JPH01307941A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a sufficient protective characteristic to a magnetic layer by specifying the compsn. of the protective films for coating one or both faces of the recording layer. CONSTITUTION:The protective film 2 in common use as an enhancement film, the recording layer 3 and the protective film 4 are successively formed on a substrate 1 consisting of glass or resin which has high transparency to laser light, small double refraction and good optical characteristics. The material to be used for the substrate 1 is exemplified by alumino silicic acid and resins such as epoxy. RE-TM formed by combining at least >=1 kinds of rare earths (RE) such as Tb and at least >=1 kinds of transition metals (TM)Fe and Co is used for the recording layer 3. The compd. expressed by (SixB1-x)yN1-y (where, 0.4<X<0.9 and 0.3<Y<0.7) is used as the material to be used for the protective films 2, 4. The sufficient protective characteristics for preventing the deterioration of the magnetic characteristics of the RE-TM film are obtd. in this way.

Description

[Detailed Description of the Invention] [Technology - Field] The present invention relates to a magneto-optical recording medium that is replaceable with F.
In particular, it has excellent protection against recording nozzles and improves recording and playback characteristics.
This invention relates to a second magneto-optical recording medium.

[Prior art]

Magneto-optical recording media utilize perpendicular magnetic recording and magneto-optical effects (Kerr effect, etc.), and like conventional optical recording media, they use laser light to record and reproduce information, so they have a large recording capacity. Can be overwritten. Furthermore, recording can be performed without contact between the head and the medium, and it is not affected by dust, so it has excellent stability. This magneto-optical recording medium is currently being actively researched, and is expected to be used for document information files, video/still image files, computer memory, etc., or as a replacement for floppy disks and hard disks, and is expected to be commercialized in the near future. We have reached the point where we can welcome them.

The essential characteristics required of a magneto-optical coupling body include the following:

■High recording sensitivity with laser light.

■High playback C/N.

■Good memory stability.

The recording sensitivity (2) is related to the Curie temperature Tc, and the lower the Curie temperature Tc, the better.The reproduction C/N (2) is related to the magneto-optical characteristics, and the larger the Kerr rotation angle Ok, the better. ■Memory stability is related to coercive force He.

The larger the coercive force 11c, the better.

In view of the above needs, TbFeCo, which is a combination of transition gold D1CFe*CO> and rare earth metals (Gd, DY, Tb, Nd, etc.), is used as a magnetic film for the recording layer of a magneto-optical recording medium.

GdTbFeCo, DingbDyFeco, NdDyF
Various amorphous magnetic alloy films such as cCo (
(hereinafter referred to as RE-TM film) has been proposed. RE with
Since the -7M film is amorphous, there is no media noise due to grain boundaries, and it has the advantage that a perpendicularly magnetized film can be easily produced by sputtering or vapor deposition. However, this RE-7
In particular, the rare earth (RE) component of the M film is susceptible to oxidative corrosion, and has a major drawback in that the magnetic properties such as coercive force and perpendicular magnetic anisotropy of the film deteriorate over time. This oxidative corrosion is caused by oxygen and water remaining in the vacuum chamber during the formation of the recording layer and protective film, oxygen and water adsorbed on the surface of the substrate made of polycarbonate (PC), polymethyl methacrylate (PMMA), epoxy resin, etc. :Oxygen contained in materials such as target materials (sputtering method): Oxygen contained in materials such as target materials (sputtering method): This is caused by oxygen, water, etc. in the atmosphere, but a particularly large influence is due to the intrusion of oxygen from the substrate and the atmosphere. This oxidation corrosion is further accelerated by the temperature rise caused by laser light during recording and reproduction. Therefore, in order to prevent this oxidative corrosion, attempts have been made to cover one or both sides of the RE-7M film with a protective film.

In addition, since the RE-7M film itself does not have very large magneto-optical effects such as the Kerr effect and Faraday effect, the RI
A dielectric film that is transparent to laser light and has a large E refractive index (n) is provided on one or both sides of the E-7M film, and the apparent Kerr rotation angle (θk) or Faraday rotation angle (OF) is determined by multiple reflections of light. must be made larger. In other words, the protective film must also have the functions of the enhancer film. Conventionally, such materials include Sin,
, Sin, AQN, SiN, BN, 5ilQN,
5iAQON and the like are known.

Furthermore, if the heat conductivity of the protective film is too good, the heat spread by the laser beam will increase, which may cause problems such as an increase in the laser power required for recording (hereinafter referred to as recording power) or the inability to record small bits. Therefore, the thermal conductivity of the protective film should be as small as possible.

However, the protective film made of any of the conventional materials
There has been no material that simultaneously satisfies the requirements of preventing oxidative corrosion of the RE-7M film forming the recording layer, excellent enhancement of the magneto-optic effect, and low thermal conductivity.

〔the purpose〕

In view of the problems of the prior art as described above, the present invention provides a magneto-optical recording device that has sufficient protective properties for a magnetic layer, fully functions as an enhancement film, has low thermal conductivity, and has improved recording sensitivity. The purpose is to provide a medium.

〔composition〕

In order to achieve the above object, according to the first aspect of the present invention,
A magneto-optical recording medium comprising a substrate, a recording layer made of an amorphous magnetic alloy film formed on the substrate, and a protective film covering one or both sides of the recording layer, wherein the protective film is (S lx B 1-X)Y N 1-Y(
In the formula, 0.4<X(0,9 and 0.3<Y<0.7te,
A magneto-optical recording medium is provided which is characterized by having a composition expressed by lF+L).

Further, according to the second aspect of the present invention, the recording layer includes a substrate, a recording layer formed on the substrate and made of an amorphous magnetic alloy film, and a protective film covering one or both sides of the recording Jfl. In the magneto-optical recording medium configured, the protective film is made of Si.
, l, B, 0, and N, including Si, B, and N. A magneto-optical recording medium is provided.

FIG. 1 shows a schematic cross-sectional view of a configuration example of a magneto-optical recording medium according to the present invention. This magneto-optical recording medium has a substrate (with guide grooves) 1 made of glass or resin that is highly transparent to laser light and has low birefringence and good optical properties, and a protective film 2 that also serves as an enhancement film. The recording layer 3 and the protective film 4 are formed in this order. Note that the protective film 2 may be omitted depending on the case.

Materials used for the substrate 1 include aluminosilicate, barium borosilicate, glass such as quartz, polycarbonate (PC), and polymethyl methacrylate (PMMA).
, epoxy and other resins.

The recording layer 3 contains at least one rare earth metal (RE) such as Tb, Gd, Dy, and Nd, and a transition metal (TM).
) Fe, C.

RE-TM is used in combination with at least one or more of the following. Specifically, TbFeCo, GdTbFeCo,
NdDyFaCo.

TbDyFeCo etc. are used. The recording layer 3 is formed to a thickness of 600 to 1200 layers using DC magnetron sputtering or the like. - In the case of the first invention, the material used for the protective film 2.4 is (
SiXBl-X)YNl-Y [wherein, 0.4<X<0.
9 and 0.3 (Y<0.7) are used.In the case of the second invention, Si, AQ,
[A compound composed of at least three elements including Si, B, and N among 3,0 and N is used.

Specific examples are 5iBN, 5iBON, 5iA
Examples include QBN, 5iAQBON, etc.

The protective films 2 and 4 can be formed by vapor deposition or sputtering, and among these, RF magnetron sputtering is most suitable. The thickness of the protective films 2 and 4 is set to 600 to 1200, but since the protective film 2 also serves as an enhancement film, it is adjusted according to its refractive index so that the apparent magneto-optic effect is as large as possible due to multiple reflections. set the film thickness. Furthermore, although the protective films 2 and 4 are basically made of the same material, different materials may be used in consideration of their respective functions.

〔effect〕

According to the present invention, since the protective film is constructed using a compound having the above-mentioned composition, sufficient protective properties can be obtained to prevent deterioration of the magnetic properties of the RE-7M film, resulting in high reliability and long service life. A recording medium can be realized, and since it is transparent to laser light and has a high refractive index, the reproduction C can be increased, and the function as an enhancement film can be sufficiently achieved. Furthermore, since the thermal conductivity of the compound used for the protective film is lower than that of conventional materials, it is possible to record down to bits as small as one tone, and the recording power can be reduced, resulting in improved recording sensitivity.

〔Example〕

The present invention will be further explained below with reference to Examples, but the present invention is not limited to these Examples.

First, an embodiment of the first invention will be described.

Polycarbonate board (no guide groove, diameter approx. 130am)
, 1.2 mm thick) by RF magnetron sputtering under the following film formation conditions.
2SNll os.

5i0-xsDo T25NO-s * Sin xs
An OS film was formed as a protective film to a film thickness of 100 mm. The composition was adjusted by changing the mixing amount of the target material 5L3N and BN.

・Back pressure: 1. OX], 0-' (Torr) or less ・Introduced gas 2N2 (10%) + Ar ・Introduced gas pressure: 1. OX 1O-2 (Torr) - Target material: Si, N4 and BN powder mixed and sintered - Discharge type Crab 2.5 (Sld) Next, as oxidation corrosion progresses on the protective film, Tb-rich TbFeCo (composition: Tb2
Jes.

Co, l) film was formed as a recording layer to a thickness of 800 nm by DC magnetron sputtering. Furthermore, a protective film similar to the above protective film (same material, same film thickness) is placed on the recording layer.
A recording medium was obtained.

Further, as a comparative example, a recording medium was obtained in the same manner as in the above example except that a SiO□ film and a SiN film were provided instead of the 5iBN film.

SLo ezsBa-zsNo m11. as a protective film.
315 *l5BO*2SN+1eG, SIO*5B@
-15NQ*3s, Sin, , The recording media provided with the SiN film are disks Nα, 1, Nα, 2, Nα, 3, respectively.
In order to confirm the protective effect of the protective film of these recording media, an environmental test was conducted at a temperature of 85° C. and a humidity of 85%, and changes over time in the coercive force He of the recording layer were investigated. The results are shown in Figure 2. In Figure 2, the horizontal axis is the time during which the environmental test was conducted, and the vertical axis is the coercive force) (li representing the change in c).
e/Hco (llco is the initial value of He).

Figure 2 shows that when using the conventional protective film (disk Nα
4. In reference 5), the coercive force Hc of the recording layer became large due to the environmental test, especially when the disk Nα using 5in2
In the case of No. 4, the characteristics deteriorated more than twice in 1000 hours, but when the protective film of the present invention was used (disk Nα1
-Nα3), the change in coercive force He is small.

It can be seen that the protective effect is greater than that of the conventional one.

Next, a film was formed on a polycarbonate substrate (about 130 mm in diameter, 1 and 2+ am thick) with guide grooves formed thereon by RF magnetron sputtering under the same conditions as above.
a-2SnO*1sNo +s + Sxa *1SB
O”+25Nll TG + Sla *sBa +l
A 5N6e3S film was formed as a protective film to a thickness of 700 mm.

The composition was adjusted by mixing the target materials Si, N4, and BN. And on the protective film Tb21Fe, x
A COs film was formed as a recording layer to a thickness of 800 mm by DC magnetron sputtering, and a protective film similar to the above protective film (same material, same thickness) was further formed thereon to obtain a recording medium. SNO+25BOa2SN as a protective film
Omm, 510-11BO”2SNO0Gs 5ia-
The recording media provided with the slllo*tsNa*as film were named disks Nα6, Nα7, and Nα8, respectively.

As a comparative example, the above embodiment (disks Nα6 to Nα8)
, a 5in2 film (thickness 1
Recording media were obtained in the same manner except that a SiN film (thickness: 700 mm) and a SiN film (thickness: 700 mm) were provided, and the discs were designated as Nα9 and Na1O. The thickness of the protective film of each recording medium was set in consideration of the enhancement effect caused by multiple reflections.

Recording media produced as described above (disc Na6~
The reproduction C/N and recording sensitivity (recording power) of Ni110) were measured under the following conditions.

- Recording and reproduction conditions Recording frequency 1 (Mllz) Laser wavelength 780 (stop) Disk rotation speed 900 (rpm) Reproduction laser power 1 (ml/) Applied magnetic field 500 (Oe) The measurement results are shown in Table 1.

From Table 1, the recording medium of the present invention (disc Nα6-Nα
8) has the characteristics of a high refractive index and low thermal conductivity compared to conventional media (discs Nα9 and Nα10), so it can be seen that the reproduction C/N is high and the recording sensitivity is improved. .

Next, an embodiment of the second invention will be described.

Aluminosilicate glass substrate (no guide groove, diameter approx. 130m)
5iBN and 5iAQ were deposited on 5iBN and 5iAQ, respectively, using the RF magnetron sputtering method under the following film formation conditions.
A [3N, Si[lON, 5LAI2DON] film was formed to a thickness of 1000 nm as a protective film.

Table 2 Next, when oxidation corrosion progresses on the protective film, the coercive force t! Tb-rich TbFeCo (composition: T
b25 Fee? Co, ) film as DJeJ and D
The film was formed to a thickness of 700 mm by C magnetron sputtering. Furthermore, a protective film similar to the above protective film (same material, same film thickness) was formed on the recording layer to obtain a recording medium.

Further, as a comparative example, a recording medium was obtained in the same manner as in the above example except that a 5in2 film and a SiN film were provided as the protective film.

5iBN, 5iAflBN, 5iBO as a protective film
N, 5iAQBON, 5in2, and recording media provided with SiN films were used as nine disks, Na and I1, respectively. Nci
, 12, Isao, 13, Na14, Nci15, N(1
No. 16, and in order to confirm the protective effect of the protective film of these recording media, an environmental test was conducted at a temperature of 85° C. and a humidity of 85%, and the change over time of the coercive force He of the @ layer was investigated. The results are shown in Figure 3. In Figure 6, the horizontal axis is the time during which the environmental test was conducted, and the vertical axis is He/Hco (Hco), which represents the change in coercive force He.
co is the initial value of llc).

From Figure 3, it is clear that when the conventional protective film is used (disc Nn
15. Nα16) is the coercive force H of the recording layer determined by an environmental test.
e becomes large, especially in the case of the disk Nα15 using 5in2, it more than doubles in 1000 hours, and the characteristic deterioration is significant. However, when the protective film of the present invention is used (disc NαII-N (11,4) In all cases, the change in coercive force Hc is small, and it can be seen that the protective effect is greater than that of the conventional one.

Next, on a polycarbonate substrate (about 130 mm in diameter, 1 and 2 mm in thickness) on which guide grooves were formed, 5i1 and 50% were each deposited by RF magnetron sputtering under the same film formation conditions as above.
3N film (12,700 film), 5iAI2BN film (film thickness g
oo people), 5iBON11mo (film thickness 700 people), 5il
A BON film (thickness: 800 mm) was formed as a protective film. Then record Tb24FeG, CO8 film on the protective film) ej
A recording medium was obtained by forming a film with a thickness of 800 mm by DC magnetron sputtering, and further forming a protective film similar to the above protective film (same material, same thickness). As a protective film, 5iBN, 5iltBN, 5iBON,
The recording media provided with the SiAρ80~film were respectively 9 disks N(117, Na18, N(119, Na2O).

As a comparative example, the above embodiments (disks Nα17 to Nα2
0), a SiO□ film (film thickness 1000 mm) was used as a protective film.
Recording media were obtained in the same manner except that a SiN film (thickness: 700 mm) was provided, and disks Nα21 and Nα22 were obtained. Note that the thickness of the protective film of each recording medium was set in consideration of the enhancement effect due to multiple reflections.

Recording medium produced as above (disc & 17~
Nα22) Under the following conditions, playback C, recording sensitivity (
recording power) was measured.

・Recording and reproducing conditions Recording frequency: 1 (Z) Laser wavelength: 780 (nm) Disk rotation speed: 900 (rpm) Reproducing laser power: 1 (m) Applied magnetic field: 500 (Os) The measurement results are shown in Table 3. show.

From Table 3, 1 recording medium of the present invention (disks Nα17 to N
α20) is a conventional medium (disk NCL21.Nα2
It can be seen that the reproduction C/N is high and the recording sensitivity is improved because it has both characteristics of a high refractive index and a low thermal conductivity compared to 2).

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the cross-sectional structure of a magneto-optical recording medium according to the present invention, FIG. 2 is a diagram showing the results of environmental tests of an example of the first invention and a comparative example, and FIG. 3 is a diagram showing the implementation of the second invention. It is a figure which shows the result of the environmental test of an example and a comparative example. 1...Substrate 2...Protective film (also enhancement film) 3...Recording layer 4...Protective layer Patent applicant Ricoh Co., Ltd.

Claims (2)

[Claims] (1) A magneto-optical recording medium comprising a substrate, a recording layer made of an amorphous magnetic alloy film formed on the substrate, and a protective film covering one or both sides of the recording layer, A light characterized in that the protective film has a composition represented by (Si_XB_1_-_X)_YN_1_-_Y (wherein 0.4<X<0.9 and 0.3<Y<0.7) magnetic recording medium. (2) A magneto-optical recording medium comprising a substrate, a recording layer made of an amorphous magnetic alloy film formed on the substrate, and a protective film covering one or both sides of the recording layer, The protective film is Si of Si, Al, B, O, and N.
, B, and N.