JPS5981193A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium having large absorption to laser light of semiconductor and capable of recording information with little optical beam energy, by making naphthol green B and PVA be contained into a recording film. CONSTITUTION:The aimed recording medium is obtained by a method wherein the mixture of naphthol green B of the formula and PVA is dissolved with water and the recording film is formed by coating it on, for example, the aluminum film of glass plate equipped with aluminum film. Thus, the miniaturization and high density recording of optical information recording medium can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a medium for recording and reproducing information using a light beam, and particularly to a medium for recording using a semiconductor laser as the light beam.

Conventionally, an optical information recording film is irradiated with a light beam, and the light energy or thermal energy of the light beam is used to form minute irregularities (c pits) on the optical information recording film, or to change transmittance, refractive index, etc. Information is recorded by causing a change in optical properties, and then a weak light beam is irradiated onto the optical information recording film on which information is recorded, and the light beam is reflected from the bit or the part where the optical properties change. High-density optical information recording media that read changes in the amount of reflected light or changes in phase are known.

The light beam must concentrate high-density energy in a minute area, and generally a gas laser such as argon (Ar) or helium-neon (He-Ne) or a GaAlAs semiconductor laser is used. used. 1r, He-Ne laser light is visible light with wavelengths of 488 nm and 633 nm, and semiconductor laser light is near-infrared light with wavelengths of 780 to 850 nm. Ar and He-Ne laser beams have large outputs of 1 to IOW and 50 mW, respectively, but require a modulator because the dimensions of the laser tube are large and the laser beam output cannot be directly modulated by the recording information signal. Therefore, optical information recording and reproducing apparatuses using Ar or He-Ne lasers have the disadvantage of being large. On the other hand, semiconductor lasers have the advantage of being able to produce outputs of 5 to 15 mW.

The information recording film has a large absorption coefficient for the recording light beam. ■Low thermal conductivity. ■Shows melting and evaporation or changes in optical properties such as reflectance and refractive index at the lowest possible temperature above room temperature. This is necessary. Such optical information recording films include tellurium (Te l and bismuth (B).
Metals, organic and inorganic dyes and pigments, and metal-organic composites such as j) may be used. Organic dye has a wavelength of 450nm to 750n
It absorbs visible light of m wavelength, and has low absorption of near-infrared light of 750 nm or more.

Therefore, when recording information by irradiating a semiconductor laser beam onto an optical information recording medium that uses an organic dye as a recording film, the disadvantage is that a large amount of light beam energy is required for recording because the laser light absorption of the recording film is small. There is.

The present invention has been made to eliminate such drawbacks, and provides an optical information recording medium that can increase the absorption of semiconductor laser light by an organic dye recording film and record information with small light beam energy. The purpose is to

The present invention is characterized in that, in an optical information recording medium that records and reproduces information using a light beam, the recording film of the optical information recording medium is made of naphthol green B and polyvinyl alcohol (p
, v A ).

The present invention will be explained below.

Known as food coloring and wool super acid dye. The spectral absorption characteristics of an aqueous solution of naphthol green B are as shown by solid line 1 in Figure 1, with a maximum absorption wavelength of 730 nm and 78 nm.
Absorption in the near-infrared region of 0 to 850 nm is small.

The absorption of naphthol green B in the long wavelength range of visible light is based on the electronic resonance of the nitroso group, which is a chromophore.

C:/-N=OHqN-0-4-□"C:?=N-0-
When an auxochrome with a bathochromic effect is introduced into naphthol green B, it can be shifted to the maximum absorption wavelength side, and the absorption of light in the wavelength range of 780 to 850 nm, which is the wavelength range of semiconductor laser light, can be increased.

In the present invention, naphthol green B is produced by mixing polyvinyl alcohol having a hydroxyl group (OH group), which is an auxochrome that exhibits the bathochromic effect, with naphthol green B.
The maximum absorption wavelength of the laser beam is shifted to the longer wavelength side, thereby increasing the absorption of semiconductor laser light.

PvA has an OH group in the structure OH represented by +-CH2-CH+r] and is a polymer compound obtained by saponifying polyvinyl acetate. Excellent adhesion, film forming properties,
Because it is colorless and transparent, it is widely used in fibers, films, adhesives, etc.

PVA is partially saponified PVA with a saponification degree of 86-89%.
.

Completely saponified PVA with saponification degree of 95-99tI), O
Modified PVA in which a portion of H groups are replaced with other functional groups
However, any PVA is effective in the present invention. This means that in any PVA, a portion of the OH group is C.
This is because most OH groups remain as they are, replaced by H3COO groups or other functional groups.

Dissolve a mixture of naphthol green B and PVA in water,
Thereafter, the spectral absorption characteristics of the information recording film according to the present invention, which was made into a film by evaporating water, are shown by the solid line 2 in Figure 1, and the maximum absorption wavelength was 775 nm, and in the wavelength range of 780 to 850 nm, which is the wavelength range of semiconductor laser light. It has greater absorption than a recording film made of naphthol green B alone.

Therefore, the optical information recording medium of the present invention allows information to be recorded with small laser beam energy.

Next, examples of the present invention will be described.

Example 1 An aluminum (hL) thin film was formed on a double-sided optically polished glass plate with a thickness of 1 and 2 mm and a diameter of 200 mm by vacuum evaporation, and a recording thin film made of a mixture of naphthol green B and PvA was further formed on the Al pattern. It was formed into an optical information recording medium.

The recording thin film is produced as follows.

The above composition is heated and stirred to completely dissolve it, and then cooled to room temperature. Next, when the above composition solution is dropped onto the hL thin film of the glass plate having an Al thin film on one side rotating at high speed, naphthol green 13. A PVA mixture recording film is formed. This optical information recording medium has a wavelength of 8
When 30 nm GaAJLAs semiconductor laser light was irradiated, the minimum light beam energy necessary to record information was 70 mJ/cm2.

For comparison with this example, an optical information recording medium was prepared in the same manner using a water-soluble acrylic resin instead of PVA in this example, and recording was performed using a semiconductor laser, and information was recorded.

The minimum optical beam energy required for
2τ゛It requires a light beam energy 1.6 times larger than that of this embodiment.

Example 2 In Example 1, PVA (completely saponified) was replaced with PVA
When a recording experiment was conducted instead of (partial saponification), the required minimum beam energy was 75 mJ/cm2.

Example 3 A similar recording experiment was conducted in Example 1 by replacing PVA (completely saponified) with modified PVA that had been modified with 10 mole urethane.The minimum required light beam and energy were 70m.
J/cm2.

In the above examples, the PV of naphthol green B
Although the weight ratio to A is set to 2, in the present invention, the weight ratio is not limited to 2, but can be in the range of 0.2 to 5, and more preferably in the range of 0.3 to 3. When the weight ratio is less than 5, crystals of naphthol green B precipitate in the recording film, and information is not recorded in that portion, which is not preferable. When the weight ratio is less than 0.2, the amount of laser light absorbed by the recording film is small, and therefore the recording film thickness must be increased to increase the amount of laser light absorbed, and the light beam energy required to record information is reduced. This is not desirable because it becomes a dog.

Example 4 An optical information recording medium having the composition of the recording film in Example 1 was prepared and a recording experiment was conducted, and the minimum required light beam energy was 85 mJ/cm2.

Water-soluble acrylic resin 100 shown in comparison of Example 1
Information can be recorded with 2 ounces less light beam energy than in the case of .

As explained above, in the optical information recording medium according to the present invention, since the recording film contains naphthol green and polyvinyl alcohol, the wavelength is 78Qnm to 850nm.
Absorption of semiconductor laser light of m is large. Therefore, if information is recorded on the recording medium using a laser beam in this wavelength band, the required laser beam energy can be reduced, and the optical information recording medium can be made smaller.

High-density recording is possible.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the spectral absorption characteristics of the recording film of the optical information recording medium of the present invention. 1 is the spectral absorption characteristic of the naphthol green B aqueous solution, and 2 is the spectral absorption characteristic of the recording film of one example of the present invention. Applicant Nippon Columbia Co., Ltd. Hamamatsu Television Co., Ltd. j′+a=:2-7

Claims (1)

[Claims] An optical information recording medium on which information is recorded by irradiation with a light beam, wherein a recording film of the optical information recording medium contains naphthol green B and polyvinyl alcohol.