JP4895902B2 - Method for forming reflective film - Google Patents

Description

  The present invention relates to a method for forming a reflective film for forming a reflective film on the surface of a substrate made of a resin or the like.

2. Description of the Related Art Conventionally, a reflective substrate in which a predetermined reflective film is formed on a substrate is known as a reflective mirror used in an optical system such as a flat panel display or a projector. Such a substrate with a reflective film can be generally obtained by depositing a metal film of Ag (silver) or Al (aluminum) on the surface of a resin film, a resin substrate or the like (hereinafter simply referred to as a substrate). In the case of forming a metal film on the substrate surface, a technique for improving the adhesion between the substrate and the metal film by forming a metal film such as Cr (chromium) between the substrate and the metal film is known. (See Patent Document 1).
JP 2002-200700 A

Such a substrate with a metal film has high adhesion and durability. However, in the film configuration in which a metal film such as chromium and a metal film made of Al or Ag are sequentially formed on the substrate as described above, a certain degree of improvement in adhesion can be expected, but sufficient adhesion while obtaining high durability performance. It is not something that can secure power.
In view of the above-described problems of the prior art, it is an object of the present invention to provide a method of forming a reflective film that can sufficiently secure the adhesion between the substrate and the formed film while obtaining high durability performance.

In order to solve the above problems, the present invention is characterized by having the following configuration.
(1) A first step of forming a first barrier layer made of aluminum oxide on a substrate by ion-assisted deposition, and an adhesive layer made of copper and silver on the barrier layer formed by the first step A second step of sequentially forming a reflective layer, and a third step of forming, by ion-assisted deposition, an increased reflective layer formed by laminating oxide films having different refractive powers on the reflective layer formed by the second step. It is characterized by having.

  According to the present invention, it is possible to sufficiently secure the adhesion between the resin substrate and the formed film while obtaining high durability performance.

This will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing a laminated structure of films formed on a reflection mirror 100 which is a kind of a substrate with a metal film according to an embodiment of the present invention.
Reference numeral 1 denotes a substrate of the reflecting mirror 100, and a general resin material such as acrylic, ZEONEX, polycarbonate, polyethylene terephthalate, or glass is used. The substrate 1 may be a film substrate in addition to a plate material. A multilayer film is formed on the reflective surface side of the substrate 1. The multilayer film in the present embodiment is composed of a base layer (barrier layer) 2, an adhesion layer 3, a reflective layer 4, an increased reflective layer 5, a protective layer 6, and a water repellent layer 7 in order from the substrate side.

The underlayer 2 is a layer provided to prevent (barrier) the movement of moisture from the substrate 1 toward the reflective layer 4 and improve moisture resistance, and is a layer made of a thin film of aluminum oxide (Al ₂ O ₃ ). It is formed by. Such an underlayer (barrier layer) 2 preferably has a physical film thickness of 10 nm to 200 nm. When the film thickness of the underlayer 2 is less than 10 nm, it is difficult to fulfill the function as a barrier layer, and even if it exceeds 200 nm, the barrier performance is hardly improved, which is disadvantageous in terms of productivity.

  The adhesion layer 3 is made of a metal film in order to improve the adhesion between the substrate 1 (underlayer 2) and the reflection layer 4. As the metal material used for the adhesion layer 3, a chromium-based alloy such as copper (Cu), chromium (Cr), nickel (Ni), or a chromium-nickel alloy can be used. The adhesion layer may be a single-layer film, or may be a two-layer film in which a thin film made of chromium and a thin film made of copper are sequentially laminated. The physical film thickness of the adhesion layer 3 is preferably 0.1 nm to 200 nm, more preferably 10 nm to 100 nm. Even if the physical film thickness exceeds 200 nm, the adhesion is hardly improved, which is disadvantageous in terms of productivity. Moreover, if the physical film thickness is less than 0.1 nm, the effect on the adhesion force cannot be obtained. In the reflective film, it is not always necessary to provide the adhesion layer 3 when sufficient adhesion performance is obtained.

  The reflective layer 4 is a layer made of a metal film provided to reflect incident light. Silver (Ag) or aluminum (Al) can be used as the metal material used for such a reflective layer 4. The physical film thickness of such a reflective layer is preferably 10 nm to 300 nm, more preferably 50 nm to 200 nm. When obtaining the reflection mirror 100, even if the physical film thickness exceeds 300 nm, the reflectance is not improved, which is disadvantageous in terms of cracks and productivity. Further, if the physical film thickness is less than 10 nm, it is difficult to obtain a desired reflectance.

The increased reflection layer 5 is a layer provided for protecting the reflection layer 4 and improving reflection characteristics. The increased reflection film 5a shown in the figure is made of aluminum oxide, and forms a part of the increased reflection layer and has a function of preventing moisture from moving to the reflection layer 4 (the same function as the underlayer 2). Such an increased reflection film 5a has a film thickness necessary for a barrier layer and an optical film thickness necessary for increasing reflection. The increased reflection film 5b is a high refractive index oxide film having a refractive index higher than that of the increased reflection film 5a. Specifically, a metal oxide having a high refractive index such as titanium oxide (TiO ₂ ) or zirconium oxide (ZrO ₂ ) can be used. The film thickness (optical film thickness) of the reflective reflection film 5b is such that the reflectance increases when combined with the reflective reflection film 5a described above. Both the reflective reflection films 5a and 5b are generally formed with an optical film thickness of (1/4) λ with respect to the target wavelength (λ). The increased reflection layer 5 is formed by laminating the low refractive index thin film layer and the high refractive index thin film layer in this order, thereby improving the reflection characteristics.

The protective layer 6 is a layer provided to improve wear resistance, and is formed of a silicon dioxide (SiO ₂ ) thin film in this embodiment. The physical film thickness of such a protective layer 6 is preferably 10 nm to 100 nm, more preferably 20 nm to 50 nm.
The water repellent layer 7 is a layer provided to improve moisture resistance and salt water resistance, and a fluorine-containing silicon compound is used. The physical film thickness of the water repellent layer 7 may be about 1 nm to 10 nm. Note that the water-repellent layer 7 is not necessarily provided when saltwater resistance is not required.

Next, a film forming method for obtaining such a substrate with a reflective film will be described. In order to form the multilayer film, a general film forming method such as a vacuum deposition method can be generally used, but in addition to the reflective film performance as shown in the present embodiment, the wear resistance, moisture resistance, etc. When the film structure is for improving durability, sufficient adhesion performance cannot be obtained by film formation by vacuum deposition. As a result of intensive studies, the present inventors have found that sufficient adhesion performance can be obtained by forming a film using ion assisted deposition (IAD) when forming a reflective film. The metal film used for the adhesion layer and the reflective layer may be vacuum deposition. At this time, an ion gun and a neutralizer are provided in the vacuum vapor deposition machine, and the reflective film is efficiently formed on the substrate by configuring the vacuum treatment machine and the vacuum assisted vapor deposition in the same processing machine. It becomes possible. When ion-assisted deposition is performed, Ar and O ₂ are introduced into the ion gun in a vacuum (degree of vacuum: about 1.0 × 10 ^{−2 to} 1.0 × 10 ⁻⁴ Pa), and plasma is introduced. Then, + ions are extracted from the ion gun into the vacuum chamber by a grid to which a voltage is applied from the plasma, accelerated, and irradiated onto the substrate. At the same time as ion irradiation, the vapor deposition material is heated and evaporated by using an electron beam or resistance heating in the same manner as in ordinary vacuum vapor deposition, and the vapor deposition material is vapor deposited on the substrate surface. The film thickness formation status can be detected by a crystal film thickness meter. When a predetermined amount of film thickness is reached, the vapor deposition material is switched to the next vapor deposition material to form a second layer. In addition, the layers not subjected to ion-assisted deposition (adhesion layer, reflective layer) are formed by ordinary vacuum deposition. In this case as well, the film thickness is detected by a crystal film thickness meter.

Hereinafter, the present invention will be described with reference to more specific Examples 1 to 5 and Comparative Examples 1 to 7. However, the present invention is not limited to the following examples.
<Example 1>
As substrate 1, ZEONOR (registered trademark) (Nippon ZEON Co., Ltd.), which is a cycloolefin resin, is used, and the base layer (first layer) is formed on the substrate using the above-described vacuum vapor deposition machine with ion-assisted vapor deposition function. ), An Al ₂ O ₃ film was formed by ion-assisted deposition with a physical film thickness of 68 nm. Next, as an adhesion layer (second layer), a Cu film was formed by vacuum deposition at a physical film thickness of 40 nm, and as a reflective layer (third layer), an Ag film was formed in order by vacuum deposition at a physical film thickness of 150 nm. Further, as an additional reflection layer (fourth layer), an Al ₂ O ₃ film has an optical film thickness of 110 nm ((1/4) λ where λ = 440 nm), and a TiO ₂ film has an optical film thickness of 110 nm ((1/4) λ where λ = 440 nm) in this order by ion-assisted deposition. Next, a SiO ₂ film is formed as a protective layer (fifth layer) by ion-assisted vapor deposition with a physical film thickness of 21 nm (optical film thickness 30 nm), and further the physical film thickness is formed using OF-110 (manufactured by Optron) as the outermost layer. A water-repellent layer was formed by vacuum deposition at 10 nm to obtain a substrate with a reflection film (reflection mirror).

The obtained board | substrate with a reflecting film was measured with the spectrophotometer, and the reflective characteristic (45 degree reflectance) was test | inspected. Moreover, as durability evaluation, the adhesiveness test, the abrasion test, and the moisture resistance test were done. The adhesion test was performed by a cross-cut tape test. In the cross-cut tape test, 100 pieces of 1 mm ² squares are formed on the substrate surface (film formation surface) with 1 mm intervals. The adhesion is evaluated by examining how many remain (conforms to JIS K5400). If all the cells were left, it was marked as ◯, and if even one cell was removed, it was marked as x. The abrasion test was conducted according to MIL-M-13508. After the abrasion test, the appearance inspection and the reflectance were measured again. If the appearance was good and the decrease in reflectance was within 1%, it was rated as ◯, and otherwise. In the humidity resistance test, the substrate after film formation was placed in an atmosphere of room temperature 60 ° C. and humidity 95% for 240 hours, and then the appearance inspection and the reflectance were measured again, and the appearance was good and the reflectance decreased. If it was within 1%, it was rated as ◯, otherwise it was marked as x. The results are shown in Table 1. The reflectance characteristics are shown in FIG.

<Example 2>
In Example 2, all the conditions were the same as in Example 1 except that the water repellent layer was not formed. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Example 3>
In Example 3, the same conditions as in Example 1 were used except that the water-repellent layer was not formed and a chromium-nickel alloy (chromel) was used for the adhesion layer. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Example 4>
In Example 4, the same conditions as in Example 1 were used except that the water-repellent layer was not formed and nickel (Ni) was used for the adhesion layer. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Example 5>
In Example 5, all the conditions were the same as in Example 1 except that the water repellent layer and the adhesion layer were not formed. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 1>
In Comparative Example 1, the same film configuration as in Example 2 was used, but ion-assisted deposition was not performed, and deposition was performed on all layers using vacuum deposition. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative example 2>
In Comparative Example 2, the same film configuration as in Example 3 was used, but ion-assisted deposition was not performed, and deposition was performed on all layers using vacuum deposition. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 3>
In Comparative Example 3, the same film configuration as in Example 4 was used, but ion-assisted deposition was not performed, and deposition was performed on all layers using vacuum deposition. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative example 4>
In Comparative Example 4, the same film configuration as in Example 5 was used, but ion-assisted deposition was not performed, and deposition was performed on all layers using vacuum deposition. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 5>
In Comparative Example 5, the film configuration was the same as that of Example 2 except that the base layer (Al ₂ O ₃ film) was not formed, but ion-assisted deposition was not performed, and all layers were formed using vacuum deposition. Went. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Comparative Example 6>
In Comparative Example 6, the film configuration was the same as in Example 2 except that the protective layer (SiO ₂ film) was not formed, but ion-assisted deposition was not performed, and all layers were deposited using vacuum deposition. It was. The obtained substrate with a reflective film was measured with a spectrophotometer, and its reflection characteristics were examined. Further, durability evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

<Result>
In Examples 1-5, while ensuring a reflectance of 95% or more, high durability performance and high adhesion can be obtained. On the other hand, Comparative Examples 1 to 4 have the same film configuration and ensure a reflectance of 95% or more, but it is not preferable because sufficient adhesion cannot be obtained. In Comparative Example 5 and Comparative Example 6, both adhesion and durability (abrasion resistance and moisture resistance) were not good.

It is the schematic which showed the film | membrane structure of this embodiment. FIG. 3 is a diagram showing the reflectance characteristics of the reflecting mirror of Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Base layer 3 Adhesion layer 4 Reflective layer 5 Increasing reflective layer 6 Protective layer 7 Water repellent layer 100 Reflective mirror

Claims (1)

A first step of forming a first barrier layer made of aluminum oxide on a substrate by ion-assisted deposition, and an adhesion layer made of copper and a reflective layer made of silver on the barrier layer formed by the first step A second step of sequentially forming, and a third step of forming, by ion-assisted deposition, an increased reflection layer formed by laminating oxide films having different refractive powers on the reflection layer formed by the second step. A method for forming a reflective film, comprising:

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