JP2007065261A - Reflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reflector which has a high reflectance on a visible light region and is excellent in moisture resistance and sulfur resistance. <P>SOLUTION: The reflector 10 comprises: a base material 11; a silicon compound film 14 which comprises one kind selected from a group consisting of silicon nitride, silicon oxide and silicon oxide nitride; a silver film 13 made of silver or silver alloy which is disposed between the base material 11 and the silicon compound film 14; a hydrocarbon film 15 formed by applying the silicon compound film 14 to plasma treatment; and a substrate film 12 made of oxide which is disposed between the base material 11 and the silver film 13 as necessary. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a reflecting mirror having high reflectance in the visible light region and having moisture resistance and sulfur resistance.

  2. Description of the Related Art Conventionally, a reflecting mirror in which a metal film such as aluminum or silver is formed as a reflecting film on a base material such as glass, which is used for lighting fixtures, mobile phones, liquid crystal displays, and the like is known (for example, Patent Documents). 1). Recently, since the reflectance is high over the entire visible light region, a reflecting mirror having a silver film has been mainly studied. However, since silver is chemically unstable, there is a problem that it is easily changed in color by changing to silver oxide, silver sulfide, or the like due to oxygen, moisture, sulfurous acid gas, hydrogen sulfide, etc. in the air.

  In order to solve this problem, a reflecting mirror in which an oxide film such as aluminum oxide is formed on a silver film as a protective film is disclosed (Patent Document 2). However, since the reflecting mirror forms an oxide film such as aluminum oxide on the silver film by sputtering or the like, the film is formed in an oxidizing atmosphere, so that the surface of the silver film is oxidized and sufficient reflection is achieved. There is a problem that the rate is difficult to obtain. In addition, the protective film cannot sufficiently suppress the alteration of silver due to oxygen, moisture, sulfurous acid gas, hydrogen sulfide, etc. in the air, and the moisture resistance and sulfur resistance of the reflector cannot be said to be sufficient.

Further, a reflecting mirror is disclosed in which a film such as aluminum nitride or diamond-like carbon is laminated on a silver film as a protective film (Patent Document 3). Further, a reflecting mirror in which a silicon nitride film is formed on a silver film by a sputtering method as a protective film is disclosed (Patent Document 4). However, even with this protective film, the alteration of silver due to oxygen, moisture, sulfurous acid gas, hydrogen sulfide, etc. in the air cannot be sufficiently suppressed, and the moisture resistance and sulfur resistance of the reflector are not sufficient. I can't say that.
Japanese Utility Model Publication No. 5-73809 JP 2001-343510 A JP 2001-13309 A JP 2001-337210 A

  An object of the present invention is to provide a reflecting mirror that has a high reflectance in the visible light region and is excellent in moisture resistance and sulfur resistance.

The reflecting mirror of the present invention includes a base material, a silicon compound film selected from the group consisting of silicon nitride, silicon oxide, and silicon oxynitride, and silver provided between the base material and the silicon compound film. It has the silver film which consists of a silver alloy, and the hydrocarbon film formed by performing a plasma process on a silicon compound film, It is characterized by the above-mentioned.
The hydrocarbon film is preferably a film formed by a plasma CVD method.

The hydrocarbon film has a base material temperature of −20 to 150 ° C., a high frequency of 100 kHz to 100 MHz is applied to the raw material gas at a power density of 0.1 to 5 W / cm ² under a pressure of 0.1 to 1000 Pa, and the raw material gas. It is preferable that the film be formed into a plasma by depositing a reactant of the source gas on the silicon compound film.
The source gas is preferably at least one selected from the group consisting of methane gas, ethane gas, propane gas, acetylene gas and ethylene gas.

The reflecting mirror of the present invention preferably further has a base film made of an oxide provided between the base material and the silver film.
The oxide is preferably titanium oxide represented by TiO _x (1.5 ≦ x <2).
The film thickness of the silver film is preferably 60 to 300 nm, and the film thickness of the silicon compound film is preferably 2 to 20 nm.
The film thickness of the hydrocarbon film is preferably 0.5 to 20 nm.
The film thickness of the base film is preferably 1 to 50 nm.

  The reflecting mirror of the present invention has a high reflectance in the visible light region and is excellent in moisture resistance and sulfur resistance.

<Reflector>
FIG. 1 is a cross-sectional view showing an example of the reflecting mirror of the present invention. The reflecting mirror 10 includes a base material 11, a base film 12 provided on the base material 11, a silver film 13 provided on the base film 12, and a silicon compound film provided on the silver film 13. 14 and a hydrocarbon film 15 provided on the silicon compound film 14.

(Base material)
Examples of the material of the substrate 11 include glass; plastics such as polyethylene terephthalate, acrylic resin, and polycarbonate.
The shape of a base material should just be a shape calculated | required as a base material of various reflective mirrors, such as a plane, a diffusion surface, a concave surface, a convex surface, and a trapezoid.
As the base material 11, a plastic film is particularly preferable in that it can be reduced in weight.
When the thickness of the base material 11 is a planar shape, 30-500 micrometers is preferable.
When the base material 11 is a film, a plasma treatment or the like may be performed in order to improve the adhesion with the base film 12, the silver film 13, and the like.

(Undercoat)
The base film 12 is a film made of an oxide. By providing the base film 12, the adhesion between the base material 11 and the silver film 13 in contact with the base film 12 can be improved, and as a result, the moisture resistance of the reflecting mirror 10 can be further improved.
Examples of the oxide include titanium oxide, zinc oxide, tin oxide, indium oxide, aluminum oxide, chromium oxide, and niobium oxide. Of these, titanium oxide is preferable from the viewpoint of adhesion, and titanium oxide having oxygen deficiency represented by TiO _x (1.5 ≦ x <2) is particularly preferable.

The base film 12 may be a single layer or may be composed of a plurality of layers.
1-50 nm is preferable and, as for the film thickness of the base film 12, 3-15 nm is especially preferable. When the film thickness of the base film 12 is less than 1 nm, the effect of improving the adhesion between the base material 11 and the silver film 13 hardly appears. When the film thickness of the base film 12 exceeds 50 nm, the unevenness of the surface of the base film 12 becomes large, and the reflectivity may be lowered, or the internal stress may be increased, and the adhesion may be lowered. The film thickness is a physical film thickness, and the physical film thickness can be obtained by an ellipsometer, a stylus type step gauge or the like.

(Silver film)
The silver film 13 is a film made of silver or a silver alloy, and plays a role as a reflection film that reflects light. By using the silver film 13 as the reflection film, the reflectance in the visible light region of the reflector 10 can be increased, and the dependence of the reflectance on the incident angle can be reduced. The visible light region means a wavelength region of 400 to 700 nm. The incident angle means an angle with respect to a line perpendicular to the film surface.

As the silver alloy, an alloy composed of silver and one or more other metals selected from the group consisting of gold, palladium, tin, gallium, indium, copper, titanium, and bismuth improves the durability of the silver film 13. In addition, the reflectance is further improved, which is preferable. As the other metal, gold is particularly preferable from the viewpoint of high temperature humidity resistance and reflectance.
When the silver film 13 is a film made of a silver alloy, the silver is preferably 90 to 99.8 atomic% in the total (100 atomic%) of silver and other metals in the silver film 13. Moreover, 0.2-10 atomic% of other metals is preferable from a durable point.

  The film thickness of the silver film 13 is preferably 60 to 300 nm, particularly preferably 80 to 200 nm. When the film thickness of the silver film 13 is less than 60 nm, the reflectance in the visible light region may decrease. If the film thickness of the silver film 13 exceeds 300 nm, irregularities are likely to occur on the surface of the silver film 13, thereby causing light scattering, which may reduce the reflectance in the visible light region.

(Silicon compound film)
The silicon compound film 14 is a film made of one kind selected from the group consisting of silicon nitride, silicon oxide, and silicon oxynitride, and suppresses the alteration of the silver film 13 in contact with the film. As a result, the moisture resistance of the reflecting mirror 10 is improved. It is a film that improves sulfur resistance.
The silicon compound film 14 is preferably a silicon nitride film formed by a chemical vapor deposition method (hereinafter referred to as a CVD method). The silicon nitride film formed by the CVD method has advantages such as low film stress, good coverage to a complicated shape, and high gas barrier performance compared to the silicon nitride film formed by the sputtering method. As a result, the sulfur resistance of the reflecting mirror 10 is improved.

  2-20 nm is preferable and, as for the film thickness of the silicon compound film | membrane 14, 3-15 nm is especially preferable. If the thickness of the silicon compound film 14 is less than 2 nm, the moisture resistance and sulfur resistance of the reflecting mirror 10 may be insufficient. When the film thickness of the silicon compound film 14 exceeds 20 nm, the reflectance may decrease due to coloring (absorption) by the silicon compound film 14.

(Hydrocarbon film)
The hydrocarbon film 15 is a film made of hydrocarbon provided on the outermost surface of the reflecting mirror 10. By providing the hydrocarbon film 15, the moisture resistance and sulfur resistance of the reflecting mirror 10 can be further improved.
Although the reason for improving the sulfur resistance has not been elucidated in detail, it is considered as follows. That is, since the adsorption energy between the carbon atom in the hydrocarbon and the sulfur atom in the sulfur-containing molecule such as hydrogen sulfide is low, it is difficult for the sulfur-containing molecule to adhere to the surface of the hydrocarbon film 15 and the sulfur resistance is improved. It is thought that it is improving.

  Hydrocarbons are also called hydrogenated carbon, hard carbon, diamond-like carbon (DLC), i-carbon, and amorphous carbon, and conventionally known hydrocarbons can be appropriately used. The film made of hydrocarbon has excellent properties as a protective film, such as excellent surface smoothness, a small coefficient of friction on the surface, chemical inertness, and low wettability so that it is difficult to get dirty.

The hydrocarbon film 15 needs to be a transparent film in view of the reflectance of the reflecting mirror 10. Specifically, the extinction coefficient in the visible light region is preferably 0.1 or less, particularly preferably 0.08 or less, and most preferably 0.05 or less. The extinction coefficient means the imaginary part of the complex refractive index in the visible light region and can be measured by a spectroscopic ellipsometer.
The film thickness of the hydrocarbon film 15 is preferably 0.5 to 20 nm, and particularly preferably 1 to 5 nm. If the thickness of the hydrocarbon film 15 is less than 0.5 nm, the gas barrier property is lowered. If the thickness of the hydrocarbon film 15 exceeds 20 nm, the reflectance may be lowered.

(Manufacturing method of reflecting mirror)
The reflecting mirror 10 is obtained by sequentially forming each film on the substrate 11 by sputtering, CVD, plasma treatment, or the like.

The base film 12 is preferably formed by sputtering. The atmosphere is preferably a rare gas atmosphere such as argon that does not substantially contain an oxidizing gas. The oxidizing gas such as oxygen is preferably 18% by volume or less.
The target for the base film 12 is preferably an oxide target in that an oxide film can be formed in an atmosphere that does not substantially contain an oxidizing gas. Examples of the oxide target include a target including one or more selected from the group consisting of titanium oxide, zinc oxide, tin oxide, indium oxide, aluminum oxide, chromium oxide, and niobium oxide.
When the base film 12 is formed by the DC sputtering method, an oxygen deficient target is preferable because it can be formed at a high speed. Examples of the oxygen deficient target include those expressed as TiO _x (1.5 ≦ x <2.0).

The silver film 13 is preferably formed by sputtering using a target made of silver or a silver alloy in an argon gas atmosphere.
As a silver target, the target containing 95 mass% or more of silver is preferable. As the silver alloy target, a target containing 95 to 99.7% by mass of silver and 0.3 to 5.0% by mass of other metals is preferable.

The silicon compound film 14 is preferably formed by a CVD method. By forming the silicon compound film 14 by the CVD method, the sulfur resistance of the reflecting mirror 10 is improved.
The CVD method is a method in which a raw material gas is reacted by applying energy to the raw material gas by heat or light, or by plasmaizing at a high frequency to deposit a film of a reaction product.
Examples of the source gas include a mixed gas of silane gas and ammonia gas.

  The hydrocarbon film 15 is formed by performing plasma treatment on the silicon compound film 14. Plasma treatment refers to exposing a treatment target to an ionized gas generated by any one of corona discharge, arc discharge, and glow discharge. As the plasma treatment, plasma treatment by glow discharge is preferable in terms of thermal damage and distribution (uniformity). An example of the plasma treatment is a plasma CVD method.

The hydrocarbon film 15 is preferably formed by a plasma CVD method. Specifically, after the substrate temperature in the plasma CVD apparatus is set to −20 to 150 ° C., a source gas is introduced into the plasma CVD apparatus. A high frequency of 100 kHz to 100 MHz is applied to the raw material gas at a power density of 0.1 to 5 W / cm ² under a pressure of 0.1 to 1000 Pa, and the raw material gas is turned into plasma, and the reactant of the raw material gas is formed on the silicon compound film 14. To form a film.

When the substrate temperature is less than −20 ° C., the film can be formed only in the state of a low molecular weight monomer, and there is a problem in film strength and the like. When the substrate temperature exceeds 150 ° C., the adhesion of the film becomes weak.
When the pressure in the plasma CVD apparatus is less than 0.1 Pa, it is difficult to maintain discharge. When the pressure in the plasma CVD apparatus exceeds 1000 Pa, arc discharge occurs and film formation cannot be performed with good uniformity.
If the frequency of the high frequency is less than 100 kHz, a sufficient plasma density cannot be obtained, and the barrier performance of the resulting film becomes insufficient. When the frequency of the high frequency exceeds 100 MHz, the uniformity of the plasma is poor and the substrate generates heat.
When the power density is less than 0.1 W / cm ² , the plasma density is not increased, and when it exceeds 5 W / cm ² , a heat load is applied.

  Examples of the source gas include methane gas, ethane gas, propane gas, acetylene gas, and ethylene gas. These may be used alone or in combination of two or more.

  The reflector 10 preferably has a luminous reflectance according to JIS Z 8701 of 90% or more, more preferably 95% or more, and most preferably 97% or more. Thereby, the reflectance of the reflecting mirror 10 becomes high, and when used in an image apparatus such as a projection television or a liquid crystal display, an image can be projected without lowering the luminance.

[Example 1]
In the vacuum chamber, a flat polyethylene terephthalate film (thickness: 50 μm) with an acrylic hard coat was disposed as a substrate.
As targets, a TiO _x oxygen deficient target (trade name “TXO”, manufactured by Asahi Glass Ceramics Co., Ltd.), and a silver alloy target (gold content 1 mass%, silver content 99 mass%) added with gold, It installed so that it might oppose a base material. The inside of the vacuum chamber was evacuated to 2 × 10 ⁻⁵ Pa.

  200 sccm of argon gas is introduced into the vacuum chamber, 100 W of electric power is applied, and the substrate is irradiated with argon ions ionized from an ion beam source (LIS-150, manufactured by Advanced Energy) to dry-clean the substrate. went.

Subsequently, argon gas was introduced into the vacuum chamber as a sputtering gas. Using a TiO _x oxygen deficient target, pulse sputtering with a pressure of 0.15 Pa, a frequency of 100 kHz, a power density of 0.79 W / cm ² , and an inversion pulse width of 1 μsec was performed by a DC sputtering method, and titanium oxide was formed on the substrate. A film (underlying film) was formed to a thickness of 5 nm. The components of the titanium oxide film were equivalent to the target.

Next, after exhausting the residual gas, argon gas was introduced into the vacuum chamber as a sputtering gas. Using a silver alloy target to which 1% by mass of gold is added, pulse sputtering with a frequency of 100 kHz, a power density of 2.46 W / cm ² , and a reverse pulse width of 5 μs is performed by a DC sputtering method at a pressure of 0.15 Pa. A silver alloy film (silver film) containing gold was formed to a thickness of 150 nm on the titanium film. The composition of the silver alloy film was equivalent to that of the target.

Next, a silicon nitride film was formed on the silver alloy film using a plasma CVD apparatus (CC-200, manufactured by ULVAC). Silane gas (SiH ₄ ) and ammonia gas (NH ₃ ) were used as the source gas, and nitrogen gas was used as the carrier gas. Source gas and carrier gas are introduced at a flow rate ratio of NH ₃ / SiH ₄ of 50% by volume and (NH ₃ + SiH ₄ ) / total gas of 10% by volume, and at a pressure of 100 Pa, a high frequency of 27.12 MHz is supplied to the source gas. Was applied at 500 W to turn the source gas into plasma, and a silicon nitride film (silicon compound film) was formed to a thickness of 10 nm. The substrate temperature at this time was 80 degreeC.

Next, a hydrocarbon film was formed on the silicon nitride film using a plasma CVD apparatus (CC-200, manufactured by ULVAC). Methane gas was used as the source gas. A raw material gas was introduced, a high frequency of 27.12 MHz was applied to the raw material gas at a pressure of 100 Pa, and the raw material gas was turned into plasma to form a hydrocarbon film with a thickness of 4 nm. The substrate temperature at this time was 80 degreeC.
The following evaluation was performed about the obtained reflective mirror. The results are shown in Tables 1-3. Moreover, the photograph of the film surface side of the reflecting mirror after the hydrogen sulfide resistance test is shown in FIG.

(1) High temperature and humidity resistance test:
The reflector was cut into 50 mm × 100 mm and used for the sample. The sample was allowed to stand for 100 hours in an atmosphere at a temperature of 60 ° C. and a relative humidity of 90%, and the presence or absence of film peeling and corrosion after the standing was confirmed.
○: There was no peeling of the film, and no corrosion was detected.
X: Detachment and / or corrosion was detected on the film.

(2) High temperature test:
The reflector was cut into 50 mm × 100 mm and used for the sample. The sample was allowed to stand for 100 hours in an atmosphere at a temperature of 85 ° C. and a relative humidity of 30% or less, and the presence or absence of film peeling and corrosion after the standing was confirmed.
○: There was no peeling of the film, and no corrosion was detected.
X: Detachment and / or corrosion was detected on the film.

(3) Hydrogen sulfide resistance test:
The reflecting mirror was cut into 50 × 100 mm and used for the sample. 10 ppm of hydrogen sulfide was introduced, and the sample was allowed to stand for 100 hours in an atmosphere at a temperature of 50 ° C. and a relative humidity of 80%, and the visual reflectance after the storage, film peeling, and the presence or absence of corrosion (appearance) were confirmed.
The presence or absence (appearance) of film peeling and corrosion was evaluated according to the following criteria.
○: There was no peeling of the film, and no corrosion was detected.
X: Detachment and / or corrosion was detected on the film.

(4) Film surface reflectance:
The reflectance on the film surface side is measured using a color analyzer (TOPSCAN, manufactured by Tokyo Denshoku Co., Ltd.), and tristimulus chromaticity Y specified in JIS Z 8701 (1982) is obtained by calculation. It was. The measurement was performed by the SCI method in which measurement is performed by measuring both regular reflection light and diffused light. The luminous reflectance was measured immediately after film formation, after the high temperature and humidity resistance test, after the high temperature test, and after the hydrogen sulfide resistance test.

[Comparative Example 1]
A reflecting mirror was obtained in the same manner as in Example 1 except that the hydrocarbon film was not formed on the silicon nitride film.
The obtained reflecting mirror was evaluated in the same manner as in Example 1. The results are shown in Tables 1-3. Moreover, the photograph of the film surface side of the reflecting mirror after the hydrogen sulfide resistance test is shown in FIG.

  The reflecting mirror of the present invention is a reflective member for a light source such as a flat panel display, a projection television, a display such as a mobile phone, and more particularly an electronic device such as a mobile personal computer, a mobile phone, a PDA, a portable game device. It is useful as a reflection member for a light source of a display.

It is sectional drawing which shows an example of the reflective mirror of this invention. It is the photograph of the film surface side of the reflective mirror of Example 1 after a hydrogen sulfide resistance test. It is the photograph of the film surface side of the reflective mirror of the comparative example 1 after a hydrogen sulfide resistance test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reflective mirror 11 Base material 12 Base film 13 Silver film 14 Silicon compound film 15 Hydrocarbon film

Claims (9)

A substrate;
A silicon compound film made of one selected from the group consisting of silicon nitride, silicon oxide and silicon oxynitride;
A silver film made of silver or a silver alloy provided between the base material and the silicon compound film;
And a hydrocarbon film formed by performing plasma treatment on the silicon compound film.   The reflecting mirror according to claim 1, wherein the hydrocarbon film is a film formed by a plasma CVD method. The hydrocarbon film has a base material temperature of −20 to 150 ° C., a high frequency of 100 kHz to 100 MHz is applied to the raw material gas at a power density of 0.1 to 5 W / cm ² under a pressure of 0.1 to 1000 Pa, and the raw material gas The reflecting mirror according to claim 1, which is a film formed by converting plasma into a plasma and depositing a reactant of a source gas on the silicon compound film.   The reflecting mirror according to claim 3, wherein the source gas is at least one selected from the group consisting of methane gas, ethane gas, propane gas, acetylene gas, and ethylene gas.   The reflective mirror in any one of Claims 1-4 which further has the base film which consists of an oxide provided between the base material and the silver film. The reflecting mirror according to claim 5, wherein the oxide is titanium oxide represented by TiO _x (1.5 ≦ x <2). The film thickness of the silver film is 60 to 300 nm,
The reflective mirror in any one of Claims 1-6 whose film thickness of a silicon compound film | membrane is 2-20 nm.   The reflective mirror in any one of Claims 1-7 whose film thickness of a hydrocarbon film | membrane is 0.5-20 nm. The reflective mirror of Claim 5 whose film thickness of a base film is 1-50 nm.

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