JPS62141660A - Optical recording medium - Google Patents

Abstract

PURPOSE:To provide an optical recording medium having good weatherability and signal quality by forming a layer consisting of 3,4,9,10-perylene tetracarboxylic dianhydride between a substrate and recording layer. CONSTITUTION:The layer 3 consisting of the 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) is inserted between the substrate 1 and the recording layer 2. Warpage is thereby prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium on which information can be recorded and reproduced using laser light.

(Prior Art) Write-once optical disk memory or magneto-optical disk memory that records and reproduces information on a medium using laser light is
Because of its high recording density, it has excellent characteristics as a large-capacity recording device. The recording layer of such an optical disk memory is a semi-metal thin film such as bismuth or tellurium
6-40479, Special Publication No. 5745676, Special Publication No. 59-
41875, Special Publication No. 54-15483, Special Publication No. 59-3
5356) and alloy thin films of rare earths and transition metals (Special Publication No. 57
An inorganic recording layer such as JP-B-20691) or an organic recording layer (Japanese Patent Publication No. 6O-23996) is used.

(Problems to be Solved by the Invention) Although inorganic recording layers have the advantage of exhibiting higher reflectance than organic recording layers, they have the problem of poor weather resistance.

An object of the present invention is to provide an optical recording medium with good weather resistance and good signal quality.

(Means for Solving the Problems) The optical recording medium of the present invention is an optical recording medium in which an inorganic recording layer is provided on a substrate, and information is recorded and read by irradiation with a laser beam, and the optical recording medium includes the substrate and the recording layer. Between 2 and 3
, 4,9,10-perylenetetracarboxylic acid.

(Function) Optical recording media conventionally have a structure as shown in FIG. That is, a recording layer 2 is provided on a substrate 1.

As the substrate 1, synthetic resin is used. As the synthetic resin, acrylic resin such as polymethyl methacrylate is most desirable in terms of optical properties. The shape of the substrate can be a disk, a sheet, or a tape. As the recording layer 2, an inorganic recording layer that can increase the reflectance is suitable. As an inorganic recording material, Te or Bi is suitable in terms of recording properties, but when weather resistance is also taken into consideration, a mixture of Sn and NiO, a mixture of Sn and Co3O4, a mixture of Te and NiO, a mixture of Te and Co3O4, etc. A mixture of is most desirable. Information is recorded on the recording layer by forming pits in the recording layer. In a disk medium using a disk-shaped substrate, recording is performed so that pits are formed in a large number of concentric or spiral tracks. 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. Usually, the width of the groove is set in the range of 0.3 to 1.2 pm, and the depth is set in the range of 1112 to 1/4 of the wavelength of the recording/reproducing laser used.

When the optical recording and reproducing characteristics of such conventional optical recording media were measured after being stored under conditions of high temperature and high humidity, it was observed that the characteristics often deteriorated. The inventor investigated the cause of this problem and found that it was due to the synthetic resin substrate being warped, and as shown in FIG. Tetracarboxylic acid (
It has been found that warping can be prevented by inserting a layer 3 of PTODA (hereinafter abbreviated as PTODA).

(Example) Examples of the present invention will be described below. Inner diameter 15mm
, an acrylic resin disk substrate with an outer diameter of 120 mm and a thickness of 1.2 mm was placed in a vacuum evaporation apparatus, and heated to 2X10-5 Tor.
Exhausted to below r. As evaporation sources, Sn was placed in a molybdenum resistance heating boat, PTODA was placed in another molybdenum resistance heating boat, and Co3O4 was placed in an electron beam heating crucible. Matu PI'ODA 35
After zero deposition, a mixture of Sn and Co3O4 was formed as a recording layer by co-evaporation. Co-evaporation was carried out using a crystal oscillator type film thickness monitor, and the deposition rate of Sn was 45 people per minute and Co
The evaporation rate of 3O4 was set at 17 per minute to form a 0-thick film for 300 people. When the optical characteristics of the flat portion of this optical recording medium were measured using parallel light having a wavelength of 8,300, the substrate incident reflectance was approximately 30% and the absorption rate was approximately 55. Wavelength 8300
A human AlGaAs semiconductor laser was focused using an optical system and irradiated onto the recording layer through the substrate to form pits in the recording layer. Disk rotation speed 900ypm, recording frequency 1.2
The recording laser power required at 5 MHz (50% duty) was 7 mW. When the recorded pits were reproduced with a laser power of 0.7mW, the bandwidth was 30KH.
The signal-to-noise ratio (C/N) of z was 48 dB or more, and the second harmonic-to-signal ratio (2ndH/C) was -26 dB or less, so a signal of good quality was obtained. Next, this optical recording medium is
After storing for 60 hours in an environment of 80% high temperature and high humidity, the above characteristics were examined, but no changes were found. PTOD for comparison
In the case of a disc with no layer A, the warpage of the disc was measured in recording/reproducing characteristics after a high temperature and high humidity test.
The recording laser power at which ndH/C shows the minimum value is 10 mW.
and deteriorated. As another comparison, attempts were made to use guanine, Al2O3, or MgO instead of PTODA, but warpage occurred in the disks in all cases.

Experiments were also conducted using a mixture of Sn and NiO, a mixture of Te and NiO, and a mixture of Te and Co3O4 as the recording layer, but the results were similar in all cases.

(Effects of the Invention) As is clear from the above embodiments, the present invention provides an optical recording medium with good weather resistance and good signal quality.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of the optical recording medium of the present invention;
FIG. 2 is a schematic cross-sectional view of a conventional optical recording medium. In the figure, 1 is a substrate, 2 is a recording layer, and 3 is a PTCDA layer.

Claims (1)

[Claims] In an optical recording medium in which an inorganic recording layer is provided on a substrate and information is recorded and read by irradiation with laser light, 3,4,9,10-perylenetetracarboxylic dianhydride is present between the substrate and the recording layer. An optical recording medium characterized by forming a layer of.