JPS63237232A - Optical recording medium and its production - Google Patents

Abstract

PURPOSE:To improve long-term preservable stability, to obviate deterioration in characteristics even at and under a high temp. and high humidity, and to increase a contrast ratio by laminating plural thin chemically vapor-grown films on a base in superlattice structure in such a manner that said films have an eutectic point with adjacent layers. CONSTITUTION:The thin chemically vapor-grown film layers 2 laminated on the base 1 form the superlattice structure laminated alternately with 4 layers of Zm films 21 and Ge films 22 which are grown films of metals, nonmetals or alloys. A part 30 of the laminate 2 provides a region 2' where the superlattice structure is annihilated when a light beam 3 is projected to this part. Said region can be utilize as an optical information bit, since the optical characteristics in this part are different. The region 2' is deformed to form a recess or hole part when the energy of the light beam is increased. This part acts as an optical information bit. The optical recording medium which has the excellent long-term preservable stability, decreases the deterioration in the characteristics even at and under a high temp. and high humidity and has the large contrast ratio at the time of recording is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical recording medium for recording and reproducing information using a light beam, and a method for manufacturing the same.

(Prior art) In recent years, optical recording media that are capable of high-density recording have become widespread, but the recording layer provided on these optical recording media is: ■To, Te-based alloys, or organic This type consists of a pigment, and when irradiated with a light beam, holes are formed to record information; or it is made of a Te-based compound, which undergoes a phase transition between amorphous and crystalline when irradiated with a light beam; A typical example is a type in which information is recorded using the difference in light reflectance between the crystal and the crystal.

However, since recording is performed on the above-mentioned recording medium using the heat of irradiation with a light beam, the material used for the recording layer is required to have a low melting point or a low phase transition point, and in order to meet this requirement, it is easily oxidized. Te and unstable organic substances are used, which causes problems such as lack of long-term storage stability and deterioration of properties in hot and humid environments.

In order to solve this problem, various studies have been conducted using materials with excellent stability as the recording layer.

One of these is research into forming a recording layer by laminating a plurality of stable metals or alloys.

For example, Japanese Patent Laid-Open No. 58-155541 discloses that the problem of stability is solved by laminating a metal and a metal different from the metal or Ge to form a recording layer, and information is recorded by using a laser on the recording layer. A recording medium has been provided that takes advantage of the fact that optical properties change due to mixing or alloying of two metal layers or interdiffusion of those layers by irradiation.

In addition, Japanese Patent Application Laid-Open No. 60-226039 discloses that the problem of stability is solved by alternately laminating ultra-thin films made of a plurality of different metals to form a recording layer, and information is recorded by irradiating a laser. A recording medium is described that takes advantage of the fact that optical properties change due to alloying.

(Problems to be Solved by the Invention) However, in the above-mentioned JP-A-58-220794 and JP-A-60-226039, the thin film of the recording layer is formed by sputtering or vapor deposition. In a stack of thin films produced by the laminate method or vapor deposition method, the metal atoms constituting the two layers at the stack interface become more mixed with each other, making it difficult to have a rapid change in atomic composition between the cross-sectional directions at the stack interface. . As a result, in a stack of thin films formed by sputtering or vapor deposition, the change in optical properties before and after recording by light beam irradiation cannot be made sufficiently large, resulting in a problem that the contrast ratio of recording is low.

Furthermore, when forming a laminate of two or more types of thin films by sputtering or vapor deposition, two or more metal evaporation sources or sputter cathodes are prepared, and during forming, the base material is evaporated from these two or more types. It is necessary to move between sources or sputter cathodes at high speed, which makes the equipment used complicated and there are problems in that the reproducibility of manufactured products is also poor.

(Purpose of the Invention) The present invention has been made to solve the above problems, and has excellent long-term storage stability, with little deterioration of characteristics even in high temperature and humidity environments (and a low output light beam is sufficient An object of the present invention is to provide an optical recording medium which has a degree of anger that can be recorded in a range of 1 to 30 degrees and has a high contrast ratio during recording.

(Means for solving the problem) As a result of various studies, the present inventors have found that if a thin film of two or more metals, nonmetals, or alloys having eutectic points is formed by chemical vapor deposition, A sharp change in the composition distribution in the cross-sectional direction can be formed in the cross section of a thin film laminate, and if this is irradiated with a light beam, the optical properties will change significantly before and after the irradiation, making it possible to use it as an excellent recording medium. The present invention was completed by discovering the following.

That is, the first aspect of the present invention is to provide metal on a support,
The gist of the present invention is an optical recording medium characterized in that a plurality of chemical vapor deposition thin films made of nonmetals or alloys are laminated in a superlattice structure so as to have eutectic points with adjacent layers. The second invention is to form a recording layer with a superlattice structure by laminating a plurality of thin films made of metals, nonmetals, or alloys on a support by chemical vapor deposition so that they have eutectic points with each other. The gist of the present invention is a method for manufacturing an optical recording medium characterized by the following. The gist of the present invention is an optical recording medium characterized in that a plurality of chemical vapor grown thin films are stacked on a base material so that adjacent layers have eutectic points.

(Function) -S-wise, a vapor deposition method or a sputtering method is used as a means for producing a thin film.

In either of these methods, the vapor or particles of the adhering substance that adheres to the substrate have energy reaching from 1,000 to tens of thousands of degrees, so they move violently on the substrate surface, resulting in a thin film formed in the form of islands or networks. or they can diffuse into the thin film already formed on the substrate surface, causing a rearrangement of the surface atomic layers.

Therefore, when thin films of two or more metals with a thickness of several to several tens of layers are alternately laminated using this method, the composition distribution in the cross-sectional direction is such that the two adjacent metals are mixed at the interface and have a clear distribution. cannot form an interface. For this reason, even if such a laminate is alloyed by irradiating it with a light beam, it is not possible to obtain a large change in optical properties before and after the irradiation.

In contrast, the present invention uses a chemical vapor deposition film.

A chemical vapor deposition film is a thin film produced by chemical vapor deposition.

In the chemical vapor deposition method, externally applied energy is used to decompose the raw material gas, and thin film growth progresses through chemical reactions. There is little rearrangement of the atomic layers, and a uniform thin film is formed.

Therefore, the composition distribution in the cross-sectional direction of a stacked body composed of two or more types of chemical vapor deposition films has a steep change in the cross-sectional direction without mixing of two adjacent metals at the interface. Therefore, when this laminate is irradiated with a light beam, a large change in optical properties can be obtained before and after irradiation.

Next, there are two types of alloys: solid state alloys and eutectic alloys.

In order to perform alloying by irradiating a light beam onto a laminate of chemical vapor deposition films of a first metal and a second metal that form a solid-state alloy, the interfacial temperature of both metals is substantially lowered. It is necessary to raise the temperature higher than the melting point of

Furthermore, for the combination of two types of metals forming a solid-state alloy, the difference in size of the two types of atoms is 15% or less according to the Huyum-Rosaly rule. ■Have the same crystal structure. ■There is no big difference in electronegativity. ■The valences are the same. ]
must be satisfied.

Therefore, even if a laminate of two metals forming a solid-state alloy is irradiated with a light beam to form an alloy, the optical properties before and after irradiation will change only slightly.

In contrast, the present invention uses a combination of metals that form a eutectic alloy.

A light beam is irradiated onto a stack of chemical vapor deposition films of a first metal and a second metal forming a eutectic alloy, so that the interface temperature for alloying is substantially higher than the melting point of both metals. A low eutectic point is sufficient. Therefore, the intensity of the light beam that is as high as that required to form a solid-state alloy is not required, and by appropriately selecting the thickness of each thin film layer constituting the laminate, the alloy can be formed at a temperature lower than the eutectic point. In some cases, a chemical reaction may proceed. Although the exact reason for this is unknown, it is thought that it is because interdiffusion of atoms constituting each thin film layer occurs at a temperature below the eutectic point.

Furthermore, in a metal laminate forming a eutectic alloy, there is a large difference in the optical properties of the metals forming each layer, so the optical properties of the eutectic alloy also change significantly before and after recording.

That is, a laminate of chemical vapor deposition films of two metals forming a eutectic alloy can be used as an optical recording medium having high sensitivity and high contrast ratio.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1(a) shows the basic structure of an embodiment of an optical recording medium according to the present invention. In this example, an optical recording medium 10 is constructed by laminating a chemical vapor deposition thin film laminate 2 on a support 1. FIG. 1(b) is a partially enlarged view of FIG. 1(a). The chemical vapor deposition thin film stack 2 consists of first layers having eutectic points with each other.
a chemical vapor deposition film 21 of metal, nonmetal or alloy;
Second metal, nonmetal or alloy chemical vapor deposition film 22
It is made by laminating four layers alternately. Here, the first
The chemical vapor deposition film 21 of metal, nonmetal or alloy is a chemical vapor deposition film of Zn with a thickness of 60 mm, and the second metal,
The nonmetal or alloy chemical vapor deposition film 22 is a Ge chemical vapor deposition film with a thickness of 60 nm, and a superlattice structure is formed by stacking these films.

Here, when a part 30 of the chemical vapor deposition thin film stack 2 is irradiated with the light beam 3 as shown in FIG. A superlattice structure vanishing region 2° is formed in the irradiated region 30.Although the detailed structure of the vanishing region 2° at the atomic level is unknown, the alloying reaction does not occur on the surface of the irradiated region 30 without forming large irregularities. A reaction that is considered to occur occurs, and since the optical properties are different for the superlattice structure region of the chemical vapor deposition thin film stack 2, it can be used as an optical information point.
When the energy of the light beam irradiated here is increased, the superlattice structure vanishing region 2'' deforms and becomes a recess or hole, which can be used as an optical impression pit. When using an object, energy heat is stored, so a relatively low light beam can be used.

In this way, forming the optical information pits as recesses or holes by changing or deforming the optical properties of the superlattice structure can be selected as appropriate depending on the desired use of the optical recording medium.

FIG. 2 is an enlarged partial cross-sectional view of an embodiment in which a laminate 2 is formed by sequentially stacking chemical vapor deposition films 21, 22, and 23 of three types of metals, nonmetals, or alloys.

In this way, in the chemical vapor deposition thin film stack 2, it is sufficient that chemical vapor deposition films of at least two types of metals, nonmetals, or alloys are laminated so as to have a eutectic point.

Recording media with the above basic structure can easily be used as hard disks, flexible disks, cards, tapes,
It can be used in the form of a sheet or the like.

In addition, in practical use, a protective layer 4 is provided on the surface as shown in FIG. 3(a).
It is preferable to provide This protective layer 4 may be made of any light-transmitting material. For example, a material used for the support described later may be used. Even with such a protective layer 5, as shown in FIG. 3(b), the light beam 4
Accordingly, the superlattice structure vanishing region 2' can be formed. This protective layer protects the chemical vapor deposition thin film laminate 2, but it essentially has the same function as the support. For example, when a light beam is irradiated from the support side, this protective WLN serves as a support. Becomes a body.

In addition, an adhesive layer may be provided to improve the adhesion between the chemical vapor grown thin film laminate 2 and the support 1, and the laminate 2 and the support may be provided for the purpose of improving the film formability of the laminate 2. One or more intermediate layers may be provided between the body 1 and the body 1.

Furthermore, a reflective layer or an anti-reflection layer is provided on the surface of the chemical vapor deposition thin film laminate 2 or on the surface of a layer laminated on the surface to improve the contrast ratio during reading. body 2 recording schedule section;
In order to track the recorded portion, a tracking pattern layer having an uneven shape, shading, or different light reflectance can be provided.

Materials of Recording Medium Materials used for each component of the optical recording medium according to the present invention are illustrated below.

(Support) The support used in the present invention may be a general inorganic material such as glass, aluminum, silicon, etc. or an organic material plate, film, sheet, etc., and is appropriately selected depending on the shape of the medium. For example, for cards, plastic sheets or films such as vinyl chloride, polycarbonate, acrylic, polymethyl methacrylate, polyester, polystyrene, and epoxy resin are used, and the thickness is 0.1
It is about 2 mm.

(Chemical Vapor Deposition Thin Film) Examples of metals, nonmetals, or alloys forming the chemical vapor deposition film of the present invention include Cu, Zn, Cd, and B.

A' % G 3% I n % CSS 'I
s G e % 3 n ,,P −.

Metals such as A3%, Sb, 3% Se, Te, Mo, W,
Non-metals or alloys thereof can be used.

Generally, when two types of chemical vapor deposition films are alternately laminated to form a chemical vapor deposition thin film laminate 2, the film thicknesses of the first chemical vapor deposition film and the second chemical vapor deposition film are as follows: The film thickness must be such that the composition provides a large change in optical properties when the superlattice structure disappears due to light beam irradiation. Further, the film thickness must be such that eutectic alloying sufficiently progresses and the superlattice structure disappears quickly within the light beam irradiation time. Therefore, the film thickness of both the first chemical vapor deposition film and the second chemical vapor deposition film is preferably about 5 to 1000 layers. More specifically, it is desirable to determine from the eutectic point and the light beam irradiation time.

A combination of the first chemical vapor deposition film and the second chemical vapor deposition film having eutectic points is A I/
Cu (548@), Ge/A I (424'), I
n/A I (637@), S i/A I (577
'), Sn/A 1 (228,3''')
, A I/Te (414'), A I/Zn (38
2'), As/Cu(689'), As/
Ge (736'), In/As (731°), A
s/5 (310”), A s /S i (786
'), A s/S n (579'), Cd/Cu (3
14”), Cd/Ge(319’), Cd/
I n (123°), C4/S e (220”
), Cd/5n(177@), Cd/Zn(2
66@), Cu/Ge(640'), Cu/I
n (153°), Cu/S 1 (802'),
Cu/5n (227"), Cu/Te (340'),
I n/S n (117°), I n/Te (42
7@), In/Z n(143,5'), S/
S e (105”), S/Te (107’),
S e/5n (640°), Sn/Te (465”)
, Sn/Zn (198°), G e /T e
(375'), G e / Z n (39B"
) etc.

Among these combinations, A I / Cu (548
°), Ge/A I (424@), S i/A
I (577m), AI/Te (414'), AI
/Zn(3B2@), Cd/Cu(314”), C
d/Ge (319'), Cu/S 1 (802')
, Cu/Te (340@), Ge/Zn (398″)
The composition distribution at the thin film interface is steep, making it possible to record with high sensitivity and high contrast.

Here, the chemical vapor deposition film of Zn is, for example, dimethyl zinc (
It is created using Zn (CH3)z3 as a raw material, but in this case, the created chemical vapor deposition film contains impurities such as carbon,
Hydrogen may be taken in, and hydrogen may be taken in as an impurity in a chemical vapor deposition film of Ge, for example, when germane (GeHa) is used as a raw material. However, it has not been recognized that these impurities have an adverse effect on optical recording.

The method for manufacturing an optical recording medium according to the present invention will be explained below.

The chemical vapor deposition thin film laminate used in the present invention is manufactured by chemical vapor deposition.

The raw materials used are metal or nonmetal hydrides, halides (fluorides, chlorides, bromides), or fulkylated compounds (alkyl: methyl, ethyl, etc.) that form thin films, and are usually used in a gaseous state. It will be done.

This gaseous raw material is transported to the vicinity of the support, where energy such as heat, discharge, or light is applied to decompose the raw material gas, and metals or nonmetals are attached to the support to grow a thin film. to form a thin film. The thickness of this thin film can be easily formed to any desired thickness by controlling the opening and closing of the raw material gas supply valve.

This operation is performed while changing the raw material gas so that adjacent layers have eutectic points (so that adjacent thin films have eutectic points)
The optical recording medium of the present invention has a superlattice structure of metallic or nonmetallic chemical vapor deposition films having eutectic points with adjacent layers by forming a layered structure of a desired number of thin film layers. can be obtained.

Note that it is also possible to form the chemical vapor deposition thin film laminate on only a portion of the substrate, and in this case, a mask may be provided except for the forming portion.

Further, the alloy thin film can be formed by chemical vapor deposition by mixing and supplying two or more types of raw material gases.

A recording method for an optical recording medium according to the present invention will be explained below.

In order to cause the disappearance of the superlattice structure due to alloying in the chemical vapor grown thin film stack of optical recording media, it is necessary to apply heat to the level of the eutectic point of the thin film, and this condition must be satisfied. Determine the energy and irradiation time of the irradiation light beam. A converged laser beam can be used as the light beam.

The size of the information pits recorded in this way is not particularly limited, and can be any size depending on the amount of information to be recorded or the recording/reproducing device.

There are no particular restrictions on the light beam for detection, and it is sufficient to choose one that has a different reflectance between the alloyed part, which is the recorded part, and the unrecorded part; for example, a low-power laser convergence beam, an LED, etc. can be used. .

Tomaba: The optical recording medium of the present invention having the above-described configuration is suitably used for the following applications.

(1) Financial distribution industry: Cash cards, credit cards, prepaid cards.

(2) Medical and health industry: health records, medical records, medical cards, emergency cards.

(3) Entertainment industry: software media, membership cards, admission tickets, game machine control media, video game media.

(4) Transportation and travel industry: traveler cards, licenses, commuter passes,
passport.

(5) Publishing industry: electronic publishing.

(6) Information processing industry 2 External recording devices and filing of electronic equipment.

(7) Educational industry: teaching material programs, grade management cards, Tsuyoshikan crowd management and bookmark management (8) Automobile industry: maintenance records, operation management.

f91FA: Program recording medium for MC, NC, robot, etc.

(10) Others: Building control, home control, ID cards, shoe king cards, media for vending machines.

(Effects of the Invention) According to the present invention, since the chemical vapor grown thin film stack in which information is recorded is formed with a superlattice structure of chemical vapor grown films having eutectic points, A reaction that can be considered as alloying easily occurs, and there is a large difference in optical properties between this reaction part and other superlattice structure parts, so
High-sensitivity, high-contrast recording becomes possible. Furthermore, if energy larger than the energy required for the above reaction is supplied, the recesses or holes can be formed as information pits, and recording with even higher contrast becomes possible.

■Recording of information does not involve volume changes due to structural changes in the chemical vapor deposition thin film laminate. Therefore, the optical recording medium of the present invention does not require conventional means for sensitizing volume changes or layer structure, and can take various shapes.

■The thin film that forms the laminate is made of a stable material, so it has excellent stability over time and environmental stability. Further, a laminate in which a protective layer is formed is even more excellent.

■Furthermore, unlike thin film creation using sputtering or vapor deposition methods, there is no need to move the base material between two or more evaporation sources or sputter cathodes at high speed during creation, and thin films can be created simply by operating the source gas valve. It is possible to create a multilayer iM laminate extremely easily, and the reproducibility of the created thin film is also good.

(Specific example) The present invention will be explained below based on specific examples.

Material U Coarse 1 Optically polished glass with a thickness of 1.2 mm was used as a support and placed at a predetermined location in the reaction vessel.

Next, dimethylzinc (Zn (CH3) 2 ) was added to H2
Bubble with gas and introduce into the reaction vessel to 0.30To
This source gas was decomposed by electrical discharge at a pressure of rr, and a chemical vapor deposition thin film of Zn with a thickness of 60 μm was deposited on the support.

Next, a source gas of germane [GeH4] was introduced into the reaction vessel, and the source gas was similarly decomposed to deposit a chemical vapor deposition thin film of Ge with a thickness of 60 nm on the Zn.

Perform the above gas valve opening/closing and discharge operations in sequence, and
A laminate of chemical vapor deposition thin films having a thickness of 60 layers with 0 cycles (20 layers) was formed on a support to obtain an optical recording medium of the present invention.

Recording was performed by irradiating the obtained optical recording medium with a 500 ns pulse of semiconductor laser light of 830 nm and 5 mw focused to a diameter of 1 μm.

Next, when this recorded optical recording medium was read, the reflectance of the recorded area was 60%, and the reflectance of the unrecorded area was 40%, indicating that a good change in reflectance was obtained as a recording medium. It was done.

A polycarbonate film with a thickness of 0.6 mm was used as a support and placed in a predetermined place in the reaction vessel.

Next, the raw material gas germane (GeH4) was introduced into the reaction vessel, and the raw material gas was decomposed by discharging at a pressure of 0.30T or r, and a chemical vapor phase of Ge with a thickness of 30T was formed on the support. A grown thin film was deposited.

Next, trimethylaluminum (A I (CHs ) j)
was bubbled with H2 gas and introduced into the reaction vessel.The raw material gas was decomposed in the same way, and a 7-thick layer was formed on Qe.
A chemical vapor deposition thin film of 0 AI was deposited.

Perform the above gas valve opening/closing and discharge operations in sequence, and
A laminate of chemical vapor deposition thin films having a thickness of 30 layers of Ge and 170 layers of A was formed on a support in a periodic manner (10 layers) to obtain an optical recording medium of the present invention.

Recording was performed on the obtained optical recording medium by irradiating it with a 500 ns pulse of semiconductor laser light of 830 nm and 2 mw focused to a diameter of 1 μm.

Next, when this recorded optical recording medium was read, the reflectance of the recorded part was 80%, and the reflectance of the unrecorded part was 40%, indicating that a good change in reflectance was obtained as a recording medium. It was done.

A polymethyl methacrylate film having a thickness of 1 and Q mm was used as a support and was placed at a predetermined location in the reaction vessel.

Next, hydrogenated tellurium (TeHz) as a raw material gas is introduced into the reaction vessel, and irradiated with an ArF excimer laser (19 mm) and an infrared lamp to decompose the raw material gas and form a 3-thick layer on the support.
A chemical vapor deposition thin film of 0 Te was deposited.

Next, trimethylaluminum (A l (CHy)1)
was bubbled with H2 gas and introduced into the reaction vessel, and the raw material gas was decomposed in the same manner and deposited on Te to a thickness of 7.
A chemical vapor deposition thin film of 0 AI was deposited.

Perform the above gas valve opening/closing and irradiation operations in sequence, and
An optical recording medium of the present invention was obtained by forming a laminate of chemical vapor deposition films having a period (107i) of 30 layers of Ge and 70 layers of Al on a support.

The resulting optical recording medium was irradiated with a 500 ns pulse of semiconductor laser light of 830 nm and 7 mw focused to a diameter of 1 μm to form a hole in the laminate for recording.

Next, when this recorded optical recording medium was read, the reflectance of the recorded area was 3%, and the reflectance of the unrecorded area was 40%, indicating that a good change in reflectance was obtained as a recording medium. It was done.

A polycarbonate film with a thickness of 0.6 mm, which was masked except for an area of 20 mm x 75 m+o, was used as a support and placed at a predetermined location in the reaction vessel.

Next, using germane (GeHa) and trimethylaluminum (A 1 (CHz ) *) as raw material gases, a further thickness of 30 Ge was applied to the 2011III+×75 ml area of the support in 5 cycles (101i) in the same manner as in Example 2. Al7
An optical recording medium of the present invention was obtained by forming a laminate of thin films by chemical vapor deposition.

A pressure-sensitive adhesive was applied to the facing surface of the resulting laminate of optical recording media, and a polyvinyl chloride film having a thickness of 0.12 mm was laminated thereon.

Next, this laminate was punched out to the size of a card to obtain an optical card. 83Q n
Recording was performed by condensing semiconductor laser light of 2 mw and 2 mw into a diameter of 1 μm and irradiating it with a 500 ns pulse.

Next, when I read this recorded light card,
The reflectance of the recorded area is 80%, and the reflectance of the unrecorded area is 4.
0%, and a good change in reflectance was obtained as a recording medium.

[Brief explanation of the drawing]

Fig. 1 fa+ is a sectional view showing the structure of an embodiment of the optical recording medium according to the present invention, Fig. 1 fbl is a partially enlarged sectional view of Fig. FIG. 2 is a partially enlarged sectional view showing the structure of another embodiment of the optical recording medium according to the present invention; FIG. 3 is a diagram showing a recording method on an optical recording medium;
Figure (a) is a cross-sectional view showing the structure of another embodiment of the optical recording medium according to the present invention. ...Support 2...Chemical vapor deposition thin film laminate 2゛...Superlattice structure disappearing portion 3...Light beam 10...Optical recording medium 21, 22, 23,...Chemical vapor Phase growth thin film patent applicant Dai Nippon Printing Co., Ltd. Representative Patent attorney Atsushi Konishi Figure 1 (a) Figure 1 (C)

Claims (2)

[Claims] (1) An optical device characterized in that a plurality of chemical vapor deposition thin films made of metals, nonmetals, or alloys are stacked on a support in a superlattice structure so that they have eutectic points with adjacent layers. recoding media. (2) A recording layer with a superlattice structure is formed by laminating a plurality of thin films made of metals, nonmetals, or alloys on a support by chemical vapor deposition so that they have eutectic points with each other. A method for manufacturing an optical recording medium.