JPH0737180B2 - Optical information recording member - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to an optical information recording member for recording and reproducing optical information utilizing light, heat and the like, and its object is to achieve high speed. Another object of the present invention is to provide an optical information recording member capable of high-density recording and reproduction.

A recording medium used for recording and reproducing high-density information using a laser beam is TeOx, which is a mixture of Te and TeO ₂ on a substrate.
A device provided with a thin film containing ₁ (0 <x ₁ <2) as a main component (Japanese Patent Laid-Open Nos. 50-46317, 50-46318, and Sho-
50-46319, U.S. Pat. No. 3,971,874), and PbOx ₅ (0 <x ₅ <1) and SbOx ₆ (0
_{<X 6 <1.5), VOx} 7 (0 <x 7 <2.5) or the like is used. In such a recording medium, it is possible to obtain a large change in transmittance upon irradiation with a reproduction light beam.

However, there is a limit to the output of the laser light source that can be used to reduce the size and simplification of the recording / playback device.
Conventional TeOx is used to record and reproduce using a small He-Ne laser oscillator, semiconductor laser oscillator, etc.
A recording medium provided with a thin film containing (0 <x <2) as a main component has insufficient sensitivity. Further, when reproducing information by changing the amount of reflected light, a sufficient amount of change cannot be obtained. To compensate for this drawback, an additive material having a low melting point is applied to TeOx (0 <x <2) to reduce the threshold temperature of state change, for example, TIOx (0 <x <1.5) (TI ₂ O melting point 300
C.) is added, and on the other hand, there is a method of increasing the refractive index of the medium in order to increase the change in the optical characteristics accompanying the change in the state. Therefore, attempts have been made to use an additive material having a high ionic polarizability and a high density. For example
BiOx ₂ , InOx ₂ (0 <x ₂ <1.5) and the like.

According to these methods, the recording medium containing TeOx as a main component enables recording by a semiconductor laser and reproduction by changing the amount of reflected light, but with the progress of the information society, a high speed of information transmission is required. Therefore, it is necessary to further increase the recording speed and the reproduction speed and to improve the recording sensitivity accordingly. It is an object of the present invention to answer this request.

[Structure of the Invention] The optical information recording member of the present invention comprises tellurium, oxygen, and an element selected from nickel, platinum, cobalt and chromium, and the content of the selected element is 3 to 38 atm%. The optical recording thin film is characterized in that the oxygen content is 20 to 60 atm%.

The technical contents will be specifically described below. A TeOx thin film, which is a mixture of TeO ₂ and Te, changes its optical constant when irradiated with high-density light such as laser light, and becomes black in appearance. Information is optically recorded and reproduced by utilizing this change.This change is the state change of Te particles in the film, that is, the growth of crystal grains, through a process of light irradiation-absorption-temperature rise. It is considered that it is based on the optical change due to Therefore, in order to increase the recording speed, it is considered that how quickly this state change is completed is a major factor. By the way, in a conventional TeOx-based thin film, if Te particles change state during recording,
Since there is an O ₂ barrier, it may take some time to relax the structure to achieve a stable crystalline state. Such a recording member does not cause any problem when recording an image or the like as information, but is not preferable because it is limited in device design when used as a computer disk that requires high-speed response.

The present invention is based on TeOx, which is a mixture of Te and TeO ₂ , with Ni, Pt, Co,
By using a thin film having a basic composition containing an element selected from Cr as a recording layer and controlling the ratio of the number of atoms of Te and O and the selected additional element in the film,
It is possible to obtain an optical recording medium capable of recording and reproducing at a much higher speed than that of a TeOx recording thin film.

There is a conventional example in which a third substance is added to Te or a mixture of Te and TeO ₂ to improve the characteristics of the optical recording medium. However, they are elements with a relatively strong covalent bond such as Ge, Sn, Pb, Si, Sb, and Se, and were limited to materials that easily form a glass state with Te or a mixture of Te and TeO ₂ . . On the other hand, in the present invention, Ni, Pt, Co and Cr are particularly selected from among the elements having a strong metal binding property as the substance to be added. These elements promote the Te state change during recording in the TeOx thin film and are considered to act like crystal nuclei. It is estimated that it will be obtained. Further, completion of the Te state change at high speed during recording means that the state change is completed while the viscosity of the film is small, for example, when it is considered that the laser light irradiation portion is softened or melted. Therefore, it is assumed that Te crystal particles with more advanced crystallinity are generated. As a result, it is considered that a larger reflectance change of the reproduction light is obtained and a high CN ratio is obtained. Further, TeOx has a large light absorption efficiency by adding the selected additive element of the present invention. Then, writing can be performed with a laser beam having a lower power, and the sensitivity becomes high. Furthermore, since these additive elements do not undergo oxidation due to their properties, they do not impair the excellent moisture resistance of conventional TeOx films.

The present invention comprises an element selected from Te, O and Ni, Pt, Co, Cr as an essential component, but Ge, Sn, Al, Cu in order to improve the optical characteristics and heat resistance of the film. , Ag, Au, S
One or more elements selected from e, Bi, In, Pb, Si, Sb, As and V may be added. Since the optical information recording member of the present invention can be applied to a recording material capable of rewriting information in addition to the function as a recording material for only recording and reproduction,
In this case, it is necessary to add at least one of the above-mentioned elements to improve the erasing property.

The addition amount of the additional elements (Ni, Pt, Co, Cr) in the present invention is appropriately 3 to 38 atm% with respect to the total of the constituent elements. It is considered that these additive elements exist in an amorphous state by partially bonding with Te of TeOx (NiTe, NiTe ₂ , PtTe, PtTe ₂ , CoTe, CrTe). When this is heated by a laser or the like, it changes from an amorphous state to a crystalline state and causes an optical change. The compound of Ni, Pt, Co, Cr and Te does not necessarily have to be in the stoichiometric composition, for example, it may be present in the alloy composition of NiTe-Te, and the role of NiTe becomes a crystal nucleus and the crystallization rate of the whole. It is thought to promote. Therefore, it is sufficient if the added amount of the additional element is smaller than that of Te. However, if the added amount is 3 atm% or less, the number of crystal nuclei in the film decreases, and high-speed crystallization cannot be expected. Further, when the added amount is increased, the light absorption efficiency is improved and the recording sensitivity is improved, but when it exceeds 38 atm%, the relative amount of Te in the film is decreased,
The change in the amount of reflected light before and after recording is reduced. Therefore, Ni, P
It is necessary to add t, Co, and Cr in the range of 3 to 38 atm%.

Next, the oxygen content will be described. In the present invention, most of oxygen is combined with Te to form TeO ₂ . The amount of TeO ₂ present is important for controlling the moisture resistance of the film, and the higher the amount of TeO ₂ , the better the moisture resistance. Therefore, in the film, the higher the oxygen content is, the more desirable it is. However, if the oxygen content is too high, the contents of Te and the additional element become relatively small, so that the light absorption efficiency of the film is lowered and the sensitivity is lowered. And the amount of change in reflectance before and after recording becomes small, so that a high CN ratio cannot be obtained. The oxygen content in the present invention is 20 to 60 at with respect to the sum of Te, O and additional elements.
It is m%, but the reason is that moisture resistance decreases at 20 atm% or less,
This is because the recording sensitivity decreases when the content is 60 atm% or more.

The optical information recording member of the present invention will be described with reference to FIG.
In the figure, 1 is a substrate, which is a metal (aluminum, copper, etc.), glass (quartz, pyrex, soda glass, etc.), or resin (ABS resin, polystyrene, acrylic, polycarbonate, vinyl chloride, etc.), and as a transparent film, acetate. , Teflon, polyester, etc.) are used. Among them, polycarbonate, acrylic plate and the like have excellent transparency and are effective in optically reproducing a recorded signal. A recording thin film 2 is formed on the substrate 1 by vapor deposition, sputtering or the like. The vapor deposition includes a resistance heating method and an electron beam method, but both methods can be used. However, the electron beam method is superior in view of controllability of vapor deposition and mass productivity.

Hereinafter, a method for producing a thin film composed of an additive element selected from Te, O and Ni, Pt, Co, Cr by using the electron beam method will be described. Using a vapor deposition machine capable of three-source evaporation to form a mixture of Te, TeO ₂ and additional elements on a substrate, TeO ₂ and Te and additional elements are deposited from respective sources. But 2
Source sources or single source sources are also possible. When using a two-source source, the additive element is vapor-deposited from one side and the other from the other side.
TeO ₂ and a metal powder having a function of partially reducing TeO ₂ , for example, Al, Cu, Fe, and the like are mixed and heat-treated at a predetermined temperature, and TeO ₂ and Te are simultaneously vapor-deposited. A mixture of TeO ₂ , Te and additional elements is formed on the substrate. Again 1
When a source is used, the additive element is mixed in the source on the side where TeO ₂ and Te are vapor-deposited in the case of using the dual source, and TeO ₂ , Te and the additive element are vapor-deposited from one source.

[Example 1 (when the additive element is Ni)] Using an electron beam evaporator capable of three-source evaporation, TeO ₂ , Te, and Ni were rotated from each source at 150 rpm, the thickness was 1.1 mm, and the diameter was Is 200
An optical disk was prototyped by vapor deposition on a mm acrylic resin substrate. Deposition was performed at a vacuum degree of 1 × 10 ^-5 Torr or less and a thin film thickness of 1200Å. The deposition rate from each source was variously changed in order to adjust the ratio of the number of Te, O, and Ni atoms in the recording thin film.

The results of elemental analysis of various optical disks prepared by the above method by Auger electron spectroscopy (hereinafter abbreviated as AES),
A signal with a single frequency of 5 MHz written with a laser power that maximizes the CN ratio when recording is completed, at a position 75 mm from the center of the optical disk that rotates at 0 rpm, 33 msec after recording ( Table 1 shows the CN ratio after a lapse of one rotation of the disk), the CN ratio after a lapse of 2 minutes (recording was completed for all optical disks), and the results of the moisture resistance test. is there.

FIG. 2 shows an outline of an apparatus used for the recording / reproducing test. The light having a wavelength of 830 nm emitted from the semiconductor laser 14 becomes a collimated parallel 3 by the first lens 15, becomes a round shape by the second lens 4, and becomes parallel light again by the third lens 5, and is made by the mirror 6. After the optical axis is converted, the wavelength limit is about 0.8 μm on the optical disk 8 by the fourth lens 7 via the half mirror 11.
It is focused on the spot 9 having the size of. This circle spot 9
The recording film on the optical disk 8 irradiated by the light is recorded by the blackening transformation due to the change in the state of Te. Here, the semiconductor laser can be modulated to record an information signal on the optical disk. The signal was detected by receiving the reflected light 10 from the optical disk surface 8 by the half mirror 11 and detecting it by the light sensitive diode 13 through the lens 12.

In Table 1, if the CN ratio is larger 2 mm after laser irradiation than 33 msec, it is considered that the growth of Te crystal grains in the thin film is still progressing after 32 msec, and the recording is not yet completed. It shows that there is no, 33msec after laser light irradiation and 2m
If the CN ratio is the same after m, it means that the recording is completed after 33 msec.

Moisture resistance test is performed on a glass substrate (18 x 18
X 0.2 mm), a recording thin film is vapor-deposited as a sample for a moisture resistance test, and the sample is left to stand at 50 ° C and 90% RH.
Regarding the moisture resistance evaluation in Table 1, the condition on the 10th day was ○ when no change was observed under the microscope, Δ was when a slight change was observed, and black pattern due to crystallization was observed. The case where the transmittance was increased due to the oxidation of Te in the film or the case where Te in the film was oxidized was defined as x.

As is clear from Table 1, the composition of the Te-O-Ni-based thin film (CN ratio after completion of recording is 50 dB or more, recording is completed after irradiation of laser light for 33 msec, and moisture resistance is good ( In the overall evaluation, △ or more), Pd is 3 to 38 atm% and oxygen is 2
It is 0 to 60 atm%. It can be seen that a more preferable composition (○ in the comprehensive evaluation) is 8 to 35 atm for Ni and 30 to 55 atm% for O.

Instead of Ni in this example, Ag and Cu were used as reference examples.
An optical disk having a Te-O-Ag-based thin film and a Te-O-Cu-based thin film was prepared by using, and the same test as in this example was conducted. The results are shown in Table 2. As is clear from the table, Ag
Or, when Cu was added, the high-speed recording completion of the signal as when Ni was added was not obtained.

[Example 2 (when the additive element is Pt)] From one source using an electron beam vapor deposition machine capable of vapor deposition with a two-source source
An optical disk was prepared by evaporating Pt and Te and TeO ₂ from the other source. Here, a method of simultaneously depositing Te and TeO ₂ from one source will be described. First, 85% by weight of TeO ₂ and 15% by weight of Al were mixed as a starting material with a small amount of alcohol, and 25 g of the powder was placed on a quartz boat and heated by an electric furnace.
A part of TeO ₂ was reduced by baking at 00 ° C. in a N ₂ gas atmosphere for 2 hours, and the baked product was crushed and pressed to form a molding material (pellet), which was used as a raw material. Thereafter, the vapor deposition rate Pt is 1Å / S, on the acrylic resin substrate in the same manner as in Example 1.
(Te + TeO ₂ ) was set to 20Å / S and a recording thin film of 1200Å was formed.

The result of elemental analysis of the above recording thin film by AES is Te = 60a
tm%, O = 32 atm%, Pt = 8 atm%. Further, the same recording / reproduction test and moisture resistance test as in Example 1 were carried out. As a result, the CN ratio after laser light irradiation was 33 msec and after 2 mm, both were 58 d.
At B, it was confirmed that the recording was completed at high speed,
The moisture resistance was evaluated as good.

[Example 3 (when the additive element is Co)] Using the same method as in Example 2, Te and TeO ₂ were used as one source, and the other was Co.
The vapor deposition rate of Co was 2Å / S, and an optical disk having a recording thin film of 1200Å was prepared. Elemental analysis of the above recording thin film by AES shows that Te = 57 atm%, O = 28 atm%, Co = 15 atm
It was m%. Further, when a recording / reproducing test and a moisture resistance test were carried out in the same manner as in Example 1, it was confirmed that the CN ratio after laser irradiation 33 msec and after 2 mm was 53 dB, and the recording was completed at high speed. Moisture resistance evaluation was good.

[Example 4 (when the additive element is Cr)] Using the same method as in Example 2, Te and TeO ₂ were used as one source and the other was Cr.
An optical disk having a recording thin film with a vapor deposition rate of Cr of 2Å / S and 1200Å was prepared. Elemental analysis of the above recording thin film by AES shows that Te = 60 atm%, O = 28 atm%, Cr = 12 atm
It was in%. Further, the same recording / reproduction test and moisture resistance test as in Example 1 were carried out.
The CN ratio after 2 mm was 54 dB, and it was confirmed that the recording was completed at high speed, and the moisture resistance evaluation was good.

[Example 5 (when the additive elements are Ni and Pt)] Ni and Pt are independently vapor-deposited from one source and Te and TeO ₂ are vapor-deposited from one source by using an electron beam vapor deposition machine capable of vapor deposition from a four-source source. A light disk was prepared. Te; 15Å / S, TeO ₂ ; 6Å /
S, Ni; 1Å / S, Pt; 1Å / S Elemental analysis of the above recording thin film by AES shows Te = 40 atm%, O = 42 atm%, Ni = 10 atm
%, Pt = 8 atm%. Further, when a recording / reproducing test and a moisture resistance test were performed in the same manner as in Example 1, it was confirmed that recording was completed at high speed with a CN ratio of 60 dB both after 33 msec of laser light irradiation and 2 mm after laser light irradiation. Moisture resistance evaluation was good.

[Example 6 (when the additive elements are Ni and Co)] Pt of Example 5
Instead of, Co was vapor-deposited at 1Å / S to make a disk. The result of elemental analysis of the above recording thin film by AES is Te = 40 atm
%, O = 42 atm%, Ni = 10 atm%, Co = 8 atm%.
Further, the same recording / reproduction test and moisture resistance test as in Example 1 were carried out. As a result, the CN after 33 msec and 2 mm after the laser irradiation was measured.
It was confirmed that the recording was completed at a high speed with both ratios of 57 dB, and the moisture resistance evaluation was ○.

To obtain a TeO-Ni thin film only by depositing from a source of single [(case of 1 source source) Example 7, as a starting _{material, TeO 2 = 60wt%, Al} = 10wt%, Ni = 30wt% Was mixed with a small amount of alcohol, and 25 g of the powder was mixed with an electric furnace.
A portion of TeO _{2 was} calcined at 00 ℃ in N ₂ gas for 2 hours.
It was reduced with Al, and the fired product was crushed and pressed to form pellets, which were used as raw materials. Example 1 using this raw material
In the same manner as above, vapor deposition was performed on an acrylic resin substrate at a vapor deposition rate of 20Å / S to fabricate an optical disk having a 1200Å recording thin film. The result of elemental analysis of the above recording thin film by AES is T
e = 57 atm%, O = 36 atm%, Ni = 7 atm%. Further, the same recording / reproduction test and moisture resistance test as in Example 1 were carried out, and it was confirmed that the CN ratio was 56 dB both after 33 msec of laser light irradiation and after 2 mm of laser light irradiation, and recording was completed at high speed. The moisture resistance was evaluated as good.

[Advantages of the Invention] As described above, the optical information recording member of the present invention comprises Te, O, and an additive element selected from Ni, Pt, Co, and Cr. 3-38at
m% (the most preferred content is 8 to 35 atm%) oxygen content is 20 to 60 atm% (the most preferred content is 30 to 55 a
tm%) significantly improves the recording speed and CN ratio of the conventional optical information recording member made of TeO _X thin film, and provides an excellent effect of providing an optical information recording member with excellent moisture resistance. Have.

[Brief description of drawings]

FIG. 1: Partial sectional view of the optical information recording member of the present invention. FIG. 2: Recording of information by the optical information recording member of the present invention.
Schematic diagram of playback device 1 ... Substrate, 2 ... Recording thin film

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Mutsuo Takenaga 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-61-68296 (JP, A) JP-A-61-943 (JP, A)

Claims (3)

[Claims] 1. Tellurium, oxygen, and an element selected from nickel, platinum, cobalt, and chromium, and the content of the selected element is 3 to 38 atm%, and the content of oxygen is The optical information recording member is provided with an optical recording thin film having a content of 20 to 60 atm%. 2. The content of the element selected from nickel, platinum, cobalt and chromium is 8 to 35 atm%.
The optical information recording member according to claim (1), wherein the oxygen content is 30 to 55 atm%. 3. The optical information recording member according to claim 1, wherein the oxygen is contained as TeO ₂ .