JPS58224793A - Optical recording medium - Google Patents

Abstract

PURPOSE:To obtain a chemically stable optical recording medium having a high sensitivity in the wavelength range of semiconductor lasers, by providing an organic film as a recording layer containing 2,3-dicyano-1,4-naphthoquinone as a main component on a substrate. CONSTITUTION:An organic thin film containing a naphthoquinone dye [e.g., 5-amino-2,3-dicyano-8-(4'-butylanilino)-1,4-naphthoquinone] as a main component of formula I (wherein R is OH, NH2, or NHX and R' is OH, NH2, or a group of formula II, where X is an alkyl and X' is H, an alkyl, or allyl) is formed on one or both sides of a substrate by a resistance heating and vapor deposition method, etc., to obtain an objective recording medium.

Description

[Detailed Description of the Invention] The invention relates to an optical recording medium on which information can be recorded and reproduced using a laser beam, and more specifically, an optical recording medium that uses a change in the state of matter by optical energy at the oscillation wavelength of a semiconductor laser to perform recording. Regarding recording media.

Conventionally, Te alloys, Te oxides, bubble-forming media, organic dyes, and the like have been used as optical recording media of this type.

A Te alloy is used as a solid solution association of Te and a semiconductor such as As or Se. This medium has relatively high writing sensitivity and is suitable for use with semiconductor lasers, which can make the optical system for recording and reproduction compact, but it is chemically unstable and easily deteriorates when left in the air. Materials (Te, A
s, Se, etc.) are toxic.

Although Te oxide is stable due to Te subassociation, its optical properties, such as absorption and reflectance, are sensitive to the oxidation state. Therefore, this medium has the disadvantage that the oxidation state must be tightly controlled during the formation of the medium.

The bubble-forming medium has a three-layer structure consisting of an anti-tN layer, a transmission layer, and an absorption layer, and it uses repeated reflection interference to increase the light absorption rate and achieve high sensitivity. Therefore, this medium is currently the most sensitive medium. The disadvantage of the medium is that it requires a large number of film formations due to its multilayer structure, and that the repeated reflection interference is highly dependent on the thickness of each layer, so the olfactory thickness must be strictly controlled during odor formation. Organic dye media have been developed in various forms.

They can be roughly divided into single dye types and compatible types in which the dye is dissolved in a polymer resin using a solvent. A compatible medium is, for example, as disclosed in JP-A-55-161690, in which polyvinyl acetate, which is a polymeric resin, is mixed with polyester yellow as a dye using a solvent, and the medium is formed on a substrate by a spin coating method. Ru. This medium exhibits absorption in a relatively short wavelength region (400 to 500 nm), but has almost no absorption in the semiconductor laser wavelength region (~800 nm), so it cannot be used as a medium for recording devices that use semiconductor lasers. I can't. In addition, generally compatible media are:
If the medium forming method is limited to solvent coating and a resin is used, there is a restriction that a solvent that does not ferment the resin must be selected. On the other hand, as a color 11 type medium, for example, a medium in which a squarylium dye is formed by a vapor deposition method is disclosed in JP-A-56-46221. This dye has a relatively large absorption in the near-infrared wavelength region, which is the oscillation wavelength of a semiconductor laser, and its recording sensitivity is worse than that of Te alloy. An object of the present invention is to provide an optical recording medium that is highly sensitive and chemically stable in the wavelength region of a semiconductor laser.

In other words, the present invention provides a recording layer on one or both sides of a substrate, and as a C1 recording layer (the formula is 01-1. NH2, NHX) in an optical recording medium in which information is recorded and read by a laser beam. or represents NX2, 几′it 0)-I, N)Iz, NHX
, NX2 also +s NHGX'E 'ah t.

(Here, X represents an alkyl group, and X' represents a hydrogen atom, an alkyl group, an allyl group, an amino group, or a substituted amino group.) Features. The naphthoquinone dyes represented by the above general formula are collectively called 2,3-dicyano-1,4-naphthoquinone, and the absorption peak wavelength shifts from the visible region to the infrared region depending on the type of auxochrome JR' at the 5.8 position. All of the auxochromes R and R' mentioned above have absorption peak wavelengths in the infrared region, but in the above general formula, R is NH2, IL' is N H-Q- A compound in which X' is a radical is most compatible with the oscillation wavelength of a semiconductor laser, and a compound in which Xl' is an alkyl group is most preferable considering other conditions.

For example, 5-amino-2,3-dicyano-8=(
When 4-butylanilino)-1,4-naphthoquinone is measured in an acetone solvent, it is found that the absorption maximum wavelength of the spectrum of this dye is λ"aX LJ 759 nm, which matches well with the oscillation wavelength of a semiconductor laser.

The naphthoquinone dye compounds are stable under relatively high range, high humidity environmental conditions and do not exhibit deterioration due to air oxidation as Te alloys 0) do. This means that it can withstand long-term use without a protective film. In addition, this compound has the same low thermal conductivity as general organic dyes,
Its value is 1/10 to 1/100 of metal. Therefore, there is less heat diffusion in the medium during laser beam recording.
, the temperature of the medium in the light irradiation section can be efficiently raised.

The recording medium is formed by attaching the above naphthoquinone dye to one or both sides of a substrate by vapor deposition or solvent coating. Although various substrate materials can be used, glass, AI, and synthetic resin are generally preferred. Examples of synthetic resins include polymethyl methacrylate (PMMA), polyvinyl chloride (PvC), polysulfonate, and polycarbonate. The substrate shape can be a disk shape, a tape shape, or a sheet shape.

When the single naphthoquinone dye film formed on the substrate is irradiated with semiconductor laser light while being absorbed by a lens, the dye film in the irradiated area is removed 71. 11. Ru. Although the mechanism of this pore formation is not clear, it is thought to be due to melting and aggregation accompanied by evaporation (premature blooming). The size of the hole formed depends on the focused diameter of the laser beam, the laser power, and the irradiation time ζ, but it is preferably about 0.2 to 3 μm. The laser energy required to form such holes is small;
Therefore, holes can be formed in a short time. in particular,
When an AlGaAs semiconductor laser beam with a wavelength of 830 nm has a beam diameter of 1.4 μm and 3 ThL, the power on the dye film surface is 2 to 10 mW.

The pores can be formed with the irradiation time in the range of 50 to 3 Q Q n5eC. Of course, holes can be formed under conditions that exceed the upper limits of the power or irradiation time above, but the above conditions are the desired flexibility of use. This is done by making the disc-shaped medium correspond to the following. - Information is recorded by rotating an ordinary disc-shaped medium at a constant speed and forming holes that meet the recording layer.

In addition, in the above case U), the thickness of the pigment film is 0.01~
0.5 μm, preferably 0.02 to 0.2 μm.The information (holes) recorded in this way can be read by detecting changes in the luminous intensity of the reflected light or transmitted light Cυ from the medium. Generally, a method of detecting reflected light is adopted.The reason for this is that the optical system is simpler when detecting reflected light.In other words, it is possible to emit and focus light in one optical system. This is because light is possible.Reading is performed by continuously irradiating laser light.The light intensity at that time is set to a weak energy that does not cause any shape change to the medium, and is 115 to 1/1O of the light intensity during normal recording. It is.

As the incident direction of light during recording and reproduction, the medium surface 11! II
There are two ways: and on the board side. *With one single layer medium as in the example, it is also possible to arrange it in both directions. With 1N incidence on the substrate surface side, recording and reproduction are possible without being affected by dust attached to the medium surface, which is a more desirable form.

Note that defects such as dust attached to the substrate surface opposite to the surface on which the medium is formed and scratches on that surface (well, if the substrate thickness is one or more times, the beam diameter on that surface is sufficient) Information that is large enough to not adversely affect recording and reproduction is recorded as a hole array.

In general, the hole rows form a large number of concentric or spiral tracks, and when reproducing, the light beam needs to accurately track the hole rows of a specific track. One way to achieve this is to increase the accuracy of the rotating mechanism by using air bearings, etc. However, in this case,
The rotation system becomes complicated and expensive, so it is impractical (unwise to do so. It is more desirable to have a guide groove for cloudy light on the substrate. When light enters a groove with the diameter of the beam, the light The spatial distribution of the diffracted light intensity differs as the center of the beer shifts from the groove, and a servo system can be configured to detect this and direct the beam to the center of the groove. The width is 0.6 to 1.2 μm.

The depth is set within the range of 1/8 to 1/4 of the recording/reproducing wavelength used. The recording layer is therefore formed on the grooved substrate surface.

A thin pattern of 2,3-dicyano-1,4-naphthoquinone dye can be easily formed by a conventional resistance heating vapor deposition method. 71.Kept at room temperature. When a thin layer 1i1;j is formed on a substrate, its crystallinity becomes amorphous, that is, it becomes amorphous. Since the reflected light from the amorphous layer does not include the grain boundary noise seen in a single polycrystal layer, the reproduction S is good when an amorphous layer is used.

The present invention will be described in detail below with reference to the drawings. Figure 1 shows the actual formation of 5-amino-2,
This figure shows the absorption spectrum of 3-dicyano-8(4-butylanilino)-1,4-naphthoquinone dye in a thin line. From this, it was confirmed that there is a thick absorption near ~800 nm, which is the excavated wavelength of GaAs semiconductor laser, and that this dye is suitable as an optical recording medium using a semi-quadram body laser.Next 1.5 on a disk-shaped PMMA substrate with a thickness of 2+++m
~Amino-2,3-dicyano-8-(4-butylanilino)-1,4-naphthoquinone dye was vapor-deposited by resistance heating method to obtain a film with a thickness of 550A (/J).The resistance heating boat material was M
O, and the degree of vacuum before and during vapor deposition is 6
10' Torr, 9 x 10' Torr.

The substrate was left to stand naturally at room temperature, and almost no increase in substrate humidity due to vapor deposition was observed. When the boat temperature is gradually raised, the dye melts at 220°C, and is then fixed at this temperature for vapor deposition. The deposition rate (about 5 A/sec).

FIG. 2 shows the medium 1 formed in this way. A dye 20 is formed on the PMMA substrate 10. A wavelength 83 Q is applied to this medium 1 from the direction of the arrow 30.
nm semiconductor laser light was focused by an optical system (not shown) and irradiated. In this case, the laser beam has a power on the medium surface of 2~
The experiment was carried out under the conditions of 12 mW and 50 to 300 nsec of irradiation time. The recording sensitivity at this recording wavelength was about 16 mJ/cA. According to this recording, about 0.9 μm in the pigment film 20
A hole 40 with a diameter of 1° was formed. Such recording was similarly possible even if the light was incident through the substrate 1'0, that is, from the direction of the arrow 50.Similarly to the previous embodiment, R' is NH,0-1 ( 5-
Amino-2,3-dicyano-8-anilino-1,4-naphthoquinone and Each thin film was obtained by vapor depositing 1,4-naphthoquinone dye by resistance heating method.
Sublimation begins at 0°C, and the latter melts at 250°C and becomes ready for vapor deposition. When writing was performed on each film (film thickness 250A) using a semiconductor laser to determine the writing sensitivity, results similar to those of the above example were obtained.As is clear from the above example, the optical recording medium obtained by the present invention has the following characteristics: It is more sensitive than Te alloy media, easier to form, and chemically (
It can be seen that it has the distinct advantages of being stable, durable for long-term storage, and having a good reproduction S/N ratio.

[Brief explanation of the drawing]

Figure 1 shows 5-amino-,-2,3-dicyano-8-(4
-butylanilino)-1,4-naphthoquinone dye vaporized film, FIG.
0 indicates the pigment film, 30 and 50 the incident direction of light Q), and 40 indicates the hole. ri1ri no UmameE) Shocho (Le female) 2nd procedural amendment (spontaneous) 58.9.12 1. Indication of the case 1981 Patent Application No. 109
332 No. 2, Title of the invention: Optical recording medium 3, Relationship with the amended person's case Applicant: 5-33-1 Shiba, Minato-ku, Tokyo (423) NEC Corporation Representative: Tadahiro Sekimoto 4, Agent: 108 Resident Mita Building, 37-8, Shiba 5-1-me, Minato-ku, Tokyo (Contact address: NEC Corporation Patent Department) Explanation - Column 6 for brief explanation of the drawings, content of amendment 1, and the scope of claims of the specification of the present application are amended as shown in the attached sheet. 2. On page 4, line 9, k of the specification, the phrase ``yield'' is amended to ``indicates yen''. 3. In the 12th line of page 1184 of the specification, VC "optical recording medium" is corrected to "optical recording medium." 4. On page 4 of the specification, line 17 to line 19, K? 5. On page 5, line 10 of specification W, correct the statement ``all infrared region K'' to ``none.'' 6. In the specification, page 5, line 116 to line 2191 is 7,
On page 6, line 9 of the specification, the word "apologize" is amended to read "endure." 8. In the fifth line of page 7 of the specification, "light absorption" is corrected to "light absorption". 9. In the specification, on page 7, line 7, the word "early flower" is corrected to "sublimation." lOl In the first line of page 10 of the specification, the word "dicyano" is corrected to "dicyano." 11. "-8(4'-" on page 10, line 10 of the specification is corrected to "-8-(4'-J.") ν, 1 on page 11, line 4 of the specification. - Correct the phrase ``Noboru wa'' to read ``Noboru wa.'' B. Correct the phrase ``Basically vaporized film'' to ``1 elemental vaporized membrane'' in page 12, line 18 of the Meiji 1st Shoki.・ ', q, z Attachment Claims This is an optical recording medium in which a recording layer is provided on one or both sides of a substrate, and information is recorded and read by a laser beam. (Here, X is an alkyl The group X' represents a hydrogen atom, an alkyl group, an allyl group, an amino group, or a Gi-substituted 7-mino group. Characteristic optical recording media. 6. Procedural amendment (voluntary) Commissioner of the Patent Office 1. Indication of the case 1981 Patent Fraud Application No. 109
332 No. 2, Title of the invention: Optical recording medium 3, Relationship with the amended person's case Applicant: 5-33-1 Shiba, Minato-ku, Tokyo (423) NEC Corporation Representative: Tadahiro Sekimoto 4, Agent: 108 Resident Mita Building 5, 37-8 Shiba 5-chome, Minato-ku, Tokyo Column for detailed explanation of the invention in the specification subject to amendment, page 12, line 6 of the specification of contents of the amendment, 1-340'C ...] should be corrected to "at 1 to 240"C.

Claims (1)

[Claims] In an optical recording medium in which a recording layer is provided on one or both sides of a substrate, and information is recorded and read by a laser beam, the recording layer comprises: OH, NH2, NHX, NX2, or ii NH-
o)-X';f Table wa t. (Here, X is an alkyl group, y is a hydrogen atom, an alkyl group,
Represents an allyl group, an amine group, or a substituted amine group. ))
An optical recording medium characterized by forming an organic thin film containing a naphthoquinone dye represented by the following as a main component.