JPH04314860A - Formation of metal film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a metal film, and more particularly to a method for dry forming a metal film on the surface of an acrylic resin molded product.

0002

2. Description of the Related Art Conventionally, acrylic resin molded products having metal films formed on their surfaces have been used for decorative goods, optical parts, optical recording media, and the like. Optical discs such as video discs, whose demand has been growing particularly rapidly in recent years, are made by forming a metal film such as aluminum as a reflective film on the surface of an acrylic resin substrate on which pits corresponding to audio signals, image signals, etc. are recorded. .

[0003] Metal films on such acrylic resin molded articles have conventionally been mainly formed by vacuum evaporation, and in recent years attempts have also been made to form films by plasma sputtering (parallel plate plasma sputtering).

[0004] In the vacuum evaporation method, as shown in FIG.
Metal particles 10 such as aluminum are evaporated by electron beam heating or resistance heating and deposited on the surface of each acrylic resin molded product 6, thereby forming a metal film of aluminum or the like on the surface of each acrylic resin molded product 6. This is a method of forming. Each acrylic resin molded product 6 is normally attached to a rotary holder 4 as in this example, but in order to increase the number of films to be formed, a cylindrical vacuum container 2 is installed, for example, as shown in FIGS. 6 and 7. An evaporation source 11 is placed in the center of the vacuum container 2, and a large number of acrylic resin molded products 6 are placed along the entire wall surface of the vacuum container 2. Evaporation source 1
1 has a large number of tungsten heaters 14 suspended between two support columns 12 and a large number of evaporation materials 16 such as aluminum attached to them. Material 1
6 is evaporated. 18 is a current introduction terminal. Further, each acrylic resin molded product 6 is attached to a holder support stand 20.
is attached to a holder 4 supported via a rotating shaft 22, and the whole is rotated in the direction of arrow A within the vacuum container 2, for example.

For example, as shown in FIG. 8, the plasma sputtering method uses a sputtering source (in this example, a magnetron type sputtering source) in which a metal target 28 of aluminum or the like is attached to the top of a magnet 26 in a vacuum chamber 2. 24 and several acrylic resin molded products 6 are arranged to face it, argon gas is introduced into the vacuum container 2, and the magnetic field formed near the surface of the metal target 28 and each acrylic resin molded product 6 (strictly The sputtering source 2 is heated by an electric field applied between the holder 4) and the metal target 28.
4 and each acrylic resin molded product 6, and this plasma 30 causes the metal target 28 to
In this method, metal particles are incidentally deposited on the surface of each acrylic resin molded product 6 by sputtering to form a metal film of aluminum or the like.

[0006]

[Problems to be Solved by the Invention] However, in the case of film formation using the conventional vacuum evaporation method, the adhesion of a metal film such as aluminum to an acrylic resin molded product is strong enough for practical use, but there is variation. is large and lacks stability. Furthermore, the reflectance is proportional to the film thickness at about 600 Å or less, and the film thickness of the metal film such as aluminum is at least 600 Å.
There is a problem in that if the reflectance is less than about .ANG., sufficient reflectance cannot be stably obtained. This is thought to be because the kinetic energy of the deposited metal particles, such as aluminum, is as low as approximately 0.1 eV, so the density and crystal alignment of the metal film deposited on the acrylic resin molded product are not very good. It will be done.

[0007] At present, aluminum metal reflective films are most commonly used in optical discs such as video discs. Particularly in the case of optical discs, when it comes to signal reproduction, the characteristics (for example, S/N) are determined by the shape of the pits as well as the reflectance of the aluminum film formed on the pits, and generally the reflectance is around 70%. Otherwise, a good reproduced image will not be obtained, and the formed aluminum film must be in sufficient adhesion to the acrylic resin substrate due to the production process.

[0008] Furthermore, in order to reduce the cost of optical discs,
It is effective to reduce the thickness of the aluminum film and thereby improve productivity by reducing the amount of material and shortening the film formation time. There was a problem in that the thickness could not be reduced to about 600 Å or less.

Furthermore, the vacuum evaporation method requires less man-hours due to problems such as the lifespan of the resistance heating resistor in the evaporation source (for example, the tungsten heater 14 in FIGS. 5 and 6) and the replenishment of metal such as aluminum, which is the evaporation material. There was a fundamental problem in trying to reduce costs: it required a large amount of energy, and there were limits to productivity improvement and production stability. Such problems are not limited to the method of vapor deposition on many substrates at once (so-called batch method) as shown in the examples of FIGS. 5 and 6, but also the method of vapor deposition on one substrate at a time ( It also exists in the so-called single-wafer type).

On the other hand, in the case of the conventional plasma sputtering method, it is possible to operate continuously until the initially placed metal target such as aluminum is exhausted, which is effective in improving productivity, and the reflectance Also, if the thickness of the metal film such as aluminum is about 500 Å or more, a sufficient reflectance can be stably obtained. However, there is a problem in that the adhesion of the metal film, especially the aluminum film, to the acrylic resin molded product is insufficient.

[0011] This is due to the deterioration of the resin surface (damage to the resin due to temperature) caused by the surface of the acrylic resin molded product being exposed to high-density plasma during film formation, and the high energy applied to the acrylic resin molded product on the anode side. It is thought that impurity gas released from the resin surface due to heating due to the influx of accelerated electrons accelerated by an electric field causes some kind of reaction with the aluminum film, which is the cause of the decrease in the adhesion of the aluminum film. It will be done.

Therefore, the present invention solves the drawbacks of the above two conventional methods and efficiently forms a metal film that has high reflectance even if the film thickness is thin and has good adhesion to an acrylic resin molded product. The main purpose is to provide a method that can be used.

[0013]

[Means for Solving the Problems] In order to achieve the above object, a first method of the present invention is to sputter a metal target using an inert gas ion beam in a vacuum atmosphere, thereby sputtering the surface of an acrylic resin molded product. 50Å~
It is characterized by forming a metal film with a thickness of 400 Å.

[0014] Furthermore, the second method of the present invention is to use means for preventing the plasma from diffusing to the surface of the acrylic resin molded product and preventing accelerated electrons from the plasma from flowing into the surface of the acrylic resin molded product. It is characterized by forming a metal film with a thickness of 50 Å to 400 Å on the surface of an acrylic resin molded product by sputtering a metal target with ions in an inert gas plasma in an atmosphere.

[0015]

[Operation] The first method is called ion beam sputtering, in which the surface of a metal target is hit with an inert gas ion beam, and the metal particles that fly out from there are deposited on the acrylic resin molded product. Form a metal film. In principle, with this method, there is no plasma near the surface of the acrylic resin molded product, and there are also no accelerated electrons emitted from the plasma. Deterioration and generation of impurity gases can be prevented, and as a result,
A highly adhesive metal film can be formed.

The second method technically belongs to the plasma sputtering method, in which the surface of a metal target is hit with ions in an inert gas plasma, and the metal particles flying out from there are incident on an acrylic resin molded product. A metal film is formed by deposition. Moreover, in the case of this invention, the film is formed while using means to prevent the plasma from diffusing to the surface of the acrylic resin molded product and the accelerated electrons from the plasma from flowing into the surface of the acrylic resin molded product. It is possible to prevent the surface deterioration of the acrylic resin molded product and the generation of impurity gas, which are seen in the method, and as a result, it is possible to form a highly adhesive metal film.

The ions and ion beams used in the above method are preferably inert gas ions or ion beams of argon, helium, neon, krypton, xenon, etc., and gas ions or ion beams of other gases such as nitrogen, oxygen, etc. If this is used, there is a risk that it will react with a metal film such as aluminum and reduce the reflectance of the metal film.

[0018] Furthermore, the metal particles such as aluminum sputtered by this method have a moderate kinetic energy of several eV to 20 eV, and this energy contributes to improving the crystallinity of the film. The metal film, such as aluminum, deposited on top has a very dense structure, and therefore has a high reflectance even if the film is thin.

However, according to the experience of the present inventors, metal films produced by ion beam sputtering or the like often have high internal stress and a certain correlation between adhesion and film thickness. Therefore, as a result of evaluating the reflectance and film thickness of metal films of various thicknesses, it was found that a metal film with good reflectance and adhesion can be obtained by setting the film thickness to 50 Å to 400 Å.

The degree of vacuum in the atmosphere during film formation is practically 4.
．． It is sufficient if the vacuum is higher than about 0x10-4 Torr.
In addition, the energy of the ion beam is preferably 100 eV or more, which is the limit of sputtering, and is usually 200 eV to 10
A range of around KeV is easy to use. In this range, the film forming rate is in the range of 1 to 500 Å/sec, and from the viewpoint of production stability, it is preferably 200 to 400 Å/sec or less.

[0021] Examples of the metal target used in the present invention include aluminum, platinum, gold, silver, chromium, and alloys thereof.

The acrylic resin used in the present invention is not particularly limited, but includes, for example, methyl methacrylate polymer,
Methyl methacrylate-alkyl acrylate (C1~
C4) Copolymer, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-cyclohexyl methacrylate-bromhexyl methacrylate copolymer, methacrylate-maleimide copolymer, methacrylate-methacrylimide copolymer, methacrylate-styrene copolymer, etc. High transparency as in
Moreover, resins having other excellent optical properties and resin compositions obtained by mixing these with transparent synthetic resins such as polycarbonate are preferably used.

Further, the shape of the acrylic resin molded product is preferably a disk, other plate, shape with few irregularities, etc., but is not particularly limited. As a method for forming an acrylic resin molded article, commonly used methods such as a casting method, an injection molding method, a compression method, a lamination method, etc. can be employed, and any method may be used.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic diagram showing an example of an ion beam sputtering apparatus for carrying out the method of forming a metal film according to the present invention. A holder 4 that holds an acrylic resin substrate 6a for an optical disk as an example of an acrylic resin molded product and a target holder 32 that holds an aluminum target 28a facing the acrylic resin substrate 6a are provided in the vacuum container 2. And the aluminum target 28a on the target holder 32 is attached to the wall of the vacuum container 2.
The ion source 34 is mounted so as to face. The ion source 34 directs an inert gas ion beam 36 made of ions of an inert gas such as argon to an aluminum target 28a.
The aluminum target 28a is irradiated onto the surface of the aluminum target 28a.
It sputters.

[0025] Using such an apparatus, film formation was performed in the following manner. That is, an acrylic resin substrate 6a with a diameter of 300 mm is mounted on the holder 4, a high-purity aluminum target 28a is mounted on the target holder 32, and the inside of the vacuum container 2 is evacuated to 2.0×10 −7
It was exhausted to Torr. Then, an inert gas ion beam 36 is extracted from the ion source 34 under the following conditions and irradiated with it onto the surface of the aluminum target 28a, and aluminum particles 38 are knocked out from there and deposited on the surface of the acrylic resin substrate 6a. Then, an aluminum film was formed. The film thickness of this aluminum film was adjusted by the film formation time. Ion species: Argon ion Energy: 1500eV Beam current: 300mA

FIG. 2 shows an example of the measurement results of the film thickness-reflectance characteristics of the aluminum film formed on the surface of the acrylic resin substrate 6a as described above. The details are summarized in Table 1 below, but when the film thickness was 50 Å or more, a reflectance of 68% or more was obtained.

In addition, the adhesion of the aluminum film to the acrylic resin substrate 6a was tested by a tape peel test in which the adhesive side of the transparent adhesive tape was sufficiently pressed against the surface of the aluminum film and the tape was quickly peeled off perpendicularly from the surface. When the film thickness was 500 Å or more, peeling of the aluminum film was observed, and when the film thickness was 400 Å, some peeling occurred and some did not, and below that, the adhesion was good and no peeling due to the tape was observed.

These results are summarized in Table 1 together with those of the conventional example for comparison. (Margin below)

[0029]

[Table 1]

[0030] In this table, ◯ indicates good, △ indicates slightly inferior but still usable for practical use, and × indicates poor. Furthermore, the reflectance measurement wavelength used was 780 nm, which is the wavelength of a semiconductor laser for optical discs.

As can be seen from this table, according to the method of the present invention, the thickness of the aluminum film can be reduced from 50 Å to 400 Å.
In other words, 2/2 of the conventional vacuum evaporation method
With a film thickness of 3.3 or less, a reflectance of about 70% or more can be ensured, and moreover, better adhesion can be obtained than in the case of conventional plasma sputtering.

Incidentally, when the image pattern of a video disk in which an aluminum film was formed on an acrylic resin substrate 6a by the above method was reproduced and evaluated, it was found that even though the film thickness was thinner than that of the conventional example, the characteristics (S/ N, etc.) was confirmed to be obtained.

Note that in actual film formation, unlike the above embodiment, the film may be formed on a plurality of acrylic resin substrates 6a at once, and in this case, the uniformity of the aluminum film may be improved. Therefore, each acrylic resin substrate 6a may be rotated.

[0034] As an example other than an aluminum film, thin films are formed on the surface of an acrylic resin molded product using gold, silver, copper, and platinum targets using an ion beam sputtering device similar to that shown in Fig. 1. Formed. The film forming conditions at this time are shown below. Ion species: Argon ion Energy: 1000eV Beam current: 60mA

The measurement results of the reflectance, adhesion, etc. of the metal film formed on the surface of the acrylic resin molded article by this method are summarized in Table 2 together with those of the conventional example for comparison. (Margin below)

[0036]

[Table 2]

In this table, IBS indicates the ion beam sputtering method, PS indicates the conventional plasma sputtering method, and EB indicates the conventional vacuum evaporation method. Further, the reflectance measurement wavelength is 780 nm as described above.

As can be seen from this table, the gold, silver, and copper metal films produced by the method of the present invention have both good reflectance and adhesion as optical discs, etc., and platinum has good adhesion although the reflectance is slightly inferior. It can be said that the results are good and practical. In conventional vacuum deposition methods, gold, silver, and platinum can be used practically in terms of adhesion, but their thin film thickness results in poor reflectance and cannot be used as optical discs. Conventional plasma sputtering methods are all poor in terms of adhesion.

Next, an example of a plasma sputtering apparatus having means for preventing the diffusion of plasma and the inflow of accelerated electrons to the surface of an acrylic resin molded article is shown in FIGS. 3 and 4.

The apparatus shown in FIG. 3 is of the facing target sputtering method, and two metal targets 2 are placed in a vacuum chamber 2.
8 are arranged to face each other, and magnets 40 with different polarities are arranged behind them. 42 is a holder. A plurality of acrylic resin molded products 6 are attached to the holder 4 and arranged around the opposing metal targets 28. 52 is a holder support base. Further, a cylindrical anode 46 is arranged around each metal target 28, respectively. 44 is an insulator.

In this device, when an inert gas is introduced into the vacuum container 2 to an appropriate pressure and a voltage is applied between each anode 46 and each metal target 28, the anode 46 and the metal target 28 and a magnetic field (4) formed between the opposing metal targets 28.
8 schematically shows the lines of magnetic force), a high-density inert gas plasma 30a is generated between both metal targets 28. Moreover, the inert gas plasma 30a is confined by the magnetic field formed between the opposing metal targets 28, and the accelerated electrons trying to exit from the inert gas plasma 30a are similarly confined in the same space by the magnetic field. Damage to the surface of the acrylic resin molded product 6 can be suppressed.

The apparatus shown in FIG. 4 basically uses the magnetron sputtering method like the apparatus shown in FIG. A mesh-like electrostatic shield 54 is placed at a positive potential equal to or higher than that of the holder 4.

[0043] When such an electrostatic shield 54 is used,
an inert gas plasma 30 between it and the sputter source 24;
a is generated, and even if there is no electric field between the electrostatic shield 54 and the holder 4, the inert gas plasma 30a is pushed back, so the inert gas plasma 30a passes through the electrostatic shield 54 and the acrylic resin molded product is 6 side, and the accelerated electrons from this inert gas plasma 30a also flow into this electrostatic shield 54 and do not reach the acrylic resin molded product 6. damage can be suppressed.

The good properties of the metal film formed on the surface of the acrylic resin molded product by the method of the present invention as described above can be widely used for applications other than optical discs, such as metal reflective films for decorative goods, optical parts, etc. It is possible.

[0045]

As described above, according to the present invention, it is possible to form a metal film that has high reflectance even if it is thin and has good adhesion to an acrylic resin molded product. As a result, it becomes possible to reduce the amount of material and the film formation time, thereby improving productivity and reducing the cost of optical discs and the like. In addition, the method of this invention technically belongs to the sputtering method, and unlike the vacuum evaporation method, it is possible to continuously form a metal film until the metal target placed at the beginning is exhausted, so the metal film can be formed efficiently. This also improves productivity.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an ion beam sputtering apparatus for carrying out a method for forming a metal film according to the present invention.

FIG. 2 is a graph showing an example of measurement results of film thickness-reflectance characteristics of an aluminum film.

FIG. 3 is a schematic diagram showing an example of a plasma sputtering apparatus for carrying out the method for forming a metal film according to the present invention.

FIG. 4 is a schematic diagram showing another example of a plasma sputtering apparatus for carrying out the method for forming a metal film according to the present invention.

FIG. 5 is a schematic diagram showing an example of a vacuum evaporation apparatus.

FIG. 6 is a top view showing another example of a vacuum evaporation apparatus.

FIG. 7 is a side view of the device of FIG. 6;

FIG. 8 is a schematic diagram showing an example of a plasma sputtering apparatus.

[Explanation of symbols]

2 Vacuum container 4 Holder 6 Acrylic resin molded product 6a Acrylic resin board 24 Sputter source 28 Metal target 28a Aluminum target 30a Inert gas plasma 34 Ion source 36 Inert gas ion beam 54 Electrostatic shield

Claims (4)

[Claims] 1. A method for forming a metal film on the surface of an acrylic resin molded product, in which a metal film is formed on the surface of the acrylic resin molded product by sputtering a metal target using an inert gas ion beam in a vacuum atmosphere.
A method for forming a metal film, the method comprising forming a metal film with a thickness of 400 Å. 2. A method for forming a metal film on the surface of an acrylic resin molded product, wherein plasma is diffused to the surface of the acrylic resin molded product, and accelerated electrons from the plasma flow into the surface of the acrylic resin molded product. By sputtering a metal target with ions in an inert gas plasma in a vacuum atmosphere while using means to prevent
A method for forming a metal film, comprising forming a metal film with a thickness of ~400 Å. 3. The method for forming a metal film according to claim 1, wherein the metal is aluminum. 4. The method for forming a metal film according to claim 1, wherein the acrylic resin molded product is an acrylic resin substrate for an optical disc.