JPH0673208A - Method for surface modification - Google Patents

Abstract

PURPOSE:To provide a surface modification method whereby a thin organosilicon film formed on the surface of a base can be subjected to a large-area plasma treatment without using any vacuum equipment or the like and whereby the properties of the thin film can be improved even when a volatile component is contained in the base or the thin film. CONSTITUTION:This method comprises treating an organosilicon thin film 4b formed on the surface of a base 41 with a plasma excited by glow discharge between the upper and lower electrodes 1 and 2 under atmospheric pressure or near.

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, characteristics such as high abrasion resistance, durability and stain resistance.

[0002]

2. Description of the Related Art Conventionally, the followings are generally used as organic silicon thin films. A thin film obtained by hydrolysis / polycondensation of an organosilicon monomer. A plasma polymerized thin film obtained using organosilicon as a monomer. As silicon which is a main component of the above-mentioned organic silicon thin film, a silicon compound represented by the general formula; R ¹ _n SiX _4-n (n = 0 to 3) (1) or a mixture thereof and / Or its main component is a partial hydrolysis product.
Here, R ¹ is the same or different and is a substituted or unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and X is a hydrolyzable group. n is represented by 0, 1, 2 or 3. In particular, those having n = 0, 1, 2 are excellent in properties 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 amido group, and a hydroxyl group, but the alkoxy group is preferable from the viewpoint of easy availability and easy preparation. In that case, the organic functional group forming the alkoxy group is not particularly limited, but for example, an organic functional group containing an alkyl group having 1 to 4 carbon atoms and / or a phenyl group, an amino group, an acryl group or the like is preferably used. To be

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

A silicon alkoxide coating material as the organic silicon thin film is obtained, for example, as follows. A single or a mixture of the silicon compound components having the above composition is diluted with a suitable solvent, and water as a curing agent and a necessary amount of a catalyst are added thereto to carry out hydrolysis and polycondensation reactions. As a result, the silicon compound component forms a siloxane bond to be polymerized and simultaneously cured to obtain a silicon alkoxide coating material. At that time, an appropriate amount of colloidal silica can be added. Colloidal silica is a fine particle silica component dispersed in an organic solvent such as water or methanol, and the particle size and the type of solvent are not particularly limited. Water is used as the curing agent, and the addition amount thereof is 45% by weight or less, more preferably 25% by weight or less based on the coating agent. Dilution solvents include methanol, ethanol,
Alcohol 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 of two or more.

Next, it is desirable that the silicon alkoxide-based coating material is prepared and used in a pH range of 3.8 to 6.0. When the pH is out of the above range, the stability of the coating material is poor, and the usable period after the coating material is prepared becomes short. The method for adjusting the pH is not particularly limited, but for example, if the pH becomes 3.8 or less after the preparation of the coating solution, the pH is adjusted to 6. by using a basic reagent such as ammonia.
When it becomes 0 or more, the pH may be adjusted by using an acidic reagent such as hydrochloric acid. The coating material thus prepared is coated on a substrate and dried. The drying condition is preferably 200 ° C. or lower.

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

The organosilicon thin film thus prepared is
Unless it is heated up to around 1000 ° C., it will not become a completely inorganic substance. In addition, since volatile components inside scatter during the heat treatment, cracks may occur or the material may become porous. Therefore, practically, a silicon-based thin film containing an organic substance in its structure is used. For example, MENGES G., PLEIN PKunstst Ger Plas
t) In 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 chemical formula 1. Is shown.

[0008]

[Chemical 1]

As described above, the organic silicon-based thin film has silicon as a main skeleton and has both organic and inorganic characteristics, as compared with an ordinary organic polymer thin film having carbon as a main skeleton. It has excellent heat resistance and durability. In addition, a large number of organic components and functional groups such as hydroxyl groups remain in the organosilicon thin film, and therefore, high adhesion is exhibited to the base material regardless of its type. For example,
As the base material, in addition to inorganic materials such as glass and ceramics and metallic materials, organic materials such as plastics can be coated with good adhesion. Therefore, the organic silicon thin film has been applied in a wide range of fields such as a highly insulating and highly moisture resistant thin film for electronic materials, a highly abrasion resistant thin film for plastic members, and a highly weather resistant coating material for building materials.

However, it cannot be denied that the organic silicon type thin film is inferior to the above-mentioned various characteristics as compared with a perfect inorganic silicon type thin film. For example, the surface hardness is lower than that of the inorganic silicon thin film. In addition, there is a drawback that the surface is likely to be deteriorated by reacting with other compounds. For example, when it is used as a surface protective film, the organic functional groups remaining in the organosilicon thin film react with contaminants (for example, hair dye) and contaminate the surface.

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

[0012]

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

However, it is difficult to process a material containing a volatile component under a high vacuum. For example, like the above-mentioned organic silicon thin film, the solvent used for forming the film, such as water and alcohol, may remain inside the film, and in such a case, even in a small amount, these may be volatilized under high vacuum. Film quality is reduced. In addition, the base material is an organic material or a water-containing material (for example,
Building materials inevitably contain water. In the case of 1), under high vacuum, volatile components are generated from the base material, so that the film quality is deteriorated or the film is peeled off.

For example, the above-mentioned organosilicon thin film has a high vapor pressure of uncured organosilicon monomer, partially reacted dimer, trimer, water, solvent, etc., in addition to the organic components and hydroxyl groups present in the siloxane bond. The components it contains remain in significant amounts. In addition, many organic functional groups described above also remain in the organic silicon thin film. However, in the conventional treatment using the low pressure plasma, since these components are scattered in the pressure reduction process, there arises a problem that the thin film becomes porous or the adhesion is lowered. Therefore, when performing such a treatment under reduced pressure, it is necessary to make the coating film thickness very thin, and in that case, the effect of the coating is also very small. In addition, the number of pinholes in the film increases, resulting in poor corrosion resistance. Further, it is difficult to obtain a film thickness of 3 microns or more, and the application field is limited.

Further, the plasma processing under high vacuum requires a device and equipment for obtaining a high vacuum, which is costly and it is difficult to process a large-area material. . Therefore, the present invention enables plasma treatment over a large area on an organic silicon-based thin film formed on the surface of a base material without the need for vacuum equipment or the like. It is an object of the present invention to provide a method capable of improving various characteristics of a thin film even if it contains.

[0016]

In order to solve the above problems, the inventors have made various studies. As a result, the present invention has been completed by confirming the following by experiments. That is, the inventors have previously developed a method capable of uniformly treating the surface of various materials over a large area with a highly stable glow discharge plasma under atmospheric pressure (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 thin film, the plasma treatment can be performed at normal pressure, and the drawbacks of the conventional method can be solved. . Therefore, it was found that when the plasma treatment under the atmospheric pressure was performed on the organic silicon thin film, various characteristics of the organic silicon thin film were improved.

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

In the present invention, the type of gas used when plasma-treating the organosilicon thin film is selected according to the desired surface treatment content and is not particularly limited, but for example, He, Ne, Ar. Inert gas such as O
Reactive gases such as ₂ , N ₂ , NH ₃ , CF ₄ , H ₂ O, and N ₂ O may be used. These gases may be used alone or in combination of two or more. When a plurality of kinds of gases are used together, the mixing ratio of these gases is not particularly limited. In addition, in order to minimize the sputtering on the thin film and to perform the glow discharge more stably, the inert gas is He, which has a light mass.
Is preferably used.

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

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

[0021]

[Function] When the organic silicon thin film formed on the surface of the base material is processed in plasma excited by glow discharge under or near atmospheric pressure, the processing is performed under pressure near atmospheric pressure. Therefore, the need for vacuum equipment is eliminated, and homogeneous plasma treatment over a large area becomes possible, and various properties of the organosilicon thin film can be achieved without degrading the film quality due to the volatilization of the components contained in the base material or thin film. It is possible to improve the characteristics.

The mechanism by which various characteristics are improved by plasma-treating an organosilicon thin film is considered as follows. When the surface of the organic silicon-based thin film is subjected to the action of plasma, the remaining organic functional groups are eliminated in the surface-near surface layer, and apparently the organic silicon is polymerized to become a substantially complete inorganic substance. Therefore, a dense layer having a high density can be obtained in this portion. When a reactive gas is used, the functional groups on the surface are replaced with elements such as O, N, and F, in addition to such an action, 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 the hair dye and the like are greatly improved. N ₂ or N
When treated with H ₃ plasma, the surface is nitrided and O
₂ Surface hardness is improved more than when treated with plasma, and a surface with excellent water resistance is obtained. Also, CF ₄
When a fluorine-based gas such as the above is used, a fluorinated layer is formed on the surface, and the contamination resistance is improved in addition to the above-mentioned effect of plasma.

[0023]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an example of an apparatus used for carrying out the surface modification method according to the present invention.
Upper and lower parallel plate electrodes 1 and 2 are installed in the reaction tank 5, and a solid dielectric 3 is placed on the lower electrode 2. First, in the gap between the upper and lower electrodes 1 and 2, the base material 4a
A sample 4 having an organic silicon thin film 4b formed on its surface is placed. The solid dielectric 3 may be provided below the upper electrode 1 instead of the lower electrode 2, or may be provided on both the upper and lower electrodes 1, 2; When the base material 4a is a metal, the solid dielectric 3 is
It is preferable to install them on both the upper and lower electrodes 1, 2. Next, when a high-voltage AC electric field is applied to the upper electrode 1 while flowing 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, 2. The surface of the organic silicon thin film 4b of the sample 4 is modified by the action of this plasma. In the figure, 7 indicates a high frequency power source for obtaining the high voltage AC electric field. Reaction tank 5
An insulator 6 is provided at the high voltage introduction part and the installation lead part. The frequency of the AC electric field to be applied is as described above, but since the sample 4 is heated in a high frequency region, in this case, a cooling method or a treatment time that does not cause adverse effects due to heating. May need to be shortened.

Hereinafter, the processing conditions and the obtained characteristics will be described in more 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 Example, Comparative Example and Reference Example,
The following characteristic test was conducted. Pencil hardness test According to JIS-K5400.

Abrasion resistance test Abrasion the surface with steel wool. X: It is easily worn. ◯: Does not easily wear. Contamination resistance test Apply a commercially available hair dye to the substrate and
After time, the dyeability is visually evaluated.

X: The dyed surface is colored. ○: The dyed surface is not colored. Resistivity of thin film 4 Resistivity measurement by probe method. Humidity resistance test MIL-STD202E-106D
Exam according to. 10 cycles.

X: Change in appearance and poor adhesion occur. ◯: No change in appearance or poor adhesion. -Example 1- A hydrolyzed composition solution of trimethylalkoxysilane represented by the following formula 2 using hydrochloric acid as a catalyst and isopropanol as a solvent was applied to a glass substrate and heat-cured at 200 ° C for 1 hour to form a film. An organosilicon thin film having a thickness of 5 μ was formed. The pH of the hydrolyzed composition liquid was 4.8.

[0028]

[Chemical 2]

Next, a glass substrate having an organosilicon thin film formed on its surface was used as a sample, which was placed between the upper and lower electrodes of FIG. 1 and subjected to atmospheric pressure plasma treatment of the organosilicon thin film under the following conditions. . Condition (1) Used gas and its flow rate Helium (He) 2000 sccm Oxygen (O ₂ ) 50 sccm Here, “sccm” represents the flow rate (ml) per unit time (min) at 25 ° C. and 1 atm. (2) Plasma conditions Frequency 15 KHz Power 50 W Treatment time 60 minutes Treatment pressure 1 atm (760 mmHg) The thin film after the plasma treatment was subjected to a characteristic test. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 3.

-Examples 2 to 14-In Example 1, the substrate material, the raw material of the organosilicon thin film,
Same as Example 1 except that the film forming method and the film thickness, the kind of gas used in the plasma processing of the thin film, the flow rate and the plasma processing pressure were as shown in Tables 1 and 2 below. After forming an organosilicon thin film on the surface of the substrate, this was plasma treated. However, in Example 11, the curing temperature at the time of thin film formation was changed to 100 ° C. Further, a characteristic test was performed on the thin film after the plasma treatment. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 3.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

As shown in Table 3, it was confirmed that various characteristics of the organic silicon thin film were improved by plasma-treating the organosilicon thin film under atmospheric pressure or a pressure in the vicinity thereof. -Comparative Example 1-An organosilicon thin film was formed on the substrate surface in the same manner as in Example 1 except that the plasma treatment pressure was set to 1800 mmHg, and then plasma treatment was performed. A characteristic test was performed on the thin film after the plasma treatment. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 5. In a pressure range higher than 1500 mmHg, plasma generation becomes unstable, and as a result, the effect of plasma is small and no improvement in film quality is observed.

-Comparative Examples 2-5-Comparative Examples 2, 3, 4, and 5 are Examples 1, 2, and 1, respectively.
An organosilicon 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.
It was heat-cured in -1 hour. Next, a sample is processed by Samco International Co., Ltd. plasma processing device (PD10
It was placed in a mold 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. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 5. In this case, the pencil hardness is improved, and if the base material is other than polycarbonate, abrasion resistance and specific resistance are improved. However, the adhesion to the substrate is poor and no improvement in performance is observed in the humidity resistance test and stain resistance test.

[0036]

[Table 4]

[0037]

[Table 5]

Examples 15 to 17 As a silicon alkoxide coating material, 100 parts by weight of methyltrimethoxysilane and 100 parts by weight of isopropanol were mixed, and a small amount of hydrochloric acid was used as a catalyst to add 90 parts of H ₂ O.
Part by weight was added and stirred. The 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, it was cured at 200 ° C. for 1 hour. Then, 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. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 8.

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 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 conducted. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 8.

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

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 would be 1 μm,
A low pressure plasma treatment was performed. The treatment conditions were the same as in Comparative Example 2. A characteristic test was performed on the thin film after the plasma treatment. As a reference, a characteristic test was performed on the thin film before plasma treatment. The results are shown in Table 8. In this case, although the pencil hardness, stain resistance, and specific resistance are improved, the performance is not improved in the humidity resistance test and the abrasion resistance test 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, it is possible to perform plasma treatment over a large area on an organosilicon thin film formed on a substrate surface without requiring vacuum equipment or the like. As a result, various characteristics of the thin film can be improved even if the substrate or the thin film contains a volatile component.

Since the organic silicon 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, organic or inorganic. It has excellent properties. Since this organic silicon-based thin film has a nearly perfect inorganic structure near the surface, it is a functionally graded thin film having various properties remarkably superior to those of ordinary organic substances. Moreover, since this organosilicon thin film is excellent in properties as a dielectric, the method of the present invention is also an excellent method for synthesizing a dielectric thin film on various materials.

[Brief description of drawings]

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

[Explanation of symbols]

 1 Upper electrode 2 Lower electrode 4a Base material 4b Organosilicon thin film 5 Reaction tank

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Sachiko Okazaki 2-20-11 Takaido, Suginami-ku, Tokyo (72) Inventor Masuhiro Ogoma 843-15 Shimoshinkura, Wako-shi, Saitama

Claims (5)

[Claims] 1. A silicon-based thin film containing an organic substance in its structure, which is formed on the surface of a base material, is treated in plasma excited by glow discharge under atmospheric pressure or a pressure in the vicinity thereof. Surface modification method. 2. The pressure at or near atmospheric pressure is 500.
The method for modifying a surface according to claim 1, wherein the surface modification is in the range of -1500 mmHg. 3. The silicon-based thin film has the general formula: R¹ _nSiX
_4-n(However, in the formula R¹ Are the same or different substitutions
Represents an unsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms, and X represents
Indicates a hydrolyzable group and hydrogen. Silicon represented by n = 0 to 3)
Single or mixture of elementary compounds and / or partial addition thereof
Is it a cured product of a coating material composed mainly of water decomposition products?
A method for modifying a surface according to claim 1 or 2, wherein
Law. 4. The method for modifying the surface according to claim 1, wherein the silicon-based thin film is a plasma-polymerized film obtained by polymerizing a polymerizable silicon compound monomer alone or in a mixture in plasma. 5. The surface modification method according to claim 1, wherein the silicon-based thin film has a thickness of 3 μm or more.