JPH03235231A - Information recording medium - Google Patents

Abstract

PURPOSE:To obtain an information recording medium having good recording/ reproducing characteristics and stability and is suitable for high-density recording by forming an auxiliary recording layer essentially comprising a compd. of calcogens and metal elements adjacent to at least one interface of a recording film to the substrate side. CONSTITUTION:The information recording medium has a substrate 1 and a recording film 5 in which pits or holes are formed by irradiation of an energy beam for recording. The interface of the recording film 5 to the substrate 1 side is covered with an auxiliary recording layer 4 essentially comprising a compd. of calcogens and metal. If the medium has a base film 3, the film 4 is provided between the base film 3 and the recording film 5, and further the layer 4 may be formed on the opposite interface of the recording film 5 to the substrate 1. Thereby, the rim of a pit formed by irradiation of an energy beam for recording has a smaller diameter, which means that the influence from adjacent recording pits is suppressed low and that the obtd. medium is suitable for high density recording.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention is applicable to signals obtained by FM modulating analog signals such as video and audio, computer data, facsimile signals, digital audio signals, etc. using a recording energy beam such as a laser beam or an electron beam. The present invention relates to an information recording medium that can record digital information in real time.

[Conventional technology]

An information recording medium in which recording is performed by irradiating a recording film with a recording energy beam such as a laser beam to form recesses or holes in the recording film includes a substrate, a base film, and a recording film. Substrates include glass discs or plastic discs made of acrylic resin, etc., with UV-curable resin layers provided with guide grooves for tracking, and plastic discs made of polycarbonate, acrylic resin, polyolefin, etc., with guide grooves formed by injection molding. A board etc. is used. For the base film, a solvent-soluble resin such as nitrocellulose, acetylcellulose, or copper phthalocyanine, or a sputterable resin such as a fluororesin is used. For example, a thin film containing Te as a main component is used as the recording film. Conventionally, in order to improve the stability of the recording film of such information recording media, Sb, Si, and G were added to at least one interface of the recording film.
JP-A-58-224446 describes the provision of a thin film mainly composed of elements such as e and Sn as a recording auxiliary layer. Regarding the recording film composition, please refer to Japanese Patent Application Laid-Open No. 57-3818.
9 and Japanese Unexamined Patent Publication No. 57-66996. Further, the base film is described in JP-A-57-55544.

[Problems to be Solved by the Invention] However, the information recording medium shown in the above-mentioned prior art has problems with the temperature distribution of the laser beam irradiated part, the viscosity of the melted recording film, and the wettability of the melted recording film and the base film. No consideration was given to this. That is, since the temperature distribution of the laser beam irradiation part is wide, the diameter of the formed recording pit (rim outer diameter) is large. Since the viscosity of the molten recording film is low and the wettability between the molten recording film and the base film is low, the rim formed around the open hole has a small rim width and a large rim inner diameter. Ta. Since the reproduced signal from the recording hole depends on the rim inner diameter of the hole, even if the rim outer diameter is the same, a smaller rim inner diameter is more suitable for higher density. Therefore, the laser beam wavelength is 830 nm, and the numerical aperture (NA) of the objective lens is 830 nm.
) When performing high-density recording with a pit spacing of 1.4 μm on an information recording medium manufactured with a conventional media configuration using a 0.53 optical head, the recording laser beam can secure a sufficiently large reproduced signal as an electrical signal. The problem was that the power range (power margin) was small, making it unsuitable for high-density recording. An object of the present invention is to provide an information recording medium that has good recording and reproduction characteristics, good stability, and is suitable for high-density recording. [Means for Solving the Problems] The above object is to (1) provide an information recording medium having at least a recording film on which a recess or a hole is formed by irradiation with a recording energy beam on a substrate; An information recording medium characterized in that a recording auxiliary layer containing a compound of a chalcogen element and a metal element as a main component is provided adjacent to at least the interface of the film on the substrate side; (2) the substrate side of the recording film; The information recording medium according to item 1 above, characterized in that a recording auxiliary layer is further provided adjacent to the opposite interface, (3) the melting point of the recording auxiliary layer is higher than the melting point of the recording film. (4) The information recording medium as described in 1.2 or 3 above, wherein the compound constituting the recording auxiliary layer contains a Se compound as a main component; (5) The above Se compound has +sb, Sn, In, Bi,
4. The information recording medium according to 4 above, which is a compound of Ga, Ge, Pb or Zn and Se. (6) The information recording medium according to 1.2 or 3 above, characterized in that the compound constituting the recording auxiliary layer contains an S compound as a main component; (7) the S compound comprises Sb, Sn, In, Bj, Ga
, Ge, Pb, or a compound of Zn and S, (8) the information recording medium according to any one of 1 to 7 above, characterized in that the recording film contains at least Ta. This is achieved using an information recording medium. In the information recording medium of the present invention, adjacent to at least the substrate side interface of the recording film, so that the rim inner diameter of the hole formed by irradiation with the recording energy beam is small,
A recording auxiliary layer containing a compound of a chalcogen element and a metal element as a main component is provided. When the information recording medium has a base film, the recording auxiliary layer is provided between the base film and the recording film. The recording auxiliary layer. It may be further provided adjacent to the interface opposite to the substrate side of the recording film. The respective recording auxiliary layers may be composed mainly of the same compound or may be composed mainly of different compounds. In addition, the thickness of the recording auxiliary layer is 1 nm, since the inner diameter of the rim of the formed hole is small and the power margin is large.
The thickness is preferably 200 nm or more. It is more preferably 2 nm or more and 1100 nm or less, and most preferably 4 nm or more and 50 nm or less. The melting point of the recording auxiliary layer is preferably higher than that of the recording film. When a Te-based recording film is used, the melting point of the recording film is lower than 450'C, which is the melting point of Te. Therefore, the melting point of the recording auxiliary layer is preferably 450'C or higher, which is the melting point of Te, and more preferably 500''C or higher.The components of the recording auxiliary layer include: It is preferable to use a Se compound as the main component.In addition, in terms of the low absorption rate of recording light in the recording auxiliary layer, Se
It is preferable that the main component is a compound or an S compound. Among Se compounds, compounds of Se and sb (S b2
S e3), a compound of S e and Sn (S n S e
, 5nSe2), a compound of Se and In (I n4Se,
, ■ nSe , I n, S e 7 ,
I n, S e, , I n 2 S
e 3) Compound of Se and B1 (B i S e,
B i2S e, ), a compound of Se and Ga (GaSe
, Ga2Se3). Compound of Se and Ge (GeSe-Ge2Se,), Se
A compound of and pb (PbSe) and a compound of Se and Zn (
ZnSe) has a melting point of 450', which is the melting point of Te.
Since it is C or more, it is preferable in that the recording density becomes high. Among S compounds, compounds of S and sb (sb2s,)
, a compound of s and Sn (SnS, 5n2S1.5nS2
), compound of S and In (InSe. In, S,, In, B4.I n2S,), S and Bi
compound (B j2s3), compound of S and Ga (Ga
, S, GaS, Ga, S, ), compound of S and Ge (G
e S, Ge2S, ), a compound of S and pb (pbs), and a compound of S and Zn (ZnS) all have melting points of 450° C. or higher, which is the melting point of Te, and are therefore preferable in terms of increasing recording density. . In addition, among the above Se and S compound systems, Se and Sn,
Se and In, Se and Bj, Se and Ga, Se and Ge,
The binary phases of S, 5n-5 and In, S and Ga, and S and Ge contain two or more types of compounds. Good results can also be obtained using a mixture of two or more of these compounds. In addition to the above-mentioned compound, the recording auxiliary layer may contain a mixture of constituent elements of the compound, other chalcogen elements, and metal elements. It is preferable that these elements are added in an amount of 1.0 at% or less. It is more preferable to add 5 at% or less. In particular, by adding Se, the oxidation resistance of the recording auxiliary layer can be improved without substantially affecting the recording characteristics. As for the recording film composition, if inorganic substances are the main component, Te-based, S
Good characteristics can be obtained with e-type or other metal-based materials. In particular, Te-3e type, Te-C type, etc. containing Te are preferable. The thickness of the recording film is preferably in the range of 10 to 50 nm. The information recording medium of the present invention can be in the form of a disk, tape, card, or the like.

[Effect]

When the information recording medium of the present invention is used, when the melting point of the substance forming the recording auxiliary layer is higher than the melting point of the recording film, the recording auxiliary layer does not melt when the recording film melts, so that the recording auxiliary layer does not melt when the recording film is melted. Due to the high wettability of the layer, the rim width of the formed rim increases. When the recording auxiliary layer is also melted and holes are formed, the rim inner diameter is sufficiently small. Therefore, it is possible to suppress the influence from the recorded pits immediately adjacent to the recorded pits in the front, rear, right and left directions. On the other hand, since the reproduction signal from the recording hole depends on the inner diameter of the rim of the hole,
Even if the rim outer diameter is the same, a smaller rim inner diameter is more suitable for higher density. Therefore, using an optical head with a laser beam wavelength of 830 nm and an objective lens having a numerical aperture (NA) of 0.53, a pit interval of 1.4 μm was formed on an information recording medium manufactured with a medium configuration having a recording auxiliary layer of the present invention. When high-density recording is performed, the power range (power margin) of the recording laser beam is large enough to ensure a sufficiently large reproduction signal as an electrical signal. Therefore, an information recording medium manufactured with a medium configuration having a recording auxiliary layer according to the present invention is suitable for high-density recording.

【Example】

Hereinafter, the present invention will be explained in detail by way of examples. Example 1 An explanation will be given with reference to FIG. 1(a), which shows a schematic cross-sectional view of a manufactured disk. A disk-shaped chemically strengthened glass plate with a diameter of 300 mm and a thickness of 1.2 mm was used as the substrate 1. Ni in advance
A 1.5% n-butyl acetate solution of nitrocellulose to serve as a base film was spin-coated onto a stamper (not shown) and dried. An ultraviolet curable resin is dropped onto this -H, the substrate 1 is pressed onto this, the resin is cured by ultraviolet irradiation, and a base film is formed which has guide grooves for tracking at a pitch of 1.6 μm and pre-pits indicating addresses on the surface. 3 and an ultraviolet curing resin layer 2 were formed, the Ni stamper was removed, and a replica substrate was produced. Next, a recording auxiliary layer 4 having a composition of 5b2Se (melting point: 590° C.) is formed on the replica substrate to a thickness of 10 nm by current heating vapor deposition, and Pb is deposited thereon. Recording film 5 with a composition of Tel1aSe15 (melting point 430°C)
was formed to a thickness of 30 nm by an electric heating vapor deposition method to produce a disk A. On the other hand, as shown in FIG. 1(a), recording aids of the composition of 5b2Se, fg4, Pb
,Te,. 10 each of the recording films 5 having a composition of Seis.
In addition to depositing S b to a thickness of 30 nm and 30 nm,
A recording auxiliary layer 4 having a composition of S e was deposited to a thickness of 10 nm to prepare a disc B. For comparison, there is no auxiliary layer, pb, Te,. A disk C having the same structure as the conventional one was manufactured in which only the recording film 5 having a composition of Se was deposited to a thickness of 30 nm. A schematic cross-sectional view of the disk C is shown in FIG. The recording and reproducing characteristics of the discs A, B, and C were measured as follows. The disk is rotated at 90 rpm and a semiconductor laser beam with a wavelength of 830 nm is applied to the numerical aperture (NA).
) A 0.53 lens focused the light and recorded it on the flat area between the tracking guide groove (group) and the group. The readout light was a continuous light of 1 mW so as not to cause deformation of the recording film. Recording was performed at a position with a radius of 140 mm (outer periphery), and the recording density was increased to a recording pit interval of 1.4 μm.
A 9.4 MHz signal was recorded so that the frequency was 9.4 MHz. Here, the recording pulse width was set to 42 ns. FIG. 2 shows the dependence of the reproduction signal modulation degree on the recording power for discs A, B, and C when recording was performed at different recording powers. here,
The reproduction signal modulation degree is defined by the following equation. (Reproduction signal modulation degree) = (Reproduction signal amplitude strength at recording point) / (Reproduction signal amplitude strength at pre-pit) Power margin when slice level is set to 0.4 (recording where reproduction signal modulation degree is 0.4 or more) Power range) is 5.2 mW between 8.4 and 13.6 for disk A, 3.7 mW between 8.3 and 1.2.0 mW for disk B,
For disk C, between 8.2 and 10.6 mW, 2.4 m
It is W. Therefore, in the discs A and B of the present invention, the power margin during high-density recording was significantly expanded compared to the disc C of the conventional structure. Regarding the configuration of the disk, disk A is more preferable than disk B. Further, FIG. 3 shows a cross-sectional view of recording pits (recording holes) formed during recording here. The power dependence of the rim inner diameter and outer diameter in this cross section is shown in FIG. 4 for each of disks A, B, and C. The rim outer diameter shows the same recording power dependence regardless of disks A, B, and C, but disk C has the smallest rim inner diameter, followed by disk B, and disk A has the largest rim inner diameter. In disk A, when the film thickness of the Sb2Se3 auxiliary layer is changed and the slice level is set to 0.4 during high-density recording similar to the above measurement, the power margin (recording where the reproduction signal modulation degree is 0.4 or more) The film thickness dependence of
As shown in the figure. Table 1 shows the results when Pb5e and Zn5e, which are binary compounds containing Se, were used instead of 5b2Se as the recording auxiliary layer in the above example. Further, as the recording auxiliary layer in the above embodiment, S b2
B, which is a binary compound containing S, instead of Se.
Table 2 shows the results using i2S, pbs and ZnS. Table 1 (blank below) Table 2 When 5% Se was added to the recording auxiliary layer in each of the above examples, the power margin of the information recording medium was slightly lower than in each example, but the environmental resistance was improved. The lifespan at 80°C and 90% relative humidity is more than twice as long. Note that similar results were obtained when a plastic substrate such as polycarbonate, PMMA, or polyolefin was used as the substrate material instead of the glass substrate used in the above example. Similar results were obtained using acetylcellulose, phthalocyanine dye, guanine, fluororesin, polyamide, polyimide, etc. as the base film, in addition to nitrocellulose. Similar results can be obtained by using other chalcogenide recording films such as Te-C, Te-5b, and Te-0 instead of the P b -T e -S s recording film. Ta. Example 2 Next, unlike the system used for the recording auxiliary layer in Example 1, a disk in which a binary compound containing Se or S having two or more types of compounds was used as the recording auxiliary layer was prepared.
The recording characteristics were measured under exactly the same conditions as in Example 1. The power margin when the slice level is set to 0.4 on a disk with the structure of disk A using 5nSe and 5nSe2, which are 5n-Se compounds, in the recording auxiliary layer (reproduction signal modulation degree is 0.4 FIG. 6 shows the results of measuring the film thickness dependence of the recording auxiliary layer in the above recording power range. In the above example, the thickness of the recording auxiliary layer was 10 nm, and the recording auxiliary layer contained 5nSe and 5nSe. FIG. 7 shows the results of the power margin when the constituent elements Se and Sn were mixed in various ratios. The horizontal axis of the figure is the concentration of Se in the total composition. When the composition ratio of Se is 45 to 72 at.%, the power margin is 4 mW or more, and in particular, the power margin is 5 mW or more at compositions near 5 nSe and 5 nSe2 or between these two types of compounds. As the recording auxiliary layer in the above embodiment, instead of the 5n-8e system, In-5e system, which is also a binary system containing Se and having two or more types of compounds, B i -S s system, G
Table 3 shows the results using a-3e and Ge-3e compounds and mixtures thereof. Also two or more compounds and mixtures thereof. The power margin is 5 mW or more. Further, as the recording auxiliary layer in the above embodiment, 5n-3
Instead of e-type, S which also has two or more types of compounds
The 5n-3 system is a binary system containing. Table 4 shows the results using In-5, Ga-8, and Ge-3 compounds and mixtures thereof, as well as 5bs-s compounds.3 These compounds and mixtures also have a power margin of It is 5 mW or more. (Left below) 3rd coat 4th machine 5% Se in the recording auxiliary layer in each of the above examples
When added, the power margin of the information recording medium was slightly lower than in each example, but the environmental resistance was improved and
The lifespan at 90% relative humidity is more than twice as long. Similar results were obtained when a plastic substrate such as polycarbonate, PMMA, or polyolefin was used as the substrate material instead of the glass substrate used in the above example. Similar results were obtained using acetylcellulose, phthalocyanine dye, guanine, fluororesin, polyamide, polyimide, etc. as the base film, in addition to nitrocellulose. As a recording film, instead of the above Pb-Te-5e system, T
Similar results were obtained using other chalcogenide recording films such as e-C, Te-5b, and Te-0.

【Effect of the invention】

As explained above, if the information recording medium according to the present invention is used, the rim inner diameter of the recorded hole is small, so even when high-density recording is performed, a good reproduction signal can be obtained, crosstalk is small, and the recording power is It also has the effect of having a large margin.

[Brief explanation of drawings]

FIG. 1(a) and FIG. 1(b) are schematic cross-sectional views showing the structure of an information recording medium according to an embodiment of the present invention, and FIG. 2 is a dependence of the reproduction signal modulation degree on recording power in the embodiment of the present invention. Fig. 3 is a sectional view of recording pits 1 to (recording holes), Fig. 4 shows the
The figure shows the dependence of the recording power on the inner and outer diameters of the rim in the information recording medium of the present invention, and FIG. 5 shows the dependence on the film thickness of the 5b2Se and recording auxiliary layer in the disc A of the embodiment of the present invention. , FIG. 6 is a diagram showing the dependence of 5nSe and S n Se on disk A according to an embodiment of the present invention, and the film thickness of the recording auxiliary layer, and FIG. FIG. 8, which is a diagram showing the composition dependence of the Se-based recording auxiliary layer, is a schematic cross-sectional view showing the structure of a conventional information recording medium. 1... Substrate 2... Ultraviolet curing resin layer 3.
... Base film 4 ... Recording auxiliary layer 5 ... Recording film 7 ... Outer diameter 6 ... Rim 8 ... Inner diameter

Claims (1)

[Claims] 1. In an information recording medium having at least a recording film on a substrate in which a concave portion or a hole is formed by being irradiated with a recording energy beam, an information recording medium adjacent to at least the interface of the recording film on the substrate side. An information recording medium comprising: a recording auxiliary layer containing a compound of a chalcogen element and a metal element as a main component. 2. The information recording medium according to claim 1, further comprising a recording auxiliary layer adjacent to an interface opposite to the substrate side of the recording film. 3. The information recording medium according to claim 1 or 2, wherein the melting point of the recording auxiliary layer is higher than the melting point of the recording film. 4. The information recording medium according to claim 1, 2 or 3, wherein the compound constituting the recording auxiliary layer contains a Se compound as a main component. 5. The above Se compound is Sb, Sn, In, Bi, Ga
, Ge, Pb, or a compound of Zn and Be.
The information recording medium described in . 6. The information recording medium according to claim 1, 2 or 3, wherein the compound constituting the recording auxiliary layer contains an S compound as a main component. 7. The above S compound is Sb, Sn, In, Bi, Ga,
The information recording medium according to claim 6, which is a compound of Ge, Pb, or Zn and S. 8. The information recording medium according to claim 1, wherein the recording film contains at least Te.