JP2001049433A - Resin substrate coated with amorphous carbon film and film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable extremely high hardness and transparency to be compatible by coating an amorphous carbon film in such a manner that the concn. of hydrogen atoms contained in the carbon film gradiently reduces from the grain boundary layer between a resin substrate and the carbon film toward the outermost surface layer of the carbon film. SOLUTION: The position of a substrate holder is set to plasma so as to satisfy |(L-D)/D |<=0.5, and, by using a plasma CVD method, an amorphous carbon film is applied on a resin substrate in such a manner that the concn. of hydrogen atoms contained in the carbon film on the grain boundary layer between the resin substrate and the carbon film is controlled to >=2.0×1022 atoms/cm3, and the concn. of hydrogen atoms contained in the carbon film on the outermost surface layer of the carbon film is <=1.8×1022 atoms/cm3, and the concn. of hydrogen atoms contained in the carbon film gradiently reduces from the grain boundary layer between the resin substrate and the carbon film toward the outermost surface layer of the carbon film. L denotes the shortest distance from the center of a waveguide to the substrate holder, and D denotes the longest distance from the center of the waveguide to the edge of plasma generated in the direction of the substrate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resin coated with an amorphous carbon film having both extremely high abrasion resistance and transparency, and a method for forming the same.

[0002]

2. Description of the Related Art In general, plasma CVD (Chemical Vapor)
It is not easy to coat the hard carbon thin film on the resin substrate using the Deposition method because the plasma is at a high temperature and the resin substrate is melted. As known methods, a sputtering method, an ion plating method, and an ion beam method are known, but it is difficult to control the content of hydrogen. JP-A-60-217148 discloses a high frequency (13.56 M
(Hz) Although a technique of coating a hard carbon film on a resin substrate with a power supply is disclosed, it is not sufficient in terms of achieving both hardness and transparency. Japanese Patent Application Laid-Open No. 1-167111 discloses a technique in which films are alternately deposited in layers to obtain a diamond-like carbon film having a small film stress and excellent surface smoothness, but the substrate temperature reaches several hundred degrees. Therefore, there are problems such as melting and deformation of the resin substrate, and the resin substrate cannot be applied to coating. Japanese Patent Application Laid-Open No. Hei 6-88209 discloses a technique of coating a hard carbon film on a resin substrate using a high-frequency (13.56 MHz) power supply. However, it is not sufficient from the viewpoint of achieving both hardness and transparency. Japanese Patent Application Laid-Open No. 10-1305 discloses a technique of reducing the amount of hydrogen contained in a carbon film to increase hardness, but is insufficient from the viewpoint of coating on a resin substrate and the viewpoint of transparency.

In general, the properties of an amorphous carbon thin film include hardness,
It shows excellent properties such as surface smoothness, chemical stability, heat resistance, insulation properties, chemical resistance, and gas barrier properties, but they are highly correlated with the molecular structure of the amorphous carbon film. Also, as a parameter governing the molecular structure of the amorphous carbon film,
(1) The sp3, sp2, and sp component ratio of carbon, (2) the amount of hydrogen atoms contained, (3) the types and amounts of atoms other than carbon and hydrogen incorporated in the skeleton structure, and the like can be considered. Therefore, controlling these parameters is important in establishing a technique for coating a carbon thin film with a purpose. Generally, in order to control these parameters, some known carbon thin film forming methods, such as, for example, a sputtering method, an ion plating method, an ionization vapor deposition method, etc. A microwave plasma CVD method that uses a microwave as a generated energy source and can apply a bias (high frequency or the like) to a substrate is excellent. In addition, the microwave plasma CVD method having a high energy density is also excellent for forming a film having a relatively high diamond property and capable of exhibiting high hardness and high transparency, which is an object of the present invention. However, generally, microwave discharge has an electron density of 10 ¹¹ (cm ³ ), a gas temperature of 1
000 (K) and high frequency discharge (electron density is 10 ⁸
Even when compared to (10 to 10 ¹⁰ (cm ³ ), gas temperature to 700 (K)), it is not suitable for coating a carbon thin film on a substrate having low heat resistance, for example, a resin substrate. In other words, when attempting to coat a carbon thin film using microwave plasma, there are problems such as melting, foaming, and deforming the resin substrate even when the substrate holder is cooled and cooled. Was. Even if it could be made, it could only cover a very soft carbon film.

[0004]

According to the present invention, a carbon film is coated on a resin substrate by using a microwave plasma CVD method for modifying the resin surface without deforming and melting the resin substrate. An object is to achieve both high hardness and extremely high transparency.

[0005]

In view of such circumstances, the present inventors have made the structure of the carbon film coated on the resin base into a multilayer structure of carbon films having different hydrogen atom concentrations, and further, From the surface layer to the outermost surface layer, a multilayer structure in which the concentration of hydrogen atoms is low is controlled by controlling the relationship between the plasma size and the position of the substrate holder, and the substrate bias is minimized when forming the substrate resin-side carbon film layer. It has also been found that, by increasing the thickness at the time of forming the outermost surface side carbon film layer, a carbon film having both high hardness and high transparency can be coated without deforming the resin substrate.

That is, according to the present invention, the amorphous carbon film is coated so that the concentration of hydrogen atoms contained in the carbon film decreases gradually from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film. And a resin substrate. Further, when the concentration of hydrogen atoms in the carbon film in the interface layer between the resin substrate and the carbon film is 2.0 × 10 ²² atoms / cm ³ or more, the concentration of hydrogen atoms in the carbon film in the outermost surface layer of the carbon film is reduced. 1.8 × 1
0 ²² atoms / cm ³ or less, such that the concentration of hydrogen atoms contained in the carbon film decreases gradually from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film. A resin substrate provided with a carbon film is provided.

Further, according to the present invention, the position of the substrate holder with respect to the plasma is adjusted so that the resin substrate coated with the amorphous carbon film satisfies | (LD) /D|≦0.5. And using a plasma CVD method to a) reduce the concentration of hydrogen atoms contained in the carbon film in a gradient from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film, or b). The concentration of hydrogen atoms in the carbon film of the interface layer between the resin substrate and the carbon film is 2.0 × 10 ²² atoms / cm ³ or more, and the concentration of hydrogen atoms in the carbon film of the outermost surface layer of the carbon film is 1 0.8 × 10 ²² atoms / cm ³ or less, so that the concentration of hydrogen atoms contained in the carbon film is gradually reduced from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film. (L: The shortest distance from the center of Namikan to the substrate holder, D: the longest distance from the center of the waveguide to the end of the plasma generated in the substrate direction). Furthermore, according to the present invention, the plasma generation source uses a microwave, and the negative substrate bias absolute value is 0 V or more and 100 V or less when forming a carbon film layer at the interface between the resin substrate and the carbon film. 10 V or more and 5000 V when forming the outermost surface layer of the carbon film
The position of the substrate holder with respect to the plasma is set so as to satisfy the following and | (LD) /D|≦0.5,
The plasma CVD method is used to a) reduce the concentration of hydrogen atoms contained in the carbon film in a gradient from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film; The concentration of hydrogen atoms in the carbon film of the interface layer with the film is 2.0 × 10 ²² atoms / cm ³ or more, and the concentration of hydrogen atoms in the carbon film of the outermost surface layer of the carbon film is 1.8 ×
10 ²² atoms / cm ³ or less, and amorphous on the resin substrate so that the concentration of hydrogen atoms contained in the carbon film decreases gradually from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film. It can be manufactured by forming a high quality carbon film.

Hereinafter, the present invention will be described in detail.

The resin used in the present invention is acrylic acid,
Polymers and copolymers of methacrylic acid, esters of these acids or acrylonitrile, especially acrylic polymers represented by polymethyl methacrylate, etc .; polycarbonates represented by poly (bisphenol-A carbonate); polyethylene terephthalate; Butylene terephthalate, polyester represented by polyethylene naphthalate, etc., or nylon 6, polyamide represented by nylon 6, 6, or polyimide, polyaramid, or polyethylene;
Polyolefin represented by polypropylene or the like, or polystyrene, styrene represented by styrene-acrylonitrile copolymer, styrene-acrylonitrile-butadiene copolymer, styrene-butadiene copolymer, styrene-butadiene copolymer hydrogenated, and the like Polymer, or polyvinyl chloride, polyvinylidene chloride,
Examples thereof include halogen-based polymers represented by Teflon and the like, and super engineering plastics represented by polyarylate, polyether sulfone, polyphenylene sulfide, liquid crystal polymer and the like. In particular, a transparent plastic typified by polymethyl methacrylate, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, polyarylate, aramid, or the like is preferable from the viewpoint of utilizing the properties of the highly transparent carbon film according to the present invention. The shape of the resin substrate is not particularly limited, and a sheet, a film, a bottle, an injection molded product, an extruded product, and the like are selected.

The amorphous carbon film referred to in the present invention is amorphous diamond-like carbon, and contains diamond, graphite, and polymer components. Here, the polymer is a hydrocarbon structure that forms a network three-dimensionally and has many hydrogen atoms. In addition, the parameters controlling these structures include the atomic hydrogen content, sp3
The carbon component ratio can be considered, and the physical properties of the amorphous carbon film greatly differ depending on the ratio. Generally, the hydrogen content is small,
The larger the sp3 carbon component ratio, the more diamond-like and harder.

According to the present invention, first, a soft carbon film having a large hydrogen content is coated as a first layer on the interface side between the resin substrate and the carbon film. This is because of the high hydrogen content,
It has small internal strain, is colorless and transparent, has excellent adhesion to the substrate with the resin, and serves as a binder with the next hard film layer. further,
It becomes a layer having better heat resistance and thermal conductivity than the resin substrate, and enables the formation of the next hard film layer. Next, as a second layer, by applying a negative substrate bias, the energy of hydrocarbon ions generated in the plasma is accelerated, and a hard film containing less hydrogen can be obtained. If a film is to be formed directly on the resin substrate under the same conditions as the second layer, the heat resistance of the resin substrate is insufficient.
With foaming and deformation of resin. Further, a multilayer film of an amorphous carbon film may be used so that the amount of hydrogen contained in the third layer, the fourth layer, and the outermost surface layer is gradually reduced.
Further, it was found that as the content of hydrogen decreases, the refractive index of the carbon film itself increases, but the difference in the refractive index between the layers decreases, and high transparency is exhibited. Therefore, both high transparency and high hardness can be achieved.

Further, according to the film forming method of the present invention, by disposing the substrate or the substrate holder at an appropriate position with respect to the magnitude of the generated plasma, the deformation of the resin substrate,
A hard carbon thin film can be formed without causing damage. That is, when L: the shortest distance from the center of the waveguide to the substrate holder, D: the longest distance from the center of the waveguide to the end of the plasma generated in the direction of the substrate, (L−
D) / D is -0.5 or more and 0.5 or less, preferably -0.0.
4 to 0.4, more preferably -0.3 to 0.
3 or less. If (LD) / D is less than -0.5, the resin base is too close to the center of the plasma, and the resin is deformed at high temperatures. On the other hand, if it is larger than 0.5, the carbon film is not coated because the resin base is too far from the center of the plasma and the number of hydrocarbon ions considered as active species is not sufficient.

The method for producing the amorphous carbon film of the present invention includes ion plating and sputtering, for example, physical vapor deposition such as ion beam sputtering, plasma CVD, microwave CVD, and high-frequency CVD. Can be In these methods, a plasma is generated in a film forming apparatus to ionize or excite a gas. Examples of the method include a method in which a gas is subjected to plasma decomposition by applying a DC voltage, and a method in which a high frequency is applied. Plasma decomposition by microwave discharge, plasma decomposition by electron cyclotron resonance, and thermal decomposition by heating with a hot filament.

However, in order to lower the gas temperature by non-equilibrium plasma to form a film on a resin substrate, high-frequency plasma and microwave discharge plasma are preferable. Furthermore, it is possible to apply a bias (high frequency or the like) to a substrate by flowing a hydrocarbon gas and using a microwave as a plasma generation energy source, and to apply the method to an ECR (Electron Cyclotron Resonance) method capable of reducing the pressure and the temperature. In terms of
Microwave plasma CVD is more preferred.

As a source gas for forming the amorphous carbon film, a gas containing carbon atoms and hydrogen atoms is used. Examples of such a gas include alkane-based gases such as methane, ethane, propane, butane, pentane, and hexane; ethylene, propylene, butene,
Alkene-based gases such as pentene and butadiene; alkyne-based gases such as acetylene and methylacetylene; benzene, toluene,
Aromatic hydrocarbon gases such as xylene, indene, naphthalene and phenanthrene; cycloalkane gases such as cyclopropane and cyclohexane; alcohol gases such as methanol and ethanol; ketone gases such as acetone and methyl ethyl ketone; And aldehyde-based gases such as ethanal. The above gases can be used alone or in combination of two or more.

Other source gases include a mixed gas of the above gas and hydrogen gas, a mixed gas of the above gas and an oxygen-containing gas such as carbon monoxide gas and carbon dioxide gas, hydrogen gas, Carbon gas, mixed gas with oxygen-containing gas such as carbon dioxide gas, oxygen gas, water vapor, carbon monoxide gas,
A mixed gas with an oxygen-containing gas such as carbon dioxide gas may be used. Further, as another source gas, a mixed gas of the above source gas and a rare gas may be used. For example, helium, argon, neon, xenon and the like can be mentioned, and these can be used alone or in combination of two or more.

The negative substrate bias in the first layer is preferably from 0 V to 100 V, more preferably from 0 V to 50 V, further preferably from 0 V to 30 V. 100V
If it is larger, the resin substrate will be deformed. The negative substrate bias in the second layer or more is preferably 10 V or more and 5000 V or less, more preferably 50 V or more and 1000 V or less.
The voltage is more preferably 100 V or more and 500 V or less. If it is less than 10 V, acceleration energy sufficient to harden the film cannot be obtained, and if it is more than 5000 V, power is simply wasted.

In order to enhance the adhesion of the amorphous carbon film to the surface of the resin substrate, if necessary, the surface of the substrate is degreased.
Known processes such as a cleaning process such as washing for dehydration, a drying process, and a plasma process using a plasma generated from an active gas such as an inert gas such as Ar or an oxygen gas in a vacuum vessel on the substrate surface are performed. May be.

As an energy source required for generating plasma, 1 KHz to 10 GHz, preferably 1 M
Hz to 5 GHz, more preferably 10 MHz to 3 GH
For z, especially microwaves, a frequency of 2.45 GHz is preferred. Output is 10 to 1000 W, preferably 20 to 6
00W, more preferably 30-300W.

The pressure in the system is 0.01 to 100 Pa, preferably 0.1 to 50 Pa, and more preferably 0.3 to 50 Pa.
It is 30 Pa.

In order to prevent the resin substrate from being damaged by heat, it is necessary to cool the substrate holder by circulating a coolant or the like. The temperature of the refrigerant at this time is -200 to 10
° C, preferably -100 to 0 ° C, more preferably -5.
0-5 ° C. Here, the substrate holder is a base on which the substrate is placed, has a structure in which a refrigerant can flow, and has a structure in which a negative rf bias can be applied.

The thus obtained resin coated with the amorphous carbon film of the present invention has a hard carbon film and excellent transparency. Therefore, when the resin substrate is a transparent plastic, it is used for display panels and automobiles. Window materials, architectural window materials,
It can be used as a material that requires abrasion resistance, transparency, chemical resistance, heat resistance, and light weight, such as a noise barrier for a highway and a plastic bottle that requires a high barrier property.

[0023]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.

The physical properties in the examples were determined according to the following methods.

(1) (LD) / D As shown in FIG. 1, the shortest distance (L (cm)) from the center of the waveguide to the substrate holder was measured, and the The distance (D (cm)) from the center (coincident with the center of the waveguide) to the lower end of the plasma in the direction of the substrate was measured and substituted into the formula (LD) / D to calculate.

(2) Using hydrogen atom concentration IR (FTS-60A manufactured by Nihon Bio-Rad),
The infrared absorption spectrum of the C—H bond was measured for the Si wafer substrate sample, and the method already reported (F. Fujimoto, et al., Jpn. J. Appl. Phys., No. 23, 810) was used.
(1984)), the hydrogen atom concentration was calculated according to the following equation 1.

HC = A∫ (α (ω) / ω) dω (Equation 1) where HC: concentration of hydrogen atoms (atoms / cm ³ ) ω: wave number (cm ~ ¹ ) α (ω): wave number ω absorption coefficient ^{(cm ~ 1) a = 1.0} × 10 21 (atoms / cm 2) (3) masked with a thickness of Si wafer substrate in the correction fluid, after the film formation, the masking is removed by ultrasonic cleaning Thereafter, the film thickness of each layer was measured by measuring the level difference using DECTAC 3ST (manufactured by Veeco-solan). For the resin substrate sample, masking was performed in the same manner, and total film thickness measurement was performed.

(4) Deformation of Base The resin base sample was visually inspected for deformation.

：: No deformation ×: Deformation or foaming (5) Surface hardness Dynamic micro hardness tester D
UH-201 (manufactured by Shimadzu Corporation), triangular pyramid indenter (1
15 °) and the surface hardness was measured at a measurement load of 10 mN.

(6) Light transmittance For the resin substrate sample, a UV-VIS spectrometer U-3 was used.
The transmittance (%) at a wavelength of 500 nm was measured using 210 (manufactured by HITACHI).

Example 1 A polycarbonate sheet (PC1600, manufactured by Takiron Co., 1 mm thick) was set as a resin base on a base holder, and a Si sheet for thickness measurement and IR measurement was placed beside the polycarbonate sheet.
The wafer substrate was set. The inside of the substrate holder was cooled while flowing a water / propylene glycol mixed refrigerant (set at -20 ° C). First, Ar gas was flowed at 120 ml / min, the pressure was set to 25 Pa using a pressure control valve, the microwave output was set to 100 W, and plasma cleaning was performed for 3 minutes as a pretreatment of the substrate surface. Then, as raw material gas,
20 ml / min of methane gas and 20 ml / min of hydrogen gas
min and Ar gas were flowed at 120 ml / min, the pressure was set to 25 Pa using a regulating valve, and the microwave output was set to 13 Pa.
0W, match, generate plasma,
The lengths of L and D were measured, and the first layer of the amorphous carbon film was covered for 28 minutes. After stopping the microwave output and gas flow and returning to normal pressure, the resin wafer sample was left as it was, and the second layer Si wafer was replaced with the first layer Si wafer. Further, after evacuation and flow of a gas having the same composition as that of the first layer, the pressure was set again to 25 Pa, the microwave output was set to 130 W, plasma was generated by matching, and the negative substrate bias value was set to 150 V. Plasma was generated for 2 minutes, the lengths of L and D were measured, and the second layer of the amorphous carbon film was covered. (LD) /
Table 1 also shows the results of D, hydrogen atom concentration, film thickness, substrate deformation, hardness, and light transmittance.

Example 2 Polymethyl methacrylate (PMMA) as a resin substrate
Sheet (Deragrass A transparent 999, Asahi Kasei Corporation)
, 1.5 mm thick) and as shown in Table 1, except that the microwave output, the substrate bias, and the position of the substrate holder were changed.

Example 3 Polyethylene terephthalate (PET) as a resin substrate
Film (Lumirror 250T60, manufactured by Toray Industries, Inc .;
25 mm thickness) and as shown in Table 1,
Coating the third layer, changing the microwave power, the substrate bias, the substrate holder position, and the first layer,
The deposition times of the second layer and the third layer were set to 26 minutes and 2 minutes, respectively.
Except for two minutes, the same procedure as in Example 1 was performed.

Comparative Example 1 The procedure of Example 1 was repeated, except that the coating of the second layer was not performed. However, the film formation time was 30 minutes. From the results in Table 1, it was found that the hardness was low.

Comparative Example 2 The procedure of Example 1 was repeated, except that the first layer was not coated. However, the film formation time was 30 minutes. From the results in Table 1, it was found that the substrate was accompanied by deformation.

Comparative Example 3 The procedure of Example 1 was repeated, except that the coating of the second layer in Example 1 was not performed, and the position of the substrate holder was moved closer to the waveguide. However, the film formation time was 30 minutes. From the results in Table 1, it was found that the substrate was accompanied by deformation.

Comparative Example 4 The procedure of Example 1 was repeated, except that the coating of the second layer in Example 1 was not performed, and the position of the substrate holder was moved away from the waveguide. However, the film formation time was 30 minutes. From the results in Table 1, it was found that the carbon film was not coated on the resin substrate.

From these results, the structure of the carbon film coated on the resin substrate is a multilayer structure of carbon films having different hydrogen atom content concentrations, and the hydrogen atom content concentration decreases from the resin substrate side to the outermost surface layer. Such a multilayer structure,
By controlling the relationship between the size of the plasma and the position of the substrate holder,
In addition, by setting the substrate bias as small as possible when forming the carbon film layer on the substrate resin side and increasing it when forming the carbon film layer on the outermost surface side, both high hardness and high transparency can be achieved without deforming the resin substrate. It was found that the coated carbon film could be coated.

[0039]

[Table 1]

[0040]

According to the present invention, a carbon film is coated on a resin substrate without deforming and melting the resin substrate by using a microwave plasma CVD method for modifying the resin surface, thereby achieving extremely high hardness and extremely high transparency. I was able to balance.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method for forming a resin substrate coated with an amorphous carbon film of the present invention.

Claims (5)

[Claims] 1. A resin substrate coated with an amorphous carbon film such that the concentration of hydrogen atoms contained in the carbon film decreases gradually from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film. 2. The concentration of hydrogen atoms contained in a carbon film in an interface layer between a resin substrate and a carbon film is 2.0 × 10 ²² atoms / cm.
^{3. The} amorphous carbon film according to claim 1, wherein the concentration of hydrogen atoms in the carbon film of the outermost surface layer of the carbon film is 1.8 × 10 ²² atoms / cm ³ or less. Coated resin substrate. 3. The position of the substrate holder with respect to the plasma is set so as to satisfy | (LD) /D|≦0.5,
A) the concentration of hydrogen atoms contained in the carbon film is gradually reduced from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film by using the plasma CVD method, or b) the resin substrate and the carbon film The concentration of hydrogen atoms in the carbon film of the interface layer with the film is 2.0 × 10 ²² atoms / cm ³ or more, and the concentration of hydrogen atoms in the carbon film of the outermost surface layer of the carbon film is 1.8 × 1
0 ²² atoms / cm ³ or less, and amorphous on the resin substrate so that the concentration of hydrogen atoms contained in the carbon film decreases gradually from the interface layer between the resin substrate and the carbon film to the outermost surface layer of the carbon film. Film forming method for coating a porous carbon film. (L: shortest distance from the center of the waveguide to the substrate holder, D: longest distance from the center of the waveguide to the end of the plasma generated in the direction of the substrate) 4. A film forming method according to claim 3, wherein a microwave is used as a plasma generation source. 5. The negative substrate bias absolute value is 0 V or more and 100 V or less when forming a carbon film layer at the interface between the resin substrate and the carbon film, and 10 V or more and 5000 V when forming the outermost surface layer of the carbon film.
The film is formed as follows.
The film forming method according to the above.