JPH0676360A - Aluminum alloy reflecting film for optical disk and target material for the same - Google Patents

Abstract

PURPOSE:To ensure proper high corrosion resistance by using an Al alloy. contg. 0.3-2.0wt.% Si+Fe, <=0.1wt.% each of Cu and/or Ti as significant elements or impurities and <=0.002wt.% Bi. CONSTITUTION:Each of the objective Al alloy reflecting film for an optical disk and the objective target material for the Al alloy reflecting film consists of 0.3-2.0wt.% Si+Fe, <=0.1wt.% each of Cu and/or Ti as significant elements or impurities, <=0.002wt.% B and the balance Al with inevitable impurities. When a castable Al alloy having the above-mentioned compsn. is used as the target material, a high reflecting film can properly be produced by sputtering.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy reflective film for an optical disk and a target material thereof, and more particularly to an optical disk having a highly corrosion resistant reflective film and having high reliability.

[0002]

2. Description of the Related Art An optical disc has a high information recording density and has a characteristic that existing information can be reproduced in a non-contact manner. It is widely used in fields such as mass filing systems for office automation.

In the above-mentioned optical disk, however, a pit string corresponding to information is formed on one surface of a highly transparent substrate made of synthetic resin, and a reflective film is coated on the pit string, and if necessary, further thereon. The protective film is formed, and the recording is read by irradiating a laser beam from the opposite side surface. Therefore, the reflective film is required to have excellent corrosion resistance, and it is most common to use a pure Al vapor-deposited or sputtered film.

As described above, pure Al has been used as a material for a reflective film in an optical disk because of its excellent reflectance, but this superiority depends on the initial reflectance (reflectance immediately after film formation). However, in recent years, the decrease in reflectance that has progressed in the atmosphere has become a problem. That is, pure Al has low corrosion resistance as a metal itself, and corrosion is apt to progress when left in the air for a long period of time, which causes a decrease in reflectance and pitting corrosion and increases a signal reading error during information reproduction. .

From the above, various studies have been carried out particularly for the purpose of ensuring long-term stability of information reproduction regardless of the storage environment, and Ag, Pd, Pt, for example, as a highly corrosion-resistant alloy replacing pure Al. Binary alloys in which Al, Ta, Hf, etc. have been proposed. In addition, JP-A-63-224050
Proposed to use an Al-Ti alloy as a reflective film.

[0006]

Among the above-mentioned binary alloys with high corrosion resistance, those using Ag, Pd, and Pt are expensive, and those containing Ta and Nb cause a decrease in initial reflectance. I have a serious problem. Moreover, in these alloy systems, it is difficult to form a stable film by the vapor deposition method because of the large difference in melting points among the constituent elements. The alloy system has a disadvantage that it becomes difficult at the stage of producing a target.

According to Japanese Patent Laid-Open No. SHO 63-224050, Ti does not have the drawback of lowering the initial reflectance unlike Ta or Nb, but it still has a problem in corrosion resistance during long-term storage. As for information and long-term stability regarding reproduction, it is difficult to obtain sufficient trust.

[0008]

Means for Solving the Problems The present invention has been studied to solve the technical problems in the conventional ones described above, and has a great effect on cost reduction when a large amount of reflective films for optical disks are formed. In addition, the initial reflectance is sufficiently high, and excellent corrosion resistance is exhibited for a long period of time, and a reflective film capable of suppressing a decrease in reflectance is obtained, which is excellent in reliability of information reproduction for a long period of time. It has succeeded in providing an optical disk and is as follows.

(1) Si + Fe is 0.3 to 2.0 wt%,
Cu less than 0.1 wt% as significant or impurities, and Ti
Is 0.1 wt% or less, or Ti is 0.1 wt% or less and B is 0.0
An aluminum alloy reflective film for an optical disk, which contains not more than 02 wt% and the balance is Al and inevitable impurities other than the above impurities.

(2) Si is 0.1-1.0 wt% and Fe is 0.2-
1.0 wt% and 0.1 wt% of Cu as a significant or impurity
% Or less, Ti is 0.1 wt% or less, or Ti is 0.1 wt%
An aluminum alloy reflective film for an optical disk, characterized in that B and 0.002 wt% or less are contained and the balance is Al and inevitable impurities other than the above impurities.

(3) A target material for an aluminum alloy reflection film for an optical disk to be sputtered, which is made of an aluminum alloy having the composition described in the above item (1) or (2).

[0012]

[Function] Si + Fe is 0.3 to 2.0 wt%, Cu as significant or impurities is 0.1 wt% or less, Ti is 0.1 wt% or less and B is 0.002 wt% or less, and the balance is High corrosion resistance can be appropriately obtained by including Al and unavoidable impurities. As other impurities such as Cr, 0.03
% Or less. If the Cu content exceeds 0.1 wt%, the corrosion resistance is reduced, which is not preferable.

Ti or Ti and B are added for refining crystal grains during molten metal casting, preventing casting cracks, and imparting corrosion resistance. However, Ti is 0.1
wt% or Ti exceeds 0.1 wt% and B is 0.0
If it exceeds 02 wt%, a coarse compound of Al—Ti or Ti—B crystallizes and hinders plastic workability, which is not preferable.

Further, it is not necessary to use high-purity Al as a base,
It is possible to obtain it in a large quantity and stably, so that the cost can be reduced in the thin film manufacturing process for manufacturing an optical disk, and a dry process method or the like can be used as a method for forming a reflective film.

Si is 0.1 to 1.0 wt% and Fe is 0.2 to 1.0 wt%.
%, It is possible to obtain a reflective film for an optical disc having a higher reflectance. When Si is less than 0.1 wt% or more than 1.0 wt% or Fe is less than 0.2 wt% or more than 1.0 wt%, the reflectance is slightly lowered.

By using the castable Al alloy having the above composition as the target material, the highly reflective film can be appropriately manufactured by the sputtering method.

The technical relationship of the present invention as described above will be described in more detail. First, the inventors of the present invention must satisfy the following two conditions: the initial reflectance is not lowered and the long-term corrosion resistance is stably exhibited. In particular, various studies were conducted to develop an Al-based alloy that can sufficiently satisfy these conditions in the form of a reflective thin film applied to an optical disc.

That is, various alloys in which the contents of Si and Fe have been variously changed (the contents of Cu and Ti at this time are Cu 0.001 to 0.03 wt% and Ti: 0.03). 00
1 to 0.02 wt%) and prepare DC using these alloys
80 on a glass substrate by magnetron sputtering
A thin film of 0 Å was prepared, and a pressure cooker test (PCT; 121 ° C,
The results of measuring the reflectance before and after the PCT are as summarized in Table 1 below.

[0019]

[Table 1]

As a criterion for high corrosion resistance based on the reflectance measurement value, if the target value before PCT is 92% or more and the target value after PCT is 75% or more is 75% or more, the Fe + Si content from Table 1 is 0.3% or more. Required, but P exceeds 2.5%
In some cases, it does not reach 75% after 10 hours of CT.

The value before PCT is 95% or more, PCT1
If the target value is 80% or more after 0 hours, from Table 1 above
The content of Si and Fe affects the reflectance before and after PCT, that is, the initial value and the value after 10 hours are below the target in the region where the amount of Si and Fe is small, but this content increases. As you do, the target value will be cleared. However, it is clear that when this amount is further increased, the initial value is high but the value after 10 hours tends to decrease.

In other words, from these results, the range of the combination of Si and Fe having excellent corrosion resistance was confirmed, and the present invention could be established. The continuous casting method was used as the method for producing the target material. 400-630 the cast body obtained by
A homogenizing treatment is performed at a temperature of about ° C for about 10 to 48 hours, followed by forging, rolling or extrusion molding, and cutting into a predetermined size. As a method for forming the reflective film, a dry process method, which is a conventionally used metal thin film forming method, can be used.

[0023]

EXAMPLES To explain specific examples of the present invention, the inventors of the present invention used Al-based alloy targets having various compositions and used 800 μm of each alloy thin film on a glass substrate by DC magnetron sputtering method. Was formed. When this sample was subjected to the above-mentioned PCT and the reflectance with time was examined by a spectrophotometer, the results shown in FIG. 1 were obtained.

That is, as shown in FIG. 1, pure Al, Al-2% Cr alloy and Al-1% Si-0.5% Cu shown as comparative materials were used.
The alloy had a low initial reflectance, and the reflectance was significantly lowered as the PCT time passed. On the other hand, in the case of the alloy of the present invention, it is clear that the initial reflectance is higher than those of these, and that the reflectance after 10 hours of PCT continues to be in the 80% range, and it is possible to obtain excellent characteristics. I understand.

Using the same target as above,
1000Å on TAC (triacetyl cellulose) film
The TEM (transmission electron microscope) observation of the thin film sputtered at the thickness of 4 was conducted to examine the crystal grain size of each alloy film, and the results shown in Table 2 below were obtained.

[0026]

[Table 2]

That is, as shown in Table 2, the alloy of the present invention has smaller crystal grains than the other comparative materials.
This result closely resembles the relationship with the reflectance demonstrated in Example 1, and it is presumed that the fineness of the crystal grain size gives the high reflectance and thus the high corrosion resistance.

[0028]

As described above, according to the present invention, it is possible to obtain excellent corrosion resistance, obtain a sufficiently low cost for thin film production at the time of optical disc production, and provide a stable supply in large quantities. It is an invention that has both of the above and has a large effect industrially.

[Brief description of drawings]

FIG. 1 is a table summarizing the reflectance change states of an alloy of the present invention and other comparative materials before and after a pressure cooker test.

Continuation of the front page (72) Inventor Kayoko Hiei 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Nippon Giken Co., Ltd.

Claims (3)

[Claims] 1. Si + Fe is 0.3 to 2.0 wt%, Cu as significant or impurities is 0.1 wt% or less, and Ti is 0.1.
wt% or less, or Ti is 0.1 wt% or less and B is 0.002 wt.
% Or less, and the balance being Al and unavoidable impurities other than the above impurities, an aluminum alloy reflection film for an optical disk. 2. Si 0.1-1.0 wt% and Fe 0.2-1.0 wt%
%, Cu as a significant or impurity is 0.1 wt% or less, and Ti is 0.1 wt% or less, or Ti is 0.1 wt% or less and B is 0.002 wt% or less, and the balance is Al and An aluminum alloy reflection film for an optical disk, which is composed of unavoidable impurities other than the above impurities. 3. A target material for an aluminum alloy reflective film for an optical disk to be subjected to a sputtering process, which is made of an aluminum alloy having the composition according to claim 1 or 2.