JPH02175284A - Optical recording medium - Google Patents

Abstract

PURPOSE:To reduce a waveform distortion and to improve a bit error by providing an optical recording layer made of a first layer containing organic dyes and a second layer of mixture of resin and organic dye on a board, and setting a bubble recording mode. CONSTITUTION:Resin for a board transmits a light for recording or reading a signal and includes, for example, acrylic resin, polycarbonate resin. A first layer is formed by dissolving organic dye in an organic solvent, coating it on a board by a spin coating method. The organic dye includes, for example, diol metal complex dye, aromatic or unsaturated fatty diamine metal complex dye, etc. A second layer is formed by dissolving resin and organic dye in an organic solvent, and coating it by a spin coating method. The organic dye includes, for example, mixture of one or more types of dyes for the first layer. The resin includes, for example, epoxy resin, urethane resin. Thus, a waveform distortion is reduced, and a bit error is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium that optically records and reproduces information.

[Prior Art] An optical recording medium has a structure in which an optical recording layer is formed on a substrate, and information is recorded and reproduced by light by irradiating the optical recording layer with a laser beam or the like.

Information is recorded on this optical recording medium by forming bits (holes) or bubbles in the optical recording layer by irradiating it with a laser beam, or by causing other physical changes. It will be done. Furthermore, information is reproduced using optical changes caused by changes in the optical recording layer as described above.

Such optical recording media have high areal recording densities and are useful for recording large amounts of data.

Manufacturing methods for optical recording media can be broadly divided into vapor deposition methods and coating methods. An optical recording medium with an inorganic recording film can only be manufactured by a vapor deposition method, but an optical recording medium with an organic recording film can also be manufactured by a coating method. The vapor deposition method requires large-scale vacuum equipment for its manufacturing process. However, the coating method does not require such equipment.

Therefore, organic optical recording media are more advantageous in terms of productivity. Even in organic optical recording media, a single-layer film structure is considered to be simple and suitable for mass production. However, in the case of an organic single-layer film, the recording layer often releases decomposed products during recording, which worsens the noise level, and it has been difficult to obtain an excellent optical recording medium as it is.

In order to overcome these drawbacks, it has been proposed to provide a layer on the recording layer to suppress the release of decomposition products, and to change the recording mode from the bit formation mode to the bubble formation mode.

In that example, the first layer is a light absorption layer and a light reflection layer, the second layer is a bubble formation layer, and the second layer has a structure that does not particularly participate in light absorption or reflection. . In other words,
It is characteristic that a bubble-forming film is simply formed on the recording layer to suppress recording decomposition products (Japanese Patent Application Laid-open No. 164037/1983). This method has the disadvantage that sometimes distorted bubbles are easily formed. Therefore, the shape of the reflected signal of information becomes distorted, and there is a possibility that a signal error may occur.

In addition, recording methods include bit-to-bit recording and bit-length recording. In particular, bit-length recording requires ■ making long holes, and ■ the length of the pits is a problem. , the trend was remarkable.

The details of the mechanism are unknown, but the material that makes up the film is N-based and has low thermal conductivity.Therefore, the first layer recording film generates heat during laser irradiation, and bubbles that do not generate heat form. This is presumed to be due to the increase in temperature gradient in the layer.

In other words, this is thought to be because the structure consists of a high-temperature, soft lower layer and a cold, hard upper layer, and even if an attempt is made to form a bubble on the upper layer, the soft lower layer deforms, causing the bubble to become distorted. .

[Basic idea] The present inventors conducted studies to improve the drawbacks of the bubble recording mode as described above while maintaining the property of not being a decomposed product, which is a characteristic of the bubble recording mode. They have also found that waveform distortion can be reduced and bit errors can be improved by including an organic dye having light absorption ability in the second layer that forms the outermost shell of the bubble during recording. We have also found that it is more desirable if the first layer thickness is thinner. This is probably due to the structure described above, which reduces the temperature gradient between the first layer and the second layer, and when the first layer decomposes and releases decomposed products, it is the most able to absorb the release pressure. The soft portion is the second layer that has become soft due to its own absorption of light, and it is therefore thought that the shape of the formed bit will be less distorted.

Therefore, by using a structure in which a first layer containing an organic dye is provided and a second layer made of a mixture of resin and organic dye is provided on top of the first layer, there is no distorted reflected signal that occurs in conventional bubble recording. This led to the completion of an optical recording medium.

That is, the present invention provides an optical recording medium having, on a substrate, an optical recording layer consisting of a first layer containing an organic dye and a second layer made of a mixture of a resin and an organic dye thereon. The present invention also relates to an optical recording medium in which the recording mode of the optical recording medium is bubble recording mode.

The present invention will be explained in detail below.

The present invention is an optical recording medium capable of recording and reading signals by irradiating a laser beam from the side of a transparent substrate, which is substantially composed of a transparent substrate and an iS layer provided on the substrate. The recording layer consists of a first layer made of an organic dye (including the case containing a binder) and a second layer made of a mixture of a resin and a organic dye, and by irradiation with laser light, This method is characterized in that recording is performed by forming a bubble.

The resin for the substrate used in the present invention is preferably one that transmits light for recording and reading signals, has a light transmittance of 85% or more, and has small optical anisotropy. 8 For example, acrylic resin, polycarbonate resin, polyester resin,
Examples include polyamide resins, vinyl chloride resins, polyvinyl ester resins, polyolefin resins, polystyrene resins, polyphenylene oxide resins, and mixed resins of these resins. Among these, acrylic resins, polycarbonate resins, polyolefin resins, mixed resins of polystyrene resins and polycarbonate resins, and polystyrene resins and polyphenylene oxide resins are preferred from the viewpoint of mechanical strength, hygroscopicity, and economic efficiency of the substrate. Preferably, polycarbonate resin is more preferable.

The substrate of the present invention may be formed by any method such as injection molding, 2P method, or extrusion molding, but injection molded substrates are preferable from the viewpoint of mass production. It may also be one that has undergone a treatment such as coating.

The shape of the substrate of the present invention may be plate-like, film-like, circular, or card-like.

The first layer film is formed on the above substrate by a spin code method (including the case where the organic dye is dissolved in an organic solvent and a binder is mixed). is desirable, more preferably 20 to 150
It is preferable to form a film in n-.

The organic dye used in the first layer is a dye that absorbs at the oscillation wavelength of the laser used for recording and is soluble in a solvent, such as a dithiol metal-based dye, an aromatic or unsaturated aliphatic dye, etc. Diamine metal complex dyes, polymethine dyes, squarylium dyes, azulene dyes,
Naphthoquinone dyes, anthraquinone dyes, porphyrins, phthalocyanines, macrocyclic azaannulene dyes such as naphthalocyanine, quinonoid dyes, triallylmethane dyes, etc. may be used alone or in combination of two or more. At this time, additives may be used, for example, in order to improve sensitivity and film-forming properties, within a range that does not impair the effects of the present invention.

Specific examples of such additives include various polymers, saturated hydrocarbons with relatively low boiling points, unsaturated hydrocarbons,
Examples include low molecular weight substances such as chlorinated hydrocarbons, aromatic hydrocarbons, esters, ethers, polyhydric alcohols, and nitric esters. These may be used alone or in combination of two or more.

Solvents for applying organic dyes (including cases where additives are mixed) include hydrocarbon solvents such as hexane, hexene, octane, octene, decane, cyclohexane, cyclohexene, and methylcyclohexane; fluorinated hydrocarbon solvents, and diethyl. Ether solvents such as ether, dipropyl ether, dibutyl ether, diethyl ether, ethylene glycol dimethyl ether, alcohol solvents such as methanol, ethanol, propyl alcohol, butyl alcohol, pentyl alcohol, hexyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monomethyl ether, etc. Glycol ether solvents such as ethyl ether, toluene, xylene, ketones, esters,
Examples include chlorinated hydrocarbon solvents and solvents containing water as a main component. These solvents may be used alone or in combination of two or more.

Next, the second layer of the mixture of the resin and the organic dye is formed by dissolving the resin and the organic dye in a solvent and applying the spin code method onto the substrate on which the first layer is formed.

The film thickness is desirably 40 to 300 nm, more preferably 40 to 140 nm.

Like the organic dye used in the first layer, the organic dye used in the second layer is a dye that has absorption at the oscillation wavelength of the laser used for recording and is soluble in a solvent. Examples of the dyes include the f-type dyes described in Section 1, and each may be used alone or in a mixture of two or more types.

Examples of the resin used in the second layer of the present invention include resins such as epoxy resin, urethane resin, phenol resin, urea resin, organic polysiloxane resin, polyimide resin, unsaturated resin, and ultraviolet curing resin. Among these resins, organic polysiloxane resins are preferred from the viewpoint of solubility and durability.

Examples of more preferable organic polysiloxane resins include R
11bSi(ORi)z−m(X) a Te represented 2
Functional silanes and trifunctional silanes represented by R45I(ORs)3-, (X) a and 5i(ORJ b (X)a-
Tetrafunctional sila 7 (R.

, Rt, R,, R4, R6, represent an alkyl group or an aryl group, X represents a hydroxyl group or a halogen, mouth is 011 or 2, ugly is 0, 1.2 or 3, h is 0 .1
, 2.3 or 4), and is an organic polysiloxane resin formed by condensing R1, R2, R3, Ra, R, and R
Specific examples of 4 include alkyl groups such as methyl group, ethyl group, propyl group, butyl group, hexyl group, octyl group, and cyclohexyl group, and aryl groups such as phenyl group, methylphenyl group, naphthyl group, and benzyl group. It will be done. Furthermore, specific examples of halogen include chlorine, bromine, and iodine. The types of these substituents in one molecule may be the same or different.Furthermore, these bifunctional, trifunctional silanes and tetrafunctional silanes may each contain one type or 211M
A mixture of the above may be used.

The mixing ratio of the organic dye and resin can be from 0.1 to 4.0 of the resin to the organic dye 1, preferably from 0.3 to I55, and more preferably from 0.5 ~
The optimum mixing ratio of these, preferably 1.5, depends mainly on the properties of the dye, and there is no specific mixing ratio for any dye.

Examples of the solvent for coating the second layer include hydrocarbon solvents such as hexane, hexene, octane, octene, decane, cyclohexane, cyclohexene, methylcyclohexane, fluorinated hydrocarbon solvents, diethyl ether, dipropyl ether, Ether solvents such as dibutyl ether, diethyl ether, ethylene glycol dimethyl ether, methanol, ethanol, propyl alcohol,
Alcohol solvents such as butyl alcohol, pentyl alcohol, and hexyl alcohol, glycol ether solvents such as ethylene glycol monomethyl ether and ethylene glycol monoethyl ether, toluene, xylene, ketone solvents, ester solvents, chlorinated hydrocarbon solvents, etc., and water. Examples include solvents whose main components are These solvents may be used alone or in a mixture of two or more, provided, however, that they do not damage the first layer.

[Preferred form for carrying out the invention! ! The present invention will be specifically explained below using examples, but the embodiments of the present invention are not limited thereto.

Example 1 Vanadyl was applied to an injection molded polycarbonate resin substrate having a spiral guide groove with a thickness of 1Jmm and a diameter of 1301mm.
After dropping a 2% by weight hexane solution of tetraoctylnaphthalocyanine dye, the resin substrate was heated to 200 rpm.
The first layer was formed by rotating for 10 seconds at a speed of
After dropping L weight % of an organic polysiloxane resin with an average molecular weight of 500 preliminarily condensed with 741% triethoxysilane and a 1 weight % methanol solution of a polymethine dye, the mixture was rotated again at a speed of 2000 rpm for 10 seconds. Then, a second layer was formed to produce an optical recording medium.

This optical recording medium has a pulse width of 500r++c, a writing duty of 1/4, a linear velocity of 5.5m, and a writing power of 9.
After recording at Soga, I read out the recorded signal.

When we measured the waveform and the differential waveform, we found that both waveforms had no distortion. The bit shape was also measured using an electron microscope, and distortion-free focus was observed.

Comparative Example 1 Vanadyl-tetraoctylnaphthalocyanine dye was applied to an injection molded polycarbonate resin substrate having a spiral guide groove with a thickness of 1.2 mm and a diameter of 130 mm. ! After dropping the % hexane solution, this resin substrate was heated to 200%
The first layer was formed by rotating at the speed of Orpm for 10 seconds. Next, 30!1% of diphenyl-jethoxysilane and 70% by weight of phenyl-triethoxysilane were pre-coated with 6% of the weight of phenyl-triethoxysilane.
After dropping a 1% by weight methanol solution of an organic polysiloxane resin having an average molecular weight of 500 condensed with 11, 2
The second layer was formed by rotating at a speed of 000 rpm for 10 seconds to produce an optical recording medium.

This optical recording medium had a pulse width of 500 nm, a writing duty of 1/4, a linear velocity of 5.5 s/s, and a writing power of 9a.
After recording with w, the recorded signal was read out. When we measured the waveform and the differential waveform, we found that both had distorted waveforms. Furthermore, when the pit shape was measured using an electron microscope, teardrop-shaped bits were observed, and it became clear that the first part to be written had a large bulge.

Comparative Example 2 Thickness 1. ．． A 5% by weight hexane solution of vanadyl-tetraoctylnaphthalocyanine dye was dropped onto an injection molded polycarbonate resin substrate having a spiral guide groove with a diameter of 2 mm and a diameter of 130 mm.
The first layer was formed by rotating at a speed of 0 rpm for 10 seconds, then diphenyl-jethoxysilane 30fUj1
% and phenyl-triethoxysilane 711% were precondensed in advance, 1% by weight of an organic polysiloxane resin with an average molecular weight of 500, and a 1ffif% methanol solution of a polymethine dye were added dropwise, and then the mixture was heated again at a speed of 2000 rpm for 10 seconds. It was rotated to form a second layer to produce an optical recording medium.

This optical recording medium had a pulse width of 500 nm, a writing duty of 1/4, a linear velocity of 5.5 m/s, and a writing power of 91 nm.
After recording, the recorded signal was read out. When we measured the waveform and the differential waveform, we found that both had slightly distorted waveforms. Furthermore, when the bit shape was measured using an electron microscope, a teardrop-shaped bit was observed, and it became clear that the first part of the bit to be written was slightly swollen.

(Effects of the Invention) In the optical recording medium of the present invention, waveform distortion is reduced and focus error is improved by including an organic dye having light absorption ability in the second layer. Further, if the first layer is thin, the optical recording medium is more desirable and excellent.

Claims (2)

[Claims] (1) An optical recording medium comprising, on a substrate, an optical recording layer consisting of a first layer containing an organic dye and a second layer made of a mixture of a resin and an organic dye thereon. (2) The optical recording medium according to claim 1, wherein the recording mode of the optical recording medium is a bubble recording mode.