JPH02227845A - Magneto-optical recording medium - Google Patents

Abstract

PURPOSE:To obviate the degradation in the adhesive property of a substrate and a recording layer occurring in the warpage of the substrate and to lessen the deterioration in the characteristics of the recording medium by adopting the constitution in which cumulatively superposed LB (Langmuir-Blodgette) films are provided and the substrate is isolated substantially from the outdoor air. CONSTITUTION:The entire surface of the substrate 11 is coated with the cumulatively superposed LB films 31 and a protective film 13a, a magnetic film 15 and a protective film 13b are successively deposited on the coated substrate 1 to form the recording layer 17. The constitution in which at least the substrate 11 is substantially isolated from the outdoor air is, therefore, obtd. The degradation in the adhesive property between the substrate 11 and the recording layer 17 occurring by the warpage of the substrate 11 is obviated and the deterioration in the characteristics of the recording medium 33 is lessened.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a magneto-optical recording medium, and in particular,
The present invention relates to a technique for improving the adhesion between a substrate and a recording layer.

(Prior Art) Magneto-optical recording media (hereinafter sometimes simply referred to as recording media) are being actively researched and developed as high-density recording media equipped with rewritable magnetic films.

Among the magneto-optical recording materials constituting the magnetic film of such recording media, amorphous alloys of rare earth metals and transition metals (hereinafter also referred to as single RE-TM gold alloys) are highly sensitive to magnetization. It is a perpendicularly magnetized film with the direction perpendicular to the film formation surface, it has a large coercive force of several Oe, and it can be formed relatively easily by sputtering, vacuum evaporation, or other deposition techniques. It has the most progress in research and the most progress in practical application.

However, the magnetic film made of the RE-T alloy has low corrosion resistance (see, for example, "Magneto-Optical Disk" (edited by Osamu Imamura, published by Trikebus, p. 427)), and may have poor magneto-optical effects. It has the disadvantage that the (Kerr effect) is small.

Therefore, a recording layer consisting of a magnetic film made of RE-T1 alloy sandwiched between protective films made of various materials was formed on the substrate surface to prevent corrosion of the magnetic film and to utilize multiple reflections of light. A structure that increases the apparent rotation angle is known (Reference I: p. 119).

First, prior to explaining the present invention, the above-mentioned conventional magneto-optical recording medium will be explained.

FIG. 5 shows an example of the configuration of a conventional recording medium.
In Figure 0, which is an explanatory diagram showing a schematic cross section, hatching etc. representing the cross section are partially omitted.

As can be understood from FIG. 5, the surface of the substrate 11 has protective l1i13a and magnetic 1! +5 and protective film +3b!
The recording layer 17 was formed by sequentially depositing the layers, and the recording medium 19 was completed.

Among these, the substrate 11 is made of, for example, polycarbonate resin, glass, epoxy resin, or any other suitable material, and has a disk shape.

In addition, the protective mHI 3 a and +31) is, for example, 5iO
1SiO□, A'lN, 5j3N4, A'1SiN
, by depositing JQSiON or other overcoat material. As already mentioned, the application of this protective film is carried out, for example, by sputtering, vacuum evaporation or other application techniques depending on the material of which the protective film is made.

In general, the magnetic 1115 is composed of the RE-T1 alloy mentioned above, and it is possible to combine such alloys with [for example, Tb-Fe alloy, Tb-(:o alloy, Tb-Fe-Co alloy, or other rare earth metals and transition Various combinations with metals are known.

In the recording medium 19 having such a structure, the medium 19
The protective film 13a disposed on the reading side of C/N (Car
carrier No.1se ratio: carrier wave to noise ratio)
Since this is a factor that affects

■The apparent material must have a high refractive index to increase the Kerr rotation angle.■The wavelength of the light used for writing and reading (usually 750
The material must be transparent at wavelengths of up to 900 (nm) or so) ■ It must be a corrosion-resistant material that can protect the magnetic S from, for example, moisture in the environment in which the medium is used. I[Membrane +3b may be made of any other material that does not meet the conditions for enhancing the Kerr effect, as long as it satisfies the corrosion resistance shown in at least the above-mentioned (2).

In general, other structures of conventionally known recording media include:
Magnetism 1 mentioned above! A configuration in which a reflective film is added to +5 and protective HI 3 a and +3b to form a recording layer is also known.

For example, aluminum (A9), gold (A9),
A wide variety of reflective film materials have been used, including copper (Cu), titanium (Ti), and copper (Cu).

First, as a configuration including such a reflective film, the $6 figure (A
), the protective film 13a, the magnetic film 15, and the ll
1ll13b and the reflective film 21 are sequentially deposited, and the recording layer 23
A recording medium 25 having a structure formed on the surface of a substrate 11 is known.

Further, normally, the above-mentioned reflective film is provided so as to sandwich a magnetic film between it and the substrate, and as another structure including reflective III,
As shown in FIG. 6(8), the surface of the substrate 11 is coated with a protective film 13a, a magnetic film 15, a reflective film 21 and a protective film 11i131.
There is also known a recording medium 29 having a structure in which a recording layer 27 is formed on the surface of the substrate 11 by sequentially depositing layers 27 and 27 on the surface of the substrate 11.

In such conventional recording media, information is written using a thermomagnetic writing method using a laser beam narrowed to a spot diameter of about 1 (μm) and an external magnetic field, and since it is a perpendicularly magnetized film as described above, (bit/cm2) extremely high density recording is possible. Furthermore, it has the excellent feature that, in principle, erasing and rewriting can be repeated almost infinitely many times.

On the other hand, a technology for forming thin films called ultra-thin plastics is known for the purpose of imparting heat resistance to various products6.
For example, Document IT: Ir ultra-thin plastic film - Focusing on high heat-resistant polyimide and aramid - J (R Chemistry and Industry) Vol. 40, No. 6.

pp. 471-473, published in 1987), Langmuir-Prodgett (L 8 (:Lanqmuir
A thin film forming technique has been disclosed in which a monomolecular film made of a precursor of a compound such as polyimide or aramid is accumulated on the surface of a product by a method, and then this accumulated film is polymerized by a chemical reaction.

(Problems to be Solved by the Invention) As described above, in conventional magneto-optical recording media, the substrate is made of synthetic resin such as polycarbonate resin or epoxy resin, or glass, and recording is performed in various configurations on the surface of the substrate. As is well known, magneto-optical recording media tend to be constructed using synthetic resins, which have superior mechanical strength compared to glass and are inexpensive, among the substrate materials mentioned above. Yes.

However, in conventionally known magneto-optical recording media, cracks and peeling (M18) occur at the interface between the substrate made of synthetic resin and the recording layer, and the characteristics of the magneto-optical recording medium are stable over a long period of time. The problem was that it was difficult to maintain.

Such deterioration of characteristics is caused, for example, by the synthetic resin that makes up the substrate absorbing moisture in the environment in which the recording medium is used, and the resulting warping of the substrate, resulting in poor adhesion between the substrate and the recording layer. it is conceivable that. Therefore, the inventors of this application believe that if at least the moisture absorption between the substrates is prevented by using the thin film forming technology disclosed in the above-mentioned Document H, the characteristics of the magneto-optical recording medium over time can be improved. This invention was made by focusing on the fact that deterioration can be reduced.

In view of the above-mentioned conventional problems, an object of the present invention is to reduce the warpage of a substrate made of synthetic resin, and thereby provide a magneto-optical recording medium that can stably exhibit excellent characteristics over a long period of time. It lies in providing.

(Means for Solving the Problem) In order to achieve this object, according to a magneto-optical recording medium according to the first invention of this application, a magneto-optical recording medium comprising a recording layer on a substrate made of synthetic resin. In this case, the entire surface of the above-mentioned substrate is coated with Langmuir-Blodgett (L
B (Langmuir-Brodgett)) is characterized in that it is coated with a cumulative polymer film, and the above-mentioned recording layer is provided on the coated substrate.

Further, according to the magneto-optical recording medium according to the second invention of this application, in the magneto-optical recording medium comprising a recording layer on a substrate made of synthetic resin, the entire surface of the magneto-optical recording medium is covered with an LB cumulative polymer film. It is characterized by being coated with

(Function) According to the magneto-optical recording medium according to this application, by providing the LB cumulative polymer film in each of the above-mentioned configurations, at least the substrate is effectively isolated from the outside air. Therefore, it is possible to eliminate the decrease in adhesion between the substrate and the recording layer mainly caused by the warpage of the substrate, and to reduce the deterioration of the characteristics of the recording medium.

(Example) Examples of the magneto-optical recording medium according to the present invention will be described below with reference to the drawings. The embodiments described below will be explained using preferred numerical examples of the number of times of the present invention and other conditions, but these are merely illustrative and the present invention is not limited only to these specific conditions. Also, in this example, except for the provision of the LB cumulative polymer film, as an example of the structure of the recording layer constituting the recording medium, the structure shown in FIG. explain. Generally speaking, in the drawings referred to in the following description, hatchings and the like representing cross sections are partially omitted, and components having the same functions as those already described are designated with the same reference numerals.

Structure and manufacturing procedure of magneto-optical recording medium> First, with reference to FIG. 1, the structure of the recording medium will be explained according to the manufacturing procedure of the recording medium according to the embodiment of the first invention of this application. do.

FIG. 1 is an explanatory diagram showing a schematic cross section similar to FIG. 3 in order to explain the recording medium according to the first embodiment.

First, a substrate 11 made of polycarbonate resin is prepared, and the LB cumulative polymer film 31 covering the entire surface of the substrate 11 is formed using the thin film forming technique disclosed in Document H mentioned above.

In this example, a conventionally well-known M manufactured by B Membrane Formation was used, and the method disclosed in the above-mentioned document II was utilized. To explain in detail, first, a polyamide precursor made of a long-chain alkylamine salt of polyamic acid is spread on a water surface to form a monomolecular film.

Thereafter, 10 layers of monomolecular film are accumulated over the entire surface of the substrate 11 according to a conventional method.
After acetic anhydride-pyridine is applied to the cumulative film, it is dried at room temperature to obtain an LB cumulative polymer film 31 having a film thickness of about 100 (λ).

After passing through these steps, the recording layer 17 is formed using the substrate 11 coated with the LB cumulative polymer film 31 as a base by a conventionally well-known technique.

The procedure and conditions for forming this recording layer 17 will be explained below.

First, a protective film 13a made of Au5iN is deposited on the upper side of the substrate 11 in the above-described state by a sputtering method similar to the conventional method.
is deposited to a film thickness of approximately 800 (λ). The film forming conditions at this time were that the input power was 500 (W) and the argon gas pressure was 3 (mTorr).

Next, the composition ratio of terhium diiron: cobalt is 22 near 0
:8 (atomic ratio) is prepared, and under the same sputtering conditions as described above, the magnetic film 15 is formed on the surface of the protective film 13a to a thickness of about 800 (λ). Adhesive formation.

Subsequently, under the same conditions as the above-mentioned protective film 13a,
A protective film 3b with a thickness of about 1000 (λ) is deposited on the surface of the magnetic film 15 described above.

In this way, the recording layer 17 is formed by sequentially depositing the protective film 13a, the magnetic film 15 and the protective film 13t on the surface of the substrate 11 on which the B cumulative polymer film 31 is formed.
A recording medium 33 as a sample according to Example 1 shown in the figure was obtained.

Incidentally, the recording medium 3 according to Example 1 obtained in this way
When considering the recording characteristics of 3, the C/N was 46.0.
(dB), and the error rate (the rate at which information written in advance is damaged due to a predetermined change over time) was about 10-5 (all test conditions are omitted).

Adhesion test procedure and subsequent measurement results> Next, the procedure of the adhesion test performed on the recording medium 33 according to Example 1 described above and the measurement results of recording characteristics performed thereafter will be explained. .

Conventionally, various adhesion tests are known, but in this example, the adhesion test measures the deterioration of characteristics after being kept under constant temperature and humidity conditions, and the ff'Z/ff'Z/ After conducting the AD cycle test J, the characteristics of each recording medium were measured.

First, an adhesion test (hereinafter referred to as
This test is called "f-adhesion test". ) results will be explained.

In this R2 adhesion test, the recording medium 33 according to Example 1 described above is kept under environmental conditions of a temperature of 70 ("C) and a relative humidity of 85 (%) for 200 hours.

After such a test, the recording characteristics described above were measured for the recording medium 33 according to the example, and it was found that C.
No change was observed in /N or error rate. Also,
Even after such (i' adhesion test J), warping of the substrate 11 and peeling between the substrate 11 and the recording layer 17 were not observed.

For comparison, a recording medium 19 according to a comparative example ( (see FIG. 5) was prepared, and an Ir adhesion test was conducted in the same manner as described above.

As a result, in the medium 19 according to the comparative example after the above-mentioned "adhesion test", the above-mentioned warping and peeling were observed.

Next, Ii'Z/AD cycle test J's hand! @ and the results of measuring the characteristics of the recording medium sample after this test will be explained.

First, to explain the procedure of the [i'Z/AD cycle test] of this example, under two conditions: the temperature condition shown in Figure 3 (A) and the humidity condition shown in Figure 3 (B). , holding the sample according to Example 1 prepared separately, 1 (cycle)
conducted multiple 40-hour tests. Furthermore, the third
Figure (A) is an explanatory diagram showing temperature ('C) on the vertical axis and retention time (hours) on the horizontal axis, and M3 diagram (8) shows relative humidity (%) on the vertical axis and horizontal axis It is an explanatory diagram showing a retention time (hour) of 18:.

Referring to these figures, the temperature and humidity conditions for each time interval for the 1 (cycle) Ire/AD cycle test j are explained as follows: ■Holding time 0 to 2 (hours) Temperature 7I25 ('C) and maintain a relative humidity of 90 (%) ■Holding time 2 to 5 (hours) Maintain a relative humidity of 90 (%) and a relative humidity of 25 ('C) to 65
Heat up over 3 hours until ('C) ■Holding time 5-8
(hours) Maintain temperature 65 ("C) and relative humidity 90 (%) ■Holding time 8-10 (hours) Maintain relative humidity 90 (%) and 65 ("C) to 25
Temperature is lowered over 2 hours until it reaches (“C”) ■Holding time: 10~
12 (hours) Maintain relative humidity 90 (%), 1 and 25 ('C) to 6
5 ('C) over 2 hours ■ Holding time 12
~15 (hours) Maintain temperature 65 ('C) and relative humidity/Jj90 (%) ■
Holding time 15-18 (hours) Maintain relative humidity of 90 (%) and 65 (''C) to 25
Temperature decreased over 3 hours until ('C), holding time 1
8-19.5 (hours) Maintain temperature 25 ("C) and relative humidity 90 (%) ■ Hold time 19.5-20 (hours) Maintain relative humidity from 90 (%) to O (%) and temperature 2
5 ('C) to -10 (''C), falling over 0.5 hours ■ Maintain darkness 20-22 (hours) Maintain temperature -10 (''C) and relative humidity O (%) ■ Holding time 22-22.5 (hours) Relative humidity from 0 (%) to 90 (%) and temperature -
Increase from IQ ('C) to 25 ('C) over 0.5 hour cycle ■ Holding time 22.5-24 (hours) Maintain temperature 25 ('C) and relative humidity 90 (%) [phase]
Holding time 24-27 (hours) Maintain relative humidity of 90 (%) and 25 (''C) to 65
(“C”), the temperature was raised over 3 hours and the O holding time was 27~
30 (hours) Temperature 165 (''C) and relative humidity 90 (%) IF!, maintained ■ Holding time 30-32 (hours) Maintain relative humidity 90 (%) and 65 ('C) to 25
Temperature decreased over 2 hours until ('C) ■ Holding time 32 ~
34 (hours) Maintain relative humidity of 90 (%) and 25 ('C) to 65
(“C”), heat up over 2 hours ■Holding time: 34~
Holding time 37-39 (hours) Maintaining temperature 65 ('C) and relative humidity 90 (%) Holding time 37-39 (hours) Maintaining relative humidity 90 (%) and 65 ('C) to 25
Temperature decreased over 2 hours until ('C) ■ Holding time 39~
40 (hours) Temperature 25 ('C) and relative humidity 90 (%) were maintained.

In addition, in the evaluation after this f Z/AD cycle test, the sample surface was observed with the naked eye every time the above-mentioned 1 (cycle) holding operation was performed, and warpage of the substrate 11 and the substrate and recording layer were detected. The presence or absence of peeling of the gate was investigated.

As a result, in the recording medium 33 according to the first embodiment described above,
Even after 10 (cycles) of holding operation, the above-mentioned warping and peeling were not observed.

When I roughly investigated the recording characteristics of this recording medium 33, I found that
It was confirmed that the C/N and error rate did not deteriorate.

Further, for comparison, a recording medium 19 according to a comparative example similar to that described above was prepared, and Ii' Z/AD cycle test J was conducted in the same manner as described above.

As a result, in recording medium No. 9 according to Comparative Example, warping of the substrate 11 and peeling of the recording layer that made it impossible to measure the recording characteristics were observed in 1 (cycle) of the lrZ/AD cycle test. Ta.

As can be understood from the above description, by applying the structure of the first invention of this application, it was observed that the warpage of the substrate was reduced and the adhesion between the substrate and the recording layer was improved.

Structure and manufacturing procedure of magneto-optical recording medium> Next, a recording medium according to an embodiment of the second invention of this application will be described with reference to FIG.

FIG. 2 is a diagram illustrating the recording medium according to the second embodiment using a schematic cross section similar to that in FIG. 1.

As can be understood from FIG. 2, the recording medium 37 according to the second embodiment is made of a protective film 13a, a magnetic layer 1115, and a protective film 1113b on the surface of the substrate 110 under the same conditions as described in the first embodiment. Then, a recording layer 17 is formed. Then, LB cumulative polymerization J135 is formed on the entire surface of the thus obtained magneto-optical recording medium having the same structure as the conventional one under the same conditions as described in Example 1. As a result, as shown in FIG. 2, a magneto-optical recording medium 37 according to Example 2 coated with the L8 cumulative polymer film 35 is obtained.

Incidentally, the recording medium 3 according to Example 2 obtained in this way
After examining the recording characteristics of 7.1, the C/N was 46.
0 (dB), the error rate was about 10-5, and the same characteristics as in Example 1 were obtained.

Adhesion Test> Next, an adhesion test conducted on the recording medium 37 according to Example 2 described above will be described.

First, the Ii' adhesion test j was conducted on the recording medium 37 according to Example 2 under the same conditions as described in Example 1. When the recording characteristics described above were measured regarding the recording medium 37 according to this example, no change was observed in the C/N and error rate, indicating that the substrate 11 was warped,
No peeling between the substrate 11 and the recording layer 17 was observed.

Further, FIGS. 3(A) and 3(B) show the recording medium 37 according to Example 2 as a sample! ? Fz/AD cycle test J was conducted under the same conditions as described above.

As a result, in the recording medium 37 according to Example 2, as in Example 1 described above, the above-mentioned warping and peeling were not observed even after 10 (cycles) of holding operations. The recording layer 'I' of this recording medium 37! Upon investigation, it was confirmed that there was no deterioration in C/N or error rate.

As can be understood from the above explanation, by applying the structure of the second invention of this application, it is possible to reduce the warpage of the substrate,
It was also observed that the adhesion between the substrate and the recording layer was improved.

Although the embodiments of the invention according to this application have been described in detail above, it is clear that the invention is not limited only to these embodiments.

For example, in Example 1, an L8 cumulative polymer film covering the entire surface of a substrate was provided, and in Example 2, a LB cumulative polymer film covering the entire surface of a conventional recording medium was provided. However, as can be understood from FIG. 4, which is shown similarly to FIGS. 1 and 2, after obtaining the recording medium described in Example 1, the L
Even with the magneto-optical recording medium 41 provided with the B cumulative polymer film 39, the same effects as in the above embodiment can be expected.

Furthermore, in the above embodiments, a polycarbonate substrate was exemplified as the substrate made of synthetic resin. Generally, polycarbonate has a heat resistance of about +40 ('C). Therefore, other techniques for forming the LB cumulative polymer film can also be applied as long as they can be carried out at a temperature lower than such a heat-resistant temperature. As such another formation technique, it is also possible to use vacuum deposition polymerization and use an LB cumulative polymer film made of aramid instead of polyimide as exemplified in the above embodiment.

In addition, the effects of the present invention are not limited to the recording medium having the configuration shown in the drawings, but are applicable to recording media having a recording layer including a reflective layer, or other recording media having various lamination relationships. Even when applied to a medium, the same effects as in the above embodiment can be expected.

These materials, arrangement coefficients, numerical conditions, and other specific conditions described above are within the scope of the present invention.
Obviously, any suitable design changes and modifications may be made.

(Effects of the Invention) As is clear from the above description, according to the magneto-optical recording medium of the present invention, an LB cumulative polymer film is provided in each of the above-described configurations. For this reason, at least the substrate is configured to be substantially isolated from the outside air, which eliminates the decrease in adhesion between the substrate and the recording layer mainly caused by the warpage of the substrate, and reduces the deterioration of the characteristics of the recording medium. be able to.

Therefore, by applying the structure of the present invention, it is possible to prevent warpage of a substrate made of synthetic resin, which has excellent mechanical strength and is inexpensive, and to improve the adhesion between the substrate and the recording layer. can provide a magneto-optical recording medium that can stably exhibit excellent characteristics over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a schematic cross section of a substrate in order to explain Embodiment 1 of the present invention, and FIG. 2 is an explanatory diagram shown similarly to FIG. 1 to explain Embodiment 2 of this invention. Figures 3(A) and 3(B) show the 1i'
In order to explain the conditions of Z/An cycle test J, 1(
cycle) temperature or humidity conditions, respectively.
FIG. 4 is an explanatory diagram shown in correspondence with the retention time, and FIG. 4 is an explanatory diagram shown similarly to FIG. 1 to explain other embodiments. FIG. 2 is an explanatory diagram similar to FIG. 1 for explaining the prior art. 11... Substrate, 13a, 13b... Protective film 15... Magnetic film, +7.23.27... Recording layer +9.25, 29, 33.37.41.・・・・・・
Magneto-optical recording medium 21...Reflection film, 31, 35.39
...LB cumulative polymer film. Patent applicant Oki Electric Industry Co., Ltd. 11: Substrate
13a, 13b: Protective film 15: Magnetic film 17: Recording layer
33: Magneto-optical recording medium 31: LB cumulative polymeric film Explanatory diagram of Example 2 FIG. Explanatory diagram Figure 4 Relative humidity rx (%) Figure 5

Claims (2)

[Claims] (1) In a magneto-optical recording medium comprising a recording layer on a substrate made of synthetic resin, the entire surface of the substrate is Langmuir-Blodgett (LB).
1. A magneto-optical recording medium, characterized in that it is coated with a cumulative polymer film and comprises the recording layer on the substrate. (2) A magneto-optical recording medium comprising a recording layer on a substrate made of synthetic resin, characterized in that the entire surface of the magneto-optical recording medium is coated with a Langmuir-Blodgett (LB) cumulative polymer film. Magneto-optical recording medium.