JP2014191841A - SiO2 FILM COATING ALUMINUM PLATE AND METHOD FOR PRODUCING THE SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a SiOfilm coating aluminum plate excellent in hardness and thermal resistance, and a method for producing the same.SOLUTION: An aluminum plate includes a SiOfilm formed thereon. When the temperature of the aluminum plate on which inorganic polysilazane containing liquid is coated is 100 to 250°C, an addition of steam is started, and it is calcinated.

Description

The present invention relates to a SiO ₂ film-coated aluminum plate suitable as a material for electrical and electronic equipment such as various electronic equipment substrates and magnetic recording medium (magnetic disk) substrates, and a method for producing the same.

  An aluminum plate (including pure aluminum and an aluminum alloy, the same applies hereinafter) is low in cost of acquisition, non-magnetic, and excellent in workability. Therefore, it is widely used as various materials for electric and electronic devices such as various electronic device substrates and magnetic recording medium substrates.

  The aluminum plate may be subjected to surface treatment or the like in order to impart characteristics according to the application. For example, a substrate for a magnetic recording medium is required to have a smooth surface and excellent hardness. In order to give such required characteristics, electroless NiP plating may be applied to the surface of the aluminum plate by a manufacturing method as described in Non-Patent Document 1, for example (NiP plated aluminum plate).

  For example, in a magnetic recording medium, a soft magnetic backing layer, an intermediate layer (crystal grain control layer, crystal orientation control layer, etc.), etc. are formed on a NiP plated aluminum plate (substrate), and a magnetic film is formed thereon as a recording layer. Furthermore, a surface protective layer (such as hard carbon) is formed.

  In recent years, the capacity of magnetic recording media has been increasing, and next-generation magnetic recording media that dramatically increase recording density have been developed. To increase the density of the magnetic recording medium, it is necessary to make the magnetic particles finer. However, when miniaturization occurs, there arises a problem of thermal fluctuation in which part of the magnetic recording data disappears due to the influence of the surrounding heat. Therefore, a magnetic recording medium in which the coercive force of the magnetic film is increased has been proposed. However, when the coercive force is increased, it becomes difficult to record data with a conventional head. For this reason, attention has been paid to a heat-assisted recording method in which data is recorded while a recording medium is heated by a laser. In this recording method, data can be recorded because the coercivity of the heated portion of the magnetic film formed on the magnetic recording medium is reduced, and thermal fluctuation can be eliminated because the non-heated portion has high coercivity.

  In the process of manufacturing a magnetic recording medium suitable for such a heat-assisted recording method, the thermal history during manufacturing, such as the film formation temperature of the magnetic film, may be 300 ° C. or higher, and further 350 ° C. or higher. In the case of NiP-plated aluminum plates that are currently widely used, the heat resistance of the underlying aluminum plate is 370 ° C or higher, but NiP plating crystallizes and becomes magnetic when heated to 300 ° C or higher. It can only handle up to about 300 ° C., and the heat-resistant temperature of the substrate is a major limitation in the production of magnetic recording media.

  In order to solve this problem, an attempt has been made to improve the heat resistance of the NiP plating film by adding a third component (Patent Document 1), but it has a heat resistance of up to about 320 ° C. and has a sufficient heat resistance improvement effect. Is not obtained.

For this reason, an amorphous SiO ₂ film has attracted attention as a nonmagnetic, high hardness, and excellent heat resistance alternative to the current NiP plating.

As a method for forming the SiO ₂ film, a dry silica coating method such as a chemical vapor deposition method (CVD method) or a vapor phase growth method (sputtering method), a sol-gel method or a silica precursor is applied and baked. Wet silica coating methods are known.

When the SiO ₂ film is formed by the dry silica coating method, for example, the CVD method may cause a risk associated with the use of a toxic gas such as silane gas. Further, the sputtering method has a problem that it takes time to form a film and the equipment is enlarged.

On the other hand, a wet silica coating method has been adopted as a film forming method that does not cause the above problem. For example, when a film is formed by a sol-gel method, mass reduction and volume shrinkage due to a condensation reaction are large, and pinning is performed on the SiO ₂ film. There was a problem that hole defects were formed.

Various techniques for forming a SiO ₂ film by applying and curing a polysilazane-containing solution as a precursor have been proposed as a wet silica coating method that does not cause a large mass loss as in the sol-gel method.

For example, in Patent Document 2, a polysilazane-containing solution (precursor) is coated on the surface of an aluminum plate, and this is fired in a temperature range of 200 to 400 ° C. in N ₂ , NH ₃ , or air atmosphere to produce silicon nitride. A technique for forming a continuous thin film is disclosed.

Patent Document 3 discloses that a substrate coated with a cyclosilazane polymer substance-containing solution (precursor) is heated to 400 to 450 ° C. to change the coating to insoluble and infusible, and then an oxygen or water vapor atmosphere. Among them, a technique for forming a SiO ₂ film by heating to about 900 ° C. is disclosed.

Further, in Patent Document 4, after a polysilazane solution (precursor) is coated on a substrate, it is brought into contact with amines and water vapor at a temperature of 0 ° C. to 100 ° C., and then baked in a dry atmosphere to produce SiO 2. A technique for forming _two films is disclosed.

JP 2012-195021 A JP-A-4-252420 JP-A-62-88327 Japanese Patent No. 4053105

Journal of Abrasive Technology, Vol. 43, no. 11, November 1999, p. 475-479

When depositing the SiO ₂ film on the surface of the aluminum plate using techniques (Patent Documents 2 to 4) for forming the SiO ₂ film of the above polysilazane-containing solution is coated and cured, the following problems are I found it to happen.

For example, in the technique of Patent Document 2, the film hardness is insufficient (about 2.1 GPa), and there are problems such as cracks in the SiO ₂ film and separation of the SiO ₂ film from the aluminum plate. It was low.

  Moreover, in the technique of patent document 3, since the heating temperature for silica conversion is 900 degreeC and higher than melting | fusing point of an aluminum plate, the application to an aluminum plate was impossible.

  Furthermore, the technique of Patent Document 4 requires a facility for contacting with amines and a facility for heat treatment in a dry atmosphere, which causes an increase in manufacturing cost.

The present invention has been made paying attention to the above-described circumstances, and an object thereof is to provide a SiO ₂ film-coated aluminum plate excellent in hardness and heat resistance, and a method for producing the same.

The present invention capable of solving the above problems is the addition of water vapor when the temperature of the aluminum plate coated with the inorganic polysilazane-containing liquid is 100 to 250 ° C., on which the SiO ₂ film is formed. It has a gist that it has been fired.

  In the present invention, it is also a preferred embodiment that the final temperature during the firing is 370 ° C. or lower.

Further, the present invention provides a method for producing an aluminum plate in which an inorganic polysilazane-containing liquid is applied to the surface of an aluminum plate, and then an aluminum substrate is continuously heated and fired to form a SiO ₂ film. The gist is that the addition of water vapor is started when the temperature of the aluminum plate is 100 to 250 ° C.

  In the present invention, the final temperature at the time of firing is preferably 370 ° C. or less, and it is also preferable to apply the inorganic polysilazane-containing liquid after removing the rolled surface of the aluminum plate surface. This is an embodiment.

In the present invention, the inorganic polysilazane-containing solution is applied to the surface of the aluminum plate, and then the aluminum plate is heated to start addition of water vapor at a predetermined temperature. 350 ° C. or more, further has preferably excellent 400 ° C. or higher), also the hardness of the comparable glass (preferably 4.0GPa or more, more preferably 5.0GPa or more, SiO ₂ film preferably has a 8.0GPa or less) A coated aluminum plate and a manufacturing method thereof can be provided.

Therefore, the SiO ₂ film-coated aluminum plate of the present invention greatly relaxes restrictions on the use of the aluminum plate for various electrical and electronic equipment applications such as magnetic recording medium substrates and electronic device substrates that require high hardness and heat resistance. be able to.

Hereinafter, the present invention will be described. In the present invention, the “firing temperature” is the temperature of the aluminum plate itself when the SiO ₂ film is formed, and is the temperature measured by installing a thermocouple on the aluminum plate. is there.

The “heat resistance evaluation temperature” is the temperature of the aluminum plate itself when the aluminum plate coated with the SiO ₂ film is exposed to a high temperature environment in various processing / manufacturing processes such as a magnetic recording medium substrate, It is the temperature of the aluminum plate measured with a thermocouple as described above.

In the present invention, the set temperature of the apparatus and atmosphere when forming the SiO ₂ film, magnetic film, etc., and the firing temperature (aluminum plate temperature) and heat resistance evaluation temperature (aluminum plate temperature) may not match. is there. For example, in an embodiment of the present invention, in order to evaluate the heat resistance of an aluminum plate on which a SiO ₂ film is formed, a thermocouple is attached to the aluminum plate in advance, and the relationship between the temperature in the electric furnace and the temperature of the aluminum plate is examined. Since the temperature of the electric furnace is set so that the temperature of the aluminum plate becomes a temperature simulating the thermal history of the manufacturing process, the temperature of the electric furnace may not match the temperature of the aluminum plate.

The inventors of the present invention have made extensive studies on the formation of a SiO ₂ film having a hardness comparable to that of glass (4.0-8.0 GPa) and excellent heat resistance that surpasses the NiP plating film. Specifically, focusing on inorganic polysilazane, an SiO ₂ film-coated aluminum plate formed by coating and baking an inorganic polysilazane-containing solution (precursor) was studied.

This is because the SiO ₂ film obtained by subjecting inorganic polysilazane to a silica conversion reaction is harder than the aluminum plate and can increase the surface hardness of the aluminum plate. Furthermore, the SiO ₂ film is excellent in the heat resistance, and the heat evaluation temperature can be improved.

First, when a SiO ₂ film by coating the inorganic polysilazane on a silicon wafer, cracks or generated in the SiO ₂ film even by firing at a temperature above 400 ° C. in an air atmosphere, the SiO ₂ film separation (No. 11 in Table 1).

However, when an inorganic polysilazane is coated on an aluminum plate to form a SiO ₂ film, when the firing temperature reaches about 300 ° C. (the aluminum plate temperature during firing), the SiO ₂ film cracks or the SiO ₂ film It was found that problems such as peeling from the aluminum plate occurred (No. 3 in Table 1).

On the other hand, even when the film is formed on an aluminum plate, if the firing temperature is set to 250 ° C. or lower, cracks or the like of the SiO ₂ film does not occur, but there is a problem that sufficient hardness and heat resistance cannot be obtained (Table 1). No. 1, 2).

Therefore, as a result of studying the film forming conditions of the SiO ₂ film, the present inventors have used inorganic polysilazane as a precursor for forming the SiO ₂ film on the aluminum plate, and water vapor as an oxygen source necessary for the silica conversion reaction. It was found that the above-mentioned problems can be achieved by adding water and further appropriately controlling the addition start timing (temperature range) of water vapor. The background is as follows.

In the formation of a SiO ₂ film, it is known to use inorganic polysilazane as a precursor or to use water vapor as an oxygen source, and the silica conversion reaction may proceed due to the reaction between inorganic polysilazane and water at high temperatures. It is known (the following formula (1)).

_{- (SiH 2 -HN) n- +} 2nH 2 O → nSiO 2 + nNH 3; 2nH 2 ··· Equation (1)
(N is an arbitrary integer)

  Further, when water vapor is added as an oxygen source, silica can be converted more efficiently than when heated in the atmosphere. Therefore, attention was paid to the fact that the final firing temperature can be set lower than the temperature at which the aluminum plate is deformed.

However, since the thermal expansion coefficient of the aluminum plate (generally, around 24 × 10 ⁻⁶ / K) is larger than the thermal expansion coefficient of the SiO ₂ film (about 1 × 10 ⁻⁷ to 1 × 10 ⁻⁶ / K), the firing temperature It was found that when the difference in thermal expansion between the aluminum plate and the SiO ₂ film increases during the heating process, the SiO ₂ film cracks and peels off.

Therefore, research was repeated on manufacturing conditions capable of suppressing cracks and peeling of the SiO ₂ film caused by the difference in thermal expansion. As a result, in the process of heating to firing temperature, temperature of the aluminum plate during firing the addition of water vapor to begin at 100 ℃ ~250 ℃, SiO ₂ is heated to a firing temperature required to more fully silica conversion It has been found that a film may be formed. The SiO ₂ film-coated aluminum plate produced in such conditions has been found possible to obtain a high hardness and heat resistance than conventional.

  The reason why water vapor is added in a specific temperature range is as follows. When the addition of water vapor is started when the temperature of the aluminum plate is less than 100 ° C., for example, an atmosphere having a water vapor partial pressure of 65% may cause dew condensation if it touches piping or the inner wall of a furnace at 90 ° C. or lower. For this reason, if condensation occurs on the water vapor introduction path (pipe), the inner wall of the firing furnace, or the aluminum plate, the silica conversion reaction cannot be performed stably and efficiently with good reproducibility.

On the other hand, even if water vapor is added after the temperature of the aluminum plate exceeds 250 ° C., the inorganic polysilazane reacts with oxygen in the atmosphere and partially converts to SiO ₂ film during the temperature rising process until the water vapor is added. Since the film is formed with insufficient strength, the SiO ₂ film is cracked or peeled off before the water vapor is added.

  Therefore, it was found that the addition of water vapor needs to start at a temperature range of 100 ° C. to 250 ° C. of the aluminum plate during firing.

In order to obtain the above effect, in the present invention, after adding water vapor at a predetermined temperature (calcination temperature: 100 ° C. to 250 ° C.), continuously or intermittently until the final calcination temperature at which the silica conversion is completed. The addition of water vapor is continued. That is, in this invention, even if the temperature of the aluminum plate at the time of baking exceeds 250 ° C., the water vapor atmosphere is sufficient for the conversion until the final baking temperature (including the holding time after reaching the final temperature at the time of baking). It is desirable to supply water vapor continuously or intermittently. For example, when the addition of water vapor is stopped at 250 ° C. and a dry atmosphere is obtained, the reaction with water vapor stops in a temperature range above 250 ° C., so that the conversion to the SiO ₂ film becomes insufficient.

  Hereinafter, the manufacturing method of the aluminum plate of this invention is demonstrated.

  The aluminum plate used in the present invention is not particularly limited, and various known aluminum alloy plates (commercially available products can be used, such as AA5086, KS5C86, KS5D86, etc.) or pure aluminum plates depending on the application. Can do. As the aluminum plate, it is preferable to use an aluminum alloy having high heat resistance.

  The plate thickness of the aluminum plate is not particularly limited, and the plate thickness may be a commonly used thickness. For example, an aluminum substrate for a magnetic recording medium having a diameter of 3.5 inches has a thickness of about 1.2 to 1.8 mm, but is not limited thereto.

  It is recommended that the aluminum plate is punched into a desired shape and annealed. By performing the annealing treatment, the shape of the aluminum plate is fixed, and the residual stress can be removed. The annealing process may be performed at a temperature of 300 ° C. or higher, for example.

Since the surface alteration layer resulting from rolling or the like may be formed on the surface of the aluminum plate, it is desirable to remove the rolling surface by grinding or cutting the surface alteration layer as necessary. When the inorganic polysilazane-containing solution is applied after removing the rolled surface of the aluminum plate surface, the leveling effect of the inorganic polysilazane-containing solution is reduced to reduce the surface roughness of the aluminum plate after the SiO ₂ film is formed. Can be improved (FIG. 1). The amount of removal of the surface altered layer is not particularly limited, but may be, for example, about 10 to 20 μm per side.

  The leveling effect by coating the inorganic polysilazane-containing liquid is an effect of improving the surface smoothness. That is, when the inorganic polysilazane-containing solution is applied to the fine irregular surface formed on the surface of the aluminum plate after the surface alteration layer is removed, the inorganic polysilazane-containing solution penetrates into the recesses, and the aluminum substrate surface can be smoothed. .

In the present invention, since the surface smoothness can be improved by the leveling effect, strictly speaking, it is not necessary to control the surface properties of the aluminum plate after the surface alteration layer is removed. However, an inorganic polysilazane-containing solution may be applied after performing surface polishing so as to obtain a desired surface smoothness (for example, about 10 nm) if necessary. In this case, after the SiO ₂ film is formed, The surface roughness can be reduced and the smoothness can be further improved.

[Coating of inorganic polysilazane-containing solution]
After processing into the desired shape, an inorganic polysilazane-containing solution is applied to the aluminum plate surface (arbitrary surface).

Inorganic polysilazane has “— (SiH ₂ NH) —” as a basic structural unit, does not contain organic components such as methyl groups in the basic structural unit, and is composed of a chain, a ring, or a composite structure thereof. It is a material that reacts with oxygen and moisture to convert to hard SiO ₂ (see, for example, Japanese Patent Application Laid-Open No. 60-145903).

  Specifically, as the inorganic polysilazane, perhydropolysilazane can be preferably used. As said inorganic polysilazane, it is preferable to use that whose number average molecular weight is about 500-2500, for example.

  As the inorganic polysilazane-containing solution, a solution in which inorganic polysilazane is dissolved may be used, and as the solvent, for example, an organic solvent such as dibutyl ether, xylene, or toluene can be used. Although the density | concentration of the inorganic polysilazane contained in an inorganic polysilazane containing solution is not specifically limited, For example, Preferably it is 10 mass% or more with respect to the mass of the whole solution, More preferably, it is 20 mass% or more.

The inorganic polysilazane-containing solution preferably further contains a catalyst for accelerating the conversion of inorganic polysilazane to SiO _2. For example, a SiO ₂ film can be formed at a relatively low temperature by adding a palladium catalyst. Therefore, the SiO ₂ film can be formed within the heat resistance temperature of the aluminum plate.

  A commercial item may be used for the said inorganic polysilazane containing solution, for example, it can obtain from AZ Electronic Materials. Moreover, you may use, after concentrating the obtained solution.

  As polysilazane, in addition to inorganic polysilazane, organic polysilazane containing an organic component such as methyl group in the basic structural unit is also known, but it is difficult to form a three-dimensional Si-O bond at low temperature, and silica conversion However, since organic polysilazane is inferior in heat resistance to inorganic polysilazane, organic polysilazane is not used in the present invention.

  The method for applying the inorganic polysilazane-containing solution to the surface of the aluminum substrate is not particularly limited, and a known method can be employed. For example, methods such as spin coating, dip coating, and spray coating can be applied.

The coating amount of the inorganic polysilazane-containing solution is not particularly limited. Therefore, the coating amount may be appropriately adjusted according to the thickness of the SiO ₂ film to be formed.

The film thickness of the SiO ₂ film after film formation is not particularly limited. If the film thickness of the SiO ₂ film formed on the aluminum plate is thin, the aluminum plate tends to be wrinkled, and the function as a protective film is lowered. Therefore, the thickness of the SiO ₂ film is preferably 1 μm or more, more preferably 2 μm or more. On the other hand, the upper limit of the film thickness is not particularly limited. However, since the time required for the silica conversion reaction increases as the SiO ₂ film becomes thicker, for example, it is preferably 15 μm or less, more preferably 12 μm or less.

  After coating the inorganic polysilazane-containing solution, it is preferable to remove the solvent by drying as necessary. The drying method is not particularly limited. For example, the solvent may be removed by drying at a desired temperature in the air or in a dry atmosphere (that is, an atmosphere not containing water vapor such as dry air or dry nitrogen).

[Baking]
The aluminum plate is coated with the inorganic polysilazane-containing liquid, or further dried, and then inserted into a firing furnace (heating furnace such as an electric furnace) and heated to convert the inorganic polysilazane to silica to mainly contain SiO _2. A hard film (SiO ₂ film) is formed.

  The aluminum plate inserted into the firing furnace is heated to the final firing temperature. In the present invention, as described above, the temperature of the aluminum plate is between 100 to 250 ° C. (preferably 150 to 250 ° C.), and steam is introduced into the firing furnace. Then, the inside of the furnace is made a steam atmosphere. It should be noted that an air atmosphere may be used until water vapor is added.

  The method for supplying water vapor is not particularly limited. For example, an atmospheric gas (water vapor partial pressure controlled by flowing a predetermined amount of air or the like while dropping a predetermined amount of water in a high-temperature vaporizer provided outside the firing furnace ( Water vapor gas) may be supplied into the firing furnace.

The amount of water vapor supplied into the firing furnace is not particularly limited because it varies depending on the size of the firing furnace, the number of aluminum plates to be fired, the size, and the like. The supply amount of water vapor is appropriately adjusted so that a film (SiO ₂ film) mainly composed of SiO ₂ having the strength and heat resistance can be formed by reacting with water supplied with at least inorganic polysilazane (silica conversion reaction). do it. The water vapor partial pressure to be supplied is not particularly limited, and may be, for example, about 20 to 70%.

The film mainly composed of SiO ₂ is caused by Si—H bond and N—H bond when the FT-IR (Fourier transform infrared spectrophotometer) spectrum of the film before and after heating is measured. It can be confirmed from the fact that the peak intensity decreases or disappears, and the peak due to the Si—O bond is generated or the peak intensity is increased. When firing without a steam atmosphere, for example, No. 1 in Table 1. 11, the absorption coefficients of the characteristic absorptions of Si—H bonds and N—H bonds appearing near 2300 cm ⁻¹ and 3400 cm ^{−1 are} 1/10, compared with the absorption coefficient of the characteristic absorption of Si—O bonds appearing near 1120 cm ^−1. Decrease to about 50. In contrast, when firing in a humidified atmosphere, for example, No. 1 in Table 1. When firing in a water vapor atmosphere as in No. 5, the characteristic absorption of Si—H bonds and N—H bonds falls below the detection limit.

After that, steam is supplied and heated to a predetermined final firing temperature while maintaining the inside of the firing furnace in a steam atmosphere to convert to silica, whereby an aluminum plate coated with a hard SiO ₂ film can be obtained.

  The upper limit (final firing temperature) of the final temperature during firing is not particularly limited, but if the final firing temperature is too high, the aluminum plate is deformed, so it is necessary to set it to a temperature lower than the heat resistance temperature (deformation start temperature) of the aluminum plate. There is. Although the heat resistance temperature of the aluminum plate varies somewhat depending on the alloy component, etc., when it exceeds approximately 370 ° C., the proof stress of the aluminum plate decreases to about ¼ of the room temperature and easily changes. On the other hand, the silica conversion of the inorganic polysilazane is promoted when the temperature is 200 ° C. or higher, and the hardness becomes higher as the temperature becomes higher. Therefore, the lower limit of the final firing temperature is preferably 200 ° C. or higher, more preferably 250 ° C. or higher.

  The holding time at the final calcination temperature is not particularly limited as long as the silica conversion is completed, and is preferably 30 minutes or more, and more preferably 1 hour or more, for example.

  Moreover, the temperature increase rate of the temperature in the firing furnace is not particularly limited, and may be performed under normal production conditions, for example, about 3 ° C./min to 10 ° C./min (average temperature increase rate).

  Although it cools to room temperature after the said baking, the cooling rate in that case is not specifically limited, For example, what is necessary is just to cool.

The thus obtained SiO ₂ film-coated aluminum plate of the present invention has an aluminum plate with increased surface hardness and excellent heat resistance.

Further, the SiO ₂ film-coated aluminum plate of the present invention has a smoothed film surface after the formation of the SiO ₂ film, as compared with the conventional production method, due to the leveling effect due to the application of the inorganic polysilazane-containing solution. Of course, for the purpose of further improving the smoothness, the SiO ₂ film surface may be polished, ground or cut under known conditions. In the present invention, since a hard SiO ₂ film is formed on the surface of the aluminum substrate, a conventionally used method or apparatus for polishing a glass substrate can be used as it is.

For example, when used as a substrate for a magnetic recording medium, the surface roughness of the SiO ₂ film is preferably as small as possible, and the polishing is performed by, for example, expanding the arithmetic average roughness Ra defined in JIS B0601 to three dimensions. The average roughness Sa defined as the volume of the portion surrounded by the surface shape phase and the average plane divided by the measurement area may be 1 nm or less when the observation field is 2 μm square. It is preferable to perform the treatment so that the thickness is 0.6 nm or less, more preferably 0.4 nm or less.

  The aluminum plate of the present invention can be suitably used as a material for various electric and electronic devices such as a magnetic recording medium substrate.

  In manufacturing a magnetic recording medium using the aluminum plate of the present invention, a magnetic recording film is formed on the surface of the aluminum plate under known conditions, and if necessary, a protective film or a lubricating film is further formed. Good.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited by the following examples, but may be appropriately modified within a range that can meet the purpose described above and below. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

Test material No. 1-3
An aluminum plate (aluminum alloy (4.2% by mass Mg—balance: Al and inevitable impurities), size: outer disk 65 mm, inner diameter 20 mm, disk disk with a thickness of about 0.84 mm, hardness: 0.7 GPa) is PVA. Grinding with a grindstone removed the altered layer by rolling. For grinding, a Speed Fam 16B double-sided machine was used, grinding pressure: 80 gf / cm ² , sliding speed: 80 cm / sec, removal amount per surface: about 20 μm, polished aluminum plate The thickness was set to 0.80 mm. The surface roughness of the aluminum plate after grinding was measured by a stylus method (Taylor / Hobson's intra) and AFM (Nanoscience Instruments, Nanosurf EasyScan 2).

On this aluminum plate, an inorganic polysilazane-containing solution (NL120A-20 manufactured by AZ Electronic Materials) was applied by a spin coating method so that the thickness of the fired SiO ₂ film was 2.1 μm, and it was heated at 80 ° C. in an air atmosphere. For 5 minutes to remove the solvent. Thereafter, the aluminum plate was inserted into an electric furnace (firing furnace), heated to the final firing temperature shown in Table 1 at an average temperature rise rate of 5 ° C./minute, and kept at that temperature for 60 minutes for firing. After firing, the product was allowed to cool to room temperature, and then the aluminum plate was taken out from the electric furnace, and a test material No. 1 in which a SiO ₂ film was formed on the surface of the aluminum plate. 1-3 were obtained. Moreover, the surface roughness of each obtained test material was investigated by the said method.

Test material No. 4-8
Test material No. In the same manner as in 1 to 3, inorganic polysilazane is applied on an aluminum plate ground with a PVA grindstone to remove the deteriorated layer so that the thickness of the SiO ₂ film after firing is 2.1 μm, and the solvent is removed. Inserted into the electric furnace. The temperature is increased at an average temperature increase rate of 5 ° C./min, and water vapor is introduced into the electric furnace from the time when a predetermined aluminum plate temperature within the range of 150 ° C. to 200 ° C. (“water vapor introduction temperature” described in Table 1) is reached. While supplying (water vapor partial pressure of 50%), the temperature was further raised to a predetermined final firing temperature ("final firing temperature" described in Table 1), and kept at this temperature for 60 minutes for firing. After firing, the sample was allowed to cool to room temperature in an electric furnace, and then the aluminum plate was taken out, and the test material No. 1 in which the SiO ₂ film was formed on the surface of the aluminum plate was obtained. 4-8 were obtained.

Test material No. 9-11
Apply inorganic polysilazane onto a 2-inch silicon wafer in the same manner as the above test material so that the film thickness of the SiO ₂ film after firing is 2.1 μm, and after drying to remove the solvent, insert it into the electric furnace. did. The temperature was raised to the final firing temperature shown in Table 1 at an average rate of temperature increase of 5 ° C./minute, and the temperature was held for 60 minutes for firing. After firing, the sample was allowed to cool to room temperature in an electric furnace, and then the silicon wafer was taken out and a test material No. 1 in which a SiO ₂ film was formed on the surface of the silicon wafer. 9 to 11 (reference examples) were obtained.

(Surface properties of SiO ₂ film)
The surface properties of the obtained test materials (SiO ₂ film-coated surfaces) were examined. Whether the SiO ₂ film of each test material was cracked or peeled off from the substrate was confirmed visually and with an optical microscope, and evaluated according to the following criteria and the results are shown in Table 1 (“SiO ₂ film state”). In the present invention, “A” was evaluated as acceptable (good).
A: Cracks and peeling are not observed visually and with an optical microscope.
B: Cracks or peeling is observed visually and by optical microscope observation.
Note: No cracks or delamination was observed, but substrate deformation was observed.

As a result of examining the surface properties of the SiO ₂ film of each of the prepared test materials, the test material No. baked at 300 ° C. In No. 3, since cracks were observed in the SiO ₂ film, the film hardness and heat resistance were not confirmed (denoted as “-” in the table).

Test No. baked at 400 ° C. In No. 8, cracks and peeling of the SiO ₂ film were not observed, but since the aluminum plate was deformed, film hardness and heat resistance described later were not confirmed (denoted as “-” in the table).

(Thickness of SiO ₂ film)
The thickness of the SiO ₂ film of each test material was measured using a nanospec / AFT model 5100 manufactured by nanometrics, and the results are shown in Table 1.

(Hardness of SiO ₂ film)
The hardness of the SiO ₂ film of each test material was measured by the nanoindentation method. Specifically, it measured using the nano indenter (Nano Indenter XP / DCM made from Agilent Technology). The measurement was performed at an excitation frequency: 45 Hz, an excitation vibration amplitude: 2 nm, a strain rate: 0.05 / second, and an indentation depth: 2000 nm.

(Heat-resistant)
In order to examine the heat resistance (heat resistance evaluation temperature) of each test material, each test material was inserted into a furnace (air atmosphere) heated to a predetermined set temperature and held for 15 minutes. A correlation between the set temperature of the firing furnace and the substrate temperature was examined in advance using an aluminum plate (dummy) attached with a thermocouple, and it was confirmed that the temperature of the aluminum plate increased to the set temperature if held for 15 minutes.

The test material was inserted into a firing furnace (air atmosphere) heated to a predetermined temperature and held for 15 minutes, and then the test material was taken out of the furnace and allowed to cool to room temperature (25 ° C.). After allowing to cool, the surface properties of the test material were observed at room temperature. Specifically, SiO ₂ film cracks by visual observation under fluorescent lamp illumination and an optical microscope (magnification: 50 × and 200 ×, arbitrary 5 locations on the inner periphery, center, and outer periphery of the substrate per side) And the presence or absence of peeling between the aluminum substrate and the SiO ₂ film were examined.

For the test material in which no crack or peeling of the SiO ₂ film was observed, the set temperature was further raised and the heat resistance test was repeated. In Table 1, “heat resistance evaluation temperature” is the maximum temperature at which cracking or peeling of the SiO ₂ film was observed. In addition, No. As for 4 to 7, even when heated to 500 ° C., cracks and peeling of the SiO ₂ film were not observed, but since deformation of the aluminum plate was observed, the test temperature just before these problems did not occur (450 ° C. ).

No. Nos. 9 to 11 are SiO ₂ films formed on a silicon wafer, and since it is known that the heat resistance is sufficiently high, the heat resistance evaluation temperature was not examined (denoted as “−” in the table).

  From the results in Table 1, the following can be understood.

No. 1 satisfying the film forming conditions of the present invention. 4-7 has a high film hardness (more than 4.0 GPa), also coating state of the SiO ₂ film (SiO ₂ film state: A rating), and heat resistance: was also excellent (heat rating temperature 300 ° C. or higher) .

On the other hand, no. Since No. 8 introduced water vapor in an appropriate temperature range (“water vapor introduction temperature”), the SiO ₂ film was not cracked or peeled off from the aluminum substrate, and the state of the SiO ₂ film itself was good. However, since the final firing temperature was higher than the heat resistance temperature (370 ° C.) of the aluminum plate used, the aluminum plate was deformed.

  The difference between the firing temperature and the heat-resistant temperature is as follows. That is, in the firing process, after the temperature rise is finished and the final temperature is reached, it is held for 60 minutes. Therefore, when the high final temperature is maintained (for example, No. 8: 400 ° C.), the substrate is deformed because the holding time is long. On the other hand, when evaluating the heat resistance, the substrate is put into a furnace whose temperature is set in advance, and is taken out from the furnace when the substrate reaches a predetermined temperature (approximately 15 minutes from the introduction into the furnace to the removal). Therefore, the heat history applied at this time is shorter than the heat history time of the firing process, and it is considered that no significant substrate deformation occurs even at 450 ° C. However, even in the above heat resistance evaluation, deformation occurs when the heat resistance evaluation temperature reaches 200 ° C.

  No. Nos. 1 and 2 are examples in which water vapor was not introduced during the firing process, and both had low film hardness (less than 4.0 GPa) and insufficient heat resistance (heat resistance evaluation temperature: less than 300 ° C.).

No. No. 3 is an example of heating and baking up to a final baking temperature of 300 ° C. without introducing water vapor, but cracks occurred in the SiO ₂ film.

As a reference example, No. 1 in which a SiO ₂ film was formed on a silicon wafer. In Nos. 9 to 11, cracks and peeling did not occur even when fired in the range of 200 ° C. to 400 ° C. (“SiO ₂ film state” was evaluated as A), but the film hardness was less than 4.0 GPa (3. 1 to 3.4 GPa).

Experiment 2
In Experiment 2, the above test material No. For 4-7 it was investigated the effect on the surface roughness of the SiO ₂ film formed on the surface of the aluminum alloy plate in the case of applying the inorganic polysilazane (center line average roughness Ra).

The above test material No. In the production of 4 to 7, the surface roughness of the aluminum plate to be used was measured before forming the SiO ₂ film. First, the centerline average roughness Ra as the surface roughness of the aluminum substrate was measured with an atomic force microscope (AFM). As the AFM, “Nanosurf easyScan2 FlexAFM” manufactured by Nano Science Instrument was used (AFM1: viewing angle 10 μm square, AFM2: viewing field 2 μm square). The surface roughness was also measured in the same manner by the stylus method (Taylor / Hobson's intra).

Next, the center line average roughness Ra of the SiO ₂ film formed on the aluminum substrate was measured in the same manner. The results are shown in Table 2.

As shown in Table 2, even if the surface roughness of the aluminum plate before film formation is high for any of the test materials, a leveling effect can be obtained by applying inorganic polysilazane, so that a sufficiently smooth surface can be obtained. It was confirmed. Therefore, according to the present invention, a smooth surface can be obtained without performing finish polishing or the like, and the surface smoothness of the SiO ₂ film can be greatly improved.

Claims (5)

It is an aluminum plate on which a SiO ₂ film is formed, and when the temperature of the aluminum plate coated with the inorganic polysilazane-containing liquid is 100 to 250 ° C., the addition of water vapor is started and fired. A featured SiO ₂ film-coated aluminum plate. _2. The SiO ₂ film-coated aluminum substrate according to claim 1, wherein a final temperature during the baking is 370 ° C. or lower. In the method for producing an aluminum plate in which an inorganic polysilazane-containing liquid is applied to the surface of the aluminum plate, and then the aluminum substrate is continuously heated and fired to form a SiO ₂ film.
The method for producing a SiO ₂ film-coated aluminum plate is characterized in that the baking starts addition of water vapor when the temperature of the aluminum plate is 100 to 250 ° C. The method for producing a SiO ₂ film-coated aluminum plate according to claim 3, wherein a final temperature during the baking is 370 ° C or lower. The method for producing a SiO ₂ film-coated aluminum plate according to claim 3 or 4, wherein the rolled surface of the aluminum plate surface is removed and then the inorganic polysilazane-containing liquid is applied.