JP2531762B2 - Optical recording medium - Google Patents

Description

The present invention relates to an optical recording medium used for an optical recording medium such as a write-once optical disc, and particularly to an optical recording medium suitable for improving the recording amount per unit surface. Regarding the configuration of.

[Conventional technology]

An example of using a dye as an optical recording medium has been published for a long time. For example, JP-A-56-154087 discloses an example of irradiating a copper phthalocyanine film with light to form a pit for recording. . However, this method cannot record and read each layer of the laminated film as in the present invention.

In addition, Kinki Chemical Society Functional Dye Subcommittee Material No.
Nanba, “Stabilized Cyanine Dye Material for Optical Discs” by Matsui, 6, pp 17-22 (Showa 63-2), describes that ultra-thin (thickness 0.05-0.1μ
An example is shown in which information is recorded by irradiating the coating film surface of m) with light. A schematic view of the oblique cross section of this example is shown in FIG. In FIG. 3, 31 is an optical recording medium layer formed on the transparent film-forming substrate 32, of which 311 is an unrecorded portion,
Reference numeral 12 is a light irradiation recording unit. However, this document does not describe the situation relating to the sequential lamination of coating films and the multiple recording of different kinds of information for each layer as in the present invention.

[Problems to be Solved by the Invention]

In the above conventional technology, the increase in the recording amount per unit surface is
It will depend on shortening the wavelength of irradiation light and increasing the optical scanning density. However, in these conventional techniques, it is difficult to increase the recording amount to twice the current level, for example, in view of the characteristics of the current semiconductor laser and the configuration of the irradiation optical path system.

An object of the present invention is to achieve an increase in the recording amount per unit surface by multiple recording on a single optical scanning line without being restricted by the current technology as described above, and an optical recording that can realize it. To provide the medium.

[Means for solving the problem]

The above object can be achieved by combining a plurality of types of light having different wavelengths and different wavelengths from each other as described below, and by discriminating and separating the light.

That is, a film containing a plurality of kinds of dyes having different light absorption wavelengths of 100 nm or more, respectively, is sequentially formed and laminated on, for example, a transparent substrate with a guide groove, and this is used as an optical recording medium.
The medium layer is irradiated with light obtained by synthesizing a plurality of types of laser light having wavelengths that match the absorption wavelengths of the dyes of the main components of the medium constituent layer. As a result, for each layer forming the optical recording medium, light having a different wavelength from the absorption wavelength of the dye as the main component is transmitted, and only light having the same wavelength is selectively absorbed, and at the same time, heat is generated by light-heat conversion. It promotes discoloration of the part and allows recording of information modulated by the irradiated light.

Then, after the light having the same wavelength as the recording light and reduced in intensity only is synthesized by the same procedure as at the time of recording, this light is applied to the medium layer provided with the recording mark. As a result, the medium layer transmits the light having a wavelength different from the absorption wavelength of the dye and absorbs the light having the same wavelength in the same mechanism as that at the time of recording, but the absorptivity of the recording mark portion is reduced by the amount of thermal transformation. That is, since the reflectance is high, a considerable part of the light is reflected and becomes return light from the medium layer, and returns to the optical path system that is the source of light irradiation to the medium layer. Then, the weak return light returned from each layer of the optical recording medium is discriminated and separated in the synthetic lens,
Recording / reading is completed by returning each to a reading system that duplicates them into an electrical signal.

The present invention uses a plurality of types of films, which are used for the above optical recording, having a light absorption wavelength in the visible light region to the near infrared light region and having different absorption wavelengths as main components, respectively, on a substrate. In the above optical recording medium, the plurality of types of films are each formed by a coating film, and a thin layer of a photopolymerization resin is provided between the coating films.

[Action]

Problems in the above-mentioned solution means are selection of a dye to be an optical recording medium, configuration of a medium layer by the dye, generation of weak return light from an optical recording mark, and discriminative reading of the return light. The details will be described below.

The dye used in the present invention has absorption wavelength selectivity
In addition to this, the transmittance for light having a wavelength more than 100 nm away from the absorption wavelength and the reflectance of 10% to 20% in the transformation part formed by thermal transformation due to absorption and heat generation of light
It is necessary to increase and increase the transmission of light of different wavelengths.
In addition to the above, it is also necessary that the thermal transformation of the dye is not accompanied by melting or evaporation of the dye. This is a melting,
This is because if there is evaporation or the like, the layered state of the film will change before and after light irradiation and phase transformation, and measures to suppress this will be necessary.

In consideration of the above points, a cyanine dye having the following structural formula is selected as the dye.

This dye is a methine group in the chain that connects the ring parts at both ends,
The absorption wavelength changes depending on the number added to -CH = CH. That is, when the number of methine groups shown in the above structural formula is 3, the absorption wavelength is about 830 nm, when the number of methine groups is 2, it is about 650 nm, when the number of methine groups is 4, it is about 1050 nm, and the absorption wavelengths differ by about 200 nm depending on the number of methine groups. Also, this dye
It absorbs and heats itself and undergoes thermal transformation, but since it has good thermal conversion properties, it can be mixed with a color former to form a composite. further,
This dye has high transparency to light having a wavelength outside the absorption wavelength, and has the characteristics required for an optical recording medium. Therefore, these characteristics should be used in a manner suited to the purpose.

In the present invention, as the medium layer of the optical recording medium, as described above, a plurality of types of films are formed by coating films, respectively, and the photopolymerization resin thin layer is provided between the coating films, so that a laminated medium is formed. Can be stably performed, and performance deterioration of the laminated film itself can be prevented.

Further, the above-mentioned recording on the medium layer may be carried out by paying attention to this point, as long as the characteristics of the dye are not impaired. As the remaining problem, there is a discriminative reading of a plurality of types of return light, which are weak from the optical recording mark, that is, a plurality of kinds of light having different wavelengths whose light amount is reduced to a fraction of the irradiation light.
This can be solved by using the technology of the invention, which has a photosynthesis / separation lens system as a main constituent, which is separately applied.

[Embodiment] Here, general matters and main points regarding an embodiment of the present invention will be shown first, and then details will be described by way of specific examples.

FIG. 1 shows the state of the multi-recording method and the recording traces by the optical recording medium of the laminated structure and the irradiation of the light in different parts, and FIG. The conditions relating to the optical recording medium according to the present invention, such as formation conditions, are schematically shown.

First, the laser light sources used are small, lightweight, and general-purpose oscillation wavelengths of λ ₁ : 650 nm and λ ₂ : 8, respectively.
A semiconductor laser of 30 nm and λ ₃ : 1310 nm is selected. Since both figures show a basic multilayer structure of the optical recording medium, the wavelength of the semiconductor laser is, for example, λ ₁₁ ,
λ ₂₁ : 650 nm, λ ₁₂ and λ ₂₂ : 830 nm will be adopted.

Here, as the dye having an absorption wavelength that matches the wavelength of laser light of 650 nm, the dye having the number of methine groups —CH═CH— forming the connecting chain between the ring parts in the structural formula of the above cyanine dye is 2 As the dye corresponding to the wavelength of 830 nm of the laser light, those having 3 methine groups are selected. Then, each of these dyes is atomized to increase the specific surface area of the dye particles, expand the light absorption-heat generation area, and improve the dispersibility by improving the wettability by the dispersion medium. Then, the finely divided pigment as a main component, and if necessary, a developer,
Add an adhesive or the like and dissolve or suspend with a dispersion medium to form a paint. In this case, it is necessary that the paint-forming auxiliary agent added to the pigment as the main agent is one that does not impair the light absorption-exothermic properties and color developability of the pigment.

Next, as shown in FIG. 1 and FIG. 2, a transparent resin plate or a transparent glass plate provided with light scanning guide irregularities on one surface is used as a transparent film forming substrate 11, and the guide irregularities are formed while the substrate is rotated at a high speed. The coating material prepared as described above is dropped and applied on the provided surface and dried to obtain the first medium layer 12 directly formed on the transparent film forming substrate 11. Subsequently, another kind of paint is applied to the first medium layer in the same procedure as above.
The second medium layer is applied by dropping and applying it on the 12th surface and drying it.
A master plate for optical discs and optical cards is obtained by laminating 13 and providing a recording medium layer 14 of a sequentially laminated type in which the interface between both media is clearly understood.

The thickness of the coating film shown here is 0.1 μm or less, so the variation of the film thickness within the plane of the disk or card obtained by cutting from a thick plate is ± 0.01 μm with respect to the specified value. It is necessary to keep it within the range.

When forming a laminated medium with a coating film, a paint solubilizer is essential, but its effect is unavoidable in successive lamination, and a clear dye interface cannot be formed if left alone. Therefore, in the present invention, a thin layer (not shown) of a so-called 2P resin having a thickness of 0.05 μm, which is optically negligible, is provided between the dyes.

As a method of light irradiation recording and reading on an optical recording medium such as an optical disk or an optical card obtained as described above, as shown in FIG. Second-part recording of multiple layers recorded in
As shown in the figure, there is multi-layer same-site recording in which only the dye film is recorded differently on either the convex portion or the concave portion. In order to perform the recording and the reading of the returned light, an optical system capable of combining and separating a plurality of kinds of light having different wavelengths as shown in FIG. 4 is required.

In the recording of another portion shown in FIG. 1 described above, a low wavelength light 123 having a wavelength of λ ₁₁ is similarly formed on the convex portion viewed from the light irradiation surface, that is, the concave portion, on the first medium layer 12 formed on the short focal plane. In other words, high-wavelength light of wavelength λ ₁₂ is formed on the second medium layer 13 formed on the long focal plane.
Irradiate 133 each. To give an example of light irradiation, first, the irradiation light is emitted using a plurality of types of laser diodes (not shown) with different oscillation light wavelengths as light sources, respectively, and is combined by a dichroic prism (not shown) via a collimator lens. 4 in FIG. 4 (b)
2. The light enters the longitudinal and lateral bidirectional optical axis asymmetric chromatic aberration lenses as indicated by reference numeral 43 in FIG. Here, the vertical and horizontal optical axes are different for each wavelength, and the lens 42 has a reference numeral 42.
The lens 43 focuses on the points 1 and 422 and the points 431 and 432, respectively. Then, if these focal points are in the first medium layer 12 and the second medium layer 13 described above,
The first medium layer 12 is irradiated with light 123 having a wavelength of λ ₁₁ to form recording marks 122, and the second medium layer 13 is irradiated with light 133 having a wavelength of λ ₁₂ to form recording marks 132. It

Further, in the recording of the same portion as shown in FIG. 2, recording may be performed in a convex portion or a concave portion when viewed from the light irradiation surface, but in FIG. 2, recording is performed in a concave portion, a so-called guide groove portion. It shows the situation. Then, the first medium layer 12 has a wavelength of λ ₂₁
Of the first medium layer 12 to irradiate the second medium layer 13 with the first medium layer 12
The light 233 having a wavelength of λ _{22 that} has passed through is emitted. To give an example of light irradiation, first, the irradiation light is emitted using a plurality of types of laser diodes (not shown) with different oscillation light wavelengths as light sources, respectively, and is combined by a dichroic prism (not shown) via a collimator lens. Then, the light enters the longitudinal optical axis asymmetric chromatic aberration lens as indicated by reference numeral 41 in FIG. 4 (a) and reference numeral 44 in FIG. 4 (d). Here, the vertical optical axis is different for each wavelength, and the lens 41 forms images at points 413 and 414, and the lens 44 forms images at points 441 and 442.
Then, if these image forming points are located in the first medium layer 12 and the second medium layer 13 described above, the first medium layer
12 is irradiated with light 223 having a wavelength of λ ₂₁ to form a recording mark 222, and the second medium layer 13 is irradiated with light 233 having a wavelength of λ ₂₂ transmitted through the first medium layer 12 and recorded. Traces 232 are formed.

In order to read information from the recording marks generated after the recording is completed as described above, for example, the recording marks 222 and 232 shown in FIG. 2, the recording marks 222 and 232 are irradiated with light of reduced intensity in the same procedure as the recording. , The weak return light due to the reflection from the recording marks 222, 232 is read. That is, the recording light, for example, the power of the laser light 223, 233 is about 10 mW at the oscillation output of the laser diode, the reading light is about 1/3 of it is 3 mW, and the reflected return light from the recording marks 222, 232 is. Since it is derived from the light reflectivity of the recording marks 222 and 232, it is further reduced, and becomes equivalent to 0.5 mW to 0.8 mW in terms of electric output.
This means that in the first and second medium layers 12 and 13, the light absorptivity of the medium film is reduced by the light irradiation, and the light reflectance is about 10%.
The reason is that the wavelength of irradiation light is increased to 20% to 30%, and the wavelength of irradiation light is mismatched due to the shift of the selective absorption wavelength for the same reason as the change in reflectance. However, if the power of the returning light is equivalent to 0.5 mW to 0.8 mW, it can be said that the value is practically sufficient. Regarding the irradiation light for reading the recording mark 232 of the second medium layer 13 and the reflected return light from the recording mark, the first medium film 12 is the recording mark 222 or the unrecorded portion 121. Randomly passing without distinction, it reaches the recording mark 232 of the second medium layer 13, and the reflected light returns in the same manner. Here, the recorded mark 222 of the first medium layer 12 and the unrecorded portion 121 have different light transmittances depending on the wavelengths. If this difference is large, the first medium layer 12
The amount of irradiation light to the second medium layer 13 and the amount of return light from the second medium layer 13 will vary depending on the transmission location of the light. It is a difference within a functional range, and the above-mentioned fluctuation can be ignored or dealt with by electrical processing of the returning optical signal as necessary.
It should be noted that, in the recording and reading of another portion as shown in FIG. 1, the above-mentioned situation where the laser beam passes through the first medium layer 12 does not occur.

Hereinafter, detailed conditions and situations will be described with specific examples.

Example 1 This example is based on the procedure outlined above in FIG. First, as irradiation light, wavelengths λ ₁₁ : 650 nm, λ ₁₂ : 830
nm, and the corresponding dye is the first medium layer
The above-mentioned cyanine dye having a methine group number of 2 is used for 12 and the cyanine dye having a methine group number of 3 is used for the second medium layer 13, and these are used as main components to form a paint, On one side with a pitch of 1.5μ
As a transparent film-forming substrate 11, a press-molded polyester film in which a guide groove was formed in a spiral shape having an inner concave width of 0.8 μm was coated and formed. First, apply the second medium layer 13,
A thin film of a photopolymerizable resin, a so-called 2P resin, was formed thereon and then sequentially laminated and coated in the order of the first medium layer 12. In addition,
The 2P resin thin film is formed by spin coating, but since the existence of the 2P resin thin film can be ignored optically, the following description is omitted. The thickness of the coating film is 0.08 μm on average of the coated surface. In the present embodiment, the substrate is rotated and the coating material is dropped and applied on the surface thereof, but it may be continuously applied on the surface of the raw film by the roll coating method.

The disk original plate obtained as described above is sized to have a predetermined size and shape, and as shown in FIGS. 1 and 4 (b), it is convex when viewed from the light irradiation surface of the transparent film forming substrate 11. The first medium layer 12 formed in the portion has a wavelength λ ₁₁ : 650
The first information by the irradiation light 123 of nm, and the second information by the irradiation light 133 of wavelength λ ₁₂ : 830 nm on the second medium layer 13 formed in the concave portion when viewed from the light irradiation surface, respectively. Recorded. Here, the light beam was 0.7 μm on the image plane, and the oscillation outputs were λ ₁₁ light: 6 mW and λ ₁₂ light: 10 mW. The amount of irradiation light was controlled so that the temperature was raised so that the medium layer was not deformed due to the melting or softening of the dye.

In addition, recording marks 122, 12 carved in the medium layer by light irradiation.
The return light due to the reflection from 3 was read by the same procedure as recording, with the irradiation light amount reduced to λ ₁₁ light: 2 mW and λ ₁₂ light: 3 mW. And the return light is λ ₁₁ light: 0.3m
W, λ ₁₂ light: 0.3 mW. In addition, the amount of noise due to the interference between the λ ₁₁ light and the λ ₁₂ light is very small, which is not a practical obstacle.

Example 2 A disk formed by forming the same coating medium as that used in Example 1 was used, and the disk was formed in the concave portion of the transparent film forming substrate 11 as shown in FIGS. 2 and 4 (a). Being the first
Of the first medium by irradiating the medium layer 12 with light having a wavelength of λ ₂₁ : 650 nm, and the second medium layer 13 of the same portion has a wavelength of λ ₂₂ : 830 nm.
And the second information was recorded. The conditions of light irradiation during recording are the same as in Example 1 except that the optical system shown in FIG. 4 (a) was used. The condition of the recording body thus obtained is as schematically shown in FIG. In the case of the present embodiment, it is inevitable that a portion in which the information 1 and the information 2 are individually recorded and a portion in which the information 1 and the information 2 are recorded in a superimposed manner coexist.

In addition, recording marks 222, 23 engraved on the medium layer by light irradiation
Regarding the reading of the return light due to the reflection from 2, the irradiation light quantity was reduced to λ ₂₁ light: 2 mW and λ ₂₂ light: 3 mW in the same procedure as recording. At this time, the λ ₂₂ light having a long wavelength reaches the second medium layer 13 through the layer in which the recording mark 222 of the first medium layer 12 and the unrecorded portion 121 coexist, and the recording mark 232 of the film. Reflected by
The returning light returns to the optical system 41 through the first medium layer 12 in the direction opposite to that at the time of incidence. Here, the presence of the first medium layer 12 is a disturbance factor, but in reality, the first medium layer 12 is present.
The light transmittance for the λ ₂₂ light in the portion where the recording mark 222 is formed is reduced by several to 10% from that in the unrecorded portion 121 to cause a decrease in the light amount of the light passing through the medium layer, but practically, The return light due to the above-mentioned light irradiation is equivalent to 0.1 mW, the noise amount is weak, and it is within a range that can be sufficiently dealt with electrically. The recording mark 222 of the first medium layer 12
The amount of light (λ ₂₁ light) returned from was about 0.3 mW.

〔The invention's effect〕

According to the present invention, in an optical recording medium prepared by laminating a plurality of types of films each having a dye having a different absorption wavelength as a main component, the plurality of types of films are formed by coating films, respectively, By providing a thin layer of the photopolymerizable resin between them, the laminated medium can be stably formed, and the performance of the laminated film itself can be prevented from deteriorating.

[Brief description of drawings]

FIG. 1 and FIG. 2 are perspective schematic views showing an optical recording medium according to the present invention, a method of performing multiple recording on the optical recording medium by irradiating different regions of light and irradiating the same region of light, and the state of recording marks formed thereby. FIGS. 3A and 3B are schematic perspective views showing a conventional recording method and a state of recording marks formed by the conventional recording method,
FIG. 4 is a principle diagram of an asymmetric chromatic aberration lens used for combining and distributing a plurality of lights having different wavelengths in the embodiment of the present invention. DESCRIPTION OF SYMBOLS 11 …… Transparent film-forming substrate 12 …… First medium layer 13 …… Second medium layer 14 …… Recording medium layer 121 …… Unrecorded area 122,132,222,232 …… Record mark

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Teijiro Kitao 4-804 Mozumoumecho, Sakai City, Osaka Prefecture Osaka Department of Applied Chemistry, Faculty of Engineering, Osaka Prefecture University (72) Ichiro Ichi, 1 Shimohozumi, Ibaraki City, Osaka Prefecture No. 1-2 Nitto Denko Corporation (72) Inventor Ken Noda 1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto Denko Corporation (56) References JP 62-167088 (JP, A) ) JP-A-59-152528 (JP, A) JP-A-51-138403 (JP, A)

Claims (1)

(57) [Claims] 1. An optical recording comprising a substrate and a plurality of types of films each having a dye having a light absorption wavelength in the visible light region to the near infrared light region and having different absorption wavelengths as a main component. In the medium, an optical recording medium characterized in that each of the plurality of types of films is formed by a coating film, and a photopolymerizable resin thin layer is provided between the coating films.