JPH0330135A - Production of thin film - Google Patents

Abstract

PURPOSE:To improve adhesion strength between a resin substrate and film material by subjecting a substrate surface to activation treatment before forming a thin film, and then forming an inorg. dielectric film thereon with using a single element or alloy element as the source material in an atmosphere containing gas which reacts with the element. CONSTITUTION:A polycarbonate plate is used as a substrate 1 and its surface 2 is treated with plasma etching in an Ar discharge gas. Then a base layer 10 of silicon nitride film is formed by reactive sputtering, next the magneto- optical film 3 is formed by sputtering with using TbFeCoNb alloy as the target and Ar discharge gas, and a second dielectric film 4 of silicon nitride is formed. At last, a metal protective film 5 is formed by sputtering using Al35Ti15 alloy as a target in Ar discharge gas. Thereby, adhesion property between the plastics substrate and films formed thereon can be improved, and thus, reliability and functions of the plastics substrate can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming an inorganic dielectric film on a plastic substrate and a method of manufacturing an information recording medium having the thin film. [Conventional technology] Many plastic products are used in modern life. Traditionally made of wood or metal are being replaced one after another. Plastics have the characteristics of being inexpensive and easily mass-produced. However, plastics also have drawbacks such as lower heat resistance and hardness than metals.

By the way, memory cards such as cash cards and IC cards, compact disks, optical disks such as laser disks and magneto-optical disks must have mechanical strength. For this reason, the plastic substrates used in them must be strengthened themselves. Furthermore, in many optical disks, a protective film is formed to sandwich the recording film in order to protect the recording film. Dielectric films made of inorganic compounds are used as these hard coat materials and protective film materials. As a conventional example,
JP-A-61-122955 and JP-A-61-122956 can be mentioned.

[Problem to be solved by the invention]

In the above conventional technology, when forming a dielectric film made of an inorganic compound on a resin, no consideration is given to the adhesion between the resin and the film, resulting in peeling of the film during use of the product, etc. , there were cases where reliability decreased. An object of the present invention is to provide a thin film forming method that improves the adhesion between a resin, a material, and an inorganic compound dielectric film formed thereon.

[Means to solve the problem]

The above object is achieved by applying an inorganic dielectric thin film after the substrate surface has been previously activated.

A particularly effective surface activation treatment method is plasma etching treatment. In addition, effective techniques for film formation include S i ,
Using S i-A flood alloy, 'l''i, T'a, etc. as a source, thin film formation was performed in an atmosphere containing at least one gas selected from N2, CH4, and C◯.

Furthermore, an effective method is to use the above metal element or alloy as a target and perform sputtering in an Ar gas atmosphere containing the above reactive gas. In the present invention, extremely high effects can be obtained because either the surface treatment step or the reactive thin film forming step is effective even when performed alone.

When the present invention is implemented simply as a processing method for hard coat, only hardness and corrosion resistance are required for the dielectric material, but when used as an optical disk, optical properties such as light transmittance and refractive index are also important. becomes a factor.

By controlling the materials and processes used, it is possible to create thin films with desired properties. Furthermore, as an auxiliary method, plasma etching, film formation, or both may be performed while the substrate is heated. The effective temperature at this time is below the softening temperature of the resin on the board. In this case, care must be taken because if the rate of lowering the substrate temperature after film formation is too rapid, separation or cracks may occur depending on the difference in thermal expansion coefficient between the substrate and film. In addition to heating the substrate, another effective method for improving adhesion is to increase the size of the particles when they reach the substrate during film formation.

[Effect]

The case of forming a silicon nitride film for protecting a recording film for an optical disc based on the present invention will be described. After plasma etching the surface of the polycarbonate substrate with Ar, a silicon nitride film was formed by sputtering in an Ar-Nz mixed gas atmosphere using Si as a target. Subsequently, the 6er 4t film, protective film, and gold bending protective film were successively applied.

When this disk was subjected to a beer test and a crosshatch test, no peeling of the film from the substrate was observed. As a comparative example, a silicon nitride film made using a SiaN4 target was formed without surface activation treatment by plasma etching, or a silicon nitride film was made using a SiaN4 target after surface activation by plasma etching. In the case of a method that does not use reactive sputtering and plasma etching in combination, when a beer test was performed, the peeling film was peeled off from the substrate in a part of the area where the tape was applied. Furthermore, no gdJl11 or cracks were observed in the disk according to the present invention even when the disk was placed in a RH of 80 DEG C. to 90 DEG C. for more than 2,000 hours. On the other hand, as in the above-mentioned comparative example, all the disks manufactured not based on the present invention suffered from peeling within 300 hours.

On the other hand, memory cards and plastic plates that require hardness are processed using the sputtering method.
By coating with a film such as N tSiNx g SiA Flood N, a plastic plate with hardness close to that of metal was obtained. This is due to the high hardness of these films. In this example, transparency and optical properties are not required, so hardness and adhesion are important. The former depends on the material, while the latter depends on the manufacturing process. Therefore, as in the case of the optical disk described above, after the substrate surface was plasma etched, a TiN film was formed using a #1 atmosphere containing N2 using 1°i as a target. When the pencil hardness was measured, it was 4H or higher. The improvement is thought to be due to the following. In other words, when sputter etching is performed, the resin surface is cleaned and a uniform surface condition can be achieved.
Non-uniform distribution of adhesive force will not occur. Moreover, the adhesive strength can be enhanced. It is thought that this activates the resin surface and forms a weak chemical bond (such as amide synthesis) between the resin surface and the film material formed thereon, thereby increasing the adhesive strength.

On the other hand, using single elements (Si, Ti, Ta, etc.) or their alloying elements as sources. When a compound film of the above-mentioned element and gas is formed in a reactive atmosphere containing N2, O2, or both, the simple elements take on various valences. Taking Si as an example, some of it exists in the form of Si, and some of it has penetrated into the resin. This increases adhesive strength. In order to further increase this effect, it is possible to spread the effect by increasing the energy of the particles colliding with the resin.In any case, surface treatment by plasma etching of the resin substrate surface and film formation in a reactive atmosphere ensure adhesive strength. This is an essential method, and other methods work to further enhance its effectiveness. Further, it goes without saying that the effects of the present invention can be achieved if not the entire substrate but the surface on which the dielectric film made of an inorganic compound is formed is made of resin.

The scope of application of the present invention is effective for improving the hardness of plastic surfaces, anti-reflection coatings, hard coats, etc., as well as forming protective films for optical discs, optical effect enhancing films, and protective films for memory cards. This allows us to provide Yasutsuku with materials that have properties that replace conventional metals and wood.

〔Example〕

Examples of the present invention will be described below.

[Example 1] This example is a case where a dielectric film made of an inorganic compound is formed on a resin substrate to protect the recording film of an optical disc. The schematic cross-sectional structure of the manufactured optical disc is shown in Figure E. show. A polycarbonate substrate is used as the substrate processing, and the surface 2 is first treated with Ar as a discharge gas, and the gas pressure: IX
1. O-”Torr, input RF power density: 0.32
Plasma etching was performed for 5 minutes at w/ffl.

Here, the etching power and time are determined depending on the material of the substrate, especially its softening temperature.

In addition, the performance of the device itself depends on, for example, the cooling status of the substrate.

Subsequently, a silicon nitride film was formed as the base film 10 by a reactive sputtering method. Pure Si. A r / N x (= 9 0 / 1
0) Using mixed gas, discharge gas pressure: I
Q-2. rr, input RF power: Sputtering was performed for 8 minutes at 6.6 W/d, and the thickness of the formed film 10 was 850 mm, and the refractive index was n=2.05.

Next, a T bx4F 13[11G O12N ha magneto-optical film 3 was formed by a sputtering method. T for target
bFeCoNb alloy using Ar as the discharge gas, Ffr. 'llJ,: 5 X 1 0-8 Tor
r, input RFm power: Suvatsuta was applied for 3 minutes at 4.5 W/d. Then, a silicon nitride film was formed as the second dielectric film 4. The conditions and method were the same as those for base film 10 above. The film thickness is 200 pieces.

Finally, an AI2-Ti metal protective film 5 was formed. The target is An asT i II! The alloy was used and Ar was used as the discharge gas, and the discharge gas pressure:
IX10-2Torr. Input RF power: 2.3
It was sputtered for 3 minutes at W/ci. The thickness of the obtained membrane is 500. As an adhesion test for the disc produced in this way,
First, we conducted a crosshatch test. In this test, 1 mm square mesh scratches were made on the surface using a cutter.
A total of 100 pieces of mesh were formed on each side, each having an area of 10 mm square, and an adhesive tape was pasted thereon.The tape was then rapidly pulled up vertically, and the number of meshes that came off was counted. As a comparative sample, no surface treatment by plasma etching was performed. A similar test was conducted using a silicon nitride base film and a SiaN4 target spattered with Ar.

As a result, in the examples of the present invention, no peeling of the film from the substrate was observed. On the other hand, in the cross-hatch test for the sample of the comparative example, more than 80% of the membranes out of 100 meshes were peeled off.

Next, a temperature and humidity test was conducted. As a result of visually observing the state of film peeling when the above disk was left in a temperature of 80° C. and 90% RH, it was found that the disk produced using the present invention had two
No cracks or peeling occurred even after more than 1,000 hours had passed. Further, no decrease in adhesiveness was observed before and after the test under the above environment. On the other hand, in the disk of the comparative example, peeling occurred within 300 hours.

The above effect can be obtained by using Si-AQ alloy, Zr
, Ta, etc., and was produced in an atmosphere containing oxygen, nitrogen, or a mixture of both gases. However, it is necessary to pay attention to the refractive index and light absorption rate of the inorganic dielectric film as the base film or protective film for the optical disc, or the hard coat film on the surface. Further, although a polycarbonate substrate was used in this example, this effect is not limited to this substrate, and polyethylene terephthalate, acrylic resin, polyolefin resin, borisulfone resin, PMMA resin,
Alternatively, a polyether resin may be used, and it does not depend on the resin material but depends on the manufacturing method.

On the other hand, without plasma etching, a silicon nitride film is immediately deposited on the substrate using a reactive sputtering method.
When we conducted the aforementioned crosshatch test, we found that the adhesion was improved compared to when it was formed using a sputtering method using silicon nitride as a target, but the adhesion was uneven. However, by performing plasma etching, this unevenness in adhesive strength could not be eliminated, and the substrate and base film were in strong contact with each other on all parts of the substrate surface. By increasing the energy of the particles ejected toward the substrate during film formation, it was possible to further increase the adhesive strength without changing other properties. Specifically, in the sputtering method, the above can be achieved by increasing the input RF power density. A similar effect was also obtained by increasing the Ar plasma energy during plasma etching.However, heat is generated during etching, and when the resin surface becomes higher than the curing temperature due to this heat, the substrate may warp or become rough. You have to be careful as it can also cause irritation.

Furthermore, even if the plasma etching and film formation of the present invention are performed while the substrate is heated, it is effective in improving the adhesion between the substrate and the film. In this case as well, care must be taken to avoid overheating the substrate temperature. However, the effect of using a single element as a source in a reactive atmosphere is due to the combination with the plasma etching described above. In addition to improving the adhesive strength with the film, it also affects the quality of the obtained film. Taking the silicon nitride of this embodiment as an example, the film formed by the reactive sputtering method of the present invention hardly incorporates oxygen into the film. On the other hand, the film in which a single nail was formed using SiaNa as a target and Ar as a discharge gas incorporated oxygen into the film. Figure 2 shows the results of measuring the infrared absorption spectra of silicon nitride films formed using two different methods. From this figure, the silicon nitride film formed using the present invention has a thickness of 900 ao-
No absorption was observed other than an absorption peak based on Si--N vibration near '. On the other hand, in the film prepared using SiaNa as a target (comparative example), in addition to the absorption peak based on Si-N vibration near 900 am-', as shown by the broken line,
A peak based on the vibration of Si-0 was measured near "-".A magneto-optical recording medium (recording W/silicon nitride film/AQ-Ti) was formed on these films. When left in the atmosphere for 500 hours, the film produced in a reactive atmosphere showed no change in Kerr rotation angle or coercive force, whereas the comparative sample had a rare earth element sublattice magnetization dominant side (Tb rich composition). ) to a transition metal sublattice magnetization dominant side (Fe-rich composition) via a compensation composition.

This change over time is due to selective oxidation of Tb among the elements constituting the TbFaCoNb recording film.

This phenomenon is clear from the results of measuring the depth profile using Auger electron spectroscopy; when left in the atmosphere at 80°C, the silicon nitride base film and the second dielectric film penetrate into the recording film from the flesh side. It was found that oxygen was diffused. It has been found that forming the film in a reactive atmosphere in this manner not only improves the adhesion to the substrate, but also reduces the concentration of oxygen taken into the eye.

Furthermore, although this example deals with a magneto-optical disk, this effect is effective in any case where an inorganic dielectric film is formed on a plastic base material or a composite base coated with a resin surface. It is. Any film may be formed thereon, regardless of the disk structure or the material from which it is formed.

[Embodiment 2] In this embodiment, an IC card, an optical card, and a cash card are shown. FIG. 3 shows an example of a memory card having a magnetic recording portion. A hard coat was applied to the entire surface of a memory card in which a recording portion 6 was formed on a substrate 7 made of a polyethylene terephthalate resin plate. Before this hard coat format, the entire surface of the card may be covered with resin. In this example, plasma etching was first performed before forming the hard coat film. The conditions at that time were Art I atmosphere, pressure: IX10-2To
rr, the etching time is 3 minutes at an input RF power density of 0.3 W/1. Continuing to use S as a hard coat film
An isNt film was formed. The manufacturing method and conditions are the same as in the example.

An adhesion test using a crosshatch test was conducted on the memory card thus formed. First, scratches were made in a cross pattern at 1m intervals on the card surface, and 100 pieces of mesh were cut out. Tape was applied to this area and then pulled off sharply and perpendicular to the surface. We also conducted a beer test at the same time by applying tape to an undamaged area and peeling it off in the same way as above. As a result, in all tests, the films that remained intact did not peel off from the substrate. In addition, when we examined the pencil hardness of the film formed on this surface, it was found to be 7H or higher, maintaining the hardness originally possessed by these materials.
Even using this method, a chemically and physically stable and strong silicon nitride film was produced.

Next, a temperature and humidity test was conducted on this sample.

As a result, no film peeling or cracking occurred even after being left at 80° C. and 90% RH for more than 2000 hours.

The above-mentioned effect of improving adhesion is determined by the manufacturing process, without depending on the type of plastic or the material of the film to be formed.

[Example 3] In this example, a TaN film was formed on the surface of plastic to increase the surface hardness. A schematic diagram showing the principle of sputtering is shown in FIG. A cylinder made of polymethyl methacrylate resin is used as the base material 20, and during etching and sputtering, a Ta disk is always used as the target 2, and Ar/Nz (=90/10) is used as the discharge gas (reactive gas).
) using each mixed gas, discharge gas pressure I
0-2Torr, input RF power density: 6.7W/c
Sputtering is performed at a rate of about 0.0 mm on the surface of the cylinder 20.
A 5 μm film was formed.

When this film was formed, the surface hardness significantly improved, and the pencil hardness increased from 2B to 7H or higher. Further, even when the Kono cylinder was left in 80° C.-9CJCRH for more than 2,000 hours, no peeling or cracking of the film occurred, and no decrease in adhesion was observed even after leaving it for 2,000 hours. This effect does not depend on the material of the plastic or the material of the film formed, but only on the formation process. [Effects of the Invention] According to the present invention, it is possible to improve the adhesion between the plastic substrate and the film formed thereon, thereby improving the reliability and the function of the plastic. That is, the film does not peel off or crack during use. In addition, the softness, which is one of the drawbacks of plastics, can be modified with a simple method, and the processability is extremely high, equivalent to that of plastics alone.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional structure diagram of an optical disk manufactured according to an embodiment of the present invention, FIG. 2 is an infrared absorption spectrum diagram of a silicon nitride film manufactured according to an embodiment of the present invention, and FIG. FIG. 4 is a schematic diagram showing the outline of the manufactured memory card, and FIG. 4 is a diagram showing the outline of the reactive spatter. Machining...Resin board, 2...Etched part, 2'...
- Base film, 3... Magneto-optical recording film, 4... Second dielectric film, 5... Metal protective film, 6... Part of memory, 7...
・Board, 8... Ha-e-zu-zu-katsu 2 Zuken School (C-1)

Claims (1)

[Claims] 1. In a method of forming an inorganic dielectric thin film on a plastic substrate, the substrate surface on which the thin film is to be formed is activated in advance, and then a single element or an alloyed element is used as a source. , a thin film forming method comprising forming an inorganic dielectric film on the substrate surface in an atmosphere containing a gas that reacts with the element. 2. The above-mentioned inorganic dielectric film forming step includes a step of forming a film having high hardness mainly composed of at least one selected from the group of silicon nitride, titanium nitride, tantalum nitride, and aluminum titanium nitride, and 2. The thin film forming method according to claim 1, further comprising the step of forming a film having optically favorable characteristics. 3. At least the surface of the plastic substrate is selected from the group consisting of polycarbonate resin, acrylic resin, polyether resin, polyolefin resin, polymethyl methacrylate resin, polyethylene terephthalate resin, vinyl chloride resin, or ultraviolet curable resin. 2. The thin film forming method according to claim 1, wherein the thin film forming method is at least one. 4. The thin film forming method according to any one of claims 1 to 3, wherein the activation treatment of the substrate surface includes a surface treatment step using plasma etching. 5. The thin film forming method according to claim 1, wherein the source made of the metal element or alloying element contains at least one selected from the group consisting of Si, Al, Ti, and Ta. 6. At least one gas selected from the group consisting of nitrogen, carbon monoxide, and methane is included as the gas reacting with the single element or alloyed element, and the main component constituting the atmosphere is Ar. The thin film forming method according to any one of claims 1 to 5. 7. The step of forming an inorganic dielectric film on the substrate surface in an atmosphere containing a gas that reacts with the element using the above single element or alloyed element as a source is a reactive sputtering method or a reactive vapor deposition method. Claims 1 to 6 are characterized in that the method is carried out by a method selected from the group consisting of a reactive ion beam sputtering method, a reactive electron beam evaporation method, a chemical vapor deposition method, and a reactive ion platen method.
Thin film forming method described in section. 8. The substrate material is surface activated at a temperature below the softening point of the resin portion, and then the surface of the substrate is activated using a single element or an alloyed element as a source in an atmosphere containing a gas that reacts with the element. 2. The thin film forming method according to claim 1, wherein an inorganic dielectric film is formed on the substrate. 9. According to any one of claims 1 to 8, the resin constituting the substrate is transparent to at least light of a specific wavelength, and more preferably has a light transmittance of 80% or more. Thin film formation method. 10. After performing surface activation treatment on a substrate having a resin layer on the surface having a light transmittance of 80% or more for light of a specific wavelength, a single element or an alloyed element, more preferably Al , Si, Al-Si as a source, a gas that reacts with those elements, more preferably N_2
A method for manufacturing an information recording medium, comprising forming an inorganic dielectric film on the surface of the substrate in an atmosphere containing the above, and further forming an information recording film and a protective film. 11. In the step of forming the inorganic dielectric thin film, the thin film is formed so that a simple element of an element serving as a source and ions of different valences are present in the substrate. Thin film formation method.