JPH06248428A - Aluminum oxide thin film - Google Patents

Abstract

PURPOSE:To improve the durability of an aluminum oxide thin film deposited on a base body with which the elevation of the base body heating temp. to a high temp. is not possible at the time of film formation. CONSTITUTION:The aluminum oxide thin film 2 contg. 3 to 10wt.% tantalum oxide is formed on the plastic base body 1 with which the elevation of the base body heating temp. to a high temp. is not possible. By such a construction, the aluminum oxide thin film 2 having the refractive index and durability equiv. to those of a simple substance aluminum oxide thin film deposited by elevating the base body heating temp. to a high temp. is formed on the plastic base body 1 with which the elevation of the base body heating temp. to a high temp. is not possible without requiring an intricate and costly vacuum vapor deposition device. The film is usable as a protective film of the base body or for an antireflection film as an intermediate refractive index material.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to an improved aluminum oxide thin film used as an optical film or a protective film.

[0002]

2. Description of the Related Art Generally, aluminum oxide (Al
_{The 2} O ₃ ) thin film is widely used as an intermediate refractive index material for an antireflection film and a protective film for various substrates.

Conventionally, for example, an Al ₂ O ₃ thin film is formed on a plastic substrate by vacuum deposition, and the substrate heating temperature is 80 ° C.
The following drawbacks are exhibited when it is deposited on. That is, it is not possible to increase the heating temperature for a plastic substrate, a single Al ₂ O ₃ thin film is deposited becomes a coarse film, single Al ₂ deposited at substrate heating temperature 300 ° C. on glass substrates The durability is remarkably inferior to that of the O ₃ thin film. A single Al ₂ O ₃ thin film deposited on a plastic substrate at a substrate heating temperature of 80 ° C. has a refractive index of about 1.5, and a simple substance A deposited on a glass substrate at a substrate heating temperature of 300 ° C.
The refractive index of the l ₂ O ₃ thin film is lower than 1.63. And so on.

For this reason, A has been conventionally used on a plastic substrate.
In the case of depositing the l ₂ O ₃ thin film, the above drawbacks have been overcome by improving the deposition method such as the ion plating method and the ion assist method.

[0005]

However, there have been the following problems in improving the above-mentioned deposition method. That is, the device is expensive. The operation method is complicated. It is difficult to set the deposition conditions. And so on.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an aluminum oxide thin film which is deposited with high durability on a substrate which cannot be heated at a high temperature during coating. .

[0007]

In order to achieve the above object, the present invention provides that a thin film made of aluminum oxide containing 3 to 10% by weight of tantalum oxide is formed on a substrate in which the substrate heating temperature cannot be raised. Characterize.

[0008]

Since the present invention is constructed as described above, the oxidation having the same refractive index and durability as the simple aluminum oxide thin film deposited by raising the substrate heating temperature on the substrate on which the substrate heating temperature cannot be raised. An aluminum thin film is formed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing an example in which a protective film is applied to a plastic substrate. In FIG. 1, reference numeral 1 denotes a substrate whose heating temperature cannot be raised during coating, for example, a plastic substrate made of polycarbonate. tantalum oxide _{(Ta 2 O 5) Al 2} O 3 thin film 2 which is formed of Al ₂ O ₃ containing a is deposited with a predetermined thickness as a protective film for.

[0011] Experiment with mixing weight ratio of Ta ₂ O ₅ and Al ₂ O ₃ to form Al ₂ O ₃ thin film 2, the relationship between the refractive index of the Al ₂ O ₃ thin film 2 corresponding to the weight ratio, The results shown in FIG. 2 were obtained. The Al ₂ O ₃ thin film 2 is formed by the vacuum deposition method. (1) Base plastic (polycarbonate) (2) Vacuum degree 6.65 × 10 ^{−3 to} 1.06 × 1
0 ⁻² Pa (5 × 10 ⁻⁵ to 8 × 10 ⁻⁵ Torr) (3) Substrate heating temperature 80 ° C. (4) Evaporation source Electron beam (5) Evaporating agent Ta ₂ O ₅ and Al ₂ O ₃ mixture The film was formed under vapor deposition conditions.

As a result of the above experiment, the addition amount of Ta ₂ O ₅ was A
In the range of ₃ to 10% by weight with respect to l ₂ O ₃ , A
The refractive index of the l ₂ O ₃ thin film 2 is 1.6 that of Al ₂ O _3.
It was found that the value was almost the same as 3 and did not change. Further, Ta showed no effect of the addition of Ta ₂ O ₅ added amount of ₂ O ₅ is less than 3 wt% relative to Al ₂ O _3, also 1
When it exceeds 0% by weight, the effect of the addition of Ta ₂ O ₅ is remarkable, and it has been found that the refractive index of Ta ₂ O ₅ approaches 2.1.

Next, the high temperature and high humidity of the Al ₂ O ₃ thin film 2 and the single Al ₂ O ₃ thin film deposited on the glass substrate at the substrate heating temperature of 300 ° C. when the added amount of Ta ₂ O ₅ is 15% by weight or less. Experiments were carried out for durability in Table 1, and the results shown in Table 1 were obtained.

[0014]

[Table 1] In this experiment, a film thickness of 0.2 μm and Ta ₂ O
The addition amount of ₅ is 0, 0.5, 2, ₃ , ₅ , 7, 10,
And 15 wt% Al ₂ O ₃ thin film when left a predetermined time in an atmosphere of the Al ₂ O ₃ thin film 2 Temperature 50 ° C., 90% humidity at high temperature and high humidity deposited by each vacuum evaporation
2 appearance change, 1/2 inch width, 1 length after standing
A tape peeling test was performed to evaluate the film peeling after a 00 mm # 600 Scotch tape (trade name) was stuck and rapidly peeled off. The following evaluation symbols were evaluated: ○ = no change × = film Peeling and film crack generation- = Not evaluated and shown in Table 1.

As a result of this experiment, the addition amount of Ta ₂ O ₅ was 3
It was found that the durability was remarkably improved when the content was more than 10% by weight, and the durability was comparable to that of a simple Al ₂ O ₃ thin film deposited on a glass substrate at a substrate heating temperature of 300 ° C. This is Ta ₂
Because by adding O ₅ , the simple substance Al ₂ O ₃ thin film, which has a rough structure at low temperature substrate heating (80 ° C.), changes to the Ta ₂ O ₅ -containing Al ₂ O ₃ thin film 2 having a dense structure. Guessed.

According to the above-mentioned experiment of refractive index and durability, an Al ₂ O ₃ thin film 2 containing 3 to 10% by weight of Ta ₂ O ₅ deposited on a plastic substrate 1 at a substrate heating temperature of 80 ° C.
, By which have been found to have a refractive index and durability of a single Al ₂ O ₃ thin film comparable was deposited at a substrate heating temperature of 300 ° C. on glass substrates, the single Al ₂ O ₃ thin film and similar uses It can be used, for example, as a protective film for the plastic substrate 1.

Next, a Ta ₂ O ₅ -containing Al ₂ O ₃ thin film 2
An example in which is applied to an antireflection film as an intermediate refractive index substance will be described.

FIG. 3 is a view showing an example in which an antireflection film is coated on a glass substrate. In FIG. 3, 3 is a glass substrate, which reduces reflection loss of incident light incident on the glass substrate 3,
The antireflection film 4 is formed on the glass substrate 3 for the purpose of increasing the transmittance.
Be attached to. The antireflection film 4 is formed, for example, by sequentially depositing an intermediate refractive index substance 5 on the first layer, a high refractive index substance 6 on the second layer, and a low refractive index substance 7 on the third layer from the glass substrate 3 side. To be done.

The antireflection coatings 4 having the film configurations and the thicknesses shown in Tables 2 to 5 were formed, and the durability of each of the antireflection coatings 4 was evaluated in the same manner as the above protective coatings. Results were obtained.

[0020]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6] Here, in the film constitution of the antireflection film 4 shown in Table 2, the intermediate refractive index substance 5 of the first layer is Ta having the same refractive index of 1.63 as in FIG.
₂ O ₅ containing Al ₂ O ₃ thin film 2 (Ta ₂ O ₅ + Al ₂ O
₃ ), the high refractive index material 6 of the second layer is Ta ₂ O ₅ having a refractive index of 2.1, and the low refractive index material 7 of the third layer is MgF ₂ having a refractive index of 1.38. In the film constitution of, the first layer is made of a simple substance Al ₂ O ₃ (denoted as Al ₂ O ₃ ) having a refractive index of 1.63, the second layer is made of Ta ₂ O ₅ , and the third layer is made of MgF _2. The film structure of the first layer is Ta ₂ O ₅ + Al ₂
O ₃ , the second layer was made of ZrO ₂ having a refractive index of 2.1, and the third layer was made of MgF _2. Further, the film structure shown in Table 5 was such that the first layer was Al ₂ O ₃ and the second layer was ZrO _2. , And the third layer is Mg
It consists of F ₂ . In addition, Ta _{2 of the} Al ₂ O ₃ thin film ₂
The content of O ₅ is set to 7% by weight with respect to Al ₂ O ₃ .

Further, each of the antireflection films 4 is formed by the vacuum vapor deposition method. (1) Base glass (2) Vacuum degree 6.65 × 10 ^{−3 to} 1.06 × 1
0 ^-2 Pa (5 x 10 ^-5 to 8 x 10 ^-5 Torr) (3) Substrate heating temperature 80 ℃, 250 ℃ (4) Evaporation source Electron beam (5) Evaporation agent Each antireflection film 4 A film was formed under the vapor deposition conditions of a mixture of constituent substances.

As a result of this experiment, film peeling occurred in the antireflection film 4 having the film structure shown in Tables 3 and 5 formed at the substrate heating temperature of 80 ° C. That is, between the first and second layers in Table 3 and _{(Al 2 O 3 -Ta 2 O} 5), between the first and second layers of Table _{5 (Al 2 O 3 -ZrO 2} ) Film peeling occurred during both tests.

Further, the antireflection film 4 shown in Tables 2 and 4 in which the Al ₂ O ₃ thin film 2 containing Ta ₂ O ₅ is applied to the first layer.
Film peeling is not generated in, Al ₂ O ₃ thin film 2 containing Ta ₂ O ₅ is Ta ₂ O ₅ thin film and ZrO
₂ It was found that the adhesive strength with the thin film was strong and showed high durability.

Therefore, the Al ₂ O ₃ thin film 2 containing 3 to 10% by weight of Ta ₂ O ₅ can be used for the antireflection film 4 as an intermediate refractive index substance.

In the above embodiment, each thin film was formed by the vacuum evaporation method, but the present invention is not limited to this, and other methods such as a sputtering method and an ion plating method may be used, and the same operational effect is obtained. can get.

Further, in the above embodiment, the electron beam was used as the covering means, but the present invention is not limited to this, and similar means and effects can be obtained even with covering means such as resistance heating.

Further, the present invention is not limited to the above-mentioned embodiments, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0028]

As described in detail above, according to the aluminum oxide thin film of the present invention, a thin film made of aluminum oxide containing 3 to 10% by weight of tantalum oxide is formed on a substrate in which the substrate heating temperature cannot be raised. Therefore, the aluminum oxide thin film having the same refractive index and durability as the single aluminum oxide thin film deposited by increasing the substrate heating temperature at the substrate heating temperature can be used without the need for a complicated and expensive vacuum evaporation device. It can be formed on a substrate that cannot be raised, and can be used as a protective film of the substrate or an antireflection film as an intermediate refractive index substance.

[Brief description of drawings]

FIG. 1 is a diagram showing an example in which a protective film is attached to a plastic substrate.

FIG. 2 is a diagram showing the relationship between the Ta ₂ O ₅ content and the refractive index of the Al ₂ O ₃ thin film containing Ta ₂ O ₅ of the present invention.

FIG. 3 is a diagram showing an example in which an antireflection film is attached to a glass substrate.

[Explanation of symbols]

 1… Plastic substrate (substrate) 2… Aluminum oxide thin film

Claims (1)

[Claims] 1. An aluminum oxide thin film, characterized in that a thin film of aluminum oxide containing 3 to 10% by weight of tantalum oxide is formed on a substrate on which the substrate heating temperature cannot be raised.