JPH02230526A - Optical information recording medium - Google Patents

Abstract

PURPOSE:To obtain an optical information recording medium which has high sensitivity, high contrast, high C/N, excellent reliability and repetitive reproducing characteristics and can be formed in a single plate or in a thin medium by providing a recording layer essentially comprising org. dyes directly on a substrate or with a base layer interposed on the substrate and further providing a protective layer thereon. CONSTITUTION:The protective layer 13 consists of a blend of polymers which can change their state from soluble in each other to separated and vice versa depending on temp. The recording layer 12 contains the org. dye as the chief component which shows the peak of a reflection near the wavelength of light for recording/reproducing, and its thickness is determined so that the maximum reflectivity can be obtained by an interferential effect of multireflection. Informations are recorded in this recording medium 10 by irradiating the recording layer 12 with laser beam a specified power. The irradiated area is heated and the state of the polymer blend in the protective layer 13 near the recording layer-protective layer interface changes from soluble to separating, by which the interface also deforms to form the pit 14. By this method, a recording medium of single plate structure with high sensitivity, high C/N and high contrast can be obtained and the obtd. medium has improved storage stability and repetitive reproducing property owing to the protective layer.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improved optical information recording medium 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 because of their large capacity, 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, optical cards, and optical floppies.

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

(a) A low melting point metal thin film is used as the recording layer. (b) A recording layer has a two-layer structure consisting of a reflective film and an organic light absorption layer. (C) A high reflectance organic dye film is used as 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 reflectance change accompanying a crystal-to-amorphous phase transition. There is a phase change type. This type of recording medium has disadvantages such as poor storage stability, hole-punched type media with low resolution and low recording density, and phase change type media with difficult manufacturing conditions and high costs.

The recording medium of type 2 (b) is a metal reflective film.
- An organic light-absorbing layer is provided by coating, and the organic light-absorbing layer is irradiated with a laser beam to create a depression, thereby recording information. This type of recording medium is difficult to manufacture because the recording layer has a 2M structure in which an organic absorption layer is laminated on a metal reflective film, and since it has a reflective layer, it is difficult to record and read from the substrate side. There is a drawback.

The recording medium of type (c) is one in which a thin organic dye film with high reflectivity is provided as a recording layer on a substrate. 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 conversion, and high reliability.Furthermore, because the film can be formed by coating, it is easy to mass produce and reduces costs. There are some promising benefits. However, unless this type of recording medium has an air-than-I 1-inch structure, the sensitivity and C/N will drop 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 was first commercialized using an optical disk with a diameter of 30c+n, and later, the 20an type,
There are signs that it will gradually become smaller in diameter to the 13an type, and eventually shift to the 9-stroke 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.
．． 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 acts as a heat insulating layer to increase thermal efficiency, and does not suppress evaporation, decomposition, or scattering of the recording layer during recording, resulting in high sensitivity and high C/C.
N was able to be maintained.

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

Therefore, the present inventors proposed an optical information recording medium (C) in Japanese Patent Application No. 14751.1/1983, in which a recording layer containing an organic dye as a main component is provided on a substrate, and a protective layer is further provided as necessary. In this case, the recording layer is composed of a dye film having a peak of spectral reflectance in the vicinity of the wavelength of the recording/reproducing light, and the film thickness is set such that the thickness dependence of the reflectance at the wavelength of the recording/reproducing light is maximum. We proposed an optical information recording medium set to

The above optical information recording medium 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 previously proposed 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 Fig. 1, a dye that exhibits a peak of spectral reflectance near the recording/reproducing wavelength is used for the recording Jtl, and the film thickness of the recording layer is Specify the thickness. Figure 3 illustrates the film thickness dependence of the reflectance and transmittance of a dye film.Here, we will focus on the film thickness dependence of the reflectance, and calculate the film thickness at which the reflectance is maximum. use. 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 R=n-]k, in general, for organic dyes, the extinction coefficient k is maximum and n is minimum near the absorption peak; This is because it increases rapidly on the longer wavelength side than the peak. That is, in a simple example, plastic (R=1.5-j
When considering the interface with

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 the dye film is less likely to rapidly decompose or sublimate; Just by deforming the dye film, the interference structure of the film is destroyed and the reflectance is significantly lowered, making it possible to record. 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 a recording layer, 4 is an incident beam, and 5 is a pin 1. Further, FIG. 6 shows how recording is performed using another recording medium.

In the figure, elements similar to those in FIG. 5 are given the same reference numerals, and 6 indicates a protective layer. This recording medium 1 is provided with a thermoplastic protective layer 6, which allows materials to be mixed and dissolved at the interface between the protective layer 6 and the recording layer (dye II!A) 3 by laser irradiation. occurs, the clean interface disappears, and the interference structure can be destroyed. This causes a partial decrease in reflectance and recording is performed. In this case, the material of the pigment film, the film j
By appropriately selecting the thermal and chemical properties of the protective film, it is possible to create a recording medium in which the sensitivity and C/N do not decrease even when the protective layer is provided.

When an optical information recording medium is configured as described above, for example, when reproducing by irradiating weak light (power of about 1710 during writing) at the time of reading, there is little light absorbed by the recording J+'7, so the reproducing light Deterioration caused by Furthermore, by providing a protective layer, oxygen and pigments in the air are removed, further reducing deterioration caused by reproduction light. If it becomes possible to provide a protective layer, a single-plate structure or a laminated structure becomes possible, and it becomes possible to use it for applications such as optical cards and optical floppies.

[Problems that the invention attempts to solve]

The optical information recording medium previously proposed by the present inventors is different from the conventional one that forms bits, and records by deforming only the interface and destroying the interference effect, resulting in high sensitivity. The aim is to However, in this optical information recording body, if a protective film is provided on the recording layer, the material of the dye film, the film, the thermal and chemical properties of the protective film, etc. must be strictly controlled. However, there is a problem that a slight decrease in sensitivity cannot be avoided, although it is not as bad as with conventional recording methods, and there is room for further improvement.

For this reason, the present inventors recently applied for patent application No. 63-27608.
According to the specification of No. 6, it is proposed to form a protective layer in an optical information recording medium such as that described in No. 2 using a coloring material having an absorption peak near the recording/reproducing wavelength and a thermosoftening resin, and the patent application No. 1983- No. 28981.3 proposed forming a protective layer in a similar optical information recording medium using a polymeric dye that exhibits an absorption peak near the recording and reproducing wavelength.

According to the former proposal, the reduction in sensitivity can be effectively suppressed by adding a coloring agent, but if the coloring system crystallizes or generates migration during storage, the defect rate and error rate will decrease. This has the disadvantage of causing an increase.

On the other hand, with the latter proposal, the inconveniences like the former proposal were eliminated and the sensitivity improved, but pins 1 to 1 due to unevenness were improved.
Compared to recording media, the sensitivity is still low, and a level 1 level of sensitivity is desired.

Therefore, in view of the above-mentioned circumstances, the present invention further improves the optical information recording medium, and achieves higher sensitivity, higher contrast, higher C/N, and can be made into a single plate and thinner. It is an object of the present invention to provide an optical information recording medium with excellent reliability and repeated playback characteristics.

[Means and effects for solving the problem] In order to achieve the above object, according to the present invention, a recording layer containing an organic dye as a main component is provided on a substrate directly or via an undercoat layer, and In an optical information recording medium, the optical information recording medium is provided with a protective layer, and records and reproduces information by destroying the interference structure of the recording layer by irradiating it with light having a wavelength near the peak of the spectral reflectance of the recording layer. There is provided an optical information recording medium, wherein at least one of the protective layer and the undercoat layer is made of a polymer blend that can change state between a compatible state and a phase-separated state due to temperature changes.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 7 is a cross-sectional view showing an example of the structure of the optical information recording medium of the present invention, in which (a) shows an unrecorded state, and (b) shows a recorded state. In the figure]0 is a recording medium, 11 is a substrate, 12 is a recording layer, 13 is a protective layer, ]4 is a pin 1-, and 16 is a laser beam. The protective layer l3 is formed using a polymer blend whose state can change between a compatible state and a phase-separated state depending on temperature changes. Recording N]2 is mainly composed of an organic dye that exhibits a reflection peak near the wavelength of the recording and reproducing light, and its film thickness is set so as to provide the maximum reflectance due to multiple reflection interference.

To record information on the optical information recording medium 10, a laser beam of a predetermined power is applied to the recording layer I in a state as shown in FIG. 7(a).
2 to generate heat in the irradiated area, and the heat changes the polymer blend of the protective layer 13 near the recording no-protective layer interface in that area from a compatible state to a sum-separated state, and the interface also deforms. This is done by forming a pit 1- as shown in FIG. 7(b). At this time, since a polymer blend is used for the protection calendar l3, the deformation of the interface can be made easier and larger.

Information is reproduced by irradiating the recording Ji 1 2 with a laser beam having a predetermined power weaker than that during recording, but as shown in FIG. 7(.)
When a laser beam is irradiated onto a portion where the pits 1 to 1 are not formed, the laser beam is reflected multiple times by the interference structure of the recording layer 12, as shown by the arrows in the figure. On the other hand, when the part where the pits 1 to 14 are formed is irradiated with a laser beam as shown in FIG. 7(b), the laser beam will not cause multiple reflections due to the light scattering effect due to the interface deformation and phase separation state in the bit 14. . Therefore, the contrast 1 to 1 is obtained depending on the presence or absence of the formation of the piso 1 to 14, and information can be reproduced by detecting this. in this case,"
Dot 1 using Polymer Blen 1 ~ like a double series
Since the deformation of the interface in No. 4 is large, high sensitivity can be achieved.

Further, according to the present invention, as shown in FIG. 8, an undercoat layer 15 may be provided between the substrate 1 and the recording layer 12. FIGS. 8(a) and (b) are views corresponding to FIGS. 7(a) and (b), respectively. In this case, the undercoat layer 15 may be formed of a conventionally used material,
Similar to the protective layer 13, it may be formed in a compatible state of polymer blends. The illustrated example is the latter case, and in this optical information recording medium, after recording, only the undercoat JFJ-recording layer interface or both the undercoat layer-recording layer-protective layer are used. Pits are formed at the interface, and by deforming the interface and imparting a light scattering effect, it becomes possible to achieve high sensitivity, high convergence, and lath.

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 preformat such as a guide groove for tracking, a guide pin 1, and a response signal may be formed on the surface of the substrate.

(2) Undercoat layer The undercoat layer has (a) an adhesion property, (b) a barrier such as water or gas, (c) an improvement in storage stability of the record I11, and (d) an improvement in reflectance. (e) protection of the substrate from solvents;
(f) Used for 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 are used. For the purposes (b) and (c), inorganic compounds such as Bib2, MgF2, SiO, Tj. 0,, ZnO,
TiN. Metals or metalloids such as SiN, e.g. Z
n. Au. S. Ni. Cr. Ge. Se.
Au, green, 80, etc. can be used. Also,(
For the purpose of d) metals, such as AQ. Ag.
Te, etc., an organic thin film having metallic luster, such as methine dye, xanthene dye, etc. can be used, and (e)
For the 11th target (f), ultraviolet curing resin, thermosetting resin, thermoplastic resin, etc. can be used.

Further, as described above, higher sensitivity can be achieved by using a polymer blend that can change the state between a compatible state and a phase-separated state depending on temperature changes for the undercoat layer.

(3) Recording layer The recording layer can record information by destroying the interference structure by irradiation with laser light, and its main components are, for example, croconium-type dyes, azulene-type dyes (pigments), triphenothiazine compounds, and phenanthrene derivatives. , Futa-cyanine compounds, Te1-herahytrochlorin compounds, dioxane compounds or their derivatives, anthraquinone derivatives, xanthene dyes, triphenylmethane-type dyes, squarylium-type dyes, polymethine dyes (virylium-type dyes, cyanine dyes, merocyanine dyes, etc.) ), croconium pigments bound with polymethine, azulene-type pigments bound with polymethine, etc.

In order to improve recording characteristics and stability, the recording layer of the present invention may contain other dyes, such as futa-cyanine-based, ter-1-herahi-1-locorin-based, dioxazine-based, triphenothiazine-based, Phenanthrene series, an-1-laquinone (indanthrene) series, cyanine (merocyanine)
In. Sn.
Te. Bi. All. Se, 1' e O 2
, SnO. As. Cd etc. may be dispersed and contained,
It may also be laminated.

In addition, the recording layer may contain a polymer material, an organic compound (aminium, immonium, diimmonium compounds, etc.) or an organometallic complex compound (bisdithiodicene, bisphenyl A low-molecular compound such as a dithiol complex (such as a dithiol complex) may be mixed and dispersed. Furthermore, the recording layer contains other storage stabilizers (
metal complexes, phenolic compounds), dispersants, flame retardants, lubricants, plasticizers, etc. 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 complex refractive index of the recording layer and is not uniquely determined, but it is approximately 100 to 10 μm.
, preferably 200 to 2 μm. As a method for forming the recording layer, vapor deposition, CVD, sputtering, and solvent coating methods such as dip coating, spray coating, spinner coating, blade coating, roller coating, force-ten coating, etc. can be used.

(4) Protective layer The protective layer (a) protects the recording layer from scratches, dust, dirt, etc., (b) improves storage stability of the recording layer, (c) improves reflectance, and (d) sensitivity. It is used for the purpose of improving.

In the present invention, a polymer blend whose state can change between a compatible state and a phase-separated state due to temperature changes is used as a material for the protective layer. The polymer blend used in the present invention is preferably of the lower critical cosolute temperature (I, CST) type, which is transparent at room temperature and undergoes phase separation and becomes cloudy above the clouding point.

Although the cloud point varies depending on the type, composition, molecular weight and molecular weight distribution of the polymer, it is preferably in the range of 150 to 400°C. Specific examples of such LCST type polymer blends are shown below.

(i) Combination of amorphous polymers polystyrene and polyvinyl methyl ether, styrene
Acrylonitrile copolymer and poly-ε-cabrolactone, styrene-acrylonitrile copolymer and polymethylmethacrylate-1-, polyvinyl nitrate and polymethyl acrylate, ethylene-vinyl acetate copolymer and chlorinated bim, poly-E-cabrolactone and Polycarbonate (bisphenol A type), p-chlorostyrene/0-chlorostyrene copolymer and poly(2,6-dimethyl-1,4-phenylene oxide), polycarbonate (bisphenol A)
type) and ethylene oxide block copolymer, butylene terephthalate/tetrahydrofuran block copolymer and polyvinyl chloride, thermoplastic polyurethane [polyε-caprolactone soft block] and polyvinyl chloride.

(11) Combinations of crystalline polymer and amorphous polymer: polyvinylidene fluoride and polymethyl acrylate 1, polyvinylidene fluoride and polyethyl acrylate 1, polyvinylidene fluoride and polymethyl methacrylate 1, polyfluoride Vinylidene chloride and polyethyl methacrylate, polyvinylidene fluoride and polyhinylmethyl methacrylate.

(iji) Combinations of crystalline polymers and crystalline monomers: polyethylene oxide, 1 helioxane, polyE-1 caprolac 1 hene and 1-lioxane.

Note that the protective layer may be a single layer or a laminate.

In the present invention, the undercoat layer and the protective layer include recording 1
As in the case of G, stabilizers, dispersants, flame retardants, lubricants, antistatic agents, surfactants, plasticizers, etc. can be contained.

In addition, the undercoat layer and the protective layer may contain a light-absorbing substance in order to further improve the sensitivity as described above, but in this case, the light-absorbing substance is the recording
The materials shown in the material examples a) are used.

〔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) Thickness l. ．． 2 mm, diameter 1.30 nwn polymethyl methacrylate 1 ~ board'' - acrylic pho 1 polymer depth 900 people, half width 0.4 μm, pinch 1
．． A 6 μm spiral guide groove was provided to serve as a substrate. A compound represented by the following formula (1) was added to this substrate at 10-'T.
A layer having a thickness of 800 wafers was formed by vacuum evaporation under an atmosphere of 100 ml.

Furthermore, polystyrene and polyvinyl methyl ether were dissolved in a 1-luene solution and coated with a vinyl coating to form a protective layer having a thickness of 10 μm, thereby obtaining a recording medium.

(Example 2) A recording medium was produced in the same manner as in Example 1 except that a compound represented by the following formula (TI) was used instead of the compound represented by the above formula (1) to form a recording layer with a thickness of 700 mm. I got it.

A 1 μm undercoat Mjjtr was formed. On top of that, add the following formula (
The compound represented by III) was dissolved in methanol/1,2-dichloroethane (9:1 weight ratio) and coated with a spinner to form a recording layer with a thickness of 800 mm.

(Example 3) A recording medium was obtained in the same manner as in Example 1, except that polyvinylidene fluoride and polymethyl methacrylate were dissolved in a dimethylacetamide solution to form a protective layer with a thickness of 5 μm.

(Example 4) On the substrate of Example 1, polyε-1 turnip sictone-bisphenol A type polycarbonate 1 was dissolved in a 1,2-dichloroethane solution and coated with a spinner. A vinyl copolymer was dissolved in carbon tetrachloride and coated with a spinner to form a protective layer with a thickness of 10 μm to obtain a recording medium.

(Example 5) A recording medium was obtained in the same manner as in Example 1 except that the same undercoat layer as in Example 4 was formed.

(Comparative Example 1) Example 1 except that a vinyl chloride-vinyl acetate copolymer was used and a protective layer with a thickness of 5 pm was provided.

(Comparative Example 2) Example 2 except that a vinyl chloride-vinyl acetate copolymer was used and a protective layer with a thickness of 5 μm was provided.

(Comparative example 3) Example 4 except that the undercoat J was not provided.

(Comparative example 4) Example 4 except that the protective layer was not provided.

Each recording medium produced as described above was measured at a linear velocity of 2. 1
m/see, and a semiconductor laser beam 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 about 1.3 μm. Recording was performed using a fundamental recording frequency of 0.5 MIIz, and the appropriate recording power at that time was determined.

Then, the recorded information was reproduced, and the reproduced waveform was subjected to sub-1H analysis, and the reflectance and C were measured. Furthermore, this same recording medium was continuously irradiated with IKW tungsten light from a distance of 30 cm for 20 hours to perform an accelerated playback deterioration test, and the reflectance and Cc were flt! I decided. In this case, the reflectance was measured with a parallel tip from the substrate side.

The above measurement results are shown in the table below. In addition, in Section 2, the appropriate recording power refers to the recording power at which the eye center becomes 50% when a random pattern is recorded.

Table 1 [Effects of the Invention] According to the present invention, the above structure provides an optical information recording medium that has a single-panel structure (adhesively laminated thin structure) and has high sensitivity, high C, and high contrast. becomes possible. In addition, by providing the protective layer, the recording layer does not come into direct contact with the outside air, which improves storage stability and repeated playback characteristics.

[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, FIG. 2 is a diagram showing the spectral reflectance and absorption of the organic dye film used in conventional recording media, and FIG. The figure shows the relationship between the reflectance and transmittance of the dye film in Figure 1 and the film thickness. Figure 4 shows the relationship between the refractive index and extinction coefficient of a general organic pigment film and the wavelength. 5 and 6 are diagrams showing how the interference structure of the recording film is destroyed and information is recorded, and FIG. 7 is a cross-sectional view showing the state before and after bit formation in the configuration example of the optical information recording medium of the present invention. , FIG. 8 is a diagram similar to FIG. 7 in another configuration example of the optical information recording medium of the present invention. 1.0... Recording medium, 11... Substrate 12... Recording layer 13... Protective layer 14... Pit 15... Undercoat layer

Claims (1)

[Claims] (1) 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 on top of the recording layer, and light having a wavelength near the spectral reflectance peak of the recording layer is provided. In an optical information recording medium that records and reproduces information by destroying the interference structure of the recording layer by irradiating the medium with
An optical information recording medium, wherein at least one of the protective layer and the undercoat layer is made of a polymer blend that can change state between a compatible state and a phase-separated state due to temperature changes.