JPH02107773A - Formation of carbon-based coating film - Google Patents

Abstract

PURPOSE:To form a carbon coating film having superior mechanical stress resistance, transparency and low resistivity by mixing a gas having C-F bond with a gas having C-N bond and H2 or a gas having C-H bond and by bringing the mixture into a plasma chemical reaction under an applied specified bias. CONSTITUTION:A gas having C-F bond such as CF4 or C2F6 is mixed with a gas having C-N bond such as N(CH3)3 or N(C2H5)3 or further mixed with H2 or a gas having C-H bond such as C2H4 or CH4. It is proper that each of the gases has a gaseous state under 0.001-10Torr pressure. The gaseous mixture is brought into a plasma chemical reaction and a coating film is formed on the film forming surface of a substrate. At this time, a self-bias or an external bias of -50 to -2,000V is applied on the substrate. A coating film based on C combined with N and F through C-N bond and C-F bond or further contg. H in the form of C-H bond is obtd. This coating film is used as a protective coat having low resistivity, generating no static electricity and also having superior mechanical stress resistance to wear, etc., and high transparency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Application of the Invention The present invention provides a method for producing a film containing carbon as a main component during plasma CVD. a first gas having and C-
The present invention relates to a method of performing plasma CVD while applying a bias of -50 to -2000 V to a composite body including at least a second gas having an N bond and having a surface to be formed during plasma CVD.

``Prior art'' Coating the surface of relatively soft materials such as glass, metals, plastics, and resins with a film that is harder than those soft materials is effective against mechanical stresses such as abrasion and scratches. .

Such films include AhCh, TiN, BN, WC.
, SiC.

Inorganic films such as 5iJ4+51Oz and "composite with carbon film" filed by the present inventor (Patent Application No. 146930, filed in 1982) are known. however,
The above-mentioned known protective films already have high electrical resistivity, tend to generate static electricity, and tend to attract dirt and dust in the atmosphere to their surfaces.

In addition, when used in composite materials that actively apply an electric field and utilize static electricity, such as photoreceptors used in electrophotographic processes, charges accumulate on the protective film with high electrical resistance. There was a problem that the expected performance could not be achieved for a long period of time.

One possible way to solve such problems is to add a conductive substance to the known film.

In this case, the added conductive substance becomes a light absorption center, and light absorption occurs in the above-mentioned known protective film, making it unsuitable for applications requiring transparency in the infrared and visible ranges. It disappears.

Conventionally, in order to carry out such a method, C2H, and NF:+,
There is a plasma CVD method that uses carbon as a main component to which nitrogen is added using a reaction with N11ff. But in this case,
Fluorine and nitrogen are added to the formed film, but although they have N-F bonds or N-)1 bonds, they also have C-F bonds and C-N bonds with carbon, which is the main component. cannot be constructed in a sufficiently stable manner. Therefore, when this surface is subjected to long-term friction, or when used as a protective layer for photosensitive drums for electrostatic copying machines, nitrogen (N) and fluorine (F)
degassing, resulting in defects such as increased electrical resistance and decreased reliability. Therefore, the electrical resistance is 1X106~5X10''Ω even at the initial stage, even when friction is applied to the surface 105 to 107 times, and even after heat treatment.
There has been a need for a method for producing a film whose main component is carbon, which stably has a predetermined value of cm and has stable physical properties in any one-component atmosphere.

"Structure of the Invention" An object of the present invention is to solve the above-mentioned problems and simultaneously satisfy mechanical stress resistance as a protective film, problems arising from static electricity, and transparency.

Therefore, 0.1 to 50 at. A film whose main components are fluorine having a bond, nitrogen having a C--N bond, or carbon to which hydrogen is added in addition to these is formed on the surface of the substrate. At this time, plasma C
C-F is added in advance to the gas as the starting material used in the VD method.
When using a first gas having a bond and a second gas having a C-N bond in advance, or when these first and second gases are used,
and a third gas having a hydrogen or C-N bond, and during film formation, a self- or external direct current of -50 to -2000 V is applied to the substrate having the surface to be formed. It is characterized in that it is carried out while applying a bias voltage.

CF4. CzF6. C+Fa, C11F3
．． CHzFz.

At least one gas selected from C113F is used.

Further, as the second gas having a C-N bond, N (C
113) 3, N (Czlls) 3, II
N (C2115) 2. HzN (CII3),
A second gas selected from IIN (CzL) 211□N (C2115) is used. In addition to these, C
A third gas having -11 bonds is used. That is, C2)14. CI+4(:2H2,C311
a, at least one selected from CzH6 or hydrogen (
11□), and these first, second, and third gases are 0
．． 001~l Q torr as a gas, and use these to form a film containing carbon as the main component.
Produced using the VD method.

The film according to the present invention can be produced by simultaneously introducing the above-mentioned raw materials, that is, a carbon raw material having a C-F bond and a nitrogen raw material having a CN bond, into a plasma reaction chamber.
At this time, by adjusting the flow rates of the first gas and the second gas, the amount of C--F bonding and the amount of nitrogen having C--N bonding added into the film can be controlled.

The added amounts of C--F bonds and C--N bonds created by the method of the present invention are observed as differences in electrical conductivity (reciprocal is specific resistance), transmittance, and hardness. The experimental results of changes in electrical conductivity when the flow rates of the first gas and the second gas are changed are shown below.

Carbon fluoride, for example C2F4, was used as the first gas.

In addition, as a second gas, trimethylamine (N(CH:
+)z) was used.

This gas is solid at -124°C, boiling point 3.2-3,
2000 at 8°C1 density 0.6709.300K
m) It is a gas having a paper pressure of Ig.

Furthermore, ethylene (C2114) was used as a third gas. CzFb flow rate 11005CC, ethylene flow rate 1
1005ec, and the flow rate of N(Ctl+)z was roughly varied. Reaction pressure 0.1 torr, input power density 0
．． 08W/cm2 (50W). As shown in FIG. 1, as the amount of N(C1h)x increases, the specific resistance decreases. Furthermore, the second factor is the relationship between bias voltage and Pinkers hardness. In the drawing, as the 'tLffl of N(CI+3):l increases, the Pinkers hardness decreases, and the bias voltage also increases (as a result, it increases.A decrease in hardness means a decrease in internal stress). means.

As described above, the specific resistance, hardness, transmittance, etc. of the coating can be changed over a relatively wide range. That is, the optimum characteristics required for various applications can be easily obtained at relatively low cost.

Also, a C-F bond and a C-N bond or a C-F bond and a C-N
Bond and C-1! A film whose main component is carbon to which fluorine, nitrogen, and hydrogen are added in a bonded state is characterized by low internal stress. This is because the dangling bonds that normally exist in carbon are terminated with fluorine, reducing the internal stress by relaxing the attractive force of the dangling bonds, but all dangling bonds are terminated with fluorine or hydrogen. is not terminated, and some dangling bonds remain in the film, which is thought to be one of the causes of internal stress. Here, fluorine, which is more reactive than hydrogen, forms C in the initial gas state.
Nitrogen has a -F bond, and nitrogen, which exhibits electrical conductivity, also has a C-N bond in its initial gas state.

Since C and N are located next to each other in the periodic table of elements, they simply decompose sufficiently in plasma, and if they are independent gases, they cannot stably combine with carbon. However, N(
CI+3): When using l, the N-C bond already has,
The H of Cth and F having a C--F bond combine with each other to form IIF, and the remaining carbons tend to form sp' bonds. As a result, for the first time, it is possible to create a film whose main component is carbon with controlled valence electrons.

A film containing fluorine and nitrogen, or carbon to which fluorine, nitrogen, and hydrogen are added as a main component, is also excellent in terms of heat resistance.

Films mainly composed of fluorine and nitrogen or carbon to which fluorine, nitrogen, and hydrogen are added can be deposited at a substrate temperature ranging from room temperature to 4.
Another feature is that the film can be formed at a low temperature of 50'C or less, preferably room temperature to 150C.

Therefore, the substrate of the composite can be made of materials that cannot be heated to high temperatures, such as plastics, organic materials such as organic photosensitive resins, and selenium semiconductors.

The manufacturing method will be described below according to the drawings.

FIG. 3 shows an outline of a plasma CVD apparatus used in the present invention for forming a film mainly composed of carbon to which fluorine and nitrogen or fluorine, nitrogen, and hydrogen are added.

In the drawing, in the doping system (1), hydrogen as a carrier gas is transferred from (2) to the first doping system having a C-F bond.
A hydrocarbon gas that is a reactive gas such as C2F4 (3
), a gas having a C-N bond, for example, N(C1h)3
From (4), a gas having a C-11 bond, for example C2
114 is introduced from the nozzle (9) into the reaction system (8) through the valve (6) and the flow meter (7). It is effective to preactivate the reactive gas by applying microwave energy at 00) for excitation of the reactive gas before reaching this nozzle.

The reaction system (8) includes a first electrode (11) and a second electrode (1
2) was established. In this case, condition 1 (first electrode area/second electrode area) was satisfied. A pair of electrodes (1
Electrical energy is applied between 1) and (12) from a high frequency power supply (13), a matching transformer (14), and a DC bias power supply (15) to generate plasma. The exhaust system (16) exhausts unnecessary gas through a pressure regulating valve (17), a turbo molecular pump (18), and a rotary pump 09). For the reactive gas, the pressure in the reaction space Q is 0.001 to 10 torr, typically 0.01 to Ito
0 due to energy from high frequency or direct current under rr
．． Energy of 05 to IKW is added.

In particular, when the excitation source has a frequency of 1 GHz or more, for example 2.45 Gtlz, hydrogen is separated from the C-H bond, and the frequency source is 0.1 to 50 M11z, for example], 33.5
At the frequency of 6Ml1, C-C bonds and C-C bonds are decomposed to create -C-C- bonds, and the unpaired bonds of carbon collide with each other to covalently bond, creating a stable diamond structure. It may have a locally formed structure.

In experiments, a DC bias of +200 to -1800V is applied.

This is because when the DC bias is zero, the self-bias has a value of 1200ν (with the second electrode at ground level).

It has been found that the Vickers hardness can also be increased when the bias voltage for the substrate is -50 to -2000V, preferably -100 to -1000V. This bias voltage is simply applied by applying a cylindrical frequency voltage with a frequency of 13.56 MIIz, and if the substrate having the surface to be formed is DC-grounded, or by adding a self-bias by giving shape anisotropy to the pair of electrodes. If not, the Vickers hardness is 300 kg/mm even if a film containing carbon as the main component is formed.
2 or less, it is impossible to form a film as so-called DLC (diamond-like carbon). Particularly when nitrogen is used as a material for controlling electrical conductivity, this bias voltage is an extremely important requirement in order to ensure that the deposited film containing carbon as its main component is stable and highly reliable.

As described above, C-C is formed on the surface to be formed by plasma.
Fluorine having a C-F bond and nitrogen having a C-N bond, or in addition to these, C-1
A hydrogen-containing carbon having one bond was produced. This electromagnetic energy was supplied at 50 W to IKW, and plasma energy of 0.03 to 3 W/cffl per unit area was added. The transmittance of carbon in which fluorine and nitrogen are combined in advance is 4th.
As shown in the figure, a nearly transparent film was obtained that had a transmission of 95% or more in a wavelength range of 600 nm or more, and a transmission of 50% or more even at 400 nm. Furthermore, the internal stress of the film was very small, at 1710 or less, compared to a film containing no fluorine or nitrogen. 1 to chemicals such as acids, alkalis, and organic solvents at room temperature.
Even after soaking for hours, no change was observed when observing the surface with an optical microscope at 400x magnification.
Although it was left in a constant temperature bath (air) heated to 1 hour,
No changes were observed on the surface, and a chemically and thermally stable film could be obtained.

In particular, as a photosensitive drum using a coating mainly composed of carbon, it is an extremely stable film that does not change its electrical resistance or transmittance even when 105 to 106 sheets of paper (A4 size) are rubbed on it. I understand.

The above-mentioned production method is just an example, and even if it is a well-known glow discharge plasma, an arc discharge plasma, or a plasma using ECR (electron cyclotron resonance), good.

Hereinafter, one composite to which the present invention is applied will be described in more detail according to Examples.

``Example IJ'' An example in which the composite according to the present invention is applied to a photoreceptor used in an electrophotographic process will be described below.

FIG. 5 shows the structure of a photoreceptor to which a coating mainly composed of carbon according to the present invention is applied. Approximately 200μm thick P
ET sheet (1) with a 600-layer thick Al vapor deposited layer (2
), a charge generation layer (4) of 0.6 to 1.2 μm is provided between the intermediate layer (3), and light ( 7) is absorbed by the charge generation layer to generate electron-hole pairs. If the charge transfer layer or protective layer is negatively charged in advance, holes generated in the charge generation layer move through the charge transfer layer only in the area where light is incident, neutralizing the negative charges. . At this time, electrons generated in the charge generation layer pass through the intermediate layer, reach the Al deposited layer, and are discharged. The negative charge remaining in the area where no light was incident then adsorbs toner and is transferred to the transfer paper, forming an image on the transfer paper depending on whether or not light is incident.

The protective layer formed here uses the present invention, and its specific resistance is reduced to 1×10 by the flow of N(C)h):+.
6 to 5 XIO” (Ωcm) preferably lXIO3 to
5 x 10" (Ωcm). Therefore, there is no lateral movement of the electrical charge that occurs due to the specific resistance being too low, and the boundary of the area where the light is incident is clear without blurring. Therefore, the transferred image was also clear.Also, if the resistivity is too high, charges will gradually accumulate on the protective film with repeated use, making it impossible to remove used toner, and the transfer paper will become black. A phenomenon occurs.

Since the protective film according to the present invention has a resistivity controlled to such an extent that no charge is accumulated, such a phenomenon does not occur, and C2
In the method using 114 and NF3, image loss was observed after 2×10' copies, but with the method of the present invention, 1×10' to 1
Even when copying XL06 sheets (equivalent to 64th edition), no image loss was observed, and high-quality transferred images could be obtained for a long period of time.

Further, the transmittance of the protective film used here was 80% or more in a wavelength range of 500 nm or more, and 60% or more in a wavelength range of 400 nm or more. Therefore, the photoreceptor of this practical example was sufficiently usable even in the visible light range.

Of course, it goes without saying that durability against mechanical stress such as abrasion resistance and seeding resistance is improved.

Furthermore, the protective film used here had reduced internal stress and good adhesion. That is, even when the sheet-like phosphor was bent to a radius of curvature of 10 mm, no cranking was observed in the protective film, and no peeling occurred.

In this embodiment, a sheet-like organic photoreceptor has been described as a photoreceptor, but the protective film according to the present invention can be similarly constructed for a drum-shaped organic photoreceptor, an amorphous silicon photoreceptor, and a selenium photoreceptor. The effect of this can be obtained.

"Example 2" A typical thermal print head structure is shown in FIG.

A glaze (2) is formed on an insulating substrate (1), a protruding glaze (3) is formed on the part corresponding to the heating element at the same time as the glaze (2), and then a heating element (4) is formed on the insulating substrate (1). and an electric conductor (5) are sequentially laminated, and then a heating element portion (21) is formed on the protruding glaze using a known photolithography technique, and finally, fluorine and nitrogen or fluorine according to the present invention are laminated. and nitrogen and hydrogen into a C-F bond, C-N
A protective film is a film whose main component is carbon that contains bonds.
6).

The protective film usually used is an inorganic film such as a silicon nitride film.
Although the film thickness is as large as 5 μm, the protective film (6) used in this example has the same characteristics as the protective film formed in Example 1, and controls the flow rate of N(C1h)z. By this, a hard film with a Vickers hardness of 2000 kg/mm 2 or more can be formed. Therefore, a coating with a thickness of about 1 μm is sufficient for practical use.

Furthermore, the internal stress of the protective film used in this example was 109d.
It has a small size of less than yn/cm" and has good adhesion, and has a
It was confirmed that the heat resistance test for 1 hour (in air) at °C was also good.

Furthermore, the specific resistance of about 1010 Ωcm is convenient for static electricity countermeasures, reducing dirt and dust that can cause scratches.
The effect of static electricity on electronic circuits was also reduced.

In this application example, a known heating element (4) is used, but it is also possible to use a film mainly composed of carbon containing C--F bonds and C--N bonds according to the present invention as the heating element. That is,
If a film is formed under film-forming conditions that increase the concentration of fluorine and nitrogen, and the specific resistance of the film is set to 10' to 104 Ωcm, this film can be used as a heating element.

``Example 3'' In this example, the film containing carbon as the main component of the present invention was applied to a contact type image sensor, and a film containing carbon as the main component having the structure shown in FIG. 7 was formed.

As shown in FIG. 7, electrodes and amorphous silicon are laminated on a transparent glass substrate (33) using a known plasma CVD method, and the electrodes and amorphous silicon layer are processed using a photoetching method to form a photosensor element. After forming (34), transparent polyimide (35
) was applied using a known spinner method to fabricate a contact image sensor. Thereafter, a protective film (36) with a thickness of 2.0 μm was formed on the transparent polyimide (35) of the image sensor by the method described in Example 1.

The Pinkers hardness of the protective film was measured and was 2500.
Kg/mm2, and the specific resistance was 1X10"0 cm.The formed carbon film had a hardness similar to that of diamond on the surface on which it was formed and on the surface, and an appropriate electrical insulation property as a countermeasure against static electricity. This prevents the above layer from being scratched by irregularities on the document surface or stapler metal fittings, and prevents static electricity from accumulating even if static electricity is generated due to friction between the document and the protective film. In addition, it was possible to suppress the electrical influence on the optical sensor element and to prevent the contamination of impurities in the translucent polyimide.

"Effect J" As stated above, the present invention is a composite having a film mainly composed of carbon having a C-F bond, a C-N bond, or a C-11 bond in addition to these, and the film contains fluorine. The degree of drainage or hydrophilicity, hardness, translucency, and resistivity of the film can be easily and inexpensively changed by making the surface water-drainable by adjusting the amount of nitrogen added and by controlling the resistivity by changing the amount of nitrogen added. In addition, the internal stress of the coating is small.
It has good adhesion.

As described in the examples, in the present invention, in the composite to which a film mainly composed of carbon to which a halogen element and nitrogen or hydrogen, a halogen element, and nitrogen are added is applied, in the present invention, a film having a C-N bond is applied. The amount of gas used is Nll:l
, NF:l can be used at about 1/20th the same specific resistance, and the ionization rate (amount of active impurities/amount of added impurities) is also 20 times higher.

Moreover, compared to the case where a film containing carbon as a main component was not applied, the life span and reliability of the composite could be significantly improved.

The method of the present invention is not limited to the plasma CVD apparatus shown in FIG. The important thing is that in the initial state,
By using a gas having C-F bonds and C-N bonds and by applying a negative DC bias to the substrate automatically or artificially, in addition to this, C-11 bonds or i
t is added at the same time. Also, during plasma CvD, 0.001 to 1Qtor Yayoshi Diagram Hias Electric Toy (V) (Phase Number Q Heat) Kaki-Jt, (*v) x square 1 Figure 3 Figure

Claims (2)

[Claims] 1. Mixing a first gas having a C-F bond and a second gas having a C-N bond or a third gas having hydrogen or a C-H bond in addition to the first and second gases, By causing a plasma chemical reaction while applying a self-bias or an external bias of -50 to -2000V, nitrogen and fluorine form C-N bonds and C-N bonds on the surface to be formed.
A method for producing a film mainly composed of carbon, which comprises forming a film mainly composed of carbon added with a -F bond. 2. In claim 1, the first gas having a C-F bond is CF_4, C_2F_6C_3F_
8, at least one gas selected from CHF_3, CH_2F_2, CH_3F, the second gas having a C-N bond is N(CH_3)_3, N(C_2H_5)_3,
HN(CH_3)_2, H_2N(CH_3), NH(
At least one gas selected from C_2H_5)_2, H_2N (C_2H_5), and the gas having hydrogen (H_2) or a C-H bond is the first or second gas, and the gas having a C-H bond or C_2
Consists of a third gas selected from H_4, CH_4, C_2H_2, C_3H_8, pressure 0.001 to 10 to
A method for producing a film mainly composed of carbon, characterized in that it is made of a gas that exhibits a gaseous state at rr.