or bleed groove layer), or on the pregroove if it is provided directly on the substrate.

The chlorinated polyolefin has a chlorination rate of 30% or more, preferably 50% or more, particularly preferably 50 to 80%.
Chlorinated polyethylene and chlorinated polypropylene within the following range are particularly preferred from the viewpoint of thermal stability and solubility.

The chlorinated polyolefin layer can be provided by dissolving the chlorinated polyolefin in a solvent to prepare a coating liquid, and then applying this coating liquid onto the substrate by a known method.

As a solvent for dissolving chlorinated polyolefin,
Toluene, xylene, ethyl acetate, butyl acetate, cellosolve acetate, methyl ethyl ketone, 2-dichloroethane, methyl isobutyl ketone, cyclohexanone,
Examples include cyclohexane, tetrahydrofuran, ethyl ether, and dioxane.

It is also possible to further add various additives such as plasticizers and lubricants to these coating liquids depending on the purpose.

Examples of the coating method include a spray method, a spin code method, a dip method, a roll coat method, a blade coat method, a doctor roll method, and a screen printing method.

A chlorinated polyolefin layer can be formed on the substrate (or undercoat layer) by applying it to the substrate surface (or undercoat layer) to form a coating film and then drying it. The thickness of the chlorinated polyolefin layer is preferably in the range o,oos to loILm.

The present invention is characterized in that the chlorinated polyolefin layer contains a thermal stabilizer in order to improve the thermal stability of the chlorinated polyolefin.

As examples of such thermal stabilizers, mention may be made of epoxy compounds, basic lead salts, organotin compounds and stearates. The heat stabilizer can be used by being added to the above-mentioned chlorinated polyolefin coating solution. These may be used alone or in a mixed state.

The content of the heat stabilizer is preferably within the range of 0.01 to 10% by weight based on the chlorinated polyolefin,
Particularly preferably, it is within the range of 0.5 to 3% by weight.

As the epoxy compound used in the present invention, those generally used as stabilizers or plasticizers for vinyl chloride can be used. For example, as epoxy compounds having one epoxy group in one molecule, allyl glycidyl ether, ethyl Examples include glycidyl ether, methylglycidyl ether, and phenylglycidyl ether.

Further, examples of epoxy compounds having two or more epoxy groups in one molecule include compounds represented by the following structural formulas (a) to (0).

(However, n is an integer from 0 to 15) and an esterified product of (a) and a fatty acid such as soybean oil, castor oil, or coconut oil, (b) (where X is C1 or Br) (c) (d) (e) (However, n is an integer of 0 to 2) (However, R is hydrogen or a methyl group, and n is 1 to 1
(i) (However, R is hydrogen or a methyl group) (j) (However, m and n are each an integer from 1 to 1O) (n) 0 Note that these The epoxy compound may be used alone or in the form of a mixed FB. Furthermore, the epoxy resin used in the invention is not limited to the above-mentioned compounds, and any resin having one or more epoxy groups in one molecule can be used.

Examples of the basic lead salts used in the present invention include:
Examples include dibasic lead phosphite, dibasic lead carbonate, dibasic lead stearate, tribasic lead sulfate, and tribasic lead maleate.

Examples of the organic tin compounds used in the present invention include dialkyltin (e.g., dimethyltin, diethyltin), diaryltin (e.g., diphenyltin, di-lutelyltin, di-p-xylyltin), tetraalkyltin (e.g., Examples include tetramethyltin, tetraethyltin), tetraaryltin (eg, tetraphenyltin), and dialkyltin malate.

Examples of stearates used in the present invention include cadmium stearate, magnesium stearate, aluminum stearate, barium stearate, and lead stearate.

Next, a recording layer is provided on the chlorinated polyolefin layer.

An example of the material used for the recording layer is Te.

Metals such as Zn, In, Sn, Zr, An, Cu, Au;
Metalloids such as Bi, As, and Sb; Semiconductors such as Ge and Si;
and alloys thereof or combinations thereof. Also, sulfides of these metals or metalloids,
Compounds such as oxides, borides, silicon compounds, carbides and nitrides: and mixtures of these compounds with metals can also be used in the recording layer.

The recording layer is formed on the substrate using the above-mentioned materials by a method such as vapor deposition, sputtering, or ion blasting. The recording layer may be a single layer or a multilayer, and its layer thickness is generally 100 to 550 from the viewpoint of optical density required for optical information recording.
The range is 0X.

Note that the surface of the substrate opposite to the side on which the recording layer is provided is coated with inorganic substances such as silicon dioxide, tin oxide, and magnesium fluoride to improve scratch resistance and moisture resistance.
8. A thin film made of a polymeric substance such as a plastic resin or a photocurable resin may be provided by a method such as vacuum deposition, sputtering, or coating.

In this way, it is possible to produce an information recording medium having a basic structure in which a substrate, an undercoat layer, a chlorinated polyolefin layer, and a recording layer are laminated in this order.

In addition, in Moeju's bonded type recording media,
It can be manufactured by joining two substrates having the above configuration using an adhesive or the like. In addition, in an air sandwich type recording medium, at least one of the two disc-shaped substrates has the above structure,
It can be manufactured by joining via a ring-shaped outer spacer and an inner spacer.

Next, Examples and Comparative Examples of the present invention will be described.

[Example 1] A disc-shaped polycarbonate substrate with groups formed by injection molding (outer diameter: 130 mm, inner diameter: 15 mm, thickness:
2mm, track pitch, 61Lm) group surface,
A coating solution having the following composition was applied by a spin cord method and then dried to provide a chlorinated polyethylene layer having a dry thickness of 0.021 part m.

-・Fabric liquid assembly t (J part) Chlorinated polyethylene 0.2 part + C2H
A −x C1xhir x=,7. n=200 Tribasic lead maleate 0.002 parts Methyl ethyl ketone 10 parts Cyclohexane 100 parts Next, In, Au and GeS were added on the chlorinated polyethylene layer in proportions of 65%, 5% and 30% by weight, respectively. Co-evaporation was performed to form a recording layer with a thickness of 300X. At this time, the heating current flowing through the Au evaporation source was controlled so that the Au concentration was high on the substrate side and decreased as it approached the surface of the recording layer.

In this way, an information recording medium consisting of a substrate, a chlorinated polyethylene layer, and a recording layer was manufactured in this order.

[Example 2] In Example 1, the coating liquid! [An information recording medium was produced in the same manner as in Example 1, except that an epoxy compound (Epicote 812 manufactured by Nisiel Chemical Co., Ltd.) was used instead of tribasic lead maleate as the I component.

[Comparative Example 1] An information recording medium was produced in the same manner as in Example 1 except that the coating liquid composition was 2 parts by weight of raw chlorinated polyethylene and tribasic lead maleate was not used. did.

[Evaluation of information recording medium] For each information recording medium obtained, (a) *at the time of manufacture.

(b) 6 in a constant temperature and humidity chamber at a temperature of 60°C and a humidity of 90% RH.
0 day broadcast 21tti! , was evaluated by the following sensitivity test.

While rotating the information recording medium at a rotation speed of 515 rpm,
When information is recorded by forming pits in the recording layer using a semiconductor laser (wavelength: 820 parts m) under the conditions of , 25 MHz and a duty ratio of 1:l, the pit formation is as small as possible. The laser output intensity was measured.

The results obtained are summarized in Table 1.

Table 1 Sensitivity (m W ) At the time of manufacture After 60 days Example 1 5 5 Comparative Example 1
5 6 As is clear from the results shown in Table 1, the information recording media of the present invention (Example 1 and Example 2) maintain sensitivity even after being exposed for 60 days at 60°C and 90% RH. was not decreased at all, and the stability of recording sensitivity over time was improved.

Claims (1)

[Claims] 1. An information recording medium in which a recording layer on a substrate is provided with a recording layer on which information can be written and/or read by a laser through a chlorinated polyolefin layer, wherein the chlorinated polyolefin layer contains chlorine. An information recording medium characterized by containing a heat stabilizer made of chemically modified polyolefin. 2. Information according to claim 1, characterized in that the heat stabilizer is at least one type selected from the group consisting of epoxy compounds, basic lead salts, organic tin compounds, and stearates. recoding media. 3.Thermal stabilizer is 0 for chlorinated polyolefin
．． 2. The information recording medium according to claim 1, wherein the content is within a range of 0.01 to 10% by weight. 4. The heat stabilizer is at least one type selected from the group consisting of dibasic lead phosphite, dibasic lead carbonate, dibasic lead stearate, tribasic lead sulfate, and tribasic lead maleate. 2. The information recording medium according to claim 1, wherein the information recording medium is a basic lead salt of. 5. Claims characterized in that the heat stabilizer is at least one organic tin compound selected from the group consisting of dialkyltin, diaryltin, tetraalkyltin, tetraaryltin, and dialkyltin malate. The information recording medium according to item 1. 6. A patent claim characterized in that the heat stabilizer is at least one stearate selected from the group consisting of cadmium stearate, magnesium stearate, aluminum stearate, barium stearate, and lead stearate. The information recording medium according to item 1 of the scope. 7. The information recording medium according to claim 1, wherein the chlorinated polyolefin is chlorinated polyethylene or chlorinated polypropylene.