JP2821155B2 - Information recording medium - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a signal obtained by FM-modulating an analog signal such as video or audio by a recording energy beam such as a laser beam or an electron beam, or data of an electronic computer. The present invention relates to an information recording medium capable of recording digital information such as digital signals and digital audio signals in real time.

[Conventional technology]

As a conventional technique relating to an information recording medium for irradiating an information recording medium with an energy beam such as a laser beam and forming a concave portion or a hole in a recording film to record information, for example, Japanese Patent Application Laid-Open No. Japanese Patent Application Laid-Open No. 58-44224 and the like are known for the composition of the base film.

[Problems to be solved by the invention]

However, in the arts known so far, including the information recording medium shown in the above-mentioned prior art, no consideration is given to the shape of the recorded hole. According to the studies by the inventors, when the angle between the inclination inside the rim and the bottom surface (referred to as the contact angle) is large and the rim width is small, high-density recording (pit interval 1.5 μm) is performed. SN
There is a problem that the ratio is small, the crosstalk is large, and the recording light power margin is small.

SUMMARY OF THE INVENTION An object of the present invention is to provide a thin film for information recording which eliminates the above-mentioned disadvantages of the prior art, has good recording and reproducing characteristics, and has good stability.

[Means for solving the problem]

In order to achieve the above object, in the information recording medium of the present invention, the angle formed by the base film inside the rim formed around the concave portion or the hole formed by the irradiation of the recording energy beam. (Contact angle) is 7 degrees or more and 40 degrees or less. However, a more preferable range of the contact angle is 8 degrees or more.
35 degrees or less, a particularly preferable range is 10 degrees or more and 30 degrees or less.

As long as the above conditions are satisfied, the substrate material may be an organic material such as acrylic resin, polystyrene, polycarbonate, epoxy resin, polyimide, polyamide, polystyrene, polyethylene, polyolene fin, ultraviolet curable resin, glass, quartz, An inorganic substance such as aluminum may be used.

As a base film, if a thin film can be formed by vapor deposition, sputtering, plasma polymerization, spin coating, or the like, organic materials such as fluororesin, polyimide, polyamide, guanine, phthalocyanine, acetylcellulose, and nitrocellulose can be used as SiO ₂ , ZrO _2. , Y ₂ O ₃ , etc., oxides, Si ₃ N ₄ , AlN
And inorganic materials such as nitrides. Further, the recording film may be an organic substance such as a dye or an inorganic substance such as a Te-Se type or a Te-C type.

The information recording medium of the present invention can be used not only in a disk shape but also in other forms such as a tape shape and a card shape.

[Action]

In the information recording medium of the present invention, since the contact angle inside the rim formed around the hole formed when the recording energy beam is irradiated is small, the inside diameter of the hole is small. Thus, even when performing high-density recording, a recording medium having a large SN ratio, small crosstalk, and a large recording light power margin can be obtained.

〔Example〕

Example 1 As shown in FIG. 2, a polycarbonate substrate 2 having a 1.6 μm pitch tracking guide groove and a pre-pit indicating an address formed on the surface thereof was used. First, a magnetron was formed on the polycarbonate substrate 1 as a base film. A fluorine resin (polytetrafluoroethylene, PTFE) layer 3 was formed to a thickness of about 400 mm by spattering (sputter gas was Ar 100%). Next, Pb ₅ Te ₈₀ S
the film thickness of the recording film 4 of about 200Å composition of e _15, magnetron spa ivy ring (Supatsutagasu the Ar 100%) have been conducted under formed.

Recording in an optical disk drive (recording / reproducing apparatus) was performed as follows. The disk is rotated at 1800 rpm, and the light of the semiconductor laser (wavelength 820 nm) is kept at a level (about 1 mW) at which recording is not performed. By detecting the reflected light, the head was driven so that the center of the light spot always coincided with the tracking groove. In this way, while performing tracking, automatic focusing is performed so that the focal point is further focused on the recording film, and in the portion where recording is performed, as shown in FIG. And the laser power was modulated. After passing the part to be recorded, reduce the laser power to 1 mW and continue tracking and autofocus. For reading, the disk is rotated at 1800 rpm, tracking and automatic focusing are performed in the same way as during recording, while the intensity of the reflected light is detected with a low power laser beam of 1 mW that does not change the recording film, and the information is read. Replayed.

In the information recording medium having the above-described configuration, the recording power dependence of the reproduction signal output when recording is performed at a place having a radius of 30 mm with a recording pulse width of 1T (T = 90 ms) and a pitch interval of 1.5T (high-density recording). It is shown in FIG. As a reference example,
FIG. 4 (b) shows a case where the thickness of the base PTFE film is 2000 °.

In the experiment described above, the cross-sectional shape (surface shape in the diameter direction) of the hole measured with a scanning tunneling microscope (STM) or surface morphology analysis scanning electron microscope (ESA) when the recording power was 5.5 mW was measured. As shown in FIG.

When the thickness of the underlayer PTFE film is 400 °, the contact angle 1 is 20 degrees, and the reproduction signal output is 0.17V, which is higher than the slice level (0.14V) even during recording with a pit interval of 1.5T high power (8mW). On the other hand, when the thickness of the base PTFE film is 2000 °, the contact angle is 45 degrees, the pit interval is 1.5 T, and at the time of high power (8 mW) recording, the reproduced signal output is 0.13 V, which is lower than the slice level.

Example 2 When the thickness of the base PTFE film sputtered with Ar gas was 100
FIG. 5 shows the results of measuring the contact angle of the pit recorded at a high power (8 mW) when the angle was changed from Å to 2200 °.
As shown in the figure, the larger the thickness of the underlying PTFE film, the larger the contact angle.

In addition, O ₂ is added to Ar
FIG. 6 shows the result of measuring the contact angle of a pit recorded at a high power (8 mW) while changing the O ₂ partial pressure from 0% to 45% when the FE film was formed at 400 °. The greater the O ₂ partial pressure, the greater the contact angle.

Next, based on the above results, the contact angle dependence of the reproduction signal output at the time of high power (8 mW) recording at a pitch of 1.5T is summarized as shown in FIG.

When the contact angle is 7 degrees or more and 40 degrees or less, a reproduction signal output higher than the slice level A (0.14 V, which is a condition suitable for the apparatus) is obtained. When the contact angle is 8 degrees or more and 35 degrees or less, the slice level is obtained. B (0.15 V, general condition for the device) or higher, and when the contact angle is 10 degrees or more and 30 degrees or less, the slice level is C (0.16 V, a loose condition for the device) or higher. The reproduction signal strength of was obtained.

As the substrate material, acrylic resin, polystyrene, epoxy resin, polyimide, polyamide, polyethylene, polyolefin,
Similar results were obtained by using UV curable resin, glass, quartz, aluminum and the like.

Similar results were obtained by using a fluororesin other than PTFE, polyimide, polyamide, guanine, phthalocyanine, acetylcellulose, nitrocellulose, etc. instead of PTFE as the base film.

As the recording film, instead of the above-mentioned Pb-Te-Se system, Te-C
Similar results were obtained using other chalcogenide-based recording films such as a recording system, Te-Sb system, or organic recording films such as dyes.

[Effects of the Invention] As described above, the use of the information recording medium according to the present invention makes it possible to obtain a large reproduction signal output even when performing high-density recording because the contact angle of the recorded hole inside the rim is small. This has the effect that the crosstalk is small and the recording power margin is large.

[Brief description of the drawings]

FIG. 1 is a sectional view of a hole formed by laser beam irradiation in an embodiment of the present invention, FIG. 2 is a sectional view showing the structure of an information recording medium of the present invention, and FIG. 3 is an embodiment of the present invention. FIG. 4 is a measurement diagram of the recording power dependence of a reproduction signal output in the embodiment of the present invention, and FIG. 5 is a dependence of the contact angle on the thickness of the PTFE film in the embodiment of the present invention. FIG. 6 shows the PT in the embodiment of the present invention.
FIG. 7 is a measurement diagram showing the relationship between the partial pressure of O _{2 in the} sputtering gas and the contact angle of the pit during the formation of the FE film. FIG. 7 shows the reproduction signal output when recording with a laser power of 8 mW in the embodiment of the present invention. FIG. 6 is a measurement diagram showing a relationship between the contact angle and the contact angle. 1 ... contact angle, 2 ... polycarbonate substrate, 3 ... base film, 4 ... recording film.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Noriyoshi Horigome 1-280 Higashi Koikekubo, Kokubunji-shi, Tokyo Inside the Central Research Laboratory, Hitachi, Ltd. Central Research Laboratory (72) Inventor Akira Goto 1-188 Ushitora, Ibaraki-shi, Osaka Hitachi Maxell, Ltd. (56) References JP-A-55-101143 (JP, A) (58) Fields investigated .Cl. ⁶ , DB name) G11B 7/24 563 G11B 7/24 561

Claims (1)

(57) [Claims] An information recording medium in which a concave portion or a hole is formed in a recording film upon irradiation of a recording energy beam, a fluororesin layer is provided between the substrate of the information recording medium and the recording film. The thickness of the fluororesin layer is set so that the angle formed between the inner slope of the rim formed around the concave portion or the hole and the bottom surface of the concave portion or the hole is not less than 7 degrees and not more than 40 degrees. An information recording medium characterized by being recorded.