JPS6286551A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a light recording medium with a high sensitivity and a satisfactory reproducing signal and servo signal by forming a recording layer with a composite film composed of a film with organic substance sandwiched by an island shaped non-continuous thin film as a substantial component. CONSTITUTION:On a substrate 10, an island-shaped non-continuous thin film 11 is formed by the vapor deposition of the gold, platinum, palladium, etc. On the film, a film 12 with respective types of a naphthoquinone coloring matter, an anthraquinone coloring matter and other organic substances as the substantial component and an island shaped non-continuous thin film 13 are formed. To the composite film, a laser beam 14 is condensed and irradiated, and then, films 11 and 13 are locally agglomerated and the bit is formed at the film 12.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an optical recording medium on which information can be recorded and reproduced using laser light, and more particularly to an optical recording medium whose main component is an organic substance.

(Prior Art) A write-once optical disk memory that records and reproduces information on a medium using a laser beam has an excellent feature as a large-capacity recording device because of its high recording density. Recording media for such write-once optical disk memories include Te and B.
Semimetallic thin films and organic thin films such as i are used (for example, Japanese Patent Publication No. 15483/1983). Organic thin films have thermal properties superior to semimetal thin films, that is, low thermal conductivity and small heat damage te, so that the temperature rise of the film per absorbed energy density is large, and high recording sensitivity can be expected.

(Problem to be solved by the invention) However, organic thin films cannot be used in the wavelength range of semiconductor lasers (~800
Since a semimetal thin film does not exhibit a large reflectance in the wavelength range (nm), when a semiconductor laser is used as a reproduction light source, a problem arises in the quality of reproduction signals and servo signals. Furthermore, since organic thin films exhibit a higher absorption rate than metalloid thin films, problems arise in terms of sensitivity.

In other words, an object of the present invention is to provide an optical recording medium with large reproduction signals and servo signals and high sensitivity.

(Means for Solving the Problems) The optical recording medium of the present invention is an optical recording medium in which a recording layer is provided on a substrate, information is recorded and read by irradiation with laser light, and the recording layer has an island shape. It is characterized by being formed by a composite film consisting of a film whose main component is an organic substance sandwiched between ultra-thin discontinuous films.

(Function) The reflectance of light incident on the substrate of an optical recording medium in which a recording layer is formed on a transparent substrate depends on the optical constants (complex refractive index) of the recording layer and the substrate and the thickness of the recording layer. Various synthetic resins or glass are usually used as the transparent substrate. These refractive indexes are approximately 1.5 in the visible light to near-infrared light range, and are highly dependent on wavelengths in this range. Therefore, the reflectance of the medium is determined by the optical constants and thickness of the recording layer.

When an organic dye film, a dye-dispersed resin film, or a metal-dispersed organic film is used as the recording layer, the complex refractive index of these films (at most 2 in the n-th OF1 semiconductor laser wavelength range (~800 nm)) .7-i 1.7, and a stable one is at most 2.6-i 0.8.For example, if the complex refractive index of the recording layer is 2.1-+0.
7 and the refractive index of the substrate is 1.5, the wavelength is 830n
The medium reflectance and absorption of the substrate incident at m depend on the thickness of the recording layer, as shown in FIG. When the thickness of the recording layer is 60 nm, the reflectance is 10.1 and the absorption is 48.
．． 6% is obtained, and it can be seen that these values are small. The problem of low reflectance and low absorption can be solved by one example of the structure of the medium of the present invention shown in FIG. That is, the known recording layer of the substrate 10 is formed by a composite film consisting of an island-shaped ultra-thin discontinuous film 11, an organic material-based film 12, and an island-shaped ultra-thin discontinuous film 13. There is. By irradiating the laser beam 14 in a concentrated manner, the island-like ultra-thin discontinuous films 11 and 13 are locally agglomerated, and pits are formed in the film 12, which is made up entirely of organic matter.

FIG. 2 shows a substrate 10 with a complex refractive index of 4.0 on a substrate 10 with a refractive index of 1.5.
Island-shaped discontinuous film 11 with a thickness of 3% m of 0-13.5
An organic dye 112i with a complex refractive index of 2.1-io and 7 is formed thereon, and an organic dye 112i with a complex refractive index of 4.0-i is formed thereon.
3.5 3 nm thick island-shaped discontinuous film 13i
The graph shows the dependence of the substrate incident reflectance and absorption on the organic dye film thickness when provided. By comparing with FIG. 3, it can be seen that the structure of the present invention is improved by increasing the reflectance and the absorption rate.

The island-shaped discontinuous film has a width of about 2 to 1100 nm and a thickness of 1 to several tens of nanometers, and is preferably made of gold, palladium, or platinum. Other materials include silver, copper, and rhodium, and alloys containing these as main components may also be used.

The organic film 12 is a plasma-polymerized organic film containing various organic dyes such as various naphthoquinone dyes, various anthraquinone dyes, various squarylium dyes, and various phthalocyanine dyes, Te, Bi, etc., and Te, Bi, etc. surrounded by alkyl groups. An organic film in which Te, Bi, etc. are surrounded by fluorocarbon, a resin film in which various dyes are dispersed, a resin film in which various metal compounds are dispersed, etc. can be used. In particular, 5-amino-8-substituted anilino-2,3-dicyano-1,4-naphthoquinone dyes, 5,8-substituted anilino-2,3-dicyano-1,4-naphthoquinone dyes, or mixtures thereof. Alternatively, their complexes are preferable, and as the substituent, an alkoxyl group or an alkyl group having 4 or less carbon atoms is most preferable. Furthermore, vanadyl phthalocyanine dyes or alkyl-substituted vanadyl phthalocyanine dyes are preferable. Various materials can be used as the substrate, but synthetic resins, glass, and porcelain are generally preferable. Examples of synthetic resins include acrylic resins such as polymethyl methacrylate, polycarbonate, polyetherimide, polysulfone, epoxy resins, and vinyl chloride resins. The substrate may be provided with a heat insulating layer or a smoothing layer thereon. The shape of the board is a frame, disc-shaped.

It can be in the form of a sheet or tape.

Information is recorded on the recording layer by forming all pits on the recording layer. In a disk medium using a disk-shaped substrate, recording is performed by forming a number of concentric or spiral tracks with pitches Nd. In order to accurately record a large number of tracks at regular intervals, light guide grooves are usually provided on the substrate. When light enters a groove about the diameter of the beam, it is diffracted. As the beam center shifts from the groove, the spatial distribution of the diffracted light intensity changes, and a servo system can be configured to detect this and direct the beam to the center of the groove. Generally, the width of the groove is set to 0.3 to 1.2 μm1, and the depth is set within the range of 1/12 to 1/4 of the wavelength of the recording/reproducing laser used. The recording medium of the present invention is formed on the grooved surface of a substrate.

Examples of the present invention will be described below.

(Example 1) On an acrylic resin disk substrate with a guide groove having an inner diameter of 15 w*, an outer diameter of 120+s, and a thickness of 1.2 mm, a thickness of 2 nm of gold was deposited by electron beam heating, and then by resistance heating in the same vacuum device. 95% by weight of 5-amino-8-(p-ethoxyanilino)-2,3-dicyano-14-naphthoquinone dye and "t8-(p-ethoxyanilino)-2,
A mixture of 5 wt.
A recording layer of a composite film was formed by vapor deposition to a thickness of m. Wavelength 830n
The medium reflectance and absorption rate when the substrate is incident on m are 14 and 58, respectively, which is 10% of that for a single layer of organic dye film.
, which is a significant improvement over the 49th model. Also, linear speed 5m/
sec, even with a laser power of 5 mW, sufficient recording was possible, and the servo signal was large and good.

(Example 2) In the same manner as in Example 1, instead of 2 m thick gold, K 3
A recording medium was produced using nm-thick palladium. The medium reflectance and absorption coefficient of the substrate incident at a wavelength of 830 nm were 141 and 59 cm, respectively, which was a significant improvement over the case of a single layer of organic dye film.

When we conducted a recording/reproduction experiment using a semiconductor laser, we found that
It has high sensitivity and can record well, and the servo signal is also large and good.

(Example 3) In the same manner as in Example 1, 2.5 m thick gold was used instead of 2 m thick gold.
M-thick gold and palladium alloy (50:50 by weight)
2 to produce a recording medium. The medium reflectance and absorption of the substrate incident at a wavelength of 830 nm are each 14 cm,
It was 59%, which was significantly improved compared to the case of a single layer of organic dye film. When a recording/reproduction experiment was conducted using a semiconductor laser, good recording was possible with high sensitivity, and the servo signal was also large and good.

(Example 4) In the same manner as in Example 1, instead of 2 m thick gold, 3 n
A recording medium was produced using platinum with a thickness of m.

The medium reflectance and absorption rate of the substrate incident at a wavelength of 830 nm were 14% and 54%, respectively, which were significantly improved compared to the case of a single layer of organic dye film. When we conducted a recording/reproduction experiment using a semiconductor laser, we were able to record with high sensitivity and good quality, and the servo signal was also large and good.

(Example 5) On a polycarbonate resin disk substrate with a guide groove having an inner diameter of 15 m, an outer diameter of 130 m, and a thickness of 1.2 m, gold was evaporated to a thickness of 2 m by electron beam heating, and then the resistance was measured in the same vacuum apparatus. A vanadyl-7 talocyanine dye was vapor-deposited thereon by heating, and an organic dye film with a thickness of 30 meters was completely deposited.Following this, gold was vapor-deposited to a thickness of f 2 nm by electron beam heating in the same vacuum apparatus to form the recording layer of the composite film. Formed. At a wavelength of 830 nm, the medium reflectance and absorption coefficient when incident on the substrate are 13 and 50, respectively, which are 11% and 31% of the organic dye film single layer.
This is a huge improvement over Chi. Using a semiconductor laser with a wavelength of 830 nm, good recording was possible at a linear velocity of 5 rrl/see and a laser power of 7 mW, and the servo signal was also good.

(Example 6) In the same manner as in Example 5, 2.5 m thick gold was used instead of 2 m thick gold.
A recording medium was fabricated using palladium with a thickness of 1.5 m. The medium reflectance and absorption of light incident on the substrate at a wavelength of 830 nmK were 12% and 49%, respectively, which were significantly improved compared to the case of a single layer of organic dye film. When we conducted all recording and playback experiments using a semiconductor laser in its entirety, we were able to achieve good recording with high sensitivity.
The servo signal was also good.

(Effects of the Invention) As is clear from the above embodiments, the present invention provides an optical recording medium with high sensitivity and excellent reproduction signals and servo signals.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an optical recording medium that is an embodiment of the present invention;
Figure 2 is a diagram showing changes in the reflectance and absorbance of an optical recording medium according to an embodiment of the present invention depending on the organic film thickness, and Figure 3 is a diagram showing the reflectance and absorbance of a conventional optical recording medium depending on the organic film thickness. It is a figure showing the change depending on the size. In the figure, 10 is a substrate, 11, 13tj discontinuous film, 1
2tlj organic film, 14Fi light shown. Figure 1 anti) Toshin, 0 and H and Kei ('/) Erasehada 1 (m) Anti-body size, O and condolence (%) 14 Fudai Tumor Liao (Labor Wei)

Claims (1)

[Claims] In an optical recording medium in which a recording layer is provided on a substrate and information is recorded and read by irradiation with a laser beam, the recording layer is composed of a film mainly composed of an organic substance sandwiched between extremely thin discontinuous island-shaped films. An optical recording medium characterized by being formed of a composite film.