JPH022066A - Optical data recording medium and recording method - Google Patents

Abstract

PURPOSE:To obtain an optical data recording medium capable of being formed into a single plate structure and made thin while keeping high sensitivity and a high C/N ratio by forming a recording layer from a dye film having a spectral reflectivity peak in the vicinity of a recording/regenerating wavelength and presribing the thickness of said film to one maximizing the film thickness dependence of reflectivity in the recording/regenerating wavelength. CONSTITUTION:The recording/regeneration of data are performed using light having a wavelength in the vicinity of one wherein the spectral reflectivity of a dye film becomes peak. Therefore, a dye showing the peak of spectral reflectivity in the vicinity of a recording/regenerating wavelength is used in a recording layer and the thickness of the recording layer is prescribed so that the film thickness dependence of reflectivity becomes max. in the recording/regenerating wavelength. The recording medium using this dye film has high reflectivity and low absorption. When the recording medium having the org. dye film having the above mentioned optical characteristics and the thickness as the recording layer is used, the absorption of light becomes little and the sudden decomposition or sublimation of the dye film becomes hard to generate but the interference structure of the film is destructed by the slight deformation of the dye film and reflectivity is lowered to a large extent to make it possible to perform recording.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved optical information recording medium and recording method that can be used in the optical recording field.

[Problems to be solved by conventional techniques and inventions] In recent years,
Optical information recording media such as optical disks are attracting attention from the viewpoint of high-density storage, non-contact recording and playback, and ease of access.
It is applied to various information devices such as backup memory, still image/video files, etc.

The following types of optical information recording media have been proposed so far:

(a) A low melting point metal thin film is used for the recording layer. (b) A two-layer structure recording layer consisting of a reflective film and an organic light absorption layer is used. (c) A high reflectance organic dye film is used for the recording layer. The recording medium of type (a) above has a recording layer composed of a thin film mainly composed of a low melting point metal such as Te, and utilizes a perforation type and a change in reflectance due to a crystal-amorphous phase transition. There is a phase change type. This type of recording medium has disadvantages in that storage stability is poor, the perforated type has low resolution and recording density cannot be increased, and the phase change type has difficult manufacturing conditions and high cost.

In the recording medium of type (b) above, an organic light absorbing layer is provided by coating on a metal reflective film, and information is recorded by irradiating the organic light absorbing layer with a laser beam to create depressions. This type of recording medium is difficult to manufacture because the recording layer has a two-layer structure in which an organic absorption layer is laminated on a metal reflective film, and since it has a reflective layer, recording and reproduction from the substrate side is difficult. It has the disadvantage of being ugly.

The recording medium of type (c) above has an organic dye thin film with high reflectance provided on a substrate as a recording layer. Organic dye thin films have high melting points, high decomposition temperatures, and low thermal conductivity, so they can be expected to have high sensitivity, high C/N, and high reliability.Also, because film formation can be done by coating, mass production is good and costs are low. There are advantages such as expected. However, this type of recording medium has poor sensitivity unless it has an air sandwich structure.
C/N drops significantly. For this reason, it is difficult to reduce the thickness of the medium, making it difficult to create a single-plate structure or apply it to optical floppies. This also applies to the perforated recording medium of type (a) above and the recording medium of type (b) above.

On the other hand, the optical disk file has the initial cylinder 4'f = 30 a
A mold using optical disks of n was commercialized, and then 20 years later.
■ type, 13α type and gradually become smaller in diameter, and eventually 90
There are signs that it will shift to a type. This is an attempt to make drives smaller and expand the market for personal use. Despite this trend toward miniaturization, the conventional air sandwich structure has been designed to reduce the thickness of the disk substrate by 1
．． In the case of 2 mm, it is very difficult to reduce the overall thickness to 3 m or less.

This is because conventional hole-punched optical discs basically have a substrate/
It has a recording layer/air structure, and the air is a heat insulator.
In addition to increasing thermal efficiency, it does not suppress evaporation, decomposition, or scattering of the recording layer during recording, resulting in high sensitivity and high C.
We were able to maintain Ha.

If a protective layer or the like is provided in place of this air layer, the sensitivity and C/N will immediately drop.

In view of the above-mentioned problems of the prior art, the present invention provides high sensitivity, high C.
It is an object of the present invention to provide an optical information recording medium that can be made into a single-layer structure and thinner while maintaining the characteristics of the present invention.

[Means to solve the problem]

In order to achieve the above object, according to the present invention, an optical information recording layer is provided on a substrate directly or via an undercoat layer, and a layer containing an organic dye as a main component is provided, and further a protective layer is provided as necessary. In the medium, the recording layer is composed of a dye film having a peak of spectral reflectance near the recording and reproducing wavelength, and the film thickness is defined to be such that the film thickness dependence of the reflectance at the recording and reproducing wavelength is maximum. An optical information recording medium is provided.

Further, according to the present invention, an optical information recording medium having a recording layer containing an organic dye as a main component is used, and light having a wavelength near the peak of the spectral reflectance of the recording layer is focused on the recording layer. , there is provided a recording method characterized in that information is recorded by destroying the interference structure of the recording layer.

The present invention will be described in detail below with reference to the drawings.

In a conventional optical information recording medium having a recording layer of a single layer of organic dye, as illustrated in FIG. Those having spectral absorption/reflection characteristics near 870 nm were often used.

That is, dyes having a spectral absorption peak near the recording/reproducing wavelength have been used.

This is based on the idea of increasing the absorption efficiency of light energy, decomposing and sublimating the dye film, and obtaining a highly sensitive recording medium. In the present invention, unlike this, information is recorded and reproduced using light having a wavelength near the peak of the spectral reflectance of the dye film.

Therefore, as shown in Figure 1, a dye with a spectral reflectance peak near the recording/reproducing wavelength is used in the 28th layer, and the 29th layer is designed so that the film thickness dependence of the reflectance is maximum at the recording/reproducing wavelength. Specify the thickness. Figure 3 illustrates the film thickness dependence of the reflectance and transmittance of the dye film used in the examples described later.In the present invention, we focused on the film thickness dependence of the reflectance, and Use the one with the maximum film thickness. As is clear from FIGS. 1 and 3, a recording medium using such a dye film has high reflectance and low absorption. The reason for this is that, as shown in Figure 4, when the complex refractive index of a dye is n=n-1k, for organic dyes, the extinction coefficient generally reaches its maximum near the absorption peak, and n reaches its minimum; This is because it increases rapidly on the longer wavelength side. That is, in a simple example, plastic (n=1.
Considering the interface with 5-i.0), the reflectance R is expressed by the following formula: (n+1.5)''2/10 This is because the term n becomes dominant on the long wavelength side.

Another means of increasing the reflectance can be achieved by setting the thickness of the dye film so that the reflections from the front and back surfaces interfere and strengthen each other.

When using a recording medium with an organic dye film having the optical properties and film thickness as described above as a recording layer, light absorption is reduced and rapid decomposition or sublimation of the dye film is less likely to occur. Just by deforming the film, the interference structure of the film is destroyed, the reflectance is significantly reduced, and recording can be performed. FIG. 5 shows how the interference structure of the film is destroyed and information is recorded.

In the figure, 1 is a recording medium, 2 is a substrate, 3 is recording/ff, 4 is an incident beam, and 5 is a pit. In addition, FIG. 6 shows how recording is performed when another recording medium according to the present invention is used. Elements similar to those in FIG. 5 in FIG.
indicates a protective film. This recording medium 1 has a thermoplastic protective film 6
If this is done, mixing or dissolution of materials will occur at the interface between the protective film 6 and the recording Jtj (dye film) 3 due to laser irradiation, the clean interface will disappear, and the interference structure will be destroyed. I can do it. This causes a partial decrease in reflectance and recording is performed. In this case, by appropriately selecting the material and thickness of the dye film, and the thermal and chemical properties of the protective film, it is possible to create a recording medium in which the sensitivity and Cr do not decrease even when a protective film is provided. .

When an optical information recording medium is configured as described above, for example, when reading by irradiating weak light (approximately 1/10 the power of writing) and reproducing, little light is absorbed by the recording layer. Deterioration is reduced. Further, by providing a protective layer, oxygen and dyes in the air are blocked, so deterioration caused by reproduction light is further reduced. Furthermore, if it becomes possible to provide a protective layer, a single-plate structure or a laminated structure becomes possible, and the optical information recording medium of the present invention can also be used for applications such as optical cards and optical floppies. becomes.

Next, the materials constituting the optical information recording medium of the present invention and the necessary characteristics of each layer will be specifically explained.

(1) Substrate As a necessary characteristic of the substrate, it must be transparent to the laser beam used only when recording and reproducing is performed from the substrate side, and it does not need to be transparent when recording and reproducing is performed from the recording layer side. As the substrate material, for example, plastics such as polyester, acrylic resin, polyamide, polycarbonate resin, polyolefin resin, phenol resin, epoxy resin, polyimide, glass, ceramic, or metal can be used.

Note that a guide groove or a guide pit for tracking, and a preformat such as an address signal may be formed on the surface of the substrate.

(Z) Undercoat layer The undercoat layer (a) improves adhesion, (b) serves as a barrier against water or gas, (C) improves storage stability of the recording layer, and (d)
) improvement of reflectance; (e) protection of the substrate from solvents;

(f) Used for the purpose of forming guide grooves, guide pits, preformats, etc. For the purpose of (a), various polymer materials such as ionomer resins, polyamide resins, vinyl resins, natural resins, natural polymers, silicones, liquid rubbers, and silane coupling agents may be used. For the purposes of (b) and (c), inorganic compounds such as Sin□, MgF, 5iO1Tie2, ZnO, Ti
Metals or metalloids such as N, SiN, etc. Zn, C
u, S, Ni, Cr, Ge.

Ss, Au, Ag, AQ, etc. can be used. Also, for the purpose of (d), metals such as AI2
．． Ag, Te, etc., or an organic thin film with metallic luster, such as methine dye, xanthine dye, etc., can be used, and for the purposes (e) and (f), an ultraviolet curing resin.

Thermosetting resin, thermoplastic resin, etc. can be used.

(3) Recording layer a/ffi is a device that causes some kind of optical change by irradiation with laser light and can record information by that change.
Its main components include, for example, croconium-type dyes, azulene-type dyes (pigments), 1-rifetchiazine compounds, phenanthrene derivatives, phthalocyanine compounds, tetrahydrochlorine compounds, dioxane compounds or their derivatives, anthraquinone derivatives, xanthine pigments, and triphenylmethane. It consists of type pigments, squarylium type pigments, polymethine pigments (pyryllium type pigments, cyanine pigments, merocyanine pigments, etc.), croconium pigments bound with polymethine, azulene type pigments bound with polymethine, etc.

The recording layer in the present invention may contain other dyes, for example, if necessary, in order to improve recording characteristics and stability.

Phthalocyanine series, tetrahydrocholine series, dioxazine series, triphetchazine series, phenanthrene series, anthraquinone (indanthrene) series, cyanine (merocyanine) series, croconium series, xanthine series, triphenylmethane series, pyrylium series, squarylium series, azulene dyes, metals or metal compounds 1, e.g., In, S
n, Te, Bi, AQ, Se, Tc02.5
nO1As, Cd, etc. may be dispersed and contained, and v
It may be an L layer.

In addition, the recording layer may contain a polymeric material, an organic compound (aminium, immonium, diimmonium compounds, etc.) or an organometallic complex compound (bisdithiodiketone, bisphenyldithiol, etc.) that has an absorption ability in a wavelength range longer than that of the cyanine dye. A low-molecular-weight compound such as a complex, etc.) may be mixed and dispersed. In addition, falN includes storage stabilizers (metal complexes, phenolic compounds), dispersants, flame retardants,
A lubricant, a plasticizer, etc. can be contained. As mentioned above, the thickness of the recording layer is set to a value that maximizes the reflectance at the wavelength used. The value depends on the birefringence of the recording layer and is not uniquely determined, but it is approximately 100 to 10 μm.
, preferably 200 people to 2 μm. Methods for forming the recording layer include vapor deposition, CVD, sputtering, and solvent coating methods, such as dip coating.

Spray coating, spinner coating, blade coating, roller coating, curtain coating, etc. can be used.

(4) The three-layer protective layer (a) protects the recording layer from scratches, dust, dirt, etc., and (b) improves the storage stability of recorded JPJ.

(c) Used for the purpose of improving reflectance, etc. For these purposes, the materials shown in the above subscript H can be used, but in the present invention, in order to maintain sensitivity and C/N as described above, polymethyl acrylate 1, polycarbonate , epoxy resin, polystyrene,
Heat softening and heat melting of polyester resin, vinyl resin, cellulose, aliphatic hydrocarbon resin, aromatic hydrocarbon resin, natural rubber, styrene butadiene resin, chloroprene rubber, wax, alkyd resin, drying oil, rosin, etc. It is more preferable to use a synthetic resin.

In the present invention, the undercoat layer and the protective layer 1! JJfj contains a stabilizer, a dispersant, and a flame retardant, as in the case of the recording layer.

A lubricant, an antistatic agent, a surfactant, a plasticizer, etc. can be contained. Furthermore, 1 is also applied to the undercoat layer and protective layer.
Compounds according to the invention may be included.

〔Example〕

The present invention will be further explained below with reference to Examples, but the present invention is not limited to these Examples.

Example 1 The compound of structural formula (1) was added to 1,2-dichloroethane by about 1
A solution was prepared by dissolving wt%. Add this solution to another 100
When I diluted it twice and measured the spectral absorption spectrum, it was 690.
There was an absorption peak at nm. The stock solution was spin-coated onto a hard-coated acrylic plate, and the reflection and absorption spectra from the substrate side were measured.
A spectrum as shown in FIG. 1 was obtained. Dye film samples with various film thicknesses were created by varying the rotation speed during the spin code. The reflectance and transmittance of this dye film were measured at a wavelength of 790 nm, and the data shown in FIG. 3 was obtained by plotting the corresponding reflectance and transmittance with the transmittance as the optical density and the film thickness as the horizontal axis. It was found that the reflection becomes maximum when the film J'l- has an absorption dust of 0.4.

A polymethyl methacrylate (PMMA) board with a thickness of 1 or 2 m+ and a diameter of 130 mm is coated with acrylic photopolymer to a depth of 900 people, a width at half maximum of 0.4 μm, and a pitch of 1.
．． A recording medium was obtained by spin-coding the stock solution on a substrate provided with 6 μm spiral groups under conditions such that the optical density was 0.4.

This recording medium was rotated at a linear velocity of 2.1 m/see, and semiconductor laser light with a wavelength of 790 nm was irradiated from the substrate side. The beam diameter of the laser beam used at this time at the writing point was approximately 1.3 μm. What is the recording frequency?

Recording was performed using 0.5 MNz as the fundamental frequency.

At this time, a C/N of 55 dB was obtained with a recording power of 3 mW.

It was found that sufficient records were being kept. When this recorded portion was read 1 million times with a reproduction power of 0.3 mW, the amplitude decreased by about 10%.

Comparative Example 1 A recording film was formed in the same manner as in Example 1 except that the optical density was 0.6, a recording medium was obtained, and evaluated in the same manner, but the obtained C/N was 45 dB. Yes, 10
The decrease in amplitude after 00,000 readings was 25%. Comparative Example 2 A recording medium was produced in the same manner as in Example 1, except that the recording film was adjusted so that the optical density was 0.25. evaluated. Although a C/N of 55 dB was obtained, the amplitude drop after 10,000 readings was 3 degrees.

Example 2 In Example 1, a protective layer was further provided on the recording film to produce a recording medium. As the protective layer, an aromatic hydrocarbon resin (trade name Vetrozin #130, manufactured by Mitsui Petrochemicals) was dissolved in cyclohexane at 2 wt % and spin-coded at 400 rpm. As a result of evaluation in the same manner as in Example 1, the C/N was 53 d[l, and the amplitude deterioration after 1 million reproductions was 7%.

Example 3 A recording medium was prepared and evaluated in the same manner as in Example 1, except that the following compound (2) was used instead of compound (1), and similar results were obtained.

e Table 1 Examples 4 to 11 In Example 1, compounds 3 to 10 in Table 1 were used instead of Ibi compound (1) to form a recording film with a thickness that maximized the reflectance. Got the medium. Note that a protective layer was provided as appropriate. Table 2 shows the evaluation results of these recording media.

[Effects of the Invention] As explained in detail above, according to the present invention, high sensitivity,
A low-cost optical information recording medium that can be made thinner by using a single-layer structure and recording using light at a wavelength near the peak of the spectral reflectance of the recording layer while maintaining a high C/N. It becomes possible to provide

Furthermore, the present invention can be used not only for optical discs but also for optical cards and optical floppies. Also, CD
It is also possible to replace it with a CD-ROM or the like.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the spectral reflectance and absorption of the organic dye film according to the present invention, and FIG. 2 is a diagram showing the spectral reflectance and absorption of the organic dye film used in a conventional recording medium. Figure 3 is a diagram showing the relationship between the reflectance and transmittance of the dye film in Figure 1 and the film J. Figure 4 is a diagram showing the relationship between the refractive index and extinction coefficient of a general organic pigment film and wavelength. 5 and 6 are diagrams showing how the interference structure of the recording film is destroyed and information is recorded. 1... Recording medium 2... Substrate 3... Recording layer 4... Incident beam 5... Pit 6... Protective layer photo; field ← 8 Figure 3 Figure 4 Filter table (nm) Figure 5 Figure 6 2-12g) Sea bream;-

Claims (1)

[Claims] (1) In an optical information recording medium in which a recording layer containing an organic dye as a main component is provided directly or via an undercoat layer on a substrate, and a protective layer is further provided as necessary, the recording layer has a wavelength close to the recording/reproducing wavelength. 1. An optical information recording medium comprising a dye film having a spectral reflectance peak at , the film thickness being defined to a film thickness that maximizes the film thickness dependence of the reflectance at the recording/reproducing wavelength. (2) Using an optical information recording medium having a recording layer containing an organic dye as a main component, light having a wavelength near the peak of the spectral reflectance of the recording layer is focused on the recording layer, and A recording method characterized by recording information by destroying an interference structure.