JPH0567437B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to an optical information recording medium, and in particular, information is recorded by drilling minute pits in a recording layer or forming minute altered points using a laser beam. So-called heat mode DRAW
This relates to recording media for (Prior Art) The optical information recording method has the advantage that there is no wear and tear deterioration because the writing head or reading head and the recording medium are not in contact with each other, and various recording media have been developed to date. Among such optical recording media, heat mode optical recording media are being actively developed because they do not require image processing in a darkroom. This heat mode optical recording medium is an optical recording medium that uses recording light as heat. Usually, a part of the medium is melted and evaporated using recording light such as a laser.
Writing is performed by forming small holes called pits, and reading is performed by reading out these pits and detecting them with light. In such a pit-type medium, a recording layer containing a self-oxidizing compound such as nitrocellulose and a light absorber is provided on a substrate, and the recording layer is formed by decomposing the nitrocellulose or the like. Among the above light absorbers, cyanine dyes are typically used. However, when a cyanine dye is contained in the recording layer, the stability against heat and light is low, and the storage stability is poor. For example, if you store it in a state where it is exposed to indoor light, you will not be able to write to it. Compared to cyanine dye systems, those using tetrahydrocholine or cocol complexes as light absorbers have significantly improved durability of so-called recording media (Japanese Patent Application Laid-Open No. 197088/1988), but the light resistance is However, it has not yet reached a practical level, and repeated irradiation with readout light causes so-called reproduction deterioration, resulting in a deterioration of the S/N ratio. In addition, especially with systems in which the recording layer is formed from a dye and a thermoplastic resin, once formed pits can be erased with erasing light or heat and rewritten. Characteristics deteriorate. Furthermore, the writing sensitivity and reading S/N ratio are also insufficient. Generally, the recording layer contains a self-oxidizing compound or a thermoplastic resin together with the above-mentioned dye,
Pits are formed by burning self-oxidizing compounds, melting thermoplastic resins, and forming deformed spots. Further, these compounds and resins serve to improve the physical properties of the recording film. Nitrocellulose has conventionally been generally used as the self-acidic compound. Nitrocellulose, which is used in optical information recording media, is insoluble in alcohols, so the recording media coating is created by dissolving it in an organic solvent other than alcohol, applying it to the substrate, and then removing the solvent by evaporation. It is deposited and formed on the substrate. However, the substrate is polymethyl methacrylate,
In the case of molded plastic substrates such as polycarbonate, the solvents for nitrocellulose, i.e. ketones, esters, and halogenated hydrocarbons, which are generally known as good solvents for dyes, can easily dissolve molded plastic substrates. It will dissolve. For this reason, for example, in the case of optical recording disks, the grooves of the plastic disk substrate are also dissolved, making it impossible to apply a recording film with the grooves completely intact. It was hot. In addition, in the case of low-viscosity nitrocellulose that dissolves in alcohols, the solution viscosity is low, so once the pigment is dispersed in the solution, it immediately settles, so the pigment is in a good dispersion state. It was not possible to obtain a coating film, that is, a recording medium. On the other hand, when an alcohol-soluble dye is used, a coating film with good appearance can be obtained, but this coating film lacks toughness and therefore has a defect of poor durability. According to experiments conducted by the present inventors, although dye-nitrocellulose coatings can form good pits, it is difficult to form good pits with pigment-nitrocellulose coatings. - It was not possible to form satisfactory pits with nitrocellulose. (Object of the Invention) Therefore, an object of the present invention is to provide a well-balanced heat mode optical information recording medium with excellent storage stability and high writing and reading sensitivity or S/N ratio. . As a result of intensive research into this objective, the present inventors have discovered a combination of celluloid and at least one selected from pigments and dyes as a light absorber that achieves this objective.
The present invention has now been accomplished. That is, the optical information recording medium according to the present invention has a base material and a recording layer provided on the base material, and the recording layer is irradiated with a laser beam to burn or change the quality of the recording layer to create recording points. An optical information recording medium in which information is recorded by forming an optical information recording medium is characterized in that the recording layer is composed of celluloid and a light absorbing agent. Any known light absorbing agent can be used, but pigments are particularly preferred;
It is preferable to have an absorption wavelength in the range of 0.6 to 0.8 mm. Generally well-known pigments include inorganic pigments such as green, blue, purple, and series colors, such as chrome green, chromium oxide, viridian, deep blue, ultramarine, cobalt blue, manganese violet, cobalt violet, etc. be done. Examples of organic pigments include the phthalocyanine-metal matrix group. These pigments can form pits by absorbing the recording light and converting the light into heat when irradiated with the recording light. The base material can be made of any known material, and may be a metal plate such as aluminum or stainless steel, a glass plate, a plastic plate such as polymethyl methacrylate or polycarbonate, or even a tape made of polyester film. good. A feature of the present invention is that the recording layer is composed of celluloid in which a light absorbing agent is dispersed. First, the difference between nitrocellulose and celluloid, which are conventionally known as self-oxidizing compounds, will be explained.
Celluloid is made from nitrocellulose, but the properties of the two are very different, and they are generally treated as completely different things. That is, nitrocellulose generally does not dissolve in alcohols, and esters are preferred solvents. Alcohol, which is a non-solvent, is sometimes added to the solvent, but this is to improve the properties of the coating film, and the main component of the solvent is esters. On the other hand, celluloid is generally made from nitrocellulose, which has a nitrogen content (N%) of around 11, by removing water to 3% or less by alcohol substitution. The dissolved solution was added and aged, and the resulting lumps were mixed in a kneader (about 3 hours) and filtered. Unlike ordinary nitrocellulose, this celluloid dissolves in alcohol. Generally, celluloid is a mixture of nitrocellulose and camphor, and camphor is said to act as a plasticizer in celluloid. However, the viscosity of a solution of celluloid made from nitrocellulose with the same viscosity in alcohol at the same concentration is significantly different from the viscosity of a solution when the same amount of nitrocellulose and camphor used for celluloid are dissolved in alcohol; is much more expensive. As is clear from the above explanation, the celluloid used in the present invention is known in the art (for example, Japanese Patent Application Laid-Open No. 58-166548
It is easy to understand that the composition and effects are completely different from nitrocellulose (No.). On the other hand, when plastics such as polymethyl methacrylate and polycarbonate are used as substrates for optical information recording media, solvents other than alcohols such as ketones, esters, aromatic hydrocarbons, halogenated hydrocarbons, and organic acids may be used. The board will melt. Therefore, when using a plastic substrate on which track grooves (groups) with a depth of about 700 A. are formed, if a solvent other than alcohol is used, the groups will dissolve, making it impossible to put it to practical use. On the other hand, when the celluloid according to the present invention is used, since the celluloid dissolves in alcohol, even if it is applied onto a plastic substrate such as polymethyl methacrylate or polycarbonate, it will not dissolve the groups on the substrate. It is possible to leave the group completely intact and apply it. Furthermore, celluloid-alcohol solutions have a much higher viscosity than nitrocellulose solutions even at low concentrations; for example, at a concentration of 5%, celluloid has a viscosity of 110 cps/20°C, while nitrocellulose has a viscosity of 110 cps/20°C.
14cps/20℃. Therefore, it is easier to disperse pigments in a celluloid solution than in a nitrocellulose solution, and even inorganic pigments dispersed in the solution do not easily settle.
Therefore, it is easy to apply this solution to obtain a coating film with uniform pigment dispersion. Furthermore, even when irradiated with light to form pits, pigment-celluloid systems can form better pits than pigment-nitrocellulose systems, and this is especially true for inorganic pigment systems. It is. Celluloid and pigment are usually used in a weight ratio, and can be selected from a wide range of 1:0.1 to 100 so as to obtain desired transmittance and reflectance as described below. The above celluloid solution is coated using a well-known spin coater.
It can be formed on the substrate by bar coater, dip coating, or any other method, and the film thickness is generally
It may be about 0.03 to 2 μm. In addition, the celluloid solution may contain other polymers or oligomers, various plasticizers, surfactants, antistatic agents, lubricants, flame retardants, stabilizers, dispersants, and the like. There are two methods for writing or reading optical information recording media: a method that uses reflected light and a method that uses transmitted light. In the case of the method that uses reflected light, there is a surface reading method that applies light from the recording layer side and a method that uses light from the substrate side. There is a back-side reading method in which the light is reflected, but the present invention can be applied to either method by appropriately selecting the substrate and reflective film. In addition, a protective layer may be provided as necessary. The recording layer made of the celluloid-light absorbing material of the present invention can also be used by laminating it with a conventionally known thin film layer of an easily evaporable metal such as Te. When the substrate is made of plastic, it is preferable to interpose a metal layer such as aluminum between the substrate and the recording layer to increase the reflectance. Further, in the case of a back reading method, it is preferable to form a gas permeable reflective layer on the outer surface of the recording layer on the side opposite to the substrate. This gas-permeable reflective layer can be formed by vapor deposition of aluminum,
The aluminum vapor-deposited film with a thickness of about 100 Å is translucent and allows H ₂ O, CO, CO ₂ , NO, and NO ₂ gases to pass through it. The recording layer burns incompletely and becomes black, but gas is released through the thin film. However, there is almost no apparent shape deformation in the laser irradiated area. Celluloid that has been altered (carbonized) in this way has excellent durability, especially stability against light and heat. Furthermore, the present invention can be used when forming a recording layer on both sides of a single substrate so that both sides serve as recording surfaces, or after forming a recording layer on only one side of the substrate, two layers are formed with the recording layer inside.
It can be applied to any case where sheets are pasted together. Hereinafter, the present invention will be explained using special examples.
The present invention is not limited to this. Example 1 A solution (A) having the following composition was prepared, and it was applied on an aluminum disk substrate 1 with a diameter of 5 inches to a thickness of a coating film 2.
It was spin-coated to a thickness of 0.2 μm and immediately dried at 60° C. for 10 minutes (Figure 1). The inorganic pigment of the light absorber, dark blue, is KFe [Fe(CN) ₆ ]. Solution (A) Celluloid (No. 5.11 manufactured by Daicel) Navy blue paste (No. SB manufactured by Daicel) Methyl alcohol n-butyl alcohol 0.2 g 1.0 g 60.0 g 40.0 g Specular reflectance of the recording medium thus obtained at an incident angle of 60° was 44.2%. Furthermore, when the light absorption characteristics at each wavelength of a recording medium obtained by coating this solution (A) on a polycarbonate substrate were measured, the light transmission characteristics as shown in FIG. 5 were obtained. 600~800nm
A strong optical absorption band can be seen. This has a wavelength of 633nm,
When the pulsed light (pulse width 1 μsec) of a He-Ne laser with an output of 10 mw was focused on a spot of _1.6〓〓n and irradiated, a pit 5 of _1〓〓n was obtained. For the medium coated on the aluminum substrate created in this way, while rotating it at 1800 rpm, semiconductor laser recording light (wavelength, 830 nm) is focused to _1〓〓n (concentrating part It was irradiated in the form of a pulse train at a frequency of 1MHz (output 10mW) and a frequency of 1MHz. As a result, track-shaped pits were formed in the medium. The shape of the pit 5 was good as shown in FIG. After this, semiconductor laser light is used as readout light,
(wavelength 830nm) is focused to 1μmφ (condensing section
1 mW), this is irradiated as a continuous light, the pit-formed substrate is rotated at 1800 rpm, and the pits and non-pits are separated.
The S/N ratio was measured using specularly reflected light from the pit.
Furthermore, readout light was continuously irradiated onto the medium after the pits were formed for 5 minutes to measure reproduction deterioration of the S/N ratio. Separately, this medium was left under sunlight for one month, after which writing was performed, the S/N ratio was measured, and the light resistance was evaluated. Also, this media
After leaving it at 150℃ for 5 minutes, write on it.
The heat resistance was evaluated by measuring the S/N ratio. These results are shown in Table 1. Comparative Example 1 A solution (B) having the following composition was prepared and treated in the same manner as in Example 1. Solution (B) Nitrocellulose (contains 30% IPA, Daicel SS1/8) Prussian paste (SB manufactured by Daicel) Methyl alcohol n-butyl alcohol 0.3g 1.0g 60.0g 40.0g The shape of the resulting pit 6 is shown in Figure 2. As you can see, the center of the pit was the aluminum surface, the periphery was the painted surface, and the area around it was raised. The 60° specular reflectance of the recording medium was 49.0%. The performance of Comparative Example 1 was measured using the same method as Example 1, and the results are shown in Table 1.

[Table] Example 2 Using a phthalocyanine copper derivative (oil-soluble dye) with the following structural formula () as a light absorber, a solution (C) with the following composition was prepared, and this was applied to a 5-inch diameter, 300 Å
An optical disk substrate 10 made of polycarbonate resin is coated with a thin aluminum film 14 of 14 by vacuum evaporation.
The coating film 12 was spin-coated on top to a thickness of 0.2 μm, and immediately dried at 60° C. for 10 minutes.

[C] The substituent is 3-position solution (C) celluloid (Daicel No. 5.11) Phthalocyanine copper derivative methyl alcohol n-butyl alcohol 0.2g 1.0g 60.0g 40.0g The specular reflectance of the recording medium thus obtained was measured to be 49.0 It was %. Furthermore, when the light absorption characteristics at each wavelength of a recording medium obtained by coating this solution (C) on a polycarbonate substrate were measured, the light transmission characteristics as shown in FIG. 6 were obtained. A strong optical absorption band is seen between 600 and 700 nm. This has a wavelength of 633nm and output
10mW He−Ne− laser pulse light (pulse width
When the light was focused and irradiated onto a spot of _1.6〓〓n (0.5μsec), a well-shaped pit of _1〓〓n was formed. Observation was made using a scanning electron microscope. A sectional view thereof is shown in FIG. For the media created in this way, use this
While rotating at 1800 rpm, He-Ne laser recording light (633 nm) is focused at 1〓〓 _n (focusing section output 10 mW).
Irradiation was performed in the form of a pulse train at a frequency of 1MHz. As a result, pits were formed in the medium in the form of tracks. After that, as readout light, a He-Ne laser (633 nm) is focused to _1〓〓n (condensing part 1mW), and this is irradiated as continuous light to illuminate the pit-formed substrate.
It was rotated at 1800 rpm and the S/N ratio was measured using specularly reflected light from pits and non-pits. Second result
Shown in the table. In addition, it was measured using the same method as in Example 1.
Table 2 also shows the S/N ratio of reproduction deterioration, light resistance, and heat resistance.

[Table] Example 3 As a light absorber, azine-based oil-soluble dye (Oriont
Prepare a solution (D) with the following composition using Spirit Black SB [Orient], bluish black), and apply it to a polycarbonate resin optical disk substrate with a diameter of 5 inches and a pregroove of 700 Å. The coating film 12 was applied by spin coating onto the coating film 10 so that the thickness was 0.2 μm, and immediately dried at 60° C. for 10 minutes. Solution (D) Celluloid (No. 5.11 manufactured by Daicel) Methanol n-butanol BlackSB 0.5g 60.0g 40.0g 2.0g Next, on this coating film 12, a film thickness of 200
Al (aluminum) 14 was vacuum-deposited to a thickness of Å. The specular reflectance of the recording medium thus obtained was 38.4% when measured from the substrate side. Also this solution
When the light absorption characteristics at each wavelength of the recording medium obtained by coating (D) on another polycarbonate substrate were measured, the light transmission characteristics as shown in FIG. 7 were obtained. A gentle optical absorption band is seen between 600 and 700 nm. This is He− with a wavelength of 633 nm and an output of 10 mW.
Ne laser pulse light (pulse width 0.5μsec)
When the light was focused on a spot of _1.6〓〓n and irradiated from the back side (polycarbonate substrate side), a well-shaped pit with a black color of _1〓〓n was formed. The cross-sectional view observed with a scanning electron microscope is shown in FIG. For the media created in this way, use this
After rotating at 1800 rpm, the He-Ne laser recording light (633 nm) is focused at 1〓〓 _n ,
It was irradiated in a pulse train from the back (substrate) side at a frequency of 1MHz (10mW). As a result, pits were formed in the medium in the form of tracks. After that, as readout light, a He-Ne laser (633 nm) is focused at 1〓〓 _n (focusing section 1mW), and this is converted into continuous light.
Irradiation was performed from the back (substrate) side, the pit-formed substrate was rotated at 1800 rpm, and the S/N ratio was measured using specularly reflected light from pits and non-pits. 3rd result
Shown in the table. In addition, the S/N ratio of playback deterioration, light resistance, and heat resistance measured using the same method as in Example 1 was also the third highest.
Shown in the table.

【table】 [Brief explanation of the drawing]

FIG. 1 is a conceptual cross-sectional view of an embodiment in which a recording layer according to the present invention is formed on an aluminum plate, and the pit shape is as seen with a microscope. FIG. 2 is a conceptual cross-sectional view similar to FIG. 1 of a comparative example using conventionally known nitrocellulose. FIG. 3 is a conceptual cross-sectional view of an embodiment in which a recording layer according to the present invention is formed on a plastic plate with an aluminum reflective layer interposed therebetween. FIG. 4 is a conceptual cross-sectional view of an embodiment in which the present invention is applied to a rear readout system, and this figure shows a case where recording points are formed on grooves formed on a substrate. 5 to 7 are diagrams depicting the light transmittance of the optical recording medium according to the present invention versus wavelength. Symbols in the figure: 1, 10...Substrate, 2, 12...Recording layer, 14...Reflection layer, 15...Recording point.

Claims (1)

[Claims] 1. A device comprising a base material and a recording layer provided on the base material, and irradiating the recording layer with a laser beam to burn or change the quality of the recording layer to form recording points. What is claimed is: 1. An optical information recording medium on which information is recorded using a method, wherein the recording layer is composed of celluloid and a light absorbing agent. 2. The optical information recording medium according to claim 1, wherein the light absorber is at least one selected from the group consisting of pigments and dyes. 3. The optical information recording medium according to claim 1, wherein the base material is made of a plastic material. 4. The optical information recording medium according to claim 1, wherein a metal layer is interposed between the recording layer and the substrate. 5. The optical information recording medium according to claim 4, wherein the metal layer is a thin film of aluminum. 6. The optical information recording medium according to claim 1, wherein a metal layer is formed on the outer surface of the recording layer on the side opposite to the substrate. 7. The optical information recording medium according to claim 6, wherein the metal layer is a thin film of aluminum.