JPH0829618B2 - Method of manufacturing optical recording medium - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical recording medium capable of additional recording by using a focused beam of a semiconductor laser, and more specifically, various information such as a computer external memory, an image and a sound. The present invention relates to an optical recording medium used for recording.

[Prior art]

As the above-mentioned recordable optical recording medium, a recording medium having an inorganic recording layer of a low-melting-point metal thin film such as tellurium, tellurium alloy, or bismuth alloy has begun to be put into practical use.
However, these recording media have low productivity because they require the formation of a recording layer in vacuum such as vacuum deposition and sputtering, and the recording density is high because the thermal conductivity of the recording layer is large.
There is a limit in terms of recording sensitivity, and since a toxic substance such as tellurium is used, there is particular concern when it is used for civil purposes in terms of toxicity.

In order to solve these problems, an optical recording medium having an organic dye film as a recording layer has been studied in recent years, for example, dithiol metal complex (US Pat. No. 4,465,767, US Pat. No. 4,219,826),
Polymethine dye (JP-A-58-112790), squarylium dye (JP-A-58-112792), naphthoquinone dye (JP-A-58-112792)
-112793), phthalocyanine dye (US Pat. No. 4,298,97
5), an optical recording medium having a recording layer of an organic dye having absorption at the oscillation wavelength of a semiconductor laser such as a naphthalocyanine dye (US Pat. No. 4,492,750) has been proposed. However, the media that have been proposed so far with an organic dye as a recording layer are (a) poor in durability and (b) have a low reflectance in the recording layer, so that a metal thin film, a metal oxide thin film, etc. There are drawbacks such as the need for a reflective layer made of an inorganic compound and the very poor solubility of the organic dye in (c) the solvent.

Due to such a lack of durability (b), the characteristics of the medium change over time, so special consideration must be given to the storage of the medium, or if the same track is repeatedly read, the medium will be read by the read light. However, due to changes, information may not be read correctly. This change due to the read light can be avoided by reducing the output of the read light, but this makes it easier to pick up noise due to the small amount of light, and the signal-to-noise ratio (S / N) becomes smaller. Not only that, it is difficult to make the laser emit light stably at a low output, and the load on the reading circuit becomes large, which is not preferable. Further, (b) the fact that a reflection layer made of an inorganic compound must be provided because of its low reflectance is not only complicated in the manufacturing process of the optical recording medium, but also expected to be low in thermal conductivity. There is a problem that the high recording density and recording sensitivity of the organic dye-based recording film are reduced or reduced by using an inorganic compound having a large thermal conductivity as the reflective layer. Furthermore, (c) poor solubility of organic dyes means that even if the coating method, which is the method of forming the recording layer with the highest productivity, cannot be used, or even if the recording layer can be formed by the coating method, the solvent that can be used is Due to the limitation, it could not be directly applied on a substrate of a thermoplastic resin having a poor solvent resistance against the solvent, because it may corrode it. Therefore, when a thermoplastic resin substrate is used, it is necessary to apply the dye solution through a resin having excellent solvent resistance such as an ultraviolet curable resin, which complicates the process and reduces the productivity and cost. It was unfavorable.

[Basic idea]

The present inventors have conducted extensive studies to improve the above-mentioned drawbacks of an optical recording medium having an organic dye film as a recording layer. As a result, a specific amount of a specific phthalocyanine dye was used for the recording layer, and the recording layer was used. By controlling the thickness of the film to an appropriate thickness, the recording layer itself has a durability which cannot be realized in an optical recording medium using a conventional organic dye, and the recording layer itself has a function of a reflection layer. As described above, the present invention has been completed by finding that an optical recording medium can be formed without the need to separately provide a reflective layer made of an inorganic compound.

[Disclosure of Invention]

That is, the present invention provides an optical recording medium for recording and reproducing a signal by using reflected light, and a transparent substrate and the following general formula (1). (In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent a linear or branched alkyl group having 5 to 12 carbon atoms, and these groups may be the same or different at the same time. A composition containing a phthalocyanine dye (100 to 80 parts by weight) and a binder of 0 to 20 parts by weight is dissolved in an organic solvent having a solubility parameter of 8.6 or less. Inorganic compound characterized in that the above solution is brought into contact with a transparent resin substrate to form a recording layer having a film thickness of 50 to 400 nm containing the phthalocyanine dye represented by the general formula (1) on the resin substrate. Provided is a method of manufacturing an optical recording medium capable of recording and reading a signal without having a reflective layer made of.

In the present invention, it is preferable to write or read a signal with a light beam that passes through a transparent resin substrate because it is less likely to be affected by dust or scratches. Therefore, the transparent resin substrate used in the present invention,
It is desirable that the transmittance of light for writing and reading signals is 85% or more and that the optical anisotropy is small. Examples thereof include substrates made of acrylic resin, polycarbonate resin, allyl resin, polyester resin, polyamide resin, vinyl chloride resin, polyvinyl ester resin, epoxy resin, polyolefin resin, and the like. Of these, acrylic resin, polycarbonate resin, polyester resin, and polyolefin resin substrates are particularly preferable from the viewpoints of deformation of the substrate, mechanical strength, easiness of providing guide grooves and pre-formatted signals, and economical efficiency.

The shape of these transparent resin substrates may be plate-like or film-like, and may be circular or card-like. Of course, the surface may be provided with a guide groove for indicating a recording position or unevenness for address signals. Such guide grooves, address signals, etc. are given when making a substrate by injection molding or casting, or by applying an ultraviolet curable resin or the like on the substrate and overlapping it with a stamper to perform ultraviolet exposure. Can also be given.

In the present invention, on the substrate, the following general formula (1) (In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent a linear or branched alkyl group having 5 to 12 carbon atoms, and these groups may be the same or different at the same time. A metal and a metal oxide or a halide thereof are provided) to provide a recording layer containing a phthalocyanine dye.

The general formula (1) used for the recording layer in the present invention
Specific examples of the alkyl substituent represented by R ₁ , R ₂ , R ₃ and R ₄ in the phthalocyanine dye represented by
-Amyl, iso-amyl, sec-amyl, tert-amyl,
n-hexyl, iso-hexyl, 1-methyl-1-ethylpropyl, 1,1-dimethylbutyl, n-heptyl, ter
t peptyl, octyl, 2-ethylhexyl, nonyl,
Examples include decyl and dodecyl. These alkyl substituents may be bonded to either the 3-position or 4-position of the benzene nucleus of phthalocyanine, or may be a mixture. On the other hand, specific examples of M in the phthalocyanine dye represented by the general formula (1) are Cu, Ni, Mg, Pb,
V, Co, Ti, Nb, Al, Sn, In, Fe, Cr, Ge, Mn, Mo, G
Examples thereof include metals such as a, Tl, Ca, Sr, Ba, Pd, Sb, Ta, Te and Se, and oxides, chlorides, bromides and iodides of these metals.

These metals, metal oxides, chlorides, bromides or iodides are usually divalent, but may be a mixture of monovalent and trivalent. When the number of carbon atoms of the alkyl substituent in the phthalocyanine dye of the general formula (1) is 4 or less, the solubility in an organic solvent is poor and it becomes difficult to form a recording layer by coating, which is not preferable. From the viewpoint of solubility in this organic solvent, an alkyl group having 6 or more carbon atoms is more preferable. On the other hand, when the number of carbon atoms exceeds 12, the reflectance of the recording layer containing the carbon atoms becomes small, which is not preferable. From the viewpoint of reflectance and absorbance, M in the phthalocyanine dye is a metal selected from the elements of groups II, III, IV, V, VI and VIII of the periodic table, or an oxide or chloride, bromide or iodide of a metal. Is particularly preferable.

The above phthalocyanine dye used in the present invention can be easily synthesized according to a known method described in "Theoretical Manufacturing Dye Chemistry" by Yutaka Hosoda (Gihodo Publishing) and the like.

In the production of the optical recording medium of the present invention, the recording layer is formed on a transparent resin substrate by, for example, bringing the dye solution containing the phthalocyanine dye and an organic solvent into contact with the substrate to fix the dye on the substrate. , More specifically,
For example, after the dye solution is made to flow down on the substrate or the substrate surface is brought into contact with the liquid surface of the dye solution and then pulled up, the excess liquid is removed while rotating the substrate, or the dye is produced while rotating the substrate. There is a method of allowing the liquid to flow down onto the substrate. If necessary, forced drying may be performed thereafter. The organic solvent used at this time may be a usual solvent that dissolves a phthalocyanine dye, such as aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; ketones such as methylethylketone, methylisobutylketone, cyclohexanone, and acetylacetone; ethyl acetate, Butyl acetate, amyl acetate, cellosolve, methyl cellosolve, butyl cellosolve, cellosolve acetate, diglyme, chloroform, carbon tetrachloride,
Aliphatic hydrocarbons such as methylene chloride, methylchloroform, trichlene, dimethylformamide, pentane, hexane, peptane, octane, nonane, decane, hexene, heptene, octene; cyclohexane, cyclohexene, methylcyclohexane, methylcyclohexene,
Alicyclic hydrocarbons such as ethylcyclohexane; chain ethers such as diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether and the like can be mentioned. In selecting the solvent, it is naturally preferable to use a solvent that does not damage the guide groove on the transparent resin substrate in addition to the solubility of the dye. Among the above-mentioned solvents, carbon tetrachloride and aliphatic hydrocarbons are preferable. Solvents having a solubility parameter of 8.6 or less, such as alicyclic hydrocarbon and chain ether, are particularly preferable.

The concentration of the dye solution in the present invention varies depending on the type of solvent and the coating method, but is usually 0.1 to 10% by weight, preferably
It is 0.3 to 5% by weight. At this time, a soluble resin such as nitrocellulose, ethyl cellulose, or acrylic resin, or an additive such as a leveling agent or an antifoaming agent may be added to the dye solution as a binder for the dye. However, the addition of too much resin component or additive tends to lower the reflectance of the recording layer, and the addition amount thereof is preferably 20% by weight or less, more preferably 10% by weight or less in the recording layer.

The phthalocyanine dye in the recording layer is 100 to 80% by weight.
Is. If it is less than 80% by weight, that is, if the amount of the resin binder is larger than this, the reflectance of the recording layer is significantly lowered.

Further, the dye solution may be mixed with another dye and used. Known dyes that can be mixed and used, for example, aromatic or unsaturated aliphatic diamine-based metal complexes, aromatic or unsaturated aliphatic dithiol-based metal complexes, naphthalocyanine-based complexes, squalium-based dyes, naphthoquinone-based complexes, Examples thereof include anthraquinone dyes and polymethine dyes.

In the optical recording medium of the present invention, it is preferable to record and reproduce a signal by a light beam (light beam emitted from the substrate side) through the transparent substrate as described above. If the film thickness is too large, the writing light is absorbed as it passes through the thick recording layer and is considerably attenuated, and does not reach the recording layer surface (the surface in contact with air) sufficiently. Therefore, the amount of light on this surface is insufficient and the temperature rise is insufficient, so that it is not possible to satisfactorily form the unevenness corresponding to the signal. As a result, the sensitivity is lowered, and even if it is possible to record somehow, the S / N (signal to noise ratio) value at the time of reading the signal is too small to be put to practical use.

On the other hand, when the film thickness of the recording layer is too thin, as will be described later, the reflectance of the recording layer cannot be sufficiently obtained due to the interference of light, and thus a large S / N value cannot be obtained.

Therefore, it is necessary to form a recording layer having an appropriate thickness, but the thickness of the recording layer in the optical recording medium of the present invention is preferably 50 to 400 nm, more preferably 60 to 250 nm, as a rough approximation. .

Although there are various methods for measuring the film thickness, and obtaining an accurate measurement value is quite difficult, it is preferable to use the value measured using an ellipsometer. Although it is particularly difficult to measure the film thickness when the guide groove is provided on the substrate, the film thickness when the dye is fixed on the same substrate having no guide groove or other irregularities can be used as a substitute.

The most characteristic feature of the present invention is that the recording layer thus formed has a fairly high reflectance by itself, and therefore the recording layer itself simultaneously functions as a reflective layer. It also serves as a function.

Therefore, the optical recording medium of the present invention does not require a laser beam for recording or reading a signal, as in the conventional case, particularly when a reflective layer made of an inorganic compound such as a metal thin film, a metal oxide or a metal alloy thin film is not provided. The focus control and the tracking control of the signal writing position are possible.

In order to write a signal in the optical recording medium of the present invention, the recording layer is focused and irradiated with a laser beam. The dye in the recording layer in the irradiated portion absorbs laser light to generate heat, so that the recording layer is altered and unevenness is formed to reduce the reflectance, thereby performing writing. A signal is read out by detecting the change in the reflectance with a finer laser beam light. Generally, if the change in the reflectance is small, the signal-to-noise ratio (S / N) is small, which is not preferable. In order to obtain a large S / N value, the original reflectance through the substrate is at least 10% or more, preferably 15% or more before the signal is written. This 10%, preferably 15
A reflectance of at least% can be easily achieved by using the dye of the present invention and appropriately selecting the film thickness of the recording layer. However, the reflectance changes depending on the film thickness due to interference of reflected light from the front and back of the recording layer.

In this case, the reflectance is measured using a light source with a wavelength of 800 ± 50 nm, and the recording layer is fixed on a transparent substrate that does not have irregularities such as guide grooves, and a spectrophotometer equipped with a 5 ° specular reflection accessory device. Is measured through a transparent substrate, and the reflectance in the present invention means the value thus measured.

In order to put the optical recording medium of the present invention into practical use, S / N
An antireflection layer is provided to improve the value, an ultraviolet curable resin is applied on the recording layer for the purpose of protecting the recording layer, a protective sheet is attached to the recording layer surface, and the recording layer surface is inside. Known means such as laminating two sheets may be used together. It is desirable that an air gear gap is provided on the recording layer when the layers are laminated.

 Hereinafter, the present invention will be described more specifically with reference to Examples.

Example 1. (1) A liquid consisting of 1 part by weight of tetra-4-tert-octyl-phthalocyanine vanadyl dye and 99 parts by weight of carbon tetrachloride was dropped on the center of an acrylic resin plate having a thickness of 1.2 mm and a diameter of 120 mm. The acrylic resin plate was rotated at a speed of 1500 rpm for 15 seconds. Next, this acrylic resin plate in the atmosphere of 40 ℃
After drying for 10 minutes, the recording layer was fixed on the acrylic resin plate. The thickness of this recording layer was 100 nm as measured by an ellipsometer. The reflectance of light having a wavelength of 790 nm through the acrylic resin plate was 22%.

(2) A semiconductor laser having an output of 3 mW on the substrate surface with an oscillation wavelength of 790 nm is placed on the turntable with the recording layer facing upwards on a turntable and rotated at a speed of 200 rpm. Using the equipped optical head, a pulse signal of 650 KHZ was recorded while controlling the laser beam from the lower side of the optical recording medium to focus on the recording layer through an acrylic resin plate. Next, using the same device, the output of the semiconductor laser was set to 0.3 mW on the substrate surface and the recorded signal was reproduced in the same manner. The signal-to-noise ratio (S / N) at this time was 55 dB, and writing and reading of extremely good signals were possible.

(3) In order to examine the durability of this optical recording medium, a temperature of 60 ° C. and 90 ° C.
After left in the atmosphere of% RH for 4 months, the signal is recorded on the unrecorded area by the same method as above, and the signal recorded before the durability test and the signal recorded after the durability test are reproduced respectively. S / N of 53 and 54 dB were obtained, and the deterioration by the durability test was small.

(4) Next, the shape of the pits of the signal recording portion after the durability test was observed with a scanning electron microscope. The pits recorded before the durability test and the pits recorded after the durability test had almost the same shape. The pits around the pits, which are generated in an optical recording medium having an inorganic thin film such as a Te-based recording layer as a recording layer and cause noise, were hardly seen, and the pit shape was very clean.

Example 2 Using the carbon tetrachloride solution of the phthalocyanine dye having an alkyl group and M shown in Table 1, an optical recording medium was prepared in the same manner as in Example 1 and the reflectance and S / N were examined.

 The results are summarized in Table 1.

Example 3 A polycarbonate resin plate having a thickness of 1.2 mm, a diameter of 130 mm, and spiral recording guide grooves (depth 0.07 μm, width 0.5 μm, pitch 1.6 μm), and 3 parts by weight of tetra-4-tert-octyl-phthalocyanine vanadyl. An optical recording medium was prepared in the same manner as in Example 1 by using a 8% octane solution. The thickness of the recording layer of this optical recording medium was 90 nm as a result of observing the cross section of the medium with an electron microscope.

Next, using this optical recording medium, the S / N measurement durability test by writing and reading signals and observing the pits were performed in the same manner as in Example 1. The obtained results are S / N = 52dB immediately after recording, S / N = 51dB at the time of reproduction after the durability test,
S / N = 51 dB at the time of re-recording after the durability test. Almost no swelling was observed around the pit.

〔The invention's effect〕

As described above, in the optical recording medium of the present invention, since the recording layer itself has sufficient reflectance, it is possible to write and read signals without providing a reflective layer such as a metal thin film or a metal oxide thin film, and Since the reflectance change is also large, a large S /
N ratio is obtained. The optical recording medium of the present invention is stable to heat and humidity and can be used for a long period of time.

Furthermore, the fact that there is no swelling around the pits of the recording section confirms that a large S / N can be obtained, and at the same time, the possibility of improving the recording density is shown.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Shigeru Takahara 4-5-45 Tai, Kamakura City, Kanagawa Prefecture (72) Masashi Koike 4-5-45 Tai, Kamakura City, Kanagawa Prefecture (56) Reference JP-A-59 -67093 (JP, A) JP-A-56-130742 (JP, A) JP-A-60-23451 (JP, A) JP-A-60-184565 (JP, A) JP-A-59-67093 (JP, A) ) JP-A-58-56892 (JP, A)

Claims (2)

[Claims] 1. A general formula (1) (In the formula, R ₁ , R ₂ , R ₃ and R ₄ represent a linear or branched alkyl group having 5 to 12 carbon atoms, and these groups may be the same or different at the same time. M represents a metal and an oxide or halide of the metal.) A composition containing 100 to 80 parts by weight of a phthalocyanine dye and 0 to 20 parts by weight of a binder is dissolved in an organic solvent having a solubility parameter of 8.6 or less. Inorganic compound characterized in that the above solution is brought into contact with a transparent resin substrate to form a recording layer having a film thickness of 50 to 400 nm containing the phthalocyanine dye represented by the general formula (1) on the resin substrate. A method of manufacturing an optical recording medium capable of recording and reading a signal without having a reflective layer made of. 2. In the phthalocyanine dye represented by the general formula (1), M is group II, group III, group IV or group V of the periodic table.
The method for producing an optical recording medium according to claim 1, wherein the optical recording medium is a metal, an oxide or a halide of a metal selected from Group, VI, and VIII elements.