JP2698005B2 - Surface modification method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved treatment method for modifying the surface condition of a material by plasma treatment, that is, properties such as high abrasion resistance, durability, and stain resistance.

[0002]

2. Description of the Related Art Conventionally, the following are generally used as organosilicon-based thin films. A thin film obtained by hydrolysis and polycondensation of an organic silicon monomer. Plasma polymerized thin film obtained by using organic silicon as a monomer. The silicon which is a main component of the organic silicon-based thin film includes a silicon compound represented by the following general formula: R ¹ _n SiX _4-n (n = 0 to 3)... And / or a partial hydrolysis product thereof as a main component.
Here, R ¹ represents the same or different substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and X represents a hydrolyzable group. n is represented by 0, 1, 2 or 3. Particularly, those having n = 0, 1, and 2 are excellent in characteristics such as stability of film quality and leveling property, and are preferably used. As X,
Examples thereof include an alkoxy group, an acetoxy group, an oxime group, an enoxy group, an amino group, an aminoxy group, an amide group, and a hydroxyl group. Of these, an alkoxy group is preferable in terms of availability and ease of preparation. In this case, the organic functional group forming the alkoxy group is not particularly limited, but for example, those containing an alkyl group having 1 to 4 carbon atoms and / or a phenyl group, an amino group, an acryl group, and the like are preferably used. Can be

As the organosilane represented by the formula (1), specifically, methyltrimethoxysilane, phenyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, methyltriethoxysilane, phenyltriethoxysilane, Examples include dimethyldimethoxysilane, diphenyldimethoxysilane, dimethyldiethoxysilane, tetramethoxysilane, tetraethoxysilane, aminopropyltriethoxysilane, methacryloxypropyltrimethoxysilane, and trimethylmethoxysilane.

A silicon alkoxide-based coating material as the organic silicon-based thin film is obtained, for example, as follows. The silicon compound component having the above-mentioned composition alone or in a mixture is diluted with a suitable solvent, and water and a catalyst are added in required amounts as a curing agent, and hydrolysis and polycondensation are carried out. As a result, the silicon compound component forms a siloxane bond to be polymerized, and at the same time, is cured to obtain a silicon alkoxide-based coating material. At that time, an appropriate amount of colloidal silica can be added. Colloidal silica is obtained by dispersing a particulate silica component in an organic solvent such as water or methanol, and the particle size and the type of the solvent are not particularly limited. Water is used as the curing agent, and the amount of addition is 45% by weight or less, more preferably 25% by weight or less based on the coating agent. As the diluting solvent, methanol, ethanol,
Alcohols such as isopropanol, ethyl cellosolve,
Butyl cellosolve, ethylene glycol, ethylene glycol monomethyl ether and the like are used. These diluting solvents may be used alone or in combination.

[0005] Next, it is desirable that the silicon alkoxide-based coating material is used after being adjusted to a pH in the range of 3.8 to 6.0. When the pH is out of the above range, the stability of the coating material is poor, so that the usable period after preparing the coating material is shortened. The method for adjusting the pH is not particularly limited. For example, when the pH falls to 3.8 or less after the preparation of the coating solution, the pH is adjusted to 6.
When it becomes 0 or more, it may be adjusted so as to lower the pH by using an acidic reagent such as hydrochloric acid. The coating material thus prepared is coated on a substrate and dried. Desirable drying conditions are temperatures of 200 ° C. or less.

The organic silicon-based thin film is a plasma polymerized film obtained by polymerizing a polymerizable silicon compound monomer alone or in a mixture in a plasma. Generally, tetraethoxysilane, tetramethoxysilane, triethoxysilane,
Hexamethyldisiloxane, vinyltrimethoxysilane, vinyltriethoxysilane, hexamethyldisilazane, fluoroalkylsilane and the like are used. A plasma generation method of plasma polymerization may be a conventionally known method using reduced pressure plasma, or a method described in Japanese Patent Publication No.
262 and atmospheric pressure plasma as described in JP-A-2-15171.

[0007] The organic silicon-based thin film thus prepared is
Unless the heat treatment is performed up to about 1000 ° C., it does not become completely inorganic. In addition, since the internal volatile components are scattered in the course of such a heat treatment, cracks are formed or the material becomes porous. Therefore, practically, a silicon-based thin film containing an organic substance in its structure is used. For example, PLEIN PKunstst Ger Plas by MENGES G.
t) Vol. 78, No. 10, pp. 1015 to 1018, a plasma polymerized film using hexamethyldisiloxane as a raw material has a chemical structure represented by the right side of the following formula 1. It has been shown.

[0008]

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As described above, since the organic silicon-based thin film has a main skeleton of silicon and has both organic and inorganic properties as compared with a normal organic polymer thin film having a main skeleton of carbon, the hardness, Excellent heat resistance and durability. In addition, many organic components and functional groups such as hydroxyl groups remain in the organic silicon-based thin film, so that the organic silicon-based thin film exhibits high adhesion to a base material regardless of its type. For example,
As a substrate, in addition to inorganic materials such as glass and ceramics and metal materials, organic materials such as plastics can be coated with good adhesion. For this reason, organic silicon-based thin films have been applied in a wide range of fields as, for example, high insulation / high moisture resistance thin films of electronic materials, high wear resistance thin films of plastic members, and high weather resistance coating materials of building materials.

However, it is undeniable that an organic silicon-based thin film is inferior to the above-mentioned various properties as compared with a completely inorganic silicon-based thin film. For example, the surface hardness is lower than that of an inorganic silicon-based thin film. In addition, there is a disadvantage that the surface is easily deteriorated by reacting with other compounds. For example, when used as a surface protective film, the organic functional groups remaining in the organosilicon-based thin film react with contaminants (for example, hair dyes and the like) to contaminate the surface.

Therefore, many attempts have been made to bring the characteristics of the organosilicon-based thin film closer to the inorganic level while maintaining the above-mentioned excellent characteristics. As one of them, there is a method of modifying the surface by utilizing the high reactivity of plasma.
For example, a method has been developed in which the surface of an organosilicon-based thin film is subjected to plasma treatment to harden the surface layer to improve wear resistance (US Pat. No. 4,435,476).
Reference).

[0012]

However, glow discharge useful as a plasma process is generally a process under a high vacuum of 10 ^-2 Torr or less, and the above-mentioned method is also performed under a high vacuum. This is because a high vacuum was conventionally required to perform stable glow discharge.

However, under a high vacuum, it is difficult to treat a material containing a volatile component. For example, as in the case of the above-mentioned organosilicon-based thin film, a solvent such as water or alcohol used for forming the film may remain inside the film. In such a case, even in a small amount, these solvents volatilize under a high vacuum. The film quality is degraded. In addition, when the base material is an organic material or a hydrated material (for example,
Building materials inevitably contain water. In the case of (1), under high vacuum, the quality of the film is deteriorated or the film is peeled off due to the generation of volatile components from the substrate.

For example, the above-mentioned organosilicon-based thin film has a high vapor pressure, such as uncured organosilicon monomer or partially reacted dimer, trimer, moisture, solvent, etc., in addition to the organic component and hydroxyl group present in the siloxane bond. Constituents remain in significant amounts. Also, many organic functional groups described above remain in the organic silicon thin film. However, in the conventional processing using reduced-pressure plasma, these components are scattered in the process of reducing the pressure, which causes a problem that the thin film becomes porous or the adhesion decreases. Therefore, when such a treatment is performed under reduced pressure, it is necessary to make the coating film very thin, in which case the effect of the coating is very small. In addition, pinholes increase in the film, and the corrosion resistance deteriorates. Further, it is difficult to obtain a film thickness of 3 microns or more, and the application field is limited.

In addition, plasma processing under a high vacuum requires a device and equipment for obtaining a high vacuum, so that there is a problem that costs are high and processing of a large-area material is difficult. . Therefore, the present invention enables a plasma treatment over a large area of an organosilicon-based thin film formed on the surface of a substrate without requiring a vacuum facility or the like, thereby enabling volatile components to be contained in the substrate or the thin film. It is an object of the present invention to provide a method capable of improving various characteristics of a thin film even when the thin film contains.

[0016]

Means for Solving the Problems In order to solve the above problems, the inventors have made various studies. As a result, the followings were confirmed by experiments, and the present invention was completed. That is, the present inventors have previously developed a method capable of uniformly treating the surface of various materials over a large area by a glow discharge plasma under atmospheric pressure of high stability (Japanese Patent Publication No. 2-4).
8626, JP-A-2-15171, etc.). The inventors have predicted that if this method can be applied to an organic silicon-based thin film, plasma processing can be performed at normal pressure, so that the disadvantage of the conventional method can be solved. . Therefore, when the plasma treatment under the atmospheric pressure was performed on the organic silicon-based thin film, it was found that various characteristics of the organic silicon-based thin film were improved.

Therefore, the surface modification method according to the present invention relates to a silicon-based thin film formed on the surface of a substrate and containing an organic substance in its structure (hereinafter referred to simply as “organic silicon-based thin film” in this specification). ) Is performed in plasma excited by glow discharge at or near atmospheric pressure. Examples of the substrate used in the present invention include various materials such as inorganic materials such as glass and ceramics, organic materials such as metal materials and plastics, and organic-inorganic composite materials such as building materials. There is no particular limitation. Also, the shape of the base material is not particularly limited, and various shapes such as a plate shape, a ribbon shape, and a fine wire shape can be used.

In the present invention, the type of gas used when plasma-treating the organosilicon-based thin film is selected according to the content of the desired surface treatment, and is not particularly limited. For example, He, Ne, Ar Inert gas such as O
_And reactive gases such as N ₂ , NH ₃ , CF ₄ , H ₂ O, and N ₂ O. These gases may be used alone or in combination of two or more. When a plurality of types of gases are used in combination, the mixing ratio of these gases is not particularly limited. In order to minimize the sputtering of the thin film and perform the glow discharge more stably, the inert gas is preferably He gas having a small mass.
It is preferable to use

In the present invention, the pressure at which the glow discharge plasma is generated must be at or near atmospheric pressure (normal pressure: 760 mmHg). A specific range of the pressure is 500 to 1500 mmHg. Within this range, plasma is stably generated, and a film having stable film quality can be obtained without deterioration of film performance due to generation of gas in the film or the base material.

Glow discharge conditions for generating plasma, for example, applied power and its frequency, processing time, and the like are appropriately set according to a desired processing degree, and are not particularly limited.

[0021]

When an organic silicon-based thin film formed on the surface of a substrate is treated in plasma excited by glow discharge at or near atmospheric pressure, the treatment is performed at a pressure near atmospheric pressure. This eliminates the need for vacuum equipment and the like, enables uniform plasma processing over a large area, and enables various types of organosilicon-based thin films without deteriorating the film quality due to volatilization of components contained in the base material and the thin film. The characteristics can be improved.

The mechanism by which various characteristics are improved by plasma-treating an organic silicon-based thin film is considered as follows. When the surface of the organosilicon-based thin film is subjected to the action of plasma, the remaining organic functional groups are eliminated in the layer near the surface, and the polymer becomes apparently almost completely inorganic, with advanced polymerization of the organosilicon. Therefore, a dense layer with high density is obtained in this portion. When a reactive gas is used, in addition to such an effect, the functional group on the surface is replaced with an element such as O, N, or F, so that the characteristics are significantly improved. For example, when treated with O ₂ plasma, the hardness of the surface and the stain resistance to a hair dye and the like are greatly improved. N ₂ and N
When treated with H ₃ plasma, the surface is nitrided and O 3
₍₂₎ Surface hardness is improved more than in the case of treatment with plasma, and a surface with excellent water resistance is obtained. Also, CF ₄
When a fluorine-based gas such as that described above is used, a fluorinated layer is formed on the surface, and the contamination resistance is improved in addition to the above-described effects of plasma.

[0023]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an apparatus used in carrying out the surface modification method according to the present invention.
In the reaction tank 5, upper and lower parallel plate type electrodes 1 and 2 are provided, and on the lower electrode 2, a solid dielectric 3 is placed. First, the base material 4a is provided in the gap between the upper and lower electrodes 1 and 2.
A sample 4 on which an organic silicon-based thin film 4b is formed is placed. The solid dielectric 3 may be provided below the upper electrode 1 in place of the lower electrode 2 or may be provided on both of the upper and lower electrodes 1 and 2. When the base material 4a is a metal, the solid dielectric 3
It is preferable to install both the upper and lower electrodes 1 and 2. Next, when a high-voltage AC electric field is applied to the upper electrode 1 while flowing the gas and maintaining the pressure in the reaction tank 5 at or near atmospheric pressure, plasma is generated between the upper and lower electrodes 1 and 2. The surface of the organic silicon thin film 4b of the sample 4 is modified by the action of the plasma. In the figure, reference numeral 7 denotes a high-frequency power supply for obtaining the high-voltage AC electric field. Reaction tank 5
The insulator 6 is provided in the high voltage introduction part and the installation derivation part. The frequency of the AC electric field to be applied is as described above. However, since the sample 4 is heated in a high frequency region, in this case, a cooling method or processing time that does not adversely affect the heating is used. May need to be shortened.

Hereinafter, the processing conditions and the obtained characteristics will be described in detail with reference to more specific examples, but the present invention is not limited to the following examples and the examples already described. In each of Examples, Comparative Examples and Reference Examples,
The following characteristic tests were performed. Pencil hardness test According to JIS-K5400.

Abrasion resistance test The surface is worn by steel wool. ×: easily worn. ：: Does not wear easily. Stain resistance test A commercially available hair dye was applied to the substrate and
After the time, the dyeability was visually evaluated.

×: The dyed surface is colored. ：: The dyed surface is not colored. Specific resistance of thin film Specific resistance measurement by 4-probe method. Moisture resistance test MIL-STD202E-106D
Test according to. 10 cycles.

×: Changes in appearance and poor adhesion occur. ：: No change in appearance or poor adhesion. -Example 1-A hydrolyzed composition of trimethylalkoxysilane represented by the following formula 2 using hydrochloric acid as a catalyst and isopropanol as a solvent is applied to a glass substrate, and heated and cured at 200 ° C for 1 hour to form a film. An organic silicon-based thin film having a thickness of 5 μm was formed. The pH of the hydrolysis composition was 4.8.

[0028]

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Next, a glass substrate having an organic silicon-based thin film formed on its surface was used as a sample, and this was placed between the upper and lower electrodes in FIG. 1, and the atmospheric pressure plasma treatment of the organic silicon-based thin film was performed under the following conditions. . Conditions (1) Gas used and its flow rate Helium (He) 2000 sccm Oxygen (O ₂ ) 50 sccm Here, “sccm” represents the flow rate (ml) per unit time (minute) at 25 ° C. and 1 atm. (2) Plasma conditions Frequency 15 KHz Power 50 W Processing time 60 minutes Processing pressure 1 atm (760 mmHg) A characteristic test was performed on the thin film after the plasma processing. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 3 shows the results.

Examples 2 to 14 In Example 1, the material of the substrate, the raw material of the organic silicon thin film,
In the same manner as in Example 1 except that the film formation method and film thickness, the type of gas used for plasma-treating the thin film, its flow rate and plasma-treatment pressure were as shown in Tables 1 and 2 below. After forming an organosilicon-based thin film on the substrate surface, this was subjected to plasma treatment. However, in Example 11, the curing temperature at the time of forming the thin film was changed to 100 ° C. Further, a characteristic test was performed on the thin film after the plasma treatment. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 3 shows the results.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

As shown in Table 3, it was confirmed that various properties were improved by subjecting the organosilicon-based thin film to plasma treatment at or near atmospheric pressure. Comparative Example 1 An organosilicon-based thin film was formed on a substrate surface in the same manner as in Example 1 except that the plasma processing pressure was changed to 1800 mmHg, and then plasma-processed. A characteristic test was performed on the thin film after the plasma treatment. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 5 shows the results. In a pressure region higher than 1500 mmHg, generation of plasma becomes unstable, and as a result, the effect of the plasma is small, and no improvement in film quality is observed.

Comparative Examples 2 to 5 Comparative Examples 2, 3, 4, and 5 correspond to Examples 1, 2, and 1, respectively.
An organic silicon-based thin film was formed on the substrate in the same manner as in Nos. 1 and 13. In Comparative Example 4, 100 ° C. as in Example 11.
Heat curing was performed in -1 hour. Next, the sample was subjected to a plasma processing apparatus (PD10 manufactured by Samco International Co., Ltd.).
) And vacuum degassed to 0.005 Torr. Next, a predetermined gas was introduced, and a low-pressure plasma treatment was performed under the conditions shown in Table 4. The plasma frequency was 13.56 MHz. A characteristic test was performed on the thin film after the low-pressure plasma treatment. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 5 shows the results. In this case, the pencil hardness is improved, and when the substrate is other than polycarbonate, the abrasion resistance and the specific resistance are improved. However, the adhesion to the substrate is poor, and no improvement in performance in the moisture resistance test and the stain resistance test is observed.

[0036]

[Table 4]

[0037]

[Table 5]

[0038] - As an example 15～17- silicon alkoxide coating material, 100 parts by weight of methyltrimethoxysilane was mixed with 100 parts by weight of isopropanol, hydrochloric acid trace as a catalyst, the H ₂ O 90
Parts by weight were added and stirred. pH was 4.5. The solutions thus prepared were applied to the substrates shown in Table 6, respectively. The coating amount was set so that the film thickness after curing was 5 μm. After the application, the coating was cured at 200 ° C. for 1 hour. Next, an atmospheric pressure plasma treatment was performed in the same manner as in Example 1. A characteristic test was performed on the thin film after the plasma treatment. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 8 shows the results.

Examples 18 to 20 The same silicon alkoxide coating as in Example 15 was applied to glass, polycarbonate, and stainless steel substrates, respectively, and subjected to an atmospheric pressure plasma treatment. The processing conditions are as follows. For condition (1) using gas and its flow rate of helium (the He) 1000 sccm of oxygen (O ₂₎ 10 sccm (2) thin film of plasma conditions Frequency 13.56MHz power 50W treatment time 20 min treatment pressure 1 atm (760 mmHg) after the plasma treatment, characteristics The test was performed. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 8 shows the results.

The films made of methyltrimethoxysilane of Examples 15 to 20 were prepared in Examples 1, 3, 5, 7, 8, 9, and 1.
Characteristics such as stability of film quality and leveling property were superior to those of films made of trimethylalkoxysilanes 1 and 13. -Comparative Examples 6 to 8- The same silicon alkoxide coating as in Example 15 was applied to glass, polycarbonate, and stainless steel substrates, respectively, and subjected to low-pressure plasma treatment. The processing conditions were Comparative Example 2.
Is the same as A characteristic test was performed on the thin film after the plasma treatment. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 8 shows the results.
In this case, the pencil hardness is improved, and when the substrate is other than polycarbonate, the abrasion resistance and the specific resistance are improved. However, the adhesion to the substrate is poor, and no improvement in performance in the moisture resistance test and the stain resistance test is observed.

Comparative Example 9 The same silicon alkoxide coating as in Example 15 was applied to a glass substrate so that the film thickness after curing was 1 μm.
Low pressure plasma treatment was performed. The processing conditions were the same as in Comparative Example 2. A characteristic test was performed on the thin film after the plasma treatment. For reference, a characteristic test was also performed on the thin film before the plasma treatment. Table 8 shows the results. In this case, although the pencil hardness, stain resistance and specific resistance are improved, no improvement in performance in the moisture resistance test and the abrasion resistance test is observed because the film thickness is thin.

[0042]

[Table 6]

[0043]

[Table 7]

[0044]

[Table 8]

[0045]

According to the surface modification method of the present invention, a large-area plasma treatment can be performed on an organosilicon-based thin film formed on the surface of a substrate without requiring vacuum equipment or the like, Thereby, various characteristics of the thin film can be improved even if a volatile component is contained in the base material or the thin film.

Since the organic silicon-based thin film treated by this method has both organic and inorganic structures at the interface with the substrate, it adheres to the substrate made of various materials regardless of whether it is organic or inorganic. Excellent in nature. Since the organic silicon-based thin film has a substantially complete inorganic structure near the surface, the organic silicon-based thin film is a functionally graded thin film having much more excellent characteristics than ordinary organic substances. Moreover, since the organic silicon-based thin film has excellent properties as a dielectric, the method of the present invention is also an excellent method for synthesizing a dielectric thin film with various materials.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of an apparatus used for performing a surface modification method according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Upper electrode 2 Lower electrode 4a Substrate 4b Organosilicon-based thin film 5 Reaction tank

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical indication location C08J 7/04 CFH C08J 7/04 CFHM (72) Inventor Masuhiro 843- Shimoshinkura, Wako-shi, Saitama Fifteen

Claims (4)

(57) [Claims] A silicon-based thin film formed on the surface of a base material and containing an organic substance in its structure, in a range of 500 to 1500 mmHg.
A surface modification method in which a surface is treated in plasma excited by glow discharge under an internal pressure. 2. The silicon-based thin film has a general formula: R ¹ _n Si
_4-n (wherein, R ¹ is the same or different and represents a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, X represents a hydrolyzable group, and hydrogen. N = 0 to 3) alone or in mixtures and / or method for modifying a partial hydrolysis product is made of a cured product of a coating material consisting mainly claim 1 Symbol mounting surface represented by silicon compound). 3. A silicon light thin film, alone or a mixture of polymerizable silicon compound monomer, reforming method of claim 1 Symbol mounting surface is a plasma-polymerized film was polymerized in the plasma. 4. A film thickness of the silicon-based thin film, method for modifying the surface according to claim 1 is 3 microns or more to 3.