JPH0497890A - Optical recording medium - Google Patents

Abstract

PURPOSE:To increase the contrast of the rate of reaction of regenerating laser beam to a recording part and a non-recording part by adding a specific electron donating compound and a specific electron acceptive compound and reacting both of them by the irradiation with writing laser beam to form a compound absorbing reading laser beam. CONSTITUTION:The optical recording medium formed on a transparent substrate 4 contains an electron donating compound composed of at least one kind of a compound among an org. reducing agent such as tannin 5 or hydroquinone, a chelating agent, a sulfur compound and an amino compound and an electron acceptive compound composed of a metal salt of org. acid, for example, ferric stearate 6. For example, when the optical recording medium is irradiated with laser beam such as laser beam of a GaAlAs system at the time of writing, the electron donating compound and the electron acceptive compound are reacted to develop a color. For example, when the optical recording medium is irradiated with laser beam lower in energy of the same system at the time of reading, the developed color part is enhanced in the absorptivity of laser beam as compared with a non-recording part and the contrast of reflectivity is largely taken.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a write-once optical recording medium using an organic dye.

Conventional technology Conventionally, write-once optical recording media using laser light have been recorded on transparent substrates such as glass or polycarbonate resin.
A typical method was to create a thin film using vacuum evaporation or sputtering, and then irradiate it with recording laser light to melt and sublimate the recording film to form a hole (focus). . In this case, since Te is easily oxidized in a humid environment, a small amount of metal elements such as Se, In, Sn, Pb, Sb, and Bi are added to prevent oxidation. However, it is very difficult to form a thick film while keeping the ratio of Te and the above-mentioned additional metal elements constant using a dry method such as vacuum evaporation or Nupasota method when forming a thin film, which reduces the productivity of optical disks. There was a problem of low yield.

In order to form holes while preventing Te oxidation, this type of disc requires two discs to be pasted together with the recording film inside, leaving a space between them, making it a write-once CD. Use of a single-panel construction was not possible without reliability.

However, other methods include JP-A-57-11090, JP-A-60-203488, and JP-A-63-10.
As disclosed in Japanese Patent Application Laid-open No. 2988 and Japanese Patent Application Laid-open No. 63-82789, a resin thin film containing an organic dye alone or containing an organic dye is similarly deposited on a glass or polycarbonate substrate by vacuum evaporation method or with a dye material. In this method, a solution dissolved in a solvent is coated by the Nupin coating method and used as a recording medium, and data is recorded by laser irradiation during writing, decomposition reaction of the dye, deformation of the resin as a recording film, etc. This method is suitable for mass production in that a recording film can be formed relatively easily by using a coating method such as the Nupin coating method, and has been widely studied. Other advantages include that since the recording film is an organic material, there is no oxidation problem like the metal To film mentioned above, and because the thermal conductivity is lower than that of metal, the recording density with laser light can be increased. There is also.

Problems to be Solved by the Invention With such a conventional configuration, there is no stability against repeated playback after recording, and the light resistance to general visible light is low. No matter how the absorption rate of the laser beam is designed, it is impossible to obtain a sufficiently large contrast between the reflectance of the recorded area and the unrecorded area with respect to the reproduction laser beam after recording. In other words, in order to cause a sufficient reaction with the dye, it is necessary to use a dye that increases the absorption rate of the writing laser beam in the recording layer, and also to set the recording film thickness thick, so that the reproduction of the recorded area during playback is difficult. Although the laser reflectance decreases, at the same time, the reflectance of the reproduction laser beam in the unrecorded area also decreases, and a sufficient contrast in the intensity of the reproduction laser beam depending on the presence or absence of recording cannot be obtained. On the other hand, if the thickness of the recording film is set so that the reflectance of the reproduction laser beam in the unrecorded area becomes high during reproduction, the absorption rate of the laser beam during writing will be small and the pigment reaction will be sufficient. This will no longer occur, and the reflectance of the reproducing laser beam of the recording section will also increase, and the contrast of the reflectance of the reproducing laser beam depending on the presence or absence of recording will decrease. In this sense, special measures are required to increase the contrast in the reflectance of light during reproduction depending on the presence or absence of recording.

An object of the present invention is to increase the contrast in reflectance of reproduction laser light between recorded areas and unrecorded areas when such an organic dye is used as a recording material.

Means for Solving the Problem In order to solve this problem, the present invention uses an organic reducing agent, a chelating agent, a sulfur compound, or an amino compound as an electron-donating compound, and an organic acid metal salt as an electron-accepting compound. When irradiated with a light beam, the electron-donating compound and the electron-accepting compound react to generate a compound that absorbs the light beam.

Further, a laser beam is used as a light source for writing and reading information on an optical recording medium, and the optical recording medium contains a dye that selectively absorbs the laser beam.

Effect: With this configuration, the electron-donating compound and the electron-accepting compound react with each other when irradiated with laser light to generate a compound that absorbs the reading laser light, thereby expanding the difference in reflectance between the recorded area and the unrecorded area. Ru. Furthermore, by adding a near-infrared absorbing color material such as a cyanine dye, the absorption rate of laser light during writing can be improved, making it possible to record with small recording energy.

Example An optical recording medium formed on a transparent substrate such as glass, polycarbonate resin, or polymethyl methacrylate resin contains at least one compound selected from an organic reducing agent such as tannin or hydroquinone, a chelating agent, a sulfur compound, or an amino compound. It contains a good electron-donating compound and an electron-accepting compound made of an organic acid metal salt such as ferric stearate. By irradiating light (oscillation wavelength: 780 nm), the compound absorbs the energy of the laser beam, and the electron-donating compound and electron-accepting compound react to develop color. Furthermore, when irradiated with laser light for reading (GajJ7As-based LD, oscillation wavelength 780 nm, lower energy than laser light for writing), colored areas (pit formation areas) and The absorbance of the laser beam during reading is greater than that of the unrecorded area, and the contrast between the reflectance of the laser beam between the recorded area and the unrecorded area is large.

As the combination of the electron-donating compound and the organic metal salt as the electron-accepting compound used in the present invention, those shown in Table 1 can be used.

When creating the recording film, in addition to the combination of the electron-accepting compound and electron-donating compound described above, a near-infrared absorbing color such as a cyanine dye is added to the combination of the electron-accepting compound and electron-donating compound to increase the absorption rate of laser light during recording. Materials may be added.

This will be explained in more detail below with reference to Examples.

(Example 1) Tannin (hyrogallol tannin) 313iii.

5 parts by weight of ferric stearate and 10M parts of polyvinyl butyral as a binder were added to 100 parts of methyl cellosolve.
In order to uniformly mix the parts by weight and further selectively absorb 780 nm laser light, 0.5 parts by weight of a cyanine dye represented by 2 (1) (Japanese Photosensitive Color System NK Table 2014) was dissolved. The material was applied onto a polycarbonate substrate using a spin coating method, and
An organic recording film was prepared by drying at ℃ for 30 minutes. The film thickness was measured using a stylus-type film thickness meter manufactured by ULVAC Co., Ltd. and was found to be 0.5 μm. Furthermore, after forming a film of Au as a reflective layer on this recording film by sputtering, an ultraviolet curable resin was applied as a protective film by spin coating, and was cured by irradiating ultraviolet rays to obtain an optical recording medium. .

FIG. 1 shows the structure of the recording medium thus formed.

The obtained optical recording medium was irradiated with an oscillation wavelength of 780 nm focused to a spot diameter of 1 μmφ on the irradiation surface from the substrate side, and an output of 20 m.
W Ga AI As LD light for 250 ns
Scanning irradiation was performed to form pits.

G with an output of 1 mW is used as reproduction light on the recorded recording medium.
When the LD light of AIAs was irradiated for 200 ns and the reflection of the reproduction laser beam due to the presence or absence of pits was determined to be 28% in the recorded area and the unrecorded area, respectively.
and 71%.

(Example 2) 2 parts by weight of thiourea, 1.5 parts by weight of silver oxalate, and 6 parts by weight of polyvinyl butyral as a binder were uniformly mixed with 1,100 parts of methylcelonol, and in order to selectively absorb 780 nm laser light. , a solution of 0.6 parts by weight of a cyanine dye (Nippon Kayaku CY-9) represented by formula An organic recording thin film was prepared.The thickness of the film was 0.4 μm as measured by DIC tack.Furthermore, as in Example 1, Au was formed as a reflective layer on this dye recording film by sputtering. , apply and harden ultraviolet curable resin as a protection,
An optical recording medium was obtained.

(It) The oscillation wavelength of 780n with a spot diameter of 1 μmφ on the irradiation surface was applied to the obtained optical recording medium from the substrate side! Ill.

Output 20 mW; G a All A a system LD
Light was scanned at 300 n II to form a focus.

The oscillation wavelength of 780n is used as reproduction light on the recorded recording medium.
When we irradiated 200 nil of Ga AI As LD light with an output of 1 mW and measured the reflectance of the reproduction laser beam depending on the presence or absence of pits, it was 32% and 74% in the recorded and unrecorded areas, respectively. there were.

(Comparative Example 1) An organic recording dye film was prepared using only the near-infrared absorbing cyanine dye (1) used in Example 1.

1.5 parts by weight of cyanine dye (1) was dissolved in 100 parts by weight of methyl cellosolve and coated on a polycarbonate resin substrate by a spin coating method to form a recording film with a thickness of 0.2 μm. In the same manner as in Example 1, an optical recording medium was obtained by forming an Au film as a reflective film by sputtering, and applying and curing an ultraviolet curable film as a protective film.

As in Example 1, the obtained optical recording medium was coated with an oscillation wavelength of 78 nm with a spot diameter of 1 μmφ on the irradiation surface from the substrate side.
0nm, output 20mW GaAIAs system L
D light was scanned and irradiated for 300 ns to form pits.

The oscillation wavelength of 780n is used as reproduction light on the recorded recording medium.
200 ns of GaAiAs LD light with an output of 2 mW was measured, and the reflectance of the reproduction laser light depending on the presence or absence of pits was 45% and 62% in the recorded and unrecorded areas, respectively. there were.

(Comparative Example 2) Near-infrared absorbing cyanine dye (I[) used in Example 2
An organic recording dye film was prepared using only

1,5 parts by weight of cyanine i dye (It) was dissolved in 100 parts by weight of methyl cellosolve, and coated onto a polycarbonate resin substrate by a spin coating method to a thickness of 0.2 μm.
A recording film of m was prepared. As in Example 1, an Au film was formed as a reflective film by sputtering, and an ultraviolet-curable film was applied and cured as a protective film to obtain an optical recording medium.

As in Example 1, the obtained optical recording medium was coated with an oscillation wavelength of 78 nm with a spot diameter of 1 μmφ on the irradiation surface from the substrate side.
0 nm, output 20 mW G a A I A 5
ff=LD light was scanned and irradiated for 300 ns to form pits.

The oscillation wavelength of 780n is used as reproduction light on the recorded recording medium.
m, Ga AI As LD with output 2 mW
When light was irradiated for 200 ns and the reflectance of the reproduction laser beam was measured depending on the presence or absence of pits, it was 38% and 67% in the recorded area and the unrecorded area, respectively.

Effects of the Invention As is clear from the description of the embodiments above, according to the present invention, the organic color material used as the recording film absorbs and reacts with the laser light during writing, and a compound generated by the reaction occurs during reproduction. By using a material that absorbs laser light, it is possible to increase the contrast between the reflectance of the recorded portion and the unrecorded portion of the reproduced laser beam during reproduction.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an optical recording medium according to an embodiment of the present invention, and FIG.
The figure is a spectral diagram of reflected light before and after optical recording of the optical recording medium of Example 1. DESCRIPTION OF SYMBOLS 1... Protective film, 2... Reflective film, 3... Recording layer, 4... Substrate, 5... Tannin, 6...
...Ferric nateate, 7...Laser light absorption dye, 8...Groove.

Claims (3)

[Claims] (1) Contains either an organic reducing agent, a chelating agent, a sulfur compound, or an amino compound as an electron-donating compound, and an organic acid metal salt as an electron-accepting compound, and the electron-donating compound and the electron-accepting compound are irradiated with a light beam. An optical recording medium in which chemical compounds react to produce compounds that absorb the readout light beam. (2) The optical recording medium according to claim 1, wherein a laser beam is used as a light source for recording and reading information on the optical recording medium. (3) Claim 1 containing a dye that selectively absorbs laser light
The optical recording medium described.