JPS62226442A - Information recording medium - Google Patents

Abstract

PURPOSE:To improve the durability and recording sensitivity of a recording medium and to decrease reading errors by providing a recording layer contg. further specific metals in addition to In and germanium sulfide. CONSTITUTION:The recording layer contg. at least one kind of the metal selected from the group consisting of Pb, Sn, Zn, Bi, and Sb in addition to In and GeSx (where x is the number in a 0<=x<=2 range) is provided on a substrate (or substrate provided with an under coat layer, pregroove layer or intermediate layer). The content of In in the recording layer is 30-80wt%, more preferably 50-80wt%. The content of GeSx is 10-50wt%, more preferably 20-40wt%. The amt. of the metal to be added is 0.1-30wt%, more preferably 1-15wt%. The mixing ratio of the metal with In is preferably 1:80-1:4 by weight. The metal is preferably incorporated in the form of the alloy with In into the recording layer. Furthermore, Au is preferably incorporated therein in such a manner that the concn. thereof is higher on the substrate side.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] Shukan IJJ relates to information recording media in which information can be recorded and/or read using a high energy density laser beam.

[Technical Background of Light II] In recent years, information recording media that use a high energy density beam of laser photons have been developed and are being put into practical use. This information recording medium is called an optical disc, and includes video discs, audio discs, and even optical discs.
It can be used as a computer disk memory.

An optical disk consists of a disk-shaped transparent substrate made of plastic or glass (9), and a metal such as Bi, Sn, In, Te, etc. or It has a recording layer made of metal.The surface of the cover plate (on the side where the recording layer is provided) usually has a
The direction of adhesive force with the recording layer or the optical disc's
+ From the viewpoint of improving If, etc., a coating layer or an intermediate layer made of a polymeric substance is provided.

1) Writing information onto an optical disk is performed by, for example, irradiating the optical disk with a laser beam, and the irradiated portion of the recording layer absorbs the light and locally increases in temperature, resulting in physical or Information is recorded by making chemical changes that change its optical properties. Reading of information from an optical disk is also performed by irradiating the optical disk with a laser beam, and information is generated tIi by detecting reflected light or transmitted light according to changes in the optical characteristics of the recording layer.

Recently, as a disk structure to protect the recording layer, a recording layer is provided on at least one of the two disk-shaped substrates, and the recording layer is placed close to the inside of the two disk-shaped substrates. 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 optical discs with such a structure, the recording layer is not in direct contact with the outside air, and the recording of information is performed using a laser beam that passes through the substrate.In general, the recording layer is physically Or, it will not be damaged chemically, or dust will adhere to its surface, which will impede the recording of information.

As mentioned above, information recording media have a very high utility value (<17 it) in various fields, but it is desired that their recording sensitivity be as high as possible.
It is rare that the recorded information can be read with the highest possible accuracy. Furthermore, it is desired that the recording layer has high durability against physical or chemical changes.

Conventionally, a layer made of a mixture of a metal such as In and GeS (where X is a positive real number) has been used as a recording layer of an information recording medium for the purpose of increasing recording sensitivity or reading accuracy. It is known to provide a
+) each publication).

However, in such a recording layer, pits may not be sufficiently formed in the recording layer even if laser light is irradiated during recording of information. This is because even though the laser beam output of 1" is sufficient to melt the recording layer, pits are difficult to open in the melted recording layer material, and the material solidifies in the same position. Therefore, it was necessary to increase the output of the laser beam by 1, and it was difficult to ensure that the sensitivity of the recording medium was sufficiently high. mold -, tr+
It: Not: I+ + Old ILj ノ, r number A h
This causes an error in il 11%, causing a problem.

Furthermore, there are problems such as the metal that forms the recording layer undergoing physical or chemical changes over time, which lowers the recording sensitivity and reading accuracy of the recording medium. It was hard to say.

[Objectives of the Invention] One object of the present invention is to provide a highly durable information recording medium that has high sensitivity and reduced reading errors even after long-term storage under harsh environmental conditions such as temperature and humidity. This is the first objective.

Another object of the present invention is to provide an information recording medium with high recording sensitivity.

Furthermore, the purpose of the FFI 11 is to provide an information recording medium with reduced reading errors.

[Summary of the Invention] One aspect of the present invention provides an eS
z (where X is a number in the range of 0<x≦2), the recording layer further includes Pb, Sn.

The present invention provides an information recording medium characterized by containing at least one metal selected from the group consisting of Zn, Bi, and S.

[Effects of the Invention] As a result of further research on information recording media, the present inventor discovered that a recording layer that can be obtained by placing a recording layer containing a specific metal in addition to indium and germanium sulfide on a nof plate. The present invention was achieved by discovering that the durability and recording sensitivity of the medium can be further increased and reading errors can be reduced.

That is, according to the information recording medium of the present invention, In is Pb
, Sn, Zn, Bi and/or sb, it has the ability to suppress the physical or chemical changes of In over time, increasing the durability of the recording layer. be able to. In particular, by containing In and the metal as a homogeneous mixture in the alloy form IE1 in the recording layer, a state in which different metals are mixed in the In case is created. The stability of the layer over time can be significantly increased.

Therefore, even when stored for a long period of time under harsh environmental conditions such as temperature and humidity, it can maintain a high level of sensitivity and has excellent durability with little reading error. It is.

In addition, by making In a mixture with L metal, In
Since the melting point can be lower than that of 1t, it is possible to obtain a high C/N1t (ratio of output level of carrier and noise) without reducing the output of laser light.
Sensitivity can be increased. At the same time, since well-shaped pits can be easily formed in the recording layer, the pit error rate (BER) during information reading can be significantly reduced.

In particular, when the recording needle further contains Au with a high e1 gradient on the large plate side and a chlorinated polyolefin layer is provided between the substrate and the recording layer, the high surface tension of 1,7 Au and the chlorinated polyolefin Due to the synergistic effect with the thermal insulation properties of the layer, high C/N ratios can be obtained at low laser powers.

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

The substrate used in the present invention can be arbitrarily selected from various materials used as substrates for conventional information recording media. From the viewpoint of the optical properties of the substrate, +i-plane properties, processability, handleability, stability over time, manufacturing cost, etc.) J (Examples of board materials include soda lime glass T glass; cell cast polymethyl methacrylate; Acrylic resins such as injection molded polymethyl methacrylate; vinyl chloride resins such as polyvinyl chloride and vinyl chloride copolymers;
Mention may be made of epoxy resins; and polycarbonates. Among these are degree stability, transparency 11 and 7
From the viewpoint of surface properties, polymethyl methacrylate, polycarbonate, epoxy resin and glass are preferred.

The surface of the substrate on which the recording layer is provided is coated with a 1t surface modified R.
A YIT layer may be provided for the purpose of improving adhesion and preventing deterioration of the recording layer. Examples of materials for the coating layer include polymethyl methacrylate, acrylic liquor and methacrylic acid copolymer. Combined.

Polymer substances such as nitrocellulose, polyethylene, polypropylene, and polycarbonate-9; organic substances such as silane coupling agents; and 'y#, organic oxides (Si02
, Al2O2, etc.), and inorganic substances such as inorganic fluoride (MgF2).

(When the plate material is glass) (In order to prevent the adverse effects on the recording layer from alkali metal ions and alkaline earth metal ions that are separated from handling, use a styrene/maleic anhydride copolymer, etc.) It is desirable that an F?a layer made of a polymer having wood-philicity (wood-philicity) and/or maleic anhydride groups is provided.

For example, the coating layer is prepared by dissolving or dispersing the l-metabolic material in a suitable solvent, and applying this "14J solution to the plate by applying spin code, D/7' coat, extrusion coat, etc." Form 1 by applying it to the surface
&can do.

In addition, a pre-groove layer may be provided on the )1 (plate (or coating layer)) for the purpose of forming unevenness representing information such as tracking grooves or address signals. The material for the pre-groove layer is at least one monomer (or oligomer) selected from monoesters, diesters, triesters, and tetraesters of acrylic acid.
Mixtures of the compound and the photoinitiator can be used.

The pregroove layer is first formed using a precisely made In! (
After applying a mixture of the acrylic ester and polymerization initiator described in 1- to the stanbar) and placing a substrate on this coating liquid layer J-, the substrate or I;Iη! The liquid layer is cured by irradiation with ultraviolet rays through the substrate (1-4).
By performing lf21, a plate provided with a pre-groove layer is obtained. The thickness of the pre-groove layer is generally within the range of 0.05 to 1100 IL, preferably 0.1 to 50 gm. If the substrate material is plastic, the pregroove may be provided directly on the substrate 1- by injection molding, extrusion molding, or the like.

), (plate (or coating layer or pre-groove layer) L,
Alternatively, (if the pregroove is directly provided on the plate, the pregroove L may be further provided with an intermediate layer made of various known materials such as chlorinated polyolefin).

In particular, when the material of the intermediate layer is chlorinated polyolefin, it is possible to reduce the loss of thermal energy due to laser beam irradiation due to heat conduction from the recording layer to the substrate, and the chlorinated polyolefin layer Gas is generated from the irradiated area, making it easier to form pits, thereby making it possible to further reduce the pit error rate and further improve the recording sensitivity.

The chlorinated polyolefin used as the intermediate layer material has a monolayer chlorination rate of 30% or more, preferably 5% or more.
It has a chlorination rate of 0% or less, particularly preferably 50 to 70%. In addition, from the viewpoint of thermal stability and solubility, chlorinated polyethylene and chlorinated polypropylene are particularly preferred among these 714 hydrogenated polyolefins.

The chlorinated polyolefin layer can be provided by dissolving the chlorinated polyolefin in a solvent to prepare a coating solution, and then applying the solution to the substrate.

1′! ! Solvents for dissolving hydrogenated polyolefin include toluene, xylene, ethyl acetate, butyl acetate,
Cellosolve acetate, methyl ethyl ketone, ■, 2-
Diglolethane, methyl isobutyl ketone, cyclohexanone, cyclohexane, tetrahydrofuran, ethyl ether, dioxane and the like can be mentioned.

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

The coating methods include spray υ:, spin code D1.
Dip method, roll coating υ:, blade coating method, doctor roll method, screen printing method, etc. ・By coating the substrate surface (or coating layer) to form a coating film and then drying it, the substrate (or coating layer) A chlorinated polyolefin layer can be formed on L. f1! The layer thickness of the hydrogenated polyolefin layer is generally in the range of 10 to 1000, and preferably in the range of 100 to 500.

Next, a recording layer, which is a characteristic feature of the present invention, is provided on the substrate (or coating layer or chlorinated polyolefin layer).

The recording layer is basically made of In and Ge5X (
However, in addition to (X is a number in the range 0<x≦2),
At least one metal selected from the group consisting of Pb, Sn, Zn, Bi, and S is used. Among these metals, Sn is particularly preferred.

The content of In in the recording layer is generally 30 to 8
0 tonj 7%, preferably within the range of 50 to 80 H,H:%. In addition, Ge5xC (where X is a number in the range of 0<x≦2), lj is generally lO~5
0 ton, 1. 'L%, preferably within the range of 20 to 40%, 1%.

Further, the metal L is generally contained in the recording layer in an amount of 1-1% of O01-30T, preferably 1-15T<+1
It is within the range of t%. The mixing ratio of metal L to In (metal:In) is generally 1:300 to 1 by weight.
:2, preferably l:80 to l:4.

In the undeveloped IJl, the above metal may be directly contained in the recording layer by co-evaporation with In;
In order to exist in a uniform mixture with In, it is preferable to form an alloy with r-In and then vapor-deposit this alloy so that it is contained in the recording layer.

In the present invention, the recording layer has a melting point and a melting point of 3.
A metal having a surface tension of 600 dyn/c+* or higher within a temperature range of 00° C. or higher may be contained.

In particular, the metal with high surface tension is Au.

And, (if the degree e on the plate side exists with a concentration gradient 1t11 higher than the concentration on the surface of the recording layer,
Due to the high surface tension of Au, well-shaped pits can be easily formed in the recording layer without reducing the output of laser light, and reading errors can be reduced when reading information. This is preferable because it can reduce the amount of water.

Note that the concentration of a metal having a high L surface tension in the recording layer refers to the ratio of the metal present in a cut surface when the recording layer is cut in a horizontal direction. Further, the recording layer surface side refers to the surface of the recording layer on the side that is not in contact with the substrate.

Metals with high surface tension of Au'p are 0.1 to 30
Contamination contained in the recording layer within the range of weight %, preferably 1-x
S ball: within the range of 1%.

For details of the metals with high surface tension and the concentration gradient in the recording layer, please refer to Japanese Patent Application No. 114733/1982 and Japanese Patent Application No. 1211/1989 filed in February 1988 by the present applicant. It is listed in each IJJ detailed chart.

The recording layer is formed on 1 m of the substrate using a method such as steaming, sputtering, or ion blasting using the material listed below.
In order to increase the concentration of metals with high surface tension on the radish side, for example, during the vapor deposition process, the heating current flowing through the evaporation source of the metal with high surface tension can be controlled to reduce the amount of metal vaporized. This can be done by changing.

The recording layer may be a middle layer or an intermediate layer, but its layer thickness is generally 500 to 150 ml from the viewpoint of optical density required for optical information recording.
It is in the range of 00s.

1) Since the metal of the Sn cap exists as a uniform mixture with In in the recording layer, especially in the form of an alloy, physical or chemical changes in In over time are suppressed, and the durability of the recording layer is improved. is facing. Therefore, especially the temperature
Even when stored for a long time under harsh environmental conditions such as humidity, information recording media can maintain high sensitivity and have little reading error.

Furthermore, the In alloys listed in 1- are generally more JIG than In.
u^, '+tsu L2, na store +--) 1'N〆, 611th feeling ++j+-1-1" A high C/N ratio (ratio of output level of carrier and noise) can be obtained without soot. , sensitivity can be increased, and at the same time, well-shaped bits can be easily formed in the recording layer.Furthermore, the pit error rate (BER) during one reading of information can be significantly reduced.

The surface of the plate opposite to the side on which the recording layer is provided is coated with an inorganic substance such as silicon dioxide, tin oxide, or magnesium fluoride to improve scratch resistance and moisture resistance. A thin film made of a polymeric material of a resin acid photocurable resin may be provided by dry vapor deposition, sputtering, or a coating method.

In this way, an information recording medium having a basic configuration in which the substrate and the recording layer are laminated in this order can be manufactured.

Note that a bonded type recording medium can be manufactured by bonding two substrates having the above structure using an adhesive cap.

In addition, in the case of an air sandwich type recording medium, at least one of the disk-shaped substrates has the structure described in (1). It can be manufactured by

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

However, each of the following does not limit the present invention.

[Example 1] Disc-shaped polycarbonate substrate (outer diameter: 120 mm, inner)
l: 15mm, thickness: 1.2mm) InllS on the surface
n alloy (In:5n=90:10, m jI'L ratio)
and GeS are co-evaporated to form an In*sn alloy and GeS.
A recording layer consisting of the following was formed to a thickness of 100 oz. At this time, the market ratio of the In-Sn alloy and GeS recording layers was 70% and 30%, respectively.

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

[Comparative Example 1] A recording layer made of In and GeS was formed with a layer thickness of 1000^ using the same method used in Example 1 (co-evaporation of In and GeS on the substrate of the plate and layer). . At this time, 1 in the In and GeS recording layers is R+1:i, respectively.
The ratio was 70% and 30%.

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

[Evaluation of information recording media] (1) Sensitivity test Regarding each information recording medium obtained, (a) at the time of manufacture.

(b) 1 in a constant temperature and humidity chamber at a temperature of 60°C and a humidity of 90% RH.
After being left for 40 minutes, binary information was recorded at a linear velocity of 5 thickness/second, and the ratio of carrier to noise output level (C/NLt) was determined.
The laser output at which the maximum value and the C/N ratio at that time are set to 1
X was determined.

(2) Reading error test information? Regarding the information recording medium on which M is recorded, see L (a)
and (b), the Nakamichi disk (Nak
amichi @Disk) Evaluation device 220M5-10
00 was used to measure the error signal in the il raw signal, i.e., the pit error rate (BER).

The measurements were made on a recording medium recorded with an output of 5 mW.
Band ItJ l 0K by spectrum analyzer
It was measured under the condition of Hz.

The results obtained are summarized in Table 1.

Table 1 Example 1 Comparative Example 1 Manufacturing output (mW) 7 8C/N1
t(dB) 50 50B E RI O-
” IO-6 output (mW) 7
9C/N1t (dB) 50
45BERl O-u 1o-3 As is clear from the results shown in Table 1.

The information recording medium of the present invention (Example 1) was able to obtain a high C/N ratio with low recording power, and was behind in recording sensitivity. Also,
The HER (p'f) is extremely small and the reading error is reduced.Also, the BER value does not change at all even after being left for 14 hours under the conditions of 60℃ and 90%RH, and the durability is particularly excellent. was.

On the other hand, the information recording medium for comparison (Comparative Example 1) required high recording power and had poor recording sensitivity. In particular, the C/N ratio decreased over time, and the BER Ida1 increased, resulting in poor durability.

[Example 2] A coating solution having the composition shown below was applied to the same plate surface as that used in Example 1 by a spin cord method, and then dried to obtain a film with a final film thickness of 150 mm. Chlorinated polyethylene 9F or less margin coating 1 (4-component Mt composition (Tunj, J part) Chlorinated polyethylene 0.2 parts A=Ct
Ha-de C1Ω, y U-“y
=l, n=200 Methyl ethyl ketone 10 parts cyclohexane 100 parts This Ii! A recording layer made of In5Sn alloy and GeS was formed by performing the same operation as the hydrogenated polyene 9F method.

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

[Comparative Example 2] A chlorinated polyethylene layer was provided on the same plate as that used in Example 2 by performing the same operation as in Example 2.

Next, this 41! , a polyethylene layer l;
A recording layer consisting of In and GeS was formed with a thickness of 100 mm by co-evaporating In and GeS. At this time In and G
In the recording layer of eS, the ratios of ; and 1 were 70% and 30%, respectively.

In this way, based on 1 ho 1 &. jiA hydrogenated polyene.

[Evaluation of Information Recording Medium] Each of the obtained information recording media was evaluated by conducting the sensitivity test and reading error test described above. In the reading error test, the BER was measured on a recording medium recorded with an output of 6 mW.

The results obtained are summarized in Table 2.

Margin below Table 2 Example 2 Comparative example 2 Manufacturing output (mW) 6 BC/
N1t (dB) 55 50B E R
l O -" 1 0 -'14
Output after 11 (mW) 6 8C/
N ratio (dB) 54 45B E R
l 0-51 0 -2 As is clear from the results shown in Table 2, the substrate, I'i! The complete IJJ information recording medium (Example 2) consisting of a combination of hydrogenated polyethylene 9F Sn alloy and GeS has a high C/N with low recording power.
ratio was obtained, and the recording sensitivity was lagging behind. Additionally, the BER value was extremely small, reducing reading errors. Also, 60℃,
The BER value did not change at all even after being left for 14 days at a humidity of 90% RH, and the durability was particularly excellent.

On the other hand, the information recording medium for comparison (Comparative Example 2) had a low C/N ratio and an increased BER value, particularly over time, and was poor in durability.

[Example 3] A chlorinated polyethylene layer was provided on the same substrate as that used in Example 2 by performing the same operation as in Example 2.

InSn alloy, Au and GeS were co-evaporated onto this chlorinated polyethylene layer to form an In5Sn alloy. The proportions of Au and GeS are 65%, 5% and 3% by weight, respectively.
A recording layer having a thickness of 1000X was formed.

At this time, the addition fAJ1lot! flowing to the Au evaporation source! : By controlling the flow, the C degree of Au is high on the chlorinated polyethylene layer side,
It was made to become lower as it approaches the surface of the recording layer. The Aue degree on the surface of the formed recording layer on the chlorinated polyethylene layer side was 40%.

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

[Comparative Example 3] By performing the same operation as in Example 3, the substrate [ii! Next, Au was vaporized on the chlorinated polyethylene layer to form an Au layer. next. In and GeS were co-evaporated onto this Au layer to form a mixed layer of In and GeS, forming a two-layer stack of recording layers. At this time. Au. The :'I ratios in the In and GeS recording layers were respectively 5%, 65% and 30% in nail i+i ratio, and the layer thickness of the recording layer was 100OX.

In this way, an information recording medium consisting of 1 (plate, chlorinated polyethylene layer, and recording layer) was manufactured in this order.

[Evaluation of information recording media] By conducting the aforementioned sensitivity test and reading error test on each of the information recording media. It was rated 2+. In the reading error test, the BER was measured on a recording medium recorded with an output of 5 mW.

The obtained results are summarized in Table 3.

Table 3 Example 3 Comparative example 3 Output during manufacturing (mW) 5' 5C/N1t
(dB) 55 55B E R
l O −' l O −”1 4 I
+ Rear output (mW) 5 7C/
N1t (dB) 54 50B E R
l O ” 1 0 -2 As is clear from the results shown in Table 3, No. 1 (the plate, chlorinated polyethylene layer and recording layer are In-Sn alloy, A
An uninvented information recording medium (Example 3) consisting of a combination of u and GeS was able to obtain a high C/N ratio with low recording power, and had good recording sensitivity. Additionally, the BEH I/I was extremely small, reducing reading errors. Also, 60℃, humidity 9
The BER value did not change at all even after being left for 14 to 11 hours under the condition of 0% RH, and the durability was particularly excellent.

On the other hand, an information recording medium for comparison (Comparative Example 3
) had a particularly low C/N ratio and an increased HER value over time, and was inferior in durability compared to the information recording medium of a completely finished IJ.

Claims (1)

[Claims] 1. Information is written on the board using a laser and/or
Or readable In and GeS_x (where x
is a number in the range of 0<x≦2), the recording layer further includes P
An information recording medium comprising at least one metal selected from the group consisting of B, Sn, Zn, Bi and S. 2. 2. The information recording medium according to claim 1, wherein the metal is contained in the recording layer in the form of an alloy with In. 3. The ratio of the above metals and In is 1:300 to 1 by weight
Claim 1 characterized in that it falls within the scope of :2.
Information recording medium described in section. 4. The weight ratio of the above metals and In is 1:80 to 1:
4. The information recording medium according to claim 3, characterized in that the information recording medium falls within the range of item 4. 5. 2. The information recording medium according to claim 1, wherein the metal is Sn. 6. 2. The information recording medium according to claim 1, wherein the recording layer further contains Au. 7. The information recording medium according to claim 6, wherein the concentration of the Au on the substrate side is higher than the concentration on the recording layer surface side. 8. Claim 1, characterized in that a chlorinated polyolefin layer is provided between the substrate and the recording layer.
Information recording medium described in section.